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[
"How can cows just eat grass when we need a balanced diet?"
] |
[
false
] | null |
[
"Well not all fermentation produces ethanol. Fermentation essentially refers to metabolism that occurs without oxygen. Not all species produce ethanol when they do this. According to Wikipedia the microbe community inside a rumen produces mostly volatile fatty acids which are absorbed as a source of nutrients, as well as a lot of gasses like methane which are released as cow farts. "
] |
[
"Could you then tell what is a proper diet for a dairy cow? Or a good source on that?"
] |
[
"Could you then tell what is a proper diet for a dairy cow? Or a good source on that?"
] |
[
"When observing an isotope over it's half-life, what determines which half deteriorates? Is it always exact? How?"
] |
[
false
] |
Isotopes have always evaded me as far as understanding. How do we understand this half-life concept so definitively that we can use it for so much?
|
[
"Atoms of a radioactive substance decay at ",
". There is no way to predict when any particular atom will decay.",
"That being said, there are some things you can say. If you have an atom you might expect it to take \"a long time\" to decay or maybe \"just a few seconds\". This is an informal way of expressing that while each decay is random, the probability of decay within any finite time interval is predictable. More unstable isotopes decay more quickly, and are thus more likely to decay after a given amount of time.",
"One way of expressing this idea is half-life. This takes advantage of the fact that any macroscopic piece of material has a massive (~10",
" number of atoms in it. Therefore, any probability for a decay gets averaged over all of the atoms. If each atom has a 50% chance of decaying during some finite time interval, then if you take a bunch of atoms, you can expect that 50% of them will decay during that interval, because of the law of large numbers. We call that time interval the half-life.",
"Its like how the outcome of any given coin flip is random, but if you flip enough coins all at once, you can expect half of them to be heads and half tails. The large number exposes the average probability."
] |
[
"Exactly. The secret lies in the great numbers. Most people fail to grasp the sheer amount of atoms in a tiny portion of matter. It makes understanding and more so handling nuclear physics really difficult."
] |
[
"Its not that it breaks down, as the smaller numbers means that instead of measuring number to a good approximation, it just shows the underlying physics that it's the expectation value that an atom will still exist after some time. The quantum nature of the nucleus transitioning to another state is where the randomness ultimately comes from."
] |
[
"Why do many humans have involuntary physical reactions to being tickled?"
] |
[
false
] |
Is the response to being tickled something that was evolved for a reason? My best guess is that it could alert us to creatures touching our skin or something like that.
|
[
"wiki on tickling",
" does a good job with this, stating that one of the 2 types of \"tickling\" called Knismesis (the irritating kind that doesn't make you laugh) is often elicited by insects..",
"My favorite line from it: \"Heinz Heger, a homosexual man persecuted in the Flossenburg concentration camp during World War II, witnessed nazi prison guards perform tickle torture on a fellow inmate, followed by various other tortures which resulted in his death\"",
"the picture of nazis tickling a guy to death is just so wrong;)"
] |
[
"He contributed a perfectly valid idea and admitted that he wasn't sure if it was true. I don't understand why that deserves to be downvoted so much. "
] |
[
"He contributed a perfectly valid idea and admitted that he wasn't sure if it was true. I don't understand why that deserves to be downvoted so much. "
] |
[
"Some nightmares feel so real they leave you feeling traumatized, why would a brain traumatize itself?"
] |
[
false
] | null |
[
"What I've always been fascinated with, and had a hard time wrapping my head around, is similar to the question posted. How is the brain able to create an environment where it is both the actor and the creator, and yet devoid of that knowledge. That is to say, in a dream, you are creating the environment, but also participating in that environment and completely surprised by what occurs within. How? Is there some sort of modular separation of experience that takes place allowing this to be possible?"
] |
[
"How does the evidence stack up for dreams as training simulator for possible situations, vs dreams as random noise being interpreted as images and sensations? Claims like this always strike me as \"ad hoc\" or \"just so\" claims. Its possible dreams have little or no impact on genetic selection and it's really just random noise. "
] |
[
"How does the evidence stack up for dreams as training simulator for possible situations, vs dreams as random noise being interpreted as images and sensations? Claims like this always strike me as \"ad hoc\" or \"just so\" claims. Its possible dreams have little or no impact on genetic selection and it's really just random noise. "
] |
[
"Is it possible to define electric charge in an absolute (non relative) sense?"
] |
[
false
] |
A positive charge is the opposite of a negative charge. But is it possible to define one without referring to the other, or they solely relative terms? A book I am reading claims it is not possible, and as a consequence the two charges could in theory swap throughout the entire universe, and nothing would be observed as different. It sounds very odd and i was wondering if the basis is true.
|
[
"For most purposes, you could swap the charges and everything will be the same. This is known as ",
"C-symmetry",
". But it's not perfect. The weak force violates C-symmetry. In order to get it to work right, you also have to mirror everything and swap the direction of time. This is known as ",
"CPT-symmetry",
".",
"You still have to define it in a relative sense, but not purely relative to other charges. If you know what direction time is going in, you can specify which charge is positive and which is negative."
] |
[
"This is the correct answer, just to clarify a bit some possible confusions. ",
"Which charge you decide to call negative and which you decide to call positive is completely a matter of convention.",
"But, once you have made the choice you cannot freely swap them arbitrarily because our universe is not entirely symmetric under C-symmetry. Our universe is symmetric as pointed above under CPT; if you run the evolution of the universe backwards, change left and right, up and down, front and back... then you can swap positive charges with negative charges and everything looks exactly the same as it does right now at a microscopic level."
] |
[
"The definition of one charge as negative and the other is positive is completely arbitrary. We could just as easily have defined the electron as having a positive charge and still be able to describe the same physics with the same math.",
"The swapping of positive and negative particles is definitely possible without any physical consequence, as evidenced by the creation of ",
"antimatter atoms",
".",
"The sign is arbitrary, but the proton charge is definitely the opposite of an electron charge whatever sign convention you choose.",
"Regardless of sign, we could still specify an electron's absolute charge because it is a charge relative to zero charge. We say that the electron charge is a fundamental ",
"physical constant",
" because it is universal and is constant in time."
] |
[
"Why does the sunset appear blue on Mars?"
] |
[
false
] | null |
[
"I think that he was talking about real (not white balanced) Martian sunsets from Curiosity. Examples include ",
"this",
" and ",
"this",
".",
"There's an explanation in the page.",
"Mark Lemmon, of Texas A&M University, College Station, the Curiosity science-team member who planned the observations, said: \"The colors come from the fact that the very fine dust is the right size so that blue light penetrates the atmosphere slightly more efficiently.",
"\"When the blue light scatters off the dust, it stays closer to the direction of the sun than light of other colors does. The rest of the sky is yellow to orange, as yellow and red light scatter all over the sky instead of being absorbed or staying close to the sun.\""
] |
[
"You have a picture? It might be color manipulation and not true color. For instance, here's Curiosity's view of Mount Sharp: ",
"Raw color: ",
"http://photojournal.jpl.nasa.gov/jpeg/PIA16769.jpg",
" ",
"White balanced: ",
"http://photojournal.jpl.nasa.gov/jpeg/PIA16768.jpg",
" ",
"The second image tries to recreate Earth lighting conditions which makes it easier for people to pick out features in a landscape colored in a way they are used to versus an alien world. ",
"http://photojournal.jpl.nasa.gov/catalog/PIA16768",
"This mosaic of images from the Mast Camera (Mastcam) on NASA's Mars rover Curiosity shows Mount Sharp in a white-balanced color adjustment that makes the sky look overly blue but shows the terrain as if under Earth-like lighting. White-balancing helps scientists recognize rock materials based on their experience looking at rocks on Earth. The Martian sky would look more of a butterscotch color to the human eye. White balancing yields an overly blue hue in images that have very little blue information, such as Martian landscapes, because the white balancing tends to overcompensate for the low inherent blue content."
] |
[
"You appear to have linked to the same picture (same URL) for both the raw colour and white balanced images."
] |
[
"What does it mean to be tidal locked to something?"
] |
[
false
] |
I am under the understanding that the moon is tidaly locked to earth, what does that mean and why has this arisen?
|
[
"Tidal locking means that the same face of the Moon always points toward Earth.",
"This occurs because tidal forces--the difference in gravitational tug from the Earth between different parts of the Moon-- cause small distortions and stretches in the shape of the Moon. These distortions dissipate the moon's rotational energy, slowing its rotation until eventually ",
" its rotational period is equal to its orbital period."
] |
[
"Longer than the Sun's lifetime. We'll be toasted to a crisp before that has time to happen."
] |
[
"Earth's day used to be about 6 hours. Wouldn't the moon be more responsible for this than the sun though? "
] |
[
"What is the geographical causes for long, thin stretches of land offshore from mainland areas? For example, Outerbanks, NC, Longboat Key, FL, or Pensacola Beach, FL?"
] |
[
false
] | null |
[
"These are barrier islands, basically a large sandbar. A number of theories for their formation can be found in Wikipedia. A combination of tides, wave action and the effects of glaciers are the main mechanisms forming barrier islands"
] |
[
"Waves, tides, and storms deposit sand and silt near shore that eventually builds up into these barrier islands, that then get colonized by plants, birds, and other life, which increases their physical stability. Not they do routinely get wiped out by particularly heavy storms; responsible governments pay dredging ships to rebuild the sandbars, which will hopefully become barrier islands in the future."
] |
[
"The outer banks (and similar islands up to coast to Cape Cod) are barrier islands. Waves act to push coastal sediment coming out of river estuaries into berms along the beach, and then storms have flooded and eroded out the flat plains behind these berms.",
"The Florida Keys are formed from barrier reefs. A coastal reef formed there during a period of lower sea level, and as sea levels rose the coral kept building up the reef. Similar to barrier islands, waves have then pushed sand up onto these reefs."
] |
[
"How does the renal HCO3- reabsorption increase blood pH?"
] |
[
false
] |
Hello, this thing is completely destroying my brain. HCO3- in renal tubules is "reabsorved" into the circulatory system through a bunch of reactions involving the carbonic anhydrase. Basically: - It combines with H+ forming CO2 + H2O, that can enter the tubular cells; - The reverse reaction happens inside these cells: forming HCO3- + H+. The HCO3- is reabsorved into the blood, and the H+ goes back to the renal tubules to restart the cycle with another HCO3-. I dont get how this is supposed to eliminate H+. Isn't the H+ net equal to 0 ? Also, how does this make the pH higher? If it reabsorbs the HCO3-, then the H+ used wont be eliminated and vice versa, so I don't see how any of these actions (one or another) could make the pH higher. Sorry if it is confusing and thank you.
|
[
"Your body secretes H+ and HCO3- through the kidneys. They combine to form H2CO3 (carbonic acid). An enzyme, carbonic anhydrase, splits the carbonic acid into H2O and CO2 in the renal tubular lumen and this water and carbon dioxide enter the renal tubular cell passively. This is because carbon dioxide is lipid soluble and can easily pass through the cell membrane. Water can also move easily across the cell membrane. ",
"Once the H2O and CO2 are inside the renal tubular cell, carbonic anyhydrase acts on them again to form carbonic acid. This carbonic acid splits into H+ and HCO3- again. Now the H+ ion is excreted from the renal tubular cell through a ion exchanger known as the Na-H exchanger where the H+ is exchanged for Na+ in the renal tubular lumen. ",
"Thus, the same H+ ion is used for reabsorption of HCO3- and Na+. ",
"I hope this helps."
] |
[
"This",
" picture can be helpful"
] |
[
"It doesn't directly eliminate H",
" from the body. As you said, there is net zero transport of H",
" Instead, a base (bicarbonate) is reabsorbed into the body.",
"You should not believe that every bicarbonate ion actually reacts with an H",
" ion -- there is a complex buffered equilibrium. But each reabsorbed bicarbonate shifts that equilibrium slightly toward the alkaline side, because it has the capacity to accept an H"
] |
[
"Where does the logic of DNA codons come from?"
] |
[
false
] |
I was talking to a friend recently who is studying to be a microbiology major. She was showing me some of her material regarding genetic code. Her homework was to explain a line of genetic proteins. The page looked like a series of ATCG in what looked to me to be totally random order. She showed me how she broke down the code into blocks of 3 which corresponded to 64 codons. My understanding was that the codons form some sort of "letters" to be used in genetic code. I understand the basics of the proteins that make up DNA, but the codons baffle me. My question is, where did the underlying logic behind these codons come from? I somewhat understand how the codons form letters, but how do those letters create something such as skin or hair color? I tried Google and most of the explanations were religious or attempting to disprove evolution. I'm not interested in that, but I have to admit I'm at a total loss to explain how series of proteins form letters which then become a sort of language of life. Forgive me if my terminology or understanding is off. I'm definitely a layman when it comes to biology, but I like to learn. Just curious about life. Thanks for taking the time to read this.
|
[
"Lets say there is a stretch of DNA that is 306 bases long, Those 306 bases can me read over into a 306 base-length strand of mRNA, made up of 1 'start' codon, 100 'letter' codons, and 1 'stop' codon. As you correctly stated, each 'letter; codon corresponds to a specific ",
". Amino acids are the building blocks of proteins. As the mRNA is read by the ribosome, a long chain of 100 amino acids will be formed. The specific order and content of this chain causes it to fold up in a very precise manner. Hydrophobicity and hydrophilicity as well as ionic charges dictate this process. In the end, you have a 3-D structure made up of amino acids which is your new functional protein. ",
"The codons are conserved throughout all organisms that use DNA, which indicates this 'language' developed almost at the same time as did the genetic material. This makes sense if you think about it like this: Words and language couldn't exist if words didn't have specific meanings. If the letters D-O-G mean a 4-legged canine to me but they mean a 2-legged primate to someone else the word 'dog' is meaningless. ",
"The genes that are carried in DNA determine the types and order of the codons, which in turn determine the types and order of amino acids, which in turn determine the size and shape of the protein, which in turn determines how that protein behaves and functions. Different eye/skin colors are based on differences in the genetic code that cause differences in the codons, amino acids, and ultimately proteins. ",
"I think the conservation of the genetic code is elegant proof of evolution, and the fact that we all are related. Divergences in genetics are how evolutionary biologists determine how closely related 2 species are, and they are able to calculate approximately how long ago the 2 species diverged from a common ancestor. "
] |
[
"You have things slightly backwards. DNA is made up of nucleotides (the A, T, C, G) which are the letters you see when you read DNA. A codon is simply 3 of these letters grouped together. This is because the RNA polymerase reads in blocks of 3, and each block of three codes for an amino acid that will be added next to the protein (although start and stop codons are used to start and stop transcription).",
"So basically, DNA has genes which consist of codons that produce specific proteins depending on what amino acids the codons specify. In your question about skin colour it is tied into the protein melanin, the different types of it (e.g. pheomelanin and eumelanin), and different codon sequences which say which form of the protein is made. In cases like eye colour, the genes code for different ",
" of melanin."
] |
[
"To add to baloo's answer:",
"Codons are read as sets of 3 nucleotides by the ribosome through the use of tRNAs. The ribosome doesn't read DNA, just mRNA (messenger RNA). A tRNA is a specific family of RNA molecule that has an amino acid attached at one end of the RNA. It stands for \"transfer\" RNA because it gets used by the ribosome to transfer the amino acid from the tRNA to the growing protein chain. The way it does this is through the matching of 3 key nucleotides on the tRNA to the 3 nucleotides of each codon in the mRNA. If the codon in the mRNA is CCC, the corresponding tRNA sequence needs to be GGG. The 3 nucleotides on the tRNA are called the \"anti-codon\". During the matching process, the third base of the codon/anti-codon isn't actually very important, leading to a phenomenon called ",
"codon degeneracy",
" which is just a fancy way of saying some codons with the same 1st and 2nd nucleotides but different 3rd nucleotides represent the same amino acid. There's a nice chart on that wiki page showing which codons match which amino acids. \"N\" is a lot like A, T, C, or G, except it stands for \"any of those 4 bases\".",
"Also, because codons are sets of 3 nucleotides in a DNA sequence, a single sequence of ATCGs can code for ",
". The sequence CCCGGGCCCGGGCCCGGG is broken up into the codons ",
"CCC - GGG - AAG - GGG - CCC - GGG ",
"which stands for the amino acids ",
"Proline (Pro) - Glycine (Gly) - Lysine - Gly - Pro - Gly. ",
"BUT, if we start counting at the second C instead of the first C, the codons end up as such:",
"C - CCG - GGA - AGG - GGC - CCG - GG",
"The first and last sets are not of 3 nucleotides, so they can't be considered codons. This new sequence codes for:",
"Pro - Gly - Arginine - Gly - Pro",
"Note that because of codon degeneracy, most of the amino acid identities didn't change. GGG and GGA both code for Gly, CCA and CCC both code for Pro. But now, instead of Lysine, we have Arginine (AGG instead of AAG)."
] |
[
"Can undersea cables undergo creep rupture?"
] |
[
false
] |
The pressure down there must be quite high. Is there any proof that undersea cables have undergone creep?
|
[
"Submarine cables used to fail for lots of reasons. Modern ones fail for three reasons: manufacturing defects at joints, dragging anchors close to shore, and deliberate interference.",
"In modern material terms the pressures involved are not that impressive. Transocean cables are laid at around 3-4km depths, which is only 400atm pressure. Yes, that's a squeeze, but it's a long, thin, solid structure. The external pressure is applied uniformly along the cable, so creep is not an issue.",
"Modern (laid in the last 15 years) cables are capable of operating for many decades unless cut accidentally or deliberately."
] |
[
"This is my new favorite qualifier, \"as an engineer completely unqualified in this area\" definitely going to use this someday"
] |
[
"This is my new favorite qualifier, \"as an engineer completely unqualified in this area\" definitely going to use this someday"
] |
[
"Why does COVID-19 seem to have so many more variants than other pandemic-inducing pathogens?"
] |
[
false
] |
To clarify, the title is merely my perception of the situation, not an assertion of fact! Basically it feels like compared to other pandemics in history, such as Spanish flu, the pandemic resulting from this particular coronavirus has included many more variants and possibly is more long lasting. My guess is that compared to former pandemics, we are simply a lot better at identifying new variants, so prior similar episodes were lumped into one single pathogen? As for the longevity, it may be because we're actually a lot better at preventing death and spread than in previous pandemics, there are more uninfected people for a longer period of time leaving them open to infection for longer? These are just some of my guesses, but i'm curious if my perception is just simply incorrect or if not, what the actual reasons are behind these phenomena.
|
[
"Because this is the first pandemic in the era of rapid genome sequencing. Previous pandemics had lots of variants as well, but even during the most recent pandemic, 2009/10, rapid genome sequencing was just getting started."
] |
[
"This is really the correct answer. It’s not just that the technology exists, but it’s also relatively inexpensive, widely available, and automated.",
"This is the first pandemic where we could identify strains precisely at their genetic level and observe the movement and evolution of virus in real time."
] |
[
"Also because there are so many cases, this virus is gettig more play than most viruses, it's a numbers game on the mutations.",
"But covid actually has a double proof reading function and is less liable to mutate than other viruses like influenza, but if you get tens of millions of cases, hundreds of millions, and infect numerous species with it, it will happen."
] |
[
"Does soap/detergent \"clean\" or does it just lower the surface tension of water?"
] |
[
false
] |
I read that warm water cleans better because it has a lower surface tension. Essentially making it a better "wetting agent" allowing water to get into the pours and fissures more easily. I went on to read that detergents lower the surface tension of water. Wondering if soap/detergent actually does anything in the way of cleaning besides lowering the surface tension, or if it's just all the act of the water?
|
[
"Detergents are a type of molecule that is amphiphilic, meaning it is partly hydrophilic (water seeking and polar) and partly hydrophobic (water repelling and non-polar). This allows polar and non-polar substances like oil and water to mix. From a practical standpoint, using detergent in water just allows that mixture to dissolve oils from whatever you are cleaning, whether it's lasagna from a dish or oil from your skin. "
] |
[
"To add to this: effectively, one end of the molecule will be attracted to the food, and the other end to the water. So it sort of pulls some molecules of the food away from the bulk and into the water."
