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[
"Does a beer's 'head' slow the release of carbon-dioxide?"
] |
[
false
] |
I just did the Heineken brewery tour in Amsterdam (good stuff) and heard a claim that I don't quite believe is true. Since the carbon dioxide increases the freshness of the beer, a good 'head' of foam would slow the release and thus maintain a pint's freshness. Not sure I can believe this... does a CO2 molecule coming out of solution on the bottom of the glass "know" that there is a barrier at the top of the glass, and therefore tend not to come out of solution? Is the foam even a barrier at all?
|
[
"I think it's plausible. The most important factors for carbonization are gas solubility and surface tension. Carbonated beverages are typically bottled at higher pressure, so they are already oversaturated in CO2 at normal atmospheric pressure, which causes the beverage to foam up in the first place. Since the relatively high surface tension in the head captures the CO2, eventually it reaches a temporary equilibrium where the CO2 in the beverage only sees the high-CO2 bubbles in the head, instead of the low-CO2 air. Sort of a ",
"partial pressure",
" problem."
] |
[
"The bubbles would form a barrier (not impermeable, but less permeable than air) to the CO2. What i'd be concerned about is that those bubbles are there due to increasing the surface area of the pour, and allowing CO2 to form bubbles in the first place. I wonder if the investment is worth the saving?"
] |
[
"I wouldn't quite say that the head slows the loss of carbonation from the beer as much as it IS the beer losing CO2. Head is formed when CO2 bubbles out of solution, which is caused by the principle ",
"Xenneract talks about",
". As the gas bubbles through the liquid, it causes the rise of proteins and other residues in the beer from the hops, grain and yeast to form a foam at the top of the glass, trapping some of the CO2 in bubbles. So while you could say that head keeps CO2 in your glass, it's keeping it as a foam on top rather than in the liquid component of the beer. "
] |
[
"How do binary star systems form?"
] |
[
false
] | null |
[
"Binary star systems form just like any other star would, except the end result is two stars.",
"Normal star systems form when a gas cloud begins to condense and heat up. As it condenses and heats up, it begins to spin faster and faster in order to conserve its initial angular momentum (the radius shrinks and the mass remains constant, so the velocity increases) Most of the matter goes into the star, which forms spinning, while the rest forms into a spinning gas and dust cloud around the star. ",
"In a binary star system, the collapsing gas and dust cloud would form into two distinct high density parts (rather than one high density part that would result in the formation of a single star). The two parts as a whole would maintain angular momentum and orbit around each other. They would begin to condense and heat up, until two distinct stars were formed like ",
"this",
" (In short, something causes the protostellar gas cloud to split, forming two distinct stars)",
"This might also help",
"It's up for debate what specifically causes a gas cloud to fracture into two shapes, but we know that it's the fracturing that leads to the formation of binary systems.",
"As for the exact reason the gas cloud would form into two separate parts, that I don't know, but ",
"this",
" might provide you with some insight."
] |
[
"It's better to imagine that Jupiter was just three times bigger",
"How do you mean? The smallest red dwarf stars have radii just over twice that of Jupiter, yes, but mass is a different story. It takes 16 Jupiter masses (one Jupiter mass being around 317.83 times the mass of the Earth) to make a brown dwarf, and they have a mass range between about 16 and 75-80 Jupiter masses. It's only above that mass range that an astronomical object can sustain hydrogen-1 fusion and become a true star."
] |
[
"Most are not equal sizes. It's better to imagine that Jupiter was just three times bigger.. then it'd also be a star albeit very dim and small. That's really how most binary systems are. One really big star and one smaller star. In our case the smaller one was just too small to light!"
] |
[
"If the Universe is indeed infinite, does it follow that a moving body is stationary relative to the universe?"
] |
[
false
] | null |
[
"A body moving at a uniform velocity can just as well be said to be stationary; that's it. There's no absolute universal rest frame against which to measure velocities, and the Universe being infinite wouldn't change that. In fact, since the Universe only has a finite age we ",
" know if it's infinite, so no experiment you could perform would have a result which depended on whether or not it was infinite."
] |
[
"You're talking about time dilation, right? And the first egg timer (A) is moving v, the second (B) is moving v+w (w parallel to v), the third (C) is moving v-w. Just saying this to make sure I understand your illustration.",
"Also I'm going to assume that they are lightbulbs instead of egg timers, and will go off after the same set amount of perceived time.",
"1) Reference Frame of Egg Timer A",
"Egg Timer A goes off first; then it sees Egg Timer B and C go off simultaneously. (This is because it takes the same amount of time for light from both to hit Egg Timer A)",
"2) Reference Frame of Egg Timer B",
"Egg Timer B goes off first; Egg Timer A goes off second, Egg Timer C goes off last.",
"3) Reference Frame of Egg Timer C",
"Egg Timer C goes off first; Egg Timer A goes off second, Egg Timer B goes off last.",
"This is an illustration that events that are simultaneous in one frame of reference are non-simultaneous in other frames of references."
] |
[
"I think I see what you are trying to say, but \"the Universe\" is not a frame of reference.",
"Frames of reference are relative, and so there must be \"something\" within that frame of reference.",
"The consequence of the idea you are getting at was the idea of an aether that underlies the Universe. There were tests for that. ",
"http://en.wikipedia.org/wiki/Luminiferous_aether#Relative_motion_between_the_Earth_and_aether"
] |
[
"How come otorhinolaryngology is a single discipline if it concerns three different body parts? Are these connected in some way? Are there other examples of specialties that include multiple minor subspecialties?"
] |
[
false
] | null |
[
"They are connected, literally, through the Eustachian tube (part of the middle ear)\nBecause of this connection, illnesses or infections to one of these body parts often affect the other.",
"Also explains why swallowing/chewing can ease the painful feeling in your ear when taking off in an airplane."
] |
[
"Exactly, just to clearify, They share the same epithelial layer (the pink part of the inside of your cheek/lips). Its continues from mouth, middle ear, nose and down your throat because they have the same origins during development, hence infections usually spread, a sore throat can affect your hearing due to tube mentioned in the original comment closing creating a lower pressure in the middle ear. ",
"Other than that, these doctors usually perform most surgeries affecting these areas of the body. The anatomy is so complex and interconnected it requires its own surgeons that also do clinical work.",
"Edit: Source, im a medical student! ",
"Edit 2: Spelling, writing on my phone with Swedish autocorrect apparently takes the air out of my knowledge on what an ENT does. :)"
] |
[
"I was an otorhinolaryngologist for nearly 30 years. In the 60's, ENTs were also trained in eye surgery so lots of older patients recall the EENT specialist. That grouping eventually involved too much knowledge to manage. . The 8\" cube that holds so much of our sensory function is really fascinating because I got to deal with foreign objects in all 3 areas, cancers, congenital deformities, infection, reconstructing trauma, allergies, plastic reconstruction and renovation. Incidentally, most 3rd graders in Spanish speaking countries learned the word early on because it is the longest one in the Spanish language: otorhinolaryngologia "
] |
[
"A question about 'tachyons'"
] |
[
false
] |
Just a quick question about tachyons. I put the word in quotations because it really refers to any hypothetical particles travelling at speeds greater than the speed of light. My question is this: If these particles do indeed exist, when they are created, they start travelling at speeds in excess of c. Does this mean that after their inception, they start travelling our current time flow? Would that make observation of them impossible, because they are moving against our forward flowing time?
|
[
"Tachyons are the result of plugging negative and imaginary numbers into the ",
" equations of special relativity where only positive real numbers are meaningful. But bear in mind that the algebraic equations in question are not meaningful in and of themselves. They're simplifications of more fundamental geometric equations, which permit no such shenanigans.",
"Basically, tachyons aren't even hypothetical. They're just fiction."
] |
[
"Um. No. None of that is true. Antineutrinos are just antineutrinos; they're not special. Radio is ",
" And gravitational waves aren't ",
" at all, but propagating changes in geometry."
] |
[
"Um. No. None of that is true. Antineutrinos are just antineutrinos; they're not special. Radio is ",
" And gravitational waves aren't ",
" at all, but propagating changes in geometry."
] |
[
"Do we have the technology to create an invisibility cloak?"
] |
[
false
] |
An article on yahoo news . What does this mean? Is this possible? Do have the technology to create an invisibility cloak?
|
[
"Do have the technology to create an invisibility cloak?",
"Yes for certain wavelengths of light, primarily microwaves.",
"There have been various devices that purport to work as an invisibility cloak (a quick search shows many), but they all tend to work in one specific direction only.",
"In principle there is no reason according to the laws of physics why this could not occur, but it would require some highly advanced technology."
] |
[
"An article on yahoo news says that you can time cloak. ",
"What does this mean?",
"Yeah, that's the problem: the author of the article doesn't have the slighest idea what it means. So, he writes more or less science-fiction, and references Harry Potter.",
"This paper seems more accurate.",
" You'll notice that while it's a pretty nice experiment, it's utterly useless as-is.",
"Also, ",
"here's the abstract.",
" We're talking about transmitting a message securely, here, not about a Demiguise-grade invisibility cloak."
] |
[
"An issue I see is, that the cloak would have to display different things from different perspectives. ",
"That means, the same point on the cloak would have to adopt several images simultaneously, depending on the onlookers' angle. "
] |
[
"Why do humans have only 2 nipples, unlike other mammals?"
