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[
"Is hypnotism a myth?"
] |
[
false
] |
[deleted]
|
[
"check out ",
"feynman's description of being hypnotised",
". he addresses the \"faking it\" thing:",
"He started to work on me and soon I got into a position where he said, \"You can't open your eyes.\"",
"I said to myself, \"I bet I could open my eyes, but I don't want to disturb the situation: Let's see how much further it goes.\" It was an interesting situation: You're only slightly fogged out, and although you've lost a little bit, you're pretty sure you could open your eyes. But of course, you're not opening your eyes, so in a sense you can't do it."
] |
[
"check out ",
"feynman's description of being hypnotised",
". he addresses the \"faking it\" thing:",
"He started to work on me and soon I got into a position where he said, \"You can't open your eyes.\"",
"I said to myself, \"I bet I could open my eyes, but I don't want to disturb the situation: Let's see how much further it goes.\" It was an interesting situation: You're only slightly fogged out, and although you've lost a little bit, you're pretty sure you could open your eyes. But of course, you're not opening your eyes, so in a sense you can't do it."
] |
[
"Hi! Hypnotist here. Hopefully I can help shed some light on these questions for you.",
"1) What is a hypnotic state?",
"This will be the most difficult question to answer. Especially because even among hypnotists there are state versus non-state theories. I'll give you my personal take on things, though. ",
"It's important to realize first that there is no specific point where someone is hypnotized. I'd say this is the biggest misunderstanding of all. Rather, it's all in degrees. To define it loosely, though, a hypnotic state is a point where major brain activity has decreased (more on that later) and a person has entered a suggestible state where they are more likely to comply with suggestions given to them.",
"Sound vague? That's because it is. As I was saying, there's no exact point where a person is hypnotized. Certainly, when they reach deeper levels, it's extremely identifiable. They'll have such bodily reactions as entering REM, shallow breathing, and catalepsy. But there are also extremely light forms of trance, where you can barely even be sure the person is in one at all.",
"An easier way to measure these things is to hook someone to an ",
"EEG",
". You can actualy see a measurable change in brain waves when a person is put into a hypnotic state. It's important to note that these states are entirely natural. The only difference is that they are being purposefully induced. While our brains enter the alpha wave length all the time, normally having someone talk to us would snap us out. ",
"This, I would say, is a uniqueness to the hypnotic state.",
"2) Why and how does the body enter one?",
"Here comes the fun stuff! Actually, you can enter into a trance in a plethora of different ways. Just about anything can be hypnotic. The important detail is that you need some sort of stimuli to alter the way your brain is processing things. The most well known method is through what's known as the relaxation induction, but there are many more techniques. You can even be surprised into hypnosis!",
"The concurrent theme, though, is things that cause your brain to give up on processing complex data. Specific to purposeful induction, a hypnotist wants to change your brain function so that you are still concentrating on what is being said to you while entering this altered state. This is what separates actual hypnosis from the naturally occurring state I mentioned earlier. ",
"The basic idea here is that when your brain is \"relaxed\" into a different wave length, ",
" still concentrated on the input being provided, it becomes less circumspect in what it accepts as \"truth.\" The conscious mind is generally your \"bullshit\" detector, and with it out of the way you will find yourself more receptive to the input. This manifests itself in therapeutic techniques (convincing the mind you no longer want to smoke) as well as more fun stuff (convincing your brain that, hey, you just won the lottery and should do a silly dance to celebrate!).",
"There's actually loads more to say on this question, but you could literally write books on this (and people have!). So hopefully that answers your question well enough, and if not I can elaborate.",
"3) Why isn't it used more often in place of placebos?",
"Throughout the past couple of centuries, hypnosis has fallen in and out of favor with the scientific and medical community. In small pockets, hypnosis is readily embraced. There are dentist offices out there that will offer hypnosis in lieu of anesthetic. And there are offices in every major city offering to help with quitting smoking.",
"The biggest reason it hasn't ever fully caught on, though? This is personal opinion, but: I think it's too much of a soft science. There's too much that hypnotists can point to and say \"Look, it works!\" But when you ask why, all we can do is offer you theories. And it doesn't have anywhere near uniform results amongst hypnotic subjects.",
"Finally, as wolfganghox points out, ",
" to be hypnotized is almost paramount to success with most people. And how can the medical/scientific community ever embrace something that has such a requirement? For many, this is enough to dismiss it along with homeopathy and other non-scientific approaches.",
"But hypnosis is quite real. I've worked as a stage hypnotist, a therapist, and just hypnotizing friends and loved ones to see what limits we could find. And if there's any one thing I've walked away from it with, it's that much. Hypnosis is real. And you can do absolutely amazing, mind-boggling things with it. But until we have a specific understanding of exactly what happening, and way to make results more uniform, I don't think it will ever be totally accepted by the mainstream.",
"I hope this helps."
] |
[
"At this point, why isn't the COVID-19 vaccination required for grade school students?"
] |
[
false
] | null |
[
"Not really a science question but more of a policy one. Perhaps try a politics-related sub"
] |
[
"Perhaps you're right. I chose ",
"r/askscience",
" because crossing into politics is a complete mess I'm uninterested to involve my time with. Politics shouldn't influence protecting my (our) children, which of course protects you, them, me, us, etc. My post is somewhat vague I suppose, but I'm questioning why at this late in the game would an immunization for Hep B, Varicella, DTaP be required yet a soon to join kindergartener doesn't need a C19 vax?"
] |
[
"*More specifically, what warrants mandatory immunization?"
] |
[
"May sound stupid but here goes , when we are in the womb and are slowly growing where do those atoms come from that make us or do we make those atoms in the womb ?"
] |
[
false
] | null |
[
"They come from the food your mother eats while you're developing, as well as your mother herself. No new atoms are created, just rearranged cleverly from food and air and water."
] |
[
"I would add that you can't make atoms without an enormous amount of energy. E=mc",
" where mass is m, c is the speed of light and E is energy. Energy in the universe can not be created or destroyed. All elements bigger than hydrogen were created in stars or explosions of stars (except for a few heavy elements like plutonium that as far as we know only humans have made). Hydrogen was made in the first few seconds after the big bang. So you need at least the energy of a star or a supernova if not the birth of a universe to make your own atoms."
] |
[
"Thankyou my greatest mystery has been solved"
] |
[
"Why is it that you can put so much weight on one side of a barbell without it tipping over?"
] |
[
false
] |
I was at the gym today and I was able to put 90 pounds on one side of the barbell without it tipping over. Why doesn't any imbalance of weight cause it to tip over?
|
[
"If the barbell is supported at each end, then it won't tip over until it's center of gravity is outside the interval between the points where it's supported. If those points are quite close to the end compared to the length of the bar, then the weight you add needs to be much larger than the weight of the bar alone to bring the center of gravity that far over.",
"Another way to think of it is to consider the torque around the end where it would eventually tip. That point of contact is the pivot point, and the torque each weight applies is weight times distance from this pivot. For the weights you're adding, that's a large weight times a short distance. For the bar, that's a small weight times a large distance (half the distance between the supporting points). So the weights your adding need to be proportionally that much heavier than the bar to make up for how much closer their centers of gravity are to the pivot point."
] |
[
"This explanation is correct, just wanted to add something.",
"For the bar, that's a small weight times a large distance (half the distance between the supporting points)",
"In addition, barbells aren't light. 20kg is standard. That's lighter than two plates (90lbs = 40kg) but only by a factor of 2."
] |
[
"Using dimensions obtained from: ",
"http://www.allaboutpecs.com/wp-content/uploads/2013/04/olympic-bar-dimensions.png",
"The distance between the collars of the barbell is 131 cm, so that means the center of mass of the barbell is about 65 cm from the collar. The collar is where the bar would pivot if you place too much weight on the end (assuming the bar makes contact with the rack at this point). What determines whether a rigid object will rotate is the torque on the object, which is a product of the force and the distance to the pivot point.",
"So the center of mass provides a torque of (45 lb)x(65 cm) to oppose the rotation that would be created by the plates. Now, how much weight can you add to the end? First of all, the plates will be at least 3 cm from the pivot because of the collar's 3 cm thickness. This will depend on the thickness of the plates. I will use a 20 kg (~45 lb) olympic plate which usually has about a 4 cm thickness. Its center of mass is halfway through this thickness, so that means each plate will act 2 cm further from the pivot.",
"So for 1 plate, the torque is (45 lb)x(3+2cm), for two plates the torque is (90 lb)x(3+2+2cm). If you keep adding plates you'll get to 5 plates providing roughly (225 lb)x(13 cm) = 2925 lb-cm of torque. Interestingly enough, this is exactly equal to the (45 lb)x(65 cm) = 2925 lb-cm torque provided by the bar.",
"So, theoretically, you should be able to get about 5 20 kg plates onto the thing before it tips. But of course this all relies on the exact dimensions of your bar and plates. Also the bar doesn't usually sit in a rack that is exactly only equal to the width of the collars, so the 65 cm lever arm distance for the center of mass will in reality be slightly smaller."
] |
[
"How are sunglasses made to block UV light?"
] |
[
false
] |
I've seen conflicting information on exactly how sunglasses are made to block UV light. Some people say that the plastics used in the lenses naturally blocks UV light so that even the cheapest sunglasses will do an excellent job, while others say you need special 'treatments' to make them UV blocking. So do the plastics used in the lenses for sunglasses naturally block UV light? If not, what 'treatments' are applied to them to make them block UV light? Do these 'treatments' degrade over time? Do they rub off?
|
[
"The clear plastic (CR-39) used in typical eyeglasses is a ",
"pretty good UV blocker",
" on its own. Polycarbonate, another common material, is ",
"even more opaque to UV.",
"Add a gray tint, and it becomes an ",
"effective UV filter",
".",
"There are coatings that can be applied to any plastic to reduce UV transmittance to zero, and they don't rub off, but I wouldn't pay any extra for it.",
"I will gladly sell it to you though, if someone has convinced you it's necessary.",
"*Edit: extra word word"
] |
[
"Polarizing lenses are tinted plastic so they have the UV characteristics of tinted plastic, independent of their polarizing effect. I don't think anybody sells polarized lenses for the UV benefits. Well, unless you want...",
"There are two classic situations where polarized sunglasses really pay off.",
"Light reflected off the horizontal surface of water happens to get polarized. When you look into a fish pond unaided, the fish are obscured by the reflection of skylight off the surface, and much of this reflection is polarized. Put on a polarizing filter and the reflection mostly goes away so you can see into (clean) water quite well. ",
"Second example: you won't drive on a sunny day with white papers on the dashboard because the paper reflects badly against the windshield, obscuring your view outside. Put on polarized sunglasses and the reflection goes away, mostly.",
"Sunglass lenses are made with the axis of polarity positioned for these effects. In either case, if you rotate the lenses 90 degrees, or look sidelong down a plate glass window, the objectionable reflections are ",
" rather than better.",
"On the down side, LCD displays are polarized, and if they aren't oriented with this in mind, things like gas pump readouts appear completely black when you put on polarized glasses. The FAA forbids polarized glasses in the cockpit because many avionics displays are LCD. Automobiles aren't so closely regulated, but my Subaru displays are polarized at a 45 degree angle."
] |
[
"What about a polarizing filter? I know what it does, but why people slap it on to sunglasses? Do polarized lens make the glass more \"UV resistant\"?"
] |
[
"Have we been able to bond any noble gas element with any metal, and if so, what is the longest we've been able to maintain this bond?"
] |
[
false
] |
Just wondering if there are any computational, theoretical, or experimental areas as far as this subject goes. I'm a applied math student who will be attending school for graduate level physics next semester, and I'm very interested in this subject. Very specific on the noble gas + metal, for example argon and gold or something of that nature. Maybe some sort of high vacuum and high energy process to create these bonds, if only temporarily. Thanks in advance for any answers!
|
[
"I've found you not only a compound with a noble gas metal bond (was expecting this), but I actually found your utterly insane suggestion of a direct nobel gas and gold bond. The ",
"Tetraxenonogold(II)",
" cation present in AuXe",
"(Sb",
"F",
" ",
") Florine makes for weird chemistry."
] |
[
"Bonding has been observed between noble gases and fluoride, but that has to do with fluoride being a ridiculously strong oxidant. Also, bonding between these species is rather weak and only really stable at temperatures around something like 5K. ",
"A metal with strong oxidizing power that comes to mind is the 3+ cation of gold, but I can't really envision a situation in which gold would form a salt with a noble gas, since they are so extremely unreactive.",
"For gold to be ionized, it has to be in a solution alongside a powerful oxidizing agent. Then, noble gas could be bubbled through, hopefully to be attacked by the gold cations. ",
"However, gold cations are pretty reactive and will therefore react with most of the oxidizable stuff in the solution, leaving the unreactive noble gas in place. Also, the low temperatures needed for stable bonding kinda hinder the formation of the gold cations.",
"Ok this is mostly just theorizing and thinking out loud, so if anyone could disprove me in any way, please do."
] |
[
"I have nothing to add except that the compound Xe[PtF_6] has been known to exist. Perhaps an expert could elaborate upon it."
] |
[
"How many virus cells are needed to make a human ill?"
] |
[
false
] | null |
[
"First viruses != cells, by definition. They are protein based capsids containing nucleic acids. Sometimes with a lipid envelope. But nothing more.",
"Second, it depends on the virus. There's actually a metric in microbiology called ID50, \"Infectious Dose 50\". It's similar to LD50. However, instead of lethality. it's the average number of pathogens needed to induce disease in 50% of a healthy population."
] |
[
"Not equal to."
] |
[
"What is '!='?"
] |
[
"What is the significance of RBMK nuclear cores not exploding?"
] |
[
false
] | null |
[
"The significance in the TV show is that they were denying something that had obviously happened. Reactor 4 was an RMBK and it did explode, but the higher-ups denied it and said that it’s not possible."
] |
[
"So it's a political statement rather than anything to do with science?"
] |
[
"I'm not sure what you mean by that."
] |
[
"Could self aware robots one day make it to other solar systems or galaxies and outlive humanity? And could self aware robots one day be considered living non-carbon based beings?"
] |
[
false
] | null |
[
"Such hypothetical / speculative / open-ended questions are better suited for our new-ish sister sub ",
"/r/asksciencediscussion",
". Please consider reposting there instead."
] |
[
"Is there a way for me to move it there without making a new post?"
] |
[
"Unfortunately no."
] |
[
"Why might UTIs (urinary tract infections) have a drastic affect on mental health? What is the link?"
] |
[
false
] |
[deleted]
|
[
"I must strongly disagree with most of the comments in this thread. Generally the idea that UTI can affect mentation and cause altered mental status comes from the geriatric literature, where infection is one of the many causes of AMS, delirium, or encephalopathy, three words which are synonyms and mean “disordered thinking, attention, cognition and level of consciousness.” The reason infection causes delirium is nuanced and incompletely understood but probably has to do with changes in inflammation and biochemical processes as well as pain, discomfort, fever, and other insults that cause enough distress that it affects the function of the brain in significant ways. People who are at risk for delirium are people who already have preexisting cognitive dysfunction (such as people with dementia, depression, or other psychoses).",
"All that said, in general UTI causes far far FAR less of the delirium than is attributed to it. Generally older patients come to this emergency department being altered and a urinalysis or culture shows evidence of bacteria, and the knee-jerk assumption is that it must be the cause of the delirium. This is erroneous because more than 50% of older adults are colonized with bacteria in their bladders, a condition called asymptomatic bacteriuria, which is not an infection and doesn’t cause delirium. This leads to over treatment with antibiotics and misdiagnosis of other causes of AMS that are potentially dangerous. Its basically an easy scapegoat for a really hard problem. When granddad is confused it’s real hard to say that this bacteria isn’t an infection (even though it usually isn’t). And even harder to say that we can’t figure out why he’s confused, and that it might last for a long time and might be his underlying disease getting worse."
] |
[
"This is the only response here even remotely close to correct, and it's spot on.",
"Other common causes of delirium which are often present alongside bacturia are dehydration, other infections, med interactions or improper dosing especially of chronic steroids, and lack of social or mental health support, among others. When grandma comes to the hospital from her budget brand assisted living facility, suddenly she gets IV hydration and a pharmacist to look over her meds and nurses to give the correct dose at the correct time and social work to talk with her and antibiotics to treat her UTI as well as any other infections she may have at the time. When delirium resolves who knows what fixed it."
] |
[
"UTIs can impair kidney and liver function and reduce their effectiveness in removing toxins from the blood which can build up in the brain. This can cause cognitive issues."
] |
[
"How can something like graphene aerogel be lighter than air if it's composed of matter and air? If it's already made of air and then extra matter is added into it to give it a solid body, how could it be even lighter than the preexisting air?"
] |
[
false
] | null |
[
"The term \"lighter-than-air\" when used in the context of solids means that the mass of the material that it consists occupies a volume such that the quotient (i.e. the density) is smaller than that of air. It does not account for air that would fill the cavities within.",
"If the aerogel is truly lighter-than-air - like if it consists of hollow cavities without air - then it'll be buoyant in air."
] |
[
"So what that term basically means is less dense than air?"
] |
[
"Specifically, it means that the ",
" is less dense than air."
] |
[
"Is there a viable way to shape sound waves?"
] |
[
false
] |
I only mean in the sense of sound not going past a certain point. The basis for this question started for me when I read . I remember reading the part where Ender was first introduced to the Giant's Game by another character. I can't remember the exact quote, but it was something along the lines of: Ender saw (xyz character) playing a different game on his computer. It was interesting because he had never seen it before. He could see the player talking to a giant, but he could not hear what the giant was saying because the sound was shaped towards (xyz character). My question in short, is this. Is there a viable way to shape sound waves so that only a small contained area can "hear" the sound?
|
[
"Yes. Sound is a wave, so with a correctly shaped reflector the sound can be focused on a narrow area. This type of setup often used in museum exhibits to limit the audible narration to a small area. Narrowly focused sound can also make a non-lethal weapon. See ",
"parabolic loudspeaker ",
" and ",
"LRAD",
"."
] |
[
"Also you can use ultrasound as carrier waves to focus sound like a laser."
] |
[
"There's a huge problem with that, there was a post here ",
"If two frequencies, one or both of which is by itself OUT of the audible range, have a beat frequency that is IN the audible range, might someone perceive the beat frequency?",
"Turns out that no, you can't easily. As in, if we assume the linear model of sound, then the wave with which you modulate the carrier (aka \"beat frequency\" in a simplified setting) doesn't actually carry any energy and therefore can't excite any resonators tuned to it (like the tiny hair-like things in our ears with which we perceive sound).",
"You can expect some of the energy to bleed into the audible range due to non-linearities, but it's very, very complicated if you want to do it purposefully.",
"By the way, ",
"relevant article",
" from xiph.org about it happening not purposefully (contains a lot of other interesting knowledge about psychoacoustics)."
] |
[
"Why do different substances have different specific heats?"
] |
[
false
] |
The amount of thermal energy in a substance is how much kinetic energy the molecules have, and the temperature is related to the average speed of the molecules (right?). So why is the relationship between the two so inconsistent? I imagine it's some mix of inter-molecular forces and different molecular masses, but I'd appreciate a more thorough explanation.
|
[
"Energy can be stored in translational, rotational, and vibrational modes inside a molecule. ",
"It can get even more complicated in solids."
] |
[
"Motion you can't predict",
" counts toward the temperature. The laws of thermodynamics are ",
"surprisingly agent-based",
"."
] |
[
"Why is water so good at holding heat? Is it because it does all three of these energy storage forms well?"
] |
[
"Are very active individuals who retire from their active lifestyles as they age at greater risk of obesity than their consistently inactive peers because they maintain the dietary habits needed to perform maintain their active lifestyle?"
