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[
"What happens to an asteroid when it hits a gas giant such as Jupiter?"
] |
[
false
] |
Thank you for your time.
|
[
"An asteroid that hits Jupiter will be moving very fast, because Jupiter is very massive and thus has a lot of gravitational potential. When the asteroid hits the atmosphere, it will compress the gas in front of it as it falls. Compressing a gas heats it up. This heats up the asteroid to 1000s of degrees.",
"At the same time, the atmosphere is slowing the asteroid down. As it's slowing down, it experiences a lot of g-forces. This puts a lot of strain on the asteroid.",
"The strain plus the heat eventually are too much for the asteroid to handle and it breaks up. This releases a lot of energy. Really it's more \"explosion\" than just breaking up. The pieces that it breaks up into then experience the heating and the strain, and they break up or explode too. ",
"It's very common for meteors to explode in the atmosphere, even in earth's atmosphere. The ",
"Tunguska meteor",
" exploded in the atmosphere over Russia in 1908."
] |
[
"Image of Jupiter impact."
] |
[
"Depending on the size of the asteroid, it either gets torn apart by the gravitational pull (like the Shomaker-Levy comet) or enter the atmosphere in tact and then burn up from the increasing friction and heat as it travels deeper into Jupiter's atmosphere where the gasses are more and more dense acting almost as a solid surface at those speeds. Just as doing a belly flop into a swimming pool is painful because the water behaves almost as a solid at the moment of impact. "
] |
[
"Why does fusing/splitting atoms cause such a large explosion?"
] |
[
false
] |
I was reading up on World War II in my history class and the creation of the atomic bomb, hydrogen bomb, etc. What causes the tremendous explosion from the atom? Also, is splitting or fusing an atom more explosive?
|
[
"Like stated it happens because these atoms have a lot of energy in them. Also, I can't tell if you relize this or not, but the atomic bomb dropped in Hiroshima had 2.5621 x 10",
" atoms splitting so its not just a single atom. The splitting of one atom would be almost undetectible. And the energy released by fusion is more powerful than fission. Fusion is actually what the sun and all the stars run on!"
] |
[
"When atoms fuse or split the binding energy per nucleon (proton, neutron) is different between the starting nucleus and the new nucleus. ",
"Nuclei are trying to reach their most stable form so are heading to the forms that have the highest binding energy per nucleon (as then it is not energetically favourable to change). If we look at a pretty simple example with the fusion of Hydrogen to Helium-4 (as is the overall process in a main sequence star like our own) the mass of 4 protons (the hydrogen is just an electron and proton and only the proton is involved in the nuclear reaction, and the electron is ionised off anyway) is greater than that of the Helium core.",
"This lost mass is given off as energy. 4 H c",
" - He c",
" gives the energy given off (as mc",
" as previously mentioned). ",
"Lots of energy, controlled in the right way, leads to the explosions you were asking about"
] |
[
"Ohhh, I think that's the part I was confused on. I was under the assumption that a single atom caused the explosion. Thanks!"
] |
[
"How did we discover molecular processes like the Krebs cycle or electron transport chain?"
] |
[
false
] |
“I need someone to explain this to me like I’m a 5 year old” - Michael Scott It’s very easy to see how astronomers can look at large moving bodies and formulate a hypothesis and test the hypothesis with models and then identify if celestial motion can be accurately predicted. How do we do this in a cell? How do we replicate cellular biology? It’s blowing my mind and I assume these processes work so fast and are so small that we can’t visually see them.
|
[
"How we do it now vs how it was done at the discovery are very different.",
"Today we have both the tools and the understanding that we can actually measure some aspects of biology in real time. Ultra fast cameras, high powered lasers, high speed processors, have all contributed to our ability to ramp up our observation capacity to match that of what's actually happening in our cells.",
"Before technology helped us catch up what we (and by \"we\" I mean the absolute legends who's names fill our text books) did was actually measure bulk flow of reactions, and determine what must have happened microscopically in order for the macroscopic change to occur.",
"Perhaps you've seen chemistry experiments that mix two clear solutions and results in a color change? Its similar to that. The individual reactions at a molecular level are much to fast to have been observed independently, however en mass they are observable.",
"Many of the founders of biology were pure chemists who understood how to chemically isolate and identify compounds. So they could take tissues and dry them out, then separate the powder to figure out what they were made of. For tissues that happen to be very densely packed with mitochondria like the liver and skeletal muscle, the molecules of the Krebs' cycle made up a large component.",
"There are so many really amazing techniques used and pioneered by this generation of scientist that truly laid the foundation of modern biochemistry.",
"Here's a brief account of Krebs' work",
"https://academic.oup.com/labmed/article/41/6/377/2657667",
"Here is a more detailed account of the state of science during the life of Hans Krebs'",
"http://www.jbc.org/content/277/37/33531.full"
] |
[
"I'll answer your question as well as trying to explain concepts as simple as possible in two parts: part one is the discovery of the Krebs cycle, and part two is how we can confirm/replicate molecular processes.",
"In the 1930s, scientists knew a good amount about fermentation, which does not use oxygen, but didn't know much about aerobic respiration. It wasn't fully understood how oxygen and carbohydrates came together to produce energy. Hungarian scientist Albert Szent-Györgyi did some of the initial research into this and is credited with discovering some compounds involved in the Krebs/TCA cycle. He did this by testing different compounds and their effects on cellular respiration on pigeon breast tissue. He noticed that when a particular group of compounds called dicarboxylic acids was applied to the tissue, way more oxygen was being used by than tissue than what should be needed to oxidize the compounds ",
"[1]",
". ",
"Most of biochemistry involves the transfer of electrons in what are called redox reactions; in the case of these dicarboxylic acids, they are able to donate hydrogen atoms (oxidation) to facilitate the production of energy (reducing other compounds). Szent-Györgyi saw that this was occurring in the tissue in excess, and realized that these acids were not being used as energy, but were catalyzing reactions (start and end the same in a chemical reaction) that utilized other compounds for energy. He came up with a working hypothesis for some compounds at work, and validated his results. ",
"Hans Adolf Krebs would also validate the work of Szent-Györgyi, but would go further and put all the compounds together into what we now know as the Krebs cycle ",
"[2]",
". We also call it the tricarboxylic (TCA) cycle, which I think is nice because Szent-Györgyi helped lay the groundwork for Krebs to build on. Szent-Györgyi got caught up on his dicarboxylic acids, while Krebs realized that citric acid, which is a tricarboxylic acid is the key compound in the TCA/Krebs/citric acid cycle.",
"I think the best way to answer how we replicate cellular biology is using models/assays in a careful, controlled, and methodic manner. You can't just throw all these Krebs cycle compounds into a test tube and expect it to work. Szent-Györgyi and Krebs carefully came up with a hypothesis for what's happening in respiration, a system to test this, carefully tested each portion of their model, and then put all their results together into scientific papers.",
"Source: in text and I'm a PhD student in molecular biology."
] |
[
"“Standing on the shoulders of giants” has never felt more applicable. True geniuses."
] |
[
"What are the risks of consuming genetically modified food? Can GM food be harmful, and when?"
] |
[
false
] | null |
[
"There are real risks to the use of biotechnology in agriculture, they can be broken down into a few catageories. I will make a post for plants and post for animals.",
"There have been a variety of publications on this subject, but with the exception of a few high contraversial publications, the scientific consensus is fairly firm. ",
"This is most succinctly stated by these sources",
"US National Academies of Sciences stated: \"To date, no adverse health effects attributed to genetic engineering have been documented in the human population. \"",
"\"A 2008 review published by the Royal Society of Medicine noted that GM foods have been eaten by millions of people worldwide for over 15 years, with no reports of ill effects.\"",
"There have been a few publications which state evidence of harm (Pusztai et. al, Seralini et al. for example). However, these fall into two categories, either meta-studies of rat feeding trials or rat feeding trials themselves. They have been controversial because in both cases they did not conduct robust experiments and made conclusions which were clearly not supported by the evidence. The \"significant\" results which they say cause harm are more than likely just noise. If you would like me to discuss the details of why these papers are not robust I can, but for now I will leave it at that.",
"While research continues, it is very unlikely that robust evidence of harm from BT or CP4 EPSPS will be found and it is safe to say there is no health risk from the currently approved commercial crops.",
"*",
"By introducing a foreign protein into an ecosystem it may cause unintended ecological damage. ",
"In the case of BT, a protein which is toxic to a narrow clade of insects. It has been shown that it readily breaks down in the environment. Additionally it helps reduce the application of broad spectrum \"chemical\" based pesticides",
"[1]",
"[2]",
". While there have been concerns raised about \"non-target\" killing of insects such as the monarch butterfly, ",
"the evidence has eventually shown that BT has not affected wild populations",
".",
"In the case of CP4 EPSPS, aka roundup ready, the waters are murkier. It has the advantage of encouraging \"no-til\" agriculture, which can massively reduce erosion and promote soil ecology. However, it also has increased the use of glyphosate application. Some would argue that glyphosate is a milder substitute compared to what farmers would normally use like 2-4-D, atrazine or paraquat. The end result though is a net increase in herbicide use.",
"Lastly there is the risk of environmental damage from a gene crossing into wild populations. This has already happened. In the case of CP4 EPSPS, it has drifted into wild rape populations. However, it has not caused environmental damage. Likely the trait will simply degrade via neutral mutations because it has no selective advantage in wild populations. ",
"Having the BT trait move into wild populations presents a higher risk. It might alter the success of the wild species and change the ecosystem. However, this has not happened on a large scale. The trait has been only used in crops which are unlikely to cross breed with wild populations, or unlikely to grow in the wild. Many agricultural species are unable to propagate themselves in the wild and this is used as a way to control the traits spread.",
"The last risk is by using GM technology, we create resistant weed species or insects, what the popular press has dubbed \"superweeds\".",
"While it sounds scary, it is much less of a risk than it sounds. Resistance is a problem found with any biotechnology. By using BT and CP4 EPSPS we are actively selecting for weeds resistant to glyphosate and insect pests resistant to BT protein. However, this can be managed fairly effectively. ",
"Two methods exist to effectively combat resistance. The first is to use \"sanctuary\" fields with no BT to maintain a level of genetic diversity in the population. This will help prevent a resistance trait from fixing in a population. The second method is by raising the cost of selection through cycling of different traits or herbicides. This creates a situation where there are so many different types of pressure that the population cannot adapt to any one. This approach has worked before with HIV patients. By cycling different anti-retrovirals you can effectively manage the infection and substantially prolong their lives. In plants, farmers now have several traits to select from and can rotate them from season to season to prevent development of resistance. ",
"While both these methods have been proven in other areas of biology, whether they can be used in concert to manage resistance over the long term remains to be seen. ",
"Edit:",
"If you are interested FRONTLINE and NOVA did an excellent documentary on the subject a few years ago ",
"http://www.youtube.com/watch?v=6NsI0ba9dNg"
] |
[
"That's a rather complex question, and there are certain facets of it I feel like I should learn more about. But I do feel confident in saying that the ",
" danger of consuming GM food, i.e. health risks from the food itself, is pretty negligible.",
"A lot of the scare tactics used in anti-GMO literature (frankenfoods, bacterial/viral genetic material, etc etc) is rooted in a fundamental misunderstanding of how our body processes food. The idea that certain proteins will be bad for us because they come from other organisms, or are \"alien\" to human diets, is total hogwash. ",
" All dietary protein is broken down into amino acids in the stomach and intestines, ",
" before it ever enters your cytosol proper. It is the only sensible way to do things -- your body depends on an extremely delicate balance of all its constituent parts, regulated by elaborate feedback mechanisms. If there were this massive, unregulated flow of thousands of kinds of unknown material into your body, how could your cells ever hope to maintain homeostasis?",
"The only exception to this is protein that acts extracellularly, ",
" the digestive tract. This is why Lactaid, which is basically just the enzyme lactase, helps treat the lactose intolerant, but only for a few hours.",
"Now, genetic modification does not only affect an organism's proteome, of course. Those new genes do things, and those \"things\" often involve the creation of different kinds of small molecules -- metabolites. There ",
" the possibility of different sorts of metabolites having a negative effect on your body. However ",
". I don't think the average layman appreciates just how excruciatingly detailed and precise FDA testing is. I trust most anything that comes out of that agency implicitly.",
"There are, of course, other questions surrounding the effects of GMO foods, but these are questions about ",
" effects. I'm talking about things like their effects on farmers, particularly third world farmers, or biodiversity. On these topics, I will agree with the anti-GMO crowd that there ",
" a dearth of information out there and that it merits a ",
" more detailed investigation than it has received. However, a lot of these secondary effects are easily countered by GMO providers, but are not. In other words, I feel like most of the negative effects that might come from GMO foods today are because of the policies of companies like Monsanto, not anything inherent to genetic modification."
] |
[
"There are two \"animal\" GM foods, rBGH in milk and the \"GM Salmon\" ",
"There has been significant concern over the use of rBGH to increase milk production. ",
"The concern is centered on the fact that using rBGH in cows increases the levels of IGF-1 in the milk. The fear is that by drinking milk which has used rBGH, it will increase your serum levels of IGF-1 and might cause cancer. ",
"It was approved by the FDA despite this, and here is why.",
"From the EU evaluation of rBGH:",
"\"Mean concentrations of IGF-I [in milk] were 2.77 ± 1.36 ng/mL in control cows and 3.30±1.40 ng/mL in treated cows, respectively.\"",
"Compare that to the normal range as stated in a laundry list of scientific papers :",
"\"1-34 ng/mL, normal milk (Malven et al., 1987; Campbell & Baumrucker, 1989; Juskevich and Guyer, 1990; Collier et al., 1991; Schams, 1991; Zumkeller, 1992).\" ",
"From the FDA re-evaluation in 1999:",
"\"Assuming 5000 ml blood plasma volume in a 60 kg person and assuming this person consumes 1.5 liters of milk containing 9000 ng IGF-I from rbGH-treated cows (as opposed to 6000 ng IGF-I in milk from untreated cows), the maximum increase in blood IGF-I would be less than 2 ng/ml of which only one-third could be attributed to the use of rbGH. This minute increase would dilute into the endogenous pool of circulating IGF-I.\"",
"and here is one more paper I found.",
"\"From a consumer perspective, bST was unique, and special interest groups loudly predicted dire consequences. However, introduction of bST had no impact on milk consumption, and milk labeled as recombinant bST-free occupies a minor niche market. \"",
"While there are scientific opinions that are critical of rBGH safety ",
"such as this one",
" they fail to provide evidence that IGF-1 occurs at a rate beyond the physiologic range. It simply hand waves the point and moves forward. ",
"GM Salmon have yet to be commercialized, but there is also fear of increased hormonal levels. While I do not have a citation on hand at the moment, the levels of growth hormone have been show to no be significantly increased compared to a control. The GM salmon simply expresses that hormone over a longer period of time compared to the normal, seasonal salmon.",
"*",
"In the case of rBGH, there is no potential of harm to the larger ecosystem, but it has been shown that it can increase mastitis. Mastitis is an infection of the cows utters which can both cause pain and taint milk with bacteria. The only solution is to use antibiotics to help prevent infection. In my opinion that is enough reason alone to not use rBGH.",
"The real concern over the approval of GM salmon, is the a paper from 1998 which predicted that it could cause a population crash. The trait doubles the growth rate of the salmon, and in the wild these fish would out-compete normal fish for mates. The company, aquabounty, which wants to approve these fish has tried to solve this problem by making all commercial fish both female and sterile (lol Jurassic park). However, it is not a perfect solution, and it has been scientifically predicted that as few as single fertile GM fish, which escapes into the wild, might destroy wild populations. The fertile GM fish would consistently win mates but would produce offspring which would not survive the winter. The current solution has been to seek approval for use only in inland fishing operations as opposed to net pens which are connected to the ocean. ",
"C. Risk of making a technology no longer useful.",
"There is no real risk of resistance in rBGH or with GM salmon."
] |
[
"Is it possible for a planet to be larger than the star that provides light for it, so that the sun revolved around the planet?"
] |
[
false
] |
I hope this hasn't been answered already... I just had a philosopher moment sitting here on the couch.
|
[
"Actually, regardless of the relative sizes of the sun and the planet, both would orbit around their combined center of mass. It's just that when one is much bigger than the other, the combined center of mass is very close to the center of mass of the larger body. For simplicity and convenience, it is often said that the small one orbits the large one, while in fact both orbit each other. ",
"Here",
" is a diagram of the combined center of mass of the entire Solar System relative to the Sun."
] |
[
"In fact, one of the very first extrasolar planets discovered was around a pulsar, ",
"PSR B1257+12",
". Pulsars are incredibly small and incredibly dense, and PSR 1257+12 is no exception: despite having a mass 1.5x our sun's, it has a radius of only 14 kilometers. ",
"However, calling a pulsar a star is a stretch. They are held up against gravitational collapse by neutron degeneracy pressure, not nuclear fusion. So any planet around a pulsar is going to be near 0 K in temperature. And neutron stars are formed by the collapse of massive stars, which means any planets in orbit had to weather a supernova sometime in the past."
] |
[
"If you're familiar with fusion, you may also be familiar with the idea of hydrostatic equilibrium. Essentially, a star is a collapsing cloud of gas. As gravity pulls the cloud inwards, it becomes more and more dense and heated. (An aside: this doesn't always happen. The ",
"Jeans criterion",
" must be met first.) Initially, gravity is the only relevant force, and matter falls inwards without opposition. But once a certain temperature is reached, suddenly something happens.",
"That something is fusion. A cool historical story about this is, before quantum tunneling was well understood astronomers were puzzled by fusion in the sun. Although they were able to determine the temperature at the center of the sun, that temperature is actually too low, classically, to ignite fusion reactions. It was only once ",
"tunneling",
" was understood mathematically that astronomers realized what was happening. Namely, particles at the high end of the thermal distribution (the ",
"Maxwell-Boltzmann Distribution",
") are capable of tunneling through the coulomb barrier with a high enough success rate to enable slow, stable nuclear fusion.",
"In fact, that reminds of another interesting history story. Before tunneling was understood to be the mechanism behind nuclear fusion, it was believed that the sun was much younger than we now understand it to be. That's because, without the slow rate of fusion due to only the high end of the Maxwell-Boltzmann distribution fusing, fusion would proceed too quickly and deplete the star's fuel. The story that follows may be apocryphal, but supposedly biological evolutionists at this time had calculated how old the Earth must be in order to account for evolution to have occurred as it has. They came up with a number much closer to the real answer than physicists did, and confronted the astronomers!",
"Anyway, back to neutron stars. So in a typical star, the onset of fusion provides the outward pressure with which to oppose gravitational collapse, and the star comes into equilibrium. This is what we call ",
"hydrostatic equilibrium",
". However, once a star reaches a certain point, having fused through the lower elements, fusion is no longer energetically favorable. ",
"Here's",
" a beautiful graph explaining why that is.",
"At this point, the energy generated by fusion is insufficient to hold up the star's collapse against gravity. As it begins to collapse, it heats up, thus increasing the rate of fusion, thus collapsing faster, etc. This is a runaway ",
"positive feedback loop",
".",
"At this point you might be tempted to say the star is doomed and will continue to collapse into a singularity, that is, a black hole. It turns out that this is not the case! Because of the ",
"Pauli exclusion principle",
", which you may recall from your chemistry class, no two fermions can occupy the same quantum state simultaneously. Thus, as the star compresses further and further, eventually the fact that the electrons are \"pushing against each other\" in an effort to not occupy the same quantum state leads to an outwards pressure governed by ",
"this",
" equation. Now you've got yourself a white dwarf: a sub-stellar object supported by electron degeneracy pressure. Notice that I say sub-stellar object, but really this is a matter of semantics and some would maybe call it a star.",
"Similarly, if the star is so massive that electron degeneracy pressure cannot prevent further collapse, a different form of quantum degeneracy steps in: neutron degeneracy. We call an object supported by neutron degeneracy a neutron star. ",
"Interestingly, the ",
"Chandrasekhar Limit",
" places the upper limit on how large an object supported by electron degeneracy can be. An object larger than 1.44 solar masses will form a neutron star or black hole after collapse. Note that this is the mass after the star has blown all it's outer layers off, as happens when fusion ceases. A more realistic number then is that something of greater than 8 solar masses while fusing will become a neutron star or black hole.",
"An application of this is that our own sun is not massive enough to become a black hole or neutron star after it exhausts its fuel in ~5.5 billion years."
] |
[
"How can the Earth's magnetic field be so weak, yet so large?"
] |
[
false
] |
[deleted]
|
[
"I believe this has 2 main reasons: ",
"MRIs are generated by a machine in a room. The field strength of a dipole falls of proportional to 1/r",
". Meaning, it falls of very quickly. The field of Earth is generated in the liquid core, a region literally thousands of kilometers across. When the source itself is already that big, the distance over which the field falls of is much larger. That being said, the field on the surface is about 50 times weaker than the field in the core. ",
"https://news.berkeley.edu/2010/12/16/earth-magnetic-field/",
"\nThe second point is energy. There is a lot of energy in the magnetic field. There is much much more energy in the terrestial magnetic field than in the magnetic field of, say, a MRI."
] |
[
"This is pretty much correct.",
" ",
"The field is weak but there is a lot of energy in it. The magnetic energy stored in the Earths field is roughly (depending on approximations chosen) 10",
" - 10",
" J. This is equivalent to the world energy consumption of humans which in 2013 was 5.67 × 10",
" joules. ",
" ",
"What makes the field so weak is that the generation of the field is spread over a very large volume. What makes it so large is there is a lot of energy in it. What makes the MRI so strong is that it is generated in a small region but it is weak in comparison to the Earths magnetosphere if you consider how much energy is in it."
] |
[
"This isn't really correct. Earth's magnetic field in the core is only about 50 times stronger than on the surface. It is measured to be about 25 Gauss. That's weaker than the average fridge magnet. \n",
"https://news.berkeley.edu/2010/12/16/earth-magnetic-field/"
] |
[
"If you drink through two straws at the same time, do you get more liquid?"
] |
[
false
] |
(Cross-post from ) Having the discussion with a work colleague. I'm inclined to say that you get the same regardless, as the suction between the two straws combined is the same as through a single straw... The suction comes from your mouth, and you're (presumably) not sucking any harder! Is this correct? Is anyone able to provide any formula/answer to this? Edit:
|
[
"The viscosity of the liquid limits the amount that you can suck through a straw. Increasing the cross-sectional area that you can suck through alleviates this.",
"Think about it, would it be easier to breathe through a straw, or 50 straws?"
] |
[
"pretend it's a circuit and you have two wires in parallel vs 1 wire. You can essentially model pipes as resistors.",
"edit: formula for those interested\n",
"http://en.wikipedia.org/wiki/Darcy_friction_factor"
] |
[
"If you have enough suck force that the amount is limit by the diameter of the straw then yes you would get more. "
] |
[
"If you slowed an electron down in a vacuum and added a proton to the environment, would it spontaneously form a hydrogen atom?"