] |
[
false
] |
I really want to know. This question has been bugging me for a long time.
|
[
"It's related to the number of children they have at once - primates usually have one or two children per pregnancy, while other mammals have more, thus needing a higher number of nipples"
] |
[
"Any reason why cows have 4, sometimes 6, nipples and horses only have 2? Both species tend to only give birth to one calf/foal."
] |
[
"Supernumerary nipples",
" are more common than you think..."
] |
[
"What is a freckle?"
] |
[
false
] | null |
[
"Oh ya almost forgot to mention, reheads have a large number of freckles and this is because of their genes. Redheads have a recessive gene variant called MC1R which gives them their hair colour and pale skin, skin with low melanin amounts. This means that more often than not, freckles are seen on redheads due to the ease at which their skin would change due to radiation."
] |
[
"A freckle is a region where melanin is increased, usually over a long period of time, to create darker splotches.",
"BTW those with darker skin colour have more melanin production making their skin darker and simultaneously making it harder for freckles to form."
] |
[
"could you have \"anti freckles\" where you have less melanin?"
] |
[
"Why exactly does Anti-bonding occur in Molecular Orbital diagrams? [Chemistry]"
] |
[
false
] |
Only in the perspective of General Chemistry.
|
[
"If you mix two orbitals together, you can get a symmetric combination and an antisymmetric one."
] |
[
"No, that does not make sense. Both explanations you've given here are incorrect. It has nothing to do either with conservation of energy, nor conservation of angular momentum. It's due to the symmetry (parity and reflection) of the bond, and ultimately of the symmetry properties of the electronic Hamiltonian. ",
"If you have a particle in a 1-dimensional box (or two nuclei, or any other axially-symmetric potential), then half of the solutions to its Schrödinger equation will have even parity and half of them will have odd parity, and the ground state will have even parity. Because a state without a node will have lower energy than one that does, all else being equal. This is a symmetry property, and has nothing to do with conservation of energy, much less conservation of angular momentum, which a 1-dimensional system doesn't even have in any meaningful sense.",
"\"This orbital is equal in magnitude away from the baseline (starting) energy as the bonding orbital.\" - no, it usually is not. You only draw them that way to make a neatly symmetrical graph when you don't know the actual energies. ",
"Coniform already gave the correct answer to this. "
] |
[
"No, that does not make sense. Both explanations you've given here are incorrect. It has nothing to do either with conservation of energy, nor conservation of angular momentum. It's due to the symmetry (parity and reflection) of the bond, and ultimately of the symmetry properties of the electronic Hamiltonian. ",
"If you have a particle in a 1-dimensional box (or two nuclei, or any other axially-symmetric potential), then half of the solutions to its Schrödinger equation will have even parity and half of them will have odd parity, and the ground state will have even parity. Because a state without a node will have lower energy than one that does, all else being equal. This is a symmetry property, and has nothing to do with conservation of energy, much less conservation of angular momentum, which a 1-dimensional system doesn't even have in any meaningful sense.",
"\"This orbital is equal in magnitude away from the baseline (starting) energy as the bonding orbital.\" - no, it usually is not. You only draw them that way to make a neatly symmetrical graph when you don't know the actual energies. ",
"Coniform already gave the correct answer to this. "
] |
[
"Could there possibly be black holes that formed from collapsing dark matter?"
] |
[
false
] |
If the universe is infused with dark matter, would it not have become "clumpy" due to gravity, just like normal matter did (forming superclusters, galaxies, stars, etc)? And therefore, would there not be black holes that formed as clumps of dark matter collapsed, with very little matter nearby?
|
[
"Quite possible, and since no information can escape from a black hole we may never know what the original material was that formed it. However, black holes form from extremely high densities of matter that strongly interacts and that are further crushed and yet it's believed that dark matter, if it exists, is widespread but very diffuse.",
"You might enjoy this article on the subject",
"https://medium.com/starts-with-a-bang/ask-ethan-100-why-doesn-t-dark-matter-form-black-holes-c5b6d90b1883"
] |
[
"Dark matter ",
" get clumpy like normal matter. This is because gravity isn't all you need for clumpiness: some degree of electromagnetic interaction (which normal matter does, but dark matter doesn't) is also necessary.",
"Therefore, it's unlikely to form entire stars, galaxies, or black holes of its own."
] |
[
"Dark matter doesn't clump as easily as it lacks the self interaction to lose kinetic energy. The structures of forms are diffuse halos around galaxies. However dark matter can fall into black holes and contributes to their mass, though it doesn't make difference if a black hole is made of dark matter or normal matter, it's the same."
] |
[
"What causes cell reception to fluctuate when you're right on the cusp of not having any? Or at any time for that matter?"
] |
[
false
] |
When you have very little reception on your phone and it fluctuates, what causes this? Assuming you and the cell tower are not moving relative to each other.
|
[
"Your cell phone uses a radio to talk to the tower. People moving, other radio sources, atmospheric conditions... all of that can contribute to interference between your cellphone and the tower."
] |
[
"woah, off topic but, maritime archaeology? I'm a terrestrial archaeologist and I've heard that a person can get into that field with arch. experience and SCUBA certification? Any merit to this rumor?",
"And thanks for the other answer too"
] |
[
"There's a specialized skillset involved, and shipwrecks have a whole different site formation process. You'd also want to know about ship construction.",
"So theoretically yes, but in practice it'd be tough. Sort of like I suppose I could get into prehistoric lithics if I really wanted, but in practice I've got a whole lot to learn about them (seriously, I know jack and squat about lithics)."
] |
[
"Why is it that you cannot tickle yourself?"
] |
[
false
] | null |
[
"From what I've been told it's because your brain (specifically your cerebellum) can anticipate your own touch and disregards it. ",
"I liked this explanation, from ",
"http://www.scientificamerican.com/article.cfm?id=why-cant-a-person-tickle",
" :",
"\"The answer lies at the back of the brain in an area called the cerebellum, which is involved in monitoring movements. Our studies at University College London have shown that the cerebellum can predict sensations when your own movement causes them but not when someone else does. When you try to tickle yourself, the cerebellum predicts the sensation and this prediction is used to cancel the response of other brain areas to the tickle. Two brain regions are involved in processing how tickling feels. The somatosensory cortex processes touch and the anterior cingulate cortex processes pleasant information. We found that both these regions are less active during self-tickling than they are during tickling performed by someone else, which helps to explains why it doesn’t feel tickly and pleasant when you tickle yourself. Further studies using robots showed that the presence of a small delay between your own movement and the resulting tickle can make the sensation feel tickly. Indeed, the longer the delay, the more tickly it feels. So it might be possible to tickle yourself, if you are willing to invest in a couple of robots!\""
] |
[
"One theory that exists is that, some forms of tickling might have come from the brain naturally making you more aware of more vulnerable areas on the body. \nThink about it, generally the most ticklish points are usually the more vulnerable ones, your sides, under the arms, behind the leg, the neck. Your brain can predict you trying to tickle yourself and disregards it because it does not need to defend itself. However, even if you know you are about to be tickled by someone else, your brain still triggers the ticklish feeling to make you naturally guard yourself. This argument is well supported by the fact that some people who simply have knowledge that they are about to be tickled will begin feeling like they are being tickled before ever being touched.",
"In responding to the cases where you can tickle yourself by lightly running your tongue across the roof of your mouth or similar actions. This is a different type of tickle caused my a light stimulation of nerves. Usually this is explained as you feeling some small stimulation so your nerves become hyper-aware to better identify the stimuli and become over stimulated."
] |
[
"Schizophrenics can"
] |
[
"I'm over 40 and day dream about a career change into a science field. I sometimes think it would be wonderful to explore national parks cataloging tree species, or digging up bones somewhere, maybe even studying psychology. Am I crazy?"
] |
[
false
] |
[deleted]
|
[
"Sounds like you'd be interested in field biology. If you're currently in college there should be more than enough opportunities to get involved in some field biology research assistant positions. Avian field biology for example is an awesome field that's almost entirely outdoors and is always looking for unpaid volunteers or paid research assistants. ",
"Check this out: ",
"Ornjobs",
".",
"Some folks have enrolled in med school in their 40s, so don't let anyone detract you from your vision -- just know what you're getting into. "
] |
[
"Currently on my second masters degree, this one in computer science, at age 41. Don't stop. NEVER STOP."
] |
[
"Currently on my second masters degree, this one in computer science, at age 41. Don't stop. NEVER STOP."
] |
[
"If all motion stops at Absolute Zero, do electrons still orbit the nucleus of an atom?"
] |
[
false
] |
I asked this question to my Chem prof. today, and he said that he would talk to me after class. Alas, he never did. Thanks for the help :)
|
[
"Yes they do still \"orbit\". In fact, all \"motion\" does not stop at absolute zero. All atoms will be in their lowest energy states (no excited electrons states).",
"I put \"orbit\" and \"motion\" in quotations because the so-called \"orbits\" of electrons are better described as different probability distributions for the position of the electron. That's what ",
"this plot",
" shows. At absolute zero, all of the lowest level energy states will be filled (also called the ground state) and no atoms will be in the first or any subsequent excited state. "
] |
[
"Theoretical physicist here. I aprove of this answer with the proviso:",
"At absolute zero, all of the lowest level energy states will be ",
"."
] |
[
"Yes, it's called electron capture. A proton becomes a neutron (atomic number drops by 1) and emits a neutrino."
] |
[
"Does age of parents have any effect on which hereditary characteristics are dominant in children?"