] |
[
false
] | null |
[
"Unfortunately, there are so many variables at play here that it'd be impossible to deduce. There's a plethora of genetic and environmental variables. Being that we're speaking of those of retirement age there are even epigenetic variables, and the science of epigenetics is so young its still in the womb, so to speak.",
"Find a way to neutralize all those variables, and you basically have one question left: \"What has this previously active person decided to fill their time with?\". ",
"For myself, I'm highly active, but have periods of laziness as well. In those inactive weeks there's a lot of extra time on my hands. I'll find myself eating purely out of boredom, no hunger involved whatsoever. At a certain point my natural motivation compels me toward activity again. So, for myself, I eat LESS when I live an active lifestyle, but thats one person out of 7.1 billion..."
] |
[
"This is a great question. The fact that people can rapidly gain weight after ceasing exercise is pretty well known. The question is do they gain more than they would have if they hadn't exercised in the first place. I don't know the answer in people, but here is the answer in hamsters:",
"http://ajcn.nutrition.org/content/35/5/943.abstract?related-urls=yes&legid=ajcn;35/5/943",
"If you can't get the full PDF, the experiment was run out to 70 days. The most important experimental groups were sedentary controls and hamsters exercised for 35 days and then retired from exercise. The upshot is that the hamsters retired from exercise rapidly catch up to the sedentary hamsters in body weight, but at least over the course of the experiment, do not significantly surpass them. ",
"The explanation is that the retired hamsters have a delay in feeding and metabolic adaptation to decreased energy expenditure. In people, exercise seems to promote weight-loss maintenance by more closely matching food intake to energy expenditure. You can imagine that if someone with larger energy expenditure (higher lean body/muscle mass) stops exercising, then this mismatch might be proportionately larger, but that is just pure speculation."
] |
[
"Thanks for the reply.",
"The explanation is that the retired hamsters have a delay in feeding and metabolic adaptation to decreased energy expenditure. In people, exercise seems to promote weight-loss maintenance by more closely matching food intake to energy expenditure. You can imagine that if someone with larger energy expenditure (higher lean body/muscle mass) stops exercising, then this mismatch might be proportionately larger, but that is just pure speculation.",
"So you're saying the delay from when an organism reduces its energy expenditure to when its hunger reflects its calorific needs might be proportional to its weight? Why might that be? As a direct function of size or because metabolic rate generally scales inversely to size?"
] |
[
"Is there an easily achievable pressure, either + or - standard atmospheric pressure, that would significantly reduce the growth of most foodborne pathogens?"
] |
[
false
] |
My thoughts are for humble food storage containers. Of course, refrigeration increases the time before spoilage, and a perfect vacuum would have an effect. But is there any sweet spot above a perfect vacuum where all or most growth of pathogens gets slowed to a crawl? Or perhaps a higher pressure that's not in danger of exploding?
|
[
"I don't see how a perfect vacuum changes much. From my impression vacuum sealing prevents infectious agents from entering mostly from the \"sealing\" aspect. The vacuum part prevents ice crystals from forming on the surface and \"freezer burning\". But if you took some meat and had it exposed to some bacteria or something, then vacuum sealed it, it could still quite easily spoil (presuming the bacteria are anaerobic)."
] |
[
"I don't think so because of experiments like this ...",
"http://www.popsci.com/technology/article/2010-08/bacteria-survive-553-day-exposure-exterior-iss"
] |
[
"May be check out this google search ...",
"http://scholar.google.com/scholar?start=0&q=vacuum+packaged+bacterial+growth&hl=en&as_sdt=0,48&as_ylo=1992&as_vis=1"
] |
[
"Are we past the tipping point for the insect population decline?"
] |
[
false
] | null |
[
"Not likely. Insects as a group are exceptionally diverse and most reproduce quickly with large numbers of offspring. It will vary strongly from group to group, with heat-loving generalists doing well and specialists (e.g. obligate parasites with rare hosts) hurting the most.",
"Additionally, some are very susceptible to pollution, while others can survive nearly anywhere (e.g. mosquitoes in shallow, ephemeral pools)."
] |
[
"My background is in ant ecology, but I have had general entomology training. I can find some references for you in a few hours.",
"Edit for more compelling evidence:",
"a famous example of rapid evolution",
" though, variation must exist for selection to act upon, so small populations are at greater risk given that they are likely to have much lesser genetic diversity. ",
"Here",
" is an example of mutualism breaking down as the result of environmental change (herbivore exclusion). While this is specific, it highlights that mutualisms once thought to be tightly bound may be more or less plastic, resulting in further change in community assembly, which is probably one ",
"step in a series",
".",
"I believe a major hurdle, ",
"explained best in this article",
", is that we simply do not know the full extent of insect diversity. The key points are that the biggest factor affecting insects is shared by plants and vertebrates alike: ecosystem change. ",
"To return to the original question: are we past the tipping point? For insects as a group, they are super numerous and occupy a tremendous variety of niches. ",
" isn't going anywhere. Admittedly there is a cascade of declines are already in the works, ",
"similar to other vertebrate groups",
". ",
"tl;dr - Reliable estimates of insect extinction are very hard to quantify at this stage, but the biggest factors causing decline in insect abundance are largely the same as those for vertebrates and plants. The best way to preserve that which we don't understand is not to change it in the first place."
] |
[
"I believe ",
"this",
" is the article you are referring to. It has gotten a lot of publicity and is good for raising awareness.",
"However, ",
"this",
" article explains that the main patterns affecting insect ",
" (not ",
" diversity) and in the discussion explains why the long-term study above may not account for larger effects, such as an increase in temperature in a historically mild climate. They specifically designate a subsection of the discussion to comparisons between the two studies.",
"edited for clarification"
] |
[
"What would be the effects of a baby being conceived and being born on a larger or smaller planet?"
] |
[
false
] |
im curious how this would effect the biology of a human's growth.
|
[
"This article",
" reviews research on the effects of gravity on cell signaling in the immune system. The research suggests cell signaling is ",
", susceptible to gravity or absence thereof. Development relies heavily on cell signaling, I know for certain neural migration is majorly dependent on cell signaling to tell neurons where to go. If cell signaling is gravisensitive, development is gravisensitive. I doubt a fetus could assemble similarly as on earth. Couple of leaps of logic, hopefully they aren't too bad."
] |
[
"would a person born on mars be taller than somebody from earth then?"
] |
[
"Honesty im not positive, with the weaker gravity field pulling on them I figure they would grow taller but I would guess its more based in genetics "
] |
[
"Did the old english language contribute to modern french or did old french contribute to modern english?"
] |
[
false
] | null |
[
"There was probably some exchange both ways, but more the latter. England was conquered by Normans in 1066, and the class divide between French-speaking nobles and Anglo-Saxon peasantry shaped much of English's early development. For example, many terms for animals are germanic, coming from farmers, while many terms for their meat are french, coming from the nobility."
] |
[
"I'm a little late to the conversation, but wanted to reply anyways as you're quite wrong on this, and anyone reading later on might be confused. French is a Romance language, not a Germanic one. Is there a chance you are confusing \"Germanic\" with \"Indo-European\"? Slavic, Romance, Celtic, Hellenic etc. languages are (along with the Germanic family) all Indo-European. But there are some non-IE languages in Europe, such as Basque or the Uralic family. But most are not Germanic, and French certainly isn't. When linguists say that certain languages belong to the same family, they mean that they used to be the same language. French, Italian, Spanish, Romanian etc. are all Romance languages because they used to be Latin (which, along with other languages in the Italic family, used to be proto-Italic). If we rolled back the entire history of French, Italian, etc. speaking children learning their language from their parents and communities, we would eventually get to the point where they were all speaking Latin. French could never be a Germanic language because it didn't used to be Proto-Germanic. Using the term Germanic is perfectly fine here."
] |
[
"I'm a little late to the conversation, but wanted to reply anyways as you're quite wrong on this, and anyone reading later on might be confused. French is a Romance language, not a Germanic one. Is there a chance you are confusing \"Germanic\" with \"Indo-European\"? Slavic, Romance, Celtic, Hellenic etc. languages are (along with the Germanic family) all Indo-European. But there are some non-IE languages in Europe, such as Basque or the Uralic family. But most are not Germanic, and French certainly isn't. When linguists say that certain languages belong to the same family, they mean that they used to be the same language. French, Italian, Spanish, Romanian etc. are all Romance languages because they used to be Latin (which, along with other languages in the Italic family, used to be proto-Italic). If we rolled back the entire history of French, Italian, etc. speaking children learning their language from their parents and communities, we would eventually get to the point where they were all speaking Latin. French could never be a Germanic language because it didn't used to be Proto-Germanic. Using the term Germanic is perfectly fine here."
] |
[
"Evolutionary Biologists: What Is the Rationale for Having two Genders?"
] |
[
false
] |
[deleted]
|
[
"It's not certain, but having two sexes (gender includes mental state) allows for more variations in mutations in offspring. This allows us to keep up with more short-lived (and more mutation heavy) competitors like parasites. This is called the ",
"Red Queen Hypothesis"
] |
[
"To allow for sex. Sex facilitates genotype recombination, which is really valuable in organism with high investment in few progeny. ",
"http://en.wikipedia.org/wiki/R/K_selection_theory",
". In the absence of two genders, there would be frequent self-fertilization of the gametes (eg 'spegg' or 'overm'). If that happens it would defeat the advantage sex bestows.",
"Even ",
"yeast cells' JV-version of sex has a genetic mechanism for preventing self-fertilization",
"."
] |
[
"I'm Familiar with RQH, i'm afraid i phrased my question badly. What i was interested in knowing is What is the advantage of placing such a high physiological burden on one gender and not the other. I should Probably put that in the question."
] |
[
"Is it possible to quicken a planet's rotation?"
] |
[
false
] | null |
[
"Yes. As an example of what will happen, look at Phobos' eventual fate (",
"http://en.wikipedia.org/wiki/Phobos_(moon)",
" ). It will draw closer to Mars' surface and eventually hit it. Phobos might break up into a ring first, but that doesn't matter for our purposes. Either way, as Phobos' orbital altitude decreases, its orbital speed increases (the angular momentum of the Phobos-Mars system is conserved). When Phobos strikes Mars, the pieces will stop with respect to the Martian surface, and Mars rotation will have sped up to conserve the total angular momentum.",
"This process is basically the opposite of what happens to Earth and our Moon. As the Moon slowly moves farther away, the Earth's rotation slows."
] |
[
"Interesting. Is it possible to calculate the length of a day once the Moon has left the Earth-Moon system (or by the inverse square law has an insignificant influence)? How long would until this happens?"
] |
[
"Specifically, if a moon is in a lower orbit than the (geo)synchronous altitude for its planet, tidal perturbations will tend to lower its orbit and speed up the rotation of the planet. If it's in a higher orbit, the perturbations will raise its orbit and slow down the planet.",
"For the Earth this critical altitude is approx 36000 km. For Mars it is around 17000 km, which is why Phobos is spiraling in and Deimos is spiraling out."
] |
[
"Is Earth's centre of gravity at its geometric centre?"
] |
[
false
] |
Not entirely sure if this question makes sense. Thanks!
|
[
"Ok..i'm going to try to break this down as I go. Center of gravity from the point of what you looking for is actually the scientific term center of mass where all the accumulative mass from all outside forces = 0. If you wanted to measure this I would try to simplify a few things that I already know, the earth is not a perfect sphere (which I'm guessing is the backbone of this question), there are many discrepancies in the density of many objects included in the earth model here. How do you designate which accounts for more and where and more for less considering the non-perfect spherical shape? This is a pretty tough question (would you agree?). And that is not even considering the earth's different inner layers! ",
"The thing that really throws us off is that we have idea of what is in the earth's core, but what if you want to talk about precision center of mass, it will be damn near impossible to find it. ",
"Morale of the story, as you go deeper and deeper into science things can get so complicated it is overwhelming, and approximations do need to be made just to get a justificatory answer."
] |
[
"No.",
"The gravitational field of the Earth is very complex and depends on local and non-local differences in density. Because it's so complex it's very hard to define a \"centre of mass\".",
"We have detailed maps of the Earth's gravitational field, e.g. ",
"measured by the GRACE spacecraft",
" "
] |
[
"A large majority of the earth is solid, the only liquid portion that would make a significant contribution would be the outer core."
] |
[
"Why do we still drink milk?"
] |
[
false
] |
Are we the only species out there who still consumes milk way after we are done nursing? I don't want this question to come off silly, but there are many other better sources of vitamins, protein, and calcium. Also how much casein should we be consuming as adults, and why is drinking liquid out of an udder appealing to us?
|
[
"there are many other better sources of vitamins, protein, and calcium.",
"Uh, really? Name some.",
"Also how much casein should we be consuming as adults",
"Recent studies have correlated certain polymorphisms of casein in the cow population with lower rates of cardiovascular disease and diabetes, so as far as casein consumption goes, it's not really a problem. Studies in the past haven't conclusively shown that casein has any connection with negative effects on health."
] |
[
"Yeah, a lot of those foods are, individually, great sources for what they offer. The main appeal of milk is that it provides a lot of the nutrients and vitamins you need in one package. "
] |
[
"Yea convenience is real nice especially if it comes with a handle lol"
] |
[
"Is a black hole a physical thing such as a planet? What exactly is it?"
] |
[
false
] | null |
[
"This answer isn't quite accurate. Not trying to play the internet cop, but forum rules clearly say that you shouldn't speculate.",
"a black hole is a collection of mass so heavy it collapses everything around it, including light.",
"Mass is a property, so how can there be a a collection of it? Either you are talking about a collection of particles, which wouldn't be correct if we are talking about black holes in the common understanding, General Relativity that is, or you are simply using the wrong words to describe mass.",
"The earth creates gravity, pulling you towards it, the bigger the object the bigger the gravity, this is why the moon has less gravity then earth. ",
"This is just plain wrong, easily proven by the mere existance of white dwarfs and neutron stars. In fact, the more massive an object of degenerate matter is, the smaller it becomes. Also, mercury is smaller than the ice moons Ganymede and Titan, yet it is twice as massive. Surface gravitation is not just about mass, but also about density. That's why 2 objects with the same mass but different sizes have different gravitational pull. By the way, stellar black holes have lesser mass than their progenitor star. ",
"Imagine an object with so much mass that most matter collapses ",
"Not most, but all matter. And it isn't simply collapsing, it is literally disintegrated. There is no more matter after the infall into the singularity. ",
"with a gravity so powerfull that you'd be crushed into a tiny dot if you ever get to close, THAT is a black hole. ",
"No. Despite the fact that white dwarfs and neutron stars would crush me just as easily, this isn't a proper explanation of what a black hole is. ",
"The simple answer is, we don't really know what a black hole is, because we can't look inside. Therefore we don't get any evidence for or against any hypothesis what could be inside. We can only observe the effects outside of a black hole. Everything within the event horizon is completely hidden to us. ",
"Using our best theory on the topic, which is General Relativity, we conclude that there is a singularity in any black hole. The singularity is a quantum object and therefore literally has no size, or regarding the fact that nothing can be smaller than a planck length, it is just as small (note that distances smaller than a planck length have no physical relevance). ",
"So asking what it's made of is meaningless, because the singularity is all there is. Around the singularity may be infalling energy/matter however. In a black hole, time and space are changed. Within the event horizon, which isn't a real barrier or surface but simply the distance from the singularity where the escape velocity exceeds the speed of light, all spacial directions point inwards to the singularity, that's why nothing can escape. At the singularity then, space and time as we know them cease to exist. ",
"See ",
"this video",
" for more information. ",
"Keep in mind, that we still lack a proper quantum theory of gravity in the early 21st century. We don't know if singularities really exist or if there are quantum effects that stops the collapsing of matter at one point and stabilize the whole object somehow. We have to discover a theory of quantum gravitation first before we can finally tell what's really going on inside. Until then, General Relativity is our best friend to explain black holes."
] |
[
"Black holes certainly do have physical properties, but making sense of them mathematically push the boundaries of our normal understanding of those properties. For instance, in the simplest case, when calculating the surface area of a black hole, we find it to be proportional to its mass. Normally, mass and volume are proportional. Likewise, the concept of a \"singularity\" arises when considering the contents of a black hole. The singularity has zero volume yet contains all the mass of the black hole. Whether properties like these actually exist, or are simply a failure of our understanding of the universe remains an open question."
] |
[
"The earth creates gravity, pulling you towards it, the bigger the object the bigger the gravity, this is why the moon has less gravity then earth.",
"Isn't that not necessarily true? For example, white dwarfs?"
] |
[
"How is the total weight of the earth calculated?"
] |
[
false
] | null |
[
"We know that the acceleration due to gravity is equal to a constant (G) times the mass of the object (M) divided by the square of the distance to the object. We can measure the acceleration due to gravity either on the Earth's surface (9.8 m/s",
" ) or by looking at the moon (one rotation in ~29 days). This allows us to measure GM. Henry Cavendish in 1798 did an experiment using two giant lead spheres of known to create a small gravitational field and measure the constant G, which could then be used to calculate the weight of the Earth."
] |
[
"The word weight has multiple meanings. Only in science and engineering does it have the meaning specific to the earth's pull by gravity. Anywhere else it means the same thing as mass."
] |
[
"Just put a scale upside down and weigh the Earth! Of course this is the weight of the Earth in your gravity field. "
] |
[
"A (probably ridiculous) question about bees posed by my six year old"
] |
[
false
] |
I was reading The Magic School Bus book about bees tonight to 6 yr old, and got to a bit that showed when 'girl' bee-larvae get fed Royal Jelly, they become Queens, otherwise they simply become workers. 6 yr old the asked if boy bees are fed Royal Jelly, do they become Kings? I explained that it there was no such thing as a King bee, and it probably never happened that a 'boy' bee was fed Royal Jelly, but he insisted I 'ask the internet people', so here I am. Has anyone ever tested feeding a 'boy' larval bee Royal Jelly? If so what was the result?
|
[
"In honeybees, the males are haploid and have only 16 chromosomes. Their genome is entirely derived from the queen. Drones produce sperm cells that contain their entire genome, so the sperm are all genetically identical (except for mutations). The genetic makeup of the female bees is half from the mother and half from the father (male bee). Most female bees are worker bees, the ones that are to become queens are specially selected by the workers to become a Queen. ",
"While the Magic School Bus has simplified things for ease, in actuality all larvae in the colony are fed royal jelly, regardless of sex or caste. However, those chosen to become Queens are fed copious amounts of royal jelly which triggers the development of queen morphology, including the fully developed ovaries needed to lay eggs (mostly by changing the DNA methylation patterns in the future queens).",
"So, to get back to the question, if a male larvae was fed the royal jelly \"by accident\" -- not much would happen as it wouldn't make the male diploid. Now it may cause some methylation changes, which could interfere with behavioral responses of the male, but in general it wouldn't make him a king."
] |
[
"What is the mechanism by which larvae are chosen to become Queens?"
] |
[
"No. DNA methylation is an epigenetic modification that doesn't alter the coding sequence. Instead, it adds \"markers\" to the backbone that can affect gene expression. In some cases, methylation patterns can be passed on to offspring, but methylation can be added and removed without affecting the underlying genetic code."
] |
[
"why do different pigments have different absorption spectra?"
] |
[
false
] |
why does the photopigment in blue cones, for instance, absorb light wavelengths that are mostly 430nm, while photopigment in red cones absorbs lights that's mostly 570nm? the difference in absorption spectra of chlorophyll molecules is due to variations in hydrocarbon tail length and side chain type. is there a method to the madness, though? like some kind of simple pattern that i can wrap my mind around, like more side chains = long wavelength absorption? or does the spacing of molecular components directly correspond to the wavelength? what's going on here? (i'm not looking for an explanation of the whole phototransduction cascade)
|
[
"Absorption relations fundamentally come from the interactions between electromagnetic waves and molecules; you can compute, using elementary quantum mechanics and advanced classical electrodynamics, the ways light should interact with a particular molecule, but there is no easy \"trick\" or correlation, mainly because of long chains and dynamic chemical structures.",
"For example, these chains can behave as scattering antennas sometimes, and more complex molecules featuring many elements are also problematic; ",
"gold, for example, has its yellow color due to relativistic effects",
", so if you don't account for relativistic quantum mechanics in the computation of the bonds in a molecule containing gold, you might get wrong results.",
"In the case of hydrogen, the computation is ",
"straightforward",
" and requires no hassle; then, in more complex cases, like in an Ammonia molecule, ",
"utilizing intermediate quantum mechanics",
" and some calculators, you can compute the energy spectrum and thus the light emission. In the example of a chlorophyll molecule, things get tricky: we can't calculate things exactly, but utilizing approximate mathematical methods and ",
"DFT",
" you can ",
"calculate the energy spectrum of the molecules",
" to a high degree of accuracy."