] |
[
false
] |
Or would the electron simply bind to the proton, or penetrate?. If so, then what force is it which compels the electron to accelerate to the appropriate speed to occupy the 1s orbital? What force is it that results in steric interference between functional groups which often dictate the most energetically favorable three dimensional chemical configuration?
|
[
"Yes, as the ground state of the hydrogen atom has 13.6 eV less energy than the separated electron and proton. The force which pulls it in and speeds it up is the coulomb force, as opposite charges attract. The energy difference will be radiated as one or more photons. "
] |
[
"Technically, sort of -- that's actually how the proton got its name, historically. The isotopes of hydrogen all have names:",
"The bare nuclei of each of these isotopes all get an -on suffix. So the nucleus of a tritum atom is called a triton, the nucleus of a dueterium atom is called a deuteron, and the nucleus of a protium atom is ... a proton. :)",
"You can also consider a free electron to be a hydrogen ion as well, kind of.",
"But, in most contexts (even technical contexts) such as this one, it is pretty unusual to refer to free protons or electrons as \"hydrogen ions.\" This is because, in general, ions are atoms, and atoms are considered to be a bound state between a nucleus and one or more electrons in a cloud. So either type of hydrogen \"ion\" isn't technically an atom."
] |
[
"Is a lone proton not already a hydrogen ion?"
] |
[
"How are motors cooled within a vacuum?"
] |
[
false
] |
Most open-air motors rely on convection-based cooling (whether passively or actively cooled). How do engineers overcome the lack of air-cooling within a vacuum (not space, but a low-pressure enclosure)? Higher heat-rated materials? Mount them to giant heatsinks? Different configuration/layout? I can't find anything online explaining how they achieve this.
|
[
"A lot of vacuum systems actually have the motor mounted outside the chamber and have a rotary feedthrough sealed with polymer gaskets. But a motor inside can be cooled by conduction--it's probably bolted to some metal anyway, maybe the chamber wall. Or it can be water cooled, by having water cooling tubes fed from outside the system. There are lots of other things in vacuum systems that require cooling, and it is common to use water cooling, but that's usually for things that dissipate a lot more heat than a small motor does.",
"If you had a motor in the vacuum, you would want to minimize heat dissipation in the rotor, and so have the windings in the stator--something like a stepper motor or a brushless dc motor. That way you don't need to get much heat out from the rotor. Whatever heat is dissipated in the rotor can get out through conduction through the bearings, or radiation from the outside surface of the rotor to the inside surface of the stator.",
"Is there any particular type of vacuum system, or application of the motor, that you are thinking of? Someone might know the specifics of that type of system and be able to comment more specifically."
] |
[
"There is no single solution, it will depend on the application. Two more options:"
] |
[
"Thanks for the reply. Could passively cooling them via copper heat pipes work as well i.e. having very many, but tiny vapor pipes within the stator core?",
"",
"The reason I am asking this is because I am curious about enclosing heavy duty motors within a vacuum and having no active cooling. I want to see how much of an efficiency increase you could get out of these motors (if it can even be adequately cooled)."
] |
[
"why is drinking a lot of fluids recommended for almost every disease?"
] |
[
false
] |
that.. how does it help getting better?
|
[
"Dehydration can exacerbate infectious diseases by hindering your immune system's ability to fight these diseases. Drinking lots of fluids basically ensures that you're not dehydrated. One less thing to get in the way of getting better."
] |
[
"Additionally your body's response to many diseases is fever, diarrhea, or loss of appetite, all which can lead to dehydration."
] |
[
"There are several different reasons.",
"The first is that many people don't ever drink enough water anyways... your pee should be a pale yellow. I can't count how many times I've seen patients give a sample of something resembling apple cider yet claim they drink a gallon of water a day. Uh, no... you're lying to me.",
"Next, many disease processes make you feel nauseous, have poor appetite, etc. and that further impacts water intake. People are likely to drink less water than the \"too little\" amount they already drink when they're sick.",
"So, we have established that people aren't drinking enough water... why do we care?",
"Well, you are basically 2/3 water. That's it. You need the stuff for almost everything. Dehydrating can lead to electrolyte imbalances within the cells (if you take out the solvent, the dissolved stuff reaches higher concentrations). Some diseases are hard on the kidneys, so you mitigate any damage by just diluting out the urine. In general, being able to flush out all the toxins that the bacteria bring with them is helpful. When you're sick, your blood vessels will dilate, so you need more water to fill up the now-expanded vessels in order to maintain blood pressure. You lose more water when you're sick... whether it's through insensible losses (sweating, breathing more rapidly/deeper, mucus production, etc.) or through overt losses like vomiting and diarrhea. There are a few other reasons that I do know but can't think of right now, but that should get the point across."
] |
[
"Are there any simulations of the ocean levels in case of global cooling available?"
] |
[
false
] |
I have managed to find plenty of ones for global warming, but I'm curious about how the world would look if significant global cooling would occur, such as might be caused by a super volcano eruption.
|
[
"I haven't been able to find what you're looking for but have found a related ",
"recently published paper",
" that looks at the brief deceleration of sea level rise (due to cooling) from the Mt. Pinatubo eruption in 1991. They estimate the eruption decreased sea level by 5-7mm, which is quite small compared to projections of anthropogenic sea level rise of >1m by 2100. I do not know how this scales with larger volcanoes.",
"Please also note that although volcanoes have a cooling effect due to the injection of aerosols in the atmosphere on 1-10 year timescales, the injection of greenhouse gasses (CO2 in particular) wins out on longer timescales. "
] |
[
"I hope I can help here: \nI believe a good place to start will be looking at the 1991 eruption of Pinatubo and the El Chichon eruption of 1982. These are two of the most climate altering volcanic events in recent history (with other notable examples). Volcanic eruptions in the tropics are more likely to effect the climate enough for short term climate altering. ",
"I don't believe a single super eruption would be enough to cool the Earth enough to alter sea levels, however, it is possible that a plethora of eruptions, in the tropics over a several year period, ~could~ change sea levels. ",
"Check out this paper for extra reading: Jevrejeva, S., Moore, J.C. and Grinsted, A., 2010. How will sea level respond to changes in natural and anthropogenic forcings by 2100?. Geophysical research letters, 37(7)."
] |
[
"It's also important to note that the climate change ensuing from a volcanic eruption is ",
" more short-term (because the aerosols and particulates that cause the effect are very short-lived) than climate change ensuing from long-lived greenhouse gasses like CO2. This is really important when considering sea level change because it means that the heat increase is essentially confined to the upper ocean, so only a very small volume of the ocean is susceptible to thermal expansion."
] |
[
"Why have so few transdermal medication patches been developed?"
] |
[
false
] |
Way back in the 90's the media made it seem like transdermal medication patches were the wave of the future. By now we were supposed to have a wide array of medical patches to choose from for all kinds of medications. Yet from what I can tell only a few have been brought to market. Is there some inherent problem or limitation with the delivery system itself? I have to imagine the demand is there for products that allow people to treat chronic illness without constantly remembering to take pills.
|
[
"This doesn't completely address the question, but transdermal medications can have variable efficacy in elderly patients, as their absorption through the skin is often dependent upon hypodermal fat. As people age, this fatty layer decreases. Considering a bulk of pharmaceutical use is among the elderly, it stands to reason that oral/injectable medications would be more ideal in treating chronic disease in this patient population."
] |
[
"Why would we want them? Pills are generally preferable. Transdermal medications generally have a slow time to onset, have to stay on for a while, and have variable absorption based between individuals and in the same individual over time (big increase in absorption during fever). You generally have to titrate them to effect."
] |
[
"Huh I didn't know any of that, thanks."
] |
[
"How is one's heart restarted after CPB?"
] |
[
false
] |
It is my understanding that one's heart is kinda stopped (asystolic) when cardiopulmonary bypass is performed. I understand that a collection of measures are taken in order for it not to die in the process. Now I know that a defibrillator won't ressuscitate a flat line, so how do cardiac MDs restart the heart at the end of surgery? An epinephrine shot and you're good to go? What about the rate of success of this procedure? Thanks!
|
[
"Med student here, these surgeries are really interesting and you ask a good question.",
"A patient that comes into the ED with asystole has a very different heart from a patient that has been placed on cardiopulmonary bypass.",
"By comparison, the heart that winds up in asystole in the ED has often suffered severe enough hypoxemia that the cells are no longer conducting electricity (as opposed to the uncoordinated beating that you see in most \"pulseless\" emergencies such as V. fib). This leads to the \"flat-line\" you see on the ECG and is generally pretty refractory to even the most heroic measures.",
"The patient undergoing a surgery with bypass will often have the heart muscle paralyzed through the use of high dose potassium. Now, this has the potential to damage the heart so I think most surgeons are starting to switch over to adenosine/lidocaine which has shown similar efficacy with fewer side effects (I'd provide links to research but I have UWorld open so I can't copy paste at the moment).",
"This heart muscle is still being oxygenated by blood from the bypass machine. Remember, the arteries that supply the heart with blood come off the proximal portion of the aorta.",
"So, you allow the myocardium to \"wake up\" from this chemical paralysis. Sometimes the rhythm is uncoordinated. Most cells in your heart have the potential to self-generate a beat. It's just usually the pacemaker that gets there first. If this is the case, defibrillation (basically shocking the entire heart to \"reset\" and give the pacemaker a chance to take over) is often enough to correct the issue.",
"Obviously a CT surgeon or Cardiologist would have more input than this, but I hope this helps some. "
] |
[
"Well, that corrects many things I was thinking!\nSo, in layman's terms, a \"flatline\" heart is basically dead, whereas a heart in CPB is merely asleep and resumes spontaneous function (coordinated or not, that is up to the defibrillator to correct) when it is awaken.",
"Thanks!"
] |
[
"sort of true, but not entirely. The heart muscle is usually NOT still being oxygenated by blood via the proximal aorta from the bypass machine. A separate cardioplegia circuit is run through the coronary circulation to dramatically cool and arrest the heart with addition of the high potassium solution you mentioned (also often chilled to reduce oxygen consumption by myocytes)."
] |
[
"How fast does a star collapse?"
] |
[
false
] |
Obviously, it takes billions of years to get to that point, but once the threshold is crossed, the tipping point, how fast is the process of collapse and explosion?
|
[
"In the case of the formation of a neutron star, the core collapses in mere seconds (or event less), while the outer parts will enter free fall and bounce back so that the actual explosion happens minutes/hours later. That's because the shock wave is regulated not only by the gravitational energy released during the fall, but also by all the nuclear reactions that ensue and hydrodynamical instabilities that develop.",
"Note that the neutrinos emitted during a supernova escape earlier that the light of the explosion, since they do not interact very much with the outer shells of the star and can go straight through. You will \"see\" the explosion once the shock wave reaches the surface of the star and disrupts it."
] |
[
"it takes billions of years to get to that point",
"Not necessarily, and in fact, almost certainly not. The bigger the star is, the harder gravity crushes it in, creating ",
" faster fusion rates compared to a small, cool star like the Sun. Stars big enough to end in core-collapse supernovas often have lifespans of just 10 million years, and some even shorter. Betelgeuse and VY Canis Majoris are both stars that are probably less than 10 million years old and are likely to undergo core-collapse supernova some time in the next 100,000 years."
] |
[
"They go through shorter and shorter cycles of fusing elements. First it takes a while to fuse all the Hydrogen into Helium, then it runs out of Hydrogen and starts fusing Helium, at that point star gets larger and less hot.",
"Anyway, it goes up the periodic table until it's like an onion where the core has the heaviest elements. Once the core is mostly iron... the fusion takes more energy than then it gives out. And the thing that was preventing the core from collapsing (radiation pressure) is no longer there and - caboom!",
"The stars burn through each successive element much quicker. For example by the time it gets to Silicon - it might only take a day to fuse it all.",
"These kinds of stars are rare, so we don't actually know how it all goes for 100%. Think we know Betelguise is going to go fairly soon because stars that massive do not live very long and it has random luminosity changes resulting from it shedding dust.",
"You might be better served Googling this yourself, it's an interesting star."
] |
[
"Why do pleural effusions occur more commonly on the right side?"
] |
[
false
] |
Why does this right-side predominance seem even more marked in cardiac failure?
|
[
"HenriSelmer is correct. Alot of this information is quite inaccurate.",
"\"Cardiac failure\" is too broad of a term and encompasses conditions that may lead to dramatically different symptoms.",
"Pulmonary edema associated with cardiac dysfunction is classically associated with left-sided heart failure. A common example would be ischemic cardiomyopathy which results in HFrEF where the left ventricle (LV) cannot efficiently \"pump\" blood, resulting in a increased back pressure. Decreased LV function results in increased left atrial (LA) pressures, which results in increased pressures within the pulmonary capillary beds. Once hydrostatic pressure exceeds osmotic pressure, there is net fluid flow from capillaries into the interstitium, resulting in pulmonary edema and perhaps pleural effusions.",
"In ",
" right-sided heart failure, pleural effusions and pulmonary edema does not occur frequently. A classic example is infective endocarditis in which vegetations on the tricuspid valve cause tricuspid regurgitation (TR). With TR, a fraction of every \"pump\" of the right ventricle actually flows backwards into the right atrium, meaning that there is less forward flow into the pulmonary capillary beds. It must be emphasized that the flow of blood is Right atrium -> Right Ventricle -> Pulmonary artery (PA) -> Pulmonary capillary beds -> Pulmonary vein -> Left atrium -> Left ventricle. Failure of the right side causes poor forward flow into the PA, making it impossible for there to be elevated pressures in the pulmonary capillary beds. Classic symptoms associated with right-sided heart failure include dyspnea / orthopnea / paroxysmal nocturnal dyspnea (from poor right-sided forward flow) and abdominal distension / anorexia / lower extremity edema (from increased central venous pressures).",
" must be emphasized, however since a common cause of right-sided heart failure is left-sided heart failure in which one can certainly observed pulmonary edema / pleural effusion. (Also of note, this infective endocarditis example is not perfect since septic emboli from the vegetation can lead to parapneumonic effusions)."
] |
[
"I question the premise of your title question. The most common causes of pleural effusions are congestive heart failure (CHF), malignancy, and parapneumonic effusions. Malignancy and parapneumonic effusions can easily cause unilateral effusions on either sides. I am not aware of a large preference towards right sided effusions with those. If you look at pleural effusions with respect to all etiologies, I believe that bilateral is the most common followed by right = left.",
"Looking at effusions due to CHF, bilateral is again the most common. However, there may be some slight preference for right-sided unilateral effusions due to CHF compared to left-sided unilateral effusions. (The Merck manual is saying 81% bilateral, 12% right-sided, left-sided 7%). I am not sure whether anyone really has a convincing explanation for why there would be a slight preference for one-side vs the other.",
"There are causes of pleural effusions, however, in which there is marked asymmetry of the sides. Hepatic hydrothorax, for example, is classically associated with a unilateral right-sided pleural effusion. This occurs in decompensated cirrhotics with significant ascites. Ascites move from the abdominal cavity into the thorax via diaphragmatic defects, which are more frequently found on the right side."
] |
[
"Pleural effusion itself is relatively rare, unless there's a serious underlying respiratory condition. I'd love to know where I'm wrong though if you'd care to explain"
] |
[
"The explosive yield of neutron star matter."
] |
[
false
] |
Okay, so we're always hearing the old canard, "a teaspoon of neutron star matter would weigh X billion tons if placed on the surface of the Earth." Well, neutron star matter is obviously not stable. If I had my handy magic teleporter and beamed a teaspoon's worth (let's say 5 cm of matter from a neutron star to say, my lab on the top floor of the Empire State building, just what would happen? Obviously you're going to get a pretty large release of energy, but just how large are we talking about? Is it like a stick of dynamite going off or is it "dinosaur-killer asteroid impact" big? Oh wise ask science, I beseech thee! Someone who's skilled with neutron stars and nuclear physics, what is the explosive yield of 5 cm of neutron star matter suddenly placed at atmospheric pressure?
|
[
"Well, neutron star matter is obviously not stable.",
"This is not obvious and I wish people would stop saying it was. Because we don't know the equation of state of the neutron star we can't comment on the stability at different scales. Neutron star matter, what ever it is, is incredibly stable on the scale of 10 km. There are some states of nuclear matter, such as strange quark matter, that do not depend on gravity for stability and may be stable at smaller scales (known as strangelets). ",
"As seen ",
"here",
" the strange quark matter equations of state (green lines) decrease in radius as the mass of the object decreases. The largest constraint on the equation of state is the observation of the masses of pulsars, which fall in a fairly narrow band around 1.35 solar masses. Radius is almost impossible to measure so all the equations of state are candidates. There is a recent measurement of a 2 solar mass pulsar, which rules out some equations of state (in that picture PAL6, GM3 and GS1), but everyone just has to tweak their models a bit and we'll be back in the same boat. "
] |
[
"Neutron stars are only 10",
" K at birth, if that. They cool to about 10",
" K in a matter of seconds. In a couple of years the core temperature is closer to 10",
" K and surface temperatures are closer to 10",
" K. "
] |
[
"The easiest way to do this calculation would be to assume the nuclear potential energy exactly balances the gravitational potential energy and that, were you to teleport your chunk of neutron star to the earth (with it's comparatively negligible gravitational field), all that energy would go into the explosion. The real answer is undoubtedly more complicated than this, since the equation of state and the mass-radius relation of a neutron star is not well know, I think this calculation will give you the right order of magnitude.",
"Most neutron stars have masses around 1.4 solar masses and radii around 10 km. So that yields an average density of about 10",
" kg/m",
" . Thus your piece would weigh (5 cm",
" ) * 10",
" kg/m",
" = 3 x 10",
" kg.",
"The gravitational potential energy of such a chunk of Neutron star near the surface of the neutron star would be -G(Mass of Neutron Star)(Mass of chunk) / (Radius of Neutron Star) = 6 x 10",
" Joules. ",
"That's 1.5 x 10",
" Megatons of TNT or about a trillion hydrogen bombs. ",
"Of course, that's how much energy you'd need to drag this chunk of the neutron star out of it's gravitation potential well, so there's no free lunch here (excepting, of course, your magic teleportation technology)."
] |
[
"Why do steam engines use water? Wouldn't it be better to use something that heats easier?"
] |
[
false
] |
Given that water has a very high specific heat (4.18), wouldn't it be easier to create a steam engine that runs on a liquid that is easier to heat up? All you need is the steam to move the turbine... Have they already created these engines?
|
[
"You actually ",
" a carrying fluid with a high specific heat, since you can transfer a lot of energy within a small temperature gradient and with a small mass of water. Using a medium with low specific heat capacity to transfer heat is akin to using a teaspoon to transfer gallons of soup - you either need a long time, or a lot of spoons.",
"For more, see ",
"this thread in r/sciencefaqs",
", as this is a frequently asked question."
] |
[
"The thermodynamic transfer of energy from steam to a turbine depends on the energy content of the fluid. Water, with its high specific heat, can transfer more energy per unit mass than most other liquids. In other words, if you were to use something like alcohol, which evaporates easier, you would need more alcohol to do the same amount of work"
] |
[
"Water vapour is lost during the normal function of a steam engine, presumably any liquid that heats more readily would be harder to obtain and as a result more expensive.",
"Simple availability."
] |
[
"What are the downsides to adding Lithium to people's drinking water?"
] |
[
false
] |
Apart from the social ramifications I mean. I only ask because doesn't say much.
|
[
"I know nothing about this topic, so I looked up and found some interesting things. (excuse my somewhat journey-like format)\nAs you found, it's amazing that\n",
"incidences of suicide, homicide and rape are significantly higher in countries whose drinking water contains little or no lithium...which suggest that lithium has moderating effects on suicidal and violent criminal behavior ",
"It took a decent amount of searching to find negatives. ",
"Obviously, ",
"overdosing on lithium is dangerous",
", but drinking water most likely won't have this danger, since it is not going to be at ",
"therapeutic levels of 300 mg",
" (more like µg levels per liter when in drinking water). ",
"This is a bit of extrapolation from the articles, but side effects from therapeutic lithium use includes",
"It's possible side effects like these can be acutely seen in drinking water levels. ",
"What does lithium do in the body, exactly?",
"Lithium readily forms salts that are used by the body in a number of functions. Among those functions are",
" Helping to control glucose metabolism\n Regulating the production of serotonin\n Dissolving excess uric acid in the blood and/or kidneys\n Facilitate the transmission of messages over neurons\n Affects the way that salt is absorbed in the body\n Assists in the absorption of folate and Vitamin B12\n",
"So changes in lithium levels can affect those processes. ",
"but in the end, here's the segment you were looking for:",
"While lithium at therapeutic (pharmaceutical) dosages has considerable side effects, there have been no noted side effects to supplementation with lithium at very low doses – up to approximately 2 mgs daily. Those levels are consistent with the amount of lithium consumed by people living in areas with soil and water naturally high in the trace element of lithium.",
"Seems like these low doses of lithium can only be good for the body. "
] |
[
"Lithium readily forms salts that are used by the body in a number of functions. Among those functions are",
"I'd like a proper source for this, because, to my knowledge, Lithium has no known biological role in the body. That is Lithium is ",
" a necessary metal ion for the body, and while it may have physiological effects (such as treating bipolar disorder) and is thought to lower the levels of myoinositol and inhibit inositol mediated signal transduction, it is by no means necessary for any of the processes in that list.",
"To that end I don't personally see why it would be necessary to add it to drinking water. It seems an awful lot like the government trying to control its citizens to me."
] |
[
"Li is also a teratogen - if pregnant mothers drank lithium-fortified water it would not be good. "
] |
[
"Are there any animals that have figured out how to \"practice medicine\" so to speak?"
] |
[
false
] |
An example would be if an animal discovered making a splint that would heal a broken bone or... somehow be aware enough of an ailment to eat a specific plant that helped it.. something like that
|
[
"Animals do eat certain plants to \"treat\" themselves, I'm not sure on the exact science of it but when a body needs something it'll start to smell it and seek it out, making it look delicious or making the body crave it. I once read about a guy stranded on a boat who caught fish to survive. After a while, the eyes started looking delicious to him so he ate them. Turned out there was some nutrient in the eyes his body lacked and that's how his body fixed it. The same would go for other animals, I'd venture to guess."
] |
[
"Some animals eat clay, which has detoxification effects. Of course, it's hard to say that the animals have \"figured it out\" though. I've heard of some new world monkeys crushing cyanide-producing millipedes onto their skin and using them as a bug repellent though."
] |
[
"Cats eating grass is a form of self-medication ",
"http://www.petmd.com/cat/wellness/evr_ct_eating_grass#",
".\nI would expect this applies to a number of animals. Numerous animals also lick their wounds which both cleans them, and provides natural antibacterials from saliva ",
"http://en.wikipedia.org/wiki/Wound_licking"
] |
[
"Turbulent to laminar flows?"