] |
[
false
] | null |
[
"There is some literature on how the age of fathers affects the number of mutations being passed on. As fathers age, their sperm are still being produced meaning they accumulate more mutations with every cell division whereas all the eggs in the mother are produced earlier in development (and in much smaller numbers). So, a father in his 40's will pass more mutations on than one in his 20's.",
"Here",
" is one of the original papers.",
"Here",
" is a news article about the study."
] |
[
"if both parents have brown eyes and the ability to have blue eyed children then there is a 1 in 4 chance of having blue eyed kids. If however, both parents have blue eyes (no brown eye genes) then there is a 0% chance of brown eyes",
"This is not true. ",
"From Wikipedia:",
"\"The earlier belief that blue eye color is a simple recessive trait has been shown to be incorrect. The genetics of eye color are so complex that almost any parent-child combination of eye colors can occur.\"",
"You can read more about it ",
"here",
"."
] |
[
"if both parents have brown eyes and the ability to have blue eyed children then there is a 1 in 4 chance of having blue eyed kids. If however, both parents have blue eyes (no brown eye genes) then there is a 0% chance of brown eyes",
"This is not true. ",
"From Wikipedia:",
"\"The earlier belief that blue eye color is a simple recessive trait has been shown to be incorrect. The genetics of eye color are so complex that almost any parent-child combination of eye colors can occur.\"",
"You can read more about it ",
"here",
"."
] |
[
"Is it possible to have a knife so sharp that it is one atom thick at its edge?"
] |
[
false
] |
As I understand it, the thinner a knife blade is, the sharper it gets. Well could you have a knife that is so sharp that at its edge it is one atom thick? This leads to my secondary question, suppose I had a sheet of metal that was one atom thick. Could I just drop that onto my arm and have it slice it off effortlessly? Could I wave around that sheet of metal and be the most badass dude ever cause I would be hacking people up and they wouldn't even be able to see my blade? I can already tell the answer to these questions is no, I just want to know why it's no. Thanks for the knowledge!
|
[
"Obsidian can be broken to have an edge 1 atom thick. Having a knife with a one atom thick edge would dull the second you touched it to something. See ",
"here",
" for some information about sharpening blades.",
"If your sheet of metal was one atom thick it would most likely tear apart in your hands. Gold foil for decorations is thicker than one atom but is very delicate. While I am sure you could cut someone with it, it would be awfully hard to not destroy it into the process. "
] |
[
"Graphene."
] |
[
"Graphene."
] |
[
"A vaccine for the 2009 H1N1 virus was developed in 3 months (from when it was declared a pandemic). What is different about COVID-19 that makes the required time to develop a vaccine 12-14 months?"
] |
[
false
] | null |
[
"H1N1 is a flu-variant and flu vaccines are developed every year. So researchers could base their work on existing flu vaccines. On the other hand, there is no such tested & safe vaccine on which to base the covid19 vaccine. There was some work done on a vaccine for SARS, which could be used as a starting point, but this work never led to a completed product because SARS was effectively contained and funding dried up because the need for a SARS vaccine went away."
] |
[
"We already have a vaccine for Influenza, we \"Just\" update it every year.",
"Now we have to do One basically from scratch.",
"This can still be done in about 3 months, but we need almost a year to test safety in humans.",
"A vaccine has to be given to more than 90% of the population to generate herd immunity, so if if we don't catch a problem with the vaccine it would be a disaster bigger than the covid pandemic.",
"We cannnot skip safety tests in humans."
] |
[
"The H1N1 you're referring to is an influenzavirus, and very closely related to known H1N1s. They're all descended from the Spanish Flu pandemic virus. We didn't have winter flu outbreaks before that! This means the infrastructure to update influenza virus vaccinations was already in place.",
"SARS-CoV-2 (COVID-19 is the disease it causes) has to be done more or less from scratch. It's a betacoronoavirus, so, for example, methods to interrupt the viral genome entering the capsid are not the same as with influenza. Humans don't have many circulating coronaviruses, and no commercial vaccines against them.",
"Just for kicks, H5N1 influenzavirus is just a few point mutations away from becoming a SARS pandemic. Dutch researchers actually created a version which would do this."
] |
[
"How is CERN able to produce the highest man made temperature without completely destroying their collider?"
] |
[
false
] |
CERN just created the highest man made temperature of about 5.5 trillion Kelvin. How can they create such high temperatures without completely destroying their equipment?
|
[
"It is a very tiny high-temperature system contained in a vacuum. Two lead nuclei collide and for a brief instant, a very high temperature medium is created. This medium expands and cools, \"freezing\" back out into a spray of particles within the vacuum.",
"So this high-temperature medium created in the collisions is never directly observed. It is too small and short lived. To know that such a high-temperature medium was created, one must look at how many particles are emitted in each collision on average, and the patterns in their momentum and direction. From this information, the temperature of the system can be estimated.",
"Over time, the particles coming from the collision will damage the detector electronics. Maintenance and replacements occur every few years when the LHC shuts down for a long period, such as the current shutdown that will end next year."
] |
[
"Basically, temperature is not the only thing that matters. If you slam a few protons together to make a soup of, e.g. 100, particles that together have a temperature of 5.5 trillion K, you still only have 100 particles. Those 100 particles can slam into the walls and spread their energy out into the 10",
" atoms of your detectors and not raise the temperature by any measurable amount."
] |
[
"This extremely high temperature is only for a few hundred thousand particles. The total amount of energy contained in the beam is in the TeV, which is in the 1e-7J range. That is, a tenth of a microJoule. It takes 4181 Joules to heat a kg of water 1 degree C. Of course if this beam hit you it would turn a bunch of atoms in the way into plasma and give you a nasty internal burn, which would be very bad."
] |
[
"Clarification about the Pauli exclusion principle"
] |
[
false
] |
This is something that has been bugging me for a while. The Pauli exclusion principle claims "no two fermions can be in exactly the same quantum state." Most qm books I have encountered describe this equivalently as "no two fermions can have exactly the same set of quantum numbers" and then proceed to list a finite set of them that describe the complete state: J, L, S, ml, ms, N, etc (I might be forgetting some). But an electron in the ground state of hydrogen will always have L = 0, S = 1/2, J = 1/2, ml = 0, ms = 1/2, N = 1 by definition. So if a state can be completely characterized by this set of quantum numbers, and an electron in the ground state of hydrogen will only take these values, this seems to imply that there can only be ONE electron in the ground state of hydrogen in the entire universe. Clearly, this is not true, but I'm having a hard time seeing how it is not implied by the Pauli exclusion principle. Can someone clarify the Pauli exclusion principle for me to help me resolve my misunderstanding? Thanks!
|
[
"To answer your immediate question, an electron in the ground state of hydrogen can have ms = +1/2 or -1/2. ",
"Slightly more interesting, perhaps, is that the PEP you know is a bit simplified. The actual statement of the PEP says that when you put two identical fermions together, their combined wavefunction must be antisymmetric with respect to exchanging the two particles. You can get the simplified version from the complete statement by seeing that if both fermions have the same quantum numbers, exchanging them won't change the sign of the wavefunction, so this configuration is symmetric and not allowed."
] |
[
"Those quantum numbers are a complete description of an electron's state ",
". Electrons bound to a different atom aren't in the same state; the wavefunction looks identical around each atom, but since the atoms are in different places this isn't the same wavefunction."
] |
[
"Wow, thank you for pointing out that tremendous oversight on my part, that the projection can be +/- 1/2 in this situation. ",
"Interesting, I knew about the antisymmetrization condition, but for some reason thought of it as a corollary to the PEP instead of the other way around. I have heard this comes from the spin-statistics theorem, but my professor last term did not elaborate. Is there an accessible explanation or at least some intuition that can be developed with an undergrad physics background?"
] |
[
"If the top layer of skin is just dead cells, what's the point in moisturising?"
] |
[
false
] | null |
[
"If the wood of a table is dead, what's the point in varnishing it? Whilst there is always new skin underneath, maintaining a barrier of dead skin can be better protection from pathogens (there's less that many pathogens can do with a dead cell). Making the surface more pliable also prevents cracking which can provide space for external material to get in and harbour bacteria. ",
"http://en.wikipedia.org/wiki/Moisturizer"
] |
[
"The key word being 'Stay'.\nShort answer: No. The upper layer of the dermis (epidermis) contains three layers within itself. The lowest of these three (S.Basale) is where the skin cells are pushed up, and eventually die.\nIn order for a cream to have any continual effect on how young the skin looks, it would have to penetrate all the way down to the dermis, and possibly the hypodermis, as it is the structure of these layers which contribute to the appearance of the skin. In order to penetrate that far, with the use of some kind of acid, you would do far more damage than good. (This is also why 'Acid peels' are a really good way of spending lots of money in hurting yourself and achieving nothing - it only peels away the very upper layer of the epidermis)",
"Any cream that says it contains collagen or any other protein to do with 'revitalizing' the skin - dont buy. \nCollagen is too large of a molecule to pass through the dead layers of your skin, and is a waste of money.",
"However moisturizing does help to keep your skin healthy, and some will give you a temporary improved appearance of skin, but it wont last.",
"Source: Pharmacology student who just had to do a massive ass paper on the skin."
] |
[
"To add an additional question to OP's interesting query, is there any proof that moisturizing actually makes skin stay \"young looking\" longer?"
] |
[
"Do neuroscientists know how/why certain neurons serve specific functions? For example, what differentiates the neurons in the insula that help to allow a person to perceive something as tasting sweet from other neurons and enables these neurons to serve this function?"