] |
[
"Basically the absorption of light is due to energy transitions in the molecule. Visible light tends to be electron transitions (an electron moving from a lower energy orbital to a higher energy orbital). ",
"Putting it simply, electrons like to be spread out over larger volumes, and a molecule that can do this by pi-bond conjugation lowers the energy (and energy difference to the next unoccupied orbital) of the orbitals the electrons occupy. In reality, for organic molecules ",
"such as those in your eyes",
", this is achieved in larger ",
"conjugated systems",
", meaning that a larger conjugated system tends to absorb longer wavelengths.",
"See ",
"here",
" and ",
"here",
" for more information."
] |
[
"I wanted to add to your question: Despite \"different color\" cones using the same molecule for photon absorption, the proteins that envelope the molecule are different for red and blue cones, and interact differently enough with the molecule to change its absorption wavelength."
] |
[
"Is rain totally pure, clean water?"
] |
[
false
] |
I have heard that it is 100% pure H20 due to the evaporation process, but somebody else told me that rain molecules form around dirt/dust particle during condensation. Plus acid rain makes it more confusing
|
[
"rain water is not pure H20. Pure H20 is not typically found in nature, only in analytic chemical laboratories and some factories. Carbon Dioxide from the atmosphere is absorbed by water molecules and and turns into carbonic acid, which is found in all rainwater. It is slightly acidic, but typically not harmful to most creatures/plants on Earth. Other chemicals can make a stronger acid in rainwater and thus be harmful. ",
"rain water is indeed fresh water, like that you'd find in most lakes and rivers. fresh water is defined having a salt concentration of less that 0.05%, where as salt water (such as the ocean) has a salt concentration between %3-5. And by salt, I mean the chemical definition, not sodium chloride."
] |
[
"Rain is not pure, clean water. Yes, water molecules need a nucleation point to condense into a water droplet (it's something I remember from a Bill Nye episode back when I was younger). This dust particle or impurity is usually known as a ",
"Cloud Condensation Nuclei",
". ",
"The thing I want to point out is that evaporation and precipitation are two different phenomena. Yes, you can get really pure water through evaporation, but upon condensation under natural conditions precipitation will contain some impurities."
] |
[
"As the water evaporates it is pure water. When the water vapor returns back as rain it has picked up impurities of the air it has moved through. \nYes the impurities can act as a seed crystal which water vapor would adhere too",
"Acid rain is when some gasses mix with the water to combine a difference compound. For instance if you mix chlorine gas and water you would get hydrochloric acid and oxygen",
"Also when they refer to acid rain they do not mean the entire amount of rain falling does is an acid"
] |
[
"Does pouring boiling hot water on a toothbrush sterilize it?"
] |
[
false
] | null |
[
"At standard pressure, boiling water won't kill everything. And you'd have to keep your tooth brush in the boiling water for about 20 minutes or so to mostly sterilize it. The instant you bring it out of the boiling water though, technically it wouldn't even be mostly sterile any more, as what floats in the air would start to colonize it, plus whatever you're using to hold it with would also serve as a source of recolonization."
] |
[
"However this would likely lead to a melted toothbrush as most are made from Polypropylene with a melting point of 130–171 °C. "
] |
[
"It might kill a few things, but if you ",
" want to sterilize something, you'd need an autoclave, which uses hot pressurized steam to disinfect surfaces. Twenty minutes in an autoclave at 120-170 C and there will be practically nothing left alive."
] |
[
"If the extinction event of the dinosaurs never happened, how long would they have likely survived?"
] |
[
false
] | null |
[
"Dinosaurs are still living today, so to speak.",
"It was quite a shock at first (this scientific discovery happened within the past couple decades I believe), but ",
"birds are descendants of dinosaurs",
".",
"Check out the ",
"wikipedia page",
" if you'd like to read more.",
"Edit: And I realize this doesn't answer the spirit of the question, which is likely \"How long would the now extinct lines of dinosaurs lasted\", to which I personally can't give a good answer without a lot of conjecture. Hopefully someone else can for that part :)"
] |
[
"The discovery, or at least initial idea, that modern birds are descendants of dinosaurs is actually pretty old, going back to the late 19th Century. ",
"Archaeopteryx",
" was discovered in 1861 and showed a mix of bird and theropod dinosaur traits that got the ball rolling for many scientists. Thomas Henry Huxley argued that birds evolved from dinosaurs by comparing birds, Archaeopteryx specimens, and compsagnathids as early as 1868. It was even reasonably accepted until it fell out of favor in the 1920's when people argued that birds have fused clavicles and no dinosaurs they had found did, so similarities must have been convergent evolution (turns out some dinosaurs do and they had misidentified them). The theory was revived in the 1970's by ",
"John Ostrom",
" and just about every shred of evidence since then has affirmed it. ",
"I feel I should mention many paleontologists would say birds aren't just descendants of dinosaurs, but are dinosaurs by any sense of the word. Most of the diagnostic traits for ",
"Dinosauria",
" are still very much present in birds, and many \"bird\" traits including vaned feathers are found on dinosaurs that are not included in Aves."
] |
[
"For one thing, the way dinosaurs are depicted by artists has changed quite a bit as we study them more, so many pictures you may have grown up with could have been based on incorrect interpretations. T. rex ",
"used",
" to be a scaly, upright-walking dinosaur dragging his tail. ",
"Now",
" we know a bit more about how they carried themselves, and feathers may go that far back (or even farther) up the dinosaur family tree. T. rex may have had some feathers. ",
"Old",
" vs ",
"new",
" Iguanodon is another great example. ",
"There's also a fairly healthy debate as to whether dinosaurs were or were not warm blooded, with some arguments for both sides, and I don't have the expertise to say one way or the other. But even ",
"being warm blooded or cold blooded",
" isn't a cut and dry issue, and its almost certain they were metabolically active and not lazily lumbering around the landscape.",
"Aside from that, it really depends on what you define as \"reptilian\". We already know plenty of dinosaurs had feathers, so its not just scales. And birds still have ",
"scaly",
" feet anyway. Sprawling like a lizard? ",
"Crocodylians can walk upright",
" as did all dinosaurs, including the bipedal ones like birds. Sharp reptilian teeth? Turtles have no teeth, many extinct reptiles were herbivores with different types of teeth, and until fairly recently in the evolution of birds they ",
"still had teeth",
". It may just be weird to think about when you've been separating them your whole life, but its an incredibly widely supported conclusion, and if you've got any other questions about it feel free to ask."
] |
[
"What is actually an electromagnetic field?"
] |
[
false
] |
We know what a gravitational field is: the curvature of space-time. However whenever I look for information of electromagnetic fields, the conclusion I get is that a charged particle can make other particles to move without touching them. I know that the answer for this is "the particles do touch each other because their magnetic fields touch" however, this always seemed to me an explanation as magical as the "invisible force working at distance" that Newton described to explain how gravity works. Einstein in the other hand, explained that there is not a force working at distance, but that gravitational fields are nothing but the curvature of space-time. Is there an explanation like this for electromagnetic fields? I mean, do we know what is actually happening to the space between the particles interacting through their electromagnetic fields?
|
[
"The explanation is really not that different from gravity. The electromagnetic field is a \"thing\" that exists everywhere, charge objects can \"deform\" it, and charged objects are in term accelerated when in the presence of a deformed field. We are perhaps more familiar with \"spacetime\" as a thing that exists rather than \"the electromagnetic field\" which is nevertheless also a thing that exists everywhere. "
] |
[
"I don't think that's quite correct. Gravity is special because every particle feels the same effect in the same gravitational field, that's ",
" it's possible to have a picture of gravity in terms of curvature of spacetime. Although I think there are more geometric treatments of gauge theories (involving things called fiber bundles that I know very little about), I don't think the analogy goes as far as you'd like it, because particles with different charges will move differently in the same electromagnetic field."
] |
[
"every gauge theory has a geometrical formulation. The difference between something like QED and gravity is that in the one case the geometry is linked to an internal space and the other case the geometrical space is spacetime itself.",
"I think maldacena talked about this in one of his public lectures on a level most people can understabd"
] |
[
"Two humans are pushed off a building, one with enough helium filled balloons attached to him to make him weigh 1 kilogram, what is the difference between the force of impact on both people?"
] |
[
false
] |
Assuming that the difference between air resistance of the people falling is negligible. Would they both die? Also assuming that this is decently sized building that would kill the other human.
|
[
"Let's disregard air resistance and disregard the change of the buoyant force with height. So we basically have Dude A being pulled down by the Earth; and Dude B being pulled down by the Earth ",
" by a rope with a constant force. ",
"They're each 100kg, g=10m/s2. The force of the rope is 990N upward. This means that he would feel 10N acting up on his feet by the ground when he stands.",
"If you draw a free body diagram for Dude B, the forces of his weight (100kg * 10m/s2 = 1000N down) and the rope (990N up) counteract each other, leaving his 100kg mass experiencing a 10N force downward.",
"Using F = m * a, his acceleration toward the earth is 0.1m/s2 (as opposed to unlucky Dude A, whose acceleration is a hundred times that).",
"Over 100 meters, Dude A will be going almost 45m/s, whereas Dude B will be going a tenth of that (since he experiences 1/100 the force and acceleration). To put that in perspective, that's how fast you hit the ground after falling a fifth of a meter (jeez that sounds wrong but I've done the math a couple times...)"
] |
[
"Wouldn't they fall the same speed if there''s no air resistance? Like the feather and brick thing?"
] |
[
"Dude B is slowed down by the buoyant force, not air resistance. I almost made that mistake as well."
] |
[
"What makes Chernobyl so much more lasting in radioactive impact than Hiroshima and Nagasaki?"
] |
[
false
] |
(*Hiroshima, Nagasaki or any other detonation location). Is it mostly about volume of material? Or are reactors that much more powerful than bombs in terms of thermal output?
|
[
"Mass of material, delivery mechanism, it's basically apples and oranges. ",
"A nuclear detonation annihilates fissile material to produce a massive emission of energy in a short period of time. A nuclear reactor produces electricity from fissile material generating steam when connected to a thermal exchange system of some kind (involving water), relying on the extremely slow decay of the material rather than forcing it to reach supercriticality and annihilate. ",
"Little Boy, the bomb dropped on Hiroshima, contained 140 lbs of Uranium. Only the most minute traces of which survived the detonation.",
"Fat Man, the bomb dropped on Nagasaki, contained only 14 lbs of Plutonium. Same as above, it was by and large annihilated.",
"The reactor that exploded in Chernobyl contained 140 ",
" of nuclear fuel, and a good portion of this was scattered in the explosion, carried on the winds, introduced into the water, etc, and there's still a large quantity of material left at ground zero. ",
"More information can be found ",
"here."
] |
[
"The nuclear devices dropped on Japan used kilograms of nuclear material most of which was used up in the blast itself. What remained was spread over a large area very quickly.",
"The first atomic weapons were remarkably inefficient. It's estimated that only about 1% of the uranium used in the Hiroshima bomb fissioned, and the rest just blew apart. Over Nagasaki about 16% of the plutonium fissioned, and the rest just blew apart. In both cases the majority of the fissionable material just blew apart.",
"However, that fissionable material just isn't that particularly harmful in small quantities. The Hiroshima bomb only had about 140 pounds of uranium in it, and the Nagasaki bomb had about 14 pounds of plutonium. ",
"Neither unfissioned uranium or plutonium are dangerously radioactive. Both are measurably radioactive, but you can pick them up and hold them in your hands just fine with no ill effects. In fact, both materials are far more dangerous from chemical toxicity than as a radiation hazard. ",
"Both are extremely dense as well, so in actuality the total volume of material was much smaller than you'd think. The 140 pounds of uranium used over Hiroshima is roughly the same volume as a 1 gallon milk jug. The 14 pounds of plutonium used over Nagasaki is about the size of a baseball. These metals are so dense that you can't pick up much of them to start with.",
"On the other hand, the stuff that escaped the Chernobyl reactor was extremely radioactive. Spent fuel has been \"activated\" and is far more radioactive than unused fuel or unfissioned nuclear weapon fuel."
] |
[
"The nuclear devices dropped on Japan used kilograms of nuclear material most of which was used up in the blast itself. What remained was spread over a large area very quickly.",
"The first atomic weapons were remarkably inefficient. It's estimated that only about 1% of the uranium used in the Hiroshima bomb fissioned, and the rest just blew apart. Over Nagasaki about 16% of the plutonium fissioned, and the rest just blew apart. In both cases the majority of the fissionable material just blew apart.",
"However, that fissionable material just isn't that particularly harmful in small quantities. The Hiroshima bomb only had about 140 pounds of uranium in it, and the Nagasaki bomb had about 14 pounds of plutonium. ",
"Neither unfissioned uranium or plutonium are dangerously radioactive. Both are measurably radioactive, but you can pick them up and hold them in your hands just fine with no ill effects. In fact, both materials are far more dangerous from chemical toxicity than as a radiation hazard. ",
"Both are extremely dense as well, so in actuality the total volume of material was much smaller than you'd think. The 140 pounds of uranium used over Hiroshima is roughly the same volume as a 1 gallon milk jug. The 14 pounds of plutonium used over Nagasaki is about the size of a baseball. These metals are so dense that you can't pick up much of them to start with.",
"On the other hand, the stuff that escaped the Chernobyl reactor was extremely radioactive. Spent fuel has been \"activated\" and is far more radioactive than unused fuel or unfissioned nuclear weapon fuel."
] |
[
"My teacher says all molecules that have benzine rings are bad for you. Am I right in saying this is false? If so, help me support my argument with her."
] |
[
false
] |
[deleted]
|
[
"If you need some specific examples:",
"Phenylalanine - An essential amino acid",
"Tryptophan - An essential amino acid",
"Tyrosine - An amino acid",
"Not only are they ",
" bad for you, they are essential to life."
] |
[
"The phenyl ring (benzene ring) features in many pharmecutics, including aspirin and paracetomol. Further more, the compounds that make up our dna base pairs also have benzene rings! Benzene itself is toxic due to, in part, the metabolites, including (i understand) epoxides. It is an electron-rich compound, meaning it will be more activated to chemical reactions. However, certain chemical modifications to benzene (e.g. The attachment of an acyl group, C(O)CH3) can lower the suseptibility to reactions as well as opening up other metabolic pathways to compounds which are not so toxic and easily excreted.",
"I'm aware of the controversy surrounding bisphenol-A, but I'm not well versed in the details of eithere side of that argument. However, you may like to point out that it features hydroxyl groups and methyl groups as well as benzene rings; are compounds featuring these also toxic(!)? "
] |
[
"If you like; you may like to reference the structures of aspirin and paracetomol (and any others!) from a book or some scientific papers. Do a google search for molecule of the month, i think its an oxford uni website, thats a good source of interesting, benzene containing compounds that are important pharmecutics. Good luck with your report!"
] |
[
"Why do you see a sort of “motion blur” in real life?"
] |
[
false
] |
Sounds kinda stupid but I couldn’t find an answer on google as “motion blur” will always turn up something about photography. Basically, what I’m curious about is the phenomenon when there’s a dim source of light in a dark setting (like using a phone in a dark room), any fast movement always translates to a weird trail of light behind the source. Is the light being momentarily burnt into your retina or is something else happening?
|
[
"That is in fact correct! The more technical term is persistence of vision, and it is caused by the photosensitive receptors in your eyes not reacting quickly enough.",
"It's also how most dimmable lights work, instead of lowering voltage and reducing efficiency, one can flicker the lights thousands of times a second to produce a dimmer light that we perceive as continuous. It's called PWM."
] |
[
"Your eyes receive light just fine (we can see strobes after all), but it takes a little time and some replacement chemicals for your retina to ",
" telling your brain there were photons."
] |
[
"PWM always has the side effects of pulsating output, albeit not significant in some cases. In other cases like LED lighting where there's no momentum (i.e. the lights can turn on and off really quickly unlike incandescents) then you will see flickering"
] |
[
"How does the momentum of a parent particle affect its decay products?"
] |
[
false
] |
My understanding of this field is very limited, but I'm looking for an answer for the following thought experiment: A hypothetical unstable particle is accelerated into empty space where it will not interact with anything. Within its own timeframe, it is bound to decay into less energetic and more stable particles within a fraction of a second. But since it is accelerated to near c, we'll assume that it will take it one second in the observer's timeframe to decay. After one second in the observer's timeframe, the parent particle decays into two daughter particles. Do those two new particles keep traveling in the same "direction" as the parent particle did, or will the event of decaying cause them to change their trajectory?
|
[
"In the rest frame of the particle, the daughter products will have some moment that adds up to zero. If that rest frame is moving very fast relative to some other frame, in that other frame the daughter products will have momenta such that the center of mass is still moving really fast in the same direction."
] |
[
"The net momentum of the particles will be zero, as long as the fission also emits gamma rays carrying the extra humph. From a spectators standpoint, both particles would move in such a way that the center of mass is travelling in the same direction as the \"mother\" particle.",
"I'm only commenting to stress the importance of the gamma rays carrying momentum so that the sum cancels."
] |
[
"Why would you need gamma rays for that? If a particle decays into two daughter particles, they just go back-to-back in the rest frame of the parent."
] |
[
"Why can electomagnetic waves travel in void, while acoustic waves can't?"
] |
[
false
] | null |
[
"Acoustic waves are oscillations in some sort of material medium like air or water. Without the material medium to oscillate, there can be no sound. Electromagnetic waves are oscillating electric and magnetic fields, so EM waves can travel through any region of space that contains these fields. The nice thing about electromagnetism is that an oscillating electric field creates an oscillating magnetic field and vise versa. Thus, any oscillation in an EM field can propagate through virtually any region of space."
] |
[
"But if EM waves can travel through any region of space that contains EM field, can it travel through a perfect void?"
] |
[
"If there is a perfect void, the EM wave will travel through it because it will create its own oscillating electric and magnetic fields in the void. ",
"Maybe try thinking of a situation in which you are trying to cross a deep ravine. If there is a bridge already built across the ravine, then you just have to walk to the other side. If there is no bridge, then you can't cross the ravine. This is analogous to the mechanical waves that require a medium like sound. Sound waves require a bridge (the air, in this case) to travel from one point to the next. If there is no bridge (no air) then the sound cannot propagate.",
"Now, lets imagine that there is no bridge across the ravine. We, however, are able to devise some ingenious scheme to create our own bridge as we cross the ravine. In doing so, we are able to cross the ravine...propagate through the void in other words. Unlike sound, light creates its own medium to travel, thus, light can propagate through the void whereas sound cannot. Light creates its own bridge between two points, whereas sound requires a bridge to already be in place. ",
"Hope that helps. Let me know if you are still confused."
] |
[
"When calculating thermal expansion, do you multiply the thermal expansion of oxides by their mass percentage or molar mass percentage in a glaze?"
] |
[
false
] |
I’m a ceramicist and I’m making a calculator for glaze analysis. I want my calculator to output the co-efficient of thermal expansion of the fired glaze as calculated by the expansion of the various oxides that make up the glaze, but I don’t know (and haven’t been able to find out) if I should be calculating from the mass or molar mass percentage of the oxides. Let me know if I didn’t explain anything well enough!
|
[
"Ok, I'm out of my tree here, so far that the squirrels are sending out search parties. But as a general note, the coefficient of expansion is 1/V dV/dT. So for a first order approximation, you want the relative volumes, not the masses. So, I'd go by the absolute mass for every oxide in the mixture divided by its density, normalize to the total mass of the mixture and use that as a weighing factor for the respective coefficient of expansion."