] |
[
false
] |
I've just started fluid dynamics so I'm not to sure but... for some flows through a pipe a laminar flow is desirable over a turbulent flow. For a lab in another class we used a wind tunnel and at the opening where the air enters, there is a honey comb cross section that tends to cancel out the velocities not normal to the cross section. Why couldn't this be used in pipes, like every x amount of meters add a little honey comb cross section to cancel out any non normal velocities?
|
[
"The first thing that comes to mind is that putting a collimator (what you are describing as a honeycomb), despite improving laminar flow, is going to increase resistance.",
"For the wind tunnel you don't care, it just means that your flux and windspeed are going to decrease a little. But for a pipe that means lower water pressure for a given pressure head."
] |
[
"Ah darn, well thanks for the answer."
] |
[
"Hey, Microfluidics! Grad student, professor?"
] |
[
"When we pop a joint like a knuckle or our back, its a realeases air. Where does that air go?"
] |
[
false
] | null |
[
"It dissolves back into the fluid. When you pop your knuckles, you're decreasing the pressure enough to allow the gas to escape the solution, which creates the popping noise. When you decrease the pressure again, it dissolves again. Think of a soda can; when you open the can you decrease the pressure and the gas escapes forcefully, creating a noise. "
] |
[
"does the gas in solution affect the function of the joint?"
] |
[
"No, the gas in the synovial fluid is completely normal and the popping of a joint is so transient that the gas does not affect mobility. All liquids in the body has some dissolved gas, especially blood. "
] |
[
"Can paradox's physically exist or are they a sign of a not fully understood subject?"
] |
[
false
] | null |
[
"You should define what you mean by paradox and/or give an example."
] |
[
"It depends on the definition. Some \"paradoxes\" are merely tricks of perception, language or notation for mathematics.",
"http://en.wikipedia.org/wiki/List_of_paradoxes",
"Logic would dictate that two mutually exclusive things cannot be both true at the same time. While we can never know everything it is important to note that in every such instance that has been resolved, one or both of the conflicting premises was found to be inaccurate.",
"These paradoxes most prominently exist in fields of study in relative infancy."
] |
[
"Logic doesn't necessarily exist in the real world. (I suppose it depends on what you define to make something exist, but the level of physical existence logic has is certainly less what my cellphone has. The useful thing about logic is you can kind of define things to be whatever you want and what you end up with is at worse useless nonsense it can still be logical (as long as it contains no contradictions(or as you call them paradoxes)).)",
"Paradoxes exist in logic.",
"The definition of a paradox is when two things that are mutually exclusive occur at the same time.",
"If two things occur at the same time they are not mutually exclusive and are therefore not a paradox. ",
"In the event that this happens we would say that the model we used to describe reality was not a perfect model of the things we were describing. I also don't think there is a logical model that can describe reality. Godel's Incompleteness Theorem seems to be powerful support for this."
] |
[
"So if your heart is always pumping New blood where's all the old stuff go?"
] |
[
false
] | null |
[
"You need to elaborate on that it didn't really seem to answer my question what happens then if it doesn't make new blood"
] |
[
"You need to elaborate on that it didn't really seem to answer my question what happens then if it doesn't make new blood"
] |
[
"So when you get cut and blood comes out of your body where does the new stuff come from?",
"And blood cells are cells they must die eventually right what happens to them or do they not die off eventually?"
] |
[
"As a bulb gets brighter, is it emitting more photons, or the same number with higher energy?"
] |
[
false
] | null |
[
"For LEDs, it's just plain more photons.",
"For an incandescent it's a bit more complicated. The range of energies of the photons it's emitting goes up, and it's emitting more of them. Since most of the radiation an incandescent emits is not visible anyway, what's sort of happening is that more of the light it emits becomes visible."
] |
[
"It depends on the distribution of photons. As pointed out by ",
"/u/corpuscle634",
", an LED simply produces more photons at the same bandwidth, but a thermal source like an incandescent lightbulb not only produces more photons when hotter, but more of them at higher wavelengths as well.",
"The number of photons emitted by an object thermally ",
"grows as T",
" or temperature cubed. The average energy of the emitted photons grows in T, or temperature to the single power.",
"Combined we get the Stefan–Boltzmann law which shows that the power emitted by the object grows with T",
"."
] |
[
"So an incandescent is a blackbody that goes from infra-red to red/orange/white/blue/ultra-violet as it heats up and gets brighter, and also produces more photons at each level?",
"Why or how are LED's different? Is an LED not a blackbody?"
] |
[
"Why are the front side of microwaves barely see-through. Why wouldn't manufacturers make them entirely see-through?"
] |
[
false
] |
[deleted]
|
[
"The metal mesh that obstructs your view is part of what is known as a Faraday cage. This prevents the microwaves from escaping the oven. Not only does this greatly increase the efficiency of the device, but it also prevents the microwave oven from completely rendering your 2.4 GHz WiFi network inoperable whenever it is turned on."
] |
[
"Just to add to ",
"/u/Rannasha",
"'s point, in an ideal Faraday cage you can cancel an electromagnetic field inside a \"cage\" by surrounding it with a solid, perfectly-conducting shell (which is why you lose cell service in a metal elevator). However, if you run the physics/math it's actually the case that the cage need not be completely solid in order to shield an electromagnetic wave, but rather can have holes PROVIDED those holes are much smaller than the wavelength of the EM wave you want to shield.",
"In a typical microwave oven the wavelength of the microwaves is about 12 cm. You can verify this by doing a little experiment by taking the rotating turntable dish out and sticking in something that is easily melted like a layer of cheese of chocolate and then turning the microwave on a little bit. You'll see regular nodes and anti-nodes of melting that you can use to measure the wavelength (there'll be two hotspots per wavelength, so there should be about 6 cms between them).",
"What this means is that a Faraday that is intended to shield microwaves of a 12 cm wavelength can have holes in it and still work provided those holes are much smaller than 12 cm. Thus the ~0.1 cm holes you see in the mesh."
] |
[
"Not only does this greatly increase the efficiency of the device, but it also prevents the microwave oven from completely rendering your 2.4 GHz WiFi network inoperable whenever it is turned on.",
"It also prevents the microwave from cooking you together with the food."
] |
[
"Is it possible to be completely motionless in space?"
] |
[
false
] |
Like, not pulled towards any gravitational body.
|
[
"Your question has a hidden assumption. What exactly are you motionless with respect to? There are no privileged frames of reference, so in a sense anything can be said to be motionless and it's everything else in the universe that moves.",
"But to answer the question you meant rather than the question you asked, there is no effective limit to the distance at which gravity can act so there will always be an acceleration between matter and they will not be at rest respective to each other."
] |
[
"Yes, sure (erm, propagate?), but that doesn't change the fact that ",
" there is no limit to the distance at which gravity can act on a body. All that gonzalez is saying is that theoretically, if you put two objects in space, no matter the distance, a gravitational force between them would manifest."
] |
[
"Doesn't gravity propagate at the speed of light?"
] |
[
"I was told by my father yesterday that there were \"no long term consequences\" to the BP oil spill in the Gulf. Does that ring true to what the scientific community is finding?"
] |
[
false
] |
I would surmise that there have been a number of studies done in and around that area, and I would love to gain some comprehension of the matter. Thank you in advance!
|
[
"The environmental geologists I've spoken with directly involved with the cleanup basically stopped finding oil and contaminants in the Louisiana marshes as soon as the tail end of 2010. The only real question remaining is the amount of contaminants remaining in the gulf. ",
"This spill was handled very differently than spills in the past. Cleanup efforts, in some ways, were much more effective and carefully executed than say, the Exxon-Valdez incident. Dispersants were used on the spill and the particles of oil were broken down into very small particles.",
"Now, these dispersants got rid of the oil slick extremely rapidly and the spill seemed to have been contained on the large scale. The problem with this is that the dispersants broke down the oil into such tiny particles that they were easily taken into the food chain of zooplankton, and from there contaminating other species. Mutations have been found in several species and large coral communities have perished. ",
"The long-term effects will be significant, but I don't think extremely detrimental to marine life as a whole in the gulf of mexico. "
] |
[
"I think it's important to distinguish that the dispersants did not make the spill go away. Rather, they broke up large slicks and made it more bioavailable to the bacteria that are naturally present in the Gulf that degrade the oil into non-harmful or less harmful compounds.",
"Another issue (though I'm not sure how well it could be studied in the field with the vast array of chemicals that were released from the spill and also to handle it), is the toxicity of the dispersants that were used. One of the primary dispersants used, Corexit, can induce headaches, vomiting, and reproductive problems in humans at high enough doses. I could only guess at what effects it has on marine life, but it is possible that these chemicals could add to the negative impact of the spill in that respect."
] |
[
"I am not sure why are you being downvoted... ",
"There actually are 190000 abandoned wells in Louisiana alone"
] |
[
"Is there a change in mass between a \"full\" battery and a \"dead\" battery?"
] |
[
false
] | null |
[
"Yes, but very, very slightly. A typical AA battery stores somewhere around 5400 joules of energy, which is equivalent to 6x10",
" kg."
] |
[
"Is this calculated using E=mc",
" ?"
] |
[
"But technically beyond that, an increase of bond energy equates to more mass. Not much at all, but still some."
] |
[
"If honey never goes bad, how is honey based alcohol made?"
] |
[
false
] |
[deleted]
|
[
"\"Regular\" honey is too hygroscopic for life; too much sugar, not enough water for life to grow. But when you dilute it, you change that ratio to the point that sugar and water are both available for life to grow in the medium. So yes, the sugars in the honey then do become the sugars that are fermented."
] |
[
"\"Regular\" honey is too hygroscopic for life; too much sugar, not enough water for life to grow. But when you dilute it, you change that ratio to the point that sugar and water are both available for life to grow in the medium. So yes, the sugars in the honey then do become the sugars that are fermented."
] |
[
"\"Regular\" honey is too hygroscopic for life; too much sugar, not enough water for life to grow. But when you dilute it, you change that ratio to the point that sugar and water are both available for life to grow in the medium. So yes, the sugars in the honey then do become the sugars that are fermented."
] |
[
"Has there been a noticeable increase in the growth rate of photosynthesising organisms due to human carbon emissions?"
] |
[
false
] |
My knowledge of photosynthesis is low to non-existent but i know it requires carbon dioxide. So would an atmosphere richer in CO2 cause faster growth in trees, plants etc.? If so has there been an increase in growth rates due to CO2 released by humans? Or are the effects of the increase in CO2 too small to notice or negligible in comparison to the effect of a changing climate on growth rates? Thanks in advance.
|
[
"I once thought that increasing CO2 would increase photosynthesis, which would in turn decrease CO2, giving us a nice balance. After taking a botany class, I realize that photosynthesis can't keep up with emissions, especially when you consider the affect of increasing heat. Photosynthesis slows with a minor increase in heat."
] |
[
"Yes, especially in desert regions. Plants have to open pores called stomata to absorb CO2, and in the process, lose water. When CO2 concentration increases, plants can absorb more CO2 while losing less water. In parts of the world where water is not a limiting factor, this doesn't make much difference, but in the desert, it's surprising.",
"See ",
"http://www.sciencedaily.com/releases/2013/07/130708103521.htm",
" for more info.",
"In findings based on satellite observations, CSIRO, in collaboration with the Australian National University (ANU), found that this CO2 fertilisation correlated with an 11 per cent increase in foliage cover from 1982-2010 across parts of the arid areas studied in Australia, North America, the Middle East and Africa, according to CSIRO research scientist, Dr Randall Donohue.",
"\"In Australia, our native vegetation is superbly adapted to surviving in arid environments and it consequently uses water very efficiently,\" Dr Donohue said. \"Australian vegetation seems quite sensitive to CO2 fertilisation.",
"This, along with the vast extents of arid landscapes, means Australia featured prominently in our results.\"",
"\"While a CO2 effect on foliage response has long been speculated, until now it has been difficult to demonstrate,\" according to Dr Donohue."
] |
[
"It can't keep up now because vast swaths of the planet are frozen and not photosynthesizing most of the year. That wasn't always the case.",
"http://en.wikipedia.org/wiki/Azolla_event",
"The Azolla event occurred in the middle Eocene epoch, around 49 million years ago, when blooms of the freshwater fern Azolla are thought to have happened in the Arctic Ocean. As they sank to the stagnant sea floor, they were incorporated into the sediment; the resulting draw-down of carbon dioxide has been speculated to have helped transform the planet from a \"greenhouse Earth\" state, hot enough for turtles and palm trees to prosper at the poles, to the icehouse Earth it has been since."
] |
[
"Is there any visual representation on how these creatures view the world?"
] |
[
false
] |
This was under and it said that mantis shrimp have 16 color receptors. What does the world look like to these things?
|
[
"Also, mantis shrimp are one of I think two known species (I believe the other is a kind of beetle) that are able to detect circularly polarized light (",
"original paper",
"). There was some hubub about this a while ago.",
"Many species can detect linearly polarized light, though.",
"EDIT: missing word"
] |
[
"There are a number of groups that analyze and catalog the sensory capabilities of many species. They probably inspected the signal response of various photoreceptors or perhaps directly analyzed the opsins (photo-sensitive chemicals).",
"Mike Land has is probably one of the better known researchers who made a career out of animal eyes. He has a great book about it - ",
"http://www.amazon.com/Animal-Eyes-Oxford-Biology-Series/dp/0198509685"
] |
[
"This image",
" shows absorption spectra of the photoreceptors for several mantis shrimp species (based on the depth that they live) as well as that of humans. They have more range and more types of opsins which should give them better discriminability of wavelengths.",
"Note that in humans the black dashed line is for our rods which work best under low light conditions. We essentially have two modes of vision - day (photopic) and night (scotopic). The difference in the absorption spectra for our day vision versus our night vision results in the brightness of objects relative to there surroundings varying depending on the surrounding light. This is called the ",
"Perkinje effect"
] |
[
"Why is COVID19 different than other global viruses?"
] |
[
false
] |
[deleted]
|
[
"SARS was far worse than the swine flu, Ebola, and the others you mentioned. And in its runtime of a little over year, it infected 8000 and killed less than 800 worldwide. No deaths in many countries where there were cases. Coronavirus, in just over 3 months, have over 150,000 cases. The death toll is almost to the entirety of the SARS outbreak’s confirmed cases, far higher than its death toll. In far less time. And with no sign of slowing down, in fact, we’ve seen exponential growth in countries like the US and Italy. Don’t live in fear, but be proactive and try to understand the severity of this"
] |
[
"Ebola is far more deadly (average 50% mortality but varies between 25-90% with various outbreaks), but it's also far less contagious. One of the major things about SARS-CoV-2 is that people can be asymptomatic (not showing any symptoms or only mild, cold like symptoms) while still spreading the virus to others. This doesn't happen with Ebola, which is only transmitted when symptoms start developing, with the symptoms usually being much more severe and noticeable. This makes containment of Ebola much easier, along with other factors which make it less contagious such as no airborne transmission.",
"We certainly did apply lots of major quarantine methods with Ebola though, ",
"here's a pic",
" of a nurse who was infected in Sierra Leone and then diagnosed after arriving back in the UK. The thing is though, due to Ebola spreading less easily, it was contained to Africa. There have only been 4 cases outwith Africa, all of whom contracted the disease within Africa and did not infect anyone else after leaving the continent. ",
"The places that have suffered Ebola outbreaks are places that aren't well developed, suffer from poor hygiene, and don't have the infrastructure/supplies to allow for mass lockdown/quarantine of people, as the people can't afford to stop working. It is treated very seriously though, with international aid supplied to these countries and healthcare workers required to follow strict rules about protective gear covering their entire body, and required to properly dispose of the dead."
] |
[
"Ebola killed 10,000 people,",
" and ",
"H1N1 killed at least 150,000 people by conservative estimates",
"."
] |
[
"Is there a minimum density that any liquid can be?"
] |
[
false
] | null |
[
"Yes, in that the term \"liquid\" implies a cohesive fluid - i.e. one that exhibits surface tension. If the density drops below a certain threshold (which changes for each substance and also by temperature) the liquid will sublimate into being a gas. ",
"It would be hard to figure out which liquid will be the least dense, but in general, it will be less dense for the lighter elements, the lower pressure and the higher temperature. My WAG would be liquid 3He."
] |
[
"Liquid hydrogen is about 6.7% as dense as water."
] |
[
"Could a single helium nucleus in a vacuum infinitely big be considered the sparsest substance?"
] |
[
"Does a particle with negative energy have a temperature of below absolute zero?"
] |
[
false
] | null |
[
"Whenever we must pay attention to the absolute value of energy, energy is always positive.",
"Also single particles cannot have a temperature. Temperature is a thermodynamic variable that is built in the thermodynamic limit, which includes sending the number of particles to infinity."
] |
[
"Just to expand on this, when a substance has a negative absolute temperature, it is hotter (in terms of the amount of energy it possesses) than absolute zero. (",
"Source",
")"
] |
[
"In my high school physics class, we defined heat as the average velocity of the particles, times this times that.",
"That's a really really wrong definition.",
"You can very easily have a 0 temperature system where the average velocity is nonzero,for example a gas of electrons."
] |
[
"Are Polygraphs statistically reliable?"
] |
[
false
] |
[deleted]
|
[
"What you've been reading is wrong. Polygraphs are not accurate, statistically or otherwise."
] |
[
"Polygraphs have been 'shown' to be statistically accurate by advocates for it's use ",
". When separate research was conducted by the National Academy of Sciences, they were found to be inaccurate and it was almost impossible to tell whether it was 'working' due to the nature of the device.",
"A quote from them",
"In 2003, the National Academy of Sciences (NAS) issued a report entitled \"The Polygraph and Lie Detection\". The NAS found that the majority of polygraph research was \"unreliable, unscientific and biased\", concluding that 57 of the approximately 80 research studies that the APA relies on to come to their conclusions were significantly flawed. These studies did show that specific-incident polygraph testing, in a person untrained in counter-measures, could discern the truth at \"a level greater than chance, yet short of perfection\".",
"In short, the answer is that anyone could 'beat' the Polygraph by simply being calm and showing confidence."
] |
[
"Just want to add to what ",
"/u/DaedalusMinion",
" said here. The reason polygraphs are so unreliable is because all they do is measure arousal. When you get nervous, you begin to sweat, your heart rate speeds up, and your breathing becomes more rapid and shallow. These are some things the polygraph measures.",
"The idea is, a person being dishonest will be more nervous than someone telling the truth, and thus will appear more \"excited\" on the polygraph. But here's the shortfall -- if you can confidently tell a lie, chances are your physiology won't change much. Conversely, if a question makes you really nervous before you even decide whether to lie or tell the truth, the polygraph might claim you are lying when you are actually not.",
"There are a myriad of other issues as well -- such as establishing a valid baseline across multiple uses -- but basically just keep in mind that polygraphs detect lies by proxy of how excited the person being measured is."
] |
[
"What happens in this theoretical universe?"
] |
[
false
] | null |
[
"If you have two objects of equal mass M kilograms starting a distance D meters apart from each other, it will take approximately",
"96167*D",
"/sqrt(M)",
"seconds for them to meet. So two objects which are one meter apart and are both one kilogram would take almost 27 hours to meet."
] |
[
"What about applying that formula to a much greater distance? Say the actual diameter of the observable universe? "
] |
[
"There is only a finite diameter of the observable universe because of expansion/dark energy, which you requested that I ignore. The two-body problem can't be solved exactly in general relativity, but the corrections to the Newtonian expression I gave above should be small if we ignore expansion, the distance is large, and the objects are small.",
"If you want to include dark energy, then the answer will then vary quite a lot from the Newtonian value as the distance gets comparable to the radius of the observable universe, and they would never meet if the distance was larger than this radius. I believe the time it would take for them to meet will go to infinity as their distance gets close to the radius."
] |
[
"Can a person be both fat and healthy?"
] |
[
false
] | null |
[
"Think of it like this: Can a person who smokes cigarettes be healthy? They can eat well, exercise, etc, but smoking is an independent risk factor for a whole plethora of diseases (various cancers, HTN, lung disease, etc). I would argue that someone who smokes, regardless of other health and lifestyle choices, is inherently unhealthy (even if they never go on to develop those diseases). ",
"Obesity is similar. On one hand, a lifestyle that leads to obesity (sedentary, poor diet, etc) is obviously unhealthy. But obesity is an independent risk factor for numerous disease processes (such as diabetes and joint problems), even in the background of a 'healthy lifestyle'. Is an obese person with a healthy lifestyle healthier than their KFC munching counterpart? Sure. Are they healthy? I'd say no. "
] |
[
"Fat is not a valid medical way of describing a patient. "
] |
[
"The definition of health is \"being free from illness or injury.\"",
"Okay, so being fat isn't an injury, but is it an illness? The definition of illness is \"a disease or period of sickness affecting the body or mind.\"",
"Again, probably not a sickness, but is it a disease?",
"Definition of disease: \"a condition [...] that impairs normal functioning and is typically manifested by distinguishing signs and symptoms\"",
"Being ",
" fat ",
" impair the body's normal functions (e.g. genitals covered by excess folds of fat/skin) but it doesn't necessarily impair normal functioning. (Additionally, what is normal?)",
"Being fat is definitely manifested by distinguishing signs-- more caloric intake than is necessary for average activity level.",
"People who are fat are also at a higher risk of developing obesity-related illnesses like hypertension, diabetes, and more.",
"Being fat could also impair normal mental functioning due to societal acceptance or being caused by an eating disorder. (But in that case is obesity simply the symptom of the untreated cause-- the disorder?)",
"If you weigh 270, jog 5 miles a day, can take staircases with alacrity, don't suffer from diabetes, hypertension, heart disease, sleep apnea, depression, or any other obesity-related illnesses then I see no problem with classifying yourself as healthy.",
"I'm 6'/350 at 26. I would say I'm unhealthy, currently-- I work at home and rarely exercise. I have weighed the same amount or very slightly less since my teens and would have considered myself healthy as I did exercise, I worked with my hands and body (construction and mechanics), played tennis and fenced. ",
"Since there's no real definition I think it's safe to say that obesity can be a side effect of unhealthfulness but is not on it's own an indicator of poor health. (Though it often is.)"
] |
[
"Why do females tend to be more flexible than males?"