] |
[
"In most cases you're not speeding up any kind of dissolution with soap; it basically just enables two things to mix that normally will not. If you have oil stuck on a dish, you can blast some off with water, but this is really just a physical process. Soap will allow the oil to dissolve (well, emulsify) in the water so that it can be easily washed away. "
] |
[
"Angular Momentum vs. Linear Momentum"
] |
[
false
] |
Say I am flipping a coin, from all the energy and force input into the coin from my finger, what determines how much energy goes into linear motion and how much goes into rotational motion. To simplify, here's an example problem: Say I have a rod of length L, and has a mass of M (that is evenly distributed along the rod). Say at a distance D from the end of the rod, I apply a force F on the rod at an angle of 90 degrees (so perpendicular to the rod pushing at the rod), for a time of T. Now I have the change in momentum (impulse) from F*T, at the point on the rod. But how can I tell how much of the momentum is angular and how much is linear?
|
[
" change momentum, ",
" change angular momentum. Just because the contact between your finger and the coin is applying both does not mean it somehow has to distribute between the two: they are different things.",
"EDIT: I think that the problem is that your intuition that you have to divide what you're doing into two momentums isn't true for impulse and momentum. What your intuition applies to is that the ",
" done by your finger has to be divided between the two ",
". Linear and angular momentum are not the same thing, they're not \"different kinds of momentum,\" they are different things entirely. There's no way to add linear and angular momentum. BUT rotational and translational ",
" are both kinds of energy, so you need to reconcile how the energy gets divided up. ",
"What you find in that case is that a force applied for the same time near the center of mass will act over a ",
" than a force applied at the edge. The force at the edge acts over a larger distance, therefore doing more work, and this extra work goes into the rotational energy."
] |
[
"And yet, his is perfectly legit."
] |
[
"Awesome! I understood that. I'll have to look into the math myself to work it out a bit, but I think I get it."
] |
[
"We toss and turn in our sleep. Why don't we fall out of bed (more often)?"
] |
[
false
] |
[deleted]
|
[
"Knowing where you are is as much a subconscious process as it is a conscious process. The brain stops you from falling out of bed the same way it prevents you from falling out of a chair when you stop paying attention. ",
"Here's a deeper explanation from a sleep expert \n",
"https://m.youtube.com/watch?v=FIZA5IZwe6g"
] |
[
"During sleep, the brain cycles between deep sleep and relatively shallow REM-sleep states during whoch we dream, and sometimes even form memories we can recall later. We are only physically active “tossing and turning” during shallow sleep phases and lie quite still during deep sleep. Also, never mind the movement - REM sleep is still a restful state.\nRemember that our immediate ancestors were tree dwellers who regularly went to sleep over a precarious drop. Our brains are very good producing a restful sleep without going over the edge. "
] |
[
"So does this mean we never rest fully and deeply as part of us is always awake and on guard!?"
] |
[
"How does the body deal with ingested protein?"
] |
[
false
] |
[deleted]
|
[
"You are correct in your guess that it breaks them down into amino acids. Some are essential and must be part of our diet and the rest we can synthesize ourselves. The number of essential vs. nonessential keeps changing, but I believe we are up to 11 nonessential and 11 essential. "
] |
[
"So I guess my secondary question is: Could we just drink a solution of amino acids? Or even just short polypeptide chains? I mean I feel like the answer is yes, but maybe I'm overlooking something."
] |
[
"Or does it keep them intact and direct them where they need to go? ",
"This has two problems: ",
"There is a tight barrier of epthelial cells between the contents of the gut and the body proper. Otherwise the body would be awash in bacteria.",
"The foreign proteins would cause all sorts of trouble. Foreign proteins make the immune system go berserk. Also, you don't want enzymes to do their thing in the wrong place."
] |
[
"How do children who haven't learned to speak yet think? How do animals and small children think without language?"
] |
[
false
] | null |
[
"In reading \"the dragons of eden\" by the late great Carl Sagan he said that it may be fairly similar to the way you think in a dream state. While dreaming, though you may not have noticed, you usually can't read or do math. Even though you may recognise a stop sign, you probably will not be able to read the word. This is because only certain parts of your brain function while dreaming, rendering you unable to use reasoning, atleast not to the extent you normally can. Even though you can still use language in a dream, atleast most people can, the way you think in a dream is about the closest to the way a baby, or even a dog or other mammal, percieves the world.",
"P.s. read every Carl Sagan book you can get your hands on and he will turn you into a better human... For sure."
] |
[
"I think they think in impulses. ",
"it's hard to wrap your head around now, but imagine this scenario: have you ever done anything without thinking about it? Some kind of task that you've done enough, you could almost do it in your sleep? What is your thought process during those moments? Mostly empty, right? With some impulses? ",
"You 'think' without language all the time, but just don't notice because it's so natural. The moment you think back on your thought process, you end up putting it into words but during the actual moment, you may not have thought any words at all. Just impulse.",
"Does that make sense? "
] |
[
"Think of it like getting bored with Reddit, and then opening up another tab of Reddit. You do that without thinking, and then you're like \"wtf\". You opened it because you're so used to getting bored on something else and going to Reddit that you do it in this instance."
] |
[
"How can hospitals check to see that operating rooms are sterile?"
] |
[
false
] |
Alternatively, how do we check to see how sterile a room is?
|
[
"As someone who works in the OR, I just wanted to mention this is the only correct answer in this thread."
] |
[
"As someone who works in the OR, I just wanted to mention this is the only correct answer in this thread."
] |
[
"They gas hospital rooms to sterilize them? Do you know what gas is used? "
] |
[
"Has the Earth always rotated on a 24 hour cycle and revolved around the Sun in 1 year?"
] |
[
false
] |
was there a time when it rotated/revolved faster/slower?
|
[
"I stand corrected. Thank you for the information, and I withdraw my previous comment."
] |
[
"There are tidal rhythmites in Utah that show that the Earth used to have ",
" an 18 hour day, 750 million years ago"
] |
[
"Tidal Acceleration",
" and geologic history beg to differ"
] |
[
"Roughly speaking, is salt evenly distributed in ocean water?"
] |
[
false
] |
Disregarding things like salt stuck in rocks at the bottom of the ocean. Thank you for replying.
|
[
"I would disagree with the previous two posters. The salinity of the ocean at the surface, shown ",
"here",
", is not uniformly distributed. The average salinity is 35 PSU (which means that each 1000 grams of water contains 35 grams of salt). The variation is about from 31 PSU to 39 PSU, which is a percentage variation of 11.4% in either direction. (Note that is a variation across the entire planet. At a given location, the local salinity deviates from the average in very tiny amounts.)",
"Local salinity is affected by many factors, including rainfall, evaporation, and temperature. Even small variations are important in determining the dynamics of ocean surface currents. To give you an idea, the thermodynamics of an ideal gas are described by temperature, density, and pressure. The same goes for seawater, except salinity can have an effect comparative to that of temperature, density, and pressure. So salinity is taken as a basic thermodynamic variable.",
"edit: Some of what I wrote above holds true for any depth. (\"Surface seawater\" means to a depth of about 500 meters.) However, the average salinity is not constant with depth. After about 500 meters (or even sooner in some parts of the ocean), we observe a so-called ",
"\"halocline\"",
". The (average) salinity of the water rapidly changes and then becomes constant with depth. Although at the surface, salinity can range from 31 PSU to 39 PSU across the globe, the salinity in deep ocean water has a much smaller range. Across the planet, deep ocean water has a salinity from 34 PSU to 35 PSU. (Again, there are tiny deviations in the local average, which affect the dynamics of the currents.)",
"Salinity at the surface has such a higher variation because of rainfall, evaporation at the surface, runoff from freshwater rivers, and surface temperatures (higher temps in the tropics means more evaporation, which means more salt). These factors are nonexistent in deep ocean water. So the salinity is pretty much 35 PSU across the planet in deep ocean water."
] |
[
", salt is uniformly distributed in the world's ocean. ",
"/u/grapheneman",
"'s answer is basically correct but they were unfortunately downvoted. Yes there are also variations in salt but they are relatively small. Mean salinity is 35‰ and probably about 98% of the ocean by volume is between 34‰ - 36‰. There are more extreme salinities but they don't account for much of the volume of the ocean. In addition to the uniformity of total salinity, the components of salinity (sodium, potassium, chloride, etc....) are also remarkably uniform around the globe - the \"Law of Constant Relative Proportions” sometimes referred to as ",
".",
"Now, even though the salinity is nearly uniform, the small variations that do exist are immensely important and entire careers are devoted to understanding why the salinity patterns are they way they are. Variations in salinty effect the density of sea water and so, have a role in the overturning thermohaline circulation of the ocean. Also, since salinity is altered by additional/removal of freshwater, studying salinity in the ocean is one way to estimate the global patterns of rainfall and evaporation. Over much of the globe in regions where weather stations are sparse, it is the measurements of ocean salinity which provide the best measure of net rainfall. ",
"Two large oceanographic projects underway now, the ",
"Argo program",
" and ",
"Aquarius mission",
" are both motivated by the need to better understand the global distribution of salinity and the factors controlling it."
] |
[
"Yes! Sound waves are just pressure waves, and pressure is a function (mostly) of the local density, which can be changed by changing the temperature or salinity."
] |
[
"How much heat (if any) reaches the surface of the Earth from the mantle?"
] |
[
false
] |
Besides volcanoes and vents, is there any heat reaching the Earth's surface through conduction?
|
[
"You bet it does. Not at lot, but yes.",
"Heat flows outward from the earth's core and mantle, ultimately to radiate out to space, in exactly the same way heat flows out of a bowl of hot oatmeal. ",
"This effect was used in the Apollo program",
" to assess the rate of heat flow out of the moon's core, as a way to estimate the levels of radioactive isotope decay and composition of the moon's core.",
"The above-linked page cites that the moon loses about 21 milliwatts per m",
" through this process, compared to the Earth's heat-flow losses of 87 mW/m",
"To put that in perspective: The total energy Earth radiates away over an average patch of ground 26 meters on a side, is equivalent to the amount of energy needed to power a 60 watt lightbulb."
] |
[
"Wouldn't ",
" of the heat reach the surface? If the Earth's temperature is stable the heat must be flowing out as fast as it is produced, no?"
] |
[
"Wouldn't all of the heat reach the surface?",
"Yes, but not all at once. The surface can radiate its heat away to space pretty easily, but is supplied with more heat from below. Still, eventually all of that heat will dissipate, at which point the earth will freeze solid, we'll lose our magnetic field, solar wind will strip the earth of its atmosphere, et cetera.",
"Remember, though, planets are ",
", and the time it takes for an object to reach thermal equilibrium with its surroundings is very non-linear with the size of the object. Big objects cool down a lot slower than little ones.",
"Earth is working off of the primordial heat of its formation, plus heat generated by radioactive decay of various elements in the core. When the earth was younger--and hotter--it radiated a lot more than 87 mW/m",
" The cooler it gets, the slower it will radiate. 87 mW/m",
" is just where we're at right now. Ask again in a billion years, and it'll be a lot less.",
"If the Earth's temperature is stable the heat must be flowing out as fast as it is produced, no?",
"Yes. You are absolutely correct. However, the earth's temperature is ",
" in fact stable. It is decreasing, just so slowly we don't notice.",
"When the earth formed, it was a ball of ",
" rock at metal. It took a few hundred million years for it to cool off enough for a crust to form. A few hundred more for temperatures to cool enough where water (from comets, we think, but that's still kind of a mystery) could start to condense out of the primordial atmosphere. Imagine how long it must have taken, once the rains began to fall, for all of that water to come out and form the oceans. Imagine a colossal, more-than-monsoon-force rain, falling all over the whole world, for maybe a million years steady.",
"But I digress. The earth's temperature is not stable. If it was, then yes, that would mean some amount of heat was being supplied internally to balance what was being lost to space. But as far as I know, the amount of radioactive decay heating going on in the core is less than 87mW/m",
" * (surface area of the earth).",
"We're still cooling down, and will eventually freeze solid. You know, unless the red-giant sun swallows the planet first..."
] |
[
"Psychologists! If someone were assigned to periodically check-in on the progress of a chronic procrastinator's task, would it help them toward accomplishing their task?"
] |
[
false
] |
This idea came from a conversation between my wife, who is a very motivated/on-task person, and myself, a lifelong procrastinator. I hypothesized that if I informed someone of my desired task and the time/date to accomplish it, and I instructed them to occasionally check in on me for any measurable progress, this might act as a motivator for me to stay focused on said task. Initially I thought this wouldn't work based on the experience of living with my parents. Growing up, they'd often remind me of all the things I didn't want to do ("Have you done your homework?", "Have you cleaned your room?", "When are going to mow the lawn?"). However, the scenario I am presenting assumes the procrastinator to accomplish the task, and to be reminded and account for his/her progress. Would this work? Would it be sustainable?
|
[
"Checking up on progress is only one part of a reasonable solution... The next step is positive reinforcement any and all progress. Procrastination can be conceptualized as a negatively reinforced cycle. First, you start working on a task, or just think about starting, which leads to some sort of negative emotion - stress, anxiety, feeling overwhelmed, etc. Turning away from the task (procrastinating) removes that feeling. Since procrastinating does a good job of immediately removing that negative feeling, you are more likely to do it again until it becomes a habit or reflexive response. To clarify the reinforcement language: negative reinforcement means that something is removed or ",
" (the negative emotional state), which makes is more likely that the behavior (procrastination) will happen again - this is the reinforcement of the behavior. Shaping, or positive reinforcement of every step that brings you closer to your desired state (productivity), is a pretty common way to break the learned cycle of procrastination. Breaking down a task into small pieces helps here. Checking up, if done incorrectly, could simply result in punishment for procrastination (disappointment, possibly verbally expressed), and we know that punishment is not as effective as positive reinforcement for creating behavior change. It might even just add to the negative emotional state that drives the procrastination. So your wife should be careful about how she responds when she checks up on you to avoid punishment. You might have several ideas about what might be positively reinforcing, which is good, but the real test is whether her response has the effect of increasing the frequency of the desired behavior."
] |
[
"Wow! I was not expecting a response to this, so thank you very much for doing so. I appreciate the detail you've gone into as well. From what it sounds like, positive reinforcement is absolutely key here in order to make any changes.",
"I did have one other factor to throw into this scenario that may or may not completely screw up any hope of help. What if this person checking up on me was a complete stranger who I asked to check up on me? I obviously have much less accountability to a stranger than to my wife. I know it's an odd scenario."
] |
[
"I think the effect from a previously unknown person would be much less than someone you know and expect to see again."
] |
[
"How would a helium balloon behave in a pressurized zero G environment?"
] |
[
false
] |
my guesses are it would either float towards the middle of the room or behave like a generic rock would in zero g. Also, if a spaceship were to accelerate and cause artificial gravity, would the balloon move contra the direction of gravity?
|
[
"Helium balloons float on Earth's surface because they are less dense than the air that would be occupying that space. Earth's gravity pulls all objects (including air and balloons) downward, but since the air weighs more, it fills that space and pushes the balloon upwards.",
"In zero G, zero net acceleration environments (a shuttle or space station in a stable orbit, for example) neither the air nor the balloon has any weight, since weight is simply the force applied to mass by gravity. Thus, the effects of density we experience on Earth's surface disappear, and the balloon simply floats around weightless like any other object.",
"For your second question, I'm not sure exactly what you mean by artificial gravity, but I'm going to assume you are referring to the resistance all objects feel when being accelerated (",
"inertia",
"). Lets say you are in a space shuttle, for example, orbiting the Earth such that you are experiencing weightlessness. You climb into the cockpit and fire the engines, accelerating the shuttle forwards. Any object in the space shuttle will resist this acceleration, so you will be pushed back into your seat. ",
"Likewise, the air in the shuttle will feel this same inertia, and will be pushed towards the rear of the shuttle as long as you are accelerating. The balloon will move forwards as a result; the air has more mass per volume (density), so it will experience more inertial resistance when accelerating. This may seem counter intuitive, but you can test this out for yourself in your car - just buy a helium balloon, let it float to the ceiling in the back seat, then accelerate forwards from rest. You will be pushed into your seat, and the balloon will move forwards in the car."
] |
[
"the second scenario highlights the equivalence principle, doesn't it? Stuff that happens in gravity based reference frames also happens in reference frames that are under any other type of acceleration"
] |
[
"This is accurate, and is a classic example of the principle. The only caveat is that the rocket must be accelerating at a constant rate, such that the inertial effects are consistent."
] |
[
"Can the extraction of raw materials significantly influence the rotation and circulation of the Earth?"
] |
[
false
] | null |
[
"I think so, because the distribution of Earth's mass is changing. In addition, the Earth loses fractions of mass percentages by sending satellites / rockets."
] |
[
"Hello,",
"Open-ended or hypothetical questions are more appropriate for ",
"/r/AskScienceDiscussion",
".",
"Cheers."
] |
[
"ok thanks, I will ask it there because I'm curious."
] |
[
"/r/AskScience Vaccines Megathread"
] |
[
false
] |
Here at we would like to do our part to offer accurate information and answer questions about vaccines. How vaccines work The epidemics of an outbreak How vaccines are made Please remember that Do not post any personal health information here; it will be removed. Likewise, we do not allow anecdotal answers or commentary. This thread has been marked with the "Sources Required" flair, which means that answers to questions contain citations. Information on our source policy is . Please report comments that violate the guidelines. Thank you for your help in keeping the conversation scientific!
|
[
"There was a chance (",
"1/750,000",
") of contracting \"vaccine-associated paralytic poliomyelitis (VAPP)\" from the live, oral form of the polio vaccine. When polio was rampant, the risk of contracting the disease \"out in the wild\" was considered worse than than the risk of contracting it from the vaccine. Today, only inactive, injected polio vaccines are used in the US (the oral form is still used in other countries). ",
"Source",
"Additionally, it's possible to contract the disease just prior to vaccination or before the vaccine is effective. Polio can incubate for about a month before symptoms show, and multiple doses of the polio vaccine are needed to confer immunity. ",
"Source"
] |
[
"There was a chance (",
"1/750,000",
") of contracting \"vaccine-associated paralytic poliomyelitis (VAPP)\" from the live, oral form of the polio vaccine. When polio was rampant, the risk of contracting the disease \"out in the wild\" was considered worse than than the risk of contracting it from the vaccine. Today, only inactive, injected polio vaccines are used in the US (the oral form is still used in other countries). ",
"Source",
"Additionally, it's possible to contract the disease just prior to vaccination or before the vaccine is effective. Polio can incubate for about a month before symptoms show, and multiple doses of the polio vaccine are needed to confer immunity. ",
"Source"
] |
[
"As nearly any drug, vaccines can have several different side effects and can cause allergical reactions.",
"http://www.cdc.gov/vaccines/vac-gen/side-effects.htm"
] |
[
"If a blade such as a knife were to be completely sharpened, down to the molecular and atomic level, could it theoretically cut through ANYTHING? If so, what metal would the knife have to be made of?"
] |
[
false
] | null |
[
"No, the bonds at the very edge of the knife would have to be stronger than the bonds of the object you were trying to cut, and significantly strong, since you are putting more energy into the knife bonds by breaking more other bonds. The knife would blunt almost immediately anyway."
] |
[
"Yes, if it was indestructible and provided with enough force it could cut through anything. Unfortunately that kind of bond does not exist."
] |
[
"The knife would also have to be rigid enough for the bit not to fold over"
] |
[
"What's the deal with the squiggly lines when I mix alcohol and water/pop?"
] |
[
false
] |
[deleted]
|
[
"Your hypothesis is correct. Alcohol and water bend light differently, and having an incomplete mixture of the two causes certain areas to refract light one way and other areas in another. The result is the borders between areas become very apparent. "
] |
[
"You aren't making your drinks strong enough. Seriously. I can't see it with a shot of alcohol in a big cup of coke but if I see the squiggles I know I'm in for a good night."
] |
[
"Awesome, thanks!"
] |
[
"Is it true that marine iguanas boil the algae they consume before digesting them?"
] |
[
false
] |
Hi. I'm reading Kurt Vonnegut's Galapagos and at one point it says that marine iguanas dive underwater, scoop a large amount of algae and then bask in the sun to increase their body temperature until the algae have been boil and cooked, at which point they are soft enough to be digested. It even says that the digestive system forms a kind of pressure boiler. I've found this fascinating, but I haven't been able to confirm it. I've seen many pictures of iguanas basking in the sun and information about how much and which kinds of algae they eat, but I find no mention of the boiling part. Can anyone confirm it/debunk it? Edit: yeah, I know they can't literally boilt it or they would boil themselves in the process and die. My question is if they do use the heat and maybe, somehow, pressure in order to make algae more digestible.
|
[
"Vonnegut is taking artistic license here. Marine iguanas do not and cannot boil anything within their stomachs. The only thing I can think of is he is assuming they are basking after their dives in order to \"cook\" their food, but in reality they need to increase their lowered body temperature after losing energy/heat to the water. It doesn't cause any boiling within their stomachs (",
"Catchpole, 2004",
"). Or maybe it's a reference to the fermentation that takes place during digestion, which still is not boiling (",
"Mackie et al., 2004",
")."