] |
[
"Not exactly sure what you are aiming at. Do you want to derive the coefficient of expansion for a mixed oxide from the coefficients of the individual oxides in the mixture? I'm not a solid state guy, but that doesn't seem quite straightforward to me, since you'd have to take the interactions between the individual components in the lattice into account."
] |
[
"That sounds like what I’m going for and yes it’s not totally straightforward or completely accurate, but it’s the common way of doing things and it gives a workable ballpark figure. ",
"I’ll try and give some more background. Mix raw materials together to make glaze, pour glaze on pottery, fire to 2,360.F, carbon and other stuff burns off leaving you with oxides (theoretically), glaze melts into glass, clay sinters. ",
"Then everything cools. If the thermal expansion of the resulting glass is higher than that of the clay, the glass will stretch over the clay and eventually crack, that’s where the crackle pattern on so many ceramics comes from. If you want to avoid this you try to match the thermal expansion of the glass and clay. ",
"So, you look at the theoretic makeup of all your raw materials (this is usually provided as a mass percentage list of oxides and then what is lost on ignition), figure out the theoretic oxide makeup of your resulting fired glaze, and calculate the molar mass percentage of all the oxides. From that oxide breakdown (either mass or molar mass percent, not sure which) you calculate thermal expansion. ",
"You’re right that it doesn’t factor in a lot of things: interaction between oxides, unmelted things that weren’t properly diffused into the glass, crystal growth, etc. It does give you a workable, ballpark figure though that at least lets you sort out if changing the recipe in such-and-such a way would increase or decrease the thermal expansion and by about how much (a lot of a little)."
] |
[
"Why are astronomers obsessed with finding water on extrasolar planets?"
] |
[
false
] |
[deleted]
|
[
"If you want to buy food, do you go to the grocery store, or do you just wander into the nearest retail outlet? Sure, there ",
" be food in the clothing store, or the furniture outlet, or the hardware store. But since you ",
" the grocery store can have food, and lots of it, you head straight for that. Looking for life in places with water is the same idea.",
"Also, neither hexane nor mercury is polar, which means it wouldn't dissolve as great a variety of things as water. Also liquid mercury is bound to be incredibly rare in the universe."
] |
[
"Well, life is built out of super-complex chemistry. Most of the complex chemistry we know about needs water to work. Any sort of chemistry based life needs some sort of solvent, just because otherwise chemicals can't float around and bump into each other. There's also a question of prevalence. Liquid water is all over the place. Liquid hexane or mercury would be a heck of a lot harder to find than liquid water. I guess liquid hydrogen is pretty common deep down in gas giants, but it's so hot there complex molecules can't even stick together. And there is a little liquid methane and ethane out on Titan, but that's one of the only places in the solar system that has it. It's also super cold out there. Not impossible for life (in fact, I think it's the best chance for non-water life), but things would certainly live a lot slower. So not only do we not have examples of life in waterless environments, we don't have examples of much in the way of possible building blocks in waterless environments either. I wouldn't want to say it's impossible without water, but again...we ",
" it can happen in water, so we look for water. We don't look for water because we think there is absolutely no chance life could exist without water, we look for water because we know 100% that life ",
" happen with water."
] |
[
"Ah. This makes sense. However, is there nothing that precludes the possibility of life existing outside an aqueous medium?"
] |
[
"'Permanent' Storms. Would it be possible for them to persist on Earth?"
] |
[
false
] |
[deleted]
|
[
"Doe the ",
"Catacumbo lightning",
" count?"
] |
[
"Best I've got on Earth is 31 days for Hurricane John in '94. ",
"I couldn't tell you if longer were possible from a technical perspective. "
] |
[
"nearly, i'm wondering more about a giant weather system than a smaller local phenomenon.. still this is really interesting thanks for the link."
] |
[
"A weird question: could a giant pitcher plant dissolve humans?"
] |
[
false
] |
Presume that there is one of those carnivorous pitcher plants, but it was scaled up. Ignoring issues of base fragility and other scaling problems, suppose a human being were trapped in there. Would the fluids inside be able to dissolve them, or would it not be able to decompose our skin like it does insects?
|
[
"Assuming that the person was incapable of moving, and the plant was scaled up enough that it could a) contain a person b) drown said person (which is how it kills its prey) c) secrete enough enzymes to dissolve the person, yes it could eat a human. It has been known to ",
"eat small rats, mice, lizards and even birds",
" at its present size. I don't see any reason our skin would be impervious to decay when those animals are not. ",
"So, all you need to do is find a way to get a 5-10m pitcher plant and you can dispose of bodies. "
] |
[
"Does the animal/human need to be dead and rotting before it will digest them?",
"No, the enzymes are working from the start. However, if the animal isn't dead it will continue to thrash about which could severely damage the plant. IF someone was trapped inside and was still living but could not get out, and didn't drown it would be a terrible, terrible death, being eaten from the outside in. It'd probably take a week (or more) until the person had decomposed enough to stop living. This of course assumes that the person can still breathe (and, I guess get enough fluids so they don't dehydrate...) "
] |
[
"Good question. Reading ",
"this nice historic overview",
", it seems there's still quite a bit we don't know about how ",
" digests its victims. It's apparently known that it secretes an acid protease, i.e. a protein-digesting enzyme that only works in very acidic conditions. So it clearly does some digesting and absorbing on its own.",
"The question here seems to be whether it does the digestion with the acid+protease alone, or whether there are symbiotic bacteria present to aid the process. If it's acidic enough, I suppose that'd kill you eventually. But if not, and it requires bacteria, then I guess our immune system may stop them."
] |
[
"What's the most accepted hypothesis (or theory) for the cause (not pathology) of autoimmune diseases?"
] |
[
false
] | null |
[
"As many people have mentioned, there is no one 'most accepted' hypothesis (or factor, let's say) that is thought to be the primary ccause of autoimmune diseases. However, people haven't given a lot of details on some of the current popular hypotheses, including ones that relate to things you've brought up in comments, like sex. So starting there:",
"As per ",
"this paper by Quintero et al",
" -- ",
"Almost 5% of the world population develops an AD. Of this 5% approximately 78% are women ",
"[1]",
" and it is considered the fourth leading cause of disability for them ",
"[2]",
". Women are at 2.7 times greater risk of acquiring an AD than men ",
"[3]",
". ",
"Also",
"Generally, women have a stronger humoral and ",
"cellular immune response",
" compared to men. They show a higher ",
"CD4:CD8 ratio",
" because of a higher absolute ",
"CD4 cell count",
" and a higher level of circulating antibodies ",
"[9]",
". Compared to men, they have more rapid rejection of ",
"allograft",
" and reduced incidence and regression of tumors ",
"[10]",
". ",
"Which brings them to summarize a number of potential explanatory factors:",
"prolactin",
"stimulants",
"X chromosome",
"thymus",
"X monosomy",
"T cells",
"XXY",
"immune repertoire",
"Microchimerism",
"pathogenesis",
"Y chromosome",
"Aside from sex-based differences, there are also genetic and environmental factors that cause autoimmunity. From ",
"Cusick et al",
":",
"Although host genetic background contributes to the induction of an immune response to self, epidemiological and molecular evidence implicates infectious agents (viral and bacterial) as the principal environmental insults responsible for the induction of autoimmune diseases (reviewed in [",
"4",
", ",
"5",
", ",
"6",
"]). Prolonged proinflammatory responses to infections have been associated with the initiation and exacerbation of autoimmune diseases (reviewed in [",
"4",
", ",
"7",
", ",
"8",
"]). Inflammation is facilitated by proinflammatory cytokines such as type I interferon (IFN), interleukin (IL)-1β, IL-12, IFN-γ, IL-17, and tumor necrosis factor (TNF)-α (reviewed in [",
"7",
", ",
"9",
", ",
"10",
"]). However, these proinflammatory cytokines are critical for clearance of pathogens, suggesting that environmental factors are able to divert the immune response towards immunopathogenesis. Although a number of immune cells are responsible for secreting proinflammatory cytokines, the primary cell types implicated in a vast majority of autoimmune disorders are autoreactive B and T cells, or antibody recognition of self [",
"11",
"]. ",
"While B cells and T cells are specifically called out in that quote, others have pointed toward ",
"dendritic cells as a central hub",
" between regular inflammatory responses, tolerance, and autoimmunity."
] |
[
"Thank you! Very informative."
] |
[
"Yes of course anything can be spontaneous, but there's an epidemiology to think about, we see those diseases more in women, more in 1st world countries, more if there's a family history... etc.",
"So there must be some factors that are much more important than chance."
] |
[
"Why are our brains so high up in our bodies?"
] |
[
false
] |
Since blood is heavily influenced by gravity, and the brain requires a lot of oxygen to function properly, why do we have our brains in the highest part of our body, as it takes a lot of energy for great amounts of blood to be pumped all the way up there?
|
[
"This is due to the evolutionary trend in early chordates (more specifically the ",
"craniates",
") for ",
"cephalization.",
" Sensory organs and nerve bundles gravitated towards one end of the body to eventually form the head with the brain, eyes and nose in the same general region. This general blueprint was passed down through all craniate descendants. This is most easily illustrated when looking at different ",
"embryos.",
" "
] |
[
"It is possible to expand on this a bit. sensory organs tend to cluster around mouth-like orifices. Which makes some sense as organisms want to be able to find food and then put it in their mouths. This sets up an early axis of asymmetry where one end tends to have both sensory organs and mouths.",
"When adding more sensory organs there are then two things going on. The first being the aforementioned proximity to the mouth and the second being how expensive (in evolutionary terms) it is to wire up something new. Its cheaper to \"bud off\" (or connect to) any preexisting brain-like structure than to establish a new site for sensory organs. So once a head is established it becomes a privileged site for new sensory organs. "
] |
[
"To build off this even further...for the reasons you both mention, the brain starts off in the \"head\" region of vertebrates. These were fishlike creatures, so OP's blood-pressure issue wasn't an issue...the head was at the front, it was no higher than any other part of the body. This horizontal body plan continued on down toward the eons until you get right up to hominids which stand ",
" and put the head high up. This is the first time in the whole lineage that blood pressure of a head much higher than other parts of the body really becomes an issue.",
"At this point, it's not really possible to go and rearrange the entire vertebrate bodyplan just to avoid this problem. Just imagine the scale of mutation that would have to happen for something like a chimp or H erectus to mutate in order to have it's brains in its belly. That sort of thing just doesn't happen. ",
"So early on, when adaptation might have been possible, there was no impetus to avoid having the brain placed high on the body because the brain ",
" placed high on the body. By the time the brain wound up placed high, it was too late to change. "
] |
[
"Why do astronomers think themselves immune to the uncertainty principle?"
] |
[
false
] | null |
[
"Astronomers aren't \"immune\", really, any more than baseball pitchers are. First let's get straight what the uncertainty principle actually is. There are many uncertainty principles, but the one you are referencing is the classic ∆x∆p ≥ ℏ/2, where ∆x is uncertainty in the position, ∆p is the uncertainty in the momentum, and ℏ is Planck's constant divided by 2π. This says, very simply, that the product of the uncertainty in the position and the uncertainty in the momentum must always meet or exceed this minimal value. This is true for all particles/waves, not just light. It's true for electrons and protons, gluons, neutrinos, whatever. ",
"The thing is, ℏ/2 is very, very, ",
" small on everyday scales, much less intergalactic ones. It's about 5x10",
" m",
" kg / s. Just treating a baseball as a single particle to get a feel for the size of the effect, go ahead and calculate the minimal positional uncertainty for a fastball with a speed known to 15 decimal places. It's much, much less than the size of an atom. ",
"Our uncertainty in the distances of other galaxies is generally ≥10%. It doesn't matter what precision in the velocity you are after, the uncertainty principle places a limit far, far below the practical limits. Other quantum effects in the detector become important before the uncertainty principle does. It simply isn't important when discussing distance vs velocity of distant galaxies. "
] |
[
"Whether space is open, closed, or flat doesn't affect it. The quantum effect is just too small to notice at classical, much less cosmological, scales. The uncertainty principle isn't proportional. It's an absolute size minimum on the uncertainties. When the values measured are very large, those size minimums are stupendously low proportionally. "
] |
[
"Just to be clear, whether space is open or closed or flat DOES affect exactly how distance and velocity are related (so far it's indistinguishable from flat). It just doesn't affect whether the uncertainty principle is important in those measurements."
] |
[
"What part of honey is antimicrobial?"
] |
[
false
] |
I've often heard that honey is antimicrobial, and it does seem to have an incredible shelf life for something that's mostly sugar and water. What is in honey that keeps it from going bad?
|
[
"Oddly enough, it's the sugar. Honey is so concentrated that it exerts tremendous osmotic pressure, essentially meaning that it sucks the water right out of micro-organisms. In addition, it's fairly acidic, and contains some hydrogen peroxide. You do have to keep honey sealed, or it will absorb moisture and eventually spoil."
] |
[
"And this is known as the ",
"water activity",
" of something. If you add enough sugar there isn't really any living thing that can hold water, and without water there is no life.",
"In fact low water activity is the main preservative in MANY foods. It's the reason syrups don't really spoil (honey, maple syrup, chocolate syrup), it's the reason dried foods don't need refrigeration while their wet counterparts do (fruit, meat/jerky, chips, cereal, bread)."
] |
[
"Strictly speaking honey is \"bacteriostatic.\" meaning that it inhibits the growth of microorganisms but doesn't kill them reliably.",
"This is mostly due to it's low water activity and high sugar content, it tends to dehydrate cells exposed to it. ",
"Honey which has been heavily diluted with water is used to make ",
"Mead.",
" When water is added yeast and other microbes don't have much of a problem growing in it.",
"Honey does contain small amounts of proteins but as far as I can tell, not much study has been done to identify and characterize them. Most abundant seems to be a number of proteins from the Major Royal Jelly Protein (MRJP) family.",
"http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2621.2011.02847.x/abstract",
"The function of these proteins is uncertain. They're found in a wide range of insects, not just bees. Note MRJP is not the same as the hormone that triggers the development of larvae into queen bees, Royalactin. Also found in royal jelly."
] |
[
"If I take half a dose of a drug, does it last half as long, or is it half as effective, or is it a mix of both?"
] |
[
false
] |
For example, if I drink half of a Five Hour Energy, do I have lots of energy for 2.5 hours, or some energy for 5 hours? Or is it somewhere in between? Also, is it different for different drugs, like tylenol or adderall?
|
[
"It would come down to the ",
"dose-response curve",
" of the drug. It may be that the drug works but for a shorter time or it may not work at all. You need to overcome a minimal effective concentration or ",
"minimal inhibitory concentration",
" and enter a therapeutic range for many drugs. This would be especially noticeable in antibiotics where not surpassing a certain serum concentration could mean that the bacteria are not significantly affected.",
"Think about that sigmoidal plot in the dose-response curve, now imagine a dotted line at some point in the response that corresponds to the minimal amount you must have to feel the effect. If the drug concentration never makes it above that line, then there will not be the effect you are looking for. You then need to think about metabolism and secretion to determine how long the drug will be above that line. ",
"Many drugs follow either zero or first order ",
"kinetics",
". Then there are other factors that complicate things like repeated administrations to build up to a desired serum concentration and sequestration in other parts of the body. "
] |
[
"It depends on the mechanism of action. Seroquel 50mg = sleeping pill/anti-histamine; 100mg = antidepressant; 200mg = mood stabilizer; >300mg = antipsychotic. Same molecule.",
"This three-part series (parts ",
"one",
", ",
"two",
" and ",
"three",
") should give you an idea of how deep the rabbit hole goes."
] |
[
"My personal knowledge about drug delivery (specifically, dissolution, some basics about drug kinetics, and that really boring pharmacy class I took 2 years ago) concur."
] |
[
"Does the moon cause tides in the mantle of the Earth similar to the tides it causes in the ocean?"
] |
[
false
] | null |
[
"Actually, it is estimated that the earth internal heat was 3% the effect of the friction caused by the moon pulling the mantle over the years. This has caused the moon to lose it's orbital height slightly and you can make some estimates of the early times of the moon based on model and calculation of the earth internal geology although this is not very accurate."
] |
[
"The moon does warp the shape of the Earth, but it is only a very slight difference since the mantle is ~99% solid and far more rigid than the oceans. Other planet-moon pairs where there are much larger masses involved (Like Jupiter and Io) can distort the moon's shape enough to cause significant friction and heating, but we don't see that to any significant degree with the Earth/Moon pair."
] |
[
"Well, it's observable by instrumentation - not observable on a scale normal human senses could pick up. Practical effects are a slight increase in temperature inside the planet, but that is about it. Other factors influence volcanism much, much more. ",
"It undoubtedly has ",
" small impact on many different things, but nothing I can think of besides inner-Earth temperature that is even worth mentioning. And even that is far outmatched by radioactive decay and latent heat from the formation and differentiation periods of the Earth."
] |
[
"Muscle memory and brain injuries"
] |
[
false
] |
Does muscle memory remain after any brain injury/trauma where there is memory loss? For example, a weight lifter ends up with a brain injury and is not able to train for a few months, and also ends up with some memory loss that might or might not be about his weight lifting. Does the muscle memory still remain or will the lifter have to start from scratch?
|
[
"Muscle memory is actually stored in both the basal ganglia and the cerebellum, the cerebellum is a part of the brain dedicated to motor control. The basal ganglia is a much deeper structure in the brain and is responsible for a lot more then movement; including cognition and emotion. ",
"Losing the ability you train for is called detraining and is a crucial part of athletic performance. When an athlete follows a programme, in the off season they will dedicate time to train for new abilities and the in season training is supposed to preserve these abilities. Different abilities such as endurance or strength are lost at different speeds.",
"So to answer your question; yes the weightlifter would have to start from scratch as they would have lost the strength, speed and also would be less accustomed to the stress that exercise places on the body."
] |
[
"Muscle memory is formed and stored in the basal ganglia. A brain injury that spares these parts will not impact muscle memory. This is where you get those stories of people getting brain injuries and losing memories but they can still do things like tie shoes or perform repetitive motions that they did before the injury. "
] |
[
"There exists more than one type of memory, so the answer to your question depends on the specific injury. A good example for your question is ",
"patient H.M.",
". He had surgery on both hemispheres of his brain in an attempt to treat an intractable seizure disorder. Unfortunately, he was left with an inability to form new declarative or episodic memories. In other words, he no longer had a narrative of his life: he did not know the year or what had happened an hour or even 5 minutes ago (really anything that happened after the surgery). However, his ability to learn new motor skills was preserved. He did not recognize the apparatus used, but he nevertheless was able to improve his performance with practice. In this case, the lesions were precise, having been created surgically. Lesions created by blunt or penetrating injury (e.g., car crash, gunshot wound) or infection (e.g., encephalitis) are not likely to be as precise. Lesions created by degenerative processes (e.g., Alzheimer's Disease) tend to follow specific patterns, impairing different cognitive processes in a relatively similar manner/timecourse across individuals The pattern of deficits is how diagnoses are made by neuropsychologists. Alzheimer's disease begins near the hippocampus, creating problems with memory and spatial cognition, while frontotemporal dementia begins in the frontal cortex, impairing executive function and social cognition."
] |
[
"Charon is being considered as a dwarf planet because its orbit makes Pluto wobble. Why?"
] |
[
false
] |
[deleted]
|
[
"It's because their common centre of gravity (the point about which they orbit or 'wobble' in the case of the larger mass) is entirely outside the surface of Pluto."
] |
[
"Huh, didn't realize that Jupiter was massive enough to have a barycentre with the sun outside of the suns radius.",
"I'd think it gets even more complicated to work out the solar system barycentre,or rather the centre point around which all the bodies effectively orbit once you take all the other gas giants into account ",
"Edit: Here is an ",
"image",
" showing the solar barycentre over the last few decades."
] |
[
"Which is fine, but the other day I read that jupiter and the sun do the same thing! Now obviously we aren't going to call the solar system a binary system, but that puts it in a different category to the planets. "
] |
[
"If the earth rotated on a horizontal axis like Uranus would it make much difference to life on earth?"
