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[
"When an Iconic satellite (Hubble, ISS) is at the end of its life cycle, could we launch it passengerless into a stable orbit such as those of comets?"
] |
[
false
] | null |
[
"If we could \"ignore cost to a degree\" ? No. The cost would be really too high.",
"If we could totally \"ignore cost\" ? Yes. You could accelerate the object so it's orbit becomes really elongated, but it still wouldn't have the orbit of a comet. If you want your satellite to have a comet-like orbit, you'll have to make it orbit the Sun then accelerate him even more.",
" With infinite money, yes.",
"Fun fact : Hubble is already passengerless."
] |
[
"If you would burn toward prograde at the periapsis you could fairly easily put the hubble in an eccentric orbit. That would let it stay up for quite a bit longer, but eventually it would fall back to earth because the periapse would still be at its original altitude. The ISS is very massive and would require many boosting stages to get it to an eccentricity that would extend its orbit significantly. "
] |
[
"Well I figured that with a very high apoapsis, it would take some time for the atmosphere to decelerate the satellite enough to make it burn. Plus, if we have enough fuel to put a sat on this kind of orbit \"for fun\", we probably have enough to circularize the orbit."
] |
[
"Is it more fuel efficient for a car to accelerate more before going up a hill or maintain a constant speed before and during the climb?"
] |
[
false
] |
I believe constraints would be required. So, let's say I restrict my speeds to be in a certain range, for example: between 20mph and 40mph.
|
[
"I have hauled logs off highway for many winters where my average gross weight per load was around 78,000 kgs (170,000lbs). Since fuel was my biggest expense I have spent many hours comparing my fuel consumption to varying driving habits. Over the years I have noticed that by following the following rules I can save up to 150 liters of fuel ($200) in a 12 hour day.",
"If it is a small hill with a gentle rise then the best way to conserve fuel is to approach the hill at normal driving speed and slowly easing back on the fuel pedal to coast up the hill, then let gravity help me get back to my cruising speed.",
"If it is a short but steep hill I will increase my speed to \"run the hill\" then ease off the throttle and let momentum carry me over the hill.",
"When I have to climb long and steep hill I will \"run it\" at the bottom, then find a gear where I can keep my engine running at the rpm where it makes its peak torque at full throttle - between 1,200 and 1,500 rpm.",
"When driving along a level road I try to keep in a gear where I am running it its \"sweet spot\" which is a little bit higher than running at peak torque but not much more than 3/4 throttle.",
"I have tried to keep my engine rpm in its peak torque range of 1,350 - 1,500 rpm for a few trips and found out that it gave me the worst fuel economy ever. The best engine speed I found for mileage was in a range between 1,550 and 1,650 rpm. I have a 550 cat in my truck. Here is a link to the pubiished torque curves for this engine. ",
"http://pdf.cat.com/cda/files/2208232/7/leht8893-00.pdf",
" ",
"One gallon of gas has enough energy to create 10 horsepower in an internal combustion engine, period. How this energy is utilized determines the vehicles efficiency.",
"(edit: gasoline can theoretically produce more power than 10 hp per gallon but the thermal and frictional losses restrict the amount of power available in today' ice's to 0.6 pounds per horsepower.)",
"If you drive at wide open throttle at an rpm that is below the maximum torque then the engine will be working harder then it is designed to. This will produce excess heat causing your engines temperature to rise, and your fan to kick in... both of which will consume more fuel.",
"If you are driving at an engine speed that is above your torque curve, then your engine is using more fuel than it needs to to maintain your speed. This will also increase your fuel consumption as well.",
"edit: I have a jet boat to go fishing or play in the rivers with. I installed a vacuum gauge in it to help me get better fuel economy. I tuned the boat to get the highest vacuum reading at the fastest comfortable cruising speed as determined by my gps. I managed to save a little under a gallon per hour at a cruise speed of 24 mph by doing so. Now I only use 6 gallons per hour at 24 mph where before I used 7 gph at 26 mph."
] |
[
"This is a great practical answer, but:",
"One gallon of gas has enough energy to create 10 horsepower in an internal combustion engine.",
"No: horsepower is not a unit of energy. One gallon of gas standardly contains about 114000BTU - that's 28,743 KCal, or 120M Joules, or 33KWh",
"Diesel engines can achieve ~50% efficiency (gas engines closer to 30%), so there's at best ~16KWh of work (=\"energy\") that can be had from a gallon of gas."
] |
[
"Actually, it gets more complicated than that, because it may be still more efficient to let yourself slow down somewhat as you climb the incline, because the force being used required of your engine to maintain a given speed on an incline is not the same as the force required of that same engine on a level surface, or while descending.",
"As such, since you are trying to maintain a minimal Sum of Force, it is almost certainly more efficient to accelerate on the level (or better, on a decline), and attempt to merely mitigate the loss of speed of speed on the incline, as the force required to maintain that speed on a slope is a function of rolling resistance, air resistance, ",
" working against gravity, rather than just the first two."
] |
[
"If the difference between the cells in our body is not the DNA that they contain but rather their genetic expression of that DNA, do we have a way to measure or examine that expression?"
] |
[
false
] | null |
[
"Yes there are many ways, measuring gene expression is done all the time in the lab and is a fundamental part of just about any genetics or molecular biology research. It's also used in medical diagnostics, for example, ",
"tumors are sometimes screened to see what genes they are expressing",
" as this can help determine the best treatment.",
"When a gene is expressed the DNA is made into RNA then the RNA gets made into protein so you can measure gene expression at either the RNA or protein level.",
"Northern blot",
": this is an old technique now usually only done in a few specialized circumstances, you can measure a few genes at a time and it takes a day or two, this can also tell you how big a gene is (technically it tells you how big the RNA is not the DNA, the RNA will be smaller than the DNA because some parts of the DNA get cut out when it's made into RNA).",
"Polymerase Chain Reaction (PCR)",
": This is an incredibly important technique not only used for measuring gene expression but is an essential part of many genetics techniques. Basically it's used to amplify (make more copies of) DNA. This is extremely important because you can't do much with the small amount of DNA you get from some cells or tissue but if you can make many copies you can do a lot more with it. The Nobel Prize in 1993 was given to the person who invented this technique. PCR can measure a few genes at a time and it takes a few hours.",
"Real-time PCR",
": A newer version of PCR that is more accurate.",
"RNA-sequencing",
": A new technology which has become popular just in the last 5 years or so, you can measure ",
", it is fairly expensive ($500-$1000 per experiment) and takes a few weeks to get results.",
"In situ hybridization",
": This technique is used to tell you where a gene is expressed more than how much it's expressed. You take a piece of tissue (brain, heart, lung, whatever) and chemically treat it so that the gene you're interested in will turn purple if/where it's being expressed. It's usually used for RNA but can be used for protein and it takes a few days.",
"Fluoresence in situ hybridization",
": Like in situ hybridization but instead of the gene turning purple when it's expressed it fluoresces one of several colors. An advantage is that you can look at more than one gene at a time (each will be a different color). This is usually used to measure expression at the protein level but can also be used for RNA.",
"Western blot",
": This is like a northern blot in that you can measure a few genes at a time, you can tell how big the gene is (technically it will tell you how big the protein is), and it takes a day or two, but unlike a northern blot it measures expression at the protein level instead of at the RNA level.",
"Proteomics",
": this is a general category of techniques to measure the expression of many proteins at once."
] |
[
"Now maybe you want to now the principle behind the majority of these methods ?",
" ",
"Gene expression",
" is done in 2 steps. First, the ",
" (transcription). Then, ",
" (translation); which are the molecules that actually do stuff in the cell. Even for the most expressed genes, there's only a few copies of the gene in the DNA, most of the time. The real difference is the amount of RNA and proteins the cell will produce from a given gene. So how do you measure the amount of a certain RNA in the cell ?",
"RNA sequences (like DNA) are subject to what we call ",
". This means that a RNA sequence has a tendency to bind with its opposite sequence. For exemple, ",
" will bind strongly with ",
" (G is complementary to C, T to A and A to T). So if you know which sequence of RNA you are looking for, you can craft the complementary sequence. Then you add some type of marker to it (usually a radioactive isotope, a metallic particle or a fluorescent protein). This type of molecule is called a ",
". \nSo if you want to know if the sequence ",
" is strongly expressed, you can put your probe, ",
" (complementary sequence with a metallic particle) in the cell. After a bit of time, you put your cell under an electronic microscope. The metallic particle appear as a black spot, so if the cell has a lot of black spots, you know the gene is strongly expressed.",
"If you put your probe in the cell to see where it sticks, you're doing \"in situ hybridization\". An electrophoresis with the RNA and your probes is the Western or Northern blot... The majority of the techniques used in molecular biology uses some kind of hybridization.",
"The choice of the technique depends on the amount of money you have and what you want to know. "
] |
[
"Good summary, but I would add some techniques to the list:",
"Gene Chips",
" allow you to convert the abundance of specific RNA molecules into red/green fluorescent intensities. ",
"RNA sequencing",
" is mentioned above, and allows you to measure a large subset of the RNA produced by sequencing millions of individual molecules. This is made possible by the rapid advances in sequencing technology over the last decade. I added this to the list to point out that variations on this theme can focus the sequencing to just mRNA, or ",
"just actively transcribed RNA",
", or just the ",
"RNA from a single cell",
". "
] |
[
"Do organisms with shorter lifespans and greater reproductive rates evolve \"faster\" than others? Does this have anything to do with why amphibians show mutations from environmental contamination faster than we do?"
] |
[
false
] | null |
[
"Yes. The faster the reproductive cycle the faster evolution occurs. Every time a species genetic code is duplicated there are mutations which cause evolution. Whether it is a mammal, insect or bacteria the faster the genetic code can be passed on the faster evolution can occur.",
"A great example of this is getting a flu-shot each year. This is because each year the common flu has evolved and grown immune to the previous years drugs.",
"As for amphibians being more susceptible to contamination it has more to do with the fact that they are aquatic animals with very permeable skin and eggs that absorb many toxins."
] |
[
"http://mblogs.discovermagazine.com/loom/2012/03/14/fifty-seven-years-of-darkness/",
"Evidence"
] |
[
"A strange result is that over geologic time, rates of evolution for different groups are generally similar.\nThis is rates measured in units like ",
"darwins or haldanes",
".",
"Rates in darwins and haldanes are surprisingly consistent for various groups (this has mostly been studied in mammals, but other vertebrates as well).",
"This is not entirely understood, but generally considered to be because there is a pay off between population size, individual size, and generation time.",
"Large population size = slow rates.",
"Large individual size = small population.",
"Large generation time = small population. ",
"What is your source on amphibians showing mutations quickly? ",
"Environmental contamination affects amphibians more quickly not because some evolutionary reason, but because they simply have a smaller range of environmental tolerance!"
] |
[
"Practical to reduce A/C load on engine by changing pulley sizes?"
] |
[
false
] |
I have a old Opel Astra 1400 '96 with an after market A/C. It puts so much load on the (small) engine that I basically cannot use it, unless I'm going downhill. I'm considering changing the engine pulley on the A/C drive belt to a 50% larger pulley size, to reduce the drag on the engine. I know this would be at the expense of less effective cooling, but it's either that or nothing. Will this reduce the effectiveness to much? Or have other practical downsides?
|
[
"Sounds like a reasonable modification to me. I would check the high and low side pressure after the mod to see if it's still reasonable. if the pressure is too low, you may have to modify the orifice tube (if it has one) to get the pressure differential back up due to the decreased flow."
] |
[
"also, just an afterthought. does it happen to run ok when your engine is above idle but bog down during idle? normally a/c systems are supposed to open up the IAC to compensate for the increased load of the compressor. if it's an aftermarket system this may have been left out."
] |
[
"There should be a wide open throttle switch which cuts the compressor off during WOT. Newer cars use the throttle position sensor position to do it, but you could mount a microswitch if none exists. "
] |
[
"What would happen if you took a chunk of bismuth into a room with an active MRI machine? Would it fly out of your hand and be shoved against the wall?"
] |
[
false
] | null |
[
"That's a great answer, but to the wrong question. He's asking what happens to bismuth in a very strong magnetic field...."
] |
[
"All MRI are always active. The only times that an MRI's magnet will turn off is because something has gone wrong and it has enter a quench on its own, it needs to be moved and the magnet is progressively weakened or turned off, or it is done in order to save someone's life. Under normal operating procedure the magnet is on from the moment that it is powered up, until the MRI is decommissioned.",
"The magnetic field generated by MRI scanners is quite strong, so it will pull anything magnetic towards the centre of the bore. ",
"YouTube has a lot of safety videos about what happens when metal enters the magnetic field",
".",
"YouTube also has a bunch of videos of what happens when a magnet is quenched",
". The white smoke is the liquid helium that was used to supercool the MRI boiling off. Those are all controlled and planned quenches, wouldn't want to be there for an uncontrolled one (helium could do a great job of displacing oxygen if it went to the wrong place).",
"Edit: One more video. Here is a ",
"demonstration of what happens when you put aluminium into an MRI",
". While the aluminium is not attracted by the magnetic field, it is a really neat example of ",
"Lenz's law",
"."
] |
[
"I just had an MRI yesterday, and the noises involved seemed to indicate it was not always active.",
"These are the gradient coils, which are switched on and off to create images in the X, Y and Z directions.",
"The static field, B0, is never turned off. You may have noticed the very large door that keeps the scanner separated from everything else. There may have also been black-and-yellow tape on the floor to demarcate the gaussian field. Nothing metallic should go beyond this tape, especially pacemakers and small, soon to be projectile, objects.",
"I don't know about bismuth, but my guess would be that it behaves very similarly to ",
"other diamagnetic objects",
"."
] |
[
"Is it possible for something like Olympus Mons to form in Earth-like conditions?"
] |
[
false
] |
I was thinking about this and I am quite curious if something like Olympus Mons could form here. (Not really an exact replica, but somewhat similar with some changes.) The characteristics I am thinking about is pretty much a stationary plate, a powerful hotspot (similar to the Hawaiian hotspot) and a stable crust (a thick craton) for such a volcano (more like a really high plateau) to stand on with minimal sinkage. The conditions met would not really exist on Earth at some time or another, but the closest thing to that, in my opinion, is the Tibesti mountains in Africa, where a hotspot underneath the Saharan Meta-craton produced a few volcanoes. Could it exist in some form and, if so, what process would lead to that and how would it form?
|
[
", not without fundamental changes to the tectonic regime, lithospheric structure, and the surface conditions (i.e., atmosphere, hydrosphere, erosional mechanims, etc.) to the point where Earth really wouldn't be much at all like Earth.",
"To dive in more, ",
" You hit on some of the big ones, but it requires a few extra things (and modifications of things that you highlighted), specifically:",
"Larson, 1991",
"Now, ",
"this figure",
"Iaffaldano & DeMets, 2016",
"LLSVPs",
"Torsvik, 2019",
"Isherwood et al., 2013",
"Johnston & Thorkelson, 2000",
"Jellinek & Manga, 2004",
"Steinberger, 2000",
"Stock, 2003",
"Doubrovine et al., 2012",
"Watts, 1992",
"continental cratons",
"Burov & Diament, 1995",
"Burov & Watts, 2006",
"FAQs",
"Egholm et al., 2009",
"Foster et al., 2008",
"Thomson et al., 2010",
"Forte et al., 2022",
"Whipple & Tucker, 1999",
"Whipple et al., 1999",
"Ultimately, when you evaluate all the criteria together, you find that you would need an incredible set of coincidences (i.e., a craton on a plate over the edge of an LLSVP where a long-lived plume existed) and very unlikely conditions (i.e., that this plate would have to remain fixed in an absolute reference frame for ~ 1 billion years) to kind of set up the possibility but then, considering the range of erosional processes on Earth, even if all of those were satisfied, you still wouldn't really be able to build something like Olympus Mons."
] |
[
"It would still have to form on a craton on a plate that remained fixed in an absolute reference frame for the time period and you're still running up against all the myriad of surface processes that will effectively limit the height/mass of the edifice. I.e., virtually all of the criteria are unlikely to be satisfied, hypothetically making one or two more likely to be satisfied doesn't really help this be any more likely."
] |
[
"The big problem is CrustalTrudger's point 4. If you put a huge weight on the lithosphere it bends downwards, with the underlying asthenosphere being pushed to the side. The oceanic lithosphere under the Hawaiian islands is bent down by about 3 km, making the mountains 3 km lower than they would otherwise be.",
"https://www.slideserve.com/huela/lithospheric-flexure-at-the-hawaiian-islands-and-its-implications-for-mantle-rheology",
"Mars has thicker stiffer lithosphere, which if I remember rightly is a direct result of its lower gravity."
] |
[
"Why do we use water in steam based energy production instead of alcohol?"
] |
[
false
] |
[deleted]
|
[
"Never underestimate the power of \"because it's cheap\".",
"Plus, water has a really high thermal capacity, which means that in a typical cycle a LOT of energy can be moved around with relatively little of it. Typically power cycles are limited by the temperature anyway (can only get so hot in your turbine before the blades melt) so you want to make as much use of that temperature range as you can."
] |
[
"1)Alcohol is flammable. A leaky pipe or fitting could cause an explosion. ",
"2)At high temperatures alcohol can pyrolize and convert to a range of other compounds such as acetylaldehyde, methanol, carbon monoxide, ethane, hydrogen, benzene, and carbon char or soot.",
"You don't want your boiler pipes to clog up with soot. That's a good way to cause a boiler failure, possibly catastrophic."
] |
[
"Mercury has lower specific heat by weight, but better specific heat by volume and a higher boiling point. There was an era early in the history of electricity production when mercury turbines were favored.",
"Ammonia has a lower boiling point than water which is useful if your heat source isn't very hot. It is also one of the few substances with a better per-mass specific heat than water. Ammonia turbines see some use in geothermal and energy recovery."
] |
[
"If the Moon was created by an asteroid hitting the Earth, why didn't Earth get knocked out of its orbit around the Sun?"
] |
[
false
] |
[deleted]
|
[
"(Very) roughly, the earth's mass is 6E24 kg and the moon's is 7E22 kg, so roughly a hundred times more massive. To continue with the truck analogy, if it's a 3-ton pickup truck, it's like throwing a 60 pound rock at it. Yes, that's a big rock, but it won't do anything noticeable to deviate the path of the truck."
] |
[
"Because the earth is a whole lot heavier than the moon. Even an asteroid large enough to crash and knock out a moon-sized piece of the Earth would barely change the orbital speed of the Earth. Think of it like standing on the highway and throwing a rock as hard as you can at an oncoming semi-truck. Then you wonder why the truck didn't slow down. Sure, you probably made a dent in the metal wherever you hit it, and it slowed down ",
", but not nearly enough to send it hurdling into the sun (ok, the analogy falls apart there). Also, because of the mathematics of orbital mechanics, orbits can change considerably and still remain stable, so even if something so large were to hit us that our momentum changed by a considerable amount, the Earth wouldn't get \"knocked out\" of its orbit"
] |
[
"Riiight, I was thinking volume instead of mass. Thank you both for clearing it up for me!"
] |
[
"What can be heard in a heartbeat?"
] |
[
false
] |
I'm trying to model the sound of a human heartbeat. I'm surprised at how little hard information I've been able to dig up on what is in the sound of a normal heartbeat. I know a resting rate is around 60-80bpm, a normal systolic/diastolic ratio is 1.5, with 1.56 indicating high blood pressure -presumably lower for low blood pressure? how low? - and does the ratio increase with rate?. I was surprised to learn that there's such a thing as a too regular heart beat, so theres an optimal level of variance - but what is that level? - and what kind of variance? - gaussian? bimodal? ; Then there's all the other sounds. I can find plenty of information on pathological states, but that's not what I want. In recordings of normal heartbeats I can pick out the "S3" and "atrial" sounds - but what is the normal range of timings and amplitudes for them? (beyond just "kentucky" and "tennesee") ; Looking at a spectrum of a normal heartbeat I found what look like about 7 more-or-less regular small peaks. Could they be just artefacts of the recording, or do they have names? - thanks [EDIT] - thanks to all who replied. is a handy animation that links a lot of heart stuff together.
|
[
"Video describing an EKG--needed for fundamentals and if you're anything like me, a visual cue for this is absolutely necessary",
"This is what you're looking for in terms of time frames. Everything is in milliseconds so you'll have to convert according to your needs in order to maintain the proper ratios. EKGs are based on electrical impulses sent out by the heart.",
"Image of EKG vs Cardiac cycle--this will help you see how the EKG measures cardiac activity in terms of systole and diastole.",
" Another image",
"You really have to watch youtube videos to understand the cardiac cycle. Reading it doesn't help if you can't picture the heart(as with all things in medicine). ",
"Don't worry about all of the other beats, just use the basic EKG. Most of the time, these are variabilities and happen as a result of normal physiology, premature beats, and minor variations in heart structure. Remember that the heart must have a simultaneous but guided contraction throughout the entire muscle which requires each cell to communicate with each other via gap junctions--some screw ups are ok as the heart compensates by following the SA/AV node over its own electrical depolarization. The heart continues to beat even without the SA/AV node as a fail safe, but the SA then AV node take control respectively. Also, you get artifacts from patients moving around, misplaced electrodes, varying body physiology, etc. Use the basic EKG you always see and the timings listed in the wiki--these are what we use to determine pathologies. ",
"s3: Are usually pathological EXCEPT in pregnant women and tall skinny people, can also be heard in skinny athletic people. usually you won't hear this. \ns4: ALWAYS pathological\ns1 and s2: Normal heart sounds-- mitral/triscuspid valve immediately after its closure(sound is the blood being abruptly stopped/backing against the valve leaflets)and s2 is the closure of the aortic/pulmonic valve. s2 can be exaggerated by a person breathing in as it causes negative thoracic pressure, \"forces\" more blood into the heart, and delays closure of the pulmonic valve--the s2 sound you'll hear is the time delay between the aortic and pulmonic valve closure as normally this happens at the same time. s1 and s2 are always present and considered normal. ",
"Resting heart rate: 60-100. Less than 60=bradycardia; more than 100=tachycardia. Much lower for athletes but this is considered normal for them(basketball players and marathon runners can have a resting herat rate in the 30's and 40's and have no adverse effects--meanwhile we would be passed out on the floor)",
"For blood pressure, unless you're a cardiologist, you're going to be just checking the pressures and determining the levels based on JNC7 criteria ",
". A cardiologist would use more of the ratios and proportions as well as ejection fractions and echo/doppler studies(see blood flow and pressure changes), but we would call them in for cardiac failure and when patient have systemic effects of hypertension and CHF like edema or abnormal labs. The ratios are nice ,but what if someone has high systolic and low diastolic? it messes with the criteria so we tend to diagnose based on the blood pressures measured at 3 different instances. Again, i'm sure some cardiologists have more advanced methods but I doubt that is something at your level plus they have a much broader knowledge base and can apply the ratios when appropriate--books apply 50% of the time in real medicine lol. ",
"Pressure and Heart rate are somewhat inversely related. Cardiac output=Stroke volume x Heart rate. Pressures tend to determine stroke volume(if more blood returns to heart, probably have a higher pressure, and thus each contraction yields more blood, but not always the case) and heart rate is determined by all sorts of factors--whole point being cardiac output needs to remain relatively stable since organs require a certain pressure to overcome the vascular resistance. Thus, if heart rate goes up, pressure usually goes down a bit, and vice versa(Exception exercise). ",
"I've never heard of a heart that is too regular, but I can only assume they meant that a \"too regular heart won't respond properly to the constantly changing physiological properties of the body\"--ie won't increase or decrease rate accordingly. Source for this? "
] |
[
"Oh, I see. Here's a ",
"paper from 2006 that says",
":",
"There are currently no widely available large scale databases for development or evaluation purposes; the Johns Hopkins Cardiac Auscultation Recording Database is an excellent resource for research purposes, although it contains predominantly pediatric subjects, but there is no publicly available resource similar to those which are available for evaluation and comparison of ECG algorithms. ",
"Good luck!"