] |
[
"Theres no way an animal can \"pressure boil\" food inside them so nah. The point of the pressure in pressure cooking is to raise the steam temp since waters temp can't exceed boiling so you're saying it goes beyond 212f/100c Inside an animal lol. Maybe this animal does spit up seaweed and let it cook in the sun and soften.. the rest is not true no way"
] |
[
"Vonnegut was being hyperbolical here. That is, a rhetorical statement that is deliberately exaggerated as a metaphor, which is not meant to be taken literally.",
"The water around the Galapagos is normally quite cool, around 15-20°C. This compared to the temperature on land which can reach 30°C in the summer. ",
"Marine iguanas are ectothermic. Meaning they don't have the ability to regulate their internal body temperature, like all reptiles. This requires less energy overall and allows them to subsist on a low quality diet of algae. It also allows them to hold their breath for longer. ",
"They spend much of their time basking on top of dark volcanic rocks that are heated by the sun. This not only helps them recover their strength after diving in the cool water. It also speeds up their digestion."
] |
[
"AskScience AMA Series: I am /u/pengdrew, a physiologist that studies Penguins! I study the physiology of aging in wild penguin species and am here to any questions you have about penguins, aging and physiology/ecology! AMA!"
] |
[
false
] |
Hi Reddit! I am a PhD physiologist and ecologist studying the physiology of aging in wild penguins! I am currently in the second year of my PostDoc studying stress hormones, aging, and ecology in Spheniscus penguins. Specifically my work explores the relationship between stress hormones, telomeres and life-history decisions (reproduction, mating, growth, etc) in a very long-lived seabird! I'm excited to talk about: A few other notes on me: I will be here from 12:00pm - 2:00pm PST (15 ET,20 UTC) to answer your questions… !
|
[
"I've heard penguins can get a bit...rapey. There was even a paper that got published, and then was retracted by its author because he was so shocked by penguins sexual behaviors. ",
"What makes it so shocking ?",
"Is there a way that paper will ever be republished?",
"Thanks!"
] |
[
"Are you referencing the observations from the Scott Expedition? I'm not aware of any retraction of a specific paper, the observation and notes from that expedition are on display at the British Antarctic Survey IIRC.",
"Edit: While I have not personally witnessed any similar observations in my field study. I have seen a number of penguins try to copulate with large round rocks, and some with the concrete floor of our research station.",
"Also, good post by ",
"/u/medsl",
", thanks!"
] |
[
"I've never been so excited for an AMA before! I hope you dont find my questions too silly or simple since I just love penguins and don't really have a science background:",
"1) emperor penguins get the most recognition (Happy Feet & March of the Penguins) but do any other species go through the same trials? ",
"2) How accurate was the information portrayed in March of the Penguins? Was there anything you think should've been included?",
"3) What's the least well known penguin species?",
"4) What's your favorite species? Why?",
"5) What poses the greatest danger for the penguin population besides global temperature changes?",
"6) Non arctic penguins don't get a lot of love or recognition to my knowledge...why?",
"7) What is the name of one of the penguins prehistoric ancestors? For example people consider wooly mammoth related to elephants - what's the penguin equivalent?",
"8) least well known fact about penguins?",
"9) how did you choose your specific focus/specialty and why? Why the sphenuscus species?",
"You are basically living my dream. I would've majored in ecology if i didnt struggle in physics so much (major requirement) AND penguins are my favorite animals."
] |
[
"Would it be possible to get a good parallax view of the stars by taking one image from earth and then another image in the same direction near the edge of the solar system?"
] |
[
false
] |
I mean, enough of a parallax that if viewed together side by side or on a 3dtv, that we'd be able to see a clear 3d view of most of the stars in the image? If not, how far would we have to travel before such a view would be possible?
|
[
"astronomers actually do use parallax more easily than that - two pictures from earth 6 months apart to use the size of earth's rotation.",
"http://en.wikipedia.org/wiki/Stellar_parallax",
"the differences are very small though, and even with computers, this is only useful for stars that are pretty close to us in the galaxy."
] |
[
"For many stars, the parallax of the Earth around the sun is too tiny for even computers to measure. Parallax is measured in arc-seconds, or 3600ths of a degree. For objects farther than about a hundred or so parsecs, it is basically infeasible to measure their distance using this parallax (according to Wikipedia this may become a few thousand parsecs in the near future). However, the more you move the two observation points, the better the measurement. So by taking parallax measurements from farther away points, one could certainly get a 3-d view of stars relative to each other (although their sizes are so tiny that you couldn't really measure them accurately with angle measurements).",
"Edit: Interestingly, the \"parsec\" that I refer to is actually defined as the distance of a body with a parallax of one second of arc."
] |
[
"At distances on the order of the size of the solar system, you could probably determine some parallaxes by hand, a larger number by computer, but still most would not be observable at all. Maybe you could get most of the stars in the galaxy, but for other galaxies, the parallax would still be far too small."
] |
[
"Are linear polarizers conductive perpendicular to the plane of polarization?"
] |
[
false
] |
From my understanding, and please correct me if I'm wrong, linear polarizers such as the ones in old 3d IMAX glasses (before they started being also circularly polarized), polarize light going through it by selectively absorbing the light whose electric field is lined up to induce little currents in the material. The polarizing material, of the sort that i'm talking about, not of the reflective type (with brewster's angle and the such), contains parallel conductive pathways so that electrons are only really free to move in one direction in the material - hence the selective absorption. Shouldn't this mean that polarizers are conductive along these conductive pathways? Is this true only in the ideal case? What I mean is...in actual linear polarizers, are the conductive pathways not necessarily connected - they are just all aligned?
|
[
"Some linear polarizers are made by etching gold into tiny wires (called a wire grid polarizer); these will definitely conduct. Other designs use long strands of conjugated polymers; though these are conductive locally, they aren't much better than a plastic at macroscopic scales."
] |
[
"That's what I thought. Do you know what the first type you mentioned is called or where I would possibly get it?"
] |
[
"They're pretty common in infrared spectroscopy, but expensive and unnecessary for visible light. In any case, here are some carried by ",
"Edmund Optics",
". The other optics guys also carried similar stuff at similar prices."
] |
[
"Why do rockets and other space probes spin/roll?"
] |
[
false
] |
Like for example take the Perseverance rover. In the animation that NASA uses, it shows the entry capsule to be spinning through space, and once they hit the Martian atmosphere, reverse thrusters stabilize it. Is spinning your way through space somehow important or beneficial? PS. First time posting anything on Reddit, please forgive and tell me if I did something wrong XD
|
[
"It's called spin stabilisation. A spinning object will tend to keep its spin axis pointing in the same direction. Many spacecraft have used it.",
"It's actually less common nowadays. Three axis stabilisation, using electronics to measure the spacecraft orientation and thrusters to keep it that way, is the alternative. But thrusters use propellant, spinning only needs propellant when you spin up or despin."
] |
[
"On top of spin stabilization as ",
"/u/cantab314",
" said it can also help with thermal control depending on the spacecraft design. In that case it's often call the \"BBQ roll\". You spin slowly so that there is not one face facing the sun all the time getting too hot. It makes sure that all external surfaces are at the same temperature."
] |
[
"I believe so, yes.",
"The page below mentions course correction burns by New Horizons. It mentions that for some corrections the spacecraft was in fact spun up for the burn, presumably having been non-spinning or spinning in a different orientation previously. Then spun down again after. The propellant used to spin up or down is small compared that needed for manouvres.",
"https://web.archive.org/web/20141010030345/http://pluto.jhuapl.edu/overview/piPerspectives/piPerspective_1_31_2006.php"
] |
[
"Is it true that COVID can make you lose memories?"
] |
[
false
] |
I’ve heard someone talk about it in the school, a girl might not be able to take the final exam at the end of the year, because she had corona. She lost significant amount of her memory, and doctors don’t know if she will recover. Is it true?
|
[
"Memory problems and other neurological symptoms do seem to be fairly common after recovering from COVID-19. For example, New York Times, Oct. 11: ",
"‘I Feel Like I Have Dementia’: Brain Fog Plagues Covid Survivors. The condition is affecting thousands of patients, impeding their ability to work and function in daily life.",
". ",
"Also:",
"The most frequently reported persistent symptoms were fatigue (55%), dyspnoea (42%), loss of memory (34%), concentration and sleep disorders (28% and 30.8%, respectively). ",
"—",
"Post-discharge persistent symptoms and health-related quality of life after hospitalization for COVID-19",
"Patients having COVID-19 infection could have cognitive impairment shortly after hospital discharge. Presence of neurological symptoms during the infection such as headache, anosmia and dysgeusia were the main risk factors for cognitive impairment related with attention, memory and executive function. ",
"—",
"Cognitive profile following COVID-19 infection: Clinical predictors leading to neuropsychological impairment"
] |
[
"It's important to qualify what we mean by \"memory loss.\" Colloquially, when we casually refer to \"memory loss,\" what we're usually talking about is ",
"retrograde amnesia",
", which is roughly \"something making you forget things you used to remember.\" This is usually associated with something significant happening to the brain itself, either in the form of direct physical trauma or in the form of a chemical (crossing the blood-brain barrier) destroying or otherwise disrupting neurons.",
"COVID-19 has been observed to cause what's classified as \"brain damage\" at a high order in many patients, but retrograde amnesia is ",
" a commonly observed effect. In that sense, colloquial \"memory loss\" isn't associated with COVID-19 to a significant degree. But what ",
" associated is difficulty in forming new memories--not full-blown ",
"anterograde amnesia",
" (counterpart to retrograde), but more of a so-called \"brain fog\" that can make it very difficult to learn. Reductions in working memory, higher latency in recalling patterns, and lower recall after exercises are all potential \"things\" to worry about. A large number of COVID-19 patients may suffer from some degree of long-term neurological damage to that effect, perhaps even permanently.",
"https://www.thehealthsite.com/news/covid-19-infection-may-cause-irreversible-brain-damage-775750/",
"Fortunately, it's not common for the deleterious effects to be so profound as to functionally incapacitate someone forever, but it's very plausible that some people are going to be strongly affected in their cognition by post-COVID-19 effects for a long time to come."
] |
[
"https://www.healthimaging.com/topics/advanced-visualization/covid-19-brain-abnormalities-mri",
"Simplifying it a lot, some have lesions in brain tissue after recovering. A general inflammation may be recoverable, but some of these complications will stay with you forever."
] |
[
"If the earth was not spinning around itself, would the apparent gravitational force be different?"
] |
[
false
] |
[deleted]
|
[
"Yes, but very slightly. The acceleration due to gravity you feel due to earth's gravity is ~10m/s",
" The acceleration you feel on the equator is about 0.03m/s",
" less than at the poles due to the rotation of the Earth."
] |
[
"Oh, I thought that the 0.03 difference was due to the earth being a little \"fatter\" on the equator compared to the poles and not due to the tangential speed."
] |
[
"the effect of the earth's rotation on gravity is called \"Coriolis Force\". It's pretty small, compared to \"regular\" gravity, but its impact is huge on the climate, shaping the path winds take.",
"here is a cool video to demostrate what the coriolis force and its associated effect is:\n",
"http://www.youtube.com/watch?v=aeY9tY9vKgs"
] |
[
"How much lead would be equivalent to Earth's atmosphere when it comes to stopping radiation."
] |
[
false
] |
Does this even make sense?
|
[
"There's no hard and fast answer to this question - lead has an atomic number of 82, while the atmosphere has a very low average atomic number (in the range of ~7). Depending on what type of radiation (photons, protons, etc) or the energy of those particles, the effectiveness of shielding can vary wildly with Z. ",
"In general, the effect of radiation shielding increases linearly with the amount of material you put in front of it. Wikipedia says that if the atmosphere was of uniform density, it would be ",
"8.5 km thick",
". Air is about 1000 times less dense than water, and lead is about 13 times more dense than water - so each cm of lead is ",
" 13,000 more stuff than a cm of air. This would mean than about 65 cm of lead would have an equivalent thickness to the atmosphere. "
] |
[
"Keep in mind that Earth's atmosphere is not the only radiation stopping tool. In fact the magnetic field set up by its rotating core acts as a barrier as well, redirecting most of the cosmic rays that would otherwise strike the surface."
] |
[
"Since you can't assume that the atmosphere has the same density at all the altitudes, I don't think you can calculate the answer to my question with only those values."
] |
[
"What do neutron stars really look like?"
] |
[
false
] |
Neutron stars are almost always depicted faint with surface features readily visible, spinning rapidly on its magnetic axis. However, pulsars such as the crab pulsar do not certainly look like this. Before you answer, just know I already l know what hotspots and the precessing astrophysical jets are, so you don't need need to explain it. What I'm curious about is the atmosphere (Corona) of the star and how the magnetosphere and gravitational lensing affects it. Also how bright would the jet be in comparison to the neutron star?
|
[
"Accretion jets are black holes. They're completely different than the energy jets from pulsars. The glow from the jets and the gas in the nebula is a reaction with the light rather than the original light itself. That's why there are a variety of colors. Its because of the variety of materials the light is reacting with. Think of it sort of like a black light. You really can't see it, but you can see it after it phosphors off something white which changes its wavelength to something you can see"
] |
[
"The jets and the neuteon star probably wouldn't be very bright at all from your perspective as far as stars are concerned. The star would likely be a faint bluish white. This is because most of the light would be emited in the ultra violet+ range, so you would only be able to see the bluish white on the visible end of that spectrum. As for the jets, you probably wouldn't see them at all. This is because they're high energy X rays and gamma rays. Far outside of the visible spectrum. Also even if the light was visible, you wouldn't be able to see it because it wouldn't have anything to bounce off of. Think shining a red laser pointer and not being able to see it in the air. "
] |
[
"A hot blackbody IIRC doesn't stop or reduce emission at lower frequencies as it heats up, but rather increases emission across the whole spectrum. So a hot neutron star would appear blindingly blue-white at any visible distance."
] |
[
"What is a plausible scientific explanation for \"glory clouds\" in church services?"
] |
[
false
] |
I read a NYT article about a runner that relied on his faith. He mentioned something about "glory clouds" during his church service. Being the skeptical citizen I am I was curious and googled it. I found a few youtube videos of the phenomenon occurring in their church (Bethel Church in Redding, CA). I googled around to see if there was a debunking and I found nothing more than some suggestions that it was either a malfunctioning in their ventilation system, or a good old fashioned glitter dump. Are there any reasonable explanations here? Or is trickery at work? Thanks! NYT article: Youtube video (one of many similar):
|
[
"Edit: Probably ",
"This.",
"It is most likely due to the condensation of water from evaporated sweat and breath. Supposedly if one of Hitler's buildings had been created the amount of people within the room's combined water generation would cause rain. ",
"Most likely in the video the air conditioning system cooled the evaporated water into mist giving the \"glory\" cloud."
] |
[
"That's dust. Definitely dust, you can tell by the straight line it makes coming from the light. "
] |
[
"Hitler's buildings",
"what?"
] |
[
"How do erasable pens work?"
] |
[
false
] |
How does the ink and eraser of an erasable pen work? I've been curious for a while.
|
[
"Thermochromatic eraseable pens are a recent innovation. The first eraseable pens, and the ones that most people are familiar with, use a rubber cement ink that comes off the paper through mechanical force."
] |
[
"This is true, but you can recover the document by popping it in the freezer. The ink is thermochromatic. You can cycle it from pigmented to colorless more times than I care to test."
] |
[
"This is true, but you can recover the document by popping it in the freezer. The ink is thermochromatic. You can cycle it from pigmented to colorless more times than I care to test."
] |
[
"Why do these droplets spread out into star-like patterns as they freeze?"
] |
[
false
] |
We're currently in a cold stretch - roughly 0°F, swinging a little above during the day and a little below at night. Every day, the sun hits these ice crystals on our window and melts them into round water droplets, but it's too cold for them to evaporate. So every night, they refreeze in these sort of star patterns. Why do they change shape as they freeze, rather than freeze as droplets? I've been thinking about it myself - I assume they start freezing on the outer surface, and water of course expands as it freezes. I'm tempted to think that the glass might be slightly warm under the droplet since it's close to the house, but this phenomenon happens on a screen as well, and in that case both sides are exposed to the cold air. I've tagged this as physics, but I suspect that a materials scientist could help as well. The pattern reminds me of dendritic crystals that I've seen in additive manufacturing papers.
|
[
"In general you see dendrites as a growth mechanism when you have a diffusion-limited transformation process. In this case, it's likely the rejection of the heat of fusion from the liquid/solid phase transformation. As you transform into ice, you have an exothermic event. This will lead to locally warmer central areas, making the extremities push outwards looking for a cold region to reject their heat to such that they can solidify.",
"I think I have that right, I spent my degree trying to avoid crystallization by making amorphous materials, lol."
] |
[
"Oh, sure. When you change from one phase to another (say, from ice to water when you're melting), it will happen at a single temperature for a pure substance. However, it takes a significant amount of energy to do this. This is the reason we put ice cubes into drinks. It'll cool your drink down to 32 °C for a long time. In fact, if your stir your drink regularly, it won't heat up at all until all of the ice is gone (though you will notice your drink has gotten more watered down as the ice melts into water). Once all of the ice is gone, your drink will rapidly heat up since any added warmth (from the room, your palm, the sun, etc) will go into heating the liquid as opposed to melting the ice.",
"This is also why you want to use really cold ice cubes for a drink. When you first add the ice you exchange heat between the drink and the ice. The drink cools down, and the ice gets heated up. In an ideal case, the drink will be cooled down to 32 F while the ice will stay even colder. If you've ever added really, really cold ice to just a little bit of water or non-sugary (or alcoholic) drink, you'll actually find some of your drink will freeze!",
"As a note, heat of fusion is typically used since the heat required to melt something is the same as the amount of heat needed to be removed to freeze it. Same with heat of vaporization is the same as vaporizing vs condensing. Also heat of sublimation (solid directly to gas) is what you use dry ice for. It doesn't go through a liquid phase, so no liquid mess. Interestingly enough, Heat of Sublimation is approximately equal to Heat of Vaporization + Heat of Fusion."
] |
[
"In my example in the second paragraph, the ice is colder than 32 F. If it's colder than 32 F it has to be heated before it can begin to melt. So, if your freezer is set to 20 F you get 12 degrees of sensible heating prior to latent heat transfer."
] |
[
"Should I finish my PhD in Cancer Biology if I Want to Go into Biotech/Pharma Consulting or Even Business Strategy Consulting"
] |
[
false
] |
Right, I already have a Master's and I will be completing my last qualifying exam for the PhD in about 2 months which will make me a PhD candidate. After that I will only have to successfully defend my disseration to obtain the degree. But the problem is that it will likely happen no earlier than the end of 2012/beginning of 2013. I'm 34 now and will likely graduate at 36-37 years of age. I'd very much like to leave lab bench science and am attracted to Biotech/Pharma consulting but would even consider business strategy consulting at BCG, for example. I know that these consulting firms "say" that they don't really require that their consultants have PhDs so I wonder if that's bullshit and that a terminal (which a Master's is not) advanced degree is required a PhD is still valuable enough in this down-turned economy to be worth the extra years that it would take to complete it with respect to the consulting market, keeping in mind that I'll be ~37 when I make myself available for the job market a Master's degree would be enough for consulting firms to take on a 34 year old with no experience (or is age something I shouldn't consider?). Certainly I plan on trying to get internship prior to my graduation but even then it will likely only be during my last year as a PhD student because of the time demands placed on the student. I'd appreciate any input anyone (especially those already in biotech/pharma or business strategy consulting field) would have. Cheerz! I graduated with a BS in '99 and entered industry doing rote tasks til 2002 when I reentered academia as technician (sadly with only 1 publication (middle author) and various poster abstracts) and later entered into the Master's program and earned my Master's 2009 and just finished my second year of my PhD. The average number of years to complete the PhD in my field is 4-5 total years. 2011 is the beginning of my 3rd year. (xpost from and )
|
[
"Finish your Ph.D., the two or three additional years are very much worth it.",
"Credibility in biotech/pharma consulting is very important! Your Ph.D. candidacy is not going to get you that. It may be different in business consulting, but if you want to keep other options open (e.g. application scientist or something like that) you'll need the Ph.D.",
"Another way to look at it: you're already a bit on the older side for your entrance into the job market. If you get the Ph.D. you will at least have something to show for it.",
"Yet another perspective: quitting half-way through your Ph.D. program won't look all that great on your resume.",
"That all said, if you get a great job offer tomorrow, things may look different."