] |
[
false
] | null |
[
"When the nervous system develops, just like in most parts of the body, there are signalling molecules that activate/deactivate certain genes based on where a stem cell is located. That is the general idea of stem line differentiation. The specialization of neurons is driven by the same general mechanism. Neurons have the added complexity that some of them are very long and need to reach from point A to point B to connect different parts of the nervous system. This is done in a similar way by providing 'paths' along which the cell extends with signalling molecules that are sensed by receptor proteins in the cell membrane."
] |
[
"Depending on what kind of answer you expect, the answer can be either yes or no.",
"For example, with neurons of the insula that participate in a person's tasting of sweet tastes, the answer would be yes in the sense that ultimately information that originates in the sweet-activated taste receptors of the tongue has to be shuttled to the insular neurons. So they participate because they are in that pathway. ",
"But the answer would be no if you want to know how the act of these neurons firing should cause a person to ",
" sweetness. We really have no idea of that for any sensory brain area."
] |
[
"Thanks! :)"
] |
[
"Is beach sand filthy?"
] |
[
false
] |
Think about it. We constantly make contact with beach sand without a second thought. The thing is, that same sand has been there for years. Tourists have stepped on it, sweated on it, bled on it, vomited on it, thrown cigarettes in it, etc etc. And it is never renewed. Is there some kind of natural self-cleaning process in sand that I don't know of, or is sand really as filthy as I suspect? for clarity: let's say we're talking about a small bay (so dilution of sand doesn't matter), and obviously the sand that water doesn't touch.
|
[
"I think you owe us another .018..."
] |
[
"A ten shall now be referred to as a kilopenny"
] |
[
"Sand is exposed to constant UV, wind and harsh weather condition , wich is not very suitable for developping organism. And, but this is more of a guess than anything, I think that most beach have a natural ecosystem (bacteria, sandworm, ....), wich clean and mix every layer of the beach.",
"Anyway that was my .002"
] |
[
"Are a projectiles impact forces amplified in space because sound cannot exist?"
] |
[
false
] | null |
[
"\"Sound\" is just us detecting a pressure wave moving through the air. You rightly point out that it can't travel in a vacuum, but it can still be created. EDIT: The wave itself is not created, but the mechanism to do so is doing the exact same thing. ",
"Take a guitar string and strum it - the vibration causes the air around it to move, but if there is no air, the string would still vibrate like that (a bit more because there is no air resistance, of course).",
"Now take a hammer hitting a metal wall - the hammer would move faster, because of the lack of air resistance, but let's ignore that. ",
"The hammer hits the wall, and the wall shakes because of it. Without any air resistance, the wall moves more, but the original impact has the same force. ",
"tl;dr: The two objects would feel the post-impact vibrations for longer, but the original impact would be the same if the two relative speeds were the same. "
] |
[
"I think what you're asking about is conservation of energy. In other words some energy from a collision is lost to sound in the atmosphere, but that can't happen in a vacuum. So, where does that energy go? It seems reasonable to me that it would wind up in the kinetic energy of the masses involved. I don't have any experimental data, though, and it sounds like a fun experiment...."
] |
[
"Then I take it the \"what would be sound energy\" entirely becomes heat energy and the heat gradually dissipates in forms from of atomic radiation.",
"Now a hypothetical. Using a 1 meter thick 100 by 100 meter sheet of Iron(Fe) in one experiment, and a 1 meter cube of Iron in another experiment. Assuming they were both hit by the same force, the cube should reach a greater temperature so therefor the material should distort more (providing enough heat is generated to distort the material eg 1538°C = melting point of Iron)?",
"Distortion determined by Fourier's Law - ",
"http://en.wikipedia.org/wiki/Thermal_conduction#Fourier.27s_law",
" :) - aaaaw yeah. I get how it should work, but Wikipedia explanation is too convoluted for me - needs dumbing down."
] |
[
"Have our lungs any way of cleaning themselves?"
] |
[
false
] |
So, we are constantly inhaling things that are not air into our lungs, specially small solid particles. I assume most of them go out by just breathing out, but its not hard for some particles to get stucked in the web of ducts we have there. Is there something curious about that or im just asking a dumb question?
|
[
"Yes! You have lots of small \"hairy\" cells that line the tubes that go from your windpipe (aka trachea) into the furthest most reaches of your lungs. Nearby these hairy cells are cells that look like goblets. These secrete mucus. When junk gets inhaled, it can get stuck in the mucus. That mucus drips onto those hairy cells. The hair (aka cilia) beat upwards, moving the mucus upwards, out of the tubes and out of the trachea and over into your esophagus. ",
"But sometimes, the junk you inhale is too small, or makes it past the mucus. That stuff reaches the end of the lung tubes, into a structure that looks like a bunch of grapes but is hollow and fills with air (aka alveoli). Those alveoli are surrounded by the clean up crew of the body, cells called macrophages. Macrophages say, mmm yummm, and then (try to) swallow the junk (aka phagocytosis) and digest it. ",
"When things get stuck in the alveoli, and macrophages cant digest it, they get angry, and they call for help. They may be helped by groups of cells that just stand around fighting off anything (aka innate immunity). Or, they may be helped by those who remember / know the specific shape of junk and fight back (trained immunity and adaptive immunity). ",
"Sometimes they really cant digest it even with help, resulting in a cycle of worsening recruitment of macrophages, other immune cells, and immune messenger molecules (aka inflammation). This is what happened in the vaping lung injury scandal back in 2020. People were thickening / diluting their THC oils with vitamin E acetate, making it very oily. This made it hard, and sometimes impossible, for those macrophages to swallow and digest. Because it was so difficult, the subsequent unresolving inflammation caused rip roaring injury to peoples lungs."
] |
[
"Yes there is: ",
"https://en.m.wikipedia.org/wiki/Respiratory_epithelium",
"Particles get stuck in lung mucus which is then transported upwards via small hair in a wave like motion and then swallowed. ",
"Also coughing is a way to get rid of bigger particles."
] |
[
"Unless you are smoker, of course. That will destroy the small hairs, which is the reason why smokers cough so often."
] |
[
"Taking cold medication in a single pill or each medication separate."
] |
[
false
] |
Is there a difference if you take a pill of cold medicine that contains stuff like acetaminophen, antihistamine, Pseudoephedrine and cafeine or if you take this same medications in the same dosage but in separate pills/drops/syrope (At the same time)
|
[
"Not really as the only goal of OTA medications is to alleviate the symptoms of a cold(fever reduction actually works against you, there are exceptions though). Thus, you take them in dosages that help your symptoms up to the recommended amount and no more; they do nothing for the underlying virus/bacteria. With that being said, you should never ever take more than 4 grams TOTAL per 24 hour period of anything containing acetaminophen- it can send you into acute liver failure. ",
"A lot of OTA medications have limitations to them which people should follow(directions). just because its OTA, does not mean its 100% safe. Aspirin can send people into acute renal failure if you take too much or have specific underlying conditions. ",
"This does NOT apply to antibiotics--these are dosage and/or time dependent so you have to take them as directed for them to work properly. ",
"source: 3rd year medical student"
] |
[
"got it. tnx"
] |
[
"Apart from the cost, no. There may be slight variances in absorption rate (how quickly the drug affects you) due to different brands but the end result should be the same. "
] |
[
"If the world was actually flat, what would the horizon look like?"
] |
[
false
] |
Or similarly, if the Earth was The size of VY Canis Majoris.
|
[
"More or less the same from ground level. It will start to become apparent you were on a flat plane (or larger sphere) as you got higher."
] |
[
"Kinda. On Earth, the land you see will drop off at a rate of about 0.000126 miles per mile (well, for the first mile anyway). That is small enough to make the Earth ",
" flat by human observation, at least when you consider that mountains and valleys prevent us from seeing infinitely far. The angle of the horizon and clouds would appear remarkably similar, as in both round and flat Earth they would ",
" to converge toward a single line in very similar ways. On a flat Earth, you would see ",
" clouds as they shrink toward the horizon (assuming ideal cloud conditions), but that is already the way clouds appear to behave anyway, more or less.",
"That small distance adds up fairly quickly if you are looking over an ocean however. A normal human at sea level can see about 3 miles or so. On a flat plane, you could see as far as the height of the waves allowed, basically. Very far, in ideal circumstances. So you ",
" tell the Earth is round at flat zones like oceans or big lakes."
] |
[
"the human eye can see for an indefinite distance",
"This is mostly true, because of the way light is focused by the lens on the retina. For an object an \"infinite\" distance away, the light rays it emits will fall upon the eye parallel to each other. ",
"The eye's lens can bend those parallel rays into a see-able image."
] |
[
"How do electrons physically move from an area of low potential to an area of high potential?"
] |
[
false
] |
I understand they move to an area of high potential, I just don't understand they get there. They move pretty fast, and I've never heard of any electron jet-packs or electrons having wings lol.
|
[
"Okay, so you've got an electron hanging out in an low potential quantum. along comes a photon. this photon happens to be the specific wavelength that has a particular amount of energy. specifically, its energy is equal to the difference in energy between the place where the electron currently occupies and the next orbital up. the photon strikes the electron, and the electron absorbs it's energy. having more energy, the electron makes a quantum leap to the next orbital",
"the thing to remember is that electrons don't have discrete locations, but rather occupy a distribution of probabilities. the electron does not have to physically traverse the space between one orbital and the other. it occupies the lower potential orbital in a probability cloud. then absorbs more energy. suddenly, the lower orbital is no longer a probable space to occupy, and the next orbital is now probable. so it now occupies a probability cloud in that orbital. ",
"TL;DR quantum physics is wierd"
] |
[
"The cool things is that during the absorption, the electron is in a superposition of the low and high states. The interference between these two states has a beat frequency effect with frequency exactly equal to the difference in energy (which is why a photon with that frequency will get absorbed)"
] |
[
"that is a great explanation of a very vague concept! it makes a lot more sense to me now. thank you so much!"