] |
[
false
] | null |
[
"Edit: For anyone who doesn't know about the rotational axis of Uranus and what this question is about, see ",
"this",
".",
"The seasons would be very extreme. Basically the polar circles would be at the equator, and all seasonal effects now only happening at polar regions would affect the whole globe to some degree. All of Europe and United States for example would experience several months of ",
"polar night",
" in a year, meaning that the Sun does not rise at all. Obviously this would affect temperatures greatly. The opposite then happens in the summer, the Sun would stay above the horizon throughout the day. ",
"Both of these effects would also be much stronger than they are now. Now in the polar regions the Sun might stay above the horizon through the day but it is still very low all that time so the temperature doesn't get very high. With the axis of Earth tilted 90 degrees, the Sun would stay almost directly overhead for months at a time at the polar regions, there would be hardly any change between a day and a night. Basically you have a time period lasting months which is equivalent to the midday of current equatorial regions. ",
"I won't speculate what exactly this would have done to the evolution of everything but the change in seasonal variation is so extreme that certainly it would have had some kind of an effect."
] |
[
"This is assuming that the geographical and geological features of the Earth would be the same as they are now. But since with a different rotation the shape of the Earth would be different can we actually assume that the way the continents panned out would be same?"
] |
[
"Yes true. I just figured it was easier to refer to different latitudes like that. When I said Europe and United States I really meant anything beyond about 30 degrees northern or southern latitude, whatever continents might be there.",
"I have no idea how the continental movement would be affected but I guess it would somehow."
] |
[
"What makes things soluble?"
] |
[
false
] |
[deleted]
|
[
"Alright, I'm going to cite heavily from ",
"Intermolecular and Surface Forces",
" here. I'm going to assume you're talking about a solid salt dissolving in water, but the same general framework is true for anything, with modifications.",
" The solubility of a solid in a liquid depends on whether the individual molecules or ions of these things \"like\" being with each other more than they \"like\" being with themselves.",
"First, imagine the crystal structure of the salt. ",
"NaCl",
" (table salt) is a good example. Every solid structure has an innate \"formation energy,\" meaning the energy that is gained by making it from its individual elements. For instance, in NaCl each positive Na+ ion is surrounded by 6 negative Cl- ions, and feels an attraction to them according to ",
"Coulomb's Law",
". Of course, it also feels repulsion from the Na+ ions on the other side, attraction to the Cl- ions on the other side of those, etc., but all of that is rolled into the formation energy.",
"Now imagine the ",
"structure of water",
". Every atom of oxygen shares electrons with two atoms of hydrogen in the form of covalent bonds, which is very energetically favorable. In the liquid state, water also forms transient hydrogen bonds with 3-4 of its neighbors, on average. Those bonds have an energy associated with them, which makes them favorable. Additionally, water molecules experience non-directional attractive forces with their neighbors called dispersion forces (often called Van der Waals forces). All of these things contribute to the formation energy of water.",
"In order to figure out whether the salt is soluble, we have to ask what kinds of intermolecular bonds will form/break if it dissolves, and what the energy gained/lost is from each of them. If the final \"dissolved\" states, combined, are lower in energy than the initial states combined, then the salt will dissolve. In the case of NaCl, dissolving into water results in \"",
"solvation",
"\" of the individual ions. Water molecules will orient themselves around Na+ so that their negative (oxygen) ends point towards the positive charge, which is energetically favorable, and vice versa for Cl-.",
"HOWEVER, when the water molecules do this, they lose the freedom to move around as much as they did before. The structure of water becomes more ordered, which is energetically UNfavorable due to a loss of entropy. Also, because the individual ions are now spread apart instead of packed together, Coulomb's Law says that the force they exert on one another gets diminished. This is also unfavorable.",
"In the case of NaCl, the energy gained from solvation more than outweighs the sum of energy lost by water due to entropy, and the energy lost by the ions due to being spread apart. Therefore, it is overall favorable for NaCl to dissolve."
] |
[
"Dissolving happens when dipoles react to ionic bonds. When charges on the ions attract dissolving substance, the dipoles manage to 'screen' charge of ions for each other so the force holding them together weakens."
] |
[
"Like dissolves like. Things that dissolve in water are called hydrophilic or ionic/polar. The hydrogens in water are slightly positively charge (not a full ionic charge like Na+) and oxygen has a slightly negative charge. This happens because in a molecule, the atoms share electrons, but unequally. Oxygen nuclei have a greater affinity for orbiting electrons; affinity for electrons roughly correlates to how far to the right an atom is on the periodic table. Oxygen and hydrogen in water are \"polar\" enough to interact with charged or other polar/partially charged molecules.",
"Things that dissolve in oil are called hydrophobic or non-polar. They have very little or absolutely no charge because electrons are shared almost equally. While they can still interact with each other through Van der Walls forces, they have an aversion to interacting with polar molecules because those interactions are too unstable and a lower energy/more stable state can be achieved."
] |
[
"Could or do steam power plants close to coastlines double as desalination plants?"
] |
[
false
] | null |
[
"They can't use salt water in the boilers or turbines. Regular tap water is not even good enough. Steam power plants use incredibly pure water (the contaminants are measured in the low ppm). This water is heated in excess of 600 Degrees and many of the contaminants found in un-purified water would react with and corrode the boiler and turbines.",
"So yes the water that is boiled would probably be quite drinkable. however because it needs to be ",
" pure to be used in the turbines, it would be far too expensive to use it as drinking water.",
"The plants that do desalination use the steam, after it has exited the turbine, to heat and boil seawater to desalinate it. The ultra pure turbine water is recycled and fed back into the boiler.",
"EDIT: ",
"Wikipedia link about Thermal power stations and their water and boilers"
] |
[
"There are already power plants that do this. Theres an actual word for what you are talking about.",
"Cogeneration: The use of excess heat from power production to accomplish another task.",
"They have plants all over the world that use this system to desalinate sea water."
] |
[
"You are right that drinking ultrapure water can be dangerous, but this is only the case when drinking it on a regular basis. So yes it would be unsuitable as a drinking water supply, but its not going to burn your mouth or anything. The main issue is that the water leaves you body with more minerals than it entered with. If you don't replace those minerals through your diet then you're going to have problems.",
"The article you linked even mentions the bitter taste of it."
] |
[
"Is there a name for this/am I just imagining this? (Genetics)"
] |
[
false
] |
[deleted]
|
[
"There is a phenomenon called ",
"chimerism",
", where the zygotes of fraternal twins merge into a single embryo, resulting in one organism whose DNA varies throughout their bodies.",
"I'm not sure if it expresses in the way you describe. As always, seek advice from a medical professional on such matters."
] |
[
"Sounds like a normal degree of variation that occurs in the development of all symmetrical animals; when symmetry is dependent upon a complex series of gene expressions within spatial perimeters defined by protein gradients—themselves the product of previous gene expressions and their interactions—then variable amounts of imperfections are near inevitable. Furthermore, these physical asymmetries are not confined to prenatal development, but can be accentuated, attenuated, or even arise ",
" during any phase of child maturation.",
"I don't think it's anything to lose sleep over; even monozygotic twins, who more or less share exact duplicates of a common genotype, do not have precisely the same phenotypes."
] |
[
"Apparently you can check."
] |
[
"Statistically speaking, is there any Isaac Newton in my bowl of porridge?"
] |
[
false
] |
Was pondering this thought with a colleague. Is there any chance any of his molecules are in my breakfast?
|
[
" There will be about 10 million atoms of Isaac Newton in every ounce of your soup. The same is true for any other person who ever lived. ",
" You are what you eat. I mean that in a very literal sense too; your body uses the food you eat to build tissue and it uses the water you drink to subsist. By this logic, Newton wasn't just one 150 lb chunk of meat walking around, but he was constantly replenishing and replacing atoms in his body. Basically, the longer you live, the more 'stuff' that has been a part of you over the course of your life. The atoms in baby Newton are probably long since gone in the frail oldman Newton, so again, the longer you live, the greater your lifetime total of atoms that were once apart of you.",
"Assume Isaac Newton consumed about 1 kg of matter every day of his life. This would be some mixture of different elements, but it's mostly water, so let's just work with that. ",
"This wouldn't be a bad assumption either, as water makes up more than 50% of the food-mass in your average diet.",
" Since water has an atomic mass of 18 (two A=1 hydrogen, one A=16 oxygen), we'll say that about 55 moles of water passed through Newton every day of his life. This works out to a little more than 10",
" water molecules per day. Newton was 84 when he died, so let's say ",
"that about 10",
" molecules of water",
" passed through him over the course of his life. ",
"How does this compare to the total number of water molecules on earth? ",
"Wikipedia",
" tells me the water content of the earth is about 1,338,000,000 km",
" - which gives me a total of about ",
"10",
" water molecules on earth.",
"If we assume that the matter that Isaac Newton consumed in his life has been well distributed back into the environment through the water cycle, then we can calculate the number of Newton's atoms that are in a given mass will be given by: ",
"(No. Newton Molecules in your soup) = (No. Atoms in your Soup) x (No. Newton Molecules) / (No. Total Water Molecules on Earth) ",
"Since that last fraction is about 10",
", that roughly tells us that any collection of more than 10",
" water molecules has pretty good odds of containing some atoms from Newton, and it turns out that these are ",
" good odds. ",
"It means that for every ",
" of water that you have, about 10 million atoms in it must have passed through Isaac Newton.",
"Of course, there's nothing unique here about Isaac Newton- this math is true for pretty much every person that has ever lived. There's only so much water in the world, and we've been re-drinking it for as long as we've been around, so statistically, in the average glass of water, you've got a taste of the overwhelming majority of humans who have ever lived. You've got Einstein, Alexander the Great, and even a little bit of Hitler, all mixed together with the atoms of billions more. Also dinosaurs, but let's not get into that. "
] |
[
"The water didnt necessarily just pass right through him. Your body uses water in everything, so a good portion of those 10 million atoms will have been his sweat blood and tears ( and everything else). ",
"What Im trying to say is that Newton spit in your food :/"
] |
[
"Does that take into consideration that he'd likely be using particles previously part of him? Surely there's diminishing returns in a method difficult to caluckate"
] |
[
"If a predator had an endless supply of prey, would they get fat?"
] |
[
false
] |
So theoretically speaking, if a predator has access to an unlimited supply of prey, which take minimal effort to catch and eat, would that predator typically just continue eating as much of that prey as possible and subsequently get fatter, or would there be a reason for the predator to regulate its hunting/ eating as to not get fat?
|
[
"It depends on the predator. Some animals will stop eating when they are full. Most large animals will consume enough food today that they can go tomorrow without food. There is a limit to how many days food they are willing to store. Some predators are also prey and they have to maintain the ability to run. In the case of humans, I think that there is too much research on what tastes good and food companies have figured out how to sell us more than we should eat."
] |
[
"It's not just what tastes good, which is definitely a large part of it.",
"Changes in portion sizes, in the US at least, have played a large role in obesity.",
"If you look at nutritional guidelines and prepare a meal at home, then have that same dish at an American restaurant, I suspect you'll find that the restaurant is feeding you significantly more calories, all of which you're paying money for, and all of which are producing profit."
] |
[
"Bears will always choose to get as fat as possible. They don't need to run from anything and they are adapted to save up for hibernation. A few years ago one in NC got access to a pig farm and turned himself into a blimp."
] |
[
"When integrating a linear reciprocal function that can be factorised, should you factorise the function before integrating?"
] |
[
false
] |
This might be a stupid question, however I have noticed that when integrating a linear reciprocal function which can be factorised, you get different results depending on whether you factorise it or not. For example, if you integrate 1/(3x + 9) without factorising, you get 1/3ln(3x + 9) + C However, if you factorise 1/(3x + 9) first and integrate 1/(3(x + 3)), you get 1/3ln(x + 3) + C My question is, should you factorise a linear reciprocal fuction before integrating it? I thought that maybe the constant of integration would account for the difference, however I can't see how that would work for definite integrals. Sorry if I'm being an idiot.
|
[
"I thought that maybe the constant of integration would account for the difference,",
"This is correct. ln(3x + 9) = ln(3(x+3)) = ln(3) + ln(x+3), so the difference is the constant ln(3).",
"however I can't see how that would work for definite integrals",
"Constants of integration never affect definite integrals. If F(x) = G(x) + C, then",
"F(b) - F(a) = (G(b) + C) - (G(a) + C) = G(b) - G(a). "
] |
[
"As it has been pointed out that it doesn't change the result in this case, but it's worth noting that factorizing is one way to solve more complicated integrals.",
"For instance, consider (x",
" + 3x +4)/(3(x",
" + x",
" + x +1)). This looks like a nasty thing to integrate, but once you realize that you can write the denominator as (x",
" + 1)(3x +3), you can use a technique called partial fraction decomposition to write the original function as 1/(x",
" + 1) + 1/(3x +3)."
] |
[
"ln(x+3)/3 and ln(3x+9)/3 are the same up to a constant of integration."
] |
[
"Why is it bad if air bubbles get into your bloodstream?"
] |
[
false
] | null |
[
"The heart muscle contracts and pushes blood forward. The air will travel through your circulatory system until it gets to your heart. Because air can be compressed much more than liquids can, the heart squeezes the air but it just pushes the air molecules closer together instead of pushing the air forward, meaning blood is no longer flowing. Your blood is not being oxygenated and your organs starve. "
] |
[
"Short version: it takes up space that should be occupied by blood, screwing up circulation.",
"http://en.wikipedia.org/wiki/Air_embolism",
"A small one isn't likely to cause problems. A big one will kill you."
] |
[
"Yup. I'm not sure how much air. If there are little bubbles (champagne bubbles) in IV tubing, we don't worry about it. 10ccs would probably do it. ",
"There's something called a central line- an IV where the tube in the blood vessel goes all the way to the heart. I've heard of a patient dying because someone accidentally took the cap off of the line, allowing air to enter. "
] |
[
"I can keep my eyes active while closed, to a slideshow of 5 crazy morphing images/second. What's going on?"
] |
[
false
] | null |
[
"I can do this too! It's usually scary monster faces that merge and morph randomly every second or two. I thought I was the only one!"
] |
[
"Do you do it to try to fall asleep, or can you do it any time? What do you do to start it?"
] |
[
"I usually do it out of pure boredom. I would say mostly at night when im chillin or dozy. Sometimes my brain 'isn't in the mood' and it doesn't work, or it might take a while to snap into the mode.",
"Another variation I do is where i get cloth material or a jumper and but it over my eyes - the cloth has to be thin enough to let light through and so you can see its texture. Then squint and do the slideshow crazy face thing... It becomes almost light a hallucination, very trippy. I've seen aliens and shit!"
] |
[
"How easy is it for electricity to arc in a vacuum?"
] |
[
false
] |
I'm doing a project that's going to involve running a bunch of electronics in a near vacuum. Unfortunately I have basically zero experience working in a vacuum. I've done my best to account for a lot of the factors that could affect the circuit based on what I've been reading, but my big concern is that I need a kill switch that will physically disconnect power from the circuit controlling a set of 12V motors while it's being pressed. I've found a number of normally closed buttons that would work under regular conditions, but my concern is that the voltage can just arc across the leads in the switch even if it's opened once it's in the vacuum. Realistically, is this something I will likely need to worry about, or is there an equation that can give me an idea of whether or not arcing is likely? If you need more info. The switch is going to be connecting a 12V battery to a circuit, and the physical action that's going to press the switch is at most an inch. I'll have electronic measures as a backup, but ideally I would like to be able to physically cut the power.
|
[
"In vacuum, there is no conductive material to allow current to flow through it."
] |
[
"Arcing through air is easier than arcing through vacuum, because the air can be ionized and provide a conductive path for the current to flow through.",
"You can see a list of dielectric strengths of various media ",
"here",
"."
] |
[
"I work with a small hydro-electric power system. Our main switchgear uses vacuum breakers. It's designed for 5kV at up to 100A.",
"Anyhow, the actual switching is a set of contacts inside a glass bottle. The bottle is under strong vacuum, and the contacts are moved via magnetic forces.",
"Anyhow, the long and short of it is that the switchgear can break the 100A of 5kv, and do so under load, killing the circuit in less than 1/4 wavelength. The only arcing would come from some potential vaporization of the contact metal."
] |
[
"Does an interferometer add or multiply together signals? Is it either?"
] |
[
false
] |
I'm studying honours physics right now and have to get an understanding of interferometers, specifically in the context of astronomy and interferometer telescope arrays. However, I'm having some trouble as we only covered the basics of interferometers in undergrad. We went over stuff like the Michelson-Morley experiment and obviously did wave interference, but not as much in terms of modern application. It seems to me that devices where multiple light beams are sent to interfere directly, and then detected, are called interferometers. This makes sense to me as you are using the interference of the two signals to measure something or to filter noise. But, in the notes I have for my project, the basic example of an interferometer array made of two telescope dishes looking at some source has the signal correlation be a multiplication instead. I understand that this would also show you where the signals correlate, and would cancel out some random noise that is specific to one of the telescopes. But this doesn't really seem like it is interference. Or am I just doing wrong something really basic to do with interference? Thanks.
|
[
"There are a couple things that you could be referring to:",
"1) There are a number of trig identities that turn adding two trig functions into multiplying two trig functions. One that you may have seen in class is the beat frequency: Add two waves with similar frequencies, and it becomes one wave with the mean frequency, multiplied by sin(Deltaf*t)",
"2) Cross correlation function multiplies one signal by a time shifted version of another, then integrating, with the largest value indicating the actual time difference."
] |
[
"you may have seen in class is the beat frequency",
"To actually get the beat frequency, say 1000Hz & 1050Hz = 50Hz (actualy 50Hz & 2050Hz, the sum and differences), requires non-linear interactions. Otherwise adding the two merely ",
"linearly superimposes them",
", while the ",
" shows the beat. There is NO 50Hz present. One non-linear way to combine the two is multiplication. Such as in your cross correlation."
] |
[
"Two waves at a point in space: Y1=A*sin((w0+wb/2)t), Y2=A*sin((w0-wb/2)t)",
"Y1+Y2=A*[sin(w0t+wbt/2)+sin(w0t-wbt/2)]",
"sum of angle identity: sin(a+b)=sin(a)cos(b)+cos(a)sin(b)",
"Y1+Y2=A*[sin(w0t)cos(wbt/2)+cos(w0t)sin(wbt/2)+sin(w0t)cos(wbt/2)-cos(w0t)(sin(wbt/2)]",
"Y1+Y2=2Asin(w0t)cos(wbt/2)",
"",
"Linearly adding them has you end up doing multiplication. Yes, there is no 50Hz frequency actually present (technically 25 Hz, but you square the envelope to get the intensity, so intensity varies at 50Hz)."
] |
[
"AskScience AMA Series: I'm David Pogue, tech and science writer, and host of NOVA PBS' new series Beyond the Elements. AMA!"
] |
[
false
] |
A former weekly tech columnist from 2000 to 2013, I'm a five-time Emmy winner for my stories on , a bestselling author, a five-time TED speaker, and host of 20 science specials on PBS. My most recent special is a mini-series called " ," a sequel to my 2012 documentary " ," which has become a staple in science classrooms worldwide. The new show's three one-hour episodes take me on a worldwide quest for the key molecules and chemical reactions that make up human civilization, including concrete and fertilizer, plastic and rubber, fire and venom, explosives and hot peppers. I've written or cowritten more than 120 books, including dozens in the Missing Manual tech series, which I created in 1999; six books in the line (including , , , and ); two novels (one for middle-schoolers); my three bestselling books of tips and shortcuts (on , , and ); my how-to guides and ; and my 620-page magnum opus, . After graduating summa cum laude from Yale in 1985 with a distinction in music, I spent 10 years conducting and arranging Broadway musicals in New York. I won a Loeb Award for journalism, two Webby awards, and an honorary doctorate in music. I live in Connecticut and San Francisco with my wife Nicki and our blended brood of five spectacular children. For a complete list of my columns and videos, and to sign up to get them by email, visit . On Twitter, I'm ; on the web, I'm at . I welcome civil email exchanges at , and of course, AMA! I'll be on at noon (ET; 16 UT), AMA! Username:
|
[
"David Pogue! I used to love your tech reviews. Feels like a long time ago, when the internet was a different place. \nI see you continue to be insanely prolific. I'll check out some of these links. ",
"Question? What's your favourite element?"