] |
[
"Do you have connections or any experience with the industry you're trying to get into? I don't really know, but it seems to me that a combination of you'll have a PhD and the job market will be a lot more friendly makes waiting to graduate a much more attractive option.",
"Of course, you could just apply and see what happens, right? I'd also recommend that whether or not you apply, you try to get in touch with relevant hiring managers and ask them what they're looking for. I don't think they'd mind being asked for honest advice from a prospective applicant."
] |
[
"The consulting firms that I know of (like McKinsey) are extremely competitive. I've heard that they pretty much won't even consider you without a PhD, but I don't know about other firms or if there are specific types of jobs that cater towards those with a Masters. You can always consider contacting someone at whatever firm to ask them some questions.",
"For biotech/pharma, there are jobs available for those with a Masters, but the jobs open to PhDs tend to be better in position, pay scale, and promotion opportunity. ",
"All in al, I'd also continue with the PhD. Good luck!"
] |
[
"When I heat up a metal where do photons come from?"
] |
[
false
] |
So I heat up any given metal to the point it starts giving off light, just like in a light bulb or foundry/ironworks. Where do photons come from and assuming I do so in a vacuum would such metal lose it's weight after some time?
|
[
"A photon is an electromagnetic wave. You make one by \"shaking\" an electron (any charged particle actually, but electron is most common). When you shake an electron you cause a momentary electrical wave, which then self induces a magnetic component and that's what a photon is.",
"No nothing is lost from the electron when you make a photon.",
"In order to shake an electron you need energy, that energy is used to create the photon.",
"When you heat anything (not just metal!) the atoms vibrate from the heat. This vibration is also shaking the electrons which then emit photons constantly. (Even at low temperatures photons are constantly being created - you just can't see them. See blackbody radiation if you want to know more.)",
"There are other ways of shaking electrons - a cool one is a free electron laser. You shoot an electron between alternating pairs of magnets. The magnets cause the electron to wriggle back and forth, producing photons. (It's called a free electron laser because the electron is not attached to an atom - it's traveling in the empty space between the magnets.)",
"You can move electrons in wires - which is how radio transmitters work.",
"An electron can absorb some energy, this causes it to \"jump\" to a higher orbit in the atom. When the electron \"falls\" back down (and it will), the motion causes it to release a photon. This is how chemical light (like from a firefly, florescent lamp, or most lasers) is produced. In a glow in the dark toy, you charge it with light - the light causes the electrons to more to higher orbits. They then take a while to fall back down - when they fall down they emit light. If you've seen white clothing glow in UV light, it works the same way. The electrons absorb the UV light, and then fall down producing their glow (unlike a glow in the dark toy, in this case they fall immediately).",
"When an electron falls down it always emits a very precise amount of light. This is because it can only obit the atom in very specific levels. So it always falls an exact amount (depending on which level it reached, different atoms have different possible levels, and usually more than one). That's why the glow is always an exact color."
] |
[
"As Nune said it does lose the mass-energy of the photon, but it had just gained that much mass-energy from the heat input. There is no net loss of mass over time: it can emit photons forever as long as heat keeps getting dumped in."
] |
[
"In blackbody radiation the electrons are not in excited states. If they were, the light would be mono-chromatic. Instead you have wide-band light because the atoms are vibrating randomly and directly generating light.",
"You do have peaks in the light, which do reflect excited states, but they are a small component of it."
] |
[
"What are the differences between Methimazole for humans and Methimazole for cats?"
] |
[
false
] |
Long story short, one of my cats needs Methimazole to treat his Hyperthyroidism. Doing preliminary search on only Google results, there is a form of Methimazole that can be used for humans. I was curious about the differences between the Methimazole that is used for humans and the Methimazole used for cats? Thank you.
|
[
"The majority of medicines prescribed to pets are actually drugs made to treat humans. This is true for most chronic or acute conditions. Most \"pet only\" drugs that are developed are preventative medications like flea, tick, and heartworm. This is why you should always price shop for your pet's meds. If the vet is prescribing a med that is also for humans, you should never buy it from the vet. Go to Costco, no need for a membership to use their pharmacy, and i guarantee it will be cheaper. Never, ever, buy directly from the vet and always ask if there is an equivalent human med to treat whatever condition your pet has."
] |
[
"Typically drugs for human use are subject to more (or possibly different) testing, and more control of quality systems. The active ingredient can be chemically identical, but the control around the manufacturing can be different. I have no special knowledge of this drug though. "
] |
[
"The dosage of the drug can also vary between humans and animals. Eg if a human needs, say, 10mg/kg and they weigh 70kg, they need a dose of 700 mg. If a cat needed the same dose it'd need like 50 mg. So human drugs might be packaged in pills of 100 mg where cat pills would only have 20mg.\nAs well as this, the cat dose rate may also be different, so while the human may need 10mg/kg, the cat may need 5mg/kg, so again it might be more practical to put more drug per pill in the human medicine compared to the cat one.\nTL;DR: human and cats need different doses, so cat pills may be more or less concentrated"
] |
[
"How does dark energy relate to vacuum energy?"
] |
[
false
] | null |
[
"Vacuum energy must contribute to dark energy. However, dark energy can also include other contributions. Quite literally:",
"Dark energy = vacuum energy + ..."
] |
[
"Yes, and the point is that ... is negative and equally big. ",
"In particular ... includes a renormalization counterterm that should cancel the vacuum energy to get a zero or very very small result for dark energy. The counterterm is arbitrary at the level of the standard model, though. A theory of everything should include an explanation for this cancellation, perhaps on the basis of a general principle that in our low-energy perspective is opaque."
] |
[
"Yes. That's why it really cannot be a coincidence and there's an explanation behind. In fact at the very simple level at which I understand this, I would argue vacuum energy + counterterm sum to exactly zero because of ToE reasons, and our current value of DE is due to another contribution of different origin. ",
"EDIT: just because I need to make one string theory example per thread: in string theory (where the counterterm is not arbitrary) the above cancellation does actually happen. So it looks promising."
] |
[
"Why does Boiling Point of a substance change on change in pressure in surroundings?"
] |
[
false
] |
Lately, I had been watching a documentary on Terra-forming mars, in which it was said that, The only problem water was not to be found on the surface is that the atmospheric pressure in the surroundings is too low for water to stay there in liquid form. My question is, According to the Ideal gas equation, PV = nRT, If pressure decreases, Temperature also decreases, but how is it possible that Boiling point and Melting point also decreases?
|
[
"Ideal gas law only deals with the ",
" of a ",
". If you have a steel box full of air, and you heat it to double its temperature, it would double the pressure of the gas inside. But that is simply the state of the gas in the box. If I did the same thing with a gallon of a gas in a ten gallon hefty bag, the bag would just inflate to 2 gallons and stay at the same pressure when I doubled the temperature. And once again, its a change of the state that the gas is in. Pressure is a function of state dependent on temperature and volume.",
"Now, if I have a jar filled half way with water, and then sucked the air out of it, the water would evaporate to fill the vacant area because the force keeping it down in its liquid phase was suddenly taken away. The pressure that the water vapor exerts is called its \"vapor pressure\". At some point, the vapor pressure above the liquid can apply enough force on the surface of the water (pressure. pressure=force per unit area, like pounds per square inch) that its just as stable being held by the strong inter molecular forces of the liquid form as it would be if it were to evaporate. Its like a bar hitting max capacity, there're still a bunch of people waiting outside, but there's a big russian hairy dude at the front door keeping 'em back in line. Of course of someone leaves, they can let someone in, but they can only let in as many people as the number that leaves. And if i heat that jar, more water can break free of the liquid phase and become a gas, increasing the vapor pressure above the liquid AS WELL AS the pressure of the water vapor already above the liquid (because PV=nRT). So, now that the force holding the water down into liquid just increased, i have to add even more heat to get the same result as before. (that's the dependency of a liquid's ability to evaporate on the pressure of the gas above it, or, pressure on boiling point temperature)",
"NOW, I've got a pot of water. And I'm heating it. But the vapor isn't pressing down on the liquid nearly as much anymore, because the volume of your house is so much significantly greater than the volume of that tiny jar. The water molecules have somewhere to go. So, I have the pressure of the atmosphere pushing down on the surface of the water. But, I can safely assume that by heating the water, I am not changing the pressure of gas pushing down on the water, keeping in liquid form. You are now heating water at a constant pressure (changing the temperature but not changing the force pushing down on the surface of the water). As you increase temperate more and more water molecules on the surface of the liquid have enough energy to break free from the liquid and enough to fight back the pressure of the atmosphere. The hotter it gets, the more it evaporates, the more evaporates, the more this quality know as the vapor pressure of the substance increases. Think of the vapor pressure as the force that the molecules can apply to atmosphere pushing down on them. And when the temperature of the water is at the point when the vapor pressure matches the pressure of the atmosphere, the water is no longer stable as a liquid. This is the boiling point temperature. If I increase the pressure of environment, by heating it, or just adding more air, the bar is raised for how hot the water needs to get before it is no longer stable as a liquid. Likewise if I have really really hot, but not boiling water, I can change lower the boiling point temperature by sucking out the air over the water, until it boils."
] |
[
"I wrote an explanation of that yesterday"
] |
[
"The boiling point is the easier concept to think about. When you have a liquid (in 1 atmosphere of air pressure) we define its boiling point when its vapor pressure is equal to atmospheric pressure. The vapor pressure of a substance is related to temperature, so increasing the temperature increases the vapor pressure till it =1 atmosphere and starts boiling. The inverse as you decrease the pressure the temperature required to boil is also reduced. This trend is very consistent between material systems.",
"The melting point side of things, well that is more complicated. Lets take two common substances and look at their phase diagrams ",
"Water",
" and ",
"CO2",
". At a given temperature increasing the pressure of water(ice) will lower the melting point. However for CO2 (Dry Ice) increasing the pressure will actually increase the melting point. So the melting point change with pressure is not as clear cut as the boiling point."
] |
[
"Why do blurry objects become clearer when we squint our eyes?"
] |
[
false
] |
[deleted]
|
[
"First of all, realize that this only works for people who have vision problems due to incorrect focusing of the light. For our eyes to work properly, incoming light must be focused down to the retina. When this does not happen, either because light is focused in front of the retina (a condition called myopia or nearsightedness), or behind the retina (hyperopia or long-sightedness), objects are various distances will look blurry since the image will be defocused, as shown graphically ",
"here",
".",
"Now squinting can remedy this situation in two ways. One possibility is that the deformation created by squinting can partially offset the natural imperfection in the eye, and can thus bring the focal plane of the eye closer to the retina. This will effectively offset the initial optical aberration and allow you to see an imagine which is better focused and thus sharper.",
"The second possibility is more general, and results from the increase in depth of field created that results from decreasing the aperture (opening) through which light enters your eye. Because of this even an image that is equally out of focus will appear sharper because the higher depth of field means that the sharpness of the image decreases more slowly as you move away from the correct focus. To better visualize this second effect, take a look at ",
"this series of images",
". Notice that as you decrease the opening of the lens, an increasingly large part of the field of view appears clear. This exact same effect is at play when you reduce the size of the opening into your eye (you can get a similar effect from looking at objects through an index card with only a small opening allowing light through)."
] |
[
"I drew you a picture. Basically it blocks all light that isn't coming in straight so there's less dispersion. The picture will explain it. Also, unless you have a 100% perfect cornea and eye muscles, this will help. ",
"http://i.imgur.com/b7tQ7D6.jpg",
"Try the pinhole trick. Close one eye and unfocus the other one (make everything blurry) Make a tiny hole with your fingers and look through it. It should be relatively clear. Same concept."
] |
[
"This image",
" can help understand the two effects.",
"The increase in field of fiew correspond to the first 2 pictures. ",
"The change of focal plane correspond to the last 2 pictures. When the hole is small, the light is diffracted and does not travel in a straight line anymore. This will help short sighted people to focus, but this also makes far sighted people lose focus even more. "
] |
[
"Will quantum computation kill crypto?"
] |
[
false
] | null |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"It is hypothetical or speculative in nature. We do not allow hypothetical questions because questions that cannot be confidently answered with any available data often invite non-scientific speculation. For more information regarding this and similar issues, please see our ",
"guidelines.",
"A good home for this question is our sister subreddit ",
"/r/AskScienceDiscussion",
" because of its open-ended or speculative nature. Please feel free to repost there!",
"Please see our ",
"guidelines",
".",
"If you disagree with this decision, please send a ",
"message to the moderators."
] |
[
"It’s not really speculation. An expert can easily answer this without speculating. Please reconsider."
] |
[
"You are asking about a situation which has not yet come to pass, which requires speculation. Please consider posting in ",
"/r/AskScienceDiscussion",
" "
] |
[
"What is the catch on this machine. Why is it not flourishing?"
] |
[
false
] |
This machine turns plastic waste into oil. Is there an ecological catch which is preventing this machine from spreading across the world? Why is this not spreading like wildfire?
|
[
"He is taking polymers (presumably mostly simple stuff, like polyethylene) with molecular weights of probably 80,000 - a few hundred kilodaltons, and supposedly breaking them down in a controlled fashion to oils of a couple hundred g/mol. Supposedly. There is also effluent gas that is not accounted for. While the water may capture the heavier stuff, there is probably a good amount of methane and other lighter hydrocarbons released using his process. ",
"This sounds a lot like \"catalytic cracking\" which is done with catalysis to retain control over the reaction products as well as lower the energy use significantly. ",
"Except, with no mention of catalysts, it is probably more like old school thermal cracking. Nothing wrong with that, but it is more of a novelty and a demonstration than a real world solution if you are doing it on such a small scale. ",
"So another way to pose your question is really - why are ",
" not taking off? Well, because while simple in theory, oil refineries are really pretty complex in practice. They work better (better, meaning more energy efficient and more safe) with a team of engineers, a full time staff, control systems, optimized heat exchange networks, and all of these things take a lot of money and time to build. Then, even with modern technology and safety systems, at the end of the day you are making flammable and explosive products, which can ",
"cause problems",
" since real-life issues of corrosion, and other maintenance and wear becomes an increasing concern. ",
"So, I am positive oil companies could build a modern refinery that can do exactly what is being done in the small scale machine shown. But they would have to staff it, and make sure it would turn a profit in X number of years. ",
"The real application of the small scale unit would be - given free electricity (solar?), it would be a good way for people in remote locations with lots of polyethylene waste to make oil to supply a small village for their heating and cooking oil needs. "
] |
[
"My semantics were off. I meant oil that you burn to cook stuff (as is common in India for example) not oil used to fry food. ",
"I guess this is still considered \"heating oil\" "
] |
[
"My semantics were off. I meant oil that you burn to cook stuff (as is common in India for example) not oil used to fry food. ",
"I guess this is still considered \"heating oil\" "
] |
[
"People say that a nuclear bomb is equivalent to X tons of TNT. Well, if X tons of TNT were actually there instead of a nuclear bomb, will it have the same effect?"
] |
[
false
] |
Perhaps without the radiation. But I'm talking more about the shockwave, destructive force, etc. And assuming you can blow them up at the exact same time.
|
[
"According to a 2010 report by the National Confectioner's Association (First result of ",
"this",
" Google search because I couldn't find a direct link-PDF warning), Americans ate chocolate 107 times in 2010. If we assume that averages out to about a ",
"50g Snickers bar",
" that comes out to 5.35 kg per capita, which matches well with ",
"this",
" article, which gives 5.09 kg per capita in 2008. If we assume a similar growth in chocolate consumption from 2008 to 2014, Americans consumed approximately 5.87 kg per capita in 2014.",
"In 2014, the US population was approximately ",
"323 million",
", meaning Americans ate about 1.9 billion kg of chocolate, or about 5 million kg/day.",
"According to the ",
"USDA",
", milk chocolate has 535 kilocalories/100g, or 5350 kilocalories/kg, or 5,350,000 calories/kg. So Americans ate 26,700,000,000,000, or 2.67x10",
" calories of chocolate per day in 2014.",
"Fat Man had a yield of ",
"84-92",
" terajoules, so we'll split the difference and say 88 TJ, or 8.8x10",
" joules. At 4.184 J/cal, it had a yield of about 2.1x10",
" calories.",
"So with a chocolate consumption of 2.67x10",
" calories, we can say that, within an order of magnitude, Americans consumed 1 Fat Man worth of chocolate every day in 2014. Over the course of a year, Americans consumed somewhere between ",
"Ivy King",
" and a ",
"B53 nuke",
", or about 0.15 ",
"Tsar bomba",
"."
] |
[
"It's an equivalency of energy ",
"They could also equate it too calories or joules but tnt they think is more relatable",
"To answer your question directly no it would not explode the same simply because a nuclear bombs volume is smaller than that many tons of tnt and many other factors "
] |
[
"So how many fat man's worth of nukes does America consume in candy bars every day?"
] |
[
"How are the repeated segments in a centipede developed?"
] |
[
false
] | null |
[
"In short, it’s basically due to a wave of transcription and following non-transcription of specific developmental genes throughout the body plan of the embryonic centipede. Waves of transcription/non-transcription are key for development and signalling in other organisms too, like the muscular system developing from specified predecessor muscular tissue (somites) that develop at the right time and the right place due to gradients of certain proteins being present or not. "
] |
[
"Also, this is a good paper to read about your question specifically: \n",
"https://scholar.google.ca/scholar?q=segmentation+development+chilopoda&hl=en&as_sdt=0&as_vis=1&oi=scholart#d=gs_qabs&u=%23p%3DHkmBh2FaEZoJ",
" "
] |
[
"Thank you!"
] |
[
"How come teeth move back to their original positions if you stop wearing braces?"
] |
[
false
] | null |
[
"Dentist here. There are many different factors affecting movement of a tooth. If your treatment with braces is incomplete, then as commented above, one factor causing relapse is that the soft tissue fibres attached to that tooth will be under tension to a greater or lesser degree in certain directions and will pull it back like an anchor tugging a drifting ship back to its immediately preceding position.",
"But to really answer your question, it’s helpful to think about teeth and their movement differently. Teeth never move back to an ‘original’ position. At any moment in your life there is a position that they are moving toward. Your teeth in fact never stop moving. They all move so slowly that you just can’t see it happening. The position they are drifting into changes as time passes. People who’ve had braces and people who haven’t both notice their teeth moving by the time they start to tip outwards, inwards, or overlap. This is why people in middle age discover that braces are for them after years not minding the mild crowding they used to have.",
"The teeth can move because they are not like a house built with foundations driven & cemented into the earth. They are floating gently on a cushion of soft tissue in a sea of bone that constantly changes shape. Around each tooth root is a sheath of fibres, a ligament, which works as a shock absorber. Pressures and tensions in that tissue from all kinds of things including your bite force and direction, the pressure of your tongue outwards and your cheeks/lips inwards, all cause a complex interaction between the cells of the soft tissue and the surrounding bone that can dissolve away bone and regrow ligament in any given direction. This is how pushing, pulling or torquing a tooth with braces can move them all around. But they do this on their own constantly anyway. The bone nearby is shapeshifting too. Your bones turn over - they disassemble and reassemble perpetually, remodelling depending on the work you have them do. This is why astronauts on the ISS lose bone density under low-G conditions as their muscles do less work to move their bones around in space, and they need to do extra workouts to maintain bone density.",
"The ‘original’ position that you’re picturing was a position of all the teeth at which they each were feeling a similar amount of pressure in all different directions. We call this equilibrium position the ‘neutral zone’. External (cheek lips tongue bite) and internal (ligament fibres etc.) forces balance out to hold each tooth in its place over time. If you’ve shoved all your teeth into a more attractive or more useful position, in which the lips happen to pull in far more strongly than the tongue pushes out, for example, your front teeth will obviously want to drift back to tipping inward. Your orthodontic treatment outcome is never a long-term stable position. So listen to your orthodontist when they tell you retainers are needed for life!"