] |
[
"Is time a wave?"
] |
[
false
] |
I was thinking about particle/wave duality and it occurred to me that it could be explained if time were a wave rather than a straight line. Actually the idea is that there are two time waves, travelling in opposite directions, visualized by . When both waves are at zero, position is known absolutely. When both waves are at 1, momentum is known absolutely. A particle is not defined by either time wave but rather the dissonance between both waves, like a . A three dimensional view of this idea is that our universe can be represented as the surface of a pulsating sphere. The surface is one time wave. Outside the sphere is another pulsating sphere. This is the other time wave. The passage of time in our universe is the interaction between the two spheres, where the outer sphere represents the future and the inner sphere represents the past. Represented as the sine waves above, at the maximum when momentum is known, position has the potential to be anywhere, but it collapses as the wave meet halfway between crest and trough. Mass in this view could be explained by part of the momentum vector being perpendicular to the surfaces of the spheres. The vector would be imaginary to us since our existence is defined by the 2d surface and it would be perpendicular to it. This defines energy as vectors which are parallel to the surface and move at the speed of the time wave. I'm sorry if this is far out there but it's really hard to explain.
|
[
"If a wave is travelling, its position changes over time. If time is a travelling wave, what does its position change over?"
] |
[
"It's definitely good to ask these sorts of questions -- so kudos for that. ",
"This doesn't seem particularly \"far out\" (esp compared to say string theory), but seems very vague at least at this point, and I still don't see any predictive power (or see how it simplifies anything). E.g., what do you mean by \"time waves moving in opposite directions\". In your as visualized by pic, you don't label either axis just plot sin x and -sin x. You need to tell us what is moving relative to what.",
"The part of particles arising between the interactions of \"time waves\" seems partially reminiscent of QFT (minus time being a wave), but particles being the (quantized) excitations of fields. The wave-particle duality while being very counterintuitive is well framed within quantum mechanics and QFT, which most physicists do not have problems with (the wave-particle duality that is; QFT has problems e.g. hierarchy problem, accounting for gravity, etc)"
] |
[
"That's a creative question, but as you admit there's room to make it more clear so we can figure how to answer it. Let's start here:",
"if time were a wave rather than a straight line",
"What do you mean by \"if time were a straight line\"? The equation for a straight line in the y-x plane is:\n y = m",
"x + b\nYou propose something like\n t = A",
"x) + B",
"x) + C",
"Essentially, you're implying time is a function of some other parameter. You're treating time as something you can measure, as in:",
"What is the position of the particle?",
"What is the momentum of the particle?",
"What is the energy of the particle?",
"What is the time of the particle?",
"Are you saying time is an observable? In quantum mechanics, observable quantities are represented by mathematical operators. However, time is expressly ",
" an observable and cannot be represented this way. Sakurai makes this very clear in his textbook, ",
"Modern Quantum Mechanics",
":",
"The first important point we should keep in mind is that time is just a parameter in quantum mechanics, ",
" an operator. In particular, time is not an observable.",
"So I guess the big question here that would be nice to clear up is that you want to express time as a function of some other variable. Did you have any variables in mind? If you do, we can work through it and see if it succeeds or fails. Also, could you please label the axes on your graph? Plotting a sine wave and its reflection isn't very informative :)"
] |
[
"What is the correlation between electrons and magnetic fields?"
] |
[
false
] | null |
[
"The paths of moving electrons are curved by magnetic fields, and moving electrons generate magnetic fields."
] |
[
"so is it chicken or the egg in that situation?"
] |
[
"No"
] |
[
"[Astrophysics]Whats the limit a photon can be redshifted? What are a wavelengths theoritical maximum amplitude and period?"
] |
[
false
] |
Can it be red shifted out of existence? Can a wavelength have a period greater than the observable universe? I have so many questions lol. Thank you for taking the time to read, and especially if you take the time to formulate an answer!
|
[
"There is no lower limit for the frequency (=upper limit for wavelength). If you get close to \"one oscillation per age of the universe\" it gets questionable to call things radiation, however."
] |
[
"but I know that we have observed, measured and made a telescope for a wavelength the size of Earth",
"What? Where?",
"We can combine the radio waves recorded by telescopes all over Earth to create a larger effective telescope diameter, but the detected wavelengths are still in the meter range.",
"but then the quantum stuff kicks in and photons may get some energy fluctuations comparable to their own energy",
"That makes no sense."
] |
[
"but I know that we have observed, measured and made a telescope for a wavelength the size of Earth",
"What? Where?",
"We can combine the radio waves recorded by telescopes all over Earth to create a larger effective telescope diameter, but the detected wavelengths are still in the meter range.",
"but then the quantum stuff kicks in and photons may get some energy fluctuations comparable to their own energy",
"That makes no sense."
] |
[
"How do sponges work?"
] |
[
false
] | null |
[
"Sponges are extremely porous - meaning there is a ton of empty spots, voids, in within the sponge.",
"When you dunk the sponge in water water gets absorbed into the tiny pores and is held there through various forces including surface tension and van der waals forces.",
"When we squeeze the sponge the voids get smaller and eventually the pressure in each void overwhelms the surface tension and the van der waal forces and the water oozes out. When you let go, the fibers in the sponge try to push it back to the original shape, which sucks either air or more water into the voids."
] |
[
"The sponge prevents pregnancy by keeping sperm from joining with an egg. ",
"It works in two ways: \n1.) The sponge covers the cervix and blocks sperm from entering the uterus. \n2.) The sponge also continuously releases a spermicide that keeps sperm from moving. ",
"See more at: ",
"http://www.plannedparenthood.org/health-info/birth-control/birth-control-sponge-today-sponge#sthash.Ycf0QsTl.dpuf"
] |
[
"Thanks! This has been bothering me for a while"
] |
[
"Can antimatter form covalent bonds with regular matter?"
] |
[
false
] | null |
[
"No. Antinuclei are negatively charged, they won’t bind with electrons."
] |
[
"Could the subatomic particles that make up antimatter be substituted for the subatomic particles that make up regular matter in order to create an hybrid atom or molecule? Like an atom with a nucleus composed of protons and antineutrons surrounded by electrons?"
] |
[
"No. The quarks and antiquarks in nucleons and antinucleons can annihilate each other."
] |
[
"What happens to a small portion of ants that are separated from their colony?"
] |
[
false
] |
[deleted]
|
[
"An ant that gets separated from its colony will search for its sisters. Largely that will involve walking in random directions until she finds, or fails to find a scent trail. If it fails to find a scent trail that will lead it home it will likely die of old age or exhaustion. ",
"Unless it encounters another colony. If that happens it will be viscously dismembered and consumed by the other colony. ",
"Unless it's an Argentine ant. Then it may join the other colony. But they're weird. ",
"In the off chance it does find its own colony, it may still be viciously attacked and dismembered if it's been gone too long. Ants recognize each other through scent, and if it's lost the scent of the colony, it will be treated as an intruder. ",
"If 200 ants get separated from the colony and they don't find a good trail that will lead them all back, they may end up picking up on each other's scent trail instead. In that case they would follow each other in circles until they all die of exhaustion.",
"\n",
"Here's a youtube video",
" of an ant circle of death with a brief explanation from an entomologist. "
] |
[
"This all sounds like a great new Pixar film. The vicious dismemberment would really put it over the top. "
] |
[
"Ants find their way by marking the path they take with chemical pheromone trails. This way, the other ants from the colony can follow the pheromone trails to food & material sources, and back to the colonies again. ",
"As the ants follow the trails, if they find good food they'll reinforce the trail on the way back. Eventually they'll follow stronger tails.",
"Your ant friends will try to find one of these paths. If they do, they will link back to the colony. If they don't, they'll wander until their physical life functions cease.",
"They cannot establish a new colony without a queen. You've only isolated some workers and soldiers.",
"Edit: typos"
] |
[
"How long can I live off beer?"
] |
[
false
] |
And does type of beer matter? I mean, there's definitely enough calories in beer to provide energy, and they do call Guinness a "meal in a glass"
|
[
"There is a whole style of beer created specifically for this purpose. Trappist monks created the doppelbock style of beer to sustain them during their 46 day fast for Lent. It was \"packed with carbohydrates, calories and vitamins, this unfiltered ‘liquid bread’ sustained the monks from Ash Wednesday to Easter.\"",
"http://j.mp/tttMN0",
"So apparently you can make it at least 46 days, but I'm guessing their intake was rather moderate to avoid the adverse effects of higher consumption. Oh, and I'm sure their religious institution frowned on over-imbibing."
] |
[
"There is a ",
"Man-sers segment on this",
".",
"Final word is 6 weeks but they throw in the \"and water\" at the very end which makes me unsure as to your question. Basically it would be the same as starving to death because you aren't getting some essential proteins and other goodies."
] |
[
"Go to Africa. Live on Sorghum beer. Very nutrious relatively low alcohol."
] |
[
"If Energy can't be created nor destroyed, how can the universe still expan?"