] |
[
"Thank you! - lots of good information there, and I think I have plenty to go on now.",
"This is just for an art project - I'm making stochastic generative sounds one of which is a heartbeat, but coming from a science background I want to make it accurate enough that a doctor could hear it and say - yep, that sounds like a healthy human. ",
"The \"too regular\" thing was from skimming through articles on ",
"heart rate variability",
"and finding things like \"Reduced HRV has been shown to be a predictor of mortality after myocardial infarction\". I'm not sure whether that means that the variance in duration of each beat vs the previous beat (1st order stats) is reduced, or that the overall range is limited to always-fast or always-slow. I also found what seemed to be a lot of woo and snake oil around heart rate variability (I guess you get that in anything medical), but ",
"this",
" page was surprisingly useful to me."
] |
[
"Is it possible to form metallic bonds between Uranium and Sodium?"
] |
[
false
] |
I was having a discussion about inner transition metals with a friend of mine, our class won't be covering them much if at all, so naturally we want to know more about them. We found that metals can bond with other metals through metallic bonding. So we are curious. Can a metal with a low melting point such as sodium bond with one with a melting point nearly 5x higher such as Uranium? What would happen if you attempted to bond Sodium and Uranium?
|
[
"Yes, there is nothing preventing alloy formation between low and high melting metals. You can even make alloys with mercury, which we call amalgams. There is apparently documented evidence that a sodium-uranium alloy exists, though I can't find any information on its properties. It's possible that the information is classified. One next generation nuclear reactor design is the molten sodium reactor, so it would be a great surprise if the reaction of sodium and uranium hadn't been studied in detail.",
"National lab link"
] |
[
"The properties of elemental sodium are nothing like those of ionic sodium, so there is little basis for comparison there. Sodium cooled reactors, just like most modern generation systems, are better at handling catastrophic failure than previous rector designs. For example, the Fukushima incident likely wouldn't have happened with a modern rector because when things go wrong, they simply shut down and the coolant solidifies instead of leaking out. They are also capable of running unattended for much longer."
] |
[
"Kind of, there really is no draining out of water in any kind of water reactor unless something has gone very wrong.. The issue is that if the pumps stop working, the water gets superheated and can rupture containment.",
"There is no \"solution\" in a sodium reactor. The coolant is literally molten sodium metal. "
] |
[
"Is thorium a viable option for supplying energy in America?"
] |
[
false
] |
I recently saw about thorium power, and it seems to suggest that thorium, if given enough support by the US government, could solve all our energy problems (I'll believe it when I see it). Physics/chemistry/energy experts, is thorium as good as this documentary suggests, or does this documentary contain some BS?
|
[
"http://www.reddit.com/r/askscience/comments/psu63/whats_the_truth_about_thorium_reactors_and_why/",
"http://www.reddit.com/r/askscience/comments/mz8pr/what_are_the_downsides_to_a_molten_salt_thorium/",
"http://www.reddit.com/r/askscience/comments/lmnep/ive_heard_all_about_the_positives_of_thorium/",
"http://www.reddit.com/r/askscience/comments/j8puj/i_stumbled_upon_articles_on_using_thorium_as_an/"
] |
[
"To summarize the content from those links:",
"I suppose that these arguments are valid, but they don't seem particularly strong to me. (In fact, I would say that any armchair scientist/journalist could come up with a similar list of criticisms with only a minimal amount of research.)",
"For example, the first item on that list has no uniqueness; you could say the same thing about any new technology and argue against it just by virtue of it `being new'. That type of reasoning is counterproductive and adds nothing to the discussion. (Though these are popular/non-scientific news sources, not scholarly writing).",
"The second issue is real, and would require some serious consideration. However, on the face of it, there isn't really anything insurmountable about it. We would `just' have to adopt the right regulatory and environmental policies to safely contain any waste products. Getting this type of political action implemented is nontrivial, but there is nothing scientifically impossible about it."
] |
[
"The Guardian article (from The Ecologist) is very misleading. Here is debunking:\n",
"http://energyfromthorium.com/rees-article-rebuttal/",
"IEER \"factsheet\" is also very misleading and full of inaccuracies. Debunked here:\n",
"http://energyfromthorium.com/ieer-rebuttal/"
] |
[
"Could Facial Recognition software work without a database?"
] |
[
false
] | null |
[
"You seem to be asking two different questions. The answer to your main question is yes -- that's what your camera / phone do... (for facial detection that is)"
] |
[
"I don't understand what you're trying to ask... Can you rephrase?"
] |
[
"I don't understand what you're trying to ask... Can you rephrase?"
] |
[
"Harmonics discussion: am I severely mistaken?"
] |
[
false
] |
Really sorry if this is the wrong place to post this. I was commenting on a post explaining what pythagorean tuning was, but the author of the music in the post insists that lowering the reference pitch by a few Hz affects the scale. Harmonics are just a ratio, correct? So lowering the reference pitch by a few Hz should lower the whole thing relative to the reference, and the ratios between the harmonics/notes should be the same, right? Am I mistaken, or is the author of this music mistaken? He or she keeps claiming they are an engineer and thus have a better understanding of harmonics than me, but then I find that this reddit user actually reposted our entire conversation to website, which didn't give me much faith in his scientific knowledge. However, I'm not one to commit an fallacy, so I would very much like to know if it is my understanding that is flawed, and if someone could correct me if it is.
|
[
"Though the harmonics of a fundamental are always going to be integer multiples in frequency, you can freely and arbitrarily select which fundamental frequencies you want to construct music out of. There is a widely used standard for what the fundamental frequencies should be, but it seemed like the gist of the author's post was not merely shifting the whole scale by a few Hz, but actually selecting a differently spaced set of frequencies to call notes.",
"I really can't say whether a slight alteration to the note spacing would substantially affect the perceived sound. Sound perception is kind of weird and very much not a sum-of-parts kind of thing. So long as there are some harmonics present, you can entirely remove the fundamental frequency of a sound with next to no effect on the perceived noise. If there are multiple tones, whether they are perceived as a single tone or as two distinct tones depends on both the relative frequencies of the tones and the levels of the harmonics of each."
] |
[
"Having read the conversation, I'm pretty sure the author's (wilfully or otherwise) misunderstanding what you say as commenting on whether or not Pythagorean tuning is different from equal temperament, which it obviously is.",
"You can change the reference frequency at will with no mathematical effects on the harmonics. However, for a real string instrument, behaviour wanders somewhat from the mathematical model, because the model makes assumptions about the stiffness of the string and the amplitude of displacement. Altering the tension in order to tune to a different reference frequency will affect this slightly, but I can't see any evidence that this would be a significant effect for a change of a percent or two to the reference frequency.",
"There will be similar nonlinearities for wind instruments etc as well. I'm not especially familiar with the mechanics offhand, but I'd be quite surprised if the effect was significant for the aforementioned small change.",
"There's been a remarkable amount of disagreement over the years over what should actually be used as the reference frequency. See the Wikipedia article on ",
"concert pitch",
"."
] |
[
"Yes, that's what pythagorean tuning is (differently spaced notes) - I fully appreciated this part. I was saying to the author that the fundamental frequency (432Hz) is arbitrary, and simply shifts the rest of the scale accordingly. "
] |
[
"Lets say we have a gear. If it's spinning at a high RPM, what direction do the particles want to travel?"
] |
[
false
] |
[deleted]
|
[
"If you imagine that all of the particles in the gear suddenly became \"unstuck\" from one another, the particles would move continue moving in the direction they were moving just before they became free to fly about (they would move along with the arrows seen in ",
"this picture",
"). Particles close to the center will get flung out at a lower velocity than those near the outside edge of the gear since the points on the outside have to travel further in one rotation than points near the middle."
] |
[
"Read up on ",
"centripetal force",
"."
] |
[
"This, not directly out from center."
] |
[
"During transformation, in genetic cloning using bacteria plasmids as vectors, do bacteria take in the new plasmid while their plasmid exits?"
] |
[
false
] |
The bacteria used in cloning already have plasmids from my understanding. And when we insert a genetically altered plasmid, say for insulin production, and we instigate a transformation reaction the bacteria takes in the new plasmid. What happens to their old, original plasmid? It would be odd if they had two distinct plasmids, or at least I would guess it would be inefficient at producing insulin(in this case)
|
[
"Why do you use wild type e.coli? I thought labs tended to just use mutants "
] |
[
"Why do you use wild type e.coli? I thought labs tended to just use mutants "
] |
[
"Yeah, we use strains that are 'competent,' that is, they are already very good at taking up plasmids (under the right conditions). Specifically, a commonly used strain (dh5 alpha) was modified at the genetic level; genes encoding endonucleases (that chew up exogenous genetic material) and recA (involved in genetic recombination) have been deleted.",
"Also, there is a difference between the bacterial chromosomal dna, which encodes most of the metabolic processes for the bacterium, and the plasmid dna that can have an additional function."
] |
[
"Does adiabatic warming occur when air descends in the Earth's polar cells?"
] |
[
false
] |
If adiabatic warming occurs when air in a Hadley cell descends, would it not also occur when air descends in a polar cell? If not, why?
|
[
"Sure! Sinking air warms by compression, so air sinking at the poles is warmer at the surface then where it began in the upper troposphere. This also causes a drop in relative humdity and produces clear skies. That is a big reason why both the north and south poles have arid climates."
] |
[
"I see! So said air must be ",
" cold just before descending. Thank you!"
] |
[
"The adiabatic warming is the reversal of the adiabatic cooling that happens when the air first rises net gain if you look at it over the whole cycle.",
"Now if you are loosing moisture then you get warmer air that is the effect that produces your Föhns and similar hot winds."
] |
[
"If you think you've been exposed to a virus, would changing you living habits (e.g. fasting, reducing all sugar intake to almost none, or putting a bunch of secondary molecules like berberry into you system) do anything to inhibit viral reproduction or spread?"
] |
[
false
] | null |
[
"You know what you call traditional medicine that has shown to be effective in scientific studies?",
"Medicine. Traditional medicine is what is left over.",
"So traditional medicines are not the kind of medicines you are going to get scientists to give you a scientific opinion about in a subreddit called AskScience.",
"Ask for how burberry is \"thought\" to work...well, other traditional medicines that are \"thought\" to work include deadly poisons like arsenic, mercury, and cadmium. Scientists have a higher standard than \"thought\" to work...that's why they do science to find out for sure."
] |
[
"Cutting your immune system off from what it needs to try and fight off anything is a bad idea."
] |
[
"No. Viruses do not metabolize, they hijack existing cells, and you have plenty of those. So you are not going to \"starve\" the virus...if anything, fasting or changing sugar intake would probably just depress your immune system and make things worse.",
"I don't know anything about burberry, except it is sold as an herbal supplement. That means its claims have not been demonstrated by science, there is very little control on how it is produced an what sort of a dose it contains, and if it is imported, no guarantee it doesn't have something dangerous in it, like lead.",
"If you think you have been exposed to a virus, a doctor is your best bet."
] |
[
"I had orange juice in a stainless steel water bottle, with a plastic lid. It sat in my hot car for 2 days. When I brought it inside to clean it, the cap shot off (like a champaign cork). Then inside, was a bunch of fog, and the bottle got really cold. What happened?"
] |
[
false
] | null |
[
"The orange juice fermented. Over those two days it built up a head of CO2 pressure.",
"The vapour and cooling are a product of rapid decompression."
] |
[
"homebrewer here, two days in a warm temp op is very lucky the cap didn't fail"
] |
[
"Some sort of decomposition is likely the cause of increase in gas pressure. Fermentation is the most likely cause due to high sugar content of orange juice. I am impressed that the plastic lid managed to contain such a high gauge pressure that would allow you to notice a temperature change, but it's certainly not implausible."
] |
[
"How long would it take two bowling balls (one metre apart from each other) to collide in empty space?"
] |
[
false
] |
How long would it take two bowling balls (one metre apart from each other) to collide in empty space assuming they had no previous velocity? In Universe Sandbox 2, they only take about a day to collide. Would this actually happen?
|
[
"We can just use Kepler's third law to find the period of the motion, from which we can get the collision time. No need for any fancy calculations, or any need to approximate the acceleration as constant (because it most certainly is not). But if you want to solve the problem from first principles...",
"Put the center of the mass of the two balls at the origin ",
" = 0, which will never move because there are no external forces on the balls. The positions of the two balls are ",
" = -r and ",
" = +r. The acceleration of the right ball is given by",
"r'' = -k/r",
"where primes denote time-differentiation and k = GM/4. For a first integral, we can use conservation of energy (equivalently, multiply both sides by r' and integrate once). Using the initial conditions r(0) = R and r'(0) = 0, we have",
"r'",
"/2 - k/r = -k/R",
"This differential equation is separable, with the initial condition r(0) = R. But we don't need the general expression for r(t). We are just interested in the collision time ",
" such that r(T) = 0. Hence, we have to solve the equation",
"[; \\int_0^R{\\frac{1}{\\sqrt{\\frac{1}{s}-\\frac{1}{R}}}\\,ds} = \\sqrt{2k}T ;]",
"The integral on the left can be done via the trigonometric substitution s = R sin(u)",
". The end result is",
"T = √[ d",
"π",
" / (16GM) ]",
"where I defined ",
" = 2",
", the initial distance between the balls. (Note that this is just Kepler's third law.)",
"If M = 5 kg and d = 1 m, then we get ",
"T = 0.4976 days",
".",
"The balls don't actually collide when ",
" = 0, but rather when they first touch. So you can be more precise if you define the collision time ",
" to be such that ",
"(",
") = ",
", where ",
" is the radius of either bowling ball. If you go through everything, you should get",
"[; T = \\sqrt{\\frac{d^3}{4GM}}\\left[\\frac{\\pi}{2}+\\frac{\\sqrt{a(d-2a)}}{d}-\\sin^{-1}\\left(\\sqrt{\\frac{2a}{d}}\\right)\\right] ;]",
"So now let's put ",
" = 11 cm. The collision time is then a bit shorter at ",
"T = 0.4358 days (about 10.46 hours)",
"."
] |
[
"This is a second-order nonlinear differential equation and I'm not aware of an analytic solution",
"The energy is a first integral of the motion, giving you an equation for conservation of energy. The resulting first order differential equation is separable and can be solved via a simple trigonometric substitution. But you only get ",
" = ",
"(",
"), and the function ",
" cannot be inverted in closed form."
] |
[
"This is a second-order nonlinear differential equation and I'm not aware of an analytic solution",
"The energy is a first integral of the motion, giving you an equation for conservation of energy. The resulting first order differential equation is separable and can be solved via a simple trigonometric substitution. But you only get ",
" = ",
"(",
"), and the function ",
" cannot be inverted in closed form."
] |
[
"Why do infants lose certain abilities around 6 months old, such as distinguishing between different language sounds and different primates' faces?"
] |
[
false
] | null |
[
"It depends on who you ask. There are two major accounts:",
"The critical period hypothesis posits that humans have enhanced sensitivity to certain contrasts (typically linguistic, but you've noted some others as well) that goes away as we age. This is usually held to be a maturational process, and it follows that lack of exposure to the correct input at the right time would result in a lack of learning the discrimination task in question (e.g., sound contrasts in native languages, differentiating human faces).",
"However, there's reasonable evidence (e.g., Bouton, Serniclaes, Bertoncini, & Cole, 2012) that humans can learn some of these discrimination tasks to a performance level similar to a native speaker when exposed later in life - in this particular instance, because they did not gain hearing until later in life due to cochlear implants. This suggests that what is happening is a result of experience, perhaps changes in how information is represented or changes in sensitivity of the underlying statistical mechanisms that leads to this loss of fidelity.",
"I tend to think that this is a result of learning rather than a biological maturational process, and in my work I look at learning mechanisms that might explain this loss of discrimination as a result of experience.",
"Bouton, S., Serniclaes, W., Bertoncini, J., & Cole, P. (2012). Perception of speech features by French-speaking children with cochlear implants. ",
", 55(1), 139-153."
] |
[
"I think a more general description might be that infants don't know what features / dimensions are relevant for discrimination / tasks / living / survival. ",
"An interesting example of this might be a gradual loss of mirror symmetry invariance which seems to happen as we learn how to read. For most objects in the natural world, it doesn't matter what side we see them from so we have some amount of mirror invariance. However, this invariance is a problem when it comes to discriminating between 'b' and 'd'. Children confusions between these letters gradually decrease from ages 4-8 (",
"Gibson et al. 1962",
"). That is, we lose some amount of mirror invariance. ",
"Although this seems like the opposite of the examples above: losing ability to discriminate between faces or phonemes, the explanation for losing an ability in one case and gaining one in another (discriminating letter forms) may actually have the same underlying explanation. ",
"For a comprehensive summary of some earlier research, see ",
"; for a more modern take, see ",
"Pegado et al. 2014",
" <-- pdf which also compares to illiterates who retain mirror constancy into adulthood. "
] |
[
"I'm not sure I follow your question, so I'll take both of the interpretations I see.",
"In one sense, one might worry about the brain \"filling up\", like a sponge that cannot retain any more water. We don't have good evidence for this being the case, and I think it's unlikely because the amount of neurons and possible connections within the brain (both posited as mechanisms of memory) are really, really large.",
"In another sense, the brain might stop interpreting parts of the signal that don't seem to matter. This might happen at the perceptual level (e.g., in sensory adaptation, where we stop perceiving things that remain constant) or at the representational level (e.g., as we learn a representation for some thing, we no longer retain the non-diagnostic characteristics of that thing). We've got pretty good evidence for both of these processes occurring (see Webster, 2012 for a review of sensory adaptation, and, uh, Doumas, Hummel, & Sandhofer, 2008 for a dense account of the latter).",
"Doumas, L. A. A., Hummel, J. E., & Sandhofer, C. M. (2008). A theory of the discovery and predication of relational concepts. ",
", 115(1).",
"Webster, M. A. (2012). Evolving concepts of sensory adaptation. ",
", 4(21)."
] |
[
"Exactly how does water temperature affect Dissolved Oxygen?"
] |
[
false
] |
I heard in class that the temperature of water can affect its ability to hold dissolved oxygen, How that that work?
|
[
"Temperature effects the amount of any gas that can be dissolved in water. When oxygen dissolves in water, intermolecular forces between the water and oxygen \"hold\" them together. As the water-oxygen solution gains energy, heat, the bonds between gas and water break, releasing the oxygen."
] |
[
"Thanks, good to know"
] |
[
"It's worth adding that heat actually tends to make solids dissolve better and gas dissolve worse. This is because gases want to be more spread out than liquids, and heat increases this. Meanwhile, solids want to be less spread out than liquids, and heat makes them spread out better."
] |
[
"Is the imposter syndrom more common among people who are a minority in their job?"
] |
[
false
] | null |
[
"Imposter syndrome is common for those that come from families of over achievers. It occurs in both women and men, as well as all races. However, it's more common among minorities. So, to answer your question, yes. Here's more info if you'd like to have a look: ",
"http://www.apa.org/gradpsych/2013/11/fraud.aspx",
" "
] |
[
"I believe, generally, being white is a statistical predictor for more academic achievement in the north american education system. While it is a statistical correlation (and admittedly we can't say for certain) this is likely due to white people being statistically more likely to be financially secure/having parents who are post secondary graduates. Especially in the United States socioeconomic position is a huge determining factor in education level.",
"Having a parent who finished post secondary schools is IRC one of the highest indicators for attending, and graduating from, a post secondary institution."
] |
[
"I believe, generally, being white is a statistical predictor for more academic achievement in the north american education system. While it is a statistical correlation (and admittedly we can't say for certain) this is likely due to white people being statistically more likely to be financially secure/having parents who are post secondary graduates. Especially in the United States socioeconomic position is a huge determining factor in education level.",
"Having a parent who finished post secondary schools is IRC one of the highest indicators for attending, and graduating from, a post secondary institution."
] |
[
"Do animals have dopamine and serotonin?"
] |
[
false
] | null |
[
"Yes the whole animal kingdom has dopamine. There is even one report that sponges (which don't have a nervous system) have dopamine, yet its function in sponges are not known.\nThere is dopamine in jellyfish, hydra or corals. Because of this we know that the emergence of dopamine as a neurotransmitter goes back to the earliest appearance of the nervous system, over 500 million years ago.",
"In every type of animal that has been examined, dopamine has been seen to modify motor behavior. Dopamine has also consistently been shown to play a role in reward learning, in all animal groups.",
"There is a publication called ",
"'The Roles of Dopamine and Related Compounds in Reward-Seeking Behavior Across Animal Phyla'",
". Im not sure if you can open it though.",
"Serotonin is also found in almost all bilateral animals from worms to insects to mammals. Also in fungi and plants. (e.g. Serotonin's presence in insect venoms and plant spines serves to cause pain, which is a side-effect of serotonin injection.)\nSerotonin is even produced by pathogenic amoebae, and its effect in the human gut is diarrhea"
] |
[
"Dopamine also plays a huge role in regulating your movement. Parkinson’s disease is caused by low levels of dopaminergic cells in your basal ganglia (very primitive portion of your brain that controls movement). I couldn’t imagine any kind of animal with a brain (these structures are very evolutionarily old) not having dopamine transmission."
] |
[
"A neurotransmitter is a substance that helps neurons (hence the first part of the name) to cross the gap to the next neuron and transmit (hence the second part of the name) information.",
"Plants and fungi don't have neurons at all."
] |
[
"If the sun were to disappear for 10 seconds, what (if anything) would happen hear on earth?"