] |
[
false
] |
This isn't always the case, but from what I've seen in yoga and gym classes it is most of the time.
|
[
"TL;DR: We're not sure; bulkier musculature due to more testosterone likely contributes to relative inflexibility in males, but the primary cause is still unknown.",
"It depends a bit on exactly what you mean by flexibility. A more useful term is range of motion, which is primarily dependent on ligamentous laxity, or how loose/stretchy the ligaments that tie bones together are. A secondary factor is muscular extensibility, or how stretchy a person's muscles are. We know that women generally have laxer ligaments, but we're not sure why. Women also have smaller, more extensible musculature due in large part to having less testosterone in their systems. It's been hypothesized ligamentous laxity may be related to estrogen levels, but so far ",
"studies",
" have shown no correlation between the two. The upshot of this is that all else being equal, hormonal differences determine muscular stretchiness, but we're still not sure what determines ligamentous laxity, and ligamentous laxity is the more important factor for restricting motion at most joints.",
"Social factors probably play a role too, but range of motion differences between genders definitely have their roots in physiology."
] |
[
"One theory is that it's because females have higher levels of a hormone called ",
"relaxin",
". That softens collagen and makes connective tissue more stretchy and flexible. Levels are highest during pregnancy, when it's believed to let the pubic symphisis relax and possibly make expansion of the uterus easier. But even outside pregnancy the hormone is present, and it may explain why females' ligaments are generally more lax than males'."
] |
[
"Are you sure? Males build muscle a lot more so they could very well be less flexible compared to women. And I don't think it's correct to think it's mostly from societal pressure.",
"Also ",
"this."
] |
[
"Can someone explain the difference between the Glycocalyx and the MHC classes on our cells?"
] |
[
false
] |
I'm in a microbiology course and my professor said the MHC classes are used for cellular identification with T-helper and T-cytotoxic. I understand this, but I also remember from my Anatomy and Physiology course that we briefly touched on the glycocalyx and that it was the "sugar coat" that allowed for adherence but also identification within the body. So my question is, what is the difference between the two or are they closely related?
|
[
"MHC stands for major histocompatibility complex, which you already know... when antigens are taken into a cell, the antigen is degraded into a specific peptide and then is loaded onto an MHC class I or II protein and the peptide:MHC complex is presented at the cell surface where it might bind to an antigen specific CD4 (helper) or CD8 (cytotoxic) T cell on its receptor. ",
"Glycocalyx",
" is a general term for the gelatinous layer on top of epithelial/endothelial cells and bacteria cells (bacteria do not express MHC in nature) containing proteins, polysacchs, and glycoproteins.. the glycocalyx environment might contain mhc"
] |
[
"MHC classes are specific for antigens and the glycocalyx is simply a general term for polysach and glycoproteins",
"That is correct. Disconnect the two terms from your mind when you hear either one you shouldnt think of the other. ",
"A memory trick. ",
"There are two types of MHCs, one on all cells and one only of specialized APC (antigen presenting cells). ",
"MHC class I is found on all cells (think One Love (Bob Marley))",
"MHC class II is only found on APCs (think 2/Too few, as there are fewer of these cells). "
] |
[
"Ah ok. So the difference appears to be that the MHC is the specific site where the antigen is presented on our cell, which could be contained on or in a glycocalyx but not necessarily? MHC classes are specific for antigens and the glycocalyx is simply a general term for polysach and glycoproteins. I think I get it now! Thank you "
] |
[
"Assuning two atoms are entirely alone in a hypothetical, empty universe, and seperated, would gravity eventually pull them together."
] |
[
false
] |
And approximately how long would this take, if possible to calcul/estimate? Assume they are very far apart; millions, perhaps billions of miles apart. Also, sorry for the typos. On my phone.
|
[
"No, not if the universe was expanding faster than the attractive force of gravity could compensate for. ",
"http://en.wikipedia.org/wiki/Future_of_an_expanding_universe"
] |
[
"It entirely depends on their initial velocity relative to their position. If you take into account of metric expansion, then in some cases the former is irrelevant.",
"For example, in a non-expanding universe, if there are two atoms, there can be 2 outcomes: they either come together via gravity, or they will never come together. The former is possible if the relative velocity is below the escape velocity. The latter results if the relative velocity is at or above the escape velocity.",
"And if you take into account metric expansion, there are some distances sufficiently far apart that the atoms will ",
" be able to come together, as their apparent recession is faster than the speed of light."
] |
[
"See ",
"escape velocity",
". If the kinetic energy of the particle is higher than the gravitational potential, it will never come together to the other atom. Remember, the further you are away from gravity, the weaker it gets (via the inverse square law). If your velocity is high enough, your speed will not decrease as fast as the gravitational force will, so you'll never stop and turn around."
] |
[
"Were ancient Egyptians aware the Earth is a sphere?"
] |
[
false
] |
This question comes up as I read somewhere that the Great Pyramid at Giza is aligned to magnetic North very precisely. I wonder what exactly could it mean for them to align a Pyramid in such a way...
|
[
"This source",
" says that it is aligned to true north, and that this feat was most likely achieved from observing the night sky. "
] |
[
"That's really quite a silly \"challenge\". The proof is in the pudding. You can't just assert \"There's no way that could be so accurate,\" because obviously there is a way. Don't be so quick to dismiss the power of astronomy, careful observations, and lots of time.",
"Regardless, ",
"this page",
" has one possible method for determining cardinal degrees, and ",
"this page",
" has another. "
] |
[
"You can't just completely dismiss academic history because you don't like the conclusions they've come to. An Egyptologist is the best person to answer this question, undoubtedly."
] |
[
"What are the pros and cons of having more or less bits in a byte?."
] |
[
false
] |
I was wondering why a byte is 8 bits, rather than perhaps 4, or 16, or 32 even. Surely having 4 bits in a byte would work just as well?, I understand that 8 bits are useful so you can fit all the keyboard symbols and other things, but wouldn't using two bytes have the same result since in the end it's 8 bits either way?. Would there be any disadvantage to using multiple bytes for each symbol or color in a pixel other than possibly being more complex to use?, and are there any disadvantages to going up to 16 bits per byte?.
|
[
"Which definition are you using for \"byte\"? I know of four.",
"the unit used in character encoding. That's the original definition. There have been 6 and 8-bit bytes by this definition. You can argue that the UTF-16 encoding of Unicode is using an 16-bit byte, but the definition falled into disuse before Unicode was established.",
"the smallest addressable unit of a computer (that definition is usually used only when it is more than one bit and less than one word; the C language is using that definition and doesn't assume than a byte is different from a word). That definition is derived from the first, as it make sense to be able to address character.",
"a bit pattern less than a word which can be handled in a word addressable computer. That meaning is used only for word adressable computers (so is somewhat exclusive from the previous one, at least when C is not concerned). Word adressable computer which had a notion of byte sometimes (usually? I'm not that knowledgeable about those obsolete architectures) could specify the width (the PDP-10 is in that case; it was commonly used with 6, 7, 8 and 9 bit bytes).",
"8 bits. ",
"What happened is that the first two notions of bytes converged to be 8 bits in most systems. The third definition felt into disuse as word addressable machines where reserved to special purpose usage and stopped to be used for character processing.",
"Why did it converge to 8-bit bytes? 6-bit bytes were too cramped for character encoding. 7-bit bytes were used for ASCII, but it was designed to be a standard for data exchange between brands of computer, not expected to be used internally and expecting that internally computers will not use 7-bit bytes (excepted machines like the PDP-10 with varying length bytes). 8-bit bytes were chosen by the first designers, and following one had no reason to second guess them as it was a good trade-off.",
"4-bits byte were considered -- BCD was a thing for the designers -- but it would allow to address half of the memory for the same address length, would force multi-byte handling for most character handling and that's a pain -- especially when you consider that assembly language was the norm them so packing two 4-bit BDC digit is a byte was deemed better if density of BCD was needed.",
"More than 8 bits was probably not considered (that reduce too much the density of text at a time when memory was costly).",
"Nowadays, changing the byte size would not be considered seriously by anybody. The assumption is too much ingrained everywhere."
] |
[
"other than the fact that only 7 real bits were ever required to represent a character of text.",
"This is more of a historical accident that computers took off in North America and western Europe before other places. ",
"If China had dominated computer development in the 40's - 60's, things might have been different.",
"I don't know why not 16, 32, etc. ",
"It's worth pointing out, for OP's benefit, that nowadays lots of processing is done in chunks of 16, 32, or 64 bits instead of 8 bits. We just haven't redefined the word \"byte\" to describe these things. Instead we talk about \"words\", \"double words\", and other such things since 1. most of our computers are still able to work with 8-bit bytes when needed, and 2. the definition of \"byte\" to mean 8 bits has become widely accepted."
] |
[
"So using more bytes is more resource intensive even when the number of bits is the same in the end?.",
"Interesting."
] |
[
"Why is an arc of a curve actually a straight line when at infinite zoom?"
] |
[
false
] |
When zooming in on a section of a curve (any curve and any section of the curve), as the zoom magnification approaches infinity, the curvature approaches zero.
|
[
"Basically, everything is a straight curve when you look close enough (except for pathological patterns designed explicitely to break this rule like fractal patterns). This leads to a lot of cases where we know some parameter x will be in a very close region around some center ",
" and we can approximate any function ",
" by a linear approximation: f(x) = ax + b\nThis is called a 1st order approximation because we replace f by a 1st order polynomial",
"If I'm not mistaken, a lot of complicated physics model are impossible to do calculations with and people replace the complicated real calculation with 1st order approximations (or n-th order if they want to be more precise) in order to \"solve\" the model mathematically",
"this attribute is purely mathematical: this is true for every smooth enough function (if a function has a derivative then it is smooth enough, but there likely is a weaker condition which I don't remember)"
] |
[
"It approaches zero, but it will never be zero. I think you're trying to over complicate this. 1/360th of a circle will have an angle of 1",
" from the origin., 1/720th 0.5",
" ",
"So essentially, for 1/x portion of a circle the angle will be x/360",
" from the origin. A straight line will have an angle of 0",
" from the 'origin' and as x/360 can't equal 0, while x>0, this will never happen."
] |
[
"When you zoom you change the scale.",
"The curvature is usually described by the radius of the curvature, the bigger the radius, the less curvy the curve is. The easiest curve with a defined curvature is a circle.",
"Now you look at the circle without zooming and it has a radius of R. When you zoom in by a factor of X, the scale changes so that the Radius is multiplied by X. If X goes to infinity, the scaled radius (i.e. X times R) also goes to infinity.",
"And an infinite Radius of curvature corresponds to a straight line."
] |
[
"What does it actually mean that the geometry of the universe is flat?"
] |
[
false
] | null |
[
"What we mean by \"flat\" in this context is not curved or warped. ",
"Here is what that looks like. Imagine you take 3 points, and you form a triangle with these three points as the vertices. Then, at each vertex, you measure the angles. If the angles add up to 180 degrees, that region of space is flat; if it's greater than 180 degrees, the space is positively curved, and if less than 180 degrees, negatively curved.",
"Now, how do you connect the vertices to form the triangle? They must be joined by lines, i.e., paths that are the shortest paths connecting those points (\"geodesics\").",
"Consider the following: The surface of the Earth is not flat. We can see this by taking as our three points the South Pole and two points on the equator. We join these by a line along the equator and two longitudinal lines. At the equator vertices, the sides meet at 90 degree angles, while there's an additional positive angle at the South Pole, and so the sum of these three angles is in excess of 180 degrees.",
"When we say space is overall flat, we mean on average over large scales, triangles you form will have 180 degrees. (Of course, there will be small areas where locally space is not flat.)"
] |
[
"Ah, I think I see what you are saying. If we were in a universe that was spherical, the shortest path between two points would be some sort of curved path? "
] |
[
"That works for positively curved space, but not negatively curved space. Hyperbolic space has constant negative curvature, and also has pairs of lines which never cross."
] |
[
"260/230 values for measuring nucleic acids using a nanodrop, when is it too high?"
] |
[
false
] |
I extract genomic DNA and quantify it using a nanodrop spectrophotometer. The manual says accepted 260/230 readings for "pure" DNA should be between 1.8 and 2.2. When I find a sample that has a reading below 1.8 I re-purify it and measure again. The thing is that sometimes I'll get readings of 2.3 and higher (no more than about 2.8). I would like to assume this just means I'm super amazing and have reduced the amount of contaminants to practically nothing and I have super pure DNA. I would like to get some opinions/discussions from other people relating to this topic. What should I consider to be too high? Could these high readings relate to problems with the DNA itself?
|
[
"Found that the tubes I was using were leeching colour into my samples once... that looked kinda funky when speccing. "
] |
[
"I use the Qiagen Puregene blood/bone marrow extraction kit. I don't have a spectrograph with me right now but if I remember I can grab one tomorrow. The graphs are very smooth and beautiful, I can tell you that. Its just that after I re-purify the sample the 230nm reading is much lower but the 260nm reading is about the same. Higher if I concentrate the sample (obviously) and lower if I lose a little bit of the DNA pellet.",
"I know most proteins typically absorb at 280nm, that's why we use the 260/280 reading to estimate nucleic acid purity in relation to protein contamination. My 260/280 readings are always between 1.8 and 1.9 so I'm not concerned about protein contamination. Are there proteins that like to absorb at 260nm?",
"I'm very careful to allow all EtOH to evaporate before I rehydrate the sample at the end. I always check the DNA pellets to make sure they're dry. I also did an experiment to see just how much EtOH would affect the readings and after adding 10ul EtOH, the readings were only affected (throughout 10 samples) about + 0.2. ",
"If you have any more insight I would appreciate it. Thanks for the response!"
] |
[
"I use the Qiagen Puregene blood/bone marrow extraction kit. I don't have a spectrograph with me right now but if I remember I can grab one tomorrow. The graphs are very smooth and beautiful, I can tell you that. Its just that after I re-purify the sample the 230nm reading is much lower but the 260nm reading is about the same. Higher if I concentrate the sample (obviously) and lower if I lose a little bit of the DNA pellet.",
"I know most proteins typically absorb at 280nm, that's why we use the 260/280 reading to estimate nucleic acid purity in relation to protein contamination. My 260/280 readings are always between 1.8 and 1.9 so I'm not concerned about protein contamination. Are there proteins that like to absorb at 260nm?",
"I'm very careful to allow all EtOH to evaporate before I rehydrate the sample at the end. I always check the DNA pellets to make sure they're dry. I also did an experiment to see just how much EtOH would affect the readings and after adding 10ul EtOH, the readings were only affected (throughout 10 samples) about + 0.2. ",
"If you have any more insight I would appreciate it. Thanks for the response!"
] |
[
"What would be the effects of someone's body being completely flipped, like in a mirror?"
] |
[
false
] | null |
[
"All your new d-isomer amino acids are no longer compatible with the L-amino acids in your food, so any new proteins you try to synthesize from a mix of the two will flop around uselessly."
] |
[
"A good home for this question would be ",
"/r/AskScienceDiscussion",
"."
] |
[
"Is this too speculative or open-ended for ",
"/r/askscience",
"? I'll remove it and post it there if it is."
] |
[
"When an atom is split is the energy released coming from the gluons?"
] |
[
false
] |
Gluons seem really interesting, I've learned that they provide 99% of the atoms mass but somehow Higgs get a lot of credit for their 1%. It just got me thinking about gluons, after googling the subject it all seems pretty vague.
|
[
"You may have heard that \"99% of the mass of a nucleon comes from gluons\", but that's not really true. There are no ",
" gluons involved. Hadrons (including nucleons) are bound states of QCD (the theory of quarks and gluons). In the low-energy regime, where bound states exist, strong interactions are ",
" strong. You can imagine quarks inside the hadron exchanging virtual gluons when they interact, but due to the strength of the strong force, this isn't really a good approach, because the strong force is non-perturbative. That means that if you try to expand the amplitude for some process into an infinite series of Feynman diagrams, diagrams with ",
" internal lines contribute ",
" than diagrams with fewer internal lines. So that means that you can't just truncate the series at some desired order, because the terms ",
" and the series doesn't converge.",
"So perturbation theory is not a good approach to studying bound states of QCD. The alternative is to use functional integration. This is an extension of Feynman's path integral formulation of quantum mechanics to quantum fields. But formally speaking, in continuous spacetime, this would require carrying out an infinite-dimensional integral to calculate any kind of observable quantity. So instead of working on a continuous spacetime, you work on a discretized spacetime \"lattice\" instead. This is lattice QCD, and it's how calculations in low-energy QCD are ",
".",
"Anyway, in these kinds of calculations (for example: calculating the mass of a proton), you're integrating over all possible configurations of the quark and gluon fields. And the majority of the contribution to the nucleon mass comes from the strong interactions between quarks and gluons rather than the rest masses of the quarks themselves (which come from the Higgs).",
"This makes up the masses of individual nucleons. Then you bind nucleons into a nucleus, and the mass of the nucleus is the sum of the masses of all the protons and neutrons, minus some contribution from the binding energy due to the residual strong force between nucleons. ",
" is what is released in exothermic nuclear reactions.",
"During a nuclear reaction, the mass of a nucleon doesn't change. However nucleons are rearranged within the nuclei involved, which either costs or releases nuclear binding energy. This binding energy comes from interactions ",
" nucleons, not interactions ",
" nucleons.",
"Although the strongest contribution to the forces between nucleons is ultimately due to the strong force as well."
] |
[
"The way that the calculation is carried out requires you to integrate over all possible configurations of the gluon fields. So even though they won’t in general have zero value at any given part of the calculation, that doesn’t mean that any physical gluon has been produced. There are no real (physically observable) gluons inside of a nucleon. So in this kind of calculation, the gluons are more of a mathematical artifact."
] |
[
"Wow, thank you for your in depth reply. I should have realized it was more complex. I'm still a bit unclear of the kind of unrealness of the gluons, are they an emergent property of the interactions between the particles, like a wave in liquid say, or are they a mathematical construct like a grid to visualize position. Thanks again for taking the time to explain this stuff."
] |
[
"How can a proton and a neutron weigh roughly the same when a down quark is twice as massive as an up quark?"
] |
[
false
] | null |
[
"Think about this: the quarks are each about 3-6 MeV/c",
" . But the proton or neutron weighs ~940 MeV/c",
" , so nearly all the mass of the proton comes from the strong force binding the quarks together, not the actual quark masses themselves."
] |
[
"Imagine you have two photons flying away from each other with equal momentum. Now, you could perhaps boost along the direction of one photon, giving it less apparent momentum and energy, but in so doing, the other one appears to gain momentum and energy. So while each photon individually is massless, the system of 2 photons has some invariant mass quantity associated with them. And this holds as a general proof in fact, for any two non-collinear photons, a center of mass term can be found. Now we can extrapolate this concept to a kind of \"thermal\" motion. A bunch of particles moving randomly about, massless or not. Any shift of my frame of reference says that some particles will gain momentum, and some lose it, but since the motion is randomly oriented, there is an associated mass of thermal heat itself (ie a hot object has more mass than it does when the same object is cold).",
"So now back to hadrons (any bound system of quarks). Even though the gluons are massless, there is a ",
" of gluons, and more generally a system of gluons and \"sea quarks\" (quark anti-quark pairs that are a part of this strong force binding). And it's that ",
" of particles with non-uniform motion that has some mass term associated with it. ",
"What's even more remarkable is that while people often refer to the Higgs field as giving mass to everything in the universe, it only gives mass to fundamental particles. But as we see here, ",
" of the mass of a proton or neutron, and thus most of the mass of any atomic matter comes not from fundamental particles but from strong force binding energy. "
] |
[
"That is how it was initially developed but it was extended to also explain the masses of the fundamental fermions as well"
] |
[
"Can there be amorphous gas?"
] |
[
false
] |
As i understand amorphous solid doesnt have a set melting point rather it gets more liquid as hotter it get like butter. This got me thinking are the amorphous gasses/liquid, like liquid that loses its viscosity gradually and eventually it becomes gas? Or is it impossible to such material to exist?
|
[
"Some added context: amorphous in materials science just means \"not crystalline.\" A crystalline solid is one whose structure repeats, like a tile floor. An amorphous solid would be like a tile floor made of irregular pieces.. they fit together as well as they can, but not perfectly. That can lead to a \"smeared\" melting point because the individual atoms are in different micro environments, so they become liquid at slightly different temps. Liquids aren't going to do this in any observable way because they tumble around so quickly that they experience an average of their possible micro environments. Does that make sense? I can go deeper in the weeds if you like."
] |
[
"The closest thing to what you are describing is called supercritical fluid. It is a phase with temperature and pressure so high that there is no meaningful distinction between liquid and gas. You can find several videos showing its formation with carbon dioxide on YouTube."
] |
[
"I wonder, does a supercritical fluid have to fill it's container? Liquids can sit on the bottom of a container, so if you had a vessel with both supercritical co2 and some other gas that withstood the pressure, would the co2 sit on the bottom, or mix with the gas?"
] |
[
"How we know certain animals can detect specific scents from X distance away? How are we measuring and determining that?"
] |
[
false
] |
You'll often hear in a nature documentary that a given creature can detect the scent of Food X from ABC miles away, i.e. creatures on the steppe smelling fresh growth from 100 kilometers away or sharks detecting a drop of blood from a quarter mile away. That sort of thing. This is fascinating, but how do we KNOW that? What experiments have we done, observations have we made, and measurements have we taken to determine that these numbers are accurate? It would be difficult to have control groups and the like in the wild, so presumably this is all down to observation, but I'd like to know more about the methodology of determining this stuff (and yes, I understand it likely differs from case to case).
|
[
"The premise is to put a scent of a known strength (or measure the strength) and place it at increasing distance from an animal. For instance, putting a ball of crap a certain distance from a dung beetle and seeing if it finds it.",
"http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2311.1980.tb01139.x/full",
"If the animal is trained, it would be a lot easier, since you can train them to respond in an obvious way, so it could be done similar to a hearing test for humans. If you hear a beep, raise your hand/paw. Without training, it would require more repetitions.",
"http://www.mdpi.com/1424-8220/8/4/2208/htm",
" (In this case, it's finding a turtle instead of raising a paw, but obviously there's loads of different studies using different approaches for different goals with dogs.)",
"In the wild, scent \"traps\" are used, then sampling the response over time, compared to a control.",
"http://www.publish.csiro.au/am/AM11034",
"We can also extrapolate from the use of scent. If an animal uses scent to mark the borders of its territory, then we can assume it would evolve to make sure any interloper would be almost guaranteed of encountering a scent marker, so... Just measure the distance between them (and divide by two, and that'd be a reasonable standard for average scent ability).",
"http://onlinelibrary.wiley.com/doi/10.1111/j.1469-7998.1984.tb05050.x/full"
] |
[
"The distances for sharks is usually expressed in miles. They aren't building controlled tanks miles long. And some shark species have never been maintained in captivity for any length of time to perform such experiments. "
] |
[
"With sharks, maybe they have them in a controlled tank and they put a drop of blood in from a certain distance away and move it closer and closer and when the shark starts swimming that direction, they know it’s been detected?"
] |
[
"What will happen if I don't eat protein in a few hour span before and after exercise?"
] |
[
false
] | null |
[
"As I understand it your body uses protein to rebuild muscle tissue. If you don't have enough protein in you it would take longer to heal, thus making your work outs less efficient. "
] |
[
"So the question is how much does timing matter? What if I have enough protein, just ingest it ~18 hours before the workout and 3 hours after the workout.",
"Assuming that the amount ingested ~18 hours before as well as what was 3 hours after are both adequate daily amounts."