] |
[
"I used to love those tech reviews, too! :) ",
"Favorite element: Sodium, for a really personal reason. Of course, sodium explodes violently with water—but when we mix it with a lethal gas (chlorine), we get table salt (NaCl). This is nothing new--but one of the early NOVA shoots on \"Hunting the Elements\" involved visiting author Theo Gray, who actually DEMONSTRATED the explosion (and the table-salt making) on camera. It was one of the first times I witnessed the point of a NOVA script illustrated right in front of my face, and I've never forgotten it!"
] |
[
"You've heard of most of them--self-driving cars, phasing out coal, etc. But here's one that's not on anyone's radar: SIT (sterile insect technique) for mosquitoes!",
"With climate change, mosquitoes are advancing northward incredibly fast, making more people sick in more places. Insecticide and genetic engineering are both problematic. But Verily (Google's sister company) performed an amazing test in 2017, 2018, and 2019, where they released millions upon millions of modified males into Fresno, CA. (Not genetically--just infected by a harmless common bacteria that made their offspring non-viable.) Within a single summer, the mosquito population dropped by 95%!",
"Their next experiment is Singapore--they're going to try to eliminate Dengue fever entirely! This is the kind of safe, smart approach that gives me real hope!"
] |
[
"Are solar panels in hotter places more efficient than solar panels in other, cooler temperatures?"
] |
[
false
] |
By hotter places, I mean surface level temperature and the temperature you see on the weather Does it even make a difference ? If so by how much?
|
[
"The technically correct answer is that lower temperatures are more efficient, the thermal coefficient is about -0.4%/⁰K, see PV panel datasheet ",
"example (pdf)",
", however, that colder temperature usually means the sun is lower in the sky, losing energy due to ",
"air mass",
".",
"\nFind locations of interest on ",
"https://pvwatts.nrel.gov/",
" and compare the \"AC Energy (kWh)\" on the last page. "
] |
[
"I don’t believe it’s the temperature that matters",
"Solar panel efficiency decreases with increasing temperature",
"."
] |
[
"What happens is that temperature shifts the bandgap of semiconductors. Very low or very high temperatures can have ",
"dramatic effects",
" on the color an LED emits, and on the colors that solar panels can efficiently absorb.",
"Almost all solar panels on the market use silicon as their semiconductor. Silicon has a bandgap of 1.1 eV while the \"ideal\" single-junction solar cell for absorbing sunlight would have a bandgap of about 1.34 eV. Silicon's not a bad material - we just need to find a redder star.",
"Gallium arsenide and other alternative solar cell semiconductors have bandgaps that are too high for the sun, and these cells become more efficient the hotter they are (to a point)."
] |
[
"Reddit, my bedroom is directly above my kitchen. Every time someone switches on the microwave, my internet freezes for whatever the duration of the time set. Why is it doing this, and how can I stop this happening?"
] |
[
false
] | null |
[
"Interference. You can stop it by using a hard-wired connection instead of wireless. Failing that, reposition your wireless access point or your microwave. "
] |
[
"I presume you mean your wireless internet. ",
"Get an 80211.n wireless instead of b/g. Different frequency. "
] |
[
"You could also change the channel your router is signalling on, I'd suggest doing that as well."
] |
[
"Ask Anything Wednesday - Engineering, Mathematics, Computer Science"
] |
[
false
] |
Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical post? No question is too big or small for AAW. In this thread you can ask any science-related question! Things like: "What would happen if...", "How will the future...", "If all the rules for 'X' were different...", "Why does my...". Please post your question as a top-level response to this, and our team of panellists will be here to answer and discuss your questions. The other topic areas will appear in future Ask Anything Wednesdays, so if you have other questions not covered by this weeks theme please either hold on to it until those topics come around, or go and post over in our sister subreddit , where every day is Ask Anything Wednesday! Off-theme questions in this post will be removed to try and keep the thread a manageable size for both our readers and panellists. Please only answer a posted question if you are an expert in the field. . In short, this is a moderated subreddit, and responses which do not meet our quality guidelines will be removed. Remember, peer reviewed sources are always appreciated, and anecdotes are absolutely not appropriate. In general if your answer begins with 'I think', or 'I've heard', then it's not suitable for . If you would like to become a member of the AskScience panel, . Past AskAnythingWednesday posts . Ask away!
|
[
"In the future do we think they might be able to delete memories?",
"I’m thinking brain mapping technology. EMDR, neuroplasticity but using computers to actually reprogram us, rewire us. PTSD and survivors. ",
"Too sci-fi or an actual possibility?"
] |
[
"I've read that mobile communication like LTE is limited when moving fast, such as using it on a train or car. See ",
"here",
" for example.",
"What causes this limitation and why is this not an issue with internet on planes?"
] |
[
"*Correct me if I'm wrong* But sending any kind of signal that needs satellites requires a steady place. Imagine you send your signal to the satellite in space and it needs to resend the feedback signal. So if you move faster the signal will have a harder time to hit your location as it is changing fast. Planes, on the other hand, are closer to the satellites so they have an easier time to pick up the signals. I'm not 100% sure about this tho need to do further investigation."
] |
[
"What if we could see more of the electromagnetic spectrum?"
] |
[
false
] |
[deleted]
|
[
"there is a condition known as ",
"Aphakia",
" where the lens of the eye is removed. The lens is a 'strong' UV absorber and after its removal some people are able to be able to see ultraviolet down to ~ 300 nm. They report seeing blue/white/violet light. "
] |
[
"Well, the sky would look like ",
"this"
] |
[
"This is kind of a fun experiment -- most phone cameras can see into the infrared frequencies. Next time you're watching TV turn on your camera and point it at the tip of your remote control where the little light is. When you press any button on the remote you'll see the flash of IR light through your camera but not with your naked eye.",
"Then use your phone to see what else emits IR light! "
] |
[
"Will the push to cloud services eventually lead to bandwidth saturation?"
] |
[
false
] |
I remember hearing a few years back that there was barely enough bandwidth to keep up with the mobile devices in existence, this was ~5 years ago. Of course, I believe it was offered as a defense against criticism of Comcast pricing, so take it for what its worth. But, reductum ad absurdum- will moore's law eventually be unable to keep up if we move ALL services, software, and data storage to the cloud? I think it will, thats why I'm sticking with my desktop, linux, and local music and move storage. I don't think the cloud is the future and everyone will eventually be back to the desktop.
|
[
"Mobile devices are subject to frequency limitations; there are only so many channels to transmit on and once they are in use you are at capacity. This can be combatted with shorter range coverage, which we already see in the use of WiFi. Many locations within the range of one cell tower can reuse the same WiFi channels because they are too far away to interfere with each other.",
"Wired cloud devices are safe because more machines with more wires have no intrinsic choke point of interference with each other."
] |
[
"Thanks for the clarification. I'm not necessarily assuming infrastructure will stagnate, just wondering if development can keep up. "
] |
[
"Thanks for the clarification. I'm not necessarily assuming infrastructure will stagnate, just wondering if development can keep up. "
] |
[
"What is it about copper that gives it anti-microbial properties? Why does bacteria die when it comes in contact with it?"
] |
[
false
] | null |
[
"Copper produces hydrogen peroxide and oxygen radicals via the Fenton reaction. Lipid peroxidation in the bacterial outer membrane ensues, eventually leading to a loss of membrane integrity and cell lysis. A recent ",
"paper",
" reported 10",
" cells being killed in less than 3 hrs. "
] |
[
"Copper truly is the death metal."
] |
[
"So if we make a similar knight's move down the periodic table, we find that shampoo should kill aliens."
] |
[
"A question on herbivores, protein and evolution."
] |
[
false
] |
Two questions, actually: 1) How do herbivores 'get' the necessary protein (and other dietary necessities for animals) without eating other animals? Have they evolved some method of coping with not eating meat in ways that humans and other omnivores have not? 2) What are the evolutionary advantages of having to hunt and kill your food? Why would any animals have evolved to be carnivores? Thanks!
|
[
"1) Plants have protein. Plenty of humans eat only plants and don't suffer from protein deficiencies. ",
"2) Other animals are the most dense source of food energy around, so if you can catch and eat another animal without spending too much energy in the process, it's a pretty good way to spend your time. Herbivores spend a lot of time eating to stay fed. Carnivores spend a lot of time sitting around, comparatively. "
] |
[
"I thought that only animals/dairy had protein",
"Everything that is alive has proteins, they are an essential component of life. This includes animals, plants, bacteria, and even viruses.",
"Proteins are made of amino acids. There are many amino acids, but only 22 are ",
"proteinogenic",
", that is, required in order to make proteins. Of these 22, only 21 are used by eukaryotes (including man).",
"Humans needs amino acids to build our own proteins. We obtain amino acids either through our diet, or by manufacturing them within our bodies. In fact, we can manufacture all except 9 amino acids within our bodies. The 9 amino acids we can't manufacture are called ",
"essential amino acids",
". These we must obtain from our diet.",
"The reason why meat is considered \"good\" protein is because meat has ",
" the amino acids we need, including all essential amino acids. Plant products also have proteins. They can have a LOT of proteins. In fact, some soybean products can have more protein than chicken, ounce for ounce. However, plant protein may not always be nutritionally \"complete\", in that it might be missing certain essential amino acids.",
"In practice, this is meaningless, because nobody eats just one plant product. Most people eat a mixture of plant products, and each plant product may have a different balance of amino acids. So if one food is missing a certain amino acid, it will be made up by other foods. Many traditional cuisines have already selected foods that are complementary in this sense, for example, rice and beans. Both rice and beans are missing certain essential amino acids, but they're missing ",
" amino acids, so when taken together they complement each other and provide \"complete\" protein.",
"It's perfectly possible for vegans to have a nutritionally complete and balanced diet. If they are prone to deficiencies, it's not because their diet makes it so, but rather because of the effort and understanding of the vegan in question. All people are not alike in how much effort they are willing to put into their diet, and how much they understand the principles of nutrition.",
"It is certainly true that it's easier for a non-vegetarian to fulfill dietary requirements and not get deficiencies -- all you have to do is to eat some meat every day. A vegan, at least in our western societies, may have to work harder to find all the foods he needs to keep his diet balanced. A vegan would also need to be more educated about nutrition to ensure that they maintained sufficient variety in their diet to not develop deficiencies. For a meat eater, it's much easier. Just eat meat, in moderation."
] |
[
"Oh - I thought that only animals/dairy had protein, and that vegans (especially) were prone to protein (as well as other) deficiencies?"
] |
[
"What FOV do humans have (like in video games)? Can it very from person to person?"
] |
[
false
] | null |
[
"The field of view is close to 180 degrees. But the resolution are the extreme edges is very low, only able to detect motion. Most of our field of view has low resolution, a human eye only has around one megapixel. Nearly all of that is concentrated in a tiny area in the centre of our field of view, about the width of your finger when your arm is outstretched."
] |
[
"honestly, yes, it's highly variable. there is fov, and then useful fov. it has to do with periphery vision. in this case, you should at least read this ",
"https://en.wikipedia.org/wiki/Vision_span",
" ",
"it's a pretty good explanation."
] |
[
"Human field of view is around 210 degrees horizontally. Each eye has about 150 degrees, with about 110 degrees common to the two and 40 degrees visible only to that eye.",
"While I'm not sure, I'd guess there is a fairly narrow range of individual differences in FOV for humans with binocular vision. Differences in visual acuity, etc, are greater, but since FOV deals mainly with anatomy (shape of the eye and pupil, retinal size) I'd guess it has less variation."
] |
[
"Is there any functional difference between a capacitor and a rechargeable battery?"
] |
[
false
] | null |
[
"The hell are you talking about?\nThat's not just crude, that is completely and utterly wrong, and is absolutely not a good way to visualize anything!",
"Capacitors absolutely don't create some \"pulsation\", although they are ",
" frequently used to ",
" pulsation coming from rectifiers."
] |
[
"Yes. Batteries store small amounts of energy (relative to their mass) and release it over long periods of time, ideally in a mostly constant fashion. Capacitors store large amounts of energy and release it over short amounts of time in an exponential fashion. ",
"From a more theoretical perspective in circuit design, a battery is a voltage source. Even if it's being recharged, the output voltage should be constant. The current charging it should not affect the voltage across the anode and cathode of the battery cell. However a capacitor acts like an integrator, meaning that the voltage across it is a function of the capacitance and the integral of current flowing through the anode. ",
"Furthermore, they arent used the same way. We use batteries in circuits to provide a constant voltage drop and energy source to supply active elements (things that consume energy). We use capacitors as means of changing how the energy flows through the circuit as a function of time. "
] |
[
"Wait what? You know that's EXACTLY how a camera flash works right? A capacitor is able to effectively dump it's entire charge in a fraction of a second. If you let the capacitor charge and then release you are not \"crudely\" defining pulsation, that's literally the definition of pulsation."
] |
[
"Since the event at CERN that proved the existence of Higgs bosons/Higgs field, can we now see this event happen regularly now we know ‘where’ to look?"
] |
[
false
] | null |
[
"It doesn't quite work that way. There never was a single event at CERN that proved the existence of the Higgs. What happened was, they announced a few years ago, and detailed in subsequent paper, a statistical analysis of the decay products detected after countless collision and deduced the existence of a subatomic particle with all the attributes of the Higgs.",
"From the way the physics is done today, there isn't really a place we can look and say \"There it is! That's the Higgs!\" The evidence is always indirect. At these large particle accelerators, beams of protons are directed into each other, resulting in collisions that produce a shower of short-lived subatomic particles that are observed and recorded. The volume of data from these experiments are huge. After tedious and painstaking analysis, a statistical spread of what was detected is examined and may or may not ",
"show something",
" that matches the predicted properties of a particular particle. "
] |
[
"I'll give it a shot:",
"On the axis you can see the production cross-sections of gluon fusion (ggH) and vector boson fusion (VBF)... cross-sections can be interpreted as a measure of \"event frequency\". ggH and VBF are different ways the Higgs can be produced (the 2 most common)",
"The 2 \"blobs\" are 2 of the decay channels for the Higgs boson (like said before, we can't detect the Higgs directly, we can only detect the things it decays into). H→γγ for example means the Higgs decayed into photons. ",
"There is some statistical noise around this measurement, hence the blob. But as you can see both measurements are withing 95% confidence level (CL) for the stardard model (SM) meaning that any model that we put forward as an alternative needs generate this process very similarly to the SM.",
"Incidentally, neither of these is the most common channel, that would be H->bb, but the background is much worst on that channel so the blob would be bigger."
] |
[
"can you elaborate what figure 4 in your link means?"
] |
[
"If magnetic pull between a magnet and a piece of metal operates under an inverse square law, is this then an inverse to the power of 4 when changing the distance between two magnets?"
] |
[
false
] | null |
[
"The field of a dipole goes like 1/r",
", so the ",
"force",
" goes like 1/r",
"."
] |
[
"This is also true between a magnetic dipole and non-magnetized metal, right? Because the magnetic dipole induces a dipole in the non-magnetized metal?"
] |
[
"The same would be true for either an induced dipole or a permanent dipole."
] |
[
"Which 'light' does photosynthesis use exactly? Ultraviolet?"
] |
[
false
] |
Been searching but most sources say it uses 'sunlight' or 'light energy'. I want to know exactly which kind of light it is. Can you technically shine a UV lamp onto a plant and promote photosynthesis?
|
[
"Chlorophyll a absorbs most strongly red light, while chlorophyll b absorbs blue light most strongly. The light that's left over is green light which is why plants look green.",
"Check this out for more detail:\n",
"http://hyperphysics.phy-astr.gsu.edu/hbase/biology/ligabs.html"
] |
[
"Chlorophyll can absorb some UV light, but UV light is also absorbed by many other components of the cell, including DNA. UV light can damage DNA, and is generally detrimental to plant growth, so plants have evolved protective strategies, including producing \"sunscreen\" compounds that absorb UV light. ",
"Here's",
" a cool example of a mutant plant where one of these protective mechanisms is inactive. The wild type plant is stunted by UV light, but the mutant is completely killed."
] |
[
"Well, just from noting the color of the light that the leaves reflect (green), you can tell the color they must absorb (red). ",
"Wikipedia",
" also says some plants absorb at a blue-violet wavelength as well so maybe they can use some UV light. "
] |
[
"How can extra dimensions be 'small' in string theory? And how do these additional dimensions enable string theory?"
] |
[
false
] | null |
[
"Think of a cylinder, the direction \"around\" is always at right angles to \"along\". Now imagine that the cylinder is very (or infinitely) long but has a small diameter"
] |
[
"Only if you want it to be. Imagine something like an old arcade game where the left and right of the screen wrap around to each other, but up and down the screen is really long (and don't wrap around) that's a cylinder that is purely 2D, no need to put it in 3D.",
"The point is though, here is a simple example of how a dimension can be as you think about it and small at the same time"
] |
[
"That's exactly it.",
"The second part of the question relies on stuff that's a lot more technical and I can't think of a good reason it \"should\" be true. The upshot is though that string theory is only even self-consistent when there are a specific number of dimensions, 9 of space and 1 of time (or 25 + 1 for bosonic string theory)."
] |
[
"In terms of killing potentially harmful bacteria/viruses/etc., what is the most effective way of cooking food?"
] |
[
false
] |
Taste or evenness of heating notwithstanding, which method of cooking food would be the most effective in terms of making food safe for consumption? The idea for this question came from on the Lobsters/Crabs feel pain thread in . Would electrocuting your food before cooking it more traditionally (or hell, just cooking it via electrocution) have a more or less noticeable effect on germ populations?
|
[
"You might want to cite your sources on the nutrients claim there."
] |
[
"As long as the internal temp reaches 160, it doesn't matter how you cook it. Digital thermometers are great for checking the temp."
] |
[
"Which nutrients? And how are they \"killed?\""
] |
[
"Does biking uphill require more energy than running uphill?"
] |
[
false
] | null |
[
"Naive analysis:",
"If we assume that the two modes of transportation have no energy losses, then we just compare the change in energy between the initial and final states. Assuming you are stationary at the start and end, the relevant energy is the gravitational potential energy E = mgh.\nWalking, you only have lifted your weight (say 85 kg).\nCycling, you have brought your bicycle as well (say 15 kg). So cycling would appear to require more energy.",
"Better analysis:",
"However this answer is probably wrong because cycling and walking are not equally efficient. Cycling requires about ",
"half the energy per unit distance as walking",
" on flat land. ",
"Suppose the hill road is 1km long and rises by 100m. Cycling a 15kg bike, you would expend about 110 kJ (using wikipedia's numbers) against air resistance and friction, and ~ 100 kJ against gravity (approximating g as 10).\nAn 85kg person walking would expend about 220 kJ against friction and ~ 85 kJ against gravity.",
"In this example (100m rise over 1km distance), cycling is probably more energy efficient -- a savings of 95 kJ. A steeper rise or heavier bike makes the difference smaller.",
"Note you probably will feel more tired cycling, because cycling probably goes up the hill more than twice as fast as walking, and therefore requires a higher power input. In this example a cyclist (16 km/h) has an average power input of ~ 1kW, while a walker (4 km/h) has an average power input of ~ 340 W."