] |
[
"That's really interesting!! Thanks for such an in depth reply I'll definitely remember this haha"
] |
[
"Well aligned teeth are definitely much easier to keep clean than crowded ones. They function more efficiently when chewing as there are minimal gaps between upper and lower teeth when closed. Being properly aligned can allow them to work together better and prevent excessive forces and wearing of a few teeth, instead spreading the forces equally over all of your teeth.",
"Edit: for mild malalignments, there is rarely an issue. Think of it as a continuum. The more aligned your teeth before orthodontics, the slighter the benefit. There are definitely lots of people who have mild enough alignment issues that it's not worth treatment"
] |
[
"Why do wet dogs have a stronger smell than dry dogs?"
] |
[
false
] |
I was lying next to my cat when I realized he smelled like a wet dog. Then I wondered why wet dogs have a specific smell. What causes this?
|
[
"It's essentially ",
"steam distillation"
] |
[
"Hmm, aromatics' solubility in water vs. its volatility (in air)?"
] |
[
"This is at least one side of the answer: An old chemistry teacher explained to us why the smell of a fart magnifies in a shower compared to any other environment. The answer was that the aromatics (smell molecules) are entrained in the water vapor, essentially attaching to it to make for a more efficient ride to your olfactory system.",
"So as your dog gets wet, all of the aromatics coming off your dog are now jumping onto the water vapor that is also coming off your dog, and making its way up into your nose.",
"There might be something more besides this, perhaps a chemical reaction, but I'm not sure of it."
] |
[
"If plants are constantly exposed to the sun, why don't they develop cancer?"
] |
[
false
] |
Is there something special about plant cells that shields them radiation that is harmful to humans? It it possible for a plant to "develop cancer" or any sort of harmful mutation?
|
[
"Plants do develop cancer. But their lack of a circulatory system makes cancer not very harmful to plants. Note that, in humans, cancer is usually only deadly when it is able to spread through the bloodstream and start growing in many sensitive areas of the body at once (such as the brain). In plants, cancer just manifests as a local growth."
] |
[
"Woodworker here, they're also worth a shitload of money if they're properly dried. (Because they're beautiful)",
"Example 1",
" ",
"Example 2"
] |
[
"Yup. Did you ever see those weird lumps on trees? They are called burls and are a sort of plant malignancy."
] |
[
"[x-post from ask reddit] question on human evolution"
] |
[
false
] |
Hello, it was suggested I post this here. I've since done a little searching on reddit and no previous threads seem to address what I'm driving at; Ok Reddit; You seem to know way more about science than me and I trust that a lot of you can answer this question to your own satisfaction but you may not manage to educate me if you assume that I have the same scientific education as you. My formal science education stopped 11 years ago when I was 16 years old. Since then it has been what I happened across and conversations with scientists. (I love learning through conversations). Please go slow explaining this... Here's my understanding of the principles of evolution theory; If you live to make babies who live, well done your genes are passed on. If you don't, sad times mr, your genes are no longer contributing anything. If a certain gene gives you an advantage over your competitors for a mate or for a dwelling or for surviving a winter etc then they will help you to survive and make a baby or two. This way the genes that are helpful slowly are preserved whilst the genes which do not help or even hinder slowly get weeded out. It's good it's logical and I'm happy. Until... I'm considering the final stages of human evolution; At some point we got quite ahead of the curve. We're much more intelligent and adaptable than our closest evolutionary relative right? We have developed technology like weapons and clothes. We can adapt much better. So at some point our competition stopped being with the other species I think and was only down to who got to sleep with yonder hottie and who survived that snow storm last winter. Perhaps it was also to do with fights over who get's to sleep in this part of the valley. My point is. There's a huge amount of lovely inhabitable fertile world out there. Once we beat the apes even by 25% of the advantage we have over them now, why did we continue to evolve so far in advance of them? Our competition with fellow humans is surely not fierce enough? Only now are we really in a place where the population is unsustainable. Why would we have evolved before now? I apologise if this is long and meandering. I wish I knew the short hand for explaining these ideas. TL DR; Oh man, how to succinctly ask? Why are humans so far in advance of other species? What was the evolutionary motivation or necessity after securing ourselves at the top of the pile? Thanks! EDIT 1; I aoplogise for oversimplifying the truth by saying we're at the top of the pile. My (now) more refined question is... I'm unaware of the timescales involved but let's talk about the half way point from the previous homo-species to the current homo-sapiens, how and why did we get there? And how and why did we get to be homo-sapiens?
|
[
"Stephen Jay Gould wrote about this. We evolved survival skills that apparently required our large brains, the ability to write symphonies and do quadratic equations was a byproduct of this large brain, not the purpose of it."
] |
[
"As was said by KevZero, the driving force behind all evolution is genetic variation and to add to that, mutation. The traits we possess today are a result of fitness within the environment as driven by those mutations. As with every creature, the more offspring you have, the higher your evolutionary fitness. You mentioned, 'Our competition with fellow humans is surely not fierce enough?' I would certainly have to disagree with that statement. Competition within your own species in terms of genetic fitness is exactly how a species evolves."
] |
[
"Every [eukaryotic] organism alive today is descended from the same ancient, primitive ancestor. Therefore, every organism that is alive has survived and reproduced just as successfully as any other. Humans are ",
" ahead at all. We're not the most plentiful by number of individuals, nor by biomass. We ",
" almost certainly the most noticeable.",
"We ",
" compete with other species, but we've solved a lot of the problems our ancestors faced by using our most successful adaptations: a nice amount of social coherence, cleverness, and the ability to pass knowledge from one generation to the next (culture and language). It's very rarely these days that a wolf or shark kills a human; it's more often the other way around. So, why do we keep evolving? Why don't we just freeze? Because genetic variation exists among our species' 7 billion members, and it keeps creating differences in reproductive advantage from in each successive generation. Where will it go? Nobody knows."
] |
[
"How do injuries in the mouth heal themselves?"
] |
[
false
] | null |
[
"Just like other injuries to the body, platelets aggregate to the site and clot together, and prevent any additional bleeding from broken vessels of the injury. Leukocytes travel to the affected tissues, starting the inflammatory process, and then white blood cells kill bacteria and clean up dead cells.",
"Injuries to the mouth heal much faster than other parts of the body, because it accelerates the inflammatory and healing processes. The mouth contains saliva and salival exosomes rapidly accelerate the clotting process. Saliva also contains histatins, peptides that are rich in histidine. Histatins have antifungal and antibacterial properties and play an important role in wound closure. In the mouth, a large amount of histatins are secreted from the salivary glands in the back of the tongue.",
"",
"The mouth heals basically heals the same way any other part of the body would, but it has special properties that allow it for a much shorter healing time, one of the factors being histatin, which is important in wound closure."
] |
[
"Essentially, yes. Rather than spitting, evolutionarily speaking, humans have an instinct to suck on their finger if they cut it; 'wound licking' is an instinctive response that is found in humans and many other animals. However, for humans, it is not really advised to spit or suck on major wounds because the bacteria found in the mouth is relatively harmless but when exposed to injuries on other parts of the body, it can lead to an infection."
] |
[
"Why is the bacteria safe in your mouth but dangerous in wounds. Is it the direct contact with your blood?"
] |
[
"Does the human heart really generate an electrical field?"
] |
[
false
] |
I've heard this come from self-help types and wondering how much merit it has. They say that every time you have a thought, a "pulse" of electro-magnetic energy is generated at the base of the heart. This smells of bullshit to me, but for all I know it could be true.
|
[
"... every time you have a thought, a \"pulse\" of electro-magnetic energy is generated at the base of the heart...",
"What!? The heart is not responsible for thinking! Whoever wrote or said that in whatever self-help book/seminar is spreading complete and utter balderdash.",
"However, the heart ",
" generate a detectable electrical potential, which is the basis behind ",
"electrocardiograms",
". It does not have anything to do with thought, and everything to do with keeping a rhythmic contraction to circulate blood around the body."
] |
[
"Indeed! It doesn't make any sense for the body to evolve the kind of function that these people are proposing. Their tactics are transparent: Show videos with nice music and lovely images, pepper them with pseudo-science, get them to shell out thousands of dollars for books, CDs, seminars, camps, et cetera. It's so dishonest that I just want to pull their hair out."
] |
[
"I wonder how they explain Dick Cheney, who apparently no longer has a heart beat due to ",
"his heart being replaced with a continuous pump",
". "
] |
[
"How do credit card chips work?"
] |
[
false
] |
How do credit card chips work differently than the magnetic strips? Why can the credit card chip not be intercepted by a scammer and be reproduced while the magnetic strip can?
|
[
"Basically the chip is a computer. The magnetic stripe is a piece of data.",
"The terminal can ask the chip to perform a computation on a number, without the chip ever revealing the secret keys used to the terminal. This is called a cryptographic signature."
] |
[
"The chip alone prevents usefully cloning the magnetic stripe, and magnetic stripe cloned card fraud is currently a much bigger problem than when the card itself is lost or stolen. So the chip alone is a large improvement. If you want to prevent lost or stolen cards from being used, that's when the PIN comes in but for whatever reason, US banks have decided to focus, at least for now, on transitioning to the chip and continue using signatures for most credit cards (there are a few issuing chip and PIN cards), and debit cards also mostly work like before where you sign if you choose \"credit\" or enter a PIN if you choose \"debit\"."
] |
[
"Yes, and no. In your example, you're assuming a dynamic/secret algorithm or function. (your 5(x",
" What's actually going on is the card has a known algorithm, and the secret portion is a number that also factors into that algorithm. The mathematics behind cryptography are extremely complex, but the long and short of it is that even if you have a copy of the input and output, you can not derive the secret information other than randomly guessing. ",
"So yes, the security all boils down to the security of that secret number on your card, but the card is designed to make extracting it extremely difficult physically, and unless there is a previously unknown flaw in the implementation of the card's firmware or processor, there's no way to extract it electronically."
] |
[
"Has Folding@Home really accomplished anything?"
] |
[
false
] |
Folding@Home has been going on for quite a while now. They have almost 100 published papers at . I'm not knowledgeable enough to know whether these papers are BS or actual important findings. Could someone who does know what's going on shed some light on this? Thanks in advance!
|
[
"Unequivocally, yes.",
"I do drug discovery. One important part is knowing the molecular target, which requires precise knowledge of structural elements of complex proteins. ",
"Some of these are solved by x-ray crystallography, but Folding@Home has solved several knotty problems for proteins that are not amenable to this approach.",
"Bottom line is that we are actively designing drugs based on the solutions of that program, and that's only the aspect that pertains to my particular research."
] |
[
"Alzheimer's. ",
"Here's",
" the reference. That's from J Med Chem, which is the workhorse journal in my field.",
"Drug development usually takes at least ten years from idea to clinic, and Folding@Home was only launched 12 years ago.",
"Edit: If you have questions about Alzheimer's drug discovery, I just did an AMA ",
"here",
". "
] |
[
"So what are some drugs that have been developed or are being developed, thanks to F@H? Also, what are those drugs treating?"
] |
[
"What substance/element/thing has the highest melting point and how did we manage to find out what it was?"
] |
[
false
] |
Wouldn't it melt anything touching it first? Would it be done using magnets to keep it from touching something else (if magnetic) or possibly in space where there is no gravity?
|
[
"Tungsten is the element with the highest melting point -- more information here:",
"http://www.newton.dep.anl.gov/askasci/phy00/phy00914.htm"
] |
[
"Carbon does melt under the right conditions. The melting point of a substance depends on both temperature and pressure. A phase diagram of carbon can be seen ",
"here",
". As you can see, at pressures above 100atm, carbon will melt from a solid to a liquid if the temperature is high enough. ",
"Perhaps the OP didn't know enough about materials science to specify a pressure range in the question. I suppose it's fair enough to assume 1atm when no pressure is specified, but it's also fair enough to expand on other answers by discussing materials that remain solid at high temperatures."
] |
[
"Carbon stays solid at higher temperatures",
":",
"Carbon sublimes in a carbon arc which has a temperature of about 5,800 K (5,530 °C; 9,980 °F). Thus, irrespective of its allotropic form, carbon remains solid at higher temperatures than the highest melting point metals such as tungsten or rhenium."
] |
[
"Why don't power plants store energy mechanically?"
] |
[
false
] |
A big problem with wind and solar energy is that they are not consistent. Why not store this energy mechanically? By say pumping water up vertically. Also, what are the best ways to store energy mechanically for personal home use with solar and wind?
|
[
"This technology is already in widespread use"
] |
[
"The relatively low energy density of pumped storage systems requires either a very large body of water or a large variation in height.",
"I guess this is why it isnt more common. "
] |
[
"Using any storage medium means introducing inefficiencies into the process. If you generate X amount of power, then store it mechanically, you can only get say 75% out of what you put in."
] |
[
"Length of a \"horizon to horizon\" jet airplane contrail?"
] |
[
false
] |
What is the length in miles of a jet aircraft's continuous contrail if it flies directly overhead at 30,000 ft altitude?
|
[
"2 * (radius of earth+30,000 ft)*arccos(radius of earth/(radius of earth+30,000 ft))"
] |
[
"If you're 6 ft tall then it's about 6 miles longer."
] |
[
"2 * (radius of earth+30,000 ft)*arccos(radius of earth/(radius of earth+30,000 ft))",
"Assuming the Earth is a perfect sphere and that you are 0 ft tall."
] |
[
"Do each of my chromosomes come from a specific grandparent or are they all a mix of genes from each?"
] |
[
false
] |
I know I have 23 chromosome pairs, 23 from my mother and 23 from my father. But is my 1st chromosome a match to one of my grandparents 1st chromosome or does it have a mix of genes from all of them? If it's matching chromosomes, does that mean I get ~12 Maternal Grandmother Chromosomes ~11 Maternal Grandfather Chromosome from my Mother and similarly from my Father? And then on back through them ~5-6 from each of my great-grandparents, ~2-3 from each great-great, ~1-2 from great-great-great, ~0-1 from my great-great-great-great, etc. So does that mean if I pick an ancestor 6 generations back, I probably don't share any chromosomes with them? Does that mean I wouldn't be any more genetically related to most of my 128 great-great-great-great-great-grandparents than I am to anyone else from that generation, since I only have 46 chromosomes only 46 of them could have contributed a chromosome to me?
|
[
"The chromosome 1 you got from your father (similarly mother) is a mix of the two versions your father has of that chromosome. Importantly, it's not a random mix, but a \"recombination\": if we represent your chromosome 1 as a vertical stick, the bottom segment would derive from one of your father's chromosome 1's, and the top segment from his other chromosome 1. The split can happen anywhere, not necessarily in the middle.",
"Because the two chromosome 1's of your father were given to him by his own father and mother, it means that the two segments of your paternal chromosome 1 correspond to your paternal grandfather and grandmother.",
"If we go deeper it gets a bit trickier. Your paternal grandparents also had two versions of chromosome 1 (total 4 chromosome 1's for your two paternal grandparents), of which your father's two chromosome 1's are recombinations. You could have inherited segments from two, three or all four of the chromosome 1's of your paternal grandparents, depending on how the segments were randomly created over two generations (where recombination happens). But because the process is independent for each of the 23 chromosome pairs, you'll still get chromosome bits from each of your grandparents.",
"The further back you go in your ancestry, the more recombination happened, and the smaller the segments inherited from a particular ancestor become, on average (note that there are more and more ancestors). The point is, chromosome versions get broken up at each generation, so what is passed down isn't entire chromosomes, but segments of them.",
"Regarding bonus questions:",
"There are numerous ways to mathematically measure ancestry. There are techniques that model the process above, but I think the most commonly used ancestry models at the moment don't explicitly do that. Though they do rely on the fact that you're bound to inherit a little bit of almost all your ancestors, even the distant ones.",
"Non-African populations have chromosome segments that correspond to their Neanderthal ancestors. Those segments are small since the Neanderthal ancestors are very far back (I mean, Neanderthals went extinct some 40,000 years ago) but the total length is about 2% of the genome (on average, and not everyone has the same segments).",
"If someone famous is your ancestor you'll most likely have inherited some genes, so it should be possible. That said, relatedness is very tricky. If you're willing to go back far enough, you'll find that everyone is related to everyone, just because everyone starts having so many ancestors."
] |
[
"Chromosomes are all shuffled and mixed during reproduction! It's called ",
"genetic recombination",
". So each of your chromosome is a mixed of the ones of all your ancestors combined!",
"With the exception of your Y chromosome if you're male, as you only get your Y from your father... so you have the same Y as your father's father's father's father's father... (not exactly tho, some recombinations with the X still happen, but it's limited). From mother's you get the mitochondria (with its own DNA). These two are called haplogroups and allow to trace the maternal lineage and the paternal lineage!",
"But to answer your question, then no, chromosome aren't transmitted as it. They got recombined and you can have in your chromosome 9 (for example), a fragment of a gene on the top part that comes from your father who got it from his mother who got it from her mother... and just after it, the rest of the gene comes from a DNA fragment from your mother who got it from her mother who got it from her dad... it's all randomised!",
"If you pick any ancestor 6 generations back, you won't have any chromosomes being exactly the same as one of yours, but you'll have 1/64th (1.56%) of DNA in common with that ancestor spread all over your chromosomes!"
] |
[
"This isn't totally accurate. Recombination happens during the production of gametes, not during actual reproduction. You receive maternal and paternal chromosomes separately, but these do not physically mix in your body except when you produce your own eggs or sperm. While it's correct to say that any given chromosome has a mixture of all your ",
" or ",
" ancestors, you won't find paternal and maternal DNA on the same chromosome. So your chromosome 9 example is only possible if looking at gametes, not somatic cells."
] |
[
"If light shines on an object, does the object reflect more light as the intensity increases?"
] |
[
false
] |
Let's say we start out with a not very intense beam of light, the object then becomes brighter because of the light. If we were to increase the light intensity, would the object increasingly reflect more light due to it's increasing brightness? The whiter an object gets, the more reflective it becomes, so does that also apply with brightness?
|
[
"In general yes. For classical reflection of light off of an effectively planar chunk of homogeneous material, the amount of reflected light is given by the ",
"Fresnel equations",
". The reflection coefficient in these equations is defined as the reflected power over the incident power, which basically assumes that there is a linear relationship between incident power and reflected power (what you call the \"brightness\"). This means that if the light hitting the object is made twice as bright, the light being reflected will be twice as bright.",
"Note that the classical description of reflection breaks down in a lot of situations, so that it gets more complex:",
"If the incident beam is bright enough, it can induce the object to respond non-linearly, so that there is no longer a simple linear relationship between incident and reflected fields.",
"If the incident beam is bright enough, it can permanently change the object (e.g. burn it, vaporize it, ionize it)",
"If the frequency of the beam is high enough, a material no longer acts like a homogeneous material, but instead acts like a collection of atoms, leading to complex behaviour such as x-ray diffraction. "
] |
[
"If I am interpreting your question correctly, the answer is no. The reflectivity of an object is in general not changed by the amount of light you're shining on it. Of course the object looks brighter to you, because the total intensity of the reflected light increases when you increase the incoming power, but that does not change what percentage of the light is reflected by it."
] |
[
"Unless you change it, an object always reflects the same fraction of incident light. E.g., for a fresh coat of silver, the fraction is around 95%, depending on the quality of the process.",
"The ",
" remains the same. But the ",
" of reflected light increases with the brightness of the source."
] |
[
"Ask Anything Wednesday - Physics, Astronomy, Earth and Planetary 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!
|
[
"The effect of the pull will travel through the material with the speed of sound as well. On your end, you pull on molecules close to you that in turn will pull on the next molecules, etc... While the action is different from banging the rod, the effect is the same.",
"Since these actions all appear to instantly affect the entire object in real life situations, the notion of the pulling effect having to propagate through the object seems strange. But if you'd be able to measure with sufficient accuracy, you'd see the same effect when pulling a small rod (",
")."
] |
[
"A student asked me this once, and I couldn't give a reply that really convinced me.",
"\"Suppose I manufacture a rod that's, I don't know, 5 light years long. If I bang it with a hammer, the signal will propagate with the speed of sound and reach the other end. But what happens if I just grab it and pull? Haven't I just sent information faster than light?\"",
"What should I have told the kid?"