] |
[
"Your body would digest it well before the 18 hours passed. ",
"There's a lot of debate when it comes to how best to work out. The one thing most people agree on is to take whey isolate protein 1 hour before working out and within 20 minutes after."
] |
[
"Are fruits and vegetables really less nutritious now then they were -- years ago?"
] |
[
false
] |
[deleted]
|
[
"Is that really true?",
"Yes",
"Where is that data coming from?",
"Here's the first scientific paper I found, but it looks like there are others.\n",
"Changes in USDA Food Composition Data for 43 Garden Crops, 1950 to 1999",
"\nDonald R. Davis, PhD, Biochemical Institute, The University of Texas",
"If true, what are the reasons?",
"From ",
"Seattle Pi",
"\"Growing bigger tomatoes and ears of corn leads to a bigger yield for the producer, but the trade-off is the lower nutritional value.",
"Some say the gutting of the nutritional value of what we eat could affect public health, particularly in poorer countries. \"There is no sinister villain behind this,\" said Chuck Benbrook, chief scientist for the Organic Center, which commissioned the report. \"Increasing the amount of food grown per acre, by itself, is a good thing.",
"\"The problem is that until recently, no one ever checked to see what was happening to the nutritional value of these much larger tomatoes, bigger grapefruit and the rest of the crops.",
"\"Now we're in trouble. Not just the U.S. but almost every Western country that is using improved growing methods,\" Benbrook said.",
"Because of the work of plant scientists and crop breeders, farmers have doubled or tripled the yield per acre of most major fruits, vegetables and grains over the past 50 years.",
"Agriculture's \"almost single-minded focus on increasing yields created a blind spot\" in nutritional content, said Brian Halweil, author of the Organic Center's report, \"Still No Free Lunch.\"",
"\"Almost more alarming, this decline has escaped the notice of scientists, government and consumers,\" wrote Halweil, a senior researcher at the Worldwatch Institute and a member of the Organic Center's scientific advisory board.",
"Nutrient decline is also found in some organic crops.",
"\"I wish I could say that there is no loss in organically grown crops, but that's just not the case,\" Benbrook said.",
"\"Organic farmers face the same laws of nature and economic pressures as conventional growers, and pushing yields upward often increases profits.\""
] |
[
"Awesome. Thank you!"
] |
[
"A relevant opposing viewpoint.",
"http://www.youtube.com/watch?v=6Jq4DGEn9Is"
] |
[
"Is there any seismic activity on the Moon?"
] |
[
false
] | null |
[
"Yes there is, but it is significantly weaker than on earth. In fact the Apollo 11 crew placed ",
"seismic detectors on the moon",
". The following ",
"Apollo missions 12, 14, 15 and 16",
" placed further detectors.",
"The moon-quakes are typically about 2 on the Richter scale with a typical depth of 800-1000km. There are about 100 per year and most are assumed to be caused by tidal forces. There were however a series of stronger moon-quakes occuring at shallower depths reaching as high as ",
"5.5 on the Richter scale",
".",
"Also, the data collected from the Apollo era instruments has been reanalyzed with modern computational methods to show the existence of a ",
"core system similar to Earths",
"."
] |
[
"The moon's surface is covered by basaltic lava flows (the \"seas\" on the moon's surface are these lava fields) from volcanic activity that occurred billions of years ago. There are also silicate lava domes visible on the surface that formed much more recently than the basaltic lava fields (ca. 800Mya).",
"Images of silicate lava domes captured by the LRO"
] |
[
"If it has a similar core and seismic activity, why aren't there volcanoes on the moon?"
] |
[
"What happens when you get struck by lightning in the ocean underwater? (More Info Inside)"
] |
[
false
] | null |
[
"Previous discussions on ",
"r/askscience",
":",
"What happens when lightning strikes in the ocean?",
"When lightning strikes the ocean, how far do the effects of the electricity go?",
"How close would lightning have to strike to you in a body of water to fatally shock you?",
"What happens to marine life when lightning strikes the ocean?"
] |
[
"How can you let this part go:",
"And it makes sense because water is a good conductor of electricity.",
"I prefer my water at 18 MΩ-cm"
] |
[
"Water is actually a really bad conductor of electricity. You're a much better conductor, that's why it's a bad idea to go near water. "
] |
[
"How does the additive color system work with regards to superposition?"
] |
[
false
] |
Hi, For example, see graph. In the additive color system, Red and Green makes Yellow. In chart, that means that 550nm and 700nm waves of light add to yellow (600nm). Now, pure yellow has a wavelength of 600nm. I am under the impression that this means that pure yellow light would be a sinusoid with a wavelength of 600nm. However, you can see from the chart that the superposition of the 550 and 700nm wavelengths (blue) is a more complex waveform than the pure yellow (red) waveform. Is this purely a biological thing? For example, we have red, green, and blue light detectors on our retinas and the frequencies are averaged? This doesn't match the chart, as the average between 700nm and 550nm would be 625nm. So, would this virtual yellow be slightly different, visually, from pure yellow? Edit - Reddit broke the google link, what I pasted into the box was But the first link above goes to the same spot.
|
[
"The superposition of 550nm and 700nm light does not create 600nm light, physically speaking. The resulting wave would instead just be a superposition of the two component waves, i.e., E = Aexp(i[k",
" x - w",
" t]) + Bexp(i[k",
" x - w",
" t]), where E is the electric field vector, k is the wave vector, and w is the frequency.",
"The fact that 550nm + 700nm is perceived as yellow is more or less just coincidence and doesn't have to do with us having evolved to see the average of two wavelengths. In ",
"this additive color chart",
", blue and red combine to create magenta, which is not only not the average of 400nm and 700nm, but doesn't actually correspond to a color on the electromagnetic spectrum at all. Thus, you can't just write a function where you input some combination of light wavelengths and get out a perceived wavelength. White is another example where the averaging idea would break down.",
"Instead, our perception of colors is depends at first on the three different ",
"cone photoreceptors",
" in the eye (which have peak sensitivities at 430nm, 540nm, and 570nm). Because the sensitivity functions are actually spread out instead of sharply defined, one wavelength of light usually activates multiple photoreceptors. A 490nm light wave, for example, will activate a blue cone just as well as a red cone. Further, since cone photoreceptor sensitivity functions have two sides, there are actually two wavelengths that will activate any given cone to the same degree (unless the wavelength is the peak sensitivity). In downstream visual processing, perceived color signals are often determined by comparing the differing activation levels of the three types of cones in a certain part of the visual field."
] |
[
"Yes. If you can't perceive a difference, then your photoreceptors are being activated in the same way, even if the physical composition of the light is different in the two cases. ",
"Note: this isn't entirely correct, as downstream color processing in the visual cortex plays a big role in perception, as can be noticed in many color illusions like ",
"this",
". But assuming the same backgrounds and surrounding visual field, identical perception should correspond to identical photoreceptor activation."
] |
[
"Basically, yes. Our brain can only know how much each kind of receptor is being activated. But monochromatic yellow light would induce less of signal in the \"blue\" photoreceptors than a combination of green and red monochromatic light, because the green component of that combination would excite the \"blue\" cones more than yellow monochromatic light would.",
"So you wouldn't be able to distinguish any difference in color between something that emitted a combination of red and green monochromatic light and something that emitted yellow monochromatic light with a small but appropriate amount of violet/blue monochromatic light, or on the other hand any other number of emission profiles that stimulate those three types of receptors in the same absolute and relative amounts."
] |
[
"After seeing this picture of Saturn as taken by Cassini, wondering why, exactly, the pole is shaped like a hexagon?"
] |
[
false
] | null |
[
"So there was initially some excitement several years ago when ",
"a group reproduced a hexagon",
" in the laboratory using a ",
"spin tank",
".",
"However...they were only able to make their hexagon in a spin tank as a vortex-supported shape, with ",
"one vortex on each side",
". As a result, most of the giant planet community thinks that experiment is probably bunk - the real Saturn doesn't actually have those supporting vortices. Using the VIMS instrument on the Cassini spacecraft allowed us to peer down pretty deeply around the Hexagon, yet no sign of these vortices was ever seen. So, this might be a case of being right for the wrong reasons.",
"Since then, other groups have been able to run ",
"climate simulations reproducing the Hexagon as a standing wave",
", no vortex needed. This matches our observations of the actual Hexagon much more closely, so we think it's a lot more likely to be the correct explanation. ",
"The basic idea is that atmospheric flow is confined to a narrow latitude strip in this region - if it wanders too far north, it gets pushed back south by the Coriolis force; similarly, if it wanders too far south, it's pushed back north again by the Coriolis force. This channel has a natural resonance frequency dictated by the length and width of the channel, as well as Saturn's rotation rate and the change in east-west wind speed across the channel. Finding out which frequency of ",
"Rossby wave",
" is the most resonant in the channel is a deeply non-linear problem - basically impossible to do on paper - but you can enter all the starting info into a climate simulation, run it, and see what pops out. The natural tendency is that wavenumber 6 is the strongest mode in the channel - which naturally forms a hexagon when you loop the channel around a tight circle."
] |
[
"Snazzy. Thanks."
] |
[
"Snazzy. Thanks."
] |
[
"What food would humans be limited to if we didn't cook/prepare it? Would it be healthier to switch back?"
] |
[
false
] |
[deleted]
|
[
"all I have to offer:",
"I remember reading that the ability to eat food that was previously indigestible changed our evolution, ",
"this was allegedly due to the introduction of cooking, which could break down food. then when we ate it we had to put less energy into digestion and that freed up energy that could have been used to from brain growth/development"
] |
[
"Anthropologically, the paleo diet is bunk. Dietetically, I can't speak to it.",
"We've been eating grains far far longer than we've been farming them. Some of the very earliest artifacts are grinding tools with grain residue, from tens of thousands of years before grain cultivation likely started.",
"Second, the idea that we couldn't have adapted in the last few thousand years is silly. Lactose tolerance has arisen since the dawn of agriculture.",
"For a pretty interesting argument giving even more reasons the paleo diet is a bit silly anthropologically, you might read Milton's \"Hunter-Gatherer Diets\" here: ",
"link",
"."
] |
[
"Interesting, but this idea that \"natural\" things are better for us is just hippie bullshit. "
] |
[
"When I turn the lights off in my office, my speaker makes a clicking noise. If it is caused by changes in electric current, shouldn't the surge protector prevent the noise?"
] |
[
false
] |
It only happens for that one switch, and only when the switch is being turned off. a recording.
|
[
"The electrical noise is likely being picked up from the air, the original electrical pulse being broacast clear up to the radio-frequency range, maybe as a magnetic pulse strong enough that it's able to electromagnetically couple to the speaker's circuitry. If it is coming in through the power wires, a surge protector won't even see it until it hits several hundred volts, while a line filter might help block it."
] |
[
"Ok, that makes sense. But why would it only pick up on-off pulses and not the other way around?"
] |
[
"Suddenly disconnecting a charged inductor (like in the ballast of a flourescent light) will create a large voltage potential across that inductor. If this voltage is not properly handled it can create a spark that causes radio interference \"from DC to Daylight\". That might explain why it only happens during the on to off transition."
] |
[
"If restasis reduces immune function in eyes, will it help with contact lens rejection and irritation?"
] |
[
false
] | null |
[
"Good question, It may help a bit, but contact lens rejection is related more to an allergic type response to the proteins deposited onto the contact lens. So the allergic response is a rapid bombardment of inflammation were as Restasis was developed to deal with chronic low grade inflammation of dry eye. That help?"
] |
[
"I don't think anyone has a clear understanding on how Restasis increases tear production, but they say it does. I also think that improves the goblet cell count on the anterior surface.",
"Steroids like Lotemax are the best treatment for giant papillary conjunctivitis, and there are some lenses that are less prone to protein deposits than others. Unfortunately after the condition is developed its much harder to wear contacts comfortably. This is why compliance with wear-schedule and close contact with your optometrist is important while wearing contacts."
] |
[
"I don't think anyone has a clear understanding on how Restasis increases tear production, but they say it does. I also think that improves the goblet cell count on the anterior surface.",
"Steroids like Lotemax are the best treatment for giant papillary conjunctivitis, and there are some lenses that are less prone to protein deposits than others. Unfortunately after the condition is developed its much harder to wear contacts comfortably. This is why compliance with wear-schedule and close contact with your optometrist is important while wearing contacts."
] |
[
"Are there any studies who focus on and explain cultural reappropriation?"
] |
[
false
] |
I was talking about rap with a couple friends this weekend and wondered why white suburban kids were so enthralled by inner city black culture, wich is pretty much the polar opposite in the north american context. What would explain this attraction? Also, is there a link between the level of comfort on group of people have and their tendency to approriate a different culture than their own? There's definitely some confirmation bias going on, but I see so many subgenre in my suburban life and I don't know if other cultures have that as well.
|
[
"You might get more help at ",
"/r/culturalstudies",
", or at ",
"/r/sociology",
". Definitely, some parts of sociology deal with those issues. ",
"Personally, I can't help you much with the exact question. I can definitely recommend ",
"Resistance Through Rituals",
". While its focus is on working class youth subcultures, there are a lot of topics related to (re)appropriations of certain cultural elements.",
"There are some papers in there dealing with black working class music appropriated by white working class youth (Hebdige, \"Regge, Rastas and Rudies\" and Chambers, \"A strategy for living\"). Later especially sees it through a processes in which class issues in America were turned into racial. White working class, according to him, being of the same class but hegemonic over black working class, had both the means and power to appropriate their music and redefine it as its own.",
"Basic point would be that (re)appropriation of elements of different culture does not mean an attempt to negate ones own. It can be an expression of betrayed expectations, unobtainable goals or a lack of definition in ones place in society. However, appropriation than is, mostly symbolic, expression of those aspiration or purely of discontent.",
"I can only speculate wildly on your given example, not being very familiar with details of American youth cultures and just marginally with related studies of subcultures. But I would hazard a guess that it might me an expression of felt marginalisation with regards to future prospects of vertical mobility. As successive generations always \"had it better than their parents\" it became a norm, one that is now under question. In that way, culture of marginal minority might find resonance in majority."
] |
[
"Actually, I would suggest ",
"/r/AskSocialScience",
"."
] |
[
"Thank, the question will be cross posted."
] |
[
"What's the difference between electric flux density and electric field?"
] |
[
false
] |
From different sources, I have the following expressions for the electric flux density D and electric field E: D=Flux/Area and E=Flux/Area But then I read about the equation D=permittivity*E which is contradictory with the above equations. So what explains this discrepancy?
|
[
"The D field and the E field are physically different things. Depending on what book you use, one or the other (or both!) may be called the \"electric flux density\" or the \"electric field\". This is highly confusing. To avoid confusion, in my class, I don't use these phrases at all and simply refer to them as \"the D field\" and \"the E field\". So what are they?",
"The E field is the total electric field. It is what you physically measure when you are doing a direct measurement.",
"The D field is a partial electric field, meaning that it is only part of the total electric field E. It is the part of the E field that is not directly attributable to a material's electric response.",
"The other partial field is the P field, which is the part of the total field E that arises directly from a material's electric response.",
"The general relationship between the total field and partial fields is:",
"E = (D/ε0) + (-P/ε0).",
"The negative sign in front of the P is a quirk arising from the way the P field is defined, but you should really think of the E field as the sum of the two partial fields.",
"Note that the expression D = ε E is not generally true. It is only an idealized special case for linear materials. ",
"Also note that when there is no dielectric material in the system, P = 0, and the above equation reduces to:",
"E = D/ε0",
"Therefore, away from materials, the E field and D field end up exactly the same (up to a universal constant scale factor), but in general they are not the same thing."
] |
[
"When you expose a dielectric material to an electric field, the atoms within the material will tend to align themselves with the electric field. That is, on average, the electrons will be pulled towards the source of the field, and the protons will be pushed away. This effect is called polarization. All the atoms within the dielectric will tend to align themselves in the same direction, with the electric field.",
"But now that the atoms, which used to be electrically neutral, are now behaving as a positive and negative charge. They don't separate, as (ideal) dielectric materials are non-conductive. So now you can imagine, every atom is now a positive and negative charge, aligned with the electric field. If you remember from the definition of electric field, this atomic dipole is now contributing its own electric field to the original electric field, and it must be aligned in such a way to make the field stronger because it is aligned against the original electric field.",
"The D field is the sum of the E field and the resulting polarization effect.",
"Edit: The wikipedia page on Electric Dipole Moments may help you to visualize this effect."
] |
[
"You sound like you're a student taking your first E&M course. It is good that you are asking these questions. Try to connect electric fields with things you learned earlier. This is physics, things interact via forces. You can compute a force from one charged body onto another with Coulomb's law. The electric field is an abstraction of this. You can take a collection of charges and compute the electric field from them, and then you can do things like compute the forces on an introduced charged particle, or compute the energy change by moving some of the charges around. All nice fun stuff, but it really does not get to the heart of your question.",
"Materials are made out of charged particles. A material will respond to an electric field E by allowing the charges to move around, causing a net polarization, P, of the material. The displacement field, D, is defined as",
"D = E + P",
"The polarization of the material is implicit in the displacement field but not in the electric field. For a linear material",
"P = X E",
"so that",
"D = ( 1 + X ) E",
"To get back to your equation 3, we define",
"permittivity = 1 + X"
] |
[
"If you painted something \"true black\" (i.e. absorbs all light) would you only be able to see the object in silhouette?"
] |
[
false
] |
I'm curious since the color black releases minimal amounts of light, hence why it is black, would it be possible to have such a deep black color that it absorbs all the light and doesn't reflect any back. Also, would that mean that we could only see that object's edges, but no definition of the object since it isn't releasing any light?
|
[
"If by \"see\" you mean see with our naked eye, then yes, a truly black object (i.e. a perfect absorber) would look... well black, meaning that no photons would be reflected from that object and reach our eyes. In that case, the only way to visually detect that object would via ",
"the contrast provided by the less absorbent materials surrounding this black mass",
", provided that the black mass is not isolated.",
"However if we extend the definition of the word see to include detection by instruments capable of detecting electromagnetic radiation in other wavelength ranges than visible light, then no object is truly dark (barring exceptions like black holes). The reason is that all objects emit so-called ",
"thermal radiation",
" simply by virtue of being at a non-zero temperature. What is perhaps surprising that when it comes to thermal radiation, a perfect absorber is also a perfect emitter, as described by ",
"Kirchhoff's law",
". ",
"The spectral profile of such this radiation is that of a so-called ",
"black-body",
" and depends on the temperature ",
"as shown here",
". For an object near room temperature conditions, this spectrum would peak in the infrared, as seen ",
"here",
". While our eyes can't detect this light, there are imaging systems capable of detecting such thermal radiation (e.g. thermal cameras), which produce images like ",
"this."
] |
[
"I'm not sure if there is a theoretical maximum of light obsorbtion without being a black hole, but if you want to see an existing example of this phenomenon check out ",
"Vantablack",
" which absorbs 99.965% of incoming light. In that picture the material is crinkly like the aluminum foil but there is not enough light coming from the material to provide depth information to your eyes."
] |
[
"But you're looking at it on a screen. Does it hurt your eyes to look at screens when they're turned off? Because that's the most black they can produce."
] |
[
"Is there any cost increase for ISP's in increasing download speeds ?"
] |
[
false
] |
[deleted]
|
[
"All right, since you want to play word games and be somewhat pedantic in your 'counter-explanation' with no substance beyond further defining presumptions made originally, let's break this down further and define some terminology so that we're all on the same page.",
"Costs have no return - literally throwing money away.\nInvestments have return - using money to make money.\nPrice is a number that could be associated with either of the above.\nValue is more ethereal, as it is defined in the combination of the above when related to a customer.",
"Infrastructure is an investment: Electricity, server, router, switch, cabling, poles, nodes/DSLAM/Central Office, maintenance, employees, contractors, upstream links, downstream links, etc, etc, etc - this is ALL part of infrastructure. It's literally an umbrella that refers to what is required to deliver service. If you really want to break it down to the last bit that travels through the cable, we can spend all night on that part. I was providing a succinct answer without getting bogged down in details, but you seem more interested in picking apart any loose thread you believe you can.",
"\"Flipping the switch has a calcuable price\" - not if the infrastructure is pre-existing. As I said in my specific example, Comcast has had the entire infrastructure to support 1 Gbps across their network. They've had it since 2007. They built it up and out in the late 90's to mid 00's. Right now, this very second, it really would be as simple as setting configuration updates out to their network to boost the speed. Because they HAVE been upping speeds at regular intervals all the time, and it's not because they're spending MORE money on infrastructure but rather following a pre-defined plan for upgrades based on competition only.",
"'The cost of installing infrastructure and physical locations to House it all and a hundred other costs'. Absolutely - but once it's built, it's built. You talk about maintenance / upkeep costs (electricity, manpower, hardware replacements) as cost to UPGRADE the network, and I say, no, that's not to upgrade it, that's to maintain it, and that's already built into the money they charge the customer per month to begin with. We'd really have to delve into actual profit margins to know how much of every monthly bill is required to maintain connectivity, and no company will divulge that info willingly.",
"Now that we're off-topic, let's go back to OP's question.",
"\"Is there any cost INCREASE to ISPs to increase download speeds?\"",
"The answer is, 'It depends on how far ahead the ISP planned, in both terms of infrastructure and manpower. Some ISPs are utilizing less than 10% of their available network resources, and as such, can increase speeds with minimal to no additional cost. Other ISPs are utilizing near the max of their available network resources, and as such, would require heavy investment and cost to build out their network and replace old technology with newer technology to be able to provide faster service.",
"On a side note, DSL is playing catch up in terms of speed because most DSL providers still use mainly copper lines to deliver service, which need serious upgrades/investments to improve, so it's costing them a LOT more to push faster speeds over time.",
"Source: Network Operations Center tech"
] |
[
"That's entirely based on whether they have to invest in infrastructure ( routers, switches, cabling, etc ) or if the structure is already there. ",
"Example. I worked for Comcast in 2007. Their entire network up until the last mile before your home is fiber optic. They could quite literally flip a switch and boost speeds at any point to gigabit or higher with little to no investment in infrastructure upgrades.",
"Other service providers may not have that, so they max out lower and do have to upgrade components, so in those cases, yes, there is a one time cost. ",
"And that's the thing. Upgrades are one time costs unless stuff breaks. So if you do a huge upgrade, but then trickle the speed lower, you can control people's perceptions and slowly increase speed overtime for no cost. The benefits of that are fantastic for the company itself."