] |
[
"Note you probably will feel more tired cycling, because cycling probably goes up the hill more than twice as fast as walking, and therefore requires a higher power input. In this example a cyclist (16 km/h) has an average power input of ~ 1kW, while a walker (4 km/h) has an average power input of ~ 340 W.",
"Seems like a shallow hill or really powerful cyclist with a ramp. I remember as a child riding bikes over hills in my area two things tend to happen, riding directly up the hill, you slow down massively to the point of being as fast as walking roughly and it becomes very difficult to keep pace and you need to stand upright on the pedals to get weight behind it. Walking up the hill ended up being faster, thus getting off your bike and walking up tends to be significantly easier than riding it up. The way to traverse hills on a bike though isn't by going straight up it but by snaking back and fourth and building side momentum to gradually move vertically. ",
"This shows some bikers doing this, though it's harder in crowded or shallower paths."
] |
[
"on the bike you will only burn a percentage of the total energy required.",
"If by \"total energy required\" you mean the total gravitational potential energy gained by moving to the top of the hill, you've got some conservation of energy problems here. Mechanical advantage has nothing to do with it, since Work is the integral of Force (dot) Displacement, and mechanical advantage is just a tradeoff between force and displacement (a tradeoff that keeps their product F*dx constant) so the Work is unaffected. ",
"It actually is a pretty complicated problem. Unfortunately, it's a problem that involves human physiology just as much as physics, which makes it pretty tough to calculate."
] |
[
"How do planets lose their atmosphere?"
] |
[
false
] |
Can earth lose its atmosphere? How long would it take?
|
[
"To start you off see ",
"Wikipedia: Atmospheric Escape",
". Given that Earth is pretty massive and that the atmosphere is shielded by Earth's magnetosphere, the Earth doesn't undergo appreciable atmospheric escape and thus won't lose its atmosphere in the lifetime of the solar system."
] |
[
"Earth atmosphere would most certainly be blown off by solar winds; however, earth's iron core generates a magnetosphere that protects it."
] |
[
"While Earth's magnetosphere does shield the Earth and its atmosphere from the solar wind, it is not necessary to have a magnetosphere to keep an atmosphere. An example of this is Venus which has a very think atmosphere and no magnetosphere."
] |
[
"How did all the gases in the Earth develop if it formed out of gas clouds of hydrogen?"
] |
[
false
] |
I know that the Sun developed from nebula of hydrogen and helium and the planets formed out of gases that surrounded the Sun by accretion. I also know that before oxygen started liberating from the ocean there was an atmosphere of ammonia, water vapor, carbon dioxide etc. How did all these gases form?
|
[
"The earth itself didn’t form from hydrogen. First generation stars form out of the light elements first, burn bright and hot and relatively fast, making heavier elements in its core. When one goes nova, it spews out heavier elements like carbon and iron, from which second generation stars (like our sun) are formed. They burn smaller and denser and cooler. During the formation, the spinning matter forms an accretion disk, which eventually gives rise to planets. So the earth, everything in it, and everything on it, including you and I, were formed in the crucible of a giant star’s core billions of years ago. As Carl Segan said: you’re made out of Star Stuff."
] |
[
"So the earth, everything in it, and everything on it, including you and I, were formed in the crucible of a giant star’s core billions of years ago.",
"Except the hydrogen and a bit of the helium and lithium."
] |
[
"This is mostly correct, though there are some elements created in the immediate aftermath of the big bang: ",
"https://en.wikipedia.org/wiki/Big_Bang_nucleosynthesis"
] |
[
"Why do mitochondria have their own separate 'mitochondrial DNA'?"
] |
[
false
] |
Do other cells or organelles have their own separate DNA? Is it some relic of the very distant past?
|
[
"It is in fact a relic of the past. Early in the history of life, we believe the eukaryotic ancestor enveloped an aerobic bacterium, but rather than digesting it, it lived within the cell. Eventually, the eukaryote and the bacterium would exchange genetic material, and the two would become interdependent on one another. This is what we call endosymbiotic theory. And there is predicted to be 2 primary events (mitochondria from aerobic bacteria, and chloroplasts from cyanobacteria), and 3 secondary events (green algae and their chloroplasts being taken up by other eukaryotes).",
"You can recognize these events through a few characteristics: extranuclear, circular genomes, independent reproductive cycles, and multiple membranes."
] |
[
"Is it some relic of the very distant past?",
"This is the theory, mitochondrial DNA looks a lot like bacterial DNA so a lot of people subscribe to ",
"endosymbiotic theory",
" for mitochondrial origin.",
"Essentially, the idea is that an early progenitor of multicellular organisms gobbled up a bacteria, and rather than digest it the cell somehow formed a symbiotic relationship and started using it to make ATP (the energy currency of the cell). As best we can tell this only happened once, and some of the details are quite contentious. Still, the big picture idea is pretty well accepted in the field."
] |
[
"They are referencing chloroplasts and possible secondary events of further endosymbiosis. Chloroplasts have three membranes (inner, outer, and thylakoid) and thus are predicted to have undergone a secondary pseudo-endosymbiotic event. Chloroplasts are very similar to mitochondria, but perform photosynthesis to generate (a little) energy and sugar. Mitochondria then convert that sugar into ATP.",
"The initial endosymbiotic event that resulted in mitochondria is thought to have occurred only once. All of these events occurred a long time ago so people are willing to argue about most aspects of it though. That review that I linked from nature goes over a few of the broad strokes.",
"Here is the summary from the review:",
"Mitochondria arose once in evolution, and their origin entailed an endosymbiosis accompanied by gene transfers from the endosymbiont to the host. Anaerobic mitochondria pose a puzzle for traditional views on mitochondrial origins but fit nicely in newer theories on mitochondrial evolution that were formulated specifically to take the common ancestry of mitochondria and hydrogenosomes into account. The presence of mitochondria in the eukaryote common ancestor continues to change the way we look at eukaryote origins, with endosymbiosis playing a more central role in considerations on the matter now than it did twenty years ago. The integral part that mitochondria play in many aspects of eukaryote biology might well reflect their role in the origin of eukaryotes themselves."
] |
[
"The Classic Birds in a Box Question?"
] |
[
false
] |
[deleted]
|
[
"If the box is closed, then the weight of the box remains the same whether the birds are in flight or not.",
"If the top is open, then the weight of the box is a function of how high the birds are, as fluid movement can lead to weight transferred outside the box, especially for cases where the birds are near the top. Obviously the higher the birds go, the less weight is experienced by the box."
] |
[
"No i don't think it would change for the birds.",
"The birds must push on the air molecules in the box to fly. The air molecules would then collide with the bottom of the box, which would impart a downward force to it. The magnitude of this force would be equal to that of gravity, because the bird needs to push up with the same force that gravity pushes down to maintain flight.",
"I think if the box were big enough it wouldn't matter if it was open or closed. Perhaps somebody with experience in aero/fluid dynamics could answer this better than me. Same with the aeroplane question."
] |
[
"Mythbusters did it."
] |
[
"Will antibiotics affect corona virus deaths?"
] |
[
false
] | null |
[
"Hi babamum thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the following flair categories and contain no other text:",
"'Computing', 'Economics', 'Human Body', 'Engineering', 'Planetary Sci.', 'Archaeology', 'Neuroscience', 'Biology', 'Chemistry', 'Medicine', 'Linguistics', 'Mathematics', 'Astronomy', 'Psychology', 'Paleontology', 'Political Science', 'Social Science', 'Earth Sciences', 'Anthropology', 'Physics'",
"Your post is not yet visible on the forum and is awaiting review from the moderator team. Your question may be denied for the following reasons, ",
"/r/AskScienceDiscussion",
"There are more restrictions on what kind of questions are suitable for ",
"/r/AskScience",
", the above are just some of the most common. While you wait, check out the forum \n",
" on asking questions as well as our ",
". Please wait several hours before messaging us if there is an issue, moderator mail concerning recent submissions will be ignored.",
" ",
" "
] |
[
"Flair choice: medicine"
] |
[
"Flair choice: 'Medicine'"
] |
[
"Noah's Ark Thread REMOVED"
] |
[
false
] | null |
[
"So is this an appropriate place to ask that this subreddit be removed from the default home page?",
"EDIT: Hey guys lets move the meta-discussion ",
"here",
" where it's more productive. Thanks"
] |
[
"This is the shit we've had to deal with",
"Please, only answer if A. you actually know what you're talking about, B. the answer is based on scientific evidence or reasoning, C. it actually addresses the question being asked, and sometimes D. if you have a secondary question that adds to the original."
] |
[
"I second this, with more vehemence than my clicking an upvote can muster. If we want /askscience to be without tripe and aggravation for mods - it ",
" to get off the default page.",
"Have reddit make a \"you might be interested in...\" interim step of some sort."
] |
[
"Why can a rocket fly straight up without wings and doesn't tip over?"
] |
[
false
] | null |
[
"Large commercial rockets are actively steered. Either the engines are 'gimbaled' (the angle is adjusted) constantly, or small sideways-pointed rockets are fired as needed, to push the rocket where the computer is programmed to send it.",
"Smaller rockets without adjustable engines or controls normally cause the rocket to spin as it flies, so any off-angle forces are canceled out. Doing this without fins is tricky, which is why smaller rockets generally do have fins."
] |
[
"More fundamentally, ",
"the center of gravity is ahead of the center of pressure",
". This creates a restoring force to counter any destabilizing force.",
"This is why hobby-grade model rockets built by 7-year-olds can launch vertically without active gimbals.",
"On the other hand, gimbals on a large rocket would be useless in resisting the instability if the CP were ahead of the CG.",
"Here's a nice elementary-school-level primer on the subject: ",
"https://www.teachengineering.org/view_lesson.php?url=collection/cub_/lessons/cub_rockets/cub_rockets_lesson03.xml"
] |
[
"The diagram describes rockets with fins. Almost all modern launch vehicles don't have any fins and are actively steered. "
] |
[
"What are the health risks of long term sleep deprivation?"
] |
[
false
] |
As a busy student this is very relevant to me (surely AskScience of all subs can sympathize).
|
[
"In a normal state of mind I'd probably be able to contribute something, but right now I am deep in a haze of sleep deprivation."
] |
[
"How did you... This post is 13 days old. "
] |
[
"Think I was lost somewhere in the CogSci sub-reddit and just kept clicking away. Turns out it's a bad idea for me to browse Reddit while in bed."
] |
[
"How much, if at all, does a human skull grow during adulthood?"
] |
[
false
] | null |
[
"Thank you for the rude response.",
"Also, please see the sidebar:",
"\"Please keep discussion:",
"Civil",
"On topic",
"Scientific (i.e. based on repeatable analysis published in a peer reviewed journal)\""
] |
[
"Thank you for the rude response.",
"Also, please see the sidebar:",
"\"Please keep discussion:",
"Civil",
"On topic",
"Scientific (i.e. based on repeatable analysis published in a peer reviewed journal)\""
] |
[
"After having searched and found only info that indicates no growth in adult skulls...",
"I am searching for information that discusses interpupilary growth or changes in adults and the acceptable tolerances for measurements among nationally recognized Opthamological organizations."
] |
[
"How does your immune system directly help with the digestion of food? Aren't enzymes specific to one purpose?"
] |
[
false
] |
I always thought that enzymes were made for one specific function and that certain enzymes were made to break down a certain kind of carbohydrate or fat or whatever you're digesting. Then I read and got all confused. A nutritionist recently told my father that by eating a bag of sun chips, given that it is not a natural food (natural carbs, fats etc), it is not broken down by the digestive system but by the immune system. The implication is that by involving the immune system and the digestive system it takes away some energy of the body when running. (He is a marathon runner). She also told him that milk is broken down by the immune system. Hence, milk is not a good food. Is this true at all?
|
[
"The idea of your digestive system appropriating enzymes from your immune system is completely false. Enzymes used by the immune system are produced and used in the cells that make them, they don't go to a central depository that gets shared out."
] |
[
"Working on my PhD in nutritional immunology here, so I'll try to help; without more info about how exactly the nutritionist thought the immune system would be involved, it's hard to give a straight answer. ",
"IgA antibodies secreted by the immune cells in the gut can target antigens in the digesta, but their activity is mostly limited to coating the particle so as to minimize its activity/impact on the rest of the system. Not only does this process not result in digestion of the food, the presence of IgA on a particle/microbe will inhibit absorption by the enterocytes. This is a protective mechanism that prevents toxins and invading microbes from getting past your gut barrier and into your blood.",
"Because the body is constantly exposed to non-self proteins through the digestive and respiratory tracts, it produces large amounts of IgA as a matter of course, to prevent problems before they happen. So while this does represent a significant energy drain, it is happening whether your father eats a bag of chips or not. Only a sustained attack/exposure to a harmful substance would result in a specific increase in IgA production, though there is a phenomenon in which high-level athletes show reduced IgA production (mechanism unknown) relative to more sedentary/moderate populations.",
"To address your comment about the function of enzymes; we often think of enzymes in terms of degradation (of food in the body or waste in a septic system, for example), but an enzyme is any protein that catalyzes a chemical reaction and is not consumed during that process. There are thousands of enzymes that are involved in synthesizing new products in your body, copying DNA/RNA, deriving ATP from sugar, as well as those involved in \"breaking down\" foods. There are many enzymes that are going to function in both digestion and immune function, but I have never seen any reference to pancreatic enzymes being critical to immune function. I would not put too much faith in the site you listed; it makes very broad statements without specific examples or good references. The digestive and immune systems are enormously complicated and flexible, and are undeniably linked, which means that anyone can come up with their own theory about what the best diet is, and it is hard to definitively debunk those theories.",
"Also, in what way is a bag of chips not natural food? Is this nutritionist (using the term lightly) recommending a raw diet? Because that certainly comes with its own set of problems. We process foods for a reason - processing (in the most basic sense) typically increases digestibility. However, there are certainly aspects of food production that get lumped under the term \"processing\" that are not healthy in excess, like frying foods or adding large amounts of soluble carbs in place or insoluble ones.",
"Her last statement just seems plain wrong: milk is not broken down by the immune system. Milk is composed of several different components including a wide lipid profile, several proteins (mainly casein) and sugars (mainly lactose). Even if your body no longer produces lactase (breaks down lactose), the other components of milk are still processed and absorbed fairly efficiently. People with milk allergies have antibodies that react to casein and stimulate a superfluous immune reaction (allergy), but this is not the same thing as your immune system doing the work that your digestive system would normally handle.",
"Sorry this ended up so long; I hope this answers your questions.\nSources: ",
"1",
", ",
"2",
"Edit: Grammar, fixed link 1"
] |
[
"Okay, I'm just a high school bio teacher, so somebody will come along and correct my mistakes hopefully. There is a a distant fainting hint at something almost based on science here. Some proteins are more difficult to digest than others. Some peoples' bodies tag these proteins with immunoglobin, and the body can attack them \"confusing\" these proteins for the proteins that are part of digestively resistant parasites. Once tagged by the immunoglobin, this triggers an immune response and an allergic reaction. So, the immune system does play a role in undigested protein and that can lead to food allergies.",
"However, I think this is just proteins, and just proteins resistant to digestion. Milk can contain some of these proteins that trigger an immune response (hence milk allergies). I'm guessing your dad isn't allergic to milk. However, sun chips aren't going to do this. Also, unless he is having a physical manifestation of an immune response, his energy is not be sapped by his \"immune digestion.\"",
"It is worth pointing out that anybody can claim to be a nutritionist, but it takes an actual degree in dietics to be a registered dietician. If you're dad is concerned about his diet, he should see a dietician."
] |
[
"If babies breathe through the umbilical cord, how do chicks breathe in eggs ?"
] |
[
false
] |
[deleted]
|
[
"It's predominately diffusion across the eggshell.",
"...up to the time when internal pipping takes place, when pulmonary ventilation is initiated, about 20 liters (O2 + CO2 + water vapor) have passed through 10,000 pores of an 80 gm egg.",
"--Pores and gas exchange of avian eggs: a review. Rahn H, Paganelli CV, Ar A. J Exp Zool Suppl. 1987;1:165-72.",
"There's ample gas diffusion across the eggshell during most of the chick's development; the eggshell itself offers little resistance to gas exchange:",
"A typical 60-g chicken egg has about 10,000 pores, each with a functional cross section of 150–200 μm",
" therefore, the total pore area is about 1.5–2 mm",
"--Gas exchange in avian embryos and hatchlings. Jacopo P. Mortola. Comparative Biochemistry and Physiology, Part A 153 (2009) 359–377 ",
"Most of the resistance is from the membranes on the inside of the shell, and this resistance is reduced during development to keep pace with the increased requirements.",
"Very near the end of development, the chick can gain extra air through the air sac (the \"internal pipping\" mentioned above); but note, the air in the air sac also gets there through diffusion through the egg shell, during earlier development. ",
"Chickens have it pretty easy compared to many other avian species. For example, ostrich eggs have a much larger volume-to-surface area, meaning that exchange is less effective. One way ostriches may compensate is by incubating eggs at lower temperatures, reducing oxygen requirements; more significantly and related, incubation time is relatively slower for birds with large eggs. Birds at high altitudes have larger total pore size, adapting to the reduced O2 pressure.",
"Actually, a more serious problem than oxygen exchange is water exchange. The egg needs to manage water loss (not too much, not too little), and the more gas exchange the more water loss. Accordingly, birds adapted to different humidities lay eggs with different gas exchange capacities (changing pore densities for the most part); birds in very arid environments, like gulls in Chile's Atacama Desert, have very low gas and water exchange, to the point where their developing chicks are relatively hypoxic (Reduced oxygen diffusion across the shell of Gray gull (Larus modestus) eggs. Monge CC, Ostojic H, Aguilar R, Cifuentes V. Biol Res. 2000;33(3-4):209-14.)"
] |
[
"It is really cool that you are able to explain why, thank you"
] |
[
"Great explanation. Is it worth making the distinction between breathing using lungs and being supplied with oxygen through the Allantois organ (effectively the umbilical). Same distinction with human babies. They do not ‘breathe’ using their own lungs until post birth. Prior to birth all oxygen is supplied by the mother through the placenta as richly oxygenated blood."
] |
[
"If alien observers detect the earth through the Transit Photometry method, would it be possible for them to realize earth is inhabited due to our artificial lights?"
] |
[
false
] | null |
[
"The limitations and capabilities of astronomic measurements are highly speculative? The signal-noise-ratio of transit detection is speculation? Light occlusion methods such as those already used to detect exoplanets(",
"http://www.eso.org/public/news/eso1024/",
") are speculative future tech of which no one know the limitations of?",
"Are the only questions that are allowed here those whose answer can be found on simple.wikipedia?"
] |
[
"You're asking about the technology, including the sensitivity, of alien observers, which is highly speculative. So is future technology. Current technology is not, and yes, the level of technology definitely determines the limitations and S/N of a transit detection; Kepler has different photometric sensitivity than other telescopes which means it can detect different numbers of exoplanets. I'm saying that if you want to flip the question and ask what our sensitivity is to artificial lights, that's completely fine."
] |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"For more information regarding this and similar issues, please see our ",
"guidelines.",
"If you disagree with this decision, please send a message to the moderators."
] |
[
"How much heat does the moon redirect to earth?"
] |
[
false
] |
For an average distance between the moon and the earth. Is the amount of energy transfer phase dependent? Is it proportional to the level of light received?
|
[
"Doing the math",
" it's about 107 GW. That sounds like a lot, but that's for the whole Earth. For comparison, the Earth gets about ",
"174 PW",
" from the sun directly, which is about 1.6 million times more.",
"Also it does depend on the phase. What I just gave is average. During a full moon you'd get double that, and during a new moon you'd get none.",
"Edit: Come to think of it, the albedo doesn't matter. That just changes whether it's reflected radiation or blackbody radiation we're getting. It still emits just as much as we absorb. Although our greenhouse gases will reflect more of the infrared light. Ignoring the albedo, it's ",
"891 GW",
", and it's a 196,000th of what we get to the sun.",
"Also, someone else brought up solar eclipses, which would block more light than the moon would reflect back. It reflects back based on how much of the sky it fills, but it blocks light with a probability from how much of the zodiac it fills, since that's the part of the sky that the sun and moon travel through."