] |
[
"Asked this question in another thread but it got lost. If I'm looking through a telescope at an object thousands of light years away I understand that the scattering of protons means that my resolution of the image is going to be limited by the size of my lens and how many protons I can capture and focus. ",
"My question was is it theoretically possible to be so far from an object that there are blind spots in the proton scattering where you simply would not be able to detect an object without being in a precise location(i.e. move 6cm to the right and it appears, but 6cm to the left and it's gone). I understand that this may mean light had to travel further than the age of the universe, but could it happen?",
"I figure it has something to do with the wave/particle duality nature of protons, but that raises other questions like are you observing the same proton in multiple locations at the same time? "
] |
[
"What is the scientific consensus on free radicals?"
] |
[
false
] |
[deleted]
|
[
"Others have given an answer to your question, but I want to address the idea of \"scientific consensus.\" Please remember that science is not in the business of locating truth -- that territory is reserved for religion.",
"In science, ideas are always open to further investigation, and theories are always open to falsification by new evidence. This means \"scientific consensus\" is nothing more than opinions by people who will most likely be proven wrong over time, and the more time, the more likely they will be proven wrong. In case you think I'm exaggerating, I will let a well-known scientist say it for me:",
"\"Science is the organized skepticism in the reliability of expert opinion.\" — Richard Feynman"
] |
[
"http://www.cancer.gov/cancertopics/factsheet/prevention/antioxidants"
] |
[
"Thanks. I'll give that a long read through."
] |
[
"Is there an evolutionary, biological, or other definitive reason why the left side of the brain controls the right side of the body, and vice versa?"
] |
[
false
] |
From what I understand, the medulla oblongota (brainstem) connects the spinal cord to the rest of the brain. Here, the nerve tracts cross from left to right, and right to left. So, nerves controlling the left side of the body are found in the right side of the brain, and nerves controlling the right side of the body are found in the left side of the brain. Is there any specific reason for this? Or is it "just because" (which in and of itself is a rarity in science).
|
[
"Contralateral central nervous control may be an evolutionary consequence of dependence on the image-forming eye, especially in large organisms. As a result of the topological transformation of the visual stimulus in the pupillary eye, the external environmental hemispace impinges directly upon the contralateral internal organismal hemispace.",
"EDIT: I am constantly downvoted for \"simplifying\" so, there you go. "
] |
[
"Yeah, I'm still pretty confused :/"
] |
[
"So, basically what you said is that it has to do with how our eyes look at things upside down?"
] |
[
"What do Titan's liquid methane seas actually look like?"
] |
[
false
] |
I've been asked to visualise the oceans of Titan, one of Saturn's moons - but can mainly find others' sci-fi renderings, nothing based on how light actually behaves. Would the oceans also have ice-blocks etc? For example, is its refractive index as a liquid, would it be perfectly transparent etc?
|
[
"Liquid methane is colorless. Even more colorless than water, which is ever so slightly blue. Based on its gas phase absorption spectrum shown ",
"here",
", methane's electronic absorptions lie in the far-UV or in the infrared region. In the liquid phase, absorption peaks tend to broaden out, so you might see a very faint green color due to a very small amount of red light absorption.",
"About the ice, the density of liquid methane is significantly less than that of ice, so you're not going to see icebergs floating around. At those temperatures, ice is just another rock."
] |
[
"\"We can't rule out some exotic type of life that doesn't need water, but it's unlikely based on what we know.\"",
"What do we know that makes it unlikely?"
] |
[
"On the surface of Titan or in its methane/ethane lakes, probably not. Life as we know it requires liquid water, and Titan's surface is far too cold for that. We can't rule out some exotic type of life that doesn't need water, but it's unlikely based on what we know.",
"However Titan, like many other moons in the outer solar system, appears to have a liquid water ocean under its ice. It might be possible for life to exist there."
] |
[
"Is the sun soft or hard?"
] |
[
false
] |
To give an example; if I was flying a spaceship (let's assume it can withstand the extreme conditions), and I wanted to enter the sun, would the ship just sail through or would it crash on the surface?
|
[
"To use your terminology, the edge of the Sun is rather soft. Take a look at ",
"this graph of the matter density profile of the Sun",
". Close to what we usually take to be the edge of the Sun, the density is about 10",
" g/cm",
". This density is comparable to the density of our atmosphere on Earth at ground level. However, as you go deeper and deeper the density rises, until you get to the core where densities are on the order of 10",
" g/cm",
", which is about 10 times as dense as bulk gold. ",
"Of course, like you say this doesn't mean you have any chance of sailing through anywhere close to the core. The temperature is already thousands of K at the edge of the Sun and ",
"quickly rises until it reaches more than a million K near the core",
". If that wasn't enough, you also have to deal with some ",
"utterly crushing pressures",
". For example, close to the core, pressures rise upwards of 10",
"Pa, a pressure higher than what you may find at the center of the blast of a thermonuclear warhead. Needless to say no material we could dream up could withstand these conditions. ",
"Sources: The graphs are from ",
"here",
" and the orders of magnitude from ",
"Wikipedia"
] |
[
"If you read the Sci-fi series \"The Golden Age\" by John C Wright, they discover the \"Island of stability\" actually exists and create entirely new elements. They create a star ship to do exactly that, sail into the core of a star. It's a great series: ",
"http://www.amazon.com/The-Golden-Age-John-Wright/dp/0765336693"
] |
[
"The author of the website appears to be particularly motivated, but deluded. He seems to think the sun has a solid calcium ferrite surface, and spends many paragraphs pointing out why NASA is \"wrong\" about their interpretation of satellite images of the sun and the like.",
"While I don't have time to go into it in detail, he has plenty of \"sources\" but they often don't actually support what he tries to use them to say. I'd trust NASA and the entire body of research on this topic over this one website.",
"Edit: As an example: Look at the ",
"tsunami page",
". The author says ",
"we observe highly rigid and angular structures which retain their three dimensional shape over the course of many hours ",
"with respect to a movie on the page. But he then posts the text of an email he got from a Stanford professor regarding the movie, which included the quote ",
"These images are Doppler shift of the spectral line Ni 6768A. The Doppler shift measures the velocity of mass motions along the line of sight. The darker areas show the motions towards us, and light areas show flows from us. These are not cliffs or anything like this.",
"This means, among other things, that the area he circles as retaining its shape is actually moving around throughout the entire video- if it were staying in the same shape it would have a uniform color. ",
"That's just one example. More generally, consider that he's disputing research results from many prominent scientists. It's never impossible that a whole field misinterprets results for long periods of time, but it doesn't happen often. If you find a mistake such as this that you're correct about, however, you don't spend your time making a website about how everyone else is wrong.",
"You write a paper, get it peer reviewed, and get it published. This website's author has done none of these things."
] |
[
"Can someone plainly explain how claims that the Pfizer and Moderna mRNA vaccines can promote prions be refuted?"
] |
[
false
] | null |
[
"This is a paper written with the same layout as a \"real\" scientific publication but it's just not... real.",
"For one, just FYI, PubMed doesn't index this journal and it's listed among known predatory journals. A good thing that's happening in publishing is open access publishing. A lot of journals now make papers available to everyone... at the cost of the author paying to publish. A small number of upstart journals have taken advantage of this to charge for publication without any review of the content they're publishing. Many times authors think their work is being peer-reviewed and edited, in other cases (likely such as this one) they're just paying someone off to get a publication on their CV.",
"Furthermore, read the methods section yourself. Unfortunately, the methods sections of most papers are lacking in detail and do not have enough information to replicate the research. This, on the contrary, has literally no information. There is no description of how they analyzed anything. RNA and protein structure prediction are complicated and will involve use of nameable software tools. (EDIT: Here's a ",
"paper predicting secondary structure of mRNA",
" for stability purposes in vaccines; pay attention to the difference in level of detail in the methods section...).",
"Beyond that, the actual results are just predictions about the structure of the RNA in the vaccine. RNA is heavily regulated in the body by RNA binding proteins, a metric shit ton of them. Some proteins that misfold and form pathogenic aggregates in neurodegenerative diseases happen to normally play a role as RNA-binding proteins. The papers they cite state that these proteins tend to bind to some structures present in the vaccine RNA (they're not very complex structures/sequences, and they'll be present in your own RNA). This binding is part of the protein's normal role in the body. Nothing in anything they cite indicate that these interactions are involved in the development of misfolded protein aggregates. The tendency of some RNA-binding proteins to form aggregates is likely inherent to the role of prion-like domains in their natural structure in the formation of protein complexes within which they carry out their normal roles. The idea that RNA induces this misfolding is an invention of their own that they never actually cite sources for."
] |
[
"Good questions.",
"Another poster addressed the prion question very well. As for the pathogenic priming/immune enhancement thing: the easiest answer is we would have seen that in clinical trials, and we did not. Both MRNA vaccines greatly reduced the number of symptomatic cases. Among those that had the vaccine and still got COVID, the cases were more mild on average. If immune enhancement were a risk here, the opposite would have happened. Even though it was quick, the vaccines were looked at very carefully, and the scientists would have seen any problems like you describe.",
"I did a quick google search, and found some sources claiming that these problems were seen in the vaccines. The only sources I saw making that claim were not real medical sources, and did not cite real medical sources. At that point, it is basically just someone making it up - not much different than a youtube comment. All of papers from real scientists and doctors on these things says they are very safe and effective."
] |
[
"Thank you for your reply. I suspected as much after looking at the method section, but thought maybe their reasoning or logic wasn't just solely theirs. I wasn't able to keep up with the topic in their cited sources myself so your explanation is reassuring (unfortunately all I know on RNA/DNA is from high school)",
"*edit: also those pay-for-publishing schemes are wild, never knew it was this easy. Just looked it up, no doubt about it, low quality. Thanks for bringing that to my attention"
] |
[
"Evolution speeding up?"
] |
[
false
] |
How long does it take for a evolution to take place and for a mutation to select itself in a community? Kevin Kelly states in his 2010 book, What Technology Wants, "We are not the same folks who marched out of Africa. Our genes have co-evolved with our inventions. In the past 10,000 years alone, in fact, our genes have evolved 100 times faster than the average rate for the previous 6 million years." Source:
|
[
"The pace of evolution depends on evolutionary pressure. Creatures well adapted to a static environment can remain largely unchanged for millions of years. But when that environment is altered, evolution can occur much more quickly. It has to, because creatures who can't evolve perish.",
"I don't know about Kelly's numbers, but the environment humans live in has change radically over the past 10,000 years. It makes a lot of sense that the pace of evolution would have accelerated adapt to it as well."
] |
[
"It may also depend on complexity. Complex organisms may very well respond differently to the environment.",
"http://en.wikipedia.org/wiki/Timeline_of_evolution",
"Single-cell organisms took their sweet time before they did anything different. Then multicellular life just exploded.",
"Within multicellular life, they just existed as worms and such tiny critters again for a long time, and then the Cambrian explosion happened, and things got a kick in the pants again.",
"And so on and so forth.",
"I think the OP is right, it's just the scale that is wrong. At the highest scale, yes, there is a noticeable acceleration at every major step."
] |
[
"Kurzweil wrote a book on this. Specifically that, among other things, evolution was essentially \"speeding up\", or more accurately that the time between salient events is directly related to the amount of chaos in a system. This certainly isn't well accepted science, and I'm almost regretting posting it in ",
"/r/askscience",
", but it is interesting, and it's not entirely impossible. ",
"This review",
" does a great job explaining the theory Kurzweil introduces in ",
", the Law of Time and Chaos. He then expands on that theory and explains that Moore's Law is a generalization, that it isn't just transistors on chips that doubles every few years, but more accurately our computational ability as a whole.",
"Again, it's not mainstream science, but if you want an interesting read on the subject, I recommend his book, at least check out that linked summary, it's very relevant to what you asked."
] |
[
"Why does my breathing dramatically change when I go from taking a hot to a cold shower?"
] |
[
false
] |
I usually take a cold shower for about 30 seconds when I'm done taking a hot shower (for about 10 minutes) and I've always wondered why my breathing always drastically changes when the water gets cold. Is it like a shock to the body?
|
[
"It's likely ",
"part",
" of the ",
"diving reflex",
". Basically, your body wants to conserve oxygen when it thinks you're going to be underwater for a while. It slows your heart and constricts your blood vessels."
] |
[
"Maybe it has something to do with ",
"this?"
] |
[
"More than you'll ever want to know:",
"http://www.jappl.org/content/100/6/2057.full"
] |
[
"Could technologies like CRISPR eventually be able to change a person's sex and/or turn a person into an entirely new species of human after the changes have propagated through the entire body?"
] |
[
false
] |
I've watched a few interviews, TED talks and debates about CRISPR and in them they've said that it can be used to change an organisms DNA while the organism is still alive and the changes are permanent and 100% hereditary ( ). CRISPR supposedly can alter several genes at once, is re-programmable and is easy to use. What are the limits of CRISPR-like technologies?
|
[
"Sounds like those TED talks oversimplified the situation.",
"However:"
] |
[
"You seem very reactive for all thread concerning CRISPR",
"Yeah no kidding. People have been asking about it a lot recently, and it's probably better that someone try to give them real information on the topic than let imaginations potentially wander off into misconception-land.",
"is Cas9 able to access condensed DNA ?",
"Yeah, apparently!",
" Doesn't seem to be a really significant loss in efficiency. Pretty impressive...",
"Isn't there a problem concerning the specificity of CRISPR ?",
"This paper",
" came out earlier this year, and basically showed that a variant of Cas9 can result in pretty much zero off-target cuts.",
"but for a 20 bps long sequence to guide it",
"Yeah, 20 bps. You're looking for a site that has [5’-20nt-NGG] or [5’-CCN-20nt] (as in, the PAM also adds specificity). While there is a chance that you could accidentally target the CRISPR to multiple sites, you're supposed to check the genome to make sure your site is unique. Generally, there is more than one site per gene that you can design your sgRNA for."
] |
[
"Mostly no.",
"In scifi shows you'll see DNA changing and a dude will change into a lizard (ST TNG: Genesis) which is absurd.",
"Very much of what you are is driven by genetics, but those things happen as you grow from a sperm-and-egg into an adult. The genes that made those changes are ",
" as an adult and changing them would do nothing."
] |
[
"Could we keep an isolated brain alive with modern technology?"
] |
[
false
] |
I have recently discovered the concept of an isolated brain and have read through the wikipedia article. There were a few experiments in Soviet Russia during the 1940s. Has technology advanced enough for this to be plausible? Provided we could, would the brain operate as normal or would it require the body to function? Could the "Brain in a Jar" be achieved?
|
[
"So if you provide it with both those things, would the person be conscious? Would they be in pain or would you just be stopping cell death but the brain would stop functioning?"
] |
[
"A brain just needs oxygen and nutrition to my understanding.",
"If it's in a jar, there isn't really anything stopping you from giving those things, as long as the concentration is higher on your side so they diffuse in.",
"I don't know why you would want a brain in a jar though. I think they're much more useful in bodies."
] |
[
"I don't know, this is a question I've never thought about before.",
"Since it's detached from most of the nerves it is normally attached to, there would likely be pain in the same way the people with missing limbs hallucinate pain.",
"I think they would be conscious. The brain in the body is just sitting in a cavity surrounded by CSF which has nutrition in it and attached to blood vessels to get oxygen. Do the same thing in a jar instead of a skull and I imagine the brain would be conscious."
] |
[
"What does it mean by 'virtual' in QED explanations?"
] |
[
false
] |
I am researching quantum electrodynamics while I'm in my Quantum II class at University. I have been looking at Feynman Diagrams for a little while to understand how they work. There was a note that any line that starts and ends inside the diagram is a virtual particle, i.e. virtual photon in the electron-electron repulsive exchange force. I know we measure photons and their properties (optics, qm, e+m), are these measured photons different from the virtual photons or am I being mislead by the title of 'virtual'? Thanks for your help
|
[
"Virtual photons are just a calculational tool. They are not a real thing. One way to see this is that there are ways to formulate quantum field theory that do not use virtual particles at all (e.g., lattice gauge theory).",
"Here's another way to see this. Take any photon you can actually observe, measure its energy and momentum, and you will find they are proportional to each (with constant of proportionality ",
", the speed of light). For a virtual photon, the energy and momentum do not satisfy this relationship, which means they are distinct from physical photons.",
"In perturbation theory, the physical photon is neither an external photon line nor an internal photon line; it is the sum of all the processes that start with an external photon line and end with an external line, summing over all possible intermediate diagrams. Of course, perturbation theory isn't the whole story, so the physical photon is really a bit more than this, but hopefully that picture helps."
] |
[
"Since you're in a quantum 2 course, I can tell you exactly how they're a calculational tool. You've probably learned perturbation theory, and you've learned that the first order correction is just the expectation value of the perturbation, <H>. However, the second order correction to the nth energy level takes an interesting form:",
"Σ",
" (<n|H'|i><i|H'|n>)/(E",
" - E",
").",
"That is, you consider the overlaps of all other states |i> with the initial state |n> and sum over them all. These are the \"virtual\" transitions: you can view the matrix elements in the numerator as the initial state |n> suddenly virtually becoming the state |i> via the interaction and then transitioning back. Then you sum over all such intermediate states. Importantly, each term in the sum contains an energy denominator, so states closest in energy contribute the most.",
"In QFT things get more complicated, but the same similar structure happens, and the intermediate \"virtual states\" look more like intermediate \"virtual particles.\" Of course, if you could solve the whole hamiltonian H",
" + H' to begin with, analytically or numerically, these virtual transitions would never appear, so virtual processes just appear in perturbation theory."
] |
[
"Are they the same as virtual work in mechanical/civil engineering terms then? We pretend there's a virtual particle and see what it would do if it were there, and at the end it cancels itself out?"
] |
[
"Is there any sort of concept of a genomic efficiency, i.e., is there any benefit to having a higher ratio of coding DNA to junk DNA?"
] |
[
false
] |
Is there no sort of penalty for carrying around all that non-coding DNA?
|
[
"A lot of non-coding DNA is functional. There are classes of functional non-coding RNAs, such as micro RNAs, as well as regions of the genome that are never transcribed into RNA but still play a role in the regulation of transcription of other parts of the genome.",
"That being said, smaller genomes are selected for in certain circumstances because more energy is required to replicate a larger genome. The extra cost is comparatively small, which is why we don't see genomes being kept as small as possible across all life. Birds, as an example, have notably smaller genomes than other vertebrates, and it's believed this is because of the high amount of energy required for flight. ",
"It should be noted, though, that genetics/genomics is a fast moving field and new technologies are constantly being invented that allow to look at things differently. It may be that all genomes are as small as possible and everything has some function that we don't yet understand. Since the regulation of genes by enhancers (one of the functional non-transcribed areas I mentioned earlier) is done through moving the enhancer region close to the gene in physical space, then some stretches of DNA in the genome may be there just to allow the genome to twist and fold more freely, enabling more dynamic regulation. We have a lot left to learn about what's going on inside the cell."
] |
[
"This is certainly a consideration for small, quick-replicating organisms like viruses or bacteria. In both cases, their population growth (and thus their fitness) is limited in part by how fast they can replicate their DNA. Since longer genomes take longer to replicate, there's a strong pressure for short, efficient genomes. In viruses, this can lead to really tricky genomes with lots of ",
"overlapping genes",
"."
] |
[
"Just to add about viruses. One of the strategies they use to keep their genome small is bu using a very small number of structural proteins. Most viruses have one main protein that makes up the capsid, and it is simply arranged in a repeated fashion that produces capsids with ",
"quasi-icosahedral symmetry",
". By way having a very small number of unique structural proteins, as well as hijacking the replication/transcription/translation machinery from their hosts, viruses can keep their genomes very small"
] |
[
"If many electron systems are unsolvable, how do we know the orbital shapes?"
] |
[
false
] |
I have not taken physical chem or differentials (does it show?) so some math concepts might be over my head. I know we have a good understanding of orbital geometries and orbital hybridization for valence electrons at least in organic chem. At the same time I have heard that for atomic systems of greater than 2 electrons certain equations that have to do with wave functions in quantum mechanics become unsolvable. Can someone explain how those can both be true. Also before those atomic resolution images, were molecular orbital geometries experimentally determined (if so how?) or just predicted by quantum?
|
[
"\"Analytically\" means solving an equation exactly, in terms of elementary functions, like you would by hand. This is as opposed to solving an equation numerically, which is using a computer to find an approximate solution.",
"The Schrodinger equation is a complicated equation in all but the very simplest circumstances, meaning you wouldn't be able to solve it by hand. But just because you can't write down an exact solution doesn't mean a solution doesn't exist - it does, you just need to find an approximation to that using a computer."