] |
[
"Well this is a broad brush you’re painting with. While you seem to understand the answer you don’t point out the individual costs for op and you assume the costs are one time when they aren’t ",
"Flipping the switch has a calculable price",
"Upping speed means ensuring there is bandwidth available",
"This requires physical infrastructure including routers switches cabling servers but other things are needed too like electricity cooling security physical rack space humans to support setup repair replace configure the equipment. Networks are only as fast as their slowest link so all parts need to be in sync",
"There’s also the cost of installing infrastructure and physical locations to House it all and a hundred other costs",
"So The answer is yes there is definitely a cost"
] |
[
"Sound to electricity?"
] |
[
false
] |
If you make a membrane that vibrates at the frequencies generated by traffic, and attach loads of small magnets to it, and have it cover a static frame with small copperwire coils, so that each magnet oscillates inside the copper coil, and connect the coils, how much power could that generate, if you covered the noise-shielding walls along the freeway? Enough to power streetlamps for instance? This might well be an idiotic question, but I've wondered about it for some time.
|
[
"Congratulations, you have invented the microphone. "
] |
[
"Okee -- I've done some sound engineering, so I have some background on this, but am by no means an expert:",
"90dB SPL at 10m is what Wikipedia says is a highway noise -- that's pretty loud. That translates, however, to a tiny 0.001 Watts per square meter. ",
"Assuming a typical number for streetlight spacing is 250 feet per 150w lamp (from some random doc I found), you're looking at 0.6W/ft.",
"At 0.001 W/m",
" you'd need a retaining wall more than a mile tall, IF you could convert 100% of the sound to electricity. (You also wouldn't get 0.001W/m",
" for the full 1.22 miles, but that's another issue).",
"So, in short: no, the acoustic energy of a roadway is very tiny. All the noise a car makes is energy lost to the world (same with friction), so it's in the car designer's interest to make the car as quiet as possible.",
"Hope that helps, and please let me know if there's any math or physics errors in the above."
] |
[
"That, in itself, is awesome."
] |
[
"If swelling/inflammation is our body's method of sending essential blood cells and nutrients to a site of damage, why are most treatment efforts after, say, an ankle sprain concentrated on reducing swelling?"
] |
[
false
] | null |
[
"This is discussed pretty thoroughly here ",
"http://www.reddit.com/r/askscience/comments/1crwwf/it_seems_more_often_than_not_reducing_swelling_is/"
] |
[
"I'm a practicing neurologist with a bachelor's of science in biochemistry, a master's of science in neuroscience and a PhD in neuroscience. My MD specialization was in clinical neurology. ",
"Cell \"necrosis\" literally just means the cell dies. When you talked about a cell \"swelling\" and \"breaking apart\" you're referring to apoptosis.",
"In apoptosis the cell mediates its' own death, initiates proteolysis, swells, forms \"buds\" and drifts apart. The fragments are phagocytized by the immune system. ",
"Necrosis refers to any condition causing a cell to die except at its' own hand. This could be any multitude of things... The death itself does not damage nearby cells. ",
"Cell fragmentation does not harm nearby cells. In the absence of apoptosis, there wouldn't be enough proteolytic caspases or other degradative enzymes built up to cause damage to nearby cell membranes. The mechanical process would not cause damage. I suppose a fractured digestive organelle (vacuole) could spill out some toxic enzymes but we're not talking nearly enough to damage cell membranes. ",
"If you have any other questions or need anything else cleared up before you take your exam feel free to shoot me a message. Psychophysiology was one of my favorite classes. If you're in neuroscience or you're a bio major, see if your school offers neuropsychopathology. "
] |
[
"Generally speaking, evolution is not a very efficient development process. It picks whichever route to a solution is the easiest given the existing resources, regardless of its long-term efficiency or effectiveness. This is of course anthropomorphising a long-standing array of patterns, but it does tend to favour the path of least resistance rather than the shortest or safest path.",
"So, we have an over-active response rather than a more effective under-active one, a laryngeal nerve that does a loop down our neck to bridge a few centimeters in the brain, a shaking eye to resolve a design blindspot, and share our breathing tube with our eating tube, to name but a few.",
"On occasion, there are selective pressures such that the resultant design is refined and made more efficient, but this is relatively uncommon given the specificity and energy investment necessary."
] |
[
"How far from Pluto is the Oort cloud and is it even possible for New Horizon to return data if it reaches it?"
] |
[
false
] | null |
[
"Pluto is about 33 AU from the sun (1 AU = Earth sun distance) The inside of the Oort cloud is about 2000 AU away. New Horizons is traveling at 58536 km/hour, so it will reach the Oort cloud in about 580 years. The power source has a current power of about 200 W and drops about 5% every four years. So in 580 years, the generator will give about 100 mW of power, not enough to run the systems much less return any data.",
"https://en.wikipedia.org/wiki/Oort_cloud",
"https://en.wikipedia.org/wiki/New_Horizons#Power"
] |
[
"It's ",
" far. 1 AU is the average distance from the Earth to the Sun. Pluto's orbit varies between about 30 and 50 AU. The Kuiper belt, another New Horizons target, is about the same distance from the Sun. The Oort cloud doesn't start until about 2000 AU, and extends to about 100,000 AU (2 light years!).",
"At the speed of the probe, it will take almost a thousand years to reach the inner bounds of the Oort cloud, so no, the probe will be dead by then."
] |
[
"Space is huge. Pluto's farthest point out, the aphel, is at roughly 50 astronomical units or 50 times the distance between earth and sun, and it took NH quite a while to reach Pluto. Even though we cannot say it with absolute certainty, the oort cloud begins somewhere around 3000 astronomical units. That's really really really far away. New Horizons will definitely run out of electricity long before reaching the oort cloud, so it won't be able to send data back to us."
] |
[
"For you surgical redditors: Aortic dissection vs \"dissecting aortic aneurysm\"."
] |
[
false
] | null |
[
"No you are not mistaken, and your definitions are correct. You can have an aortic dissection without an aneurysm, an aneurysm without dissection, or both together.",
"The problems they cause are a bit different. The main worry with an aneurysm is that it can burst, causing rapid, massive blood loss. The only treatment is emergency surgery, which has a high mortality rate. Aneurysms are usually monitored by regular scans until they get to a size when the risks of leaving it outweigh the risk of surgery; the cut off is around 5cm.",
"With a dissection, the worry is that the split in the wall of the artery can obstruct blood flow to vital organs, causing heart attacks, strokes, or other major complications. Historically, dissections were managed without surgery if the split was lower down in the aorta, by trying to control the patients blood pressure and so reduce the damage to the vessel wall. Dissections starting closer to the heart were still taken to theatre though.",
"In the last five to ten years the big change in the management of these conditions has been the development of stents, which can be placed into the artery, by a much less invasive surgical procedure. Stents are being used for both aneurysms and dissections. Interestingly, the long term outcome studies are just now being published and suggest that while stents are better in the short term ,they have a higher long term complication rate compared to the standard open surgical techniques."
] |
[
"Can't answer any better than this dude(ette). Well done."
] |
[
"Thank you. "
] |
[
"When we say 70% of the human body is water, is that mass or volume?"
] |
[
false
] |
"The human body is 70% water" is a really common "factoid" we hear when studying biology or just as a random fact. But is that referring to our mass or to our volume?
|
[
"The statement can be accurate in both senses. The human body itself is roughly about as dense as water (sometimes less, sometimes more depending on body fat percentage and other factors), so if your body is 70% water, and the rest of it is about as dense as water, then your mass fraction and volume fraction of water are relatively the same."
] |
[
"Is it roughly the same as water because it's seventy percent water by mass? Or because the mass of all of the components of the human body is similar to water? The statement is most accurate, and in fact is meant to be referring only to mass."
] |
[
"The fact that we're mostly made of water is part of it. The remaining organic compounds are roughly as dense as water, since they contain nitrogen and carbon (which are slightly lighter than oxygen) and phosphorous (which is a fair bit heavier, but found in smaller amounts). This is a gross simplification, but the density of most organic compounds are similar partially for this reason.",
"Edit: Here is a decent list of organic compounds: ",
"http://www.kayelaby.npl.co.uk/chemistry/3_3/3_3.html",
"You'll see that most of their densities hover right around that of water, which is 1000 kg/m",
" ."
] |
[
"Do animals have an individual scent as well as a \"species\" scent? Can other animals tell them apart?"
] |
[
false
] |
For example, could my dog (hypothetically) know which individual squirrels have been in our backyard, or just that squirrels in general have been there?
|
[
"I hope you get an answer! This is a good question! "
] |
[
"Can't answer for squirrels/dogs with knowledge but can answer for honey bees. Yes they do at least on the nest level. Honey bees can certainly tell distinguish other non-honey bee bees that enter the hive in the complete darkness from themselves and the do it primarily by smell. Every so often we will find bumble or carpenter bees that entered the hive and don't make it out alive. ",
"Honey bees can also differentiate honey bees from another hive. The guard bees will typically keep them out, but if they are loaded down with nectar might let them in. Pretty soon the worker adopts the smell of the hive and becomes part of it. ",
"Putting one beehive on top another initiates a lot of fighting until the smells of the hives combine.",
"Honey bees can also be fooled. The ",
"Death's head hawk-moth",
" smells like a honey bee and they use this as camouflage to enter hives and steal honey. Its clearly too large to fool them its mostly about smell.",
"Actually yes I can answer about dogs. Your dog can tell, this is how bloodhounds track down a specific person not just anyone when hunting escapees."
] |
[
"They would most likely (since we can't just ask them personally) determine individual differences based on urine scents, which are quite pungent odors and would vary widely based on species, average diet, activity, health, and so on. Secondarily would likely be their body scent, which wafts to the ground as scents are heavier than air. This second method isn't quite as direct as the first, but it's a viable tool nonetheless.",
"That said, identifying individual squirrels would be quite a bit more difficult, due to typically wanting to chase/catch them more so than learn about them.",
"Dogs can ",
"positively identify other dogs",
" by sight alone researchers have determined, which is a super important step to understanding how they percieve the world around them.",
"Scent, though, for dogs is actually more acute than their vision. They can determine the time of day by room odor, individuals, trails, and the faintest of faint traces of chemicals. This isn't even talking about other dogs, as they use their keen noses to determine health, age, sex, and breeding potential among other characteristics.",
"So I would in the face of the evidence say yes, they can identify individual animals by species and on a case-by-case basis if presented with a reason to do so, such as with positive reinforcement training."
] |
[
"What changes in the designs of wires and connectors to make them faster across generations?"
] |
[
false
] |
Why is USB 1.0 so slow despite being bigger than USB 2.1, and how is the newest USB wire so much faster than both of those?
|
[
"A few things are going on."
] |
[
"From generation to generation, the electronics that send and receive information into the cable get better and faster, so more signals are sent per second.",
"I'd like to add to the first point. It is true that they get better but most importantly, they get ",
". The cheaper it is, more accessible to the mass market and more likely for manufacturers to actually implement the standard."
] |
[
"The cable specifications have also changed and cables have improved for USB and Ethernet. Cat 5,5e, 6, and 7 each improves on the previous. The impedance and inter-pair timing skew especially must be tightly controlled.",
"In the early stages of USB 3.0, many cable and connector manufacturers were unable to meet the requirements of USB 3.0. The impedance requirement of 90Ω ± 15Ω at the connector and the skew recommendation of 15 ps/m were seldom met. When Omnetics ran an informal test of a dozen off-the-shelf USB cable assemblies in 2014, only one of the assemblies met the USB 3.0 specification. ",
")"
] |
[
"I’ve heard that 99% of our “mass” comes from the electromagnetic force in atoms and the strong force, does that mean there is no such thing as mass, just energy?"
] |
[
false
] | null |
[
"All mass has an energy equivalence."
] |
[
"But are they two different things or is it all just energy?"
] |
[
"They are two different things that are related to each other."
] |
[
"Why do white arctic animals have black noses?"
] |
[
false
] |
If animals in the Arctic have evolved to have all white fur/hair to blend in, why do they still have dark colored noses? For example, polar bears or arctic foxes.
|
[
"Why do white arctic animals have black noses?",
"It's simply because their skin is black.",
"Both polar bears and arctic foxes have black skin (",
"see for yourself",
") underneath their thick coats, caused by a high concentration of the pigment eumelanin, and thought to adaptively help them maximise heat absorption and retention. Some likewise argue the high concentration of eumelanin helps protect their otherwise exposed noses from harmful UV radiation. Given polar animals live in a relatively UV impoverished environment, perhaps not. But who knows?",
"If animals in the Arctic have evolved to have all white fur/hair",
"Ah! Polar bears don't have white hair ",
", rather, it's translucent (at least in the visible spectrum). In a similar way to how snow appears white, large numbers of translucent hair fibres in their dense fur scatter and reflect away most visible light; thereby causing the bear's fur to appear white - or the colour of sunlight - to an observer. An abundance of popular misconceptions have arisen in the literature over the years on polar bear fur, mostly around how the 'transparent' nature of their hair allows each one to act like a 'fibre optic cable', allowing bears to 'harvest' the majority of sunlight that hits them and transfer it to their skin to be absorbed as heat: alas, this is all demonstrably false [1][2]*. Only about 10-20% of sunlight hitting a bear makes it down to the skin; the rest is scattered away.",
"Speaking of misconceptions; given their black noses, it's also often said polar bears will 'hide' their nose from prey during hunting, by pushing a block of ice in front of them, or otherwise hiding their nose behind a paw. There has never been any evidence to support these claims. ",
"In any case, polar bears and arctic foxes (and, too, ",
"arctic hares",
") have dark coloured skin which helps them, presumably, better absorb heat, and where their fur coat is thinnest (or absent entirely; i.e. their nose and paws) you can simply see that dark colour. In contrast, ermine have pink-ish skin and pink-ish noses (",
"image",
"), ditto snowshoe hare (",
"image",
"). As for this:",
"why do they still have dark colored noses? ",
"It's a bit tautological, but there hasn't been any evolutionary pressure selecting for lighter skin on the nose. Presumably; i) UV protection, if true, is more important; ii) the required genetic path is too tricky; iii) as their eyes are dark anyway it won't make much difference; and iv) the preferred hunting ground of a bear is either at a ",
"seal's breathing hole",
", or looks ",
"like this",
" (also check out ",
"this video",
" from BBC's ",
"); under these circumstances, if, as a seal, you're close enough to spot a nose, it's probably waaaay too late!",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" ",
" "
] |
[
"Ah, that makes total sense! Thank you so much for your comprehensive answer!!"
] |
[
"I was mildly disappointed that the linked image wasn't a fully shaved polar bear, ngl"
] |
[
"If you lit enough candles in a small room, would you eventually suffocate from lack of oxygen?"
] |
[
false
] | null |
[
"This. The room would basically have to be airtight, which is not likely to happen in a house. ",
"That being said, a room that was airtight enough that candles could burn out of the O2 causing suffocation is also a room that you could suffocate in just by breathing out the O2 in the absence of candles."
] |
[
"If the room was set up in a way that more oxygen was being exhausted by you + candles than was diffusing or flowing in, then yes. "
] |
[
"Assuming a candle is made of ",
"paraffin wax",
", the best guess I could find was that the formula was C25H52. The full combustion assuming clean burning:",
"C25H52 + 38O2 --> 25CO2 + 26H2O",
"1mol of C25H52 (352g) burns 1216g of O2. Using the ideal gas equation (pV=nRT) assuming STP, this takes up 914L or ~0.9m",
" Air is 21% oxygen, so this would be 4.35m",
"So in a room 2x2x1m (basically a closet), sealed shut, 352g of candle would use up all the oxygen, theoretically. Using ",
"this",
" and ",
"this",
" and ",
"this",
" as a source, that'd take around 81 hours (not a great value, the times were inconsistent).",
"On the other hand, a human will consume around ",
"0.55m",
" a day.",
"I can't tell you the exact O2 concentration it takes to put out a candle or kill a man though. But it looks as though 1 candle will use up about as much oxygen as 2.5 people.",
"TL:DR",
"Candles rate of oxygen consumption = 1.23m",
" day",
"Humans rate of oxygen consumption = 0.55m",
" day"
] |
[
"Why do babies not inherit their mom's immunizations?"
] |
[
false
] | null |
[
"To clarify and expound just a bit:",
"There ",
" a component of inherited immunity that is conferred to the infant. However, this is common to most people and has very little variation. It is the innate immune system. Things like complement, PAMP, and TLR pathways are here. ",
"But for immunizations acquired later in life, Th3Redeyedjedi is correct - the child inherits the variability in the ",
" from its parents, but not the ",
" immunities developed. It's like getting a hybrid of your parents' houses and tools, but not the furniture or decorations so you have to build your own as you need it. These are part of the HLA and MHC system Th3Redeyedjedi talked about.",
"The antibodies that the baby receives is called ",
" immunity. Those are the same immunities that the mom has, but only one specific subset of it. There are 5 classes of antibodies that we use for immunity:",
"IgG, IgA, IgM, IgE, IgD",
"Ig = immunoglobulin; the letter is just to differentiate. ",
"Only IgA makes it through the breast milk, so only infections that trigger an IgA response normally will be protected against by this passive immunity. It is probably too much detail to go into, but suffice it to say there are reasons for each class and IgA handles only some infections but not all. These also fade pretty rapidly and usually by 6-12 months they are no longer useful (because mom stops breastfeading and/or the baby is big enough that he can metabolize the IgA faster than it can come it). ",
"I am not sure if he intended to imply this, but it seems like Th3Redeyedjedi is implying that the IgA from the breastmilk is was results in hemolytic disease of the newborn. This is not correct. ",
"Hemolytic disease of the newborn and hydrops fetalis are different ends of the spectrum of the same disease entity. If the mom's blood type does not match the baby's then you can get HDN. This is the ABO blood types (not the Rh) and it results in mild to moderate jaundiced hemolytic anemia in the newborn. This is because the baby's blood does cross the placenta in very small quantities (not 100% of the time and not often a lot at all) and when the baby cells get into mom's blood, she creates antibodies against it. These become IgM after a while but they can't cross the placenta. But sometimes the mom's blood leaks into the baby through the placenta and then the IgM's are the baby's blood and the antibodies destroy the red blood cells. But typically very little gets across, so it rarely needs intervention. ",
"HF however, is a much more severe. This is when there is Rh incompatability. However, this only happens if it is where the mom is Rh(-) and the baby is Rh(+). The (+) and (-) indicate if a particular protein is on the surface of the red blood cell (RBC). If there is no protein, there is nothing to make an antibody to. The baby can't make its own antibodies while in the uterus. So if it is Rh(-) and the mom's blood gets into it, nothing happens. If it's blood gets into mom, then nothing happens (because baby has no protein so mom's immune system doesn't do anything).",
"But if it is the other way around, the baby's Rh(+) blood gets into Rh(-) mom and then her immune system makes antibodies. But at first it is IgM which can't cross the placenta. So usually the 1st baby has no issues, except for maybe some HDN. But if the second baby is Rh(+) the mom will have IgG by this time and that can cross the placenta. It gets into baby's blood in huge amounts and starts destroying the RBCs in huge amounts. Baby can't keep up production, but still needs oxygen to grow, so the heart beats faster to try and keep up with demand. Eventually it is so low and the heart has been beating so heard for so long the fetus dies of heart failure and becomes swollen and this is hydrops fetalis and is always fatal. ",
"So when we have an Rh(-) mother we always give her Rhogam ",
". Once at 24 weeks and again right at birth. This is a drug which is antibody to Rh(+). So if baby's Rh(+) blood gets into mom, the Rhogam destroys them before mom can make her own antibodies to it. We give it at 24 weeks because that is when the most risk of small placental bleeds begins. And we give it at birth because all women bleed when they give birth and the baby's blood always gets into hers (we can even detect it and tell you how many there are so we can tell if a woman has given birth within the previous 2-3ish months just by looking at her RBCs)."
] |
[
"To clarify and expound just a bit:",
"There ",
" a component of inherited immunity that is conferred to the infant. However, this is common to most people and has very little variation. It is the innate immune system. Things like complement, PAMP, and TLR pathways are here. ",
"But for immunizations acquired later in life, Th3Redeyedjedi is correct - the child inherits the variability in the ",
" from its parents, but not the ",
" immunities developed. It's like getting a hybrid of your parents' houses and tools, but not the furniture or decorations so you have to build your own as you need it. These are part of the HLA and MHC system Th3Redeyedjedi talked about.",
"The antibodies that the baby receives is called ",
" immunity. Those are the same immunities that the mom has, but only one specific subset of it. There are 5 classes of antibodies that we use for immunity:",
"IgG, IgA, IgM, IgE, IgD",
"Ig = immunoglobulin; the letter is just to differentiate. ",
"Only IgA makes it through the breast milk, so only infections that trigger an IgA response normally will be protected against by this passive immunity. It is probably too much detail to go into, but suffice it to say there are reasons for each class and IgA handles only some infections but not all. These also fade pretty rapidly and usually by 6-12 months they are no longer useful (because mom stops breastfeading and/or the baby is big enough that he can metabolize the IgA faster than it can come it). ",
"I am not sure if he intended to imply this, but it seems like Th3Redeyedjedi is implying that the IgA from the breastmilk is was results in hemolytic disease of the newborn. This is not correct. ",
"Hemolytic disease of the newborn and hydrops fetalis are different ends of the spectrum of the same disease entity. If the mom's blood type does not match the baby's then you can get HDN. This is the ABO blood types (not the Rh) and it results in mild to moderate jaundiced hemolytic anemia in the newborn. This is because the baby's blood does cross the placenta in very small quantities (not 100% of the time and not often a lot at all) and when the baby cells get into mom's blood, she creates antibodies against it. These become IgM after a while but they can't cross the placenta. But sometimes the mom's blood leaks into the baby through the placenta and then the IgM's are the baby's blood and the antibodies destroy the red blood cells. But typically very little gets across, so it rarely needs intervention. ",
"HF however, is a much more severe. This is when there is Rh incompatability. However, this only happens if it is where the mom is Rh(-) and the baby is Rh(+). The (+) and (-) indicate if a particular protein is on the surface of the red blood cell (RBC). If there is no protein, there is nothing to make an antibody to. The baby can't make its own antibodies while in the uterus. So if it is Rh(-) and the mom's blood gets into it, nothing happens. If it's blood gets into mom, then nothing happens (because baby has no protein so mom's immune system doesn't do anything).",
"But if it is the other way around, the baby's Rh(+) blood gets into Rh(-) mom and then her immune system makes antibodies. But at first it is IgM which can't cross the placenta. So usually the 1st baby has no issues, except for maybe some HDN. But if the second baby is Rh(+) the mom will have IgG by this time and that can cross the placenta. It gets into baby's blood in huge amounts and starts destroying the RBCs in huge amounts. Baby can't keep up production, but still needs oxygen to grow, so the heart beats faster to try and keep up with demand. Eventually it is so low and the heart has been beating so heard for so long the fetus dies of heart failure and becomes swollen and this is hydrops fetalis and is always fatal. ",
"So when we have an Rh(-) mother we always give her Rhogam ",
". Once at 24 weeks and again right at birth. This is a drug which is antibody to Rh(+). So if baby's Rh(+) blood gets into mom, the Rhogam destroys them before mom can make her own antibodies to it. We give it at 24 weeks because that is when the most risk of small placental bleeds begins. And we give it at birth because all women bleed when they give birth and the baby's blood always gets into hers (we can even detect it and tell you how many there are so we can tell if a woman has given birth within the previous 2-3ish months just by looking at her RBCs)."