] |
[
false
] |
I've been thinking, and it's a common hypothesis that the universe is infinetly large, and expanding, atleast that's what I think I've heard. Then I got to thinking.. One of the very basics of physics, is that energy can't be created or destroyed. Thusly, nothing can only come from nothing. Following me so far? Well, how is the universe still expanding, then? This is just if we assume that that theory is correct, yes.
|
[
"Conservation of energy only holds when space and time are constant. This means that energy is not conserved on ",
"galactic scales (and we dont expect it to be) due to the expansion of the space diminution in our universe",
"edit: correction"
] |
[
"ooch, gotta make a small but important correction there: it's not conserved on ",
"galactic scales - it's definitely conserved on the scale of the Milky Way."
] |
[
"actually, it's thought that there is new dark energy being made; ie since the universe is expanding and dark energy is a constant value throughout space, it seems that the universe is adding dark energy. But we really don't know enough about dark energy to say one way or the other."
] |
[
"Why is the brain folded to such a high degree?"
] |
[
false
] |
I've heard many answers to this question, mostly along the lines of "it increases the surface area of the brain and this increases the amount of neurons" . I'm confused as to why the trade off of brain volume for increased surface area allows for greater neurons than the converse.
|
[
"An excellent question! It is actually quite simple once you understand the anatomy: the cell bodies of the neurons are almost all found in the cortex, or the outermost layer, of the brain. It is also called the grey matter, ",
"because of its appearance",
". You see that layer of dark grey that's at the boundaries? That's where your ~100 billion neuron bodies are.",
"What about the rest? All that white stuff in the middle (appropriately called white matter) are actually all the ",
" in the brain - it's packed full of ",
"myelinated axons",
" (and glial cells) that are the 100 ",
" connections between the gray matter.",
"So the ",
"cortical gyrii",
" is like a simcity that decided to put every single building on the outskirts of the city and filled the rest of the map in the middle with roads and highways. As more neurons are added through development, ",
"the outer layer tries to expand while the axons pull them together, eventually folding the outer layer like an accordion",
"."
] |
[
"Basically, the bodies of the neurons are located in the outer layer (surface) of the brain. There are reasons for this, which are related to how the brain receives nutrients and chemicals and whatnot - it probably helps with efficiency in many ways. ",
"The point is, the bodies - the control centers, for neurons are mainly in this surface layer - so creating more of this surface layer means that there's room for more ",
". The loss in inner volume of the brain will be very small in proportion to the number of extra neurons available and will mostly mean axons (which are very thin indeed) need to be shorter or closer together."
] |
[
"Folding allows for more brain matter (IE neurons) to fit in to a smaller area. If the cerebral cortex was not wrinkled, only the very outside of the (smooth) brain would contain grey matter. Since it's wrinkled, the gray matter can extend inside and around all of the folds, increasing the amount of usable material. ",
"That's why our intestines are folded, and sponges have holes in them. It allows for more surface area to be used for a certain job. In the brain, the outer layer (grey matter) is used for processing. Thus, the more room we have for processing, the more processing we can do. The more folds we have, the more grey matter we can fit in there.",
"Folding makes it so we don't need huge heads to contain all of our processing equipment. A bigger head would mean weight, it would require more blood, more muscle, more bone, a stronger spine, etc. It would complicate our anatomy and necessitate further evolutionary adaptions. By utilizing the folding technique, the overall size of our head did not have to change to the same degree as if we did not use folding."
] |
[
"[Chemistry] How does the viscosity of the proteins affect in a gel electrophoresis?"
] |
[
false
] |
I can't seem to find a good answer.
|
[
"Viscosity is a particle interaction property. The point of a gel is to create a new set of interactions that dominate inside the gel to create a separation by size. That said the gel probably doesn't completely remove all of the viscosity effects and part of the spread of a specific band of protein may be due to its viscosity."
] |
[
"Excellent point. It's a bulk property, so at least under normal circumstances the bulk properties of the buffer overwhelm any influence of the protein itself. If you vastly overload a gel, you can start to see distortions because the protein starts to dominate the solution properties, but under normal circumstances the SDS will be the main factor determining the solution properties. "
] |
[
"This is the correct answer. An individual protein doesn't have viscosity, but an entire sample of protein or proteins does. A standard SDS-PAGE gel has limited resolution, so if your sample isn't diluted enough, you'll see nothing but smearing, like fourth lane from the left in ",
"this",
" picture. "
] |
[
"Fossil locations in a perfect sample of rock"
] |
[
false
] |
Assume you have a 1km deep sample of rock. It contains the entire known fossil record at the appropriate depth. At what depth would you find the first occurance of commonly know fossils? For instance: early humans, mammoths, trilobytes, different dinosaurs, true plants, early aglae, single cell organisms.
|
[
"It would all depend on rates of erosion and deposition on that piece of earth over time. Stratigraphy (the layering of rock) gives relative dates, such as that humans came after dinosaurs, but does not correspond to any absolute time. It could be that sediment was deposited 3 inches per year during the age of fishes, was eroded at 0.5 inches per year during the age of dinosaurs, and is now being eroded at 0.3 inches per year. For absolute scale you need radiometric dating."
] |
[
"I see what you're after, but geological processes doesn't work that way. Sedimentation can be at slow and steady rates (deep sea sedimentation for example) or sudden and quick (for example avalanches). You can get several meters of material deposited in a few seconds, where in another case you'd need a million years for the same amount of material.",
"\nThen there's erosion and uplift and all sorts of movements going on in the crust. Think about what ages of rocks are currently present at the surface (0 meters). You have sedimentary rocks ranging from 3.8 billion years to basically recent. ",
"A better answer for you would be \"well, then we'd find dinosaurs in the same ",
" as humans. But we don't.\"."
] |
[
"Yeah, that all makes sense. It was more a hypothetical than anything. I just want a way to compare the origin of different species. ",
"Just assume you have a perfect collection of strata with most of the fossils ever found present in the layers. I know such a thing doesn't exist because of the various global locations where certain fossils have been found.",
"Basically I want to say \"If everything was present in a 1km deep sample of stratum, you wouldn't find anything remotely human below 10cm but you'd find algae way down at 950m.\"",
"I don't want to get into an technical discussion on the methods of radiometric dating, but have a simple, understandable example of \"we've never found a T-Rex outside of the band between Xm and Ym deep\""
] |
[
"Homo sapiens have been traced \"out of Africa,\" but is there any detailed analysis of our geographic origins and migrations before this?"
] |
[
false
] |
Research tracing the geographic migrations of Y-DNA and mt-DNA have generated some great maps of human migrations like this one from the for human mt-DNA. If we go back and include and we would still be within Africa, but going back further to the common ancestor with and beyond, there should be some wide migrations. Do we know with much detail what kind of migration path these early ancestors took? I guess ideally there would be some sort of series of maps that chronicled movement from the first land vertebrate on Laurasia or Gondwana to the dawn of humanity in southern Africa. Surely Y-DNA/mt-DNA and the fossil record allows us to make at least a generalized map of migration, right?
|
[
"It was my understanding that research like the Genographic Project does not rely on fossilized DNA at all, but a comparative analysis of DNA from extant animals.",
"Fossils provide a different and more direct way to see where an ancient animal ranged that is perhaps less specific, but better to use after Y-DNA/mt-DNA becomes too convoluted."
] |
[
"It was my understanding that research like the Genographic Project does not rely on fossilized DNA at all, but a comparative analysis of DNA from extant animals.",
"That is my understanding as well. ",
"Fossils provide a different and more direct way to see where an ancient animal ranged that is perhaps less specific, but better to use after Y-DNA/mt-DNA becomes too convoluted.",
"I'm not sure what you mean by ranged. If you're referring to comparative anatomy, I'm not so sure that necessarily fits the bill better than molecular analysis for regression."
] |
[
"It is incredibly difficult to get usable DNA from fossils. The older the fossil, the harder, and in many cases more impossible it would be to retrieve something usable. That being said, many of those reconstructions work backwards. We don't analyse fossil DNA but do relative comparisons between large sample sets of DNA, which allows us to determine where and when divergence occurs (with a sometimes wide margin of error). "
] |
[
"How do they reproduce seedless fruits/vegetables ?"
] |
[
false
] |
Seedless watermelon for instance, where do they get the seeds to reproduce ?
|
[
"Seedless fruits and vegetables are genetic freaks that don't reproduce, but they came from a parent plant.",
"As far as I know there are two methods to do this. We shall refer to them as the splicing method and the mule method. But both methods result in a plant that can't reproduce using normal reproductive methods ( plant version sexy time). ",
"The splicing method. We will use bananas for example. Normal bananas are actually riddled with seeds making them a pain to eat. You would start by cross breeding different species of banana until you came up with one banana that tasted good and has a genetic defect that prevents the seeds from maturing. Once you have your one plant you take the root ball at the base of the plant and cut it up into small portions and replant each one at the next growing season. Essentially you are cutting the plant in half and letting each half grow into a full sized plant. After a couple hundred times of doing this you will have a whole banana plantation full of bananas the have no seeds and all taste the same since they are all genetically same plant or a clone if you will. This is very dangerous, because the traditional method of passing on genes is how plants protect themselves from diseases. In the normal way things work, if a fungus we're to start eating up banana plants some of them would be able to develop a resistance to it and pass that resistance on to its offspring. If all the banana plants are clones of the same plant, then they also inherit the same immune system. Back in the 1950s a fungus called fusarium oxysporum wiped out entire species of banana because of this, there was a small panic that spead the world because everyone thought we would have no bananas.",
"The mule method. This is for plants that don't grow back every year and rely on seeds to repopulate. Monsanto is great for this. You start the same as the splicing method with cross breeding. But instead of looking for one plant you're trying to make a set of parent plants that are so different from each other that they can barely reproduce. Kind of like how mules came into existence. A mule is a crossbreed between a horse and a donkey. They are close enough relatives that they can reproduce but the offspring is so genetically different from both parents that they can't reproduce, in the same way you can't mate a cat and a dog to get a catdog. Mules cannot have offspring with a horse or a donkey, and apparently not even another mule. Now instead of beasts of burden, it's a plant that will produce fruit but can't reproduce therefore no seeds"
] |
[
"See ",
"https://en.wikipedia.org/wiki/Plant_propagation#Asexual_propagation",
"For ",
"watermelon",
". They take the pollen from the seedless watermelon and pollinate a conventional watermelon flower. This produces seedless watermelon seeds."