] |
[
false
] | null |
[
"I think the idea was what would happen if the light from the sun were prevented from reaching the Earth for 10 seconds and then uninhibited afterwards. Although I suppose I'm interested if the rapid removal of the sun's gravitational pull would have a significant effect, but you seem to be saying that somehow not modellable. "
] |
[
"I think the idea was what would happen if the light from the sun were prevented from reaching the Earth for 10 seconds and then uninhibited afterwards. Although I suppose I'm interested if the rapid removal of the sun's gravitational pull would have a significant effect, but you seem to be saying that somehow not modellable. "
] |
[
"This question will always be a bit ill-defined, since there is no physical way to make the sun disappear for 10 seconds. But we can speculate, assuming that we could use Newtonian gravity equations and that no extra violent radiation was produced by the sun popping in and out of existence. Let's start with gravity effects. These would be pretty minor: the earth would travel in a straight line instead of an elliptical orbit for a bit, but it wouldn't get too far off course. You would lose tidal forces for a bit, but there is enough inertia in the water/crust that there wouldn't be much of an effect here. Next we can deal with the solar radiation. This wouldn't be too different from a solar eclipse, so a little darkness but no major effects on the temperature. There would be an interesting \"winking\" on and off of the moon and the planets, since the dark pulse would take a different amount of time to be seen depending on how far each one is from the sun and from us. All in all, ten seconds of no sun wouldn't be so bad.",
"What if we waited longer? There are many answers on this on the web. ",
"Here",
" ",
"are",
" ",
"a few",
". The tldr is that in a few days it would get too cold to survive on the surface, and growing food/finding energy would be too hard to solve before everyone dies."
] |
[
"Why is Iron the first element whose fusion does not create energy?"
] |
[
false
] |
It's always said Iron creation signals the death of star due to this property, what is it about iron that makes it the tipping point?
|
[
"At first the nuclear strong force holds the nucleons together, but adding more makes the electric repulsion from the protons more and more significant, and iron's the point where it balances out and adding nucleons takes more energy than it releases."
] |
[
"This isn't wrong, exactly, but it is a very simplistic explanation. Nuclear binding is far more complicated than coulomb repulsion vs strong force attraction. "
] |
[
"Can you please elaborate a bit further? "
] |
[
"Why are we not acidic?"
] |
[
false
] |
From my understanding, we are almost entirely made up of proteins which are chains of amino acids. If that is true, then why is our pH 7.35-7.45 rather than <7?
|
[
"The pH of what? We have a wide range of pHs in our body. Do you mean our skin? Our skin is actually acidic, if just mildly so. Same with hair. Blood is slightly alkaline. Stomach is obviously acidic (stomach acid). Saliva and urine changes depending on diet. Gotta be more specific if you want a good scientific answer :)"
] |
[
"Take a human, stick it in a blender until all the bits blend together into a human smoothie, then measure the PH of that"
] |
[
"The \"acid\" in amino acids refers to the carboxylic acid on the C-terminal side of the backbone, but doesn't actually mean the amino acid has acidic properties, it's just a naming convention. Most amino acids balance out around 7 because in water, the carboxylic acid will give up a proton while the N-terminus snags a proton. The net change in pH is thus largely negligible."
] |
[
"If no elephant was alive today and the only record we had of them was their bones, would we have been able to accurately give them something as unique as a trunk?"
] |
[
false
] |
Edit: To clarify, no fossils. Of course a fossil would show the trunk impression. My reason for asking this question is to understand when only bones are found of animals not alive today or during recorded history how scientists can determine what soft appendages were present. Edit 2: from a picture of an elephant skull we would have to assume they were mouth breathers or the trunk attachment holes were the nose. From that we could see (from the bone) that muscles attached around the nose and were powerful, but what leads us to believe it was 5 foot long instead of something more of a strong pig snout? Edit 3: so far we have assumed logically that an animal with tusks could not forage off the ground and would be a herbivore. However, this still does not mean it would require a trunk. It could eat off of trees and elephants can kneel to drink provided enough water so their tusks don't hit bottom. Edit 4: Please refrain from posting "good question" or any other comment not furthering discussion. If this gets too many comments it will be hard to get a panelist up top. Just upboat so it gets seen! Edit 5: We have determined that they would have to have some sort of proboscis due to the muscle attachments, however, we cannot determine the length (as of yet). It could be 2 foot to act as a straw when kneeling, or it could have been forked. Still waiting for more from the experts. I have been told that no matter if I believe it or not, scientist would come up with a trunk theory based on the large number of muscle connections around the nose opening (I still think the more muscles = stronger, not longer).
|
[
"I recently made a post about elephant skulls as well (after having the OP post in my thread, I thought I would contribute here):\n",
"http://farm3.staticflickr.com/2718/4378175875_61dc2b8fdd.jpg",
"That's the skull of an indian elephant. I suspect that with such a large entrance way for the bone, we could suspect that there was a large set of fleshwork coming through said hole (I make this supposition through what folks linked to and specialists said in my post about the similar topic here: ",
"http://www.reddit.com/r/askscience/comments/p2aa7/if_elephants_were_entirely_extinct_in_the_modern/",
"Lastly, I wonder if through the lobes of bone on the skull, we could determine a proximate angle for which direction the muscles would extend? Scientists would have the size and angle of the hole in the skull, as well as the latching-on points on the skull to determine the nature of the trunk.",
"Thanks for reading."
] |
[
"I often wondered the same about a sperm whale. ",
"http://www.whalesongs.org/cetacean/sperm_whales/sperm_skeleton.gif"
] |
[
"We have indeed found ",
"preserved mammoths",
"."
] |
[
"How do scientists measure extreme depth without sending in people/robots?"
] |
[
false
] |
Assuming that a person had access to equipment and resources, how would they measure the depth of a hole? Is there a limit to how deep people/drones/robots could travel into it safely? How would you measure how deep it was long past that point?
|
[
"I'd send a sound wave down and measure when the echo came back. Know the speed of sound, depth = echo time * speed of sound / 2. 2 for down and back. SoS = 340 m/s. You could probably measure the echo to somewhere around a millisecond, so accuracy on the order of a meter. ",
"https://en.m.wikipedia.org/wiki/Echo_sounding"
] |
[
"Same method also holds for finding the depth of surfaces within the lithosphere. ",
"https://en.wikipedia.org/wiki/Reflection_seismology",
"Also ... we're ",
" sorry about autotune..., a spinoff from this technology."
] |
[
"Also ... we're really, really, REALLY sorry about autotune..., a spinoff from this technology.",
"Looks like some post-doc became angry cause he never got a tenured position. So he became a super villain who created an infernal machine and throw it on the world ;) "
] |
[
"Did Newton know his theory of gravity was incomplete?"
] |
[
false
] |
Did Newton realize his theory of gravity was incomplete in that it did not take into account time distortion caused by gravity? If not that specific did he know something was wrong but did not know what?
|
[
"Yes. He knew he did not understand the mechanism behind gravity, and was uncomfortable with the fact that there was action at a distance. In his 3rd letter to Bently in 1692 he wrote.",
"\"It is inconceivable that inanimate brute matter should, without the mediation of something else which is not material, operate upon and affect other matter, without mutual contact, as it must do if gravitation in the sense of Epicurus be essential and inherent in it. And this is one reason why I desired you would not ascribe 'innate gravity' to me. That gravity should be innate, inherent, and essential to matter, so that one body may act upon another at a distance, through a vacuum, without the mediation of anything else, by and through which their action and force may be conveyed from one to another, is to me so great an absurdity, that I believe no man who has in philosophical matters a competent faculty of thinking can ever fall into it. Gravity must be caused by an agent acting constantly according to certain laws; but whether this agent be material or immaterial, I have left to the consideration of my readers.\"",
"Newton did not understand that there could be time distortion, and in newton mechanics space is absolute, but relative to motion. All observers will agree on all distances, and on all time intervals. Observers will not agree on velocities, as these are relative in Newtonian mechanics.",
"During Newton's lifetime no experimental evidence disagreed with his law of gravitation. The first experiment to conclusively to do so was the anomalous precession of mercury of about 43 arc seconds per Century different than Newtonian Mechanics by Le Verrier in the 1840s."
] |
[
"precession of Mercury ",
"The Newtonian Mechanics of gravity are an excellent approximation of General Realitivity when the curvature of space time is small, but loses precision as the curvature increases. When mercury passes closest to the sun (the perihelion) this error causes the orbit of mercury to precess slightly more in GR than in Newton's Gravity. As every other planet has less and less curvature in local space-time due to the sun this effect is much harder to measure with the planets further form the sun.",
"An much deeper explanation of the 43 arc seconds is within ",
"http://classroom.sdmesa.edu/ssiegel/Physics%20197/labs/Mercury%20Precession.pdf"
] |
[
"Can you elaborate on the precession of Mercury anomaly? I would think that bodies on the scale of planets would confirm Newton's laws perfectly. "
] |
[
"CN IV AND VI evolution?"
] |
[
false
] |
Why did abducens(cn 6) nerve evolve to control just the lateral rectus and trochlear nerve(cn 4) controls the superior oblique when occulomotor nerve(cn 3) controls all other muscles of eye movement
|
[
"Short answer: we don't know.",
"Longer answer: the layout of the cranial nerves only makes any kind of sense once you realize all vertebrates are just modified fish. It seems like the cranial nerves used to just be like the spinal nerves, with a dorsal and ventral branch, with the ventral branch mostly innervating the gill arches. This is still the case, with 5, 7, 9, and 10 innervating structures derived from the first, second, third, and posterior gill arches, and their dorsal partners spreading elsewhere.",
"The problem is that we know the locations of the nerves and their targets can and do shift over evolutionary time, and many of the species which could help us resolve which is connected to what and how and why they've shifted are either highly modified due to diverging from us 500+ million years ago (e.g. lampreys, hagfish) or just plain extinct and rarely fossilized with enough skull detail to help (e.g. ostracoderms, conodonts, acanthodians).",
"There's an exceptionally detailed look here: ",
"https://academic.oup.com/book/37442/chapter/331583157"
] |
[
"I just want to mention that simple and rationally satisfying explanations for evolutionary modifications that we observe today may not always be possible. We aren't always able to infer all the evolutionary pressures that these modifications underwent over hundreds of millions of years. Also remember that evolution cannot go back to the drawing board. It can only work with incremental modifications of existing systems."
] |
[
"The link is broken. But that rationale sounds weak - why would a separate nerve improve either response time or control? Is there actual evidence that the lateral rectus response faster or with greater precision than the rest of the oculomotor nerves, either in humans or other species?"
] |
[
"How does anesthesia \"tax the body\"?"
] |
[
false
] |
I recently had surgery and the doctor recommended spinal painkiller instead of general anesthesia due to the latter being very "taxing on the body", and that it takes a while to recover from it. Why is this the case?
|
[
"I am an anesthesiologist.",
"Many of the medications we use to induce or maintain general anesthesia impair your body's ability to maintain physiological homeostasis: You are unable to normally compensate for drops in blood pressure, you lose the ability to maintain your own temperature, you can't regulate the amount of carbon dioxide/oxygen/hydrogen in your blood, you lose your airway reflexes and can't swallow your own spit, etc. Depending on the case, you may not be able to breathe on your own (either because of the surgery, or because I gave you a paralytic).",
"Your inability to do these things forces me to give you other medications or perform other interventions to counteract these changes, and prevent something bad from happening. Depending on your medical history, general anesthesia can be very risky. For example, if you have a heart problem, or a blood pressure problem, your blood pressure might drop to a critically low level at the start of the case or any point afterward. Therefore, I have to do more \"stuff\" to keep your body working properly while you are asleep. Even after I wake you up, it still takes a few hours for you body to fully recover the ability regulate itself again - specifically, it's ability to regulate your breathing, to keep your blood pressure up, to keep your airway open, and so on. That is why you spend time \"sleeping off\" my drugs in PACU - the post-anesthesia care unit - where a nurse can keep an eye on you.",
"When I perform a spinal anesthetic, I am basically putting medication around your spinal cord that makes you numb from the site of injection, down. Since you are numb, I do not have to put you under general anesthesia. But I will usually give you some IV medication to make you sleep (since being awake and numb during surgery is rather boring). This \"sleep\" is not a natural sleep, but it is much closer to a natural sleep than general anesthesia (in that you are still arousable). Like general anesthesia, you do lose some of your ability to maintain homeostasis. But the changes are not nearly severe. You recover your ability to self regulate much faster, possibly even before the spinal anesthetic wears off.",
"(edit: When your doctor said it takes \"awhile\" to recover, I suspect he was referring to the hours it takes to recover from general anesthesia in the PACU vs the shorter time it takes to recover from IV sedation. I doubt he was referring to any long-term effect.)"
] |
[
"To add to this excellent explanation. It is mostly the surgery that taxes the body by causing the release of inflammatory signals. The anesthesia itself, if done right and in a reasonably healthy person, is not all that stressful. A spinal block helps deaden the inflammatory response to surgery significantly, which is perceived as being a less “taxing” anesthetic."
] |
[
"During general anesthesia, you are put to sleep, paralyzed, and then have a breathing tube inserted. You remain paralyzed with the machine breathing for you. ",
"During the surgery, your body can still react to the procedure. You don’t feel pain, but it knows that parts are being cut/sewn/burned etc. but it can’t react the same, which means the anesthesiologist is frequently giving meds to speed up your heart, pump up or lower your blood pressure, drugs to keep you asleep. The surgery itself can mean fluid and blood loss that the anesthesiologist also is keeping up with. ",
"This all as you can imagine means periods when you might have too low oxygen, heart rate, blood pressure, before the machines pick it up and the doc can try to give medicines to correct it, and thus a lot of stress on the system. ",
"Your body does a much better job regulating all of this specific to your needs. So if they can keep some or all of you “awake” and doing it yourself (breathing on your own, etc) it tends to be a lot safer for the body.",
"Edit: changed a contraction to be more clear"
] |
[
"How do we know about the evolutionary history of jellyfish?"
] |
[
false
] |
Wouldn't their squishy bodies just disintegrate into nothing long before we could ever find them?
|
[
"It is important to understand that the ability to directly study the DNA of currently living creatures is beginning to have a huge impact on our understanding of evolutionary history. At one level, scientists can now test for a fairly limited number of DNA \"markers\" in a large number species in a group like jellyfish. This will lead to a pretty clearly resolved family tree, showing things like how closely related the different species are, and roughly when the different groups split off to form their own branches, and when certain shared traits first evolved. At the other extreme, a full sequence of the DNA of a species can reveal an amazing amount of information about its evolutionary history. At the moment, however, this is still quite expensive, and has only been completed for a very limited number of representative species. This is quickly changing, though, as the technology improves and the prices for this kind of work continue to fall.",
"Ideally, this new DNA data is compared to the fossil data to clarify and improve both, but DNA data alone can tell us a lot, even in things like jellyfish that leave behind very little fossil evidence."
] |
[
"Source?",
"In my Fossil Records class we learned that there weren't many jellyfish fossil records compared to other organisms due to the fact that the jellyfish had no \"hard parts\". Typically these hard parts became mineralized, particularly in trilobites. Which is why we have more trilobite fossils in comparison to jellyfish."
] |
[
"Source?",
"In my Fossil Records class we learned that there weren't many jellyfish fossil records compared to other organisms due to the fact that the jellyfish had no \"hard parts\". Typically these hard parts became mineralized, particularly in trilobites. Which is why we have more trilobite fossils in comparison to jellyfish."
] |
[
"Why do wind farms use the horizontal axis blades that have to face the wind instead of vertical ones that capture wind in all directions? (Examples in comment)"
] |
[
false
] |
Traditional horizontal axis Rarely used vertical axis I’m assuming it has to do with efficiency but does anyone know actual ratings? What’s the most efficient vertical turbine and how does that efficiency compare to traditional ones? Is it half as efficient? Is it better than half? When is a vertical a better option? Thanks!
|
[
"Axial wind turbines are significantly more efficient. That means for the same size of tower and same weight of turbine you'll get more output while producing less drag force on the tower.",
"For axial turbines the efficiency is around 35-45% while for vertical wind turbines the overall efficiency is 15-20% at best. I'll explain more about this in a bit.",
"Moreover, for very large turbines, the axial design requires fewer large-size structural parts.",
"Lastly, axial turbines are tolerant of a wide range of wind speeds, whereas peak efficiency for vertical turbines occurs at a narrow range of speeds. Vertical turbines are subject to aerodynamic problems outside of that range, which robs them of efficiency."
] |
[
"One more thing to add on this: your original question states that vertical axis turbines capture wind from all directions. That’s not true. ",
"As other users have noted, axial turbines turn to capture wind from any direction. The problem with vertical axis turbines is that each blade gets pushed by the wind for half of the rotation but then causes drag as that same blade has to move against the wind to finish a rotation. Axial turbine blades are producing energy at all times during their rotation. "
] |
[
"My guess as an engineer who deals with different kinds of turbines would be that it would be hella expensive to manufacture, install or fix compared to the marginally better performance RELATIVE to what is already in use and production. Would it perform better? Probably. A lot better? Probably not. "
] |
[
"How and why do exothermic reactions release energy?"
] |
[
false
] | null |
[
"The ionization potential is the energy it takes to remove (or really move to an infinite distance) an electron from an atom/molecule in vacuum. The electron affinity is the energy gained by adding an electron to an atom molecule, from having been infinitely far away.",
"does this mean in order for a reaction to take place, the electron affinity has to be greater than the ionization energy in order for 2 atoms to want to share or transfer e in a bond? ",
"No, electron affinities and ionization potentials really have nothing to do with bonding energies. The difference in IP and EA between two species will only tell you the enthalpy of electron transfer between them. Bonding is not electron transfer.",
"There is no 'mechanism of electron transfer'. The electrons in atoms and molecules move. And they move quantum mechanically as well, not even having to cross intermediate points in space for getting from A to B. If an electron can lower its energy by being in another spot, there is a probability it will go there, a probability that increases the closer it is spatially, and depending on what's in-between."
] |
[
"What about during Ionic Bonding.. aren't electrons transferred from Cation to Anion? I can understand that they electron simply spends more time on the anion side but when they break up in a solution lets say.. does the electrons still go back and forward between the two ions?"
] |
[
"Ionic bonding is an old and rudimentary model of chemical bonding that works for some situations, but it isn't close to what's actually happening. There is no cation or anion in an ionic bond, electrons are actually always shared when there's a chemical bond, you have a contiguous region of electron density between the two atoms. So there is no straightforward way of determining how much of the electron density 'belongs' to a certain atom, and thus what the net charge on the atom would be. (and ",
" you divide it up, however you do it, you're not likely to end up with an integer) ",
"So for two ",
" ions, you can determine the energy X + Y -> X",
" Y",
" from the IP and EAs, because then there's no bond and the two atoms (provided they're well-separated enough) can be treated as independently of each other. But you can't determine the bonding energy from the IP/EA.",
"The electrons will go back and forth if they're close enough that the electrons are able to do so, and there's no energetic difference depending on where they are. Otherwise they'll tend to stay in the state with lower energy, as with any chemical equilibrium."
] |
[
"Why are \"x\" and \"y\" the two primary variables in most of algebra?"
] |
[
false
] |
On a 2d graph, the axes are always labeled either x or y, as well as many problems being "solve for x" or a basic linear equation of y=x, yet unless you substitute y for f(x), why dont people use "a" and "b" or even "y" and "z"? Who came up with "x" and "y"?
|
[
"If you don't get an answer here, you can also try ",
"/r/askhistorians",
", ",
"/r/math",
", ",
"/r/historyofscience",
", or ",
"/r/philosophyofscience"
] |
[
"Thanks"
] |
[
"Here's a video from the Today I Found Out youtube channel on the subject. ",
"https://youtu.be/cz9q2xa9Wkw"
] |
[
"What would the night sky viewed from a planet in the middle of a dense star cluster look like?"
] |
[
false
] |
I was reading the APOD (astronomy picture of the day) description from July 5 2013 and started wondering what it would be like to be on the night side of a planet in NGC 6752, a globular star cluster only 100 light years in diameter with over 100,000 stars. How bright would it be at night, assuming an earth-like planet orbiting a sun-like star with no moon?
|
[
"However, if you were in the middle of a globular cluster, the average spacing between stars is much less than 1 light year, so you would have both a drastically increased number of visible stars in the sky as well as much brighter stars. ",
"Bad Astronomy",
" calculated that the visible stars in the night sky (when all added up) are about a factor of 10",
" fainter than the full Moon. Even taking your conservative assumption that the stars are only spaced 4 times closer together, that means there are 64 times as many of them visible in the sky (if we assume an identical stellar population, which isn't true, but shouldn't be too big an effect). So it would definitely be a significant increase.",
"However, if we consider the core of a cluster, ",
"where stars are spaced 10",
" or 10",
" times closer together",
" than they are in our neighborhood of the Galaxy, then the visible stars, when taken together, have gotten brighter by a factor of 10",
"-10",
", "
] |
[
"The sky will be a lot more illuminated during the night and perhaps it'll be somewhat easier to see during the night. In fact, some figures put the sky to be brighter than a full moon near the center of a cluster. This has an interesting effect of illuminating everything but only casting light shadows because the light will be omnidirectional.",
"However, the night sky won't be very interesting in terms of features because it'll be mostly uniformly dense with stars throughout (if you are near the center). It'll be a lot more interesting if you are outside of this cluster. Here is what the night sky could look like on a planet around a star near a globular cluster.",
"Picture 1",
"Picture 2",
"Picture 3",
"Picture 4",
"It's quite spectacular if you ask me.",
"EDIT: ",
"Here",
" is screenshot of a procedurally-generated planet near a globular cluster in the game/simulator Space Engine (There is a sub-reddit for this game at [",
"r/spaceengine",
"](en.reddit.com",
"/r/spaceengine/",
"). One thing you could do is try out the game - visit a cluster an such a procedural planet and just look up at the night sky. I've done this on my computer but no longer have the game."
] |
[
"The distance between stars in globular clusters is still immense, on the order of ",
"about one light year average between stars.",
"The closest stars to earth are ",
"roughly four times that",
" (we're not in a star cluster)",
"In short: They night sky wouldn't look that much different. Stars 1 light year away would look about as bright as Jupiter in the night sky. Noticeable, but not really enough to contribute noticeable changes in light on a planet in a system. "
] |
[
"Why is a mylar blanket (first-aid blanket) effective against hypothermia/heat loss?"
] |
[
false
] |
How can something so thin and flimsy be so good at keeping heat where it is?
|
[
"This is exactly it! The space blanket is also waterproof, which helps keep stuff warm and dry. There's a reason why it's thin and flimsy, though! As a former Army medic, one of the biggest limitations we have in the field is space and weight. A space blanket is terrifically small and light for what it does, which saves space for other things that can't be made smaller or lighter, such as IV fluid and bandages.",
"Besides, in the field it's usually easy enough to scrounge up insulation- at the worst, pick up loose dry leaves, crumple up paper, etc.- that an insulating blanket isn't worth the size and weight. Having the space blanket to deal with radiative losses, and act as a waterproof layer, is a much more effective use of space."