] |
[
"You are correct that Rh incompatability is not the ",
" cause of HF. I was not clear on that point.",
"And I thought you mightn't have intended that.",
"Rh(-) can be mild in some cases",
", but in most case results in HF but only during the 2nd pregnancy. ",
" the first. ",
"ABO",
" incompatability leads to HDN, which can be severe at times but is almost always not. ",
"And actually I was incorrect in on thing I said. HDN and HF are not degrees of severity of the same disease entity. What I should have said was that ",
" HDN leads to HF and there are other causes of HF as well. "
] |
[
"Can a proton be taken from an atom? If so, what happens when this occurs?"
] |
[
false
] |
So I know that electrons can be taken or shared in ionic and covalent bonds but I was curious to know whether or not the same could happen with protons. I understand that this would change the elemental properties of the atom but I'm interested to know if anyone has attempted this because if we can split an atom then shouldn't we have a way of taking a proton out of the nucleus?
|
[
"We can pull protons out of the nucleus, but this would be a nuclear reaction, not chemistry. We've been doing nuclear reactions in experiments for about 100 years.",
"For the most part, the nucleus doesn't care about what happens at the level of the electron cloud."
] |
[
"For some radioactive elements, all you need to do is just sit back and watch. One of the three main types of radioactive decay is known as an alpha decay, where a bundle of two protons and two neutrons is spontaneously ejected from the nucleus of a radioactive atom in order to make the nucleus more stable. This bundle of two protons and neutrons is ejected extremely fast and has a lot of energy. And yes, the identity of the element itself also changes, because its atomic number goes down by two, and atomic mass goes down by four."
] |
[
"This usually happens naturally with radioactive decay, such as the decay of Uranium-238 into Thorium-234 by the emitting of alpha particles. Mostly it's to stabilize the nucleus. In short, if a proton is loss or gain it will change the element entirely. "
] |
[
"what sources do we have to understand climate in early historical times?"
] |
[
false
] | null |
[
"Well there’s quite a number of indicators to past climate and we use a lot of different indicators for different periods in time. I’ll try to name a few particular interesting tools we have to learn about our climate history.",
"One particularly useful one if the 800,000 year old Antarctic ice core record. These core samples can tell us all sorts of cool stuff but namely its actually able to give us measurable data on C02, CH4, and N20 levels. Measurements are obtained from snow bubbles trapped in the ice. ",
"If we take a step back in time about 4 billion years very little is know about the earliest days on earth, during a time know as the Hadean Eon. The best indicator we have on the climate of this time come from Zircon crystals found in the Jack Hills in Australia. These crystals are the only physical evidence we have from that far back. They are able to tell us through the distribution of the isotopes O-16 and O-18 that these Zircon crystals were formed throughout some kind of interaction between magma and water. We can infer this because the more abundant O-18 isotopes are what we would expect to be left behind through the evaporation of water, because these isotopes are heavier than the O-16 isotopes which more readily evaporate. Knowing this we think the earth was surrounded in a proto-crust consisting of Basalt and Anorthorsite that was the result of cooling oceans of magma. ",
"During the Paleocene (around 69 billion years ago) something close to 17 billion tons of C02 entered the climate system resulting in a static warming effect. That’s a crazy amount. We call this period of time the Paleocene-Eocene Thermal Maximum. Evidence for this stems from both the terrestrial sediment record and deep-sea core samples. Through this we can see that the more abundant Carbon-12 isotopes in comparison to Carbon-13 confirms Carbon rich organic materials were present within the ocean atmosphere system. This oxygen isotope deep-sea sediment record is a really important tool too. ",
"Most of this information as well as many more indicators to past climate indictors can be located in this text: “Climate change: the science of global warming and our energy future.”"
] |
[
"For early historical times (ie, the past few thousand years) our best lines of evidence come from tree rings and lake cores. Tree rings tell us about tree growing conditions. Tree ring records go back much further than living modern trees...trees used in buildings and buried in sediment can be used to extend the record backwards, because it's possible to match up the outermost rings in older trees with inner rings in younger trees, forming a continuous record.",
"Lake sediments are laid down slowly over time, and pollen that falls into the lake settles to the lake bed, forming annual layers with every blooming season. This can tell us a lot about what plants lived where, and that's directly related to local rainfall and temperature."
] |
[
"Pretty sure it's more that they use trapped air bubbles over the density. The air is compressed and trapped in the ice, giving a pretty solid estimate of the gasses and climate during the time. Haven't heard anything about your answer, but I'll check it out."
] |
[
"Quantum mechanics: Do the electrons in an electron pair in an atomic orbital occupy the same physical space?"
] |
[
false
] |
Another related question: Is an electron cloud a representation of a electron waveform? I.e., does an unperturbed electron in an atom exist as a diffuse entity?
|
[
"So I'm curious. Chemistry textbooks which show orbital diagrams... To what probability are they showing? Or in other words... Where do they make the cut off? Because, if the probability never reaches 0, then you wouldn't be able to draw a picture like that as they could be \"anywhere\" (meaning, you couldn't just draw a finite sphere for the s-orbital). So do they make the cut off like 1%, .1% or is there something else they use to limit it? Does my question make sense? If not I can try to reword it..."
] |
[
"So I'm curious. Chemistry textbooks which show orbital diagrams... To what probability are they showing? Or in other words... Where do they make the cut off? Because, if the probability never reaches 0, then you wouldn't be able to draw a picture like that as they could be \"anywhere\" (meaning, you couldn't just draw a finite sphere for the s-orbital). So do they make the cut off like 1%, .1% or is there something else they use to limit it? Does my question make sense? If not I can try to reword it..."
] |
[
"It doesn't exist as a diffused entity though, does it?"
] |
[
"which shape resists impacts better; triangle or circle?"
] |
[
false
] |
My brother is trying to build a robot. It needs to be able to resist sharp impacts. He favours a design of multiple panels bolted together in a triangular pyramid shape whereas I think he should try a seamless semicircle shape bolted to the chassis. which of these two structures would be more resistant to impact forces? The material is going to be hdpe, with the chosen shape attached to a metal chassis. My logic was that, even ignoring the multiple joins in a triangle, the circular shape should be able to cause most blows to glance off, whereas any blow even close to perpendicular to the surface of the triangle will damage it badly. We had an argument about this and could find nothing good on the internet. Cheers!
|
[
"And write your observations down! Otherwise it's just fooling around."
] |
[
"And write your observations down! Otherwise it's just fooling around."
] |
[
"For reference: Triangles are strongest when shapes are being built out of beams and connected by vertices. This is because every vertex of a triangle is connected to every other vertex, which rigidly defines each angle. If you're dealing with a plate of material, this doesn't apply. A triangle may actually be weaker in this case, because the extra points would cause stress concentrations while a circle wouldn't. I don't have the necessary knowledge to run the math and make an educated prediction, though.",
"You might get more help in ",
"/r/AskEngineers",
", too."
] |
[
"If two animals of different species developed antibodies for the same virus how different would they be?"
] |
[
false
] |
Would you be able to tell that they are from different animals or would they be there same because they are both trained on the same protein spike? For instance, if there were another outbreak of swine flu, could we infect a bunch of pigs then make an antibody serum from blood extracted from them?
|
[
"Not only would antibodies against the same protein be different if they came from different species, they would probably also be different if they come from two identical twins. ",
"The amount of variation possible in antibody sequences is literally astronomical, ",
"up to a quintillion different possible antibodies",
". The body can’t possibly hold all those possibilities, so a relatively tiny subset (maybe billions) of those are actually produced. The ones that are actually produced are generated (mostly) randomly, which means the chances of you having the same antibodies as your identical twin is very low. ",
"Antibodies with very different sequences can still attack the same target - there are many paths to effective binding - and actually looking at the sequences used by genetically identical mice (the equivalent of identical twins) shows that they often get to the same effective place with completely different antibodies. ",
"There is some overlap with identical animals, but not much; less (but still some) with members of the same species that are not genetically identical. In some cases it’s possible to identify patterns in the antibody sequence that might help identify its target, but this is still a very new and uncertain field. ",
"Antibodies from different species are also different in other regions of their proteins, not just the parts that interact with their targets, and that’s why you can’t easily swap antibodies between species. Your body knows what human antibodies look like and so it doesn’t make an immune response to them. It doesn’t know what horse or pig antibodies look like, and would generate an immune response to them - not necessarily (but sometimes) a problem on your first exposure, but definitely a problem if you get them twice. This is called ",
"serum sickness",
" and now is rarely seen except occasionally when people are treated for snakebite."
] |
[
"You don't test whether people have a protein of a certain structure, because everyone's antibodies are different. Rather, you include some parts of the virus on the test, and if something in the patient's blood binds to one or more parts, it has to be antibodies."
] |
[
"Thank you for a very informative answer. In relation to the current pandemic, I sometimes hear that they are testing for antibodies, to test if someone went through the infection. So how does this work if everyone essentially has different antibodies?"
] |
[
"What is the formal difference between a 'vaccine' and a 'cure' or similar?"
] |
[
false
] |
The term "vaccine" as I grew up to understand it: inactivated parts of the pathogen that would cause the immune system to develop a recognition of it as harmful, allowing it to respond immediately to later exposure to the real thing. : "We have used another noncustomized approach called in situ vaccination. Immunoenhancing agents are injected locally into one site of tumor, thereby triggering a T cell immune response locally that then attacks cancer throughout the body." So you can actually already an illness and receive a vaccine for that illness which cures it. Is anything that activates the immune system a 'vaccine'?
|
[
"It’s simply a question of definition. ",
"Treating cancer in this way is a relatively new discovery. So it all depends on how the scientific community chooses to describe it; currently they are describing it as a vaccine, which makes sense because the defining feature of the word vaccine is more the fact that it introduces an antigen or antigen-like substance in a immuno-stimulatory environment to activate an antigen specific immune response. Whether it’s given before or after the illness occurs doesn’t makes it any less of a vaccine in my opinion"
] |
[
"As ",
"/u/newsround123",
" says, it's a question of definition. Vaccination is fundamentally about educating the immune system to recognise and respond to something. Traditionally, this has been about training it to recognise infectious diseases before infection actually happens. But training the immune system to recognise cancer cells is conceptually similar, which is why they chose to describe it as vaccination. "
] |
[
"A vaccine-based cure or therapy, if you will. As opposed to chemotherapy or radiation therapy, which have different mechanisms of action. "
] |
[
"Why is carbon used for all these awesome things (carbon fibre, carbon nano tubes, etc)?"
] |
[
false
] |
Why is carbon used for all these awesome things (carbon fibre, carbon nano tubes, etc)? Is it because its so abundant? Is it because it has some amazing property that no other atom has? Is it because its the lightest element that happens to be very tough? Why not use iron or something even tougher?
|
[
"C-C bonds are very strong. When carbon is able to use all its bonds effectively, you get diamond, which is a very hard material.",
"Why not use iron or something even tougher?",
"Diamond is much harder than iron.",
"Now, carbon fibers are not diamond, not in all directions anyway. E.g. you can bend them. But along the length of the fiber, they do exhibit extreme strength.",
"Now weave a bunch of those things, and dip them in epoxy glue. Let it dry. What you get is a composite material named CFRP, Carbon-fiber-reinforced polymer, or \"carbon fiber\" to me and you. There are fibers criss-crossed in all directions, and each one of them is very tough along its length. The epoxy is holding them together and prevents unraveling.",
"It's a highly rigid material, yet lightweight. Compared to steel, a CFRP item of same size is both more rigid and less heavy.",
"EDIT: Please be aware of the differences between hardness, rigidity (stiffness) and strength.",
"http://en.wikipedia.org/wiki/Hardness",
"http://en.wikipedia.org/wiki/Stiffness",
"http://en.wikipedia.org/wiki/Strength_of_materials",
"Hardness is resistance to scratching. Stiffness is... well... stiffness (resistance to bending when deformed). Strength is the ability to resist breaking due to excessive load.",
"Diamond is the hardest thing ever; it's also quite stiff. Steel is pretty hard, but less so than diamond. Carbon fiber is not very hard (due to the epoxy), but it's very stiff and strong, and also lightweight."
] |
[
"The awesome things you are talking about are no doubt awesome, but largely due to their micro- and macro-scopic material qualities (as opposed to the intrinsic properties of elemental carbon vs. iron). If we could make nanotubes out of iron, and if iron were the cheaper way to do that, we totally would. However, given the material properties we desire out of a nanotube, the atomic requirements in order to make that nanotube, and the cheapness of whatever we choose to make out of it (in this case, carbon), there's really no need to make it out of anything else.",
"Carbon naturally makes some ",
"pretty cool things",
" that have amazing material properties, mainly graphite (",
"graphene",
" sheets) and ",
"diamond",
", with the former possessing an interesting combination of flexibility, good strength-to-weight ratio, and electrical conductivity. These properties can be consummately used (nanowires, OLEDs) or selectively (a baseball bat or bike frame doesn't need to conduct electricity, but it does need to be light, strong, and flexible).",
"Iron as a material is actually quite brittle and prone to becoming rust, and the few very durable things that are made out of iron are prohibitively heavy for applications where carbon nanostructures dominate (imagine swinging with a cast-iron baseball bat vs. a carbon fiber one). ",
"To answer your question more generally, if we can find a material that possesses the qualities we want, we will use it. This is generally what happens:"
] |
[
"To get a little more technical, the reason carbon fibers exhibit such high tensile strength is due to the bonding between carbon molecules. Carbon will form a lattice of SP2 hybridized bonds, which you'll hear called \"resonant\" or \"aromatic\", but simplistically it means that it is forming stronger than usual bonds with its neighbors. A consequence of this is that it can only form planar sheets, which is why you end up with these crazy strong strengths in one direction, and weaker ones in others.",
"Sidenote: these resonant structures also have very unique electronic properties, which gives this class of materials (graphene, graphite, carbon nanotubes, fullerenes) a lot of interesting applications in electronic devices. "
] |
[
"If quarks that make up protons are excitations in their respective fields, how do they collide in the LHC?"
] |
[
false
] | null |
[
"Everything in quantum mechanics is a particle and a wave, but in some contexts (for example accelerator/beam physics), it's perfectly fine to envision them as particles with well-defined positions and momenta. In reality, they are wave packets, which are somewhat localized in both position and momentum. Much more so than any reasonable experimental resolution. So for those intents and purposes, they ",
" acting like particles."
] |
[
"I don't understand the question. Why would you think that those statements are at odds with each other?"
] |
[
"When first hearing about protons colliding I always used to visualize it as particles colliding but after learning that those are not particles per se but waves, I'm having a hard time understanding how those waves would collide."
] |
[
"What is the scientific significance of the Voyager missions?"
] |
[
false
] |
Apart from the psychological and historical value. What have the Voyager missions helped prove or disprove? Bonus question: What was the cost (in today's money) of both missions?
|
[
"They were hugely valuable scientifically! If you went through every valuable bit of data, it would take ages. Overall, the Voyager and Pioneer programs provided huge amounts of insight into the gas giants and their moons, conducted thousands of precision measurements and sent back thousands of high-resolution images of things that previously we could only observe with ground-based telescopes. ",
"I think it's safe to say the two probe progams pretty much revolutionised the understanding of the outer planets.",
"Watch all of these: ",
"http://cdsweb.cern.ch/record/908376?ln=en",
" ",
"The cost for the Voyager program was about $865 million, which is a bargain considering the scientific value for planetary astronomers, according to: ",
"http://voyager.jpl.nasa.gov/mission/didyouknow.html"
] |
[
"Thank you. I knew they were significant, but I did not know how much. ",
"$865 million is a lot less than what I thought it costs, considering, at the time, the cutting-edge technology and personal used."
] |
[
"No probs. ",
"The cost estimates are always a bit off, as it's hard to adjust the cost of manufacture and then running mission control over three decades of financial inflation. Overall, if that $865m is true, it works out to be less than the cost of just TWO Space Shuttle flights:",
"http://www.nasa.gov/centers/kennedy/about/information/shuttle_faq.html#10",
"Q. How much does it cost to launch a Space Shuttle?\nA. The average cost to launch a Space Shuttle is about $450 million per mission.",
"Which is astonishing value for money, really!"
] |
[
"What happens when opposite magnetic poles meet?"
] |
[
false
] |
There's a gif in of a n/s magnet in a container of iron filings in some kind of solution. The filings aren't attracted to the center. What's happening?
|
[
"If you look at the magnetic force between the magnet and one of the iron filings, it will in general have a component in the radial direction, but it scales like 1/(distance)",
". So it's very weak unless the dipoles are very close to each other."
] |
[
"So, is that saying there's a repulsive force of some kind there, or is it that there's so little attractive force there that the filing is just moving on the bent line of the field?"
] |
[
"I'm referring to the force given ",
"here",
" as a simplified model for this situation. It's not exact, of course.",
"The force between magnetic dipoles can be attractive or repulsive, but since the iron filings seem to be pretty well-aligned with the field of the magnet, the term which goes like ",
" is attractive.",
"If you consider one of the iron filings sitting in the midplane of the magnet, we have ",
" = ",
" = 0, and ",
" = -μ",
"μ",
".",
"So in this case, the force is attractive. The filing will feel a force toward the center which goes like 1/(distance)",
". This is very weak, and there are viscous forces from the medium which further inhibit the motion of the filing towards the center.",
"If you look closely at the GIF in question, you'll see that many of the filings actually are slowly drifting towards the center."
] |
[
"My high school cross-country coach always said it was better to breath through your nose while running. Is there any truth to this, and if so whats the science behind it?"
] |
[
false
] | null |
[
"You will suffocate trying to breathe only through your nose while running unless you are going at a pace that is way too easy anyway. Here's a thread of runners laughing at the idea that you are supposed to breathe only through your nose-",
"http://www.runnersworld.com/community/forums/runner-communities/beginners/mouth-v-nose-breathing",
"\"When it comes to taking in air, you have to get it from every place possible. It's also an advantage to a runner, or any athlete involved in aerobic activity to practice breathing properly and developing a strong and vibrant diaphragm muscle.\"",
"Here are pictures from the Olympic marathon. These people are not breathing through their nose only-",
"http://www.guardian.co.uk/sport/gallery/2012/aug/12/london-olympic-mens-marathon-pictures#/?picture=394618582&index=0",
"Their mouths are slightly open, as they are taking in as much air as possible by breathing through their mouth and nose at once.",
"Here is some science on why-\n",
"http://www.topendsports.com/resources/research/nasal-oral-breathing.htm",
"You can see that the nasal breathing is statistically lower in VO2 etc. than oral breathing."
] |
[
"The sinuses have turbinates to actually smooth out airflow, and allow more time for it to reach body temperature. They're better at humidifying the air than the lungs are as well, meaning that you're not losing fluid inside the lungs and making the secretions inside the lungs thicker, and thus harder to remove.",
"This is no way aids in the diffusion of oxygen, I don't know where you get that bit of information from but it's entirely wrong. Air that participates in gas exchange will be 100% saturated and body temperature, period. It's a matter of whether it's drying out lung tissue to do that.",
"From this book",
" and many other textbooks."
] |
[
"When you breathe through your nose, the air flow is turbulent in your sinuses. This causes the air to not only warm up to body temperature, but also adds water vapor to the air. The aids in the diffusion of Oxygen once the air reaches your lungs."
] |
[
"If a pregnant woman requires a blood transfusion can the woman’s blood type be used or is O- blood needed due to the child’s potentially different blood type?"
] |
[
false
] |
[deleted]
|
[
"A woman’s blood supply does not mix with the baby’s. The placenta acts as an exchange point for nutrients and oxygen, otherwise the mother’s blood cells would develop antibodies to attack the baby’s cells. Sometimes red blood cells do manage to mix which happens closest to childbirth, and that’s what causes jaundice and anemia in babies. ",
"So in essence, a woman would receive her blood type. Women who have Rh negative blood who are pregnant with an Rh positive baby can also have these issues occur, it’s called Rh Disease. You can get shots and antibodies or something to prevent the chance of blood type related issues causing miscarriage. ",
"Hope that helped! "
] |
[
"I seem to remember \"mother's immune system attacking the baby\" among my nightmare scenarios when I learned I was going to be a father years ago. Is that something that actually happens during pregnancies?"
] |
[
"The antibodies created by red blood cells can cause a rejection of the pregnancy. In extremely rare cases, if your bloodstream is filled with NK cells (natural killer cells- they fight cancer and foreign objects in your body), they can treat the embryo and hormones as a foreign body and kill it before it implants in the uterus properly. "
] |
[
"Does vasodilation cause an appreciable change in blood pressure?"
] |
[
false
] |
I'm a secondary school science teacher in the UK. I'm currently teaching about homeostasis and negative feedback loops (this isn't my specialism). We talked about how when you are warm your blood vessels in your skin dilate to dump heat out of your body. A student asked if this would change your blood pressure and if so, how does your body react to the change? I admitted I was stumped, the only thing I could think of was that it probably wasn't an appreciable change, and I promised I would find out the correct answer for them. EDIT: punctuation and incoherent rambling sentence.
|
[
"Indeed it does.",
"In severe cases of vasodilation—septic shock, as an example, where blood vessels are dilated throughout the body in response to infection throughout the body—the resulting drop in blood pressure quickly becomes lethal.",
"In milder/more localized states of vasodilation, the heart can usually compensate by ",
"beating a little faster."
] |
[
"I was taught like this in school but it was a long time ago so any expert may correct me!",
"The average blood pressure during a heartbeat is the Mean Arterial Pressure (MAP)",
"It is determined by how much blood the heart pumps (CO) (which itself is determined by how fast and strongly it beats) and the resistance of the arteries (AR)",
"The formula is this MAP = CO × AR.",
"When the vessels dilate, the arterial resistance lowers. As such, the blood pressure lowers too.",
"But the body can compensate by adressing the other factor: how much blood the heart pumps. The heart will pump a bit faster and more strongly"
] |
[
"Pretty good but it's SVR (systemic vascular resistance) rather then AR"
] |
[
"Is there any way to transmit power through the air like envisioned by Nikola Tesla, on the scale of providing wireless power for a small city?"