] |
[
"so it's not just about growing seedless watermelons themselves... there is also an industry around producing only the seeds to grow these seedless fruits?"
] |
[
"What makes root beer floats so foamy?"
] |
[
false
] |
Is there some sort of chemical reaction going on between the soda and the ice cream?
|
[
"The fats and proteins from the ice cream assist in creating longer lasting bubbles from the carbonation. "
] |
[
"Pretty sure you're spot on with that, the massive amount of nucleation sites act to effectively knock the carbon dioxide out of solution, causing a huge release of gas bubbles"
] |
[
"Pretty sure you're spot on with that, the massive amount of nucleation sites act to effectively knock the carbon dioxide out of solution, causing a huge release of gas bubbles"
] |
[
"What decides if a gene becomes Dominant or recessive?"
] |
[
false
] | null |
[
"There is no blue pigment. The blue is just a lack of brown and the light reflecting off of the eye.",
"But protein function in general is determined by a bunch of different things. The amino acids coded by the DNA create a backbone for the protein that has to fold properly on itself and then bind to other proteins or substrates. Messing with any of those binding sites can just turn it into a dud. I don't know enough about the eye example to say why the blue is specifically less effective than the brown. Wikapedia says its more complicated than a single gene. I know that my answer was pretty general but I'm happy to point you in the right direction for more specific examples!"
] |
[
"In all of the classical examples it's due to the actual protein that is being made by the gene. Dominant genes are usually the functional protein and recessive have a mutation that makes it less functional. Function can be performed with only 1 copy of the protein, meaning the only loss is with both alleles mutated.\nIn the blue vs brown eye example, brown is dominant because the gene actually codes for pigment wheras the blue allele doesn't make a functional pigment. So only 1 functional pigment gene is necessary to turn your eyes brown. This obviously makes sense in recessive disorders where a loss of both gene copies of an important protein causes disease."
] |
[
"This is the ",
" of dominance on genetic disorders, not the underlying cause. In the terms of the example you gave, the original question is asking what ",
" the disease allele to be dominant or recessive. Assuming the disease is controlled by the isoform of a single, protein-encoding gene, then the determining factor is ",
"Here are two examples, the first in which the disease is recessive (which is more common), and the second in which it is dominant:",
"In the case where just one healthy copy of a protein is required for normal biologic function, the disease phenotype will only appear if ",
" copies of the gene (both alleles) produce non-functional proteins. This typically concerns metabolic disorders, in which the ability to carry out a certain step of a metabolic pathway becomes compromised if both inherited alleles contain a loss-of-function mutation. Alternatively, if just one isoform is non-functional, the other isoform can still carry out the metabolic function. This makes the disease recessive.",
"A disease is dominant if a particular allele codes for a protein which ",
" confers a deleterious effect. An example is Huntington's Disease, in which a mutant form of a particular protein is not just non-functional, but prone to forming massive aggregates that kill cells. The fact that the other isoform is carrying out its function normally is irrelevant, since the aggregates themselves are lethal. To think of this another way, if a deleterious allele is dominant, then injecting its gene product into a cell that lacks that allele would theoretically cause the deleterious effect in that cell.",
"There is, as you might imagine, a third possibility, known as ",
". This results when two functional alleles are in fact required for normal function. Whether this is the case for a given gene is pretty much random and depends on the structure and function of the gene product, as well as its expression regulation. In this case, the disease results from a loss-of-function allele like in a recessive disorder, but it is not completely dominant or recessive and is referred to as ",
", so one copy of the null (non-functional) allele produces a relatively mild phenotype, and two copies of the null allele produce a relatively severe phenotype. Such diseases are often fatal in the homozygous form."
] |
[
"How come humans can't stand still as well as other animals?"
] |
[
false
] |
When I try to stand still, I still move a little but the other day I saw a squirrel just standing still and barely moving. Are we incapable or what? Sorry for all the alliteration.
|
[
"Most other animals stand still on 4 legs, we stand still on 2. This means it's easier for us to sway since we're tall and have a small base of support."
] |
[
"Squirrels practice standing still regularly. If you practiced standing still daily then you too could do it without much issue eg human statues, guards, hunters/snipers.",
"Being tall and 2 legged shouldn't matter unless there is a wind or something. You find your center of gravity and don't move. You may tire more quickly having 2 less supports and more weight but with practice/exercise that issue should go away. "
] |
[
"This seems to be a poor explanation. ",
"I can put all 4 of my limbs on the ground. I am not better at remaining still after doing so (in fact, I'm worse)."
] |
[
"Do blind people get sleepy in the dark?"
] |
[
false
] |
[deleted]
|
[
"There are a host of reasons why people can have blindness, so there isn't a single answer to this. In short: Not all blind people are the same. ",
"That said, yes, in some people with blindness the photoreceptor cells that signal to the brain to produce \"sleepy time\" chemicals can be intact and functional even though they are blind. Also, there are other zeitgebers, but light is a very important one.",
"http://en.wikipedia.org/wiki/Zeitgeber"
] |
[
"To elaborate: the influence of light on blind people's circadian rhythms is dependent on whether stimuli from the optical nerves reach the ",
"suprachiasmatic nucleus",
", a (very!) small part of the brain that releases melatonin (among other neurotransmitters) - an important neurotransmitter implicated in modifying the circadian rhythm.",
"There are several ways blindness can occur: basically if anything is damaged in the ",
"visual system",
" - from eyeball to visual cortex - this can induce partial or complete blindness. However, ",
" when the pathway between photoreceptors and the suprachiasmatic nucleus is compromised (the SCN is somewhere between the optic nerve and right next to the ",
"thalamus",
" - basically a relay center for sensory information from where it gets sent to other regions of the brain for processing) will a blind person not be influenced in their day/night cycle by light."
] |
[
"Most blind people do have some residual light perception. ",
"This website has the total number of blind individuals with no light perception as 15% of blind people",
". Oddly enough, there's some debate if one should ",
"blindfold blind people",
" for learning. If you ask a blind person with residiual light perception, they tend to keep the lights on when they're awake, even though it provides no real benefit. So, to answer your question, just like sighted people, for 85% of blind people."
] |
[
"Does a supermassive black hole exist before a galaxy aggregates, and serve as an attractor to create the galaxy, or does the supermassive black hole aggregate because of the existing galaxy?"
] |
[
false
] |
[deleted]
|
[
"There is some evidence suggesting that galactic development is both spurred and controlled by the formation of black holes.",
"In the following quote, the 'bulges' being referred to are the bulges present at the center of spiral galaxies.",
"Each bulge contains a central black hole, whose mass is proportional to the bulge stellar mass 1–5, M BH ≈ 0.001M bulge. Black holes and bulges also formed at about the same epoch in the lifetime of the Universe 6,7 . These observations imply that the formation of black holes and the formation of bulges are closely linked. ",
"source",
"It kind of makes sense, really. According to the big-bang theory, the early universe is was very dense and early stars were universally large and short-lived -- the perfect progenitors of super-massive black holes. Those early black holes would coalesce and concentrate the field of matter around them, leading to galaxies.",
"Their presence also serves to limit the growth of galaxies, as they feed on matter they heat up the surrounding gas -- making it both hotter and less dense, and that limits star formation."
] |
[
"They probably wrote a research paper for a class. Non scientific means it wasn't a published paper in a journal, for example."
] |
[
"They probably wrote a research paper for a class. Non scientific means it wasn't a published paper in a journal, for example."
] |
[
"Can a skinny object have gravity?"
] |
[
false
] |
My 8yo asked if an object that is significantly larger in one dimension than another, like an infinite 2x4, would have notable gravity. Thoughts?
|
[
"I ",
" your eight-year-old.",
"The gravitational field of an infinite flat plate of finite thickness is actually a ",
" problem in field theory. A full exploration of Gauss's law is beyond the limits of my motivation at the moment, but suffice to say it's a wonderful little problem. Spoiler alert: the gravitational acceleration field is actually ",
" and does not change as a function of distance.",
"So yes, things which are very large in some dimensions and very small in others do gravitate, and in fascinating ways."
] |
[
"It's constant for a 2D mass distribution (infinite plane), but not for a 1D distribution (infinite line). ",
"Although this begs an interesting question: if we lived in two dimensions, would an infinite line of mass have constant gravitational pull? I'd have to think about that..."
] |
[
"Fair point. I went the wrong way with \"skinny.\"",
"But still! Science! Fun! When someone has already done the maths for you!"