] |
[
"This is exactly it! The space blanket is also waterproof, which helps keep stuff warm and dry. There's a reason why it's thin and flimsy, though! As a former Army medic, one of the biggest limitations we have in the field is space and weight. A space blanket is terrifically small and light for what it does, which saves space for other things that can't be made smaller or lighter, such as IV fluid and bandages.",
"Besides, in the field it's usually easy enough to scrounge up insulation- at the worst, pick up loose dry leaves, crumple up paper, etc.- that an insulating blanket isn't worth the size and weight. Having the space blanket to deal with radiative losses, and act as a waterproof layer, is a much more effective use of space."
] |
[
"Beside the noise and tearing issues, you usually want your blankets to let some air through to allow evaporation so you don't get all wet from your sweat and breath."
] |
[
"How do you find the Electronegativity difference between three or more elements?"
] |
[
false
] |
For example, what is the electronegativity difference for Acetone(CH O)? Are there two different answers? 0.4 for C & H, and 1.0 for C & O? Which one do you choose?
|
[
"I might not understand very well the question but if you are trying to find an electronegativity for a compound to try to assess if it would attract electrons I think there are other factors that would affect this.",
"I would say that depending on the compound. In the case of CH2O, which would be formaldehyde, you could see that the oxygen has two pairs of electrons available to be donated. Neither H or C would be available for bonding since they have all the bonds necessary to fill the valence shell."
] |
[
"You're trying to apply something from a binary system to a bigger system. I assume you're trying to find the dipole moment of a molecule. In a biatomic molecule, (A bonded to B) you can just say the potential difference is that of A minus that of B. Bigger molecules require a lot more math per atom.",
"If you're asking because you need homework help its a completely different process than what you're used to. I suggest starting by figure out how to do it with Water, and working your way out from there.",
"Watch this: ",
"https://www.khanacademy.org/science/organic-chemistry/gen-chem-review/electronegativity-polarity/v/dipole-moment"
] |
[
"This is wrong.",
"Electronegativity is ",
" the pull an atom has on the electrons in a covalent bond with another atom. So, in reality, an element does not have one standard electronegativity, and its measured electronegativity will vary based on what it is bound to. We can't talk about the electronegativity of one atom in a vacuum.",
"That isn't to say we can't speak in averages, and for all intents and purposes (Though not technically), the effective electronegativity of an oxygen atom bound to a carbon atom will be more or less the same."
] |
[
"Does the gravity pull that causes the tides lead to a change in an objects weight? (e.g. high tide 50 kg, low tide 49.5 kg?)"
] |
[
false
] |
Obvious title is obvious. ninja edit: Object's
|
[
"Yes, though the effect is tiny. Since the force of gravity is directly proportional to mass and inversely proportional to distance squared, ",
"the effect is roughly one part in 300,000."
] |
[
"(e.g. high tide 50 kg, low tide 49.5 kg?)",
"It is exact opposite. Moon also pulls you.",
"Longer version: When on same side than Moon, you (and water) are being pulled more than the rest of the Earth since it is further away from the Moon. When on opposite side, you (and water) are being pulled less than the Earth since you are further away - so again ~same result. Sun also counts, but in lesser way because it is so far away so there isn't much difference on either side of the Earth."
] |
[
"Weight = Mass * Acceleration of Gravity, where weight and mass are written in the same unit (e.g. kg)- right? "
] |
[
"Are there any factors that have actually been shown to affect which sex a baby will be when born?"
] |
[
false
] |
I've heard of anecdotal reasons like mother's diet but have there been any serious studies on this topic?
|
[
"There is one common proposition that sex during ovulation is ",
" slightly more likely to result in a boy, while sex a few (2.5-3) days before ovulation, is ",
" slightly more likely to result in a girl. This is because x sperm live longer than y sperm, but swim slower. Sex during ovulation means the faster y sperm will have a greater presence at the egg during fertilization. Sex before ovulation means that some of the y sperm will have died off, leaving a higher presence of x sperm. This is called \"Shettles Method.\" However, remember that the odds are still very close to 50/50, and methods like this have a significant lack of non-anecdotal evidence. There is no known morphological difference between x and y sperm, according to the British Medical Journal."
] |
[
"There's some evidence that women in less than well-fed circumstances (so not quite starving but not far) give birth to a higher proportion of girls. This is a variant of the \"Trivers–Willard hypothesis\", but the general feeling is that daughters represent a more guaranteed chance of having grandchildren, versus sons are more of a gamble (less likely to survive to adulthood, less likely to reproduce if they do, but more likely to have a higher # of children if they're successful). In more resource poor states, evolutionarily speaking, it may make more sense to have less sons.",
"That said, the evidence is weak, and no one would recommend starving yourself to try to increase your odds of having a girl."
] |
[
"I suppose that in the end it's most beneficial for a species overall to produce an equal number of males and females, therefore creating the highest number of mating couples.",
"Of course not all species have a single mate for life, especially humans, but starting with a 50/50 ratio is the best starting point."
] |
[
"Can Nuclear Reactors Become More Fuel Efficient?"
] |
[
false
] |
I'm trying to gauge whether demand for uranium will increase in a more or less linear manner with an increase of the number of reactors (and demand for energy), or whether technological advances in reactor design could result in greater fuel efficiency and therefore steady or even declining demand for uranium even as more reactors come online. So, is the amount of energy released directly linked to the amount of fuel present, or is it possible to do more with less? Thanks for any replies!
|
[
"Can Nuclear Reactors Become More Fuel Efficient?",
"Definitely. The question is really do we need them to be?",
"Almost all the reactors in the world are \"once-through\" Light Water Reactors ",
"(LWR)",
". Their designs are simple and they are cheap to build and run. They work by fissioning the U-235 in enriched uranium. U-235 is the famous isotope of uranium that makes up only a small fraction (0.7%) of uranium but most importantly is ",
", this means that it can undergo a nuclear chain reaction.",
"This does not mean that the ",
" isotope of uranium (U-238) does not have any extractable energy, it is just harder to get access to. This isotope does not spontaneously decay, you first have to react the U-238 with a neutron to make an unstable isotope which decays similar to how U-235 decays.",
"Since U-238 makes up the majority of uranium it contains the majority of the energy. Something like 60-100 times more energy is stored in the U-238 than in the 235.",
"There are types of reactors called breeder reactors which can access this energy, they are designed such that there is a significant population of fast neutrons (or indeed thermal neutrons in even more advanced designs) which can react with the fissionable components of your fuel and cause them to release their stored energy.",
"Interesting aside here is that the majority of the energy released in thermonuclear (fusion) bomb comes from the fissioning of U-238 which is in turn caused by the neutrons emitted from the fusion of the hydrogen. This makes \"fusion\" in fusion bomb a little bit of a misnomer!",
"The reason we don't use fast breeder reactors is mostly economics, though also political. They were popular before (50s-60s), partly because they can produce weapons grade plutonium, but since then we have discovered more uranium deposits and made our uranium enrichment designs cheaper and more effective. The abundance of cheap enriched uranium means we don't have to worry about being efficient with it.",
"There are good reasons to switch to more modern reactor designs though, despite their increased cost. There are currently 4 ",
"EPR reactors",
" being built (or about to start work) in the world, 1 in Finland, 1 in France and 2 in the UK. These can burn lightly enriched uranium, reprocessed spent uranium and even a fuel called mixed oxide fuel ",
"(MOX)",
" which is a mix of weapons plutonium and natural/enriched/depleted/fuel grade uranium.",
"There are also even more capable designs such as the canadian ",
"advanced CANDU reactor",
" which can burn completely unenriched, nautral uranium. No plans to build one as of yet.",
"So in summary (TLDR) yes we can be 60-100 times more efficient with our uranium fuel but it requires much more expensive and complicated reactor designs called breeder reactors. Some of the newest commercial reactors being built are breeder reactors but enriched uranium is cheap so there isn't as much pressure to be efficient with it as you might expect."
] |
[
"Not a fan today, I could be convinced in the future.",
"The most important difference is that EPR reactors are here now, we are building them they have advantages over Gen 3 and gen 2 reactors but they aren't future tech and so don't have some of the advantages that gen V+ have.",
"LFTR have an extremely aggresive propaganda machine, I don't think this is a coordinated effort but rather some people have been convinced of a proposed problem and the aspects of LFTR that solves that problem. These people have been enthused and have passed on the message, the hype is dieing off a little these days but you still see it in most popular nuclear energy threads.",
"LFTR introduces problems we cannot solve at the moment, these problems are numerous and broad but to me there is one that stands out: We can't provide materials that we can build an LFTR from. This is fundamental, we can still design them but until we can build corrosion-less materials that don't become brittle from neutron exposure the ship will never sail.",
"A lot of the advantages that the internet hypes about LFTR are unfair, they are comparing LFTR to gen 2 reactors whereas modern designs and future designs of commercial reactors do not have these problems. If you compare them to Gen IV reactors (i.e. ones that will become available commercially maybe around 2030) then these differences are not there. For example, Gen IV designs are all meltdown proof which is one of the positives of LFTR.",
"Other advantages that are touted are false advantages, where you say X is better than Y at Z but the truth is that no one needs Z to be any better. An example of that is the fuel abundance, the abundance of Thorium on Earth is frequently claimed as an argument for LFTR. My original comment in this thread is exactly about this Uranium is abundant enough that we are using it extremely inefficiently, if there was a supply problem then we could just switch to more efficient Uranium fueled designs rather than have to switch to Th designs.",
"LFTR and all MSR to be honest bring their own unique disadvantages and an all around lack of development that doesn't get mentioned as much as it should in discussions around them.",
"Those benefits of LFTR reactors that are not also present in other modern designs are also exaggerated. For example the Thorium is very abundant yes but the U-233 needed is close to non-existent. It produces less long lived waste yes but the stuff it does produce is water soluble (obviously awful for storage).",
"If you want a future design that I can really get behind then VHTR are excellent and we can probably build one in 15 years, in particular the pebble-bed core VHTR designs seem all around excellent.",
"Overall, we shouldn't give up on molten salt reactors but for now they are not competition. We are talking about 2050 and beyond for a feasible design if we solve serious material and waste management challenges. In comparison there are many Gen IV and gen V designs that bring the same advantages and are within reach technologically, we could see a pebble bed reactor in 15 years.",
"edit: apologies for rambling on much longer than I was going to."
] |
[
"There are also even more capable designs such as the canadian advanced CANDU reactor which can burn completely unenriched, nautral uranium. No plans to build one as of yet.",
"Just to clarify: (nonadvanced) CANDU reactors that burn natural uranium have been around for a long time."
] |
[
"Why can we still hear the cosmic microwave background? How much longer will we be able to hear it? The big bang was almost 14 billion years ago, how can we possibly see something from that long ago given that it no longer exists?"
] |
[
false
] | null |
[
"One thing that tends to confuse people here is picturing the Big Bang as an explosion from a point. Currently, the universe appears to be infinite in size, and so it's better to picture an infinite universe where everything has just been getting further apart from everything else in every direction. The universe started very hot and dense, and started to become cooler and less dense at it spread out. This hot and dense early material was opaque, but at some point it quick rapidly transitioned into a cooler thinner state that was transparent. The last photons from the opaque stage could then freely escape and fly through the universe to be observed by telescopes. These photons are the cosmic microwave background.",
"These photons were emitted about 13 billion years ago. But the speed of light isn't instantaneous, and the universe is either infinite in size, or at least huge enough that we can't tell the difference. This transition from opaque to transparent happened at about the same time everywhere, so we're just receiving the photons that have travelled for 13 billion years. These photons have travelled a distance of 13 billion light years, although the stuff they were emitted from is more than 13 billion light years away because the universe continued to expand \"behind\" the photons. In another 10 billion years, we will be receiving the photons that have travelled even further, and so on forever.",
"Basically, we can see things that don't exist because it takes time for the light to reach us, and the light wasn't just emitted from a single point.",
"However, the cosmic microwave background is dimming over time. As the universe expands, the photons are spread out over a larger volume. The individual photons are also being stretched out and losing energy. So we have fewer CMB photons and they have less and less energy all the time. It won't shut off, but eventually it'll become so dim that it can't be observed."
] |
[
"We receive the photons forever because the universe is infinite. The photons were released over a fairly short period of time, but in an infinite universe, there are infinite ",
" for when those photons will reach us.",
"Right now we are receiving photons that have travelled about 13 billion light years over about 13 billion years. In 7 billion years, we will receive photons that have travelled 20 billion light years over 20 billion years.",
"We're always receiving photons from the same moment in time, it's just that the location in ",
" that these photons came from is increasingly distant, and the delay between being emitted and being received has increased, because the photons had to travel further.",
"Imagine that I'm a supervillain who instantly sent out a hypnotic command to the entire world that forced everybody to run towards the Eiffel Tower as quickly as they could. First, the people near the Eiffel Tower would arrive. Then other people from local areas in Paris. Then other people from further out in Paris, then further out in France. Later, people from other countries in Europe would start to arrive, and then people from Africa and Asia, and North & South America. Eventually people from Oceania would turn up.",
"This doesn't mean that my magic hypnotic signal lasted forever - it could have been instantaneous. It's just that the Earth is quite large, and it's going to take a long time for everyone to arrive. And because people are spread out all over the place, you're going to have people continually turn up for a long time.",
"With the cosmic microwave background it's similar, except that the universe seems to be ",
". The CMB photons were all emitted over a fairly short time period. It just takes time for those photons to reach us from distant parts of the universe. And, unlike the Earth, we won't run out of space, which means that there's always a more distant part of space whose photons are just reaching us now."
] |
[
"We don't hear it, we see it. It's photons. It's still around because the universe has a non zero temperature. The temperature has decreased as the universe has expanded and will further decrease in the future, and the thermal radiation of the universe (CMB) will shift further to longer wavelengths, which at some point in the future may become difficult to detect. "
] |
[
"What do wild animals die from mostly?"
] |
[
false
] |
[deleted]
|
[
"That's how I want my obituary to read: \"died from inadequate fitness to circumvent the circumstances of his death\" "
] |
[
"Your question needs to be scoped. ",
"What do you mean by \"animal\"? Chordate? Animalia? Metazoa? Eukaryotes?",
"What do you mean by \"mostly\"? Are you asking about the circumstances under which the largest number of individuals cease life-sustaining function? Are you asking about the circumstances that arrest metabolic function for the largest biomass?",
"What and where do you mean by \"wild\"? Not under the custodianship of humans? Living in wilderness reserves?",
"To what time periods do you refer? Ecosystems and environments constantly change.",
"What do you mean by \"from\"? Any event has immediate and distant factors. Being eaten is easily identified as an immediate cause of death of an individual, but an individual's edibility in any context is conditioned by all manner of contingencies. ",
"Depending on how you scope your question, possible answers might include hunting, predation, disease, malnutrition, old age, ... ",
"A cheap but unsatisfying answer would be that most organisms die from inadequate fitness to circumvent the circumstances of their death."
] |
[
"I don't think it is necessary to be so pedantic. It is reasonable to assume that a layperson is referring to animalia, and the scope of answers they are expecting is something like: disease, killed by other animals, starvation, environment. ",
"We can roughly divide environments, so that may a good place to start. What is the most common cause of death in the ocean, in the desert, the rainforest etc. or you divide by size: most large animals die of <blank> while most small animals die of <blank>.",
"Start somewhere, a lot of questions in this subreddit are vague, but appreciate that this person doesn't understand much about the subject matter. ",
"I am interested in the answer to this question so I hope you update your answer."
] |
[
"Are epigenetic changes passed on mostly through the matrilineal line?"
] |
[
false
] |
[deleted]
|
[
"This is in reference to maternal imprinting, which is one of the sole examples of a truly epigenetic trait passed across generations. In imprinted genes, DNA accumulates methyl marks that can regulate the locus. Histone marks are really not epigenetic in the trans generational sense as the marks are removed during the preimplantation phase of embryogenesis"
] |
[
"Mostly, but there is alot we don't know it seems that epigenetic information carried by parental sperm chromosomes can cause changes in gene expression and development in the offspring. ",
"https://www.nature.com/articles/s41467-019-09141-w",
" . Also Mitochondrial DNA is epigenetic."
] |
[
"My guess was that it was because the mother carries the foetus for nine months so, and I know Reddit doesn’t like a Wikipedia reference, but i looked on there and found this on the ",
"Transgenerational epigenetic inheritance",
" page:",
"During fertilization the male and female gametes join in different cell cycle states and with different configuration of the genome. The epigenetic marks of the male are rapidly diluted. First, the protamines associated with male DNA are replaced with histones from the female's cytoplasm, most of which are acetylated due to either higher abundance of acetylated histones in the female's cytoplasm or through preferential binding of the male DNA to acetylated histones."
] |
[
"What else do electrons interact with besides protons?"
] |
[
false
] |
I know that electrons are attracted to protons, and together they form matter. But, from my understanding, matter makes up a very teeny tiny percentage of space. I'm curious to know if electrons have a wide variety of interactions with other things, and we only know about matter because that's the only interaction that actually produces large clumps of stuff. In other words, do electrons exhibit this really great range of behaviors, and the fact that it also takes part in making matter is just a small part in all of that?
|
[
"Well technically, the electrons don't interact with the protons directly. Electrons interact with ",
" (electromagnetism) that then interact with protons. Electrons also interact with W",
" and Z",
" bosons in particle decays. While it seems like a bit of pedantry, it's really the key to your question. Because whatever else photons and W and Z bosons couple too are all of the things electrons can interact with.",
"Outside of forces ",
" it's also important to note that energy of any kind carries a space-time curvature with it, and that gives rise to gravitational effects (though on a single-electron basis, this is largely negligible). Electrons are also fermions, so they obey Pauli exclusion principle and thus can't have more than one electron in the same state."
] |
[
"Dunno how I missed that. Sorry."
] |
[
"They also interact gravitationally, a fact particle physicists often forget."
] |
[
"What would happen to an electron and proton in a vacuum?"
] |
[
false
] |
I know that they would accelerate towards each other due to the electromagnetic force. But, what happens once they become very close, to the point where they reach their highest velocity? Would they collide, with the kinetic energy accumulated in the acceleration being used to form a chemical bond (making a hydrogen atom)? If they would stick together and make a hydrogen atom, how does that entire process not lead to an increased entropy of the universe?
|
[
"The entropy has increased, because they have emitted photons."
] |
[
"You get hydrogen."
] |
[
"Right, but then the entropy of the system has decreased. What would account for the overall increase in entropy of the universe should this process occur?"
] |
[
"I'm ex-military, and today when playing a new first person shooter, I swear you, I smelled gunpowder. What causes that, and how does it work?"
] |
[
false
] | null |
[
"Mostly priming, which is how we humans relate on thing to another. This is the reason why for instance if I say \"red\" you might think of blood or a firetruck and so on. Because you're so used to smelling gunpowder after a fired shot your brain expects it to happen again so much that you actually believe you can.",
"I guess you could also connect this to operant conditioning where a certain stimuli (firing a virtual gun) brings about a ",
" response (the smell of gunpowder). This works similarly to priming (mostly because both of these processes are connected to your memory) as you've gotten so used to the specific response of the perceived stimuli.",
"Source for ",
"priming",
" and for ",
"operant conditioning",
" ",
"classic conditioning",
" Thanks to OutFlanked for clearing that out.",
"EDIT: I guess the point I'm trying to make is that the human brain is always searching for meaning and correlations which helps us organize our memories. This can also be seen as an evolutionary trait since we can more quickly discern and analyze a situation and it's proper course of action. You've probably received training in muscle memory during your time in the military and the aforementioned concepts are what those exercises are funded upon. ",
"Fun fact",
" about the human brain; we're so desperate to find meaning and correlations that we find it even when it's not there. For instance, if you're in the shower the seemingly meaningless rhythm of the water when we shower that we often perceive noises that aren't there, such as your phone ringing. This is called apophenia."
] |
[
"Isn't this a textbook case of Classical conditioning? Operant conditioning is about an individual's behavior, whereas this seems to be a case of OP connecting two stimuli: combat, or gunfire or whatever being associated with the smell of gunpowder"
] |
[
"This is a reminder that anecdotes (i.e., \"me too!\" answers) will be removed. Please keep answers scientific and well-sourced if possible."
] |
[
"What are any current \"embarrassments\" in Science?"
] |
[
false
] |
I was watching this Lawrence Krauss lecture ( , great lecture by the way), and he mentions that at one time in our history we knew the Earth was at least 4 billion years old, but the universe was estimated to be younger. So, this was embarrassing that the Earth was older than the universe. My question is: what current big contradictions, if any, exist in Science? I know there are several "theories of everything" which contradict, but no one is claiming that we can really estimate which is true or false (otherwise there wouldn't be competing theories for the same thing). An example would be if rock dating techniques disagree on something nontrivially, different ways to measure the mass of a proton disagree wildly, etc. Thanks!
|
[
"The predicted vacuum energy density from quantum field theory is 107 orders of magnitude greater than the observed value. This is the most embarrassing prediction in the history of science."
] |
[
"We don't know how supernovae actually explode... computer simulations can't make them explode for whatever reason.",
"Despite many many years of studying the problem, we still don't have a really good grasp of star formation."
] |
[
"I work in star formation, and the problem with the small-scale modelling seems to be that ",
" has any idea what to do about the magnetic fields. ",
"Most conferences I've been to about this always have the magnetic fields folks saying \"seriously, you need to include these\", then the rest of the time is spend ignoring their advice because it's really hard."
] |
[
"What do we mean when we say something \"died of old age\"?"
] |
[
false
] |
[deleted]
|
[
"Dying of old age is certainly not a medical term. It means that the person or animal died of natural causes that are related to the natural aging of that species. usually related to some kind of cardiac or organ failure. Everybody dies of something, however, usually if the person is at, or past their normal life expectancy, whatever they die of (except for trauma and some specific non age related diseases) can be attributed to \"old age.\""
] |
[
"Cells in our body are constantly carrying out various functions. These functions are energy intensive, create waste and in general are quite tough on our various organs. On top of this, we are constantly getting external damage from the environment: UV light, toxic material, bacteria and other microorganisms. ",
"This results in our body's cells, the cellular proteins and DNA getting damaged. We have evolved various ways to overcome this: we replicate cells in our various organs, we can recycle and reproduce damaged proteins, we can repair and replicate DNA etc... But as with any system, those repair mechanisms are imperfect. Sometimes the cell is overcome by damage before it can be replaced, sometimes the repair attempt is imperfect. This is often exacerbated by things like smoking, diet, exposure to harmful chemicals.",
"Over time, your body accrues damage it is not able to repair. The stem cells which are used as the basis (a template if you will) for various cell types in your body also age, and become less effective at replacing your body tissues. This is what we refer to as ",
". Everything, slowly but surely, getting worse over time.",
"We understand that ageing is natural process, but it is not inherently part of our biology but rather something we have yet not been able to overcome. ",
"In general when we say that someone dies of old age, we mean they died from something you would expect to kill an old person that you may not in any way be able to 'cure'. Specifically, when someone dies from failure attributed to this build up of damage, or an acute insult such as a drug given to them to treat another condition damaging their liver, or kidneys, or heart. Older people often have chronic conditions - meaning they are conditions that may not outright kill them, but they can also not be cured. These conditions can often get worse over time despite treatment and, again, death from succumbing to such a condition such as chronic heart disease, chronic obstructive lung disease would be considered old age-related.",
"However, as ",
"/u/andyblu",
" said, old age is not a medical diagnosis. Doctors may use that term when explaining things to family, the patient etc, but generally for medical purposes, a medical doctor would be more specific when describing cause of death."