] |
[
"Does the moon get heat up by the earth? I know there is no atmosphere, but do the surface rocks heat up from the earth radiating heat? If so, how is this affected by climate change/more greenhouse gases"
] |
[
"Yes it is. It makes a bigger difference since the earth is larger than the moon, but it's still pretty tiny. Climate change doesn't do anything. The reason greenhouse gases cause the earth to heat up is that the reflect the infrared light back to the ground. This heats the earth up until it's hot enough that the light that does escape is equal to what it's getting from the sun. If you were to suddenly increase the amount of greenhouse gases, then the earth would radiate less heat for a little while, but it will balance itself out again.",
"Edit: Although I guess it does mean that more of the outgoing light is higher energy, and the moon might reflect more or less of it at that frequency."
] |
[
"Yoga: Are the benefits of yoga scientifically proven? If yes, how did the inventors of yoga make up the asanas and know their benefits?"
] |
[
false
] | null |
[
"Penn and Teller did an episode of Bullshit on yoga. They claim that all of what is modernly known today as 'yoga' in America was invented very recently (I think the 60's) and just artificially tied to ancient stuff to give it credence.",
"Is stretching, strength training using your own body weight, and regular exercise good for you? You bet! Body and mind are known to improve from these conditions.",
"Edit - claims require evidence. I don't have to prove yoga isn't magic.",
"Yoga advocates (including instructors of yoga classes I personally attended) do not merely argue yoga is a good exercise/meditation practice. They claim the asanas and other positions are somehow an enhanced way of doing things. That the breathing and 'finding your center' within these stretches opens up your mind beyond normal self- or guided-meditation and exercise.",
"If you want to argue that yoga ",
" is more than just an analogous exercise routine, that requires evidence."
] |
[
"There's plenty of science related to the health and psychological benefits of exercise in general. Ignoring the meditational aspects of some varieties, yoga is a form of exercise, and as such is going to have benefits. ",
"A google search for \"",
"yoga scientific research",
"\" turns up plenty of specifics about post-hoc research that has been done on the benefits of yoga. ",
"The NIH page",
" summarizes some of that research. That page points out that yoga is comparable to \"other forms of regular exercise\" and \"conventional stretching exercises\", which can have similar benefits to yoga.",
"The development of yoga was not done in any rigorous scientific way, so the claimed benefits of specific asanas should not be taken too seriously if they don't have a sensible rationale - and even then, beware of ",
"just so stories",
" until you've seen at least one scientific study confirming the claimed benefit."
] |
[
"Humans are also romantic creatures, aesthetics is a testament to this. Logic and function is not always the most optimal way in doing this. Making the exercise fit your frame of mind through spiritual mumbo-jumbo enables the function of exercise.",
"So, what I'm trying to say is: It is magical and healing if your romantic view of the world sees it that way. Exercising is healing both for the mind and body and one could call that magical. Magic doesn't always mean meta-world fluff, semantically speaking. The same way as two people falling in love on a beautiful autumns day in New York might be called magical; we still know it's a bunch of chemicals firing off in their brains to cause such resonance in emotion.",
"I often find discussions like these do not incorporate people and perception enough but deal in absolutes and binary rationalization. "
] |
[
"Historically how important have viruses been to our evolution?"
] |
[
false
] |
[deleted]
|
[
"Viruses have played a very important role in all evolution, including human evolution.",
"The figure you mention is likely referring to the large sections of DNA composed of retrovirus-derived repetitive sequences, or transposons. While human transposons have not been active for millennia, they were active in our evolutionary past and their movement (and consequently, their disruption of the genome) was one of the forces driving evolution. Today these repetitive elements serve a structural role in the genome, helping chromosomes arrange themselves correctly in the nucleus and maintaining heterochromatin (tightly packed DNA that does not allow RNA transcription).",
"Humans also have a number of genes derived from viruses, the most notable being RAG1 and RAG2 recombinases, two genes that are absolutely required to generate an adaptive immune system. There are others as well but these two are the most obvious.",
"Finally there is the viral contribution to our evolution as pathogens (causes of disease). All organisms from bacteria on up have defense systems they evolved to fight viruses, the mammalian version being quite elaborate. These defenses are costly - any energy spent on immunity is energy NOT spent on reproduction - so their presence in every genome is the result of constant evolutionary pressure by viruses to develop and maintain them.",
"There are many viruses that are so widespread as to be nearly universal in the human population (mostly herpes family viruses - HHV6, HHV7, Epstein-Barr etc) and resistance to these is definitely something that was selected for in our evolution (for example, we have a receptor that specifically recognizes LCMV).",
"Sorry if this was a little disorganized, its hard to overstate the importance of viruses in the evolution of life on earth."
] |
[
"I don’t think this is a question that we fully have the answer to yet. We do know of a handful of functional Human Endogenous Retroviruses (HERVs) in our genome. Most of them however are negative, being associated with cancer. It’s pretty well established that a handful of HERVs play vital roles in placenta function though (",
"source",
").",
"Edit: also maybe you already know this but I figured I’d mention it just because of how your question is phrased: COVID is not a retrovirus so it can’t integrate into our genome and become a HERV. Only retroviruses like HIV can do this",
"Edit2: because I saw another user post about TEs, I just wanted to clarify that the figure you are referring to was talking about HERVs. HERVs make up 8% of the genome. TEs make up 45-50%."
] |
[
"There is evidence that the mammalian ability to form a placenta comes from viral DNA ",
"https://whyy.org/segments/the-placenta-went-viral-and-protomammals-were-born/#:~:text=Now%2C%20we%20get%20this%20viral,but%20also%20keeps%20them%20separate",
"."
] |
[
"How can I classify mud?"
] |
[
false
] |
Hey I am trying to categorize mud so that what I am working on can meet certain requirements. I know there is a way to classify soil, USCS, but does that change with mud?
|
[
"What does \"Land-Sea Couplings\" research entail?"
] |
[
"What does \"Land-Sea Couplings\" research entail?"
] |
[
"thanks, but do you have any sort of official source for this or is it just how its done/personal experience type of thing?"
] |
[
"when you get sick and recover, is this like your immune system getting \"exercise?\" is it now stronger for the future?"
] |
[
false
] | null |
[
"So basically, vaccines are training simulations for your immune system."
] |
[
"It's like this in a way, but the \"strength\" is only specific to the illness you just suffered from. For example, recovering from one strain of the flu isn't going to give you protection from all forms of the flu, or from illness in general, but it creates immunity (antibodies) against that particular form to prevent against re-infection. The whole system doesn't really become stronger, but a part does (the part that fights the illness you just experienced). It's comparable to doing squats, where your legs specifically are strengthened but the rest of your body isn't really changed."
] |
[
"When you get sick your immune system designs antibodies that learn how to fight off the ailment. This is what a vaccine is for, a weakened version of something the immune system can learn to fight without risking being defeated.",
"In reality I wouldn't say it's exercise to get stronger as much as it's like a military learning a new strategy."
] |
[
"To what degree can we affect our genetics?"
] |
[
false
] |
[deleted]
|
[
"Epigenetics is defined by ",
" changes in gene expression that do not involve changes to/in the actual fundamental sequence of the DNA concerned. There are a number of known molecular mechanisms which govern such changes (e.g. methylation of DNA and various histone modifications). From my knowledge, environmental stimuli can cause ",
" changes to an organisms DNA; effectively genes can become 'silenced' in response to an environmental stimulus. Thus, in theory, an environmental stimulus (i.e. doing more exercise, being exposed to a certain substance, etc.) could cause an epigenetic change, which, could then be inherited in the organism's offspring (as the epigenetic change is maintained and replicated by meiosis to produce gametes). ",
"However, I have no idea how often such significant epigenetic changes occur and the magnitude of stimulus required to produce such a change. Moreover, phenotypic traits are very rarely monogenic (governed by a single gene) and so even if a gene was 'silenced' in an epigenetic sense (by an environmental stimulus), it is unlikely to produce a significant phenotypic change.",
"TL;DR - Possibly!",
"Entry level reading ",
"here",
"EDIT - some more, relevant and interesting links/articles",
" - Jablonka (2009)",
" - Reik & Walter (2001)"
] |
[
"I think that you are confusing genotype (i.e., genetic makeup) with phenotype (expression of those genes). While you can modify your phenotype with diet and exercise, you can't (but, see below) modify your genetic predisposition for that body type in the same way. This is essentially Jean-Baptiste Lamark's theory of evolution that has since been replaced.",
"Think of it this way... if you cut off your left hand, and cut off your wife's left hand, what are the chances that your kids will be born without a left hand? The answer is largely the same in both cases.",
"Having said that, epigenetics is an actively developing field of study, and there may be some epigenetic influences in the case you describe, but I don't know enough about it to say one way or the other."
] |
[
"A reminder here that your family being overweight does not mean you are genetically predisposed to being overweight. It might just be that those families have eating/cooking and (lack of) exercise habits that lead to them gaining weight (or it could be a combination of genetic and environmental factors). In the case of weight, even if it were truly a genetic trait, in most cases how you eat, what you eat, and whether you exercise have a much greater influence over your body weight than the genetic factors (though there are exceptions). You can provide a good example to your children by being in good shape, and that will \"train\" them to do the same, but it won't be genetic. ",
"Others already commented on the confusion between genotype and phenotype, so I'll leave that to be. "
] |
[
"A couple of questions about memory."
] |
[
false
] |
Why do I often recall completely insignificant memories? For instance, I have this memory of when I was a kid, going grocery shopping with my mom, and I happened to run into this other kid with whom I went to school and was only moderately friendly. It was a completely uneventful occurrence, yet it pops into my head a lot. That brings me to my second question: How does the brain decide what information should be stored as a short-term memory versus a long-term memory? Using my previous example, why is that any more important than remembering what I ate for dinner last Tuesday (which I can't)?
|
[
"Memory works by associations. It's really difficult to make any 100% definitive statements here, but this is most likely what happened:",
"Odds are you were surprised to see your neighbor. Surprise at seeing your neighbor (especially if you haven't seen other people you know at the grocery store often before) triggered dopamine release. Yeah, yeah, dopamine is the pleasure neurotransmitter and all that, but it does other things, too. Especially relating to novel or unanticipated events. (One of the reasons why people like trying new things is, not coincidentally, dopamine.)",
"Dopamine is great at helping form memories (if you're looking to learn more about this, type dopamine + ltp into your favorite science search engine). Thus, you formed a memory of a seemingly uninteresting event.",
"Your second question is much more interesting. This is a very, very hotly debated topic in the literature. The generally agreed upon idea is that the more connections a memory has (that is, the more things you associate it with), the more easily recalled it is, and the older a memory is, the more stable it is. A couple candidate proteins play some role in induction of memory formation (CREB, CaMKII) and stabilization (PKMzeta), but at this point, we really have no idea of the specifics of how they work. Pretty much every other Nature Reviews Neuroscience has a review article on this, but I can't find a good open access one to link to at the moment. The view I'm most fond of is that long term and short term memories are the same (long term differing by more PKMz expression and being somewhat more interconnected with other memories leading to easier recall). However, I am not an expert on this subject, and therefore am not to be trusted under any circumstances.",
"One final slightly unrelated bit - no matter how old your memory, every time it is recalled, it needs to be re-encoded (a process requiring protein synthesis) or it will be lost. Stuff like a simple bump on the head (hard enough to knock you out) can destroy not only your short term memories, but any long-term memories you recently recalled (in the last ~2 hours)."
] |
[
"You might see a penny a hundred times but still not know what direction Lincoln faces. You might have your mom yell at you 30 years ago and still remember the look on her face with precise detail.",
"TIL that I have no clue what direction the presidents face on most coins."
] |
[
"I wish I knew the answer to this. I can't remember Birthdays, Holidays (beyond Christmas), or any other important date. I can't remember plans for the weekend that my wife made 3 days ago.",
"However, I can quote damn near every movie I have ever enjoyed watching, and can recall almost every scene in detail. I have a shit-ton of useless knowledge (which makes me fairly good at late-night drunken trivia.) ",
"I can hardly remember ANYTHING I learned in college. Especially the math. I went through Calc 3 and im lucky I can even do basic arithmetic these days."
] |
[
"Would spraying blood-spatter at a crime scene with ammonia (like in Boondock Saints) really ruin any DNA evidence?"
] |
[
false
] |
I've also heard the same mentioned about bleach; would that work as well?
|
[
"Given modern molecular techniques, I don't think the aforementioned Boondock Saints scene would be as accurate as it may have been back then. There are now DNA extraction kits that are specifically designed for old, contaminated, or mishandles samples. These \"forensic kits\" have several wash stages that remove chemicals such as ethanol and ammonia, resulting in fairly decent readings.",
"I've used them in the past to extract DNA from ~125 year old moths who had been subjected to some harsh chemical treatments. We were able to get useful DNA out of it. "
] |
[
"This isn't correct. While the distinction between organic and inorganic can be somewhat arbitrary, the sugar backbone of DNA and the bases are certainly organic.",
"Also there are many inorganic molecules which are quite easily destroyed and likewise some very hardy organic compounds which can persist."
] |
[
"So, does DNA ever \"expire\"? As in, does it ever naturally degrade and stop bearing usable genetic code?"
] |
[
"If sea turtles return to their birth beach, how do the species ever spread to new areas?"
] |
[
false
] |
Every article I can find on sea turtles shows that female sea turtles return to the beach where they were born to lay eggs, most likely through sensing location via the Earth's magnetic field. Yet sea turtles are found the world over, so how do some female turtles find new beaches?
|
[
"This review",
" gives a good overview of the genetic structure of populations of all 7 sea turtle species. Some key relevant points:",
"1) The natal hypothesis of female nest site choice is supported in populations which overlap in overall territory but not in nesting location or genetic markers (see figure 1). However, natal homing is not infallible, as the authors put it:",
"Among the thousands of female sea turtles tagged on the beach, a tiny percentage are observed nesting far outside the range of their previous nesting site (e.g. LeBuff 1974), and mtDNA surveys also indicate occasional nest-site shifts (Reece et al. 2005). These ‘gravid waifs’ are probably essential to the prosperity of sea turtles, as absolute natal homing, over the 100-million-year history of this group, would be a strategy for extinction.",
"2) Juvenile sea turtles form large feeding groups, but don't necessarily stay located offshore of the beach where they were hatched (see figure 2). It's possible that females which don't return to their own hatch site migrate with their feeding group.",
"3) Migration plays a major role in all 7 species, and each species has an ideal habitat, but there is lots of overlap and hybridization, as well as significant gene flow within species (see figure 3). During migration, water flow and temperature can impact destination, quoting again:",
"Ridleys and loggerhead (",
") also show more recent colonization between ocean basins, probably mediated by warm-water gyres that occasionally traverse the frigid upwelling zone in southern Africa."
] |
[
"A common misunderstanding of this and similar phenomena, such as migration, are that ",
" members of the species participate in it in exactly the same way. The majority of the individuals behave this way, but there are almost always some that don't. I'm fairly sure a careful analysis of a large sample of turtles would show that some females visit beaches they've never been to before to lay eggs. "
] |
[
"Thanks!"
] |
[
"Do the calories in fruit increase as they ripen?"
] |
[
false
] | null |
[
"No, not exactly. Fruits tend to taste sweeter as they ripen because ripening is a form of decomposition. The polysaccharides in fruit that represent the energy stored begin to break down into smaller molecules that are easier for our body to break down into glucose meaning less time is needed to digest the fruit. No calories are added or lost and digestion is a mostly passive process so no extra energy is needed or saved."
] |
[
"After I posted this I thought of something. If you place fruit together they ripen faster because of the gases they release. Is it possible that they actually loose calories due to the energy it takes to produce these gases? Do they heat up during this process? But it seems as though, if heat is actually generated, it would be insignificant to a calorie count."
] |
[
"A loss in energy doesn't necessarily equate to a loss in calories. It could be decomposing into a more bioavailable form."
] |
[
"How do you prove that time is a dimension?"
] |
[
false
] |
One of my friends doesn't believe that time is the 4th dimension and I haven't been able to prove him wrong and need some help.
|
[
"Tell him there's a great party you'd like him to join you at, at your friend Bob's. When he asks you when the party is, respond by pointing out that if time isn't a dimension then that question is meaningless. "
] |
[
"I don't think it can be ",
" that time is a dimension. Rather, depending on the model you are using, time either is or is not a dimension. Some models are more accurate than others.",
"Our best model of time is general relativity. In general relativity, it is taken as a postulate that there are 3 dimensions of space and 1 dimension of time, and a \"dimension\" in this sense means a real number that is needed to specify a location. So if we say the universe is 4-dimensional (3+1-dimensional), that means we need 4 coordinates to specify where something is in spacetime (3 space coordinates, x, y, and z, and 1 time coordinate, t).",
"So, in our best model of space and time, time is a dimension by simple postulate. The fact that this model is extremely accurate suggests that time either is a dimension, or it has a structure that makes it effectively equivalent to a dimension. So it can be said that time ",
" a dimension.",
"Also keep in mind that time being \"the fourth dimension\" is not the same as time being a fourth ",
" dimension. A fourth spatial dimension is different from a fourth temporal dimension because of how the mathematics/algebra for determining the distance between things works (called the \"metric\"); a temporal dimension has the opposite sign and also needs a conversion factor (usually the speed of light, c)."
] |
[
"The idea of a dimension is a construct that helps us solve problems. There is nothing to prove.."
] |
[
"Are fighter aircraft noticeably \"weighed-down\" by their armaments?"
] |
[
false
] |
Say a fighter pilot gets into a combat situation, and they end up dropping all their missiles/bombs/etc, how does that affect the performance of the aircraft? Can the jet fly faster or maneuver better without their loaded weaponry? Can a pilot actually "feel" a difference while flying? I guess I'm just interested in payload dynamics as it applies to fighter jets.
|
[
"It's a huge difference. The weight changes the stress on the airframe, and if external the ordnance produces lots of extra drag.",
"For example, a f/a 18 is rated for +7.5g and -3g maneuvers when light, but at full weight only +4.8g and -1.8g.",
"Here are some study cards for an f/a 18: ",
"https://quizlet.com/13297122/fa-18-limts-and-prohibited-maneuvers-flash-cards/"
] |
[
"Also, what's a wingtip launcher rail?"
] |
[
"Wing tip launcher rails are mini-pylons of sorts that are attached to the wingtips of an aircraft. Usually, they hold things like a short range Air to Air missile, like an AIM 9. ",
"Here's one on an F-16",
"As far as to why an F/A-18 can't fly without wingtip launcher rails, I believe they are a permanent attachment to the wing. I can only assume though, never been near that specific airframe. ",
"EDIT: Spelling. "
] |
[
"How does altitude (atmospheric pressure) influences our hearing?"
] |
[
false
] |
Does the difference in atmospheric pressure make a noticeable difference to how we perceive sounds?
|
[
"Assuming the back of your eardrum is the same pressure as the atmospheric pressure (ie, your ears don't need to be popped), then no, the pressure difference doesn't really have an effect on your hearing. This is, of course, assuming that you are at a reasonable pressure where the air is still breathable (not in the vacuum of space).",
"If there is a pressure difference, however, it will effect your hearing, because your eardrum will be pushed away from its equilibrium position where it's most sensitive."
] |
[
"Sound most definitely travels slower at high altitudes/low pressures.",
"Sound travels slower at higher altitudes because of the temperature difference. Sound speed is expressed as c=√(γP/ρ), where γ is the ratio of specific heats (a property of the gas), P is the ambient pressure, and ρ is the density. However, through the ideal gas law we have have that P=ρRT/M, where R is the gas constant, T is temperature, and M is molar mass. Thus, c=√(γRT/M), where γ,R, and M are all constants of the air, so that means that the sound speed is only a function of temperature.",
"This means sound dissipates faster so hearing something at a distance is significantly harder",
"Sound doesn't dissipate as a function of sound speed. It's almost entirely determined on energy spreading, which is determined by distance from the source, along with absorption by the medium (which is primarily a function of distance and frequency)."
] |
[
"Sound most definitely travels slower at high altitudes/low pressures. This means sound dissipates faster so hearing something at a distance is significantly harder"
] |
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