] |
[
"At What Latitude is the Largest \"Sea-Locked\" (All-Ocean) Circle of Latitude?"
] |
[
false
] |
I'm looking for the largest circle you can draw on Earth at constant latitude that would never intersect land.
|
[
"If you look at a ",
"Mercator projection map",
" it is pretty easy to see that it would be close to cap Horn. So it would be close to 56 degree latitude south."
] |
[
"It distorts area, not coordinates. Latitude lines are corrected for the distortion."
] |
[
"It doesn't have to. It preserves correct locations, so you can still follow a horizontal line of latitude."
] |
[
"What theoretically happens in the middle of two merging kerr black holes?"
] |
[
false
] |
Let me first specify what I mean by the question. Kerr black holes have an angular momentum and thus drag the infalling matter in the same direction of their spin right? Now let's assume that two exactly same kerr black holes just with their spin the opposite way are on a collision course with each other (as in they would directly hit each other instead of rotating around each other and eventually merge), what would happen the very instant their opposingly spinning event horizons touched? Could there be theoretically even an almost unmeasurable instant of time where their event horizons cancelled out and say a photon could escape even though it was initially doomed to fall into one the singularities?
|
[
"When two Schwarzschild black holes merge, there is actually a larger \"effective horizon\" that encompasses the two, that is bigger than each of them. With Kerr, it'll be more complicated (you also have the actual black hole region as well as the ergospheres). There are a few papers calculating what collisions would be like, but they don't have cool pictures.",
"In fact, most of these papers seem to assume that the two black holes have their spins aligned, but in this one they consider the anti-aligned case: ",
"http://arxiv.org/pdf/gr-qc/0702052.pdf"
] |
[
"If by internal dynamics you mean the shapes of the horizons then no I don't think so. Actually, I just found this: ",
"http://iopscience.iop.org/article/10.1088/0264-9381/7/12/002/pdf"
] |
[
"This paper doesn't seem to touch on the internal dynamics; do the others you were mentioning? I know that the study of black-hole mergers is so far fairly incomplete."
] |
[
"Anyone with a solid description of universe expansion?"
] |
[
false
] | null |
[
"Forget expansion for now, and think instead of space itself stretching.",
"Take a partially inflated balloon and an ink marker. Place two dots a unit length away from one another. As the balloon is further inflated the distance between the dots increases as the fabric of the balloon between them stretches. Furthermore, the rate that the distance between them increases is a function of the distance. In other words points that are farther apart will move apart faster as there is more material in between that is stretching.",
"The surface of the balloon is like space itself and the dots represent points in space. The dots can be replaced by ants to represent movement through space, but space itself (what the ants walk on) is what is expanding."
] |
[
"thanks for the explanation, its making more sense now. "
] |
[
"Don't worry too much if it doesn't. Humans are designed to comprehend catching antelope on the plains of Africa and such, not the largest - nor smallest -natural behaviour of the Universe. The ability for a human being to \"visualize\" something is not a requirement for it to be true."
] |
[
"Does calorie in foods change depending on how its cooked ?"
] |
[
false
] |
I'm guessing it could change with frying etc. With oil from outside the food but what happens in the inside ? Do both purée potato and potato in a stew have same calories given they are equal in weight. Or does it differ with meats, veggies or eggs etc. depending on what kind of food is it ? Please do enlighten me if its not a dumb question !
|
[
"Not a dumb question. I'll answer it in two parts. First, as you pointed out, if something is added calories will change. Oil, being a fat, is calorie dense and will increase the calories of a food as it soaks in. This is why grilled chicken is much healthier than fried (though the breading doesn't help either). Pretty straight forward.",
"But let's look at just cooking. Take meat or vegetables, as they are great examples. As heat is added, the food under goes chemical changes. The most significant are the breakdown of starches (sugars) and protein chains. Energy is put into the food and work is done chemically. This is important later.",
"Now, for the most part, calories aren't really changing during cooking. What is changing is the net calories the body will absorb. You see, instead of having to do work to break the long sugar or protein chains chemically through the process of digestion, the heat from cooking does it for us, saving a LOT of energy - approximately one third of our bodies energy goes into operating our digestive system, which is why you can go into a \"food coma\" as the body lags to support the digestive demand. ",
"Since cooking saves us calories burned, more of a food's calories can be used or stored as body fat. This is theorized to be a huge driver in our evolution, particularly with our calorie-hungry large brains. Cooking foods allow us to extract more calories from our food.",
"As an extension, these principles explain problems like rampant obesity. Highly processed foods are usually made with short chain - glucose, fructose - sugars, and our bodies can just rapidly absorb them, where as something like fruit has longer chain - sucrose - sugars, as well as fiber, to slow down digestion. Thus a 300 calorie artificial fruit snack (think Fruit by the Foot) is higher in net calories than a 300 calorie apple. Increased sugar consumption has other effects like increasing your insulin response which triggers the processing of blood sugar into fat and can lead to diabetes. Further, more complex digestible elements like fat and protein are even more intensive on digestive resources, which is partly why diets like Atkins or Keto can work."
] |
[
"/u/prometheus2508",
" did a great job here, but I think you might be interested in a couple things that they left out.",
"First is that our bodies have a \"medium-term\" energy storage option between blood sugar and fat, namely glycogen. Glycogen is very similar to starch (the primary carbohydrate source in grains and tubers) and consists of linked glucose (sugar) molecules. We have some glycogen stores in our muscles, while most of it is stored in the liver. Glycogen stores in the muscles exist to rapidly provide your muscles with energy, even under anaerobic (oxygen-free) conditions: While the most efficient method of ATP production is aerobic respiration in the mitochondria, glucose alone can be used to produce ATP without oxygen. Therefore, when you perform anaerobic physical lifting (such as weightlifting or sprinting), you can't use fats, since you need oxygen to get energy out of them - to say nothing of the time it takes to transport fatty acids to muscles in the first place. Therefore, your muscles use glucose from glycogen, initially from their own glycogen stores, and then from your liver, which is constantly either forming or breaking down glycogen in order to maintain an ideal blood-sugar level. In times of fasting or starvation, the liver can provide a few hours worth of energy, after which your body must rely almost entirely on fat reserves.",
"Second is that the brain is not only very energy-demanding, but it is also specifically glucose-demanding. Unlike most of your body, your brain ",
" obtain energy from fats. It derives almost all of its energy from glucose, which is why you may have an easier time performing physical rather than mental activity when you haven't eaten for several hours. The brain is very energy demanding in large part because it has to expend lots of energy to pump ions in and out of its cells to produce electric currents. Ion-pumping is very energy intensive: 3/4 of your basal metabolic energy requirement (process to keep you alive, not including physical activity) is comprised by maintaining the balance of sodium and potassium ions in your cells. The brain therefore needs a lot of ATP, and for this, aerobic respiration is required, so the brain monopolizes your body's oxygen whenever therere's a shortage.",
"You may, then, wonder how it is that humans can survive long after their glycogen stores run out, since the brain can't use fats for energy. The truth is actually that they can't use fats ",
", but they can use a class of chemicals called ",
" for aerobic respiration. Ketone bodies are derived from the molecule Acetyl-CoA, the input for aerobic respiration. Acetyl-CoA can be derived from carbohydrates, amino acids (i.e. from proteins), or fats - that is, from basically any energy source. The brain can't break down fats to make Acetyl-CoA, but it can process ketone bodies back into Acetyl-CoA if another organ (usually the liver) first does the work of producing the ketone bodies, which are exported to the brain.",
"To get back to the original question, however: fats are great for long-term survival because they are very energy-dense, but they take a relatively long time to process into usable energy, especially for the brain since it can't use them directly. Therefore, your body runs at its best when it has easy access to carbohydrates, obtained directly from nutrition or from its own glycogen stores."
] |
[
"Aah, so the brain goes for the most practical energy source first rather than using most common (I think?) being fat stored in body?",
"I think it's best to say that it uses the most quickly metabolized energy source (glucose). The energy in fat reserves is always far in excess of that in glycogen, but actually getting energy out of them is a relatively long process (on the time scales of metabolism). Glucose, on the other hand, is transported in usable form through the blood and can start being broken down for energy as soon as it enters a cell.",
"Then does craving for more sugar after eating something sweet has anything to do with brain wanting consume more sugar based energy or its just cause of sugar being \"addictive\". ",
"Both. Sugar is addictive because it's very useful for our bodies, which evolved under the constant threat of starvation. Pure sugar is also rare in nature (refined sugar was not available to Eurasia, Africa, and Oceania until the Columbian Exchange began), so sugary processed foods fall outside the paradigm of what our bodies are \"supposed\" to deal with. It's essentially pure energy that requires no work to digest, so its in the interest of an organism with limited access to nutrition to consume as much of it as possible when it gets the chance. Obviously, such a tactic is detrimental when food shortage ",
" an issue.",
"I'm not familiar with the actual mechanism of addiction and what criteria something must fulfill to be considered addictive, but to the best of my knowledge, researchers in the relevant fields do consider sugar to be an addictive substance."
] |
[
"What happens if we artificially stimulate the visual cortex of someone who has been blind from birth?"
] |
[
false
] |
Do they see patterns and colors? If someone has a genetic defect that, for instance, means they do not have cones and rods in their eyes and so cannot see, presumably all the other circuitry is intact and can function with the proper stimulation.
|
[
"If they ",
" developed without a retina or optic tract then it's likely they wouldn't experience