] |
[
"How does age make our organ's fail?"
] |
[
"Are there any documented cases of evolution where there has been speciation?"
] |
[
false
] |
I have a religious but otherwise very reasonable friend and I have finally piqued her curiosity with evolution, specially since she is studying medicine and we have been discussing the pharyngula stage, vestigial features, etc. The thing is she says she accepts microevolution, but she does not believe two species can come from the same ancestor (it's the old "it's not evolution, it's adaptation"). I looked around but couldn't find any. Any ideas? Thanks! Edit: Thank you very much for your responses! I will read these myself and share it with some other friends, as well. AskScience Rocks!
|
[
"Well, I was going to post a giant list, but it was over the word limit... so start here:",
"http://www.scienceforums.net/topic/13511-observed-speciation/"
] |
[
"Ring species",
" are great examples of speciation in progress ",
".",
"Wikipedia: Speciation",
" also gives examples of observed speciation."
] |
[
"This is one of the more famous ones ",
"(Lenski)"
] |
[
"What color are the eyes of an albino person?"
] |
[
false
] |
The iris, pupil and sclera, please. I'm doing a and the internet confuses me as to what color I should do the eyes.
|
[
"Usually it is pale blue, though this may vary as a function of the type of albinism. ",
"The Wikipedia article on albinism",
" has some more info."
] |
[
"Here's an example image",
".",
"The sclera should still be white.",
"The iris of an albino person has an extremely low melanin content. In normal lighting conditions, this results in a pale blue or gray color. However, if the light is bright enough, such as in bright sunlight or a flash photo, you get the red-eye effect shown in the image. This is similar to but more intense than the common red-eye effect for normal people in flash photos: you are seeing the blood vessels in the eye illuminated off the reflective retina. In albino people, there is so little melanin in the iris that it cannot block all the incoming light - it is translucent. As a result, the red-eye effect extends across the iris as well as the pupil."
] |
[
"Yes I've gathered that I just needed to know a more specific description that focuses on the eyes only. Though someone helped me out I appreciate the fact you took the time to answer! Thanks :)"
] |
[
"How does gum disease have any bearing on the heart?"
] |
[
false
] |
Why am I increasingly seeing articles saying that if I don't keep my gums healthy, I might be susceptible to heart diseases?
|
[
"To sum up the last few decades of research, what was found was a certain group of ",
" called ",
" could be cultured from the valves and myocardium of patients with endocarditis, which is an infection of the interior surface and valves of the heart. Interestingly enough, these were identical to some of the ",
" that live in the mouth and cause gingival disease. Further evidence suggests that patients who have gingivitis have higher than baseline risk for endocarditis. ",
"So the thinking is that ",
" introduced into systemic circulation by increased permeability of inflamed tissue in the gums during gingivitis allows for higher than baseline probability for the bacteria to seed into the system. Coupled with people who may have valvular disease or artificial valves (which provides an excellent place for the ",
" to colonize and form \"vegetations\"), the new guidelines are pointing towards oral health as a way to maintain cardiac health."
] |
[
"It is also theorised that long term inflammation can worsen atherosclerosis and promote blood clotting which can contribute to the more common types of heart and vascular disease. "
] |
[
"Infection in one's gums can enter the blood stream and travel to their heart infecting the heart valves."
] |
[
"What do muscle knots actually look like?"
] |
[
false
] |
I have always wondered what the muscle actually looks like when you have a "knot". I'm aware they are contractions in muscles, but it's not the whole muscle contracting (right?), so what does it really look like?
|
[
"http://www.t-nation.com/img/photos/06-150-training/image009.png",
"This is similar to a picture out of a physiology book that I had in massage school. "
] |
[
"Here's a larger image in colour: ",
"link"
] |
[
"yes the term \"toxin\" is terrible, but in an area of muscle that is in constant contraction (or stuck closed {see full response below}) there is reduced blood flow. thereby the chemical bath at the site is stagnant. ",
"prostaglandins and histamines (and the rest of the compounds the regulate emigration of neutrophils) cant do their work well in that situation and become irritants. \ncellular by-products cant be removed from the site and become an irritant.\nBroken cells or cellular debris from micro tearing are also stuck at the site.\nThus the lay term is 'toxins' ",
"if a car crashes into you house you would call the broken pieces \"trash/junk\" even though categorically it is all the same stuff that was once a wall."
] |
[
"Would it be possible to create a synthetic agent to replace our Myelin Sheaths?"
] |
[
false
] |
I've been wondering about this for a while. Since it appears that our Myelin Sheaths are the source of numerous complications yet crucial to our survival, would it be possible to create a synthetic agent that performs the essential functions we require while avoiding generally negative effects? I'm quite sure that the answer to this isn't an encouraging one, but if such an undertaking was possible, we could circumvent a lot of the factors that prevent Neurogenesis of the CNS, and certain Diseases - such as MS, Myelitis, or Polyneuropathy - could be confronted in a new way.
|
[
"Purely synthetic? Most likely not as the scale and \"installation\" process would be major hurdles. Bio-synthetic? Maybe. The myelination process involves two types of glial cells. One of them takes care of the peripheral system, the other the central system. Producing, maintaining, and adapting myelin is an active, not passive, process. It has to adapt to changing neuronal function and is not a stagnant \"object\" in the brain. Therefore a synthetically derived material that can keep up with all that is very unlikely. It might, however, be possible to engineer a biosynthetic organism that mimics the functions of these glial cells in some ways that could be beneficial in certain disease states.",
"Edit: I should mention that bio-synthetic myelin has been attempted in the past, with little success. I was able to find a few more recent articles that seem to still be running into hurdles, for example ",
"this paper",
" shows how they overcame one problem with thermodynamic instability. Looks like it's still being worked on; keep your fingers crossed!"
] |
[
"This is only complicated by the fact that myelin sheaths are not continuous along the length of the axon - it's actually a bunch of sheaths separated by small gaps. These gaps are necessary to keep the action potential traveling down the neuron.",
"Because of this, a completely synthetic myelin analogue would require Dr. Manhattan levels of molecular control to properly apply. Stimulating natural myelin synthesis instead, as per Brain_Doc82's comment, is much more likely."
] |
[
"Whilst studying glioblastoma multiforme in my last job, I seem to recall reading that the myelin sheaths do more than just insulate the neurons - they also provide other support functions for the otherwise encased nerves. ",
"That's been a while though"
] |
[
"How strong would a vacuum's suction need to be to start pulling hair off of a Person?"
] |
[
false
] |
[deleted]
|
[
"One thing that you must understand is that there is no actual \"suction\" from a vacuum. What you are experience is the PUSH of the air trying to get into where the vacuum is. So even if your whole body was in a vacuum, you wouldn't pull the hair off anything."
] |
[
"Somehow I find this relevant:",
"http://www.youtube.com/watch?v=ORalNaAokYA",
"But seriously, I'd imagine it'd have to be something at least industrial strength."
] |
[
"Vacuum is a vacuum. There is nothing in a vacuum so you can't make it a stronger vacuum by making it have less stuff, because there is nothing to take away. Because there is nothing at all in a vacuum, then there isn't anything in there that would be doing the sucking either. It's the non-vacuum that does the pushing. Normal air does this pushing all the time in all directions, it's called the air pressure. But because it's surrounded by more normal air, this air pressure doesn't have much effect on most things. But if you suddenly take away the normal air, that is, create a vacuum, then the surrounding normal air is going to rush into the vacuum since there's nothing to stop it there.",
"Someone's head, or hair, isn't going to do this pushing like air is. We don't talk about hair pressure or things like that after all, because there isn't any. The air that surrounds the head and hair would rush into the vacuum, and in doing so create a pretty good wind around the head. That wind may or may not be able to pull some hair off. Probably really only hair that's loose already."
] |
[
"How old can a tree get in a perfect environment?"
] |
[
false
] |
If there are thousand year old trees in non- perfect conditions how old can a tree get if it gets everything it needs to live,
|
[
"Tree age is limited more by the stability of their telomeres. As plants age, the telomeric caps that stabilize the ends of their DNA will inevitably degrade, causing DNA damage.",
"Another factor with negative effects on plants aging indefinitely is DNA damage itself. A classic cause of this is UV damage from the sun.",
"Ultimately, plant age is mostly genetic. Certain trees are short-lived no matter what, while others are able to survive thousands of years, like redwoods or certain pine species (like Methuselah)."
] |
[
"Assuming you mean they keep growing:\nTheoretically you would reach a point when the tree needs so much water (more so than evapotranspiration can provide) that the tree would stop growing and then stabilise staying at that point indefinitely.\nAssuming you mean that it grows to a certain point and then stops, it could age indefinitely"
] |
[
"One of the things that makes plants so special is the fact they can be polyploidy (they have more than the two sets of alleles), which is usually fatal/causes serious mental difficulties in humans. Another is the fact that when they grow they grow a stable structure (has you tried flexing a thick tree branch) as opposed to a fluid structure in animals in turn due to the structurally stable cellulose cell wall."
] |
[
"Is a sperm getting to the egg first actually a result of it carrying better genes than slower sperm?"
] |
[
false
] |
From a layman point of view, the quality of the genetic material being carried seems as though it would have little effect on the sperms ability to move. Exactly how much if at all does the cargo affect the vessel?
|
[
"One of the big things is that it's not only speed, but luck as well. The fastest sperm may go the wrong direction, may not be able to penetrate the egg before another sperm does, or just plain old not survive the trip. Speed may help the sperm, but it isn't the deciding factor."
] |
[
"Thanks for this very scientific answer."
] |
[
"Thanks for this very scientific answer."
] |
[
"How physically damaging(if at all) is our increasing dependance on wireless technologies?"
] |
[
false
] | null |
[
"In terms of the internet, specifically things like google, our brains are actually evolving in such a way as to crave \"instant gratification\" (finding the answer to your question via google instantly), and we are less capable of spending time reading through large articles. This also affects our writing abilities, as now-a-days our ability to write often comes in short bursts rather than being able to write down many thoughts at a time and link them all together. For example, when writing an essay, most people these days will write one paragraph, take a break to surf the net( reddit of course ), then will go back and write the next paragraph, resulting in a break from their train of thought. Hope this helps!"
] |
[
"There are two kinds of radiation. Non-ionizing and ionizing radiation. Ionizing radiation is dangerous, because it has the ability to destroy molecules(e.g. DNA) in your body. This is what causes cancer in people who has been exposed to radioactivity(nukes, power plant failures or medical device failures, and so on). Sun burns fall into this category. ",
"The other kind is non-ionizing. It doesn't do anything in itself, but the amount of radiation you receive can be dangerous. For instance, radio waves are not dangerous, unless you are standing 1 meter from the transmitter. And even then, it is the power of the transmitter that decides how dangerous it is. For instance, when a repair guy climbs to the top of a broadcasting tower, they shut down the transmitter when he is maybe 1/3 to the top. But that is because the transmitter has a power of maybe 1 Megawatt, and not the power of your mobile phone/wifi router and so on. ",
"There is a very extensive Wikipedia article on the possibility of damages from mobile phones here: ",
"http://en.wikipedia.org/wiki/Mobile_phone_radiation_and_health",
"As you can see from this, there is is little to no conclusion that mobile phones are dangerous, and whatever warnings there are, are of a precautionary nature. "
] |
[
"First thing, \"radiation\" is essential to our lives; the most common form we think and talk about is light. Light and wireless signals are the exact same physical phenomenon, except that each has different wavelengths. ",
"However, that's not to say that some forms of electromagnetic radiation might not be harmful (just like how sound can be unharmful (like from a TV) or harmful (like the noise level of gunfire). ",
"With electromagnetic radiation, the damage is known to occur in two ways: heat and ionizing radiation. Heat is pretty self-explanatory; when electromag radiation hits objects, it can get absorbed and transfer their energy to heat that object up (a la the sun). Ionizing radiation is actually a similar principle, except here a molecule absorbs the radiation, then instead of heating up, it breaks. If this happens to molecules like DNA, then bad stuff can start to happen.",
"As you may have figured out, whether it does either of those largely depends on the energy level of the electromag radiation (otherwise known as photons). Radio waves (the same kind of waves emitted from wireless signals) are lower energy than visible light, so it can't really do ionizing radiation (you start getting ionizing radiation at ultraviolet light, which is the just a bit higher energy than visible light, and is the reason you should where skinblock outside).",
"However, there are still other ",
" ways for photons to hurt you, we just haven't established whether or not any of these methods actually do anything."
] |
[
"Why does the hair on our body seem to stop at a certain length while the hair on our heads grow continuously?"
] |
[
false
] | null |
[
"All hair grows for a certain amount of time, stops for a period, then falls out. The cycle repeats. Changing the amount of grow and dormant times gives you the difference between scalp hair and arm hair. This basically gives all hair a maximum length and the hair that remains a constant length has a short enough growth period to show you that average length. That and the fact that you don't cut it."
] |
[
"Head hair has a max length as well. Some people just can't grow hair past their shoulders. Some can grow it three yards long. Even though there's a big range it does taper off eventually. "
] |
[
"This is true, but this also raises the question, why does the hair on different parts of our body fall out at different times? And regardless of race or gender, why it that only the hairs on our head get the longest growth period before falling out?"
] |
[
"Does blowing on your food actually make it cool down quicker?"
] |
[
false
] | null |
[
"You're moving the heat away from the food faster than it would normally would, so yes."
] |
[
"The air you exhale is still colder than the food, and you're also pushing the colder air from the environment over it as well. Food cools down by transferring its heat to the air around it. The greater the difference between the temperature of the air and the temperature of the food, the faster this heat is transferred.",
"By blowing, you are doing two things. First, you are removing the hot air in immediate contact with the food and replacing it with cold air, increasing the rate at which the food can transfer its heat to the air. Second, you are creating a current which makes it so that there will be more contacts between cold air particles and warm food particles per second than if the air were stagnant, which also allows for faster transfer of heat from the food to the air."
] |
[
"Great answer! Thank you! "
] |
[
"What do the scientists/physicists expect to find when they ramp up the energy of the LHC to 13 TeV?"
] |
[
false
] |
I assume it is new particles that are not part of our current Standard Model?
|
[
"A very interesting question, bmp91. ",
"There are several topics that scientists are trying to clear up by means of the LHC. \nI'll list a couple.",
"By increasing the energy of the accelerator, scientists are hoping to come close (though how close that's up to some debate) to the amount of energy that was around soon after the Big Bang. In the ",
"moments following the Big Bang",
", the Universe was so energetic and hot that the current laws of physics break down. So there's essentially a whole field to discover there. \nSome are suggesting that the sort of energies that the LHC can achieve might trigger the formation of mini-black holes, which would then collapse back onto themselves because of their tiny size.",
"As you mentioned, particle physicists currently have discovered a bunch of particles that make up the Standard Model; with the discovery of the Higgs boson, the Standard Model is believed to be complete.\nHowever, there are indications that another set of corresponding particles should exist. ",
"This extra model is called 'super-symmetric' (or SUSY)",
" as its particles would have the same charge and mass as the corresponding standard model particles, but spin differing by 1/2.\nFor instance, the equivalent of the electron would be the 'selectron' (for the name of the super-symmetric particle, you usually just add an 's' in front of the standard model particle name), would have the same mass and charge as the electron, but it would be a boson (integer spin) rather than a fermion (half-integer spin)\nBut as the electron and the selectron ought to have the same mass, they should be equally easy to find. However, none of these supersymmetric particles have yet been found; it is then believed that the super-symmetry was somehow 'broken' during the evolution of the Universe, causing the masses of the supersymmetric particles to be much larger than the standard model counterparts. The reason for this is unknown.\nThe LHC experiment might therefore finally discover some of the super-symmetric particles. Should it not, it would make the theory shakier still. "
] |
[
"There are absolutely no indications that SUSY particles should exist. It is just aesthetically pleasing to some.",
"The chance of the LHC producing any mini-black-holes is basically zero. There is no indication that general relativity should break down at the ~10 TeV scale. Much MUCH more energetic particles hit the Earth all the time (cosmic rays).",
"The main reasons to continue running the LHC at higher energies is because the main cost in the LHC is building the thing and it can do higher energies. It was built like that because we didn't know when we'd find the Higgs. There is a chance that it'll find something and a chance that it won't.",
"What we might hope to find is a dark matter candidate and/or a susy particle. As far as I am aware there is no particular reason why either should be found at these energies but equally no reason why not (that is given that they haven't been found at 7 TeV, at that point SUSY makes as much sense to show up anywhere or nowhere).",
"related: ",
"http://smbc-comics.com/index.php?id=2088"
] |
[
"The presence of a supersymmetric model would solve theoretical issues regarding the value of the Higgs boson's mass, it makes the problem of quantum field theory easier to analyse and is necessary for the string theory (which of course it's not proven itself)."
] |
[
"Steel rod to mars vs the speed of light?"
] |
[
false
] |
Hi, I remember reading this passage in the "Feynman Lectures", where Dr. Feynman describes an experiment in which a theoretical metal rod of length equal to the distance between mars and earth is arranged between mars and earth. Then the "rod handler" on earth gives the rod a push upwards. So the question posed is, will the rod instantaneously move backwards on Mars? He then proceeds to say that actually the movement will be felt roughly after the time it would take for sound to propagate from earth to mars i.e. at the speed of sound. This is because the atoms in the rod actually propagate their position at the speed of sound. My question is, if this were true, how is supersonic travel possible? won't there be a scenario where the atoms in the components of the aircraft won't "catch up" because the propagation of the new positions is slower than the actual speed? Won't the aircraft disintegrate?
|
[
"The super-sonic aircraft is an example of (nearly) ",
"rigid-body motion",
". Note that this page says:",
"Even though such an [prefectly rigid] object cannot physically exist due to relativity, objects can normally be assumed to be perfectly rigid if they are not moving near the speed of light.",
"Which maybe behind the point Feynman is trying to make.",
"If the thrust of the engines of an aircraft were to suddenly increase then they would exert a \"jerk\" on the airframe and the response to that jerk would pass through the airframe at about the speed of sound ",
". As an example ",
"Concorde",
" is about 62 m long, ",
"the speed of sound in aluminium",
" is about 5100 m/s so that impulse could pass from one end of the aircraft to the other in about 62/5100 = 12.2 ms. ",
"If the engines were somehow to go form 0 thrust to maximum thrust (676 kN) in less than 13 ms the aircraft would indeed disintegrate!",
" missed a link, corrected calculation."
] |
[
"My question is, if this were true, how is supersonic travel possible? won't there be a scenario where the atoms in the components of the aircraft won't \"catch up\" because the propagation of the new positions is slower than the actual speed? Won't the aircraft disintegrate?",
"You're mixing up reference frames here - or rather, what the \"supersonic\" part is relative to.",
"When you push on a rod, the pressure wave travels down the rod at the speed of sound of the material that makes up the rod. When a plane is supersonic, ",
" is travelling through the air faster than the speed of sound ",
". It is not some part of the plane travelling at supersonic speeds relative to other parts of the plane.",
"The two are not comparable."
] |
[
"5100/62 = 822.6 ms. ",
"Your computation is completely off.",
"62m / 5100ms",
" = 0.012 s "
] |
[
"Do deaf people with dyslexia have a hard time understanding sign language?"
] |
[
false
] |
Sign language involves interpreting language using visual interpretation, so would dyslexia make that difficult? Or does sign language go through a different path in the brain? PS not sure which flair is most suitable - sorry if it's a bad choice!
|
[
"Sign language makes sense if you reverse the image like a mirror. ",
"",
"I'm not too familiar with neurolinguistics, but I believe signed language is processed through the same area as spoken language (Broca's area). I'm not sure where dyslexia occurs in the brain."
] |
[
"Aren't there some signs that are identical except for which hand is used?"
] |
[
"No, at least not in ASL or a few other sign languages I know. Right-handed people sign opposite of left-handed people, so the signs are not easily confused. The only time this changes is when the signer is indicating something on their left or right, this would be the same for every person signing in that direction. "
] |
[
"Before modern dental hygiene, did everyone have terrible breath all the time, or do our mouths stay pretty clean when not eating so many refined carbs?"
] |
[
false
] | null |
[
"Dental Hygienist here: Refined sugar has more to do with caries (cavities) than bad breath. Interestingly enough, caries used to be a disease of the wealthy because they were the only ones who could afford refined sugars, but now it is seen more in the poor because of poor education and it is cheap.",
"\nPeople probably did have bad breath because of calculus (tartar) buildup on the teeth and on the tongue. ",
"Here",
" is a picture of a jawbone from many hundred years ago with dental calculus and periodontal disease. My guess is breath was affected by diet (think onions and garlic)."
] |
[
"Cultural anthropologist here:\nPeople have been using things to clean their teeth for much of human history. Two things that were prevalent all over the world were cloth and sticks. Tooth cloths and tooth powder have been used in Europe for hundreds of years (possibly longer, but cloth rots and doesn't turn up in digs). ",
"Bankes' Herbal, 1525 [English]\n\"Also take the timber thereof [rosemary] and burn it to coals and make powder thereof and put it into a linen cloth and rub thy teeth therewith, and if there be any worms therein, it shall slay them and keep thy teeth from all evils.\"",
"Rosemary does have antibacterial properties so I suppose they were onto something there!"
] |
[
"The interesting thing to consider, in this case, is whether the OP means bad breath or bad teeth. The two are certainly linked, but not until the advanced stages of gingivitis or ANUG.",
"If we're talking bad breath, then onions and Garlic were peasant foods. Meats (for peasants) were a delicacy and eaten very rarely. The interesting thing that my history of food professor told me is that, despite the severe grinding that the peasant's teeth were subjected to during the middle ages (from unrefined flour and additives like rock dust), they actually had less dental caries. This could be a result of the fact that they ate far less refined foods and (ironically) far more peasant foods like garlic (antimicrobial) and unrefined bread (scrubbing effect).",
"If we're talking bad teeth though, everyone had them. Grinding of teeth was significant due to the use of rock mills for grain and brushing was extremely uncommon. Interestingly, the first humans (Homo Sapiens and Neanderthals and the like) were not only taller than your average human from greek or roman times but also had better teeth due, in large part, to their meat-heavy diet.",
"Just an interesting aside regarding health and nutrition: Rameses II, who was supposedly ",
"very tall for his time",
" (that's an awful link, but I don't want to just speculate, my professor told us this) was only 5'8\", and was most certainly one of the people with the best access to nutrition. "
] |
[
"Did cocoa trees, coffee plants, and tea plants all evolve the production of caffeine independently, or do they share a common ancestor that made caffeine?"