] |
[
"OP, I would just like to ad that most (all?) electron orbital shapes you see in textbooks are actually the shapes for the one electron problem, which, of course, is analytically solvable. ",
"That is to say, the 1s, 2s, 2p",
"{x,y,z,z",
", x",
"-y",
"}, etc etc are all the shapes they would be, ",
". ",
"Check out ",
"https://en.wikipedia.org/wiki/Hydrogen-like_atom",
" for more information"
] |
[
"Well, you can still solve the Schrodinger equation for your system numerically, if not analytically.",
"But of course, at some point this strategy fails terribly when your system is too complicated.",
"This is when you will need to use various approximations to help you simplify your system. Maybe you don't need the exact shape of the orbitals, you might be sufficiently happy to know qualitatively what they are like. Or maybe you give up using wavefunctions entirely and focus on something else, such as the electron density. Or maybe only one part of the molecule needs to be calculated in great detail, and the rest can be kind of glossed over. Or perhaps you know from some experiments that your system has to satisfy certain properties which allows you to simplify your calcuations. And so on. You can use a bunch of tricks to turn a very hard problem into a tractable one and in the process extract a lot of important chemical information. Part art and part science."
] |
[
"Are there any effects of brain hemisphere lateralization?"
] |
[
false
] |
I read this in my consumer behavior textbook. Is the information accurate? Does brain lateralization have any effects on behavior? I am weary to believe anything of brain lateralization after learning that left/right brain personality theory is not necessarily true.
|
[
"This is mostly a bunch of hooey. People have a mix of personality traits and abilities that are not so simplistically dependent on a hemispheric laterality."
] |
[
"There is a lot of baloney on this subject, and I believe the whole 'dominant side' is unfounded. ",
"I went through some of my books to find the exact info on it:",
"The left hemisphere controls the right side of your body, the right hemisphere controls the left side of your body. Your trunk muscles and facial muscles are controlled by both hemispheres, as an exception. Vision doesn't work per eye, but per visual field, this is crossed as well (so your left field of vision get processed by the right hemisphere). Taste and smell are uncrossed. Hearing is shared, but slightly stronger for the contralateral ear. ",
"The left hemisphere is dominant for speech for more than 95% of right handed people. Most of left handed people have left hemisphere dominance for speech as well, but some for right, or mixed.",
"\nThe right hemisphere is more dominant for recognizing emotions in others and has better spatial abilities. Regarding vision, it also attends to overall patterns, while the left hemisphere focuses more on details. ",
"Sources: Biological Psychology, James W. Kalat, 11th edition.",
"\nPsychology, Peter Gray, 6th edition."
] |
[
"Yes, because we are about 97% left brain hemisphere dominant for language/speech, we are right handed. using the right hand selectively for writing, shaking hands, eating, and many other tasks, which also makes us largely right visual field dominant, is probably the most important brain hemisphere characteristic dependent series of behaviors known. "
] |
[
"How efficient is chlorophyll at light absorption? And how does it compare to modern-day solar pane light absorption?"
] |
[
false
] |
I'm trying to wrap my head around how much light is actually utilized for energy by plants and if our solar panes can absorb more or less energy from incoming solar light. Not sure if this can be best described in percentages or along the lines of frequencies in the electromagnetic spectrum - but either will be very helpful!
|
[
"There is a complication in your question. Most energy efficiency comparisons don't look at raw energy absorption. They also remove overhead from operation. You'll see this for plants and solar cells. For solar cells, there is some overhead which costs power. If you have a pane with the capability of 100% absorption, but it has to use 90% of that to operate, it's really no better than the one that gets 25% absorption and has to use 60% of that to operate. I'm going to adhere to that standard for the most part. If you want to talk about raw input without overhead, let it be known.",
"The theoretical max for photosynthesis is ~25% ",
" to 30%. ",
" Most plants operate at ~32% efficiency on that amount (due to the chemical conversions). However, plants have to consume that energy to survive. That drops them to ~0.5% up to ~8%. The efficiency depends on the plant's consumption. Check out the sources below for more specific details in that regards. ",
"The efficiency basically boils down to the following losses.",
"Solar cells are more complicated and there are a ton of them out there. Rather than walk through them all, I'll state the max is at 43.5% efficiency. I recommend you check out the massive chart with their efficiencies. ",
"http://en.wikipedia.org/wiki/Photosynthetic_efficiency",
"http://hyperphysics.phy-astr.gsu.edu/hbase/Biology/ligabs.html",
"http://en.wikipedia.org/wiki/File:PVeff%28rev120820%29.jpg"
] |
[
"I can't comment on the math but I have a nitpick; it's typically D-glucose, not d-glucose, though you aren't strictly wrong. "
] |
[
"And what difference does capitalization make in this case?"
] |
[
"If a breastfeeding human female eats an exclusively non carbohydrates diet will she still be able to produce milk?"
] |
[
false
] | null |
[
"Mmmm. Well, I would have to say that yes, a mammal can still produce milk. I'm sorry, I don't have any citations, but look at predator mammalian species who subsist on an almost exclusively protein diet. They have no problem nursing their young, and the physiological mechanisms behind neoglucogenesis remains the same. ",
"As well, in the vast portion of human history we have not had ready (regular) access to carbohydrates. Some cultures like the Aleut live almost wholly without them. ",
"ETA: neoglucogenesis means we ",
" make glucose from fats and proteins."
] |
[
"I'm pretty sure that carbohydrates (unlike fats and proteins) are not essential nutrients. As in a zero carbohydrate diet might be suboptimal, and might also have negative long term side effects, but it's not going to cause any sort of short term malnutrition. Do you have a cite?"
] |
[
"The body produces milk from fat stored in the body; as long as caloric needs were met for the duration of the pregnancy (from fats or carbs) the mother should be able to produce milk. Now I'm not 100% sure if glucose is required for milk production, but if it were I'd believe that gluconeogenisis would cover those needs."
] |
[
"Is there a difference between hurricanes, cyclones, typhoons, medicanes and tropical storms? If not, is there a reason other than the place where they form for the name difference?"
] |
[
false
] | null |
[
"Atlantic and pacific storms are called hurricanes.",
"Storms in the ",
" Pacific are called Hurricanes, while storms that form in the ",
" Pacific are known as Typhoons. Storms forming in the Indian Ocean as well as the ",
" Pacific are referred to as Cyclones."
] |
[
"It’s just where they are formed. Atlantic and pacific storms are called hurricanes. Storms off the coasts of Asia are typhoons. And storms in the oceanic region are cyclones. Never heard of medicanes before. All of them will downgrade to a tropical storm though."
] |
[
"I just learned about medicanes this week because one is hitting Greece today with 60-90 mph gusts. They're rare..\n ",
"https://m.accuweather.com/en/weather-news/medicane-to-bring-heavy-rain-strong-winds-to-southern-greece-western-turkey/70006195"
] |
[
"How does altitude and topography affect the gravitational constant on earth?"
] |
[
false
] |
I understand the inverse square law but I want to know more about what happens when we make no idealizations. This all started as an argument between me and my brother, me saying that is smaller at higher altitude simply because of the inverse square law and him saying that it's not the inverse square law that takes precedence but instead that gravitational anomalies take precedence (i.e which had the caption "Red shows the areas where gravity is stronger than the smooth, standard value, and blue reveals areas where gravity is weaker."). Looking at that gif leads me to believe I'm completely wrong and that the gravity on Everest would be greater than sea level but I'm having a really hard time with that because all I've read and been taught is that gravity decreases as the inverse square of the radius where we can model the Earth as a point at its centre of mass. Are we not able to make this assumption in this case?
|
[
"If you want to make no idealizations, it is not really correct to call g a \"constant\" because it varies with distance from masses. Gravitational forces between objects depends of 3 things 1) the mass of object 1 ,lets call this you. 2) the mass of object 2, lets call this earth, and the distance between them. Consider the idea that \"the earth\" does not exert a gravitational force on you, but instead every atom that makes up the earth exerts some small force on you that is proportional to the three factors mentioned above. That being said, it follows that the force due to gravity is not the same everywhere on earth. Lets say at point a on the earths surface, the ground is very dense. This will cause a stronger gravitational force to be exerted on you than if you were at point b ( a place where the ground is not very dense) because you are closer to more mass. The force of gravity is represented by this equation F=G(m1)(m2)/(r",
" where G is a constant, m1 and m2 are the masses of the two objects being observed, and r is the distance between them. It follows that the force exerted on a person 10m away from a 100kg object and 100m away from a 10kg object is not the same as the force exerted on a person 100m away from a 100kg object and 10m away from a 10kg object (assuming one dimension). ",
"Lets assume the example of a person standing on top of Everest. Lets say for simplicity that all of the mass that you are standing on top of will add to the gravitational force that you experience ( because the mass of the mountain will exert a gravitational force on you) and that your increase in elevation ( in other words, your distance from the earth) will cause a decrease in the gravitational force that you experience from the rest of the earth. I cannot say for certain that the magnitude of the force added to the gravitational force you normally experience due to your proximity to the mass of the mountain will be more than the difference of gravitational force caused by your increase of distance from the rest of the earth, but if that is the case, then you will experience a higher gravitational force on top of Everest. "
] |
[
"Yes, and on the scales of neutron stars and black holes you need to dip into general relativity to fully describe these gravitational interactions. But for less exotic objects like stars and planets Newtonian gravitation works just fine."
] |
[
"There are two corrections that have to be made",
"First your correct for the altitude at which the measurement is made:\n",
"http://en.wikipedia.org/wiki/Free-air_gravity_anomaly",
"Then you correct for changes in topography:\n",
"http://en.wikipedia.org/wiki/Bouguer_anomaly",
"It seems to me that the GRACE map you found is 'free air', which accounts for the altitude of measurement (the altitude of the GRACE satellite), but does not take into account the extra mass of high topography!"
] |
[
"In ISS time lapse video, It says \"aurora australis over Madagascar\". Can this be true?"
] |
[
false
] |
According to my knowledge about auroras, they are created by the magnetic fields forcing particles form solar winds down around the poles. Surely Madagascar is not south enough to have aurora australis? The video can be seen at 2.02 at this link:
|
[
"Doubt Nasa? I would think that it is perfectly okay to question to caption on a video when I find a dissonance between it and what I thought I knew. I was doubting myself more than NASA. But thanks for the answer anyway. I discussed it with a friend who said that the aurora can be seen further north (or south in borealis) when you see it from space, and that I couldn't believe. So we found that video and he thinks its confirming his theory."
] |
[
"I find it odd that your immediate reaction is to doubt NASA. Pretty ssure they know what they're about.",
"The most important bit of info you're missing is the existence of the \"South Atlantic Anomaly\", it's almost like a hole in the Earth's magnetic field, or another pole. At it spreads from South America all the way to the edge of Madagascar. The SAA is most likely responsible for the existence of aurorae near Madagascar despite it being at only 20 deg. S latitude."
] |
[
"It's actually quite common that during geomagnetic storms during which solar winds are more active than normal, that the auroras can extend to lower latitudes, going as far north as Australia, New Zealand and also Madagascar. So this particular footage shows a quite rare, but not unheard of kind of aurora."
] |
[
"What kind of protection do memory T cell stored in bone marrow provide, compared to neutralizing/sterilizing immunity?"
] |
[
false
] |
There’s lots of discussion around the vaccines providing the best source of sterilizing immunity, but what protection could be provided from these memory T cells from natural infection and the following convalescent immunity? And do vaccines also provide this same type of immunity, or only sterilizing immunity?
|
[
"Vaccines provide antigens, which are pieces of a bacteria or virus (pathogen) that your immune system can recognise and use to trigger an immune response. The main actors in this part of the immune response are the B cells and the T cells. ",
"B cells make antibodies which bind to the antigen, and depending on what the antigen was it can directly interfere with the pathogen. Using the COVID vaccine as an example the antigen that is introduced is the spike protein that allows the virus to enter cells, so antibodies against the spike protein can stop the virus from getting into the cells and replicating itself. This can be a bit hit-or-miss though, as there are lots of different places on the spike protein that the antibodies could be binding to and not all of them will prevent the virus from being able to enter a cell. The exact antibodies your body will make against it are determined at random.",
"T cells have a different job - they kill cells that are infected with the virus so that they don’t keep making more virus. They don’t stop the virus getting in, but if they can get to an infected cell early enough they can kill it before it releases the virus to its neighbouring cells. This process is a bit more of a sure bet because it doesn’t require having the exact right antibody - any piece of the virus will do as infected cells will present random virus pieces on their surface.",
"Both cell types create memory cells, which are B and T cells that hang around after you recover essentially keeping a record of which antibodies were used to fight that infection in case you get infected again."
] |
[
"I think it would be difficult to tell whether the a T cell response on it own would be better than a B cell response on its own because it would be difficult to get an isolated T cell response in a living human. The T cell response is often involved in activating the B cell response, so the two systems feed into each other and work best together."
] |
[
"The symptoms are a combination of the damage the virus is doing to your body and your body engaging your primary immune system to fight it off. The primary immune system involves things like fever, coughing and sneezing which your body does to try and suppress the pathogen or expel it from your body while your cellular immunity learns to fight it. ",
"It takes a few days to mount a proper cellular response the first time you encounter a pathogen, but once you’ve had a cellular response and you’ve got your memory B and/or memory T cells it takes much less time, so you can clear out an infection before it has time to cause much damage and give you any major symptoms. ",
"Sterilising immunity means that your body is able to completely stop the virus from replicating. It’s a product of the B and T cells working together. The COVID vaccines don’t quite provide this, especially against the delta variant which replicates much faster, but it helps your immune system mobilise much faster so that the virus can’t cause as much damage before a full sterilising immune response can be mounted, so it protects against the most serious symptoms. That’s why people who have had the vaccine can still test positive for the virus but they’re much less likely to need to go to the hospital or die from it."
] |
[
"Could we in theory create Saturn style rings around the Earth, for shits and giggles."
] |
[
false
] |
If I recall correctly the rings around Saturn are supposed to be caused by a moon or something that exploded and all the pieces and rocks and ice circling it and forming what appear to be rings. Would it be possible to do the same thing to Earth, intentionally, how would we go about this? And would there be any negative consequences (I'm pretty sure that there'd be enough of a gap between the surface and the rings for it to not interfere with satellites or planes or anything)
|
[
"By constantly do you mean every few hundred thousands years or so?"
] |
[
"Could adding artificial rings to Venus be used to cool it and aid in terraforming, potentially anyway?"
] |
[
"Could adding artificial rings to Venus be used to cool it and aid in terraforming, potentially anyway?"
] |
[
"When neutron stars collide do they immediately form a black hole or would the collision produce ejecta?"
] |
[
false
] | null |
[
"This would depend heavily on initial conditions. While models do predict that neutron stars can spin fast enough to deform their shape, I have read little about how much mass escapes a merger, however, one paper I read did propose a method for calculating this, you can find it ",
"here",
". Based on their calculations, depending on initial conditions, anywhere from 0.27*10^-2 to 3.15*10^-2 solar masses (pulled out of their table, so the actual range is likely greater).",
"Last year LIGO had the first confirmed detection of a binary neutron star merger, and a gamma ray burst and optical component followed some hours later.",
"For some sauce here are some simulations run by the SXS collaboration, they do modeling that is used to look for signals in the LIGO data.",
"binary neutron star merger",
"black hole neutron star merger"
] |
[
"Neutron stars are made up of a form of degenerate matter, in this case, neutron degenerate matter, though it is expected that they have an iron crust on the surface. Ejected degenerate matter would quickly go through a series of violent reactions once free from the neutron stars gravity, resulting in a spray of decay products.",
"By the way, when I say violent, I mean that a cubic centimeter of neutron degenerate matter would yield roughly 500 billion megatons when allowed to decompress. In fact, the ejecta of merging neutron stars or a nuetron star and a black hole is believed to be the source of kilonovae."
] |
[
"Their state of matter is only stable with the intense pressure in a neutron star. Everything that is ejected leaves as regular matter (probably as extremely hot plasma based on the energies involved in these processes)."
] |
[
"How has the amount of water on Earth’s surface changed over geologic time?"
] |
[
false
] |
Is water being subducted into the mantle faster than it’s being out gassed back out? Has the Earth experienced any net loss of water to space?
|
[
"This is a major ongoing question in geology, that I hope to do a PhD project on. ",
"Korenaga et al., 2016",
" came up with a net decrease of water on earth's surface over time, with almost a quadrillion gallons of water going down into the mantle per year."
] |
[
"The lightest elements (Hydrogen and Helium) can escape the Earth's atmosphere because they are light enough to get occasionally whisked away into space. So can some light molecules. ",
"On human timescales, there is a tendency to think of an atmosphere as being\nas immutable as a planet’s rocks, but over geological time, gases can leak from the\ntop of the atmosphere and escape to space. Fortunately, for the modern Earth, loss\nrates are tiny even for the lightest gases: about 3 kilograms per second of hydrogen\nand 50 grams per second of helium. But in the last few decades, we have begun to\nappreciate how the very existence of an atmosphere depends as much on escape as\nsupply. In particular, the atmospheres on terrestrial planets and outer planet satellites\nare like the ruins of medieval castles, remnants of riches that have been subject to\nhistories of plunder and decay. Atmospheres of small planets are more like crude\nforts, poorly defended and extremely vulnerable. For decades people have pondered\nhow the smallness of Mars might be responsible for an atmosphere only one\nhundredth as dense as Earth’s—but a consideration of escape makes us wonder why\nMars has any atmosphere at all. Odd puzzles also exist for larger terrestrial planets.\nHow did Venus steadfastly cling to a thick atmosphere yet thoroughly lose its water?",
"To escape, atmospheric gases must attain escape velocity, which is the\nminimum needed to overcome gravity. One way that this can happen is when gases\nget too hot to hold on to—so-called thermal escape. Escape can also occur through\nnumerous “non-thermal” processes, where individual atoms or molecules get an\nenergy boost from chemical or charged particle reactions. A third, completely\ndifferent process, is when air is blasted away by asteroid or comet impacts.",
"https://geosci.uchicago.edu/~kite/doc/Catling2009.pdf",
"I'd expect nearly all the water lost from Earth over the past few hundreds of millions of years to have escaped this way. That is broke down into hydrogen and oxygen by natural processes on earth then the hydrogen finds a way to escape. IIRC H2O can also escape in specific circumstances but its far less than simple hydrogen atoms."
] |
[
"I thought it was now fairly well accepted that the Earth’s oceans are slowly being lost to the mantle over time? (Though not quick enough to mean an end to any life before the sun boils the oceans away mind) ",
"Are there any significant objections to this line of thought?"
] |
[
"A question regarding colors and wavelengths."
] |
[
false
] |
Do different shades of one color have different wavelengths? For instance, does light blue have a different wavelength than dark blue? or is the difference just the amount of light waves/particles hitting one's eyes?
|
[
"Short answer: yes, they'd have a different spectral response.",
"Long answer:",
"http://i.imgur.com/SNJXdOT.png",
"The above image is a conceptual plot of all the colours that can be rendered by the human eye. The triangle in the middle represents the colours that can be reproduced by a computer monitor (likely sRGB). ",
"If you follow the locus on the outer edge, you can see all the colours which can be produced by different wavelengths. However, the colours on the outer edge are not typically found in nature as they are composed of a very narrow band of wavelengths and are something you'd most likely see from a laser source. Almost all other light sources are broadband and are composed of multiple wavelengths. A blue, green or red LED usually will have a bandwidth on the order of 10nm to 50nm. Some gas discharge lamps will usually have a few narrow contributors which depend on the energy states of the elemental electrons in the gas. And incandescent and fluorescent lamps typically have broad spectra which will span across the entire visible spectrum (400nm to 700nm) and well beyond into the infrared.",
"TL;DR Light is pretty fucking cool and can get complicated really quickly.",
"EDIT: If you look at the graph you'll notice there are no numbers between red and blue (i.e. purples, magentas) and this is because these do not exist as pure colours in the sense that they're composed of only a single narrow band of wavelengths but rather exist as a combination of a red source and a blue source."
] |
[
"It is a different wavelength. Dimness and brightness are the differences in intensity."