] |
[
false
] |
We use electromagnetic radiation for all sorts of things like communication, but I am curious about transmitting enough power wirelessly to handle a small city's lighting, heating, and all of its electrical power requirements.
|
[
"Nobody knows how Tesla was going to accomplish his claimed feat. He said that he'd worked it out in practice, but wouldn't reveal details when questioned by reporters.",
"Either he was a crackpot who was lying about having got it working ...or he had some trick up his sleeve which we modern engineers still don't know about. (And scientists today are sure that he was just a lying crackpot, since there cannot be any such unknown tricks which would allow his sytem to work has he described.)",
"He did leave behind an 1899 ",
"magazine illustration",
" of his ",
"city-wide power sytem",
" in operation. It involved tethered balloons which lifted some sort of ray-generators aimed downwards at the city. WTF?! Well, each time his contemporaries insisted that his system was based on EM waves, Tesla was adamant that it absolutely was not \"Hertzian.\" Maybe he was right? But without knowing what was actually in his head, we might as well just assume that Tesla was a crackpot who had no idea what he was talking about.",
"Years later other researchers apparently ",
"were working on a similar scheme."
] |
[
"Electromagnetic induction does work for power transfer.",
"The problem is efficiency - and i have a hard time to imagine powering a city with it by any other means then having ",
" of induction sources.",
"If you want some decent level of efficient directional energy transfer, you could use microwaves. That would have to be between static points."
] |
[
"What is the difference between a Hertzian wave and a non-Hertzian wave? "
] |
[
"Reddit, you’re my only hope! This is such a taboo subject, I can’t get a conversation going: historical gene-pools and evolution"
] |
[
false
] | null |
[
"Just want to make this clear to everyone:",
"/r/askscience",
" ",
"Thanks, have a wonderfully scientific day!"
] |
[
"You're not the only one asking this question. The debate is pretty strong in the scientific community, most of it hinging on scientific ethics. As an example, I'll link to one commentary on Nature (paywalled) and another article on the Independent (free) that both show the debate and the hot water into which such assertions can land people:",
"http://www.nature.com/nature/journal/v457/n7231/full/457786a.html",
"http://www.independent.co.uk/news/science/fury-at-dna-pioneers-theory-africans-are-less-intelligent-than-westerners-394898.html",
"So here's the thing: much research was conducted in scenarios where ethics in science were tossed. I point to Japanese research camps as a significant example. See ",
"Unit 731",
" for more information, and note that this isn't the only instance where a lack of ethics led to research that was deemed valuable. I'm only citing the first case that came to my mind.",
"The only way such topics can be probed is if such research is done in secret or if everyone changes their mindset towards disregarding political correctness and moral violations in scientific research. The argument against this is that the former encourages the latter and that the latter cannot be achieved with everyone on the planet anyway.",
"Therefore, as the research cannot be conducted under our ethically sound rules, the best anyone can do is wait until another ethically and morally derelict regime comes to power and conducts the research which gives the world conclusive evidence in any one direction or another. Until then, all anyone can do is speculate. One may construct syllogisms entertaining the idea that race and intelligence may be linked, but ",
" For those of you downvoting, if you could please provide a justification as to where my conclusion is unscientific in the context of the thread, I'd appreciate the feedback."
] |
[
"Well, in the end, the issue is the differing environmental conditions make it difficult to separate heritability from environment.",
"BUT, Razib Khan makes the argument ",
"here",
" that the standard of living in the modern West makes heritability the major factor of intelligence these days (in the West.)",
"But, there's all sorts of weird confounding factors when dealing with so many genes, like:\n",
"http://dienekes.blogspot.com/2010/01/height-iq-gender-interplay.html",
"That paper shows correlation between height and intellect, so therefore since men are taller, they are smarter. (But tall women are smarter than tall men.) Wat? Who knows. Nutrition, maybe.",
"Watson caught a lot of flak",
" for his statements on sub-Saharan intelligence. Sub-Saharans score low on IQ tests, and he suggested it might be genetic. In, and of itself, that statement shouldn't have raised as much ire as it did. But, the environmental factor can't really be excluded in this case.",
"(And IQ is a reasonable metric of ",
"g",
", gosh darn it.)",
"Here's",
" a link to a link of a literature review of Sub-Saharan IQ. But, again, Sub-Saharan Africa is a horrible place to live....",
"So, really, to make any sort of comment on genetics vis a vis intelligence in a population, I agree with Razib Khan you have to look at developed nations.",
"But, the subject itself ",
" taboo. For several reasons, the major one, these days, I think is that people don't like the idea of",
" genetic determinism",
". Moreover, research in the area can always be appropriated, incorrectly, by racist groups to advance an agenda.",
"But the idea that certain populations possess alleles in higher frequency that lead to the phenotype of higher IQ shouldn't be anathema. But it is.",
"I mean, look at this:\n",
"http://dienekes.blogspot.com/2012/03/rare-look-at-y-chromosomes-of.html",
"\nWithin 1 country - Afghanistan - the major ethnic groups are distinguishable via Y-chromosome markers. If they differ in one genomic area, is possible that actual coding allele frequency (for all sorts of traits) are also distinguishable? Of course it is. (But full genome sequencing is expensive.)",
"If you just scroll through Dienekes' blog, you'll see dozens of papers that can distinguish populations - ",
"you can even get Latitude and Longitude estimates based on genetic markers (because panmixis doesn't exist irl.)",
". Again, these are non-coding regions of DNA being used. (Because non-coding regions mutate faster than coding regions, and thus make distinguishing populations easier.) Yet, still, if panmixis were in place, distinguishing people to such a fine degree would be impossible. Since panmixis does not exist (as we can see), then it stands to reason that allelic frequencies between populations also differs considerably. "
] |
[
"What are some good starting books on nuclear chemistry (or just the overall subject)?"
] |
[
false
] | null |
[
" by Loveland, Morrissey, and Seaborg."
] |
[
"Thanks for the response! Would someone like me be able to understand the text if I only have taken general + organic chemistry? How much knowledge should I be prepared to have when reading this book?"
] |
[
"Yes, it starts from the basics. You should be aware that nuclear chemistry is not much like the other branches of chemistry. It doesn't really build on things you learn in organic, analytical, etc. chemistry courses. It might help if you had had some physical chemistry, but this book starts from the basics and works up.",
"Nuclear chemistry as a subject is more like nuclear physics than \"traditional\" chemistry. So your standard advanced chemistry courses are not pre-requisites for learning nuclear chemistry, it's like a standalone subject."
] |
[
"If the universe is accelerating, does this mean that we are still, in the grand scheme of things, in the early parts of universal expansion?"
] |
[
false
] |
I watched an interview with Neil deGrasse Tyson where he was explaining how astrophysicists discovered that the universe was accelerating in its expansion, and nobody knew why (as gravity should be slowing it down). Would this mean that the initial explosion that was the big bang was so powerful that even today, because it is accelerating in its expansion, the initial force of that explosion is still pushing the universe at a growing rate? Meaning that this universe is still relatively young? I'm no astrophysicist, but the idea of the big crunch/big bounce makes sense to me. To illustrate the point, would this essentially mean that we are in the very early stages of a bounce? Like, if you throw a baseball straight up, it will accelerate at first and then decelerate from gravitational force. So, is the universe that baseball right as it's been released from the hand, still accelerating from the initial force that launched it?
|
[
"First of all, your baseball analogy is a little flawed. A baseball is only accelerating upward while it's in the hand. The instant it leaves the hand, it begins slowing down due to gravity (and air resistance). If we're to go with this analogy, then we're still \"in the hand\", and it's not clear whether we'll ever be \"let go\", or stop accelerating. Dark Energy is the name of the cause of the acceleration, and so far no one really knows what it is.",
"That said, I believe the growing consensus is that the universe will ",
" reverse into a big crunch, but will continue expanding forever. If this happens, it probably means we are indeed in the very early part of the universe's life. If time is infinite, you might say there's no such thing as the end. However, if you want to pick an event to call \"the end of the universe\", you might pick, say, the death of the last star, which ",
"according to Wikipedia",
" will be somewhere between 1 and 100 trillion years from now. Being that the universe is only 13.8 billion years old, we're still near the beginning, by that measure."
] |
[
"If I recall correctly there has been some speculation that certain patterns in the CMB were caused by pre-Big Bang structures, eg ",
"http://en.m.wikipedia.org/wiki/Conformal_cyclic_cosmology"
] |
[
"Note that you don't take up the third option, which is that we end our own existence, probably due to shortsighted greed or inter-tribal conflict.",
"Do you still think he/she was being pessimistic?"
] |
[
"Why (or how) do different musical notes/tones evoke different emotional and psychological responses in us? (The kind of string music they play when a killer in a movie is looming, for example)"
] |
[
false
] | null |
[
"I was disappointed that no one had any answers here yet because I am curious as well. I do remember hearing that minor chords evoke feelings of sadness or melancholy while major chords tend to evoke happier emotions. According to ",
"this paper",
" this is why: \"the minor third was the most reliable cue for identifying sadness. Additional participants rated musical intervals for emotion, and their ratings verified the historical association between the musical minor third and sadness. These findings support the theory that human vocal expressions and music share an acoustic code for communicating sadness\". So basically minor chords mimic the cadence and tone of a human speaking while sad. I would imagine it's something similar with discordant sounds mimicking potential threats in our environment. "
] |
[
"Thank you!"
] |
[
"My guess is that it's mostly cultural. If you listen to music from other cultures, you don't see the same associations between minor keys and sadness for example.",
"In your specific example, I think a couple of things are going on. In the context of Western music, dissonance can be unsettling. Film makers have been using dissonance and sharp chord sounds for a long time in horror movies. My favorite horror movie score is Psycho, from 1960, which has that very distinctive \"DUN DUN DUN DUN\" string sound (it's an awesome movie sound design wise in general; if you watch it, pay attention to how silence is used.) In addition to unsettling properties of the music itself, as similar music is used in scary movies, we begin to learn that music means a killer is coming. So you can think of it in a classical conditioning paradigm, like Pavlov's dog. We hear the music, then get scared, and come to associate the music with feeling scared or anxious."
] |
[
"Do the principles of relativity apply to angular velocity as well as linear velocity?"
] |
[
false
] |
I understand the relativity of linear velocity. - I.e. all frames of reference are valid, and there is no singular universal frame of reference (e.g. It is equally valid to state that the sun moves at a given velocity relative to Earth, or vice versa - or that the solar system moves at a given velocity relative to Sagitarius A, etc.) Does this apply to angular velocity as well? E.g. if I went into space and applied a force to put my body into a spin, would it be equally valid to make a reference frame statement that the rest of the universe is rotating around me rather than that I am rotating? If not, why? If yes, the mental hiccup I'm having is realizing that I'd still get dizzy - implying that there is some sort of force still at play in this rotation.
|
[
"A rotating reference frame is non-inertial, meaning that light rays in such a reference frame move on curved paths, and spatially separated clocks at rest with respect to a rotating frame cannot stay synchronized.",
"It's still perfectly valid to consider such a reference frame in special relativity, but the laws of physics take a different form in rotating frames as opposed to inertial ones."
] |
[
"No, relativity doesn't apply to rotation. You can tell if you're rotating because of Coriolis and centrifugal forces; this is how a Foucault pendulum works."
] |
[
"Galilean and special relativity both state that in all ",
", meaning non-accelerating, frames of reference the laws of physics take the same form.",
"A rotating frame of reference is accelerating (it does not just move at constant linear velocity), therefore you get nasty effects like centrifugal and Coriolis forces in your equations of motion. This is what makes the difference between inertial and non-inertial reference frames, and it is also why you get dizzy."
] |
[
"Why do I see colors when I close my eyes?"
] |
[
false
] |
For example, when I go to bed in a dark room and I close my eyes, I see colors and patterns and such. It all seems random, sometimes a consistent pattern can occur. What is this and what causes it?
|
[
"Your eye and optic nerve, when lacking stimulation from light, produce their own signals which are interpreted by the brain as random patterns of colours."
] |
[
"That's interesting, hm."
] |
[
"Phosphenes."
] |
[
"To what degree can the safety of previous vaccines be generalized to the Covid-19 Vaccines? How generalizable is previous safety data to a given new vaccine?"
] |
[
false
] | null |
[
"If it’s the same type of vaccine and uses the same dosage of adjuvants, the safety data from an older vaccine could give you a very good idea of what to expect safety-wise. More often than not, adjuvants are the cause of negative side-effects. That being said, there is still a chance that the antigen used can cause toxicity as well, especially if the antigen’s native function is to subvert your immune system or have some other physiological affect on your body. Usually vaccine researchers go out of their way to pick an antigen with very little likelihood of having such functions, like the covid spike protein.",
"Definitions, if needed:",
"Adjuvant - the compound in a vaccine that stimulates your immune system.",
"Antigen - a compound, usually a protein, derived from the pathogen you want to building lasting immunity to. This is the target your immune system will recognize when you get infected with the real pathogen."
] |
[
"I recently found this article. I'd definitely recommend it for anyone concerned about the potential unnoticed side-effects given the \"rushed\" development.",
"https://science.sciencemag.org/content/early/2020/11/16/science.abf0357"
] |
[
"That is a very informative article, thank you for sharing it. What that analysis lacks is discussing the tradeoffs in the context of a global pandemic where thousands of people a day are dying. A zero-risk vaccine is probably not the answer here, IMHO."
] |
[
"How did the planetary cool-down of Mars make it lose its magnetic field?"
] |
[
false
] | null |
[
"Mars' magnetic field is thought to have a very similar origin as Earth's magnetic field. It is created by ",
"dynamo action",
" in the molten core.\nFor this dynamo to occur several conditions need to be met. ",
"You need a conductive fluid, i.e. molten iron. ",
"Kinetic Energy (provided by the planetary rotation)",
"An internal heat source that causes convection in the liquid conductor to occur (heat from the formation of the planet, radioactive decay, differentiation of the planets interior, etc.)",
"It is thought that Mars' internal heat source is too weak to drive the convection needed for the dynamo action to occur. We don't know for sure yet. But now we have a very accurate seismometer on Mars onboard of the Mars Insight lander. We will get more accurate data about the planetary interior. It will be an important part to get some certainty about Mars' magnetic field."
] |
[
"Nuclear power pretty much powers life from all sides. Sun's nuclear fusion powers feeds all of life, it's suspected at least some radiation helped jump start lifeforms on earth, and it helps maintain our own planet's core and magnetic field.",
"We're absolutely are nuclear powered."
] |
[
"Even if nuking a planet’s interior was doable the amount of energy required would be colossal. Much of the heat generated within Earth’s core comes from radioactive isotopes decaying over time, which cumulatively add up to far more energy than we could ever hope to inject."
] |
[
"AskScience AMA Series: I'm Eric Noel Muñoz and I helped in the eradication of \"Killer Algae\" on the coast of Southern California. Environmentalist and Brady Bunch actor Christopher Knight will be joining me. Ask Us Anything!"
] |
[
false
] |
Hi, my name is Eric Noel Muñoz. A life-long ocean lover with a degree in physical geography from San Diego State University, I wrote about how Agua Hedionda Lagoon in northern San Diego County eradicated an invasive species of seaweed between 2000 and 2006 which was most likely released from a home aquarium. This strain of Caulerpa taxifolia (nicknamed "Killer Algae" for good reason) is a mutant genetic clone of a natural counterpart; it has no predators, keeps fish away, grows rapidly and smothers reef or rocky substrate, and reproduces via fragmentation. First detected in the Mediterranean Sea and now in over half a dozen countries there, it also is in Southern and Eastern Australian wetlands. As a Carlsbad city planner and later lagoon foundation president, I had many roles in the eradication effort and outreach efforts from 2000 through 2015. The book is a personal account which covers the issue from many angles and includes time spent in New Zealand, Australia, Croatia, France, and Monaco. Our local effort—the only known successful eradication of an invasive marine species—is put into a global context and outlines the success of our rapid response that combined funding, science, and policy. You can check out my book on or directly from the publisher, . You can watch my 3-minute TED animated video here: For my AMA session, I will be joined as necessary by a consulting biologist/scuba diver who was part of the eradication team, Robert Mooney, Ph.D, of Marine Taxonomic Services in San Marcos, CA. Christopher Knight, environmental activist and Peter Brady from will be on from 12:30 to 1:00 PST and can chime in on any questions about his work with community outreach regarding . I look forward to your questions on everything from our efforts in California to the situation in the Mediterranean and in Australia, plus whatever else you might think up. I’ll be on from noon to 2 p.m. PST. AMA! Eric's publisher here! Eric has signed off for the night since he has a book signing to go to (California Surf Museum in #Oceanside from 6-8 p.m for anyone local) but wanted me to let you all that he really enjoyed the exchanges and the experience of hosting an AMA. We hope you'll give the book a read ( ). Feel free to contact Eric with any other questions or if he didn't reach yours in time; his email address is in the back of the book! Thanks everyone, and thanks to the mods for a great time!
|
[
"Since you're good with killer algae can you please come check out the situation in Martin County, Florida with the toxic algae blooms caused by the releases from Lake Okeechobee? We are loosing hundreds of dolphins, manatees and there is now a large fish kill. Our government is unwilling to do anything to resolve the problem and this is being ignored at a federal level. ",
"Edit: Here are some articles to what I'm referencing.",
"http://www.tcpalm.com/news/indian-river-lagoon/health/high-levels-of-toxins-from-algae-at-4-test-sites-in-martin-county-379cc3be-928b-474f-e053-0100007f3d-386998721.html",
"http://www.wpbf.com/news/report-shows-extreme-toxicity-at-4-bodies-of-water-in-martin-county/40723340",
"http://www.palmbeachpost.com/news/news/local/blue-green-algae-coming-up-on-shore-closes-some-tr/nrnpj/",
"http://www.palmbeachpost.com/news/news/report-algae-shutting-down-martin-county-beaches-s/nrnWD/",
"http://www.wptv.com/news/region-martin-county/stuart/martin-county-holding-emergency-meeting-over-algae-tuesday"
] |
[
"There's a similar problem in Utah right now as well. ",
"https://www.ksl.com/?sid=40666305&nid=148&title=health-officials-shut-down-utah-lake-over-algal-bloom-concerns",
"https://www.ksl.com/?sid=40725118&nid=148",
"I wonder if there's some kind of climate connection or something going on. Fertilizer pollution may also be a factor. "
] |
[
"Fertilizer from the sugar industry is the factor down here in FL. But the issue is our politicians are quite literally paid by them so they don't regulate that industry. It's been like this for years but my home town of Stuart doesn't have much of a voice compared to the money sent by the sugar industry."
] |
[
"How does the food, medicine, drink that we take go to specific parts of our system?"
] |
[
false
] |
Examples like, when eating food. How does the food that we take distribute specific nutrients to specific parts of our system? When we take our vitamins, how do the vitamins get properly distributed to certain parts of the system like if the vitamins is specialised in nourishing bones, eyesight, hair growth, skin nourishment, or even viagra? It just blows my mind on how all the different substances we take end up doing what it's supposed to do, whether its for remedy or nourishment.
|
[
"For the most part, they don't get ",
" distributed, they just get distributed. How or whether a cell in that tissue uses any particular molecule in the interstitial fluid is up to that cell. ",
"That said, things aren't evenly distributed, since certain organs and tissues get more blood flow than others, so that can have an effect on biodistribution. Also, hydrophobicity of a molecule, charge, and size all play a role in what biological compartments a molecule ends up in. For example, some molecules are more likely to stick to serum proteins like albumin and get filtered out by the liver, while others are more likely to get filtered out by the kidneys."
] |
[
"In general, stuff gets dumped into the blood and cells individually pick out what they need/want using various methods. The distribution there is a result of the cells rather than the method of transport."
] |
[
"How do you explain the function of ANGPTL3/4 or 8, or ApoC1/2/3, or ApoE? What about FABPs? Or insulin, ghrelin, and glucagon?"
] |
[
"Does the expansion of the universe, which is apparently accelerating, violate the conservation of energy?"
] |
[
false
] |
Why hasn't entropy slowed the expansion of the universe?
|
[
"This question is one of our ",
"FAQs",
", and the answer can be found ",
"here",
". The summary is that it can be interpreted that the Universe does not need to conserve energy, as it is a system which varies with time - however, some alternative possibilities are pointed out in the answer and the articles it links to."
] |
[
"It may violate the conservation of energy, but not in the way you're thinking. Expansion isn't ",
". It doesn't involve things ",
" away from each other, but rather the space between them growing over time. This is why, for instance, some locations in space are gaining more than 1 light second of distance per second of time (what would appear to be travelling faster than light away from us). ",
"The way it may violate energy is that we observe the universe to have some additional form of energy that is pervasive everywhere and it's that type of energy that \"drives\" the expansion of the universe. We don't have much more detail about it than that. But what's interesting is that ",
" that as more space is added between bodies in the universe, this type of energy isn't diluted. So... it's ",
" new cosmological constant energy is being created to \"fill\" the new space that's being created over time.",
"And as the FAQ gets into, that's okay. Conservation of energy isn't expected to hold over cosmological scales anyway, explicitly ",
" of the expansion of space-time."
] |
[
"This may be outdated but the way I heard it explained was that a stuff (dark matter or dark energy I forget which) basically has effects that are the opposite of gravity. So the way i think of it, with gravity, the closer you get to the source, say earth, the stronger it pulls you in. If the universe is expanding with the opposite of gravity then the farther you get the harder it pushes you away. And about the conservation of energy I think that it is because of potential energy. On a planet if you pull something away from the surface you get potential energy and when you let go it falls back to earth. Is a similar fashion at the beginning of the universe all the dark stuff had everything very close so it had a lot of potential energy to push away and over a long time it is pushing away faster using the potential energy it had",
"All of this could be wrong but from what I have been taught this is my explanation"
] |
[
"Do radioactive materials actually glow green? If not, do they glow at all?"
] |
[
false
] |
Also: If not, where did the idea of radioactive = glowing green come from?
|
[
"Note that the tritium itself does not glow green, it basically acts as the power source for a phosphor in your watch. ",
"source."
] |
[
"That's a good guess, but the reason Cherenkov radiation is blue is due to the spectrum given off by Cherenkov radiation itself, rather than it being a scattering effect. Cherenkov radiation is stronger at higher frequencies (the spectrum is governed by the Frank-Tamm formula, if you're interested), which means the radiation spectrum will be brighter at the blue end of the spectrum than the red end (actually, it's substantially brighter in UV than in visible for that matter)."
] |
[
"I believe the association with green glow comes from the watches with green-glowing radioactive dials, which as ",
"trickyben2",
" notes, doesn't actually come from the radioactive material itself.",
"Highly radioactive stuff (mainly beta-emitters) can give off ",
"Cherenkov radiation",
", caused by charged particles moving faster than the speed of light in the surrounding material (that is, moving faster than light does in that material, not moving faster than light does in vacuum, through that material). It's usually blue-ish.",
"'Radiation' is either particles or gamma radiation, neither of which are visible in-themselves, so any glow would come from the interactions with the surroundings. So it depends on the radiation and the surroundings, but in most situations, radioactive stuff simply doesn't glow. "
] |
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