] |
[
false
] |
Also, are there many other plants that produce caffeine that may not be edible or that are less common?
|
[
"They evolved caffeine production independently. This is an example of convergent evolution, whereby different species develop similar characteristics independently. The caffeine sources even vary--seeds, leaves, etc. The chemical structure of caffeine isn't the most complex.",
"http://sierram.web.unc.edu/files/2011/04/cafmol.png",
"Article:",
"http://public.wsu.edu/~lange-m/Documnets/Teaching2011/Pichersky2011.pdf"
] |
[
"As elsjaako pointed out above, both ",
" and ",
" share a common ancestor in a monophyletic group. It would seem more likely that their ability to produce caffeine enzymatically is an example of parallel evolution, not convergent. It is likely their common ancestor produced xanthosine or xanthine (purine derivatives), and descendants acquired the same enzymatic mutations to create caffeine in this pathway. ",
"Edit: As an example, ",
" parallel evolution can be seen in the evolution of the eye in ",
" octopuses and ",
" nautiluses, and convergent evolution can be seen in the evolution of flight in bats and birds. It's very easy to confuse parallel and convergent evolution."
] |
[
"This is likely the most correct answer. To corroborate your point I ran a sequence alignment on the caffeine synthase of black tea (Camellia sinensis) and coffee (Coffea arabica). The proteins are clearly homologs, with a 37% identity match along amino acid sequence (55% similarity when using BLOSUM62 and default penalties on a global alignment). ",
"If the proteins are that closely related it hardly seems fitting to call it convergent evolution. As you said, they likely independently mutated from conserved proteins involved in purine derivative synthesis. If one were to run a profile search using a ",
"protein involved in caffeine metabolism",
", they would find a variety of such enzymes in their ",
"page of results",
". ",
"Notice that the listed enzymes come from a variety of organisms, not just the caffeine producers we are interested in. Also notice that both of the previously mentioned caffeine synthases (and the respective gene-product duplicates) are in our page of results. ",
"Note: plant biology is not my area of expertise and I am not a panelist.",
"Edit: It would be great if a panelist could chime in."
] |
[
"Why is there a positive correlation between population density and the murder rate?"
] |
[
false
] |
I posed this question before in AskSocialScience. Curious to see what sort of answers I'll get here.
|
[
"Other factors play into this: Per Capita income, racial percentages, gun laws, guns per capita, and other variables that need to be controlled in a model for this. ",
"Personalities clash, resources become scarce, relationships are complex. People, like most animals respective to their species, are not happy pent up with thousands of other people per square kilometer.",
"I believe that people are not happy with the lack of economical freedom (related to the scarce resources) and feel trapped in a town, in a cycle, in a job."
] |
[
"It seems obvious to me: the greater the population density, the more people you interact with over time. Each such interaction has a non-zero ",
" of leading to you becoming the victim or perpetrator of murder. Too-frequent interactions may increase that chance, as each interaction is a potential source of stress."
] |
[
"This is a good question! To work out the answer though, first we need to understand why people murder in the first place. Different countries will have different statistics (which indicates how closely tied these questions are with cultural practices), but in a western country, many murders are committed as a result of ongoing domestic violence, in the pursuit of money, or out of hatred/revenge/intense emotion. ",
"A side effect of population density increasing (especially rapidly), is that there is less access to quality education and health care ie higher poverty indicators. These indicators mean people have less to lose and also have few options or ways to deal with their problems. When someone is planning a homicide, their feeling that there is no other option, coupled with access to deadly weapon can lead them to murder. The reigons with the highest murder rate are also the reigons with the higher poverty indicators.",
"Hope this helps!",
"Ray"
] |
[
"Is there any matter inside a black hole?"
] |
[
false
] |
I know that as things head into a black hole, spaghettification occurs. I know these tidal forces are enough to tear the bonds between atoms. And, to the best of my knowledge, since the gravity is practically infinite, I assume it is enough to tear apart the bonds within the atoms as well leaving only the fundamental particles. So, assuming I haven't made a mistake yet, would these fundamental particles be 'torn' apart as well? I'm not sure how they would be torn apart... maybe converted into pure energy? What would this 'energy' manifest as? : Thought of a follow up. I've read that black holes preserve information. If my presumption is true, how would the information survive and be reconstituted in any plausible sense?
|
[
"how would the information survive",
"When particles fall into a black hole they cause deformations/oscillations of the event horizon surface. So the information about them is not lost in a sense that it will be able to affect outgoing particles (Hawking radiation), for example. "
] |
[
"It depends how you define \"matter\". If by \"matter\" you mean anything that has rest mass, then the answer is yes: but you wouldn't say that the black hole ",
" matter, rather that it ",
" a type of matter.",
"A more restrictive definition would be to insist that matter has to be something made of fermions. In that case the answer is no, as the pressure is high enough to overwhelm pretty much any and every exclusion principle, and fundamental particles will break down."
] |
[
"Black holes are superdense collections of matter."
] |
[
"What will happen here on earth when Betelgeuse goes supernova?"
] |
[
false
] | null |
[
"It'll be about the same relative size as the moon",
"I don't know what you mean by this. The brightness would be the same. You can determine the brightness from the distance modulus. I couldn't grab the absolute magnitude of a Type-II, but for a Type-Ia it is about -19. At a distance of 200pc, this would be an apparent magnitude of -12.5. That's about the brightness of the Moon.",
"With a decay rate of about 3 magnitudes per year, so 4 years to get to the brightness of Vega."
] |
[
"Its too far away to have much of an effect on Earth. We will be able to see it clearly night or day as it is already an extremely luminescent star. Damage wise gamma rays will be sent out but because of its axis, we won't get hit by the intense gamma ray burst."
] |
[
"My thoughts exactly."
] |
[
"Why are the blades on hole punches a concave shape?"
] |
[
false
] | null |
[
"A blunt tip doesn't punch effectively, especially for multiple sheets. A convex tip punches ragged holes and doesn't remove the material, just pushes it aside. A concave point reliably cuts the material away neatly, and also provides a thinner \"edge,\" making it easier to punch multiple pages at once."
] |
[
"a sharp object can hurt you and a blunt object can't",
"Are you volunteering to test the latter hypothesis? I can help you."
] |
[
"The same reason for why a sharp object can hurt you and a blunt object can't. The pointy part of the concave blades will provide the power to puncture the thick layer of paper. Cutting the rest of the paper is easy work after that. "
] |
[
"Where do atoms get their energy from? Or more specifically, why do they seem to have an infinite amount of energy?"
] |
[
false
] |
So I've understood since I was young that atoms are always moving, and the speed at which they move determines their state (solid, liquid, gas). What I never even thought to ask was how the atoms kept moving! So if you have a solid object, let's say a bouncy ball, and the ball is comprised of constantly moving or vibrating atoms, where does this energy come from? And why doesn't an atom's energy ever run out? If you throw a bouncy ball, every time it bounces it transfers some of its energy to the surface it comes in contact with, eventually losing the required amount of energy to continue bouncing. So why do atoms bounce around at a constant and infinite pace?
|
[
"Well, the reason a bouncy ball stops moving after some time is, that is loses energy to its surroundings; mostly in the form of heat.",
"On a microscopic scale, however, heat ",
" the movement of atoms. Thus Atoms cannot lose energy to their surroundings, except by transferring it to other atoms (or emitting it in some other way, but let's neglect that for our purpose).",
"Hence, a system of atoms will never stop moving, because the kinetic energy is constantly transferred from one atom to another through collisions, but is never lost."
] |
[
"No, tiny balls which are bouncing around randomly are already at their most disorganized state, so you can't \"disorder\" them any further. You can only increase or decrease their average velocity (heat it up or cool it down).",
"Entropy increases when you decrease or remove differences in energy. To stay with the the ball analogy, mix a box of very fast moving (hot) balls with a box of very slow moving (cold) balls and you end up with a two boxes of mixed balls whose average speed is mediocre. By removing the difference between the boxes you have just increased the entropy of the system."
] |
[
"Exactly. One important distinction between heat and macroscopic movement though is that heat is random motion whereas macroscopic movement is ordered (everything is moving together). Because many more disordered states exist when compared to ordered states, you can expect that over time ordered motion (like a bouncy ball moving) will slowly disipate to non-ordered motion (heat). Macroscopically this appears like objects tending towards rest (kinetic energy is turned into thermal energy whenever lossees are present)."
] |
[
"Do People who fast regularly have lower risk of diabetes ?"
] |
[
false
] |
People who fast regularly like religious people have a lower risk of being diabetic, is that true? Being at a high risk of diabetes I'm trying to avoid as much risks as I can and i dont mind fasting but my mom wanted to know more about it so can someone please let me know.. Thank you
|
[
"Yes, it lowers the risk of type II Diabetes. ",
"Type II diabetes is caused by ",
"insulin resistance",
". Insulin is a hormone that makes cells take in sugar from the blood. Insulin resistance means that the same amount of insulin will now lead to a reduced uptake of sugar from the blood. At first this is not a problem, the pancreas will just release more insulin and the blood sugar eventually normalizes, someone at this point is considered “prediabetic”, they do not have the negative health effects of high blood sugar yet but at some point the additional insulin will not be enough. When this happens they have progressed to type II diabetes. No matter what the pancreas does the cells wont take up enough sugar leading to high blood sugar which is really bad for your health (increased risk of infection, heart disease, cancer, etc.). ",
"By lowering the amount of sugar in the blood you can reduce the amount of insulin needed and over time insulin resistance will wane. This can be achieved by caloric restriction (a diet) but also through intermittent fasting. However, fasting is a higher risk and less proven strategy, you should not try to fast for prolonged periods of time and you should be aware of the risk of passing out while fasting. A safer approach is probably to eat a normal 3 meals but eat less at each one, and cut back on simple sugars. Exercise is also extremely important for reducing insulin resistance. When you exercise your muscle cells burn internal energy stores and replenish them with sugar from the blood. They become more sensitive to insulin and more willing to take in sugar.",
"It is best to consult a doctor or nutritionist before trying anything radical."
] |
[
"Does genetic predisposition towards developing type II diabetes confer any survival advantage in parts of the world where starvation is rife? I notice there appears to be a strong correlation between the prevalence of type II diabetes and such countries.",
"If starvation strikes, are you more or less likely to survive if your body is more disposed to reducing the uptake of glucose?"
] |
[
"There have bin several theorys why people become Typ2 diabetic form: to much calories, to cells are overfiled by constant glucose exposure, to desensitisation of the insulin receptors by constant insulin exposure.",
"in theory people that fast will have lower caloric intake, burn the glucose in the cells and reduce the constant insulin signaling which will keep insulin sensetivety high.",
"also there are several low carb, keto, lchf diets that have shown to reverse typ2 diabetes",
"(blood sugar and HbA1c in normal ranges without medication)",
"https://www.carbmanager.com/article/xybzfheaacyasz8g/can-type-2-diabetes-be-reversed-with-keto/",
"https://www.diabetes.co.uk/news/2020/nov/low-carbohydrate-diet-can-help-over-50s-to-control-type-2-diabetes.html"
] |
[
"Is the moon really going to escape our view/orbit after a long enough period of time?"
] |
[
false
] |
If so, what are going to be the effects on earth's tide? or other impacts?
|
[
"Correct. As with many things, the real universe comes along and ruins the theoretical scenario."
] |
[
"Yes. Tides will diminish. It's possible that the core will cool and the that will cause the magnetosphere to shut down and stop protecting the earth from the solar winds. Also the moon stabilizes the earth's axis. With the moon gone, seasons would become less predictable and more extreme."
] |
[
"It's important to note three things here.",
"1.) The moon won't escape its orbit completely. The moon is gaining the energy required to move into higher orbits through tidal forces which slow the Earth's rotation. Thus, once Earth is tidally locked to the Moon, the Moon will stop receding from Earth.",
"2.) The time scale for this to happen is enormous: roughly 50 billion years.",
"3.) The Sun will become a red giant and destroy both bodies long before the above scenario can unfold.",
"More info: ",
"http://www.spaceanswers.com/solar-system/will-the-moon-ever-leave-earths-orbit/"
] |
[
"Are OD 6+ goggles strong enough to safely build/play with \"DYI blu-ray laser pointers\"?"
] |
[
false
] | null |
[
"Wolfram alpha is doing that calculation with the base e logarithm, not base 10.",
"Here is the corrected version.",
"Though are you sure that you can get 2 Watts from a 405 nm diode? When I was into lasers, the most that I heard people doing was 500 to 600 mW. Have people found sources of more powerful diodes?"
] |
[
"Optical density of 6 means that the intensity is reduced by a factor of 10",
" This is overkill unless you plan on working with lasers with hundreds or thousands of Watts of power.",
"The optical density that you want depends on the power output of the laser. Usually, you want the goggles to reduce the power to 5 mW or less. You can calculate the minimum OD required with the following formula, od=-log(.005/p) where p is the power output of the laser in watts and log is the base-10 logarithm.",
"You can, of course, purchase those goggles if you wish, just remember that the laser most likely wont be visible with them on."
] |
[
"So I did that and assuming 2W, I got 5.9999 (6+ OD). Did I get something wrong?",
"http://www.wolframalpha.com/input/?i=-log%28.005%2F2%29"
] |
[
"How is feline leukemia contagious but human leukemia isnt?"
] |
[
false
] | null |
[
"It sounds like you're thinking of feline leukemia virus, which is a virus that causes leukemia. As a general rule, cancers including leukemias are not contagious, but if they are caused by a contagious virus, cases of cancer will spread. This is analogous to HPV in humans, which is sexually transmitted and causes cervical cancer. Someone with just cervical cancer won't be able to pass it to someone else, but if their cervical cancer is caused by HPV, they can pass on the HPV, which can lead to cancer in new hosts."
] |
[
"Humans have a version called human T-cell leukemia/lymphoma virus (HTLV) that causes T-cell leukemia and other conditions."
] |
[
"Feline leukemia is caused by a virus so it can be spread like any other virus leukemia in humans is not caused by a virus. The exact cause in humans is not known but is related to genetics and not a virus so It can not be spread."
] |
[
"What is the difference between anti matter and negative matter?"
] |
[
false
] | null |
[
"If by \"negative matter\" you mean \"stuff with negative mass\", we're not sure if such a thing can even exist. Antimatter has positive mass."
] |
[
"Could black holes be made made of negative mass?"
] |
[
"Black holes, as we know them, have positive mass."
] |
[
"For how long can you survive hanging upside down?"
] |
[
false
] | null |
[
"I can't see any way of getting a definitive length of time, unless you actually hung someone upside down and waited for them to die. ",
"Human beings aren't meant to go about their lives upside down, and I believe that eventually, doing so would prove fatal- the heart would be overworked from trying to pump blood up the length of the torso and legs, and the brain and head would be flooded with far more blood than usual. Capillaries in the brain could potentially hemorrhage, which could easily prove fatal. Your feet would succumb to Gangrene before too long, though chances are you would die before that became any sort of fatal issue.",
"It could take 3-5 days, it could take up to several weeks or more. I'm guessing the length of time will vary wildly depending on the age, gender, fitness, etc. of the individual in question, but pinpointing a specific duration is going to be difficult without some sort of empirical study (and I doubt there's a study out there which revolves around suspending a living creature wrong-side-up until it dies, but hey, feel free to prove me wrong)"
] |
[
"I believe that eventually, doing so would prove fatal- the heart would be overworked from trying to pump blood up the length of the torso and legs, ",
"I doubt it. The heart already has to pump that blood up the length of the torso and legs, after all, because the blood has to get from your toes up to your head."
] |
[
"Doesn't the human heart work differently in terms of capacity for blood in than it does for blood out? It might be optimised for bringing deoxygenated blood up from your feet rather than sending oxygenated blood down.",
"Blood goes in, blood goes out never a miscommunication."
] |
[
"Are there any animals that have symbiotic parasites and evolved under the expectation of the parasite's presence?"
] |
[
false
] |
For a hypothetical example, if an animal that used to have a type of skin but a parasite replaces it with better skin so the animal stops growing the skin over generations. Probably not skin specifically but anything in general!
|
[
"Yeah, pretty much all multiple Cellular organizms. It is hypothesized that the mitochondria, during ancient Cellular development, was a bacteria that was engulfed by a cell. The bacteria adapted to its new environment and began being useful to its host. As a result the cell began feeding the bacteria and eventually the bacteria became incorporated into the cells as an organell. ",
"Keep in mind this is a basic explanation."
] |
[
"Mitochondria",
" could be an example. It has been proposed that they were once an energy-stealing parasite that now is a critical part of cellular function. The exact details of the original role of mitochondria isn't certain, though, so it may have been simply symbiosis rather than parasitism. This all happened with single-cell organisms, so we aren't talking about any complicated life forms.",
"Chloroplasts in plants are a similar story, although I've never seen any proposals that they were parasites at any point.",
"Regardless of the case of mitochondria, the situation of mutually beneficial symbionts (mutualism) evolving from parasitic symbionts has been ",
"studied",
", and the mechanism is certainly viable."
] |
[
"Humans are symbiotic with our gut bacteria, but it's a mutualistic symbiosis rather than a parasitic one, as both host and bacteria benefit. Humans get enhanced nutrient extraction, immunity, and ",
"MANY other effects",
", while the bacteria get food and shelter in our intestines. Normally mutualistic gut bacteria can become parasitic sometimes, which can be very unpleasant, but usually your gut microbiome just quietly keeps you running properly. In fact, gut flora ",
"have been shown to affect personality",
", so in a very real sense, your bacteria are partly responsible for keeping you ... you."
] |
[
"At what point in human evolution did we develop a dominant hand? Is this a trait found in other primates as well?"
] |
[
false
] | null |
[
"Scientists (myself included) are still trying to figure this out. The current evidence suggests Neanderthals exhibited handedness and it appears to be roughly the same ratio as most modern humans: ~ 90% right handed. However, hand preference, that is consistently using one hand or the other for a particular behavior, has been found in several of our closest living relatives like chimpanzees and bonobos. But these apes are different from humans because they do not consistently use the same hand across different tasks whereas humans do. In short, it looks like handedness has evolved in the last few million years of our evolution but is likely at least half a million years old."
] |
[
"Most hypotheses associate handedness with either the 1) evolution of bipedalism or 2) increased task complexity (e.g. tool use). Some also elicit language as a selective pressure. There is decent evidence for the first two hypotheses so it’s hard to tell which is better supported. ",
"I should note that there is a slowly emerging consensus on a very old idea that handedness is probably not under direct selection pressure but is rather a byproduct of selection for other traits."
] |
[
"is there any indication as to why we did? i would think that being ambidexterous would give a greater advantage both in hunting and in daily tasks."
] |
[
"Why does depression cause brain atrophy in certain regions?"
] |
[
false
] |
Is it reversible?
|
[
"Why? Lots of reasons. Is it reversible? Partly.",
"The evidence comes mostly from rodent chronic stress models and clinical postmortem studies of depressed subjects, where neuronal atrophy is most notable in the prefrontal cortex (PFC, executive functions and cognition) and the hippocampus (memory, especially spatial memory). The PFC and anterior cingulate cortex of depressed subjects show reductions of dendritic arborisation and spine density, atrophy of neurons, and losses of discrete populations of cells.",
"There is also loss, again in the PFC and cingulate cortex, of non-neuronal cell populations, including astrocytes and oligodendrocytes, which play critical roles in the regulation of synaptic function.",
"Magnetic resonance spectroscopy studies demonstrate decreased GABA levels and GABAergic interneurons in depressed patients, possibly resulting in increased susceptibility to excitotoxic cell death via unregulated glutamate signalling, which could also contribute to damage of other neurons.",
"It is also associated with reduced neurogenesis in brain regions where this continues to takes place in adulthood, such as the hippocampus. In rodents, ablation of neurogenesis increases the susceptibility to stress, so that when animals with reduced neurogenesis are exposed to stress, they display depressive behavior.",
"Antidepressants (SSRIs and SNRIs, EDIT: also tricyclics and MAOIs) increase neurogenesis, and new cell birth is necessary for the behavioral actions of these agents in rodent models. With respect to reversal, antidepressant-induction of cell proliferation has also been reported in the postmortem hippocampus of patients treated with antidepressants at the time of death, demonstrating the potential clinical relevance for induction of neurogenesis for these drugs as well as indicating that some aspects of depression-associated neurodegeneration is reversible with drugs, as well as synaptically stimulating activities, principally physical exercise. ",
"Antidepressants have complex actions on neurotrophic factor and growth factor signalling that contribute to neuronal and synaptic remodelling over long time periods. In the short term, ketamine activates mTOR signaling and synaptic protein synthesis, resulting in increased synaptogenesis and spine formation, and this along with disruption of glutamate signalling via NMDA antagonism is attributed to ketamine's antidepressant effects.",
"Review:\n",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3259683/",
"Depression and neuroplasticity:",
"https://pubmed.ncbi.nlm.nih.gov/17851537/",
"GABA:",
"https://pubmed.ncbi.nlm.nih.gov/17430150/",
"Antidepressants and neurogenesis:",
"https://pubmed.ncbi.nlm.nih.gov/18045159/",
"Ketamine:",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3116441/?report=reader"
] |
[
"So drugs like SSRIs can potentially reverse the brain degeneration induced by depression, right?",
"Can the cognitive decline be naturally reversed as well if the patient gets better by other means (e.g. psychotherapy) with the passage of time? Or is this effect exclussively caused by pharmaceutical treatments?"
] |
[
"They can, and this is proposed as an important part of their long term benefit, but their direct role in increasing monoamine action (serotonin, epinephrine, dopamine) is also obviously crucial.",
"I don't know if psychotherapy/CBT have been proven to reverse it, but they are, in my view, extremely important in managing depression, which after all is not an exclusively biological phenomenon - improving your thoughts, behaviour, reactions and emotions through psychotherapy, CBT, mindfulness etc is arguably more important than trying to address neuronal atrophy, which occurs naturally as a part of ageing in any case."
] |
[
"What food doesn’t come indirectly or directly from soil?"
] |
[
false
] |
The FAO has a statistic that 95% of our food is either indirectly or directly from soil. My lab mate and I are scratching our heads trying to think of foods that don’t come from soil and we thought y’all might have better ideas than us.
|
[
"Anything harvested from the oceans would fall into the 'not directly or indirectly from soil' category."
] |
[
"The major biomass production in the oceans is pelagic and entirely independent of the ocean floor."