] |
[
"The chart is a visual representation of what is known as CIE 1931 color space. Wikipedia has an interesting article about how it's defined and how to undergo various transformations to different color models such as RGB. ",
"Scientists have experimentally determined (to some extent) how the cones in our eyes decode colour information and have developed what is known as LMS colour space. LMS, stands for long, medium and short wavelengths. It's been observed that we have three types of cones in our eyes which are sensitive to different colours of light. ",
"It's also been observed that humans are most sensitive to green light, specifically 555nm, under normal illuminant conditions. This mean that if you have a green, red and blue laser of equal energies, the green laser would appear to be much brighter to the human eye. In low-light conditions, peak sensitivity occurs under blue-green light at 498nm. These two modes are referred to as photopic and scotopic vision."
] |
[
"How would a person standing on the North Pole feel the effects of the earth's rotation?"
] |
[
false
] |
[deleted]
|
[
"Standing on the equator, you are moving at a whopping 1670 km/h around the center of the Earth. You don't feel this. ",
"Standing on either pole, you are stationary relative to the center of the earth. You are merely rotating very very slowly (0.0007 rpm). You are absolutely guaranteed not to feel this."
] |
[
"They wouldn't. ",
"There are two forces that appear in uniformly rotating frames - the Coriolis force and the centrifugal force. ",
"The Coriolis force depends on the direction you're moving - it's produces the apparent motion of 'the earth rotating under you' when you move. If you're standing still this force is zero. ",
"The centrifugal force is the 'thrown up and out force' and is greatest at the equator, but zero at the poles.",
"Thus, someone at the north pole wouldn't feel earth's rotation. They could, however, still see the rotation from the motion of objects in the sky, like the sun and stars. "
] |
[
"That and the fact that gravity would be weaker near the Equator due to the equatorial bulge makes about a .5% difference in weight between the two.",
"Source: ",
"http://curious.astro.cornell.edu/about-us/42-our-solar-system/the-earth/gravity/94-does-your-weight-change-between-the-poles-and-the-equator-intermediate"
] |
[
"How do the particles not escape the HADRON collider?"
] |
[
false
] | null |
[
"Their paths are constrained by magnetic fields."
] |
[
"Ion optics. Electromagnetic fields are used to steer and shape the beams how they desire."
] |
[
"Much stronger than common toy magnets, but typical ion optical field strengths are around a few Tesla. The strongest man-made magnets in existence that I know of have max continuous field strengths of around 50 Tesla."
] |
[
"What happens if the beta decay of a diproton into deuterium is unsuccessful?"
] |
[
false
] |
Do the two protons go back to being sole protons? How do they get back the energy that they lost earlier through gamma radiation when fusing into a diproton ? Does the star's core have any way of giving it back to them? If not what happens then?
|
[
"The diproton almost always decays to two protons. The beta decay to a deuteron has a very small branching fraction.",
"How do they get back the energy that they lost earlier through gamma radiation when fusing into a diproton ? ",
"They don't."
] |
[
"Can those protons fuse into diproton again? If not, what happens to them from there on?"
] |
[
"From this point they're just protons like any other, they have no \"memory\" of their previous diproton state."
] |
[
"Do the bacteria in our stomach become resistant to antibiotics over time?"
] |
[
false
] |
If we are creating antibiotic resistant bacteria that can infect us, I was wondering whether our microbiome would also become resistant.
|
[
"There are no bacteria in your stomach (unless you are infected with ",
").",
"For the most part, there are no bacteria in your small intestine either, as the forward motion of the muscle lining (peristalsis) keeps them moving forward toward the large intestine.",
"There are colonies of bacteria in your large intestine though. To get to your question, the answer is definitely ",
" your intestinal bacteria (flora) can be affected by and become resistant to antibiotics. Sometimes you get an intestinal overgrowth of a \"bad\" bacteria (not really \"bad\" unless they overgrow) when the \"good\" bacteria are killed by taking antibiotics (another reason to avoid antibiotics unless absolutely required). One example of this is a ",
" colitis (aka ",
") which can cause severe abdominal pain, bloating, and diarrhea... which also requires antibiotics to treat.",
"But, in general, your gut bacteria can (over time) develop resistances to antibiotics which can cause further problems down the line, given enough time and enough exposure to antibiotics... this process can be accelerated by the improper administration of antibiotics or a failure to fully follow the regimen enough times."
] |
[
"You're looking to learn about \"horizontal gene transfer\". There are a lot of ways it can happen. Wikipedia, as usual, is a good place to start: ",
"https://en.wikipedia.org/wiki/Horizontal_gene_transfer#Mechanism"
] |
[
"On antibiotics. You either take it all and more if that didnt do the trick or you take none at all. "
] |
[
"If I had a spherical glass vacuum in a zero-g environment containing some rubber balls, shook it, then left it free-floating, would the balls ever completely stop moving inside it?"
] |
[
false
] |
[deleted]
|
[
"Some of the energy is going to dissipate because the collisions are not perfectly elastic.\nEvery time the rubber balls strike each other or the glass container some small component of the momentum is going to be lost.\nThe loss of energy is going to be due to some inelastic process, like friction between each ball or ball and glass after collision.",
"There is no way to say explicitly where the balls will stop, but they will stop working when they all reach constant velocity, with their velocity vectors pointing in the same direction and having the same magnitude as the glass case.",
"Remember that \"rest\" is when there are no external forces acting on a body, or more explicitly the body maintains constant velocity.",
"So when there is some difference between the magnitude of the velocity, or the direction of the velocity, or both for any component- this means that there will be a collision at some time in the future.\nWhen all are equal, then there will be no further collisions.",
"The time it will take to equilibrate will depend on the inelasticity of the collisions.\nThe final position will most likely be touching the glass itself, since there is no air friction to slow the balls to stopping in the middle of the glass.\nHowever one cannot explicitly say whether they will be arranged in some stack along the edge (so that some touch the glass, but others will only be touching other balls), or spread out touching in some pattern where each has a nearest-neighbour ",
" touches the glass. Or even if they will be spread around with no nearest neighbours, but touching the glass.\nOr if there are several clusters that forms stacks in different locations.",
"EDIT: Finished my sentence"
] |
[
"Why would they stop because a gravitational force is acting on them?"
] |
[
"Ok, step by step now:",
"Because they all will have a constant force pulling them in towards a singular point.",
"So far so good. Let's ignore for a moment that gravity is not actually a force in order to keep it simple. The ball in the container is accelerated towards the wall by the \"force\" of gravity. At the moment before it hits the wall it has gained some amount of kinetic energy relative to the box. Where does this energy go when it hits the wall and just stops moving like you suggest? ",
"Unless you projected the glass ball with enough force to maneuver through multiple gravitational fields it will just be orbiting a single body. ",
"I don't really understand what you are trying to say here. Could you rephrase it for me?",
"Now the time it takes for that force to bring them all to rest my seem relatively high. Could be a year could be a decade. That's all dependent on how close they are to the gravitational body and how fast they are bouncing about. ",
"Same here. Could you elaborate on the point you are trying to make? "
] |
[
"Is there a limit to how small black holes can get? Also, are singularities all the same size?"
] |
[
false
] |
I was browsing , when a thought occurred to me: Is there a physical limit to how small a black hole can be? I understand that the event horizon is no measure for the size of a singularity, but could a black hole exist with an event horizon on the scale of planck lengths? I know that really small amounts of matter have been used before to create black holes, such as LHC and [RHIC]( ), but how small can they get? I was also wondering, are all singularities the same size? Do we know about this? Would [NCG 1277] (mcdonaldobservatory.org/news/releases/2012/1128.html) have the same size singularity as the ones made at RHIC? If so, how big are they? Thanks for any answers. Posted from a phone, sorry of the hidden links are broken.
|
[
"I know that really small amounts of matter have been used before to create black holes ",
"This is not true. The link you give points to a discussion that explains RHIC cannot produce an actual black hole. See ",
"http://www.bnl.gov/rhic/blackHoles.asp",
". Neither LHC nor RHIC nor any other accelerator has produced a black hole.",
"It is possible small black holes were formed in the primordial universe, but there is no known mechanism by which small black holes would be produced today."
] |
[
"If black holes emit Hawking radiation, then a black hole will emit more than it absorbs from the cosmic microwave background if it is smaller than about the mass of the moon. However, as far as we know black holes are formed from collapsing stars, and stars much be much larger than the sun for this to occur.",
"Singularities aren't physical phenomena, but rather problems with our mathematical description of physical phenomena. The fact that the way we describe black holes has two singularities (one at the edge and one at the centre) means that our understanding is incomplete. The one at the edge goes away with the right choice of coordinates, but the one at the center is a problem."
] |
[
"Thank you for referring to the singularity as a mathematical issue rather than a physical object. Most descriptions I see treat them as if they are real physical objects and I think that causes a lot of misunderstandings."
] |
[
"If every person were to stand at equal distance apart from each other on earth, how far apart would we be?"
] |
[
false
] |
[deleted]
|
[
"Let's just take land area and neglect the polar icecap (additional area) and areas which would be hard to stand on like cliff terrain etc. (subtracted area)",
"The land area of the earth is ",
"~150 million km",
". The world population is just under 7 billion (google).\n",
"\nSo dividing the area by the population you get ~0.02 km",
" per person which is about 20'000 m",
" Take the square root of that to get the length of the side of the square the person i standing in (which should also roughly be the distance to the next person): I get 140 meters (~400 feet).",
".. hmm that seems very short so feel free to check my calculations.",
"edit: also check out this",
" wikipedia link",
" on population density"
] |
[
"It's actually impossible to stand on a sphere with more than 20 people with exactly equal distance to each other. ",
"I know this sounds counter intuitive, but if it were possible there would be more platonic solids. The ancient greeks figured this out already. "
] |
[
"How much difference will it make to the distance between hexagonal packing and just putting them in the suboptimal squares I've described below? (Not criticizing, just wondering how large that effect is and since you brought it up, you're probably more apt at making that calculation than me.)"
] |
[
"Cocaine and tobacco residues found in Egyptian mummies, does this indicate trade with the Americas?"
] |
[
false
] | null |
[
"http://www.faculty.ucr.edu/~legneref/ethnic/mummy.htm"
] |
[
"[Citation Needed]"
] |
[
"You should update your post to post the findings that you are referring to so others can share :)"
] |
[
"Why do people die instantly of heart failure? Shouldn't there be some time you're still alive while your brain is suffocating from lack of fresh oxygenated blood?"
] |
[
false
] | null |
[
"They do not, many many people have been resuscitated after the heart stops beating. You will lose consciousness within a short time of the moment it stops beating (similar to losing consciousness from being choked - lack of oxygen to the brain), but you are not dead immediately thereafter.",
"That is just what happens in movies."
] |
[
"That is just what happens in movies.",
"To add my two cents, a fact that they always insist on getting wrong in the movies is the use of a defibrillator. They show it as a way to resuscitate someone's stopped heart but that's not it's function at all; desfibrillators are used to return a dysrhythmia (ventricular fibrillation to be precise) to normal sinus rythm, not to restart a heart."
] |
[
"In fact, you could make the case that the defibrillator's role is not to start, but to ",
" the heart.",
"You use it in ventricular tachycardia and fibrillation, which are \"rhythms\" where an electrical pulse goes haywire or where every muscle cell fires more or less randomly. The defibrillator delivers a powerful shock that resets all the cells at once, returning control to the natural mechanisms (usually the sinoatrial node)"
] |
[
"Why does my radio get beter reception when I have my hand on it?"
] |
[
false
] |
Am I acting as like a flesh antenna or something?
|
[
"Water does not conduct electricity very well. The minerals in it do. "
] |
[
"Basically, yes. Here's a couple articles on it:",
"http://www.thenakedscientists.com/HTML/content/qotw/question/2448/",
"https://www.scientificamerican.com/article.cfm?id=why-does-moving-your-hand",
"And a similar question:",
"http://www.reddit.com/r/askscience/comments/se5et/when_i_tune_my_radio_it_sounds_alright_but_the/"
] |
[
"Most of your body is water, water conducts electricity, boom, antenna."
] |
[
"Do brain training games actually improve your cognitive ability?"
] |
[
false
] |
[deleted]
|
[
"The closest I can come to commenting on \"brain games\" in general is some of the research around the Brain Age games: people don't necessarily get \"smarter,\" but they do get better at Brain Age.",
"\nI remember reading in Wired way back when (quick google search finds this:",
"link",
") which found that students who played Brain Age frequently showed improved test scores in math than students who didn't play the game. Keep in mind that improved math scores doesn't necessarily mean improved brain functioning. It could simply mean that these students got better at the math skills being tested for.\nThe study did also find that these students felt more confident in their math skills, which might explain the comments you saw. Those \"alumni\" saw distinct improvements in their performance at the brain game tasks, which led to an increased sense of confidence in their abilities in the outside world -- regardless of whether those abilities actually improved or not.",
"\nIn short, there's no clear evidence that these types of exercises improve mental acuity in a way that translates to \"smarts\" in the real world. There is some evidence that they can help slow down the impacts of again on brain functioning, but that requires you to do these types of activities over a several-years' span, at which point you might as well start picking up sudoku."
] |
[
"There's evidence that ",
"n-back tasks",
" can increase test scores on Raven's Progressive Matrices. Whether Raven tests are a good indicator of IQ is arguable, although schools and high IQ societies do use it to vet candidates."
] |
[
"There is some evidence that the placebo effect can remain even if the subject knows its a placebo. But the placebo effect isn't truly understood."
] |
[
"What would happen if sea levels DROPPED?"
] |
[
false
] |
We always hear about the social/economic/environmental problems and side effects of worldwide rising sea levels, but out of curiosity, what would one expect if the opposite was true? How would things change if sea level dropped, say, 10-20 metres. More, if that's more interesting. Thanks in advance! Edit: thanks everyone for the thought out and informative comments, dnd setting inbound ;)
|
[
"Well ... it happened before, of course, and within the previous few hundred thousand years no less ... litterally within human memory, during the last ice age. The Lascaux paintings are documentary evidence from that time period.",
"Just as global warming leads to rising sea levels as the ice caps melt, global cooling is the mechanism linked to sea level decrease and growing icesheets.",
"When the last glaciation was at its height the area between Alaska and Kamtchatska was above sea level, and formed a landmass known as Beringia. Sea level went down 100 meters relative to the present. The ancestors of American Indians and Inuit crossed that land bridge on foot, as did a lot of wildlife that went either East or West. The shores of southern Spain and France were covered by subarctic tundra-like vegetation, and the icesheet reached all the way down to Central Park and Wisconsin.",
"And the effects of a climatic regime where such a sea level decrease would occur would be those of going back to a global ice age ... much of currently inhabited Europe, Asia and North America would become uninhabitable, as 2-3 kilometer thick icesheets came thundering towards the equator (geologically speaking). Areas amenable to agriculture would shrink due to a shortened growing season. Inhabitable areas would migrate closer to the equator, and shrink. Economies would collapse, massive socio-economic disruptions, extinctions, possibly our own, would occur ... yadda yadda yadda, as they say... it would be apocalyptic."
] |
[
"Putting aside the climate effects required for a sea level drop, every major harbor in the world would now be high and dry--or at least have problems working at anything close to their original capacity--so much of world trade would be interrupted, and you could see regional famines resulting."
] |
[
"OTOH, wouldn't the Sahara be \"wet\" (i.e. grassland) again as it was during the neolithic subpluvial?",
"Edit: thanks to all the folks who dropped knowledge below--learned a lot!"
] |
[
"AskScience AMA: I'm a biologist who studies stress and reproduction in large whales, sea turtles and other species. I'm at the international marine mammal meeting right now in New Zealand. AMA"
] |
[
false
] |
[deleted]
|
[
"The most common is actually shipping noise, and the most common high-volume noise is seismic exploration. Those never seem to get as much press as military sonar. A lot of my funding is specifically to look at effects of military sonar and yet it's clearer with every study that shipping noise and seismic exploration are much more pervasive problems. Shipping noise is really difficult to study because it's so common you can't get a decent \"unexposed\" control group. (For my species the only time shipping really got shut down was during 9/11, probably the all-time best example of an \"unplanned experiment\". We were on the water that year in the Bay of Fundy and found the right whale's fecal glucocorticoid - stress hormones - levels dropped after 9/11 that year, presumably because of reduced ship traffic after the ports were shut down, and didn't drop in any other year.)",
"Seismic exploration is another one I really worry about. Something that really came clear at the meeting this week is the phenomenal amount of high-volume seismic exploration that's being planned off practically all the continental coasts and all through the Arctic. All the southern right whale teams are reporting massive ramping-up of seismic plans throughout most of the southern oceans, and they're scrambling to get baseline measures now before it hits. (Also the Arctic is really getting blasted with nosie - and Canada laid claim to the North Pole a couple days ago btw - Arctic mineral rights is really politically hot right now.) Seismic exploration blasts are up to 240dB (caveat: dB measurements are different in water than in air, but that's still very loud)",
"Most threatening factor overall: Right now it's entangement in fishing gear, plus deaths due to shipstrike - a HUGE number of whales die due to these 2 things. (most mortalities in NA right whales are due to those 2 factors). Entanglement really gets overlooked (plus it's a horrific way to die, really an inhumane thing to do to an animal). Long term though I'd pick climate change and associated shifts in prey base. NA right whales pulled completely out of their usual foraging grounds this year, corresponding with an all-time high in sea surface temp in the Gulf of Maine and a steep drop in food availability, and I expect we may see that sort of thing become more common."
] |
[
"Thanks for the AMA! 2 questions:",
"What have your studies found to be the most common source of ocean noise? ",
"What is, in your opinion, to be the most threatening factor to the whales' habitat? "
] |
[
"Funny you should bring this up because the N. Atlantic right whales, and all the right whales, are kind of famous for their reproductive organs and repro behavior. They don't seem to suffer any erectile dysfunction though - partly because the right whale penis works quite differently - (a) like a lot of mammals they have a penile bone and not the same sort of erectile tissue that the great apes have, and (b) the end is prehensile and they can steer it. ",
"The way it works is, they congregate in these huge bunches of whales called \"surface active groups\" (SAGs) with 1 female upsidedown in the middle, and dozens of males around her jockeying for position, also upsidedown, with these penises waving in the air around her sort of probing her trying to find the right opening. (yes, this is as hilarious to see as it sounds). It seems it's sort of a challenge for the male - only the biggest, most skilled male can push his way next to the female, hold position, hold his breath while upsidedown and also find the right opening on the female, especially when there's another male on the other side also trying the same thing. Anyway they also congregate in all possible combinations of ages and sexes - we've seen all-male groups, males sticking their penises into each other, adults with calves, everything. I have to also mention that they have the longest penis and biggest testes of any mammal in the world, both in terms of absolute length and in terms of % of body length and body mass. (The penis on an adult male is about 9 feet long, the testes about 6 feet long, each weighing about 1000lbs.) ",
"SAGS are our best time to get respiratory vapor samples because they pay no attention to us at all. My most memorable moment at sea was being in flat calm water looking for whales, not knowing there was a SAG of 26 animals ",
" underneath the boat. All 26 suddenly popped up all around us, all basically just a few feet away. (every one of those 26 was bigger than our boat)",
"Anyway the thing we really worry about is lack of calves. All joking aside, something is seriously wrong with calf production. During the 1990s the right whales almost completely stopped producing calves. They were still showing lots of sexual activity (edit: there's a puzzle about the location of the mating grounds, and the time of conceptive mating, that I will not get into), yet no calves were showing up. A lot of females never produce a calf at all; a lot of others produce 1 and then quit entirely (we call them the \"one and done\" females). That's when I got involved - I was brought in to basically help develop the first pregnancy test for large whales, to try to figure out if they were losing the calves, or just never getting pregnant at all. We're starting to think that those females might be chronically stressed, especially the ones who have been previously entangled in fishing gear or struck by ships. They tend to take a long break between calves if they've had an entanglement."
] |
[
"Why is it impossible to have a correct 2D map of the earth?"
] |
[
false
] |
[deleted]
|
[
"Because a sphere has non-zero intrinsic curvature and the plane has zero intrinsic curvature. You can't isometrically (preserve angles and distances) move from one to the other because isometries preserve curvature."
] |
[
"try to lay an orange peel flat on a table. it will have bumps or it will break. "
] |
[
"No matter how much you break it it will still not be 2d."
] |
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