] |
[
"Surprisingly, it isn't, I would have thought the same. I suppose that even societies deriving a majority of their protein from seafood still derive the majority of their overall caloric intake from grains.",
"https://www.who.int/nutrition/topics/3_foodconsumption/en/index5.html"
] |
[
"How worried should I be by recent articles about arctic methane?"
] |
[
false
] |
So I've read this recently: I was aware of arctic methane as an issue before now but this article seems to suggest that it's a lot worse than it was expected to be. I'm generally very skeptical about science reporting which declares how astonished researchers are as they tend to be bunk, but I don't have any expertise that would let me judge it in this area. So, how bad is it really, and should we be any more worried now than we were (say) six months ago? Edit for clarity: I'm aware of why arctic methane release is a bad thing. My question is whether the claim that it is currently being released in unexpectedly high volumes is accurate
|
[
"Sorry, but I have to nit pick you . . .",
"Global Warming (aka Climate Change - the more politcally correct term)",
"Yeah, no . . . global warming is the observed phenomenon that the global mean temperature has been increasing over a long period of time. Global climate change is what results from the change of such an important environmental parameter. These two are cause and effect. The reason why global climate change is preferred in political discussion is because it refers to the effects that global warming will produce on humans -- namely that changes in various global, regional, and local processes will lead to changes in how we can use land, grow food, manage water resources, etc.",
"It depends if you believe in global warming or not.",
"Additionally, the scientific evidence for (and consensus regarding) global warming is pretty much indisputable at this point (see the ",
"Oreskes 2004",
" and ",
"Zimmerman 2009",
" for a meta-analysis of the relevant literature and a survey of relevant scientists, respectively) so implying that it is scientifically sound to believe anything contrary to the evidence is simply misleading. What is essentially up for debate is how the increase in global mean temperatures will affect our planet's climates (and thus its peoples).",
"However, the release of methane is just a byproduct of increased warming of our earth. If you have anything to be concerned about, its the shear amount of energy that is required by our ever-growing population which then increases pollution, greenhouse gases, etc",
"It's not just a byproduct, but also a cause of global warming. This is one of many \"positive feedback loops\", which you alluded to in your first paragraph. Both anthropogenic and natural sources of greenhouse gases are extremely (and equally) important because it is their combined effect that causes the total effect we are experiencing. (That is, the total effect is important so thus are its components important.) Besides, these natural sources are what can eventually put us over a \"tipping point\", at which point anthropogenic activity has no potential to reverse the warming trend."
] |
[
"climate change was inevitable",
"Well, yes and no. To some extent, the climate is always changing. The sun is getting incrementally brighter, our orbit changes its eccentricity, obliquity, and precession so gradually that over human lifespans it's unnoticeable, etc. ",
"But the current climate change (i.e. mutlidecadal warming trend and future warming) is not natural, and was not inevitable. Our climate would not have been getting steadily warmer. In fact, two of the three main drivers of orbital forcing had been cooling us off since the mid-Holocene, at least in terms of the high latitude NH. Our alternative present would look a good deal like the preindustrial climate. And there is no technological reason why we have to continue to force warming, although some amount of change has already been affected and an additional amount is \"in the pipeline\" (i.e. stored as energy in the ocean) and being masked by aerosol pollution. ",
"methane is speeding up the process. The problem is, with that change occuring at an increasing rate, we'll see more dramatic changes... correct? ",
"Yes, but it's more that methane is is coming on top of our CO2 increase, which is the primary concern, due to its immense atmospheric residency and the amount we're capable of increasing it due to fossil fuel use and other activities. Methane is more fuel on the fire, but we are still capable of largely determining the size of that fire due to our choices in the near future and beyond. One of the things that really drives me crazy is that there seems to be very little public awareness- once people have gotten past the \"it's not happening/it's not us\" denial- that we still have an enormous amount of say in what happens next.",
"A gradual change would allow for us (and other species) to adapt... while a more abrupt change suggests we'll see some of the worst case-scenarios I'm sure we've all read: a large chunk of the human population dying off.",
"I don't think we'll end up being so reckless as to not reign in greenhouse emissions. If we don't, then certainly the we'd all better hope that warming is more gradual than we think we have constrained it to be via observational, modeling, and paleoclimatic evidence. ",
"In terms of human die off, I don't think we're in a position to really make any sort of projections. There is too much we don't know about our technological capabilities in terms of adaptation and our political will to respond. Hypothetically, we could offset a good deal of warming with sulfate aerosol geoengineering, but that comes with a host of drawbacks (e.g. does little about ocean acidification), and the idea that we could come up with a global agreement of who gets to set the thermostat and gets trusted with the power that goes with that but we can't come up with an agreement to simply stabilize emissions seems a little far fetched. ",
"Certainly with the biosphere in the state it's currently in, we can expect more extinctions of species if we force a climatic change that is basically unprecedented for ecosystems adapted to Holocene climates and at best used to tens of thousand year timescales for significant global climatic change. ",
"And yes, adaptation would be easier in response to slower changes, but there's a danger in assuming that changes will be linear. For things like sea level rise, they almost certainly will not, at least not in the long run. ",
" I think that there is also a conflation in popular consciousness of methane coming from permafrost melt and the kind of large-scale methane clathrate/hydrate destabilization that has been put forward as a potential player in some of the large mass extinction events in the geologic record. We expect methane from permafrost to contribute additional warming as a positive feedback, but we don't really have a handle on what it would take to trigger a massive clathrate release. I know that people like the aforementioned David Archer who take climate-carbon cycle interactions very seriously don't seem to be super concerned about it given what we do know so far. Obviously that could change. "
] |
[
"It depends if you believe in global warming or not.",
"In my opinion, Global Warming (aka Climate Change - the more politcally correct term) is a very very very real situation. It probably can be concluded that the methane was released due to the permafrost melting. Immediate concern can be raised considering that methane is 20x more efficient at keeping in heat when compared to Carbon Dioxide - thus further spurring Climate Change (",
"http://www.epa.gov/methane/",
")",
"EDIT: And yes, you should be concerned. However, the release of methane is just a byproduct of increased warming of our earth. If you have anything to be concerned about, its the shear amount of energy that is required by our ever-growing population which then increases pollution, greenhouse gases, etc.....but if you dont believe in global warming, then 7 billion people that need energy (primarily from limited amounts of natural gas) is completely normal! (joke.)"
] |
[
"How does frame of reference in physics being arbitrary reconcile with kinetic energy being proportional to square of velocity?"
] |
[
false
] |
I'm having a difficult time reconciling my understanding of kinetic energy being the square of the velocity with my understanding of frames of reference being arbitrary. So given some frame of reference, say a spacestation traveling through a starless void at a speed signficantly less than the speed of light, a spaceship with mass of 1 Kg (guess it's a small ship) traveling at exactly the same speed (0) has 0 J energy of kinetic energy. If that ship speeds up to 1 m/s, it should now have 0.5 J of kinetic energy. Presumably this means that it fired its thruster for some length of time. Now if the spaceship doubles its speed, it's now going 2 m/s but its kinetic energy will have increased to 2 J. Did it need to 'expend' 3 times at much energy from it's thrusters to get to this speed? Now I run into the problem that I thought frame of reference is arbirary. What if we instead start with the moving 1 m/s frame of reference? Does it take less fuel for the spaceship to change speeds if we change our frame of reference? What am I missing here?
|
[
"Those are great questions, because they show that you're engaging with the concepts and trying to apply them in different scenarios to work out the consequences. Very good.",
"There's a couple of things to work through here. The first I want to to point out is that while energy is famously ",
", it is not ",
", which is to say that it does not stay the same between frames. Whenever you change your frame of reference, the total energy will change, but whatever happens the energy will stay conserved in that frame as the system evolves.",
"So now onto your questions about energy and velocity. The important thing here is that whichever frame you chose (and you do have complete freedom to chose your reference frame), you have to account for all the energy involved. If we say, for example, that our spaceship is propelled by a conventional rocket, then we need to account for the energy associated with the fuel and exhaust throughout the process. The entire system is ship + fuel: initially there will be some kinetic energy for both (which can be zero, if the frame we choose is the one where both are initially at rest), plus some (chemical) potential energy in the fuel. When the rocket burns, it converts the potential energy into kinetic, and that kinetic energy will be split between the ship (accelerating forwards) and the exhaust fuel (accelerating backwards). Afterwards, both the ship and the exhaust will have kinetic energy.",
"What changes, depending on how you chose your frame, is how that kinetic energy is distributed between the two. To address your question on whether it takes 3 times as much energy to go from 1 to 2 m/s, compared to 0 to 1 m/s: yes, that's correct. In the rocket case, you can interpret it as the rocket becoming more efficient at putting kinetic energy into the ship as it speeds up: at low (or zero) speed, most of the energy is put into the exhaust (flying backwards at high speed); you can also imagine the rocket eventually reaching some speed such that its exhaust has zero velocity in your reference frame and all the energy is going to the ship.",
"Changing your reference frame changes the seeming efficiency of the process, but doesn't alter the end result. In the scenario where the ship accelerates by 1 m/s, and you consider two frames where the initial -> final velocity is either 0 -> 1 m/s or 1 -> 2 m/s, each frame will observe the same amount of fuel spent (change in potential energy), and will observe the same ",
" in velocity, but will assign different values to the energy of the ship and the energy of the exhaust. Going through the full accounting of the energy budget in each case will show that each frame satisfies conservation of energy, even if they disagree on how that energy is distributed.",
"If it seems a bit arbitrary that the amount of energy in the exhaust 'just happens' to work out to balance the energy budget, regardless of the frame we choose, that's because we're discussing this at the purely conceptual level without detailed derivations. All of these results fall out naturally from the mathematics without the need for any particular fuss"
] |
[
"Thanks! This whole answer really helped reconcile these concepts for me. I love this way of thinking about it.",
"What changes, depending on how you chose your frame, is how that kinetic energy is distributed between the [ship and exhaust]."
] |
[
"This increased efficiency of conversion to kinetic energy is called the “Oberth Effect.”"
] |
[
"Why can't we produce milk or honey synthetically? What's so special about cows and bees?"
] |
[
false
] | null |
[
"I'll answer this for honey, though the answer for milk is probably pretty similar. What is boils down to is that ",
"honey",
" is a complex mixture of ",
"carbohydrates, proteins",
", ",
"acids",
", and ",
"organic volatiles",
". ",
"We don't know every molecule in honey, and we don't know exactly how much of each is in honey. Honey is produced through a series of partial digestions in a specialized stomach of honey bees, which includes the use of enzymes like ",
"invertase",
". Making some kind of mechanical device that could approximate this process is maybe possible, but providing it with the correct amount and types of enzymes and acids would be pretty difficult.",
"In short, we can pretty easily manufacture honey or milk substitutes that have a lot of the general (main) ingredients, but they lack the nuances of the biological processes that actually create the real deal."
] |
[
"For solidarity (and to piggy back this comment). Milk is an incredible complex mixture. Just milk fat alone contains approximately 400 different fatty acid species, which makes it the most complex of all natural fats ",
"Source",
". "
] |
[
"Honey was ",
"? Yuck! "
] |
[
"How do icebreaker ships work?"
] |
[
false
] | null |
[
"Modern ones are designed to 'ride up' onto the ice and then break it with their immense weight. Specially shaped bows (and sterns, for some that can go backwards), of course."
] |
[
"They break the ice with their weight. The bow is shaped like a spoon and allows the ship to slide on top of the ice and the weight of the ship pushes and crushes the ice downwards. Some ice breakers have big water tanks that allow swinging on the top of the ice, helping to break the ice below. Air can also be blown into the water to help the process and to be used in steering instead of extra propellers. ",
"The surface of the hull must be as smooth and frictionless as possible. low-friction paints and explosion welded stainless steel is often used for maximum smoothness. "
] |
[
"So you're saying they...cut through the ice?"
] |
[
"Can anyone help with questions about brain tumors?"
] |
[
false
] |
I am currently writing a story in which the protagonist has a benign brain tumor. From what I've read online, they are generally easy to deal with, but can be dangerous if they are in certain parts of the brain. I haven't been able to find out which locations are more dangerous than others in regards to this type of tumor. Additionally, in the interest of plot development, I wonder if there is a specific location where a tumor (or the removal of a tumor from this location) could cause mental instability, enough so to have the person committed to a mental institution. I don't want to make the character an invalid, so I'm not sure if this is an option or not. Any information or help with this situation would be greatly appreciated.
|
[
"A \"benign\" brain tumor will have varying effects upon a person depending on what area of the brain it's in. Much of our understanding about which parts of the brain control specific functions is due to case studies where individuals have had damage to those areas of the brain. For example, quite a few people have received damage to the ",
"Broca's area",
" of the brain. These people exhibit impaired speech. We can infer that this area of the brain must have some major function regarding speech. More recently, we have begun to use fMRI to study what the brain is doing when the person is given a specific task. Perhaps try to find a neuropathology textbook at your local university library, or maybe interview someone working in the field of neurology. Maybe you'll get lucky and an expert while chime in here. "
] |
[
"Brain tumours aren't easy to deal with generally; it does depend on location and type. For example, glioblastoma if left untreated can kill within around 4 months. As for location, a tumour of the brainstem (brainstem glioma), or a tumour of the cerebellum (medulloblastoma); both of these tumours are highly malignant. Benign tumours can be dangerous if they affect some function, so they vary on location. Hemangioblastomas of the cerebellum are an example."
] |
[
"Interestingly, I found two separate case reports of psychiatric illness seemingly arising as a result of a right intraventricular meningioma:",
"http://www.ncbi.nlm.nih.gov/pubmed/10085187",
"http://www.med.ucla.edu/modules/wfsection/article.php?articleid=120",
"These two seemed not to be invalids, even after resection.",
"Brain tumors are ",
" heterogeneous in the symptoms they produce, depending on their exact nature and exactly which tracts or gray matter nuclei they damage or disrupt, so almost any neuropsychiatric symptom is possible, if the location is right (although of course some symptoms are much more common than others, like headache, seizure, sensory or motor loss).",
"My experience (from listening to neurosurgeons talk about viable approaches to resection of brain tumors) would tell me that areas like Broca's and Wernicke's areas, the pre- and post-central gyri, the thalamus, the basal ganglia, and the brainstem (particularly pons and medulla) are some of the \"most dangerous\" places to have tumors. Any tumor that can stop the flow of CSF, for example, a third ventricular tumor, can cause potentially life threatening hydrocephalus.",
"The location described in the above two links (lateral ventricle invading the corpus callosum/periventricular white matter) is still potentially disruptive, but less so. My impression is that it's relatively low value real estate in the big scheme of things (although obviously it was enough to mess up these ladies' executive functioning).",
"It's really strange how some people can have truly gigantic tumors displacing huge amounts of brain tissue but have minimal symptoms, while others will have a tiny tumor in the \"wrong\" place that will give them absolute hell."
] |
[
"Looking at the position of the Sun provides a useful measurement of time during the day. Can I do the same by looking at the moon at night?"
] |
[
false
] |
There was full moon yesterday and it occurred to me that I should ask this question on before I fell asleep again. Is there a way to deduce an approximate time (like "it's around 23:00 o'clock in the evening") by looking at the position of the moon during nighttime? I'm not afraid of using additional information, like the date or a few memorized numbers.
|
[
"There are methods based both off of the moon and off of the stars.",
"The moon method is based off the fact that the part of the moon that is illuminated by the sun reveals where the sun is. The offset between the Moon and the Sun's apparent position is caused by the orbit of the Moon around the Earth, so the offset will vary with a period of about 28 days.",
"The stars method is based off of the fact that you can identify the north star, and that the pattern of stars around the north star will appear to rotate as the Earth rotates. This time you observe a particular angle with respect to the horizon will vary depending on the position of the Earth in its orbit around the sun, with a period of about 365 days.",
"As far as practical considerations go, the moon is brighter and more visible in cities and other high-light situations. However, some times of the month will have the moon close enough to the sun that you'll have part of the night where you can see neither sun nor moon.",
"A quick google search on this topic lead me to this: ",
"http://www.wikihow.com/Tell-Time-Without-a-Clock"
] |
[
"I have estimated absolute times and times till sunrise/sunset/moonset many times, and its a fun trick. The error is quite large though (+ or - 1 hour). But I think there is comparable error when I do this with this sun. ",
"First estimating the hours till sunset with the sun:",
"So if you assume the sun is directly above you at noon, and that it gets back there after 24 hours, you can point 1 arm at the sun and another at the western horizon. Then estimate the angle between your arms. (the estimated angle in degrees)*(24 hours/360 degrees)=the number of hours till sunset. Alternatively you can point your other arm straight up, and you will get the number of hours till/after noon depending on whether the sun is closer to the east or the west.",
"Estimating absolute time with the moon:",
"First make a half sphere with one hand like you would cup a large boob. Place your other hand so that it is flat on the fingertips of the first, defining a bisecting plane through what would be a whole sphere. Your first hand now represents the lit portion of the moon. With the exception of lunar eclipse the moon is always half illuminated. Now hold this model up next to the moon and try to orient it until you match what the moon looks like in the sky from your perspective. For example: with a full moon you would be looking completely at the back of your hand, and for a half moon you would be holding your hand in a position such that with your other hand you could make another half sphere and your bilateral symmetry would be preserved. For angles between these it gets a bit tricky, but you'll eventually find an orientation that seems reasonable. Then keep your flat hand still and take your first hand that was making the half sphere and point in the direction normal to the plane of your flat hand. Assuming you can't see the sun and you chose the normal vector that points into our planet you are now pointing at the unseen sun. So then apply the reasoning we used for the sun except now you can point straight down and measure the angle between the sun and down to give you the number of hours till/past midnight depending on whether the sun more toward the east or the west. Also you can point toward the eastern horizon and measure the hours till sunrise. Lastly the moon can be treated just like the sun for estimating moonset.",
"Hope this helps",
" if you read it you should be able to quickly and easily estimate absolute times and times till sunset/sunrise/moonset by remembering nothing except easily derivable and intuitive notions of celestial mechanics and illumination perspective."
] |
[
"Depends on the phase of the moon. If it's a full moon, the sun and moon are at opposite sides of the sky from each other, and the moon acts as a marker for where the sun is below the horizon (though you have to take your latitude into account and what season it is).",
"Alternatively, if the moon is in a half or quarter phase, it's tougher, but not impossible to tell about what time it is. I think the seasonal shift of the sun's position on the sky is the biggest complicating factor, though."
] |
[
"How does the process of creating the COVID vaccine differ from the process to create the flu vaccine each year?"
] |
[
false
] |
Are they the same, similar or completely different?
|
[
"There isn't \"the\" COVID Vaccine. There are many different kinds of mechanisms. The vaccines from Moderna and Pfizer are for example both mRNA Vaccines whereas Astazeneca's is based on an Adenovirus. Other manufacturers may also use different methods. So it may be easier to explain the machanism for the flu vaccines. ",
"The flu vaccine contains mostly 4 Viruses that are predicted to circulate the next season. This kind of flu vaccine is also called a quadrivalent flu vaccine (there is also trivalent flu vaccines that only contains three viruses). The quadrivalent vaccine contains two sort of viruses; two Influenza A and two B viruses. These viruses are mostly produced in embryonated chicken eggs (this is also the reason people can react allergic to those vaccines, since there might be some chicken protein left in the vaccine), but there are also other approaches for example in Chinese Hamster Ovary cells.\nThe viruses are harvested from the chicken eggs and get inactivated. ",
"https://www.cdc.gov/flu/prevent/how-fluvaccine-made.htm#:~:text=For%20inactivated%20influenza%20vaccines%20(i.e.,quality%20testing%2C%20filling%20and%20distribution",
".",
"Edit: I should add that the production of the flu vaccine is a highly standardized process where the vaccine for most influenza viruses can be produced with the same protocol.\nThe production of a vaccine for another type of virus isn't as fast and easy as the production of the flu shot."
] |
[
"There are Covid vaccines being developed that do use the traditional chicken egg method due to cost. One them currently under trial is ",
"NDV-HXP-S",
"."
] |
[
"I'm not really sure why the go to comparison is for flu with covid. There are plenty of other vaccines that most people receive that are more what covid vaccines are going for more similar results to. A big thing with covid is that we don't need the vaccine to predict and protect against every strain of coronavirus that could exist, just the one(s) from this year that are particularly deadly. Coronaviruses have been around for decades and only 3 of them have had major human health impact on a global level. The technology for making the pfizer and moderna vaccines was used for the first time for that kind application with the covid vaccines so not similar to flu at all. I honestly had thought there would be no vaccine as progress and research on SARS and MERS vaccines hadn't gone anywhere in decades and a large part of that is that the technology used at least for the pfizer and moderna vaccines didn't exist yet at the peak of that research."
] |
[
"Questions about quantum entanglement"
] |
[
false
] |
Alright, my layman's understanding of quantum entanglement is that particles can interact physically even when separated by an arbitrary distance. What kind of particles can we observe entanglement with? What kind of physical state changes can occur? What can we do to cause a state change? Is the change instantaneous? If so, how does the "information" about the state change travel faster than c?
|
[
"Is this one of those quantum things humans just don't readily understand?",
"Basically, if you mean that it's something non-intuitive based on our classical understanding of the world. It's a biproduct of quantum superposition, i.e. Schrodinger's Cat.",
"Using the cat analogy, imagine you've got a Schrodinger's cat box with 2 cats instead of 1 in it. As in the typical thought experiment, some quantum event is measured and poisonous gas is either emitted or not. Then the box separates into 2 different cat boxes that travel 100 miles from each other.",
"In the classical interpretation, both cats are either alive or dead, and we just don't know which until we open one of the cat boxes, but once we open one cat box and find a dead cat, we know with certainty that the other cat is dead, even though it is 100 miles away.",
"But the whole point of the thought experiment is that the way quantum weirdness works isn't what we expect classically. Instead of being alive or dead, both cats are in a simultaneous superposition of being either both alive or both dead. The entanglement part is that there are no mixed states (i.e. one alive and one dead) because they were either killed or not by the same quantum event. So they are both alive and dead until we open one of the cat boxes. By observing the dead cat, we then collapse the superposition on the other, and the cat 100 miles away is now definitively dead. No information is transferred because there was only one bit of information to begin with (alive or dead), but two cats."
] |
[
"I'm having a hard time wrapping my head around how it's instantaneous without some kind of \"communication\" at c between the particles",
"My understanding is that it's not that there's no \"communication\" between the particles, it's that it's impossible to transmit information this way because we can't control them. For a more intuitive, macroscopic example, imagine we have two \"entangle\" coins. Once one of the coins is flipped, whatever it lands on, it will always land on that. The other coin will land on the opposite side. So let's say you take one of these coins, and I take the other, and we travel several light years apart. Now I flip my coin, and it lands on heads. I now know that if you flip your coin (or if you've flipped it already), it will land on tails. But I can't actually send any sort of message this way, because I can't control the coin flip."
] |
[
"Experiments are typically done either with the spin states of electrons or the polarization states of photons. With electrons they're forced into a specific state by a varying magnetic field, with photons it's with optical components like filters and mirrors. The change is instantaneous but no actual information is transferred."
] |
[
"Do Mantle Plumes Originate From the Core-Mantle Boundary?"
] |
[
false
] |
[deleted]
|
[
"The science behind mantle plumes is a little uncertain because we are making inferences about what's happening thousands of kilometers beneath the surface, which unavoidably introduces some error. There are some things we can know about that depth pretty well, but it obfuscates many things too.",
"It is, however, a perfectly reasonable hypothesis, at least, based on a few bits of pretty well-confirmed data.",
"Mantle Plumes would require a continuous source of heat, and temperatures increase the deeper you get into the Earth, so it makes sense they would originate from the core-mantle boundary, where temperatures for mantle rocks are the hottest on average. It couldn't be lower than the core-mantle boundary because the core material (Nickle/Iron) is too dense to rise to the surface, even through heating. This may be what you are thinking of by 'seismic imaging'... hard to say, since\" seismic imaging\" can reveal a whole heck of a lot about the Earth's interior. Some people have tried to directly \"image\" mantle plumes through seismology, but it's pretty tricky to pick up something as \"small\" as a mantle plume with modern equipment and methods. I believe these studies at least generally support the theory though.",
"Mantle Plumes by necessity must be stable for very long periods of time - many millions of years at a minimum for the vast majority. You can find evidence for this within the ",
"Hawaiian island and seamount chain",
", to just name just one among many. We know how fast the Pacific Plate is moving, and how fast it has been moving (roughly) in the past, and we can estimate the amount of material the Hawaiian Island hotspot has released over its lifespan - and these observations can only really be reconciled if the mantle plume is a highly stable multi-million year feature, with only rare changes. This stability is easiest to explain by a core-mantle boundary origin for the plumes. ",
" EDIT: re-reading your post, I think I mis-interpreted your first sentence. Sorry about that.",
"The whole isotope thing is IMO the weaker bit of evidence, but it's still arguably easiest to explain by a core-mantle boundary origin than the other theories out there. For example Helium-3 to Helium-4 ratio can be used to estimate the age of a substance, since Helium-3 is lost without any practically no way of it being produced naturally on Earth, while Helium-4 can be produced naturally. So the relationship between the amount of Helium-3 and Helium-4 in a material can be used to judge from what point in time the material came from. It's tricky though, since it requires some assumptions about the source rock. As far as I am aware, nobody has done anything especially conclusive regarding them yet.",
"It's too early to \"call it\" for the mantle plume theory, but it is really quite favored by the scientific community. It appears capable of explaining all the evidence we see, it is considered fairly intuitive by most scientists in the field, and it doesn't appear to be overly complicated. That's a pretty good sign, for what it's worth. The plate theory is a fairly distant second, with really no other option anywhere close to being as seriously considered as those two."
] |
[
"Not to mention that seismic tomography imaging of plumes has a pretty significant ",
"error"
] |
[
"Cavanical has a great explanation. One major field of research is figuring out the density differences between the different layers of the mantle. Check out this ",
"figure",
" As you can see, a plume coming from the core mantle boundary would have a very hard time breaking through the transition zone equally, a subducting slab has a hard time sinking to the core mantle boundary. Even though we are pretty sure of these density differences, highly uncertain ",
"seismic tomography",
" shows that some plumes might come from the core-mantle boundary, and other plumes come from the transition zone. Enjoy Earth Science! "
] |
[
"Does light change colour when passing through a medium?"
] |
[
false
] |
I'm learning about light, reflection, refraction and similar topics in Physics. The textbook says: where n = absolute refractive index, c = speed of light in vacuum, λ1 = original wavelength, λ2 = refracted wavelength. The book uses this to explain how light disperses into colours as it passes through a prism, which I mostly understand (because speed of light in a medium depends on frequency), allowing each colour to have it's own distinct refractive index. My question is: If , doesn't this suggest that the wavelength is changed quite significantly as the medium changes? For example: red light has a wavelength of about 700nm, if it passes through a glass with n = 1.5, the equation suggests it has a new wavelength in the medium of about 466nm; a significant change in colour. In other words, does this mean that the red light that exits a prism was a different colour before entering the prism, and has been shifted to a shorter wavelength by refraction?
|
[
"You are correct that when light crosses from one medium into another, the wavelength changes. And the amount of change is determined by the refractive indices of both source and destination medium.",
"However, the velocity of the light is also changed by the same factor in this transition. What remains constant is the frequency of the light (which is velocity divided by wavelength). And it is ultimately the frequency that determines the colour of the light.",
"So while the wavelength changes as the light crosses into another medium, its colour does not.",
"Finally, if you look at the light (take a monochromatic light source, with just a single wavelength) going in on one side of a prism (or any other transparant object) and compare it to the light coming out on the other side, you will find that on both sides the light has the same wavelength, despite having gone through the prism. Why? Because the light undergoes two transitions into another medium, once from air into glass, once from glass back into air. The effect that each of these transitions has on the wavelength of the light cancels out."
] |
[
"The wavelength of light (in most normal situations, as long as there are no nonlinear elements present) only depends on the medium the light is currently in, not where it has been previously. So if light has a wavelength of 500 [nm] in air, and it passes through a cup of water, it will have a wavelength 376[nm] ",
", but in the air on the other side it will go back to being 500 [nm]. ",
"Now this has an important consequence: since the detection of light always occurs inside of your eye (in the vitreous humor right in front of the retina, which has an index of 1.337), no matter what light of a given free-space wavelength has travelled through (prisms, lenses, whatever), it will always end up having the same wavelength inside of your eye. So 500[nm] light will always be the same reduced wavelength of ~373 [nm] inside your eyeball, regardless of any prisms or other things it has passed through.",
"But when you say ",
", you need to be clear about what you're talking about. Most photodetectors (including the cells in your eye) will respond to a photon's energy, which is given by E=hf. So it is important to note that since photon energy doesn't depend on wavelength, that ",
". The frequency doesn't change in a medium, so the energy doesn't change, so the color detected by the photodetector doesn't change. "
] |
[
"You are write, the important quantity is the energy of a photon. The other parameters are derived from energy and possibly depending on the medium but the energy doesn't change. ",
"To expand a bit, the photon energy can change when entering non linear propagation regimes. Usually this requires high intensity (in simple terms a lot of light within a small area and short time) so does not happen in every day life but is very common (and used extensively) when working with lasers "
] |
[
"If you could detect and measure Hawking radiation, could you tell what was inside of the black hole?"
] |
[
false
] | null |
[
"If information is to be conserved (a principle known as unitarity) then the information brought in that everything that fell in, and then stored in the black hole, must then be all contained in the total Hawking radiation emitted by the BH in its whole lifetime, after it's evaporated completely.",
"If you had perfect, microscopic knowledge of the quantum state of the total Hawking radiation (and of the fundamental laws of the Universe, including quantum gravity) you'd be able to reconstruct the original state of the matter that fell into the black hole.",
"However, this information is stored in the Hawking radiation not in some straightforward way as a certain number of bits per amount of radiated particles; the radiation is instead strongly entangled with itself and the information lies there. In practice, this means that even omitting a small part of the radiation makes most of the information unreadable. There's a more famous example of how this works:",
"I'm Alice and I have a message to you, Bob. I write my arbitrarily long message in a piece of paper and throw it in a black hole. You try to decode the message from the Hawking radiation that comes out. It turns out you need to wait for ",
" the whole BH (in horizon area) to evaporate before you can even decode ",
" single bit from my message. This is because when the BH is partially evaporated, the information of the message is in great part encoded in entanglement between the Hawking radiation particles and the remaining portion of the black hole itself. (This cryptographic property of BH is very important in that it solves a very tricky problems with the holographic principle, known as the xeroxing paradox).",
"In any case, all of this assumes you can acquire perfect microscopic knowledge of the state of Hawking radiation. In reality, you are a macroscopic observer unable to perform anything else but a few macroscopic measurements. In this sense the information in Hawking radiation is completely unreadable and it looks like a zero-information state from a macro perspective - equivalently, it has maximum entropy. That's why it's in thermal equilibrium. From this macro POV then BHs are ideal shredders, completely erasing useful information. Of course what really happens is that the info is not getting destroyed, but just getting very scrambled to the point of being macroscopically unretrievable. "
] |
[
"A system can be in many possible states; to each you can assign a value for the entropy. Amongst all states of a system with a given energy, there is one with higher entropy than all the others. It's not too hard to prove this is actually the state of thermal equilibrium.",
"Entropy can be understood as the lack of information the macroscopic observer has. The higher the entropy of a state is, the less you know about the system by knowing it's in that state. The state of maximum entropy, or thermal equilibrium, corresponds to zero bits of information for the macro observer.",
"The main feature of Hawking radiation, essentially the heart of Hawking's derivation, is that it is in thermal equilibrium at a temperature inversely proportional to that of the black hole it comes out of."
] |
[
"the interior and surface of the black hole, according to the complementarity principle, are the same thing, just two different perspective on it. That's the magic of holography. There is information in the black hole, and you either picture it as being encoded in a membrane on the horizon, or equivalently in the 3D interior region of spacetime. Not both at the same time though, that's cloning, and it's forbidden."
] |
[
"What causes the rebound when a star collapses on itself and goes supernova?"
] |
[
false
] | null |
[
"There are two reasons behind it.",
"First is the immense shock wave in the core of the star due to the incoming matter smashing against the core. This shock wave slams against the collapsing matter which slows it down separately. This means less energy is required in order to reverse the matter and send it spewing outwards in an explosion, meaning the explosion is bigger.",
"The main reason for the intense energy outburst of a supernova is because due to the intense conditions of the majority of the mass of the star slamming into the core, and due to complex quantum mechanics, a vast, almost mind blowing amount of neutrinos are produced. The total energy of these neutrinos can be greater than 100 times the energy that the sun will produce over the span of it's entire lifetime. Now, neutrinos are very nonreactive with normal matter, but the density of the matter collapsing inwards combined with the vast amount of neutrinos produced means huge numbers of neutrinos transfer their energy to the incoming matter. This causes the direction of the collapse to be reversed and blast outwards in a giant supernova explosion."
] |
[
"It's essentially a bounce. The matter collapses inward, and the rapidly intensifying pressure in the core causes (in most supernovas) the matter to be converted to neutrons, and then the rest of the infalling material will be pushed outward."
] |
[
"So someone should probably correct me, but I think the implosion creates both high intensity energy that can escape the massive gravitational pull while simultaneously creating the excessively dense materials that then further collapse in.",
"Like imagine smashing a raw egg in your hand. The dense shell will crumble and collapse into your hand while the lighter egg whites spill from between your fingers."
] |
[
"Are our oceans getting saltier?"
] |
[
false
] |
I was reading some other post about how the hotter weather means that the air can also hold more water, and this is also why storms are getting stronger because of the higher amount of water that needs to be dumped. So my question is, since storms are also getting bigger, and more and more seawater is evaporating, is the amount of salt being left behind increasing?
|
[
"The most notable change has been the intensification of the water cycle and resulting gradients. At a local scale, salty regions become more salty and fresh regions become more fresh. Example papers on the subject: ",
"1",
" ",
"2",
"A significant problem is that we don't actually have reliable ways to measure ocean salinity at a large scale. See ",
"here",
":",
"However, the demonstrated usefulness of salinity in oceanography is in striking contrast to the practical inability to directly measure it (Lewis ",
"1980",
", Millero et al ",
"2008",
"). During the last century, only two methods of measuring this total dissolved mass were successfully exploited to establish salinity scales that were officially adopted by oceanography, namely by drying a sample and weighing the residue (Forch et al ",
"1902",
"), or by carrying out a complete chemical analysis of the sample's composition and adding up the constituent masses (Millero et al ",
"2008",
"). Neither method is appropriate for the frequent regular measurements required in oceanographic studies, nor are they mutually consistent with one another within requisite accuracy. In practice, oceanographers, for many years, have used the fast, reliable and robust technique described by the Practical Salinity Scale of 1978 (PSS-78; see Unesco ",
"1981",
") to approximate these other methods.",
"They actually wrote a ",
"Part 2",
" discussing at length the difficulty in measuring salinity."
] |
[
"Due to global warming and melting polar ice caps, it is assumed that oceans will become more dilute and less salty.",
"I would say both will happen. As usual, we can only, and should, measure and monitor salt concentration to establish which effect is greater."
] |
[
"Salt in the oceans have reached a near-equilibrium state. Salts react with ocean minerals at roughly the rate that they are added due to runoff. There are a few other processes that salt is removed from the water, but reacting with minerals is the major one. For this reason, the salt content of the oceans stays relatively stable."
] |
[
"How do I answer this question about evolution? I've hit a wall with him"
] |
[
false
] |
This is a conversation on Facebook that's gone on to nearly 100 posts... His latest one is: "evolution is concerned with expressions of the various traits of living things. how can anyone profess a proper understanding of the expression of traits without understanding what's doing the expressing. Darwinian evolution solves this problem by saying there is nothing being expressed except random chance, which. when taken to its logical conclusion states that we are simply self-replicating self-perpetuating chemical chain reactions, which of course doesn't explain consciousness, laughter, pain, emotion, et al. this of course means that we have no free will as well. it can't possibly be correct. this brings us all the way back around to the original topic which is the absurdity of not "believing" in Darwinian evolution (as opposed to some other form), which all i'm trying to impress upon is not that absurd. You derided an agnostic mathematician simply because he considers himself a creationist, and has found unlikely allies within the religious communities. i just wanted to point out that there is likely a lot more to changes in life forms over time than the academic theory of evolution gives it credit for. i certainly don't have any of the answers myself, just a lot of unanswered questions." I'm like hitting my head against a wall here. I have a degree in Science so I've taken courses in Biochemistry, Molecular & Cellular Biology, Organic Chemistry, Chemistry, Microbiology, Biology, etc -- but I just don't know where to go from here.
|
[
"how can anyone profess a proper understanding of the expression of traits without understanding what's doing the expressing. ",
"DNA codes for proteins",
"expressed except random chance",
"Not random chance. Variation with selection.",
"we are simply self-replicating self-perpetuating chemical chain reactions,",
"Non-sequitur",
"which of course doesn't explain consciousness, laughter, pain, emotion, et al.",
"Appeal to emotion; phenomena explained by emergence.",
"this of course means that we have no free will as well. it can't possibly be correct.",
"Does not follow or matter.",
"blablalbaherpderpderp",
"Who gives a shit.",
"i just wanted to point out that there is likely a lot more to changes in life forms over time than the academic theory of evolution gives it credit for",
"Evidence or stfu.",
"This is the question I would ask: "
] |
[
"I have no idea what that person you are arguing with is saying. If there is an attempt at a logical argument in there somewhere, it did not succeed."
] |
[
"This guy obviously isn't interested in discussing science if he is using terms like \"spark of like\" or \"elan vital\""
] |
[
"How do living organisms interpret DNA?"
] |
[
false
] |
So if I have some sequence of DNA that we know will produce a certain chemical in a bacterium for example how does the sequence get interpreted? My assumption is that for all organisms the same DNA will produce the same results. Is it possible to take any piece of DNA and using the rules of interpretation figure out what it does. Imagine I then had to translate this to programming code how would it be done?
|
[
"Basically, a segment of DNA gets translated to RNA, which is a similar molecule with a slightly different structure. Then, the RNA goes through an organelle called a ribosome where it is transcribed into a protein. Each set of three genetic letters adds an amino acid to a protein, and a protein is a chain of amino acids. So depending on the genetic sequence there will be a specific protein sequence, such that a gene codes for a specific protein. Biochemical interactions occur between proteins."
] |
[
"To answer a couple of your other points:",
"1) In general yes, DNA from one organism will be expressed in the same way in another organism. This principle is at the cornerstone of genetic engineering. For example, a while ago I inserted a a sequence of DNA from P.falciparum (a single-celled eukaryotic parasite that causes malaria) into E.coli (bacteria, harmless) so that I could get a large amount of the product of that gene (a ribosomal sub-unit) since E.coli is much easier to grow in the lab than P.falciparum and is non-infectious.",
"2) In one sense it is extremely easy to figure out what an arbitrary sequence of DNA will code for, but in another sense, it is one of the most difficult problems in modern science. The easy part is that there is a well established code that means every 3 base pairs of DNA (called a codon) stands for one of the 20 amino acids that make up proteins. For example GCA = alanine. Where it gets really hard is figuring out what a given protein (a long chain of amino acids) will do. The problem is that each protein doesn't exist as a long chain, in order to be functional, they fold into a complicated 3D shape. Figuring out how a given protein will fold is immensely hard since it depends not only on the sequence of the chain, but also on a variety of external factors. Most researchers use pretty powerful super-computers to solve the problem, and so far no one has gotten very good at it.",
"3) This all applies for DNA that codes for proteins. There is plenty of other DNA that does not, that used to be considered 'junk', but there is a growing understanding that it plays a role in gene expression, that is, which parts of your genome are active at any given time. Remember that every cell has the same DNA, so what makes a brain cell different from say a muscle cell is which parts of its genome are active at a given time.",
"If you want to know more, figuring this out is more or less the focus of Biochemistry as an academic field. Picking up a good textbook should help get you started. Some good keywords for you would be: gene expression; protein folding; proteomics; central dogma of molecular biology."
] |
[
"Good answer! I just have one thing to add about protein structure:",
"X-ray crystallography is the go-to method right now for determining the three dimensional structure of a protein to near-atomic level resolution. While you need a good x-ray source for data collection, the actual solving of a structure can be done on almost any laptop. More to your point, figuring out HOW they actually adopt their fold is still extremely difficult and is often guessed at using modeling.",
"If you are interested in protein 3-D structure I highly recommend ",
"www.pdb.org",
", it's where we deposit our protein structures and they have great educational sections."
] |
[
"What are the evolutionary ancestors of spiders?"
] |
[
false
] |
How did spiders get from non-web building creatures to web builders?
|
[
"The first creatures we classify as \"aracnids\" come from the late Silurian.",
"Trigonotarbida",
" is the earliest aracnid we have in the fossil record.",
"Spiders themselves generally are very mysterious in the fossil record because they are extremely poor specimens for fossilization so little is really known about them."
] |
[
"I didn't want to have to type this all out on reddit, so I wrote it on paper and here's the link to a picture of it. ",
"http://imgur.com/wMkUcW1",
"But like what has been said, spiders are fairly mysterious when it comes to evolution and what not due to the lack of fossils to be able to accurately place them in the big scheme of things. But what I did in this picture is write out a broad evolutionary chart/classification of spiders, so if you want to know it's evolutionary ancestor just go in reverse order (order aranea -> domain eukarya). The earliest organisms in each taxonomic classification are the \"base\" evolutionary ancestors to everything that comes after it. I hope this helps a little. ",
"Source: \"Animal Diversity sixth edition\", by: Hickman, Roberts, Keen, Larson, Eisenhour",
"Edit: I forgot to mention, if you look carefully at the picture in the Phylum: Arthropoda section, you can actually see an ant on the page. The little guy ran across my desk as I was taking the picture. I thought it was funny. I chuckled a little...."
] |
[
"There is a Cambrian thingamajig called ",
" which is believed to be somewhere along the common original stem to proto-arachnids, sortof a common ancestor to spiders, eurypterids and eventually scorpions. ",
" was a marine nektonic to benthic predator which may have relied on pursuit.",
"Between these and the first quasi-spiders in the Devonian (see ",
"), pretty much all we've got is various species of ",
", so as far as I can tell it is unknown whether spiders branched out from before the Eurypts with fossils remaining to be found or if they branched out from the Eurypts later on.",
"As to ",
" (perhaps named by a Tolkien fan?), seems it had silk-producing spigots but no spinnerets, so it probably was not a web-builder. for the rest, see: ",
"http://en.wikipedia.org/wiki/Evolution_of_spiders"
] |
[
"If air can both heat things up (friction) and cool them down..."
] |
[
false
] |
[deleted]
|
[
"Air/wind doesn't have any special heating/cooling properties. It follows the same laws of heat exchange equilibrium that everything else does: If you put something a room with warmer air, it'll get warmer. If you put something in a room with colder air, it will get cooler.",
"But your car engine has something in common with your body: it produces heat while it's working. Accordingly, the air immediately surrounding your body or engine is hotter than the air in the surrounding environment. When you turn on a fan and feel cooler, all that's happening is that the fan is dispersing the heat cloud that's surrounding your body (the opposite of what a blanket does: trap the heat cloud so that the heat builds up).",
"So the answer to your question is that moving wind across a thing doesn't have any special mechanism for cooling that thing down. But if that thing has a bunch of heat already around it (as anything that produces heat will), blowing this cloud away can keep the temperature of the object from getting out of control."
] |
[
"which is created because of friction (?).",
"Note that many things that go wicked fast (as in an atmospheric entry) are heated not because of friction but because the air is compressed into a hot ",
"shock layer",
" in front of the object."
] |
[
"The speed is never \"too high to disperse the heat cloud\". The heat cloud is going to get dispersed no matter what. It's just a matter of putting in more heat (via friction) than you're taking out (via dispersion), and the exact point at which this happens will vary with the situation for objects that produce heat.",
"For objects that don't produce their own heat though (such as the fighter jet wings), I don't expect there will be a point of equilibrium such as you have described. That's because the only heat that's there to be expelled is the heat you're putting in with wind friction. But you'll always be putting it in faster than you're dispersing it. This is due to a couple of things, including the fact that the heat is transferred not only out of the object but also deeper into it (objects become hotter/colder in response to their environment from the outside in), and the fact that if it weren't true you wouldn't actually be heating the object to begin with.",
"tl;dr: For heat-producing objects it depends, and for non-heat-producing objects, there is no such point."
] |
[
"What would life be like if our planet was tidally locked?"
] |
[
false
] | null |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"For more information regarding this and similar issues, please see our ",
"guidelines.",
"/r/AskScienceDiscussion",
"Please see our ",
"guidelines.",
"If you disagree with this decision, please send a message to the moderators."
] |
[
"I guess the wording was a little vague, I didn't mean to ask how life would adapt to such conditions but rather, what the consequences would be if earth were to become tidally locked tomorrow? Would the dark side freeze and sunny side fry?"
] |
[
"Hypothetical or \"what if\" questions like that would still be better off in ",
"/r/asksciencediscussion"
] |
[
"Why do my sister's eyes change color when she cries?"
] |
[
false
] | null |
[
"I have no rhyme or reason to give you, but pics would certainly be nice."
] |
[
"Sorry, but we don't allow questions like this, for reasons that I think were best explained ",
"here",
". As such, I've removed it."
] |
[
"Whoops! My bad "
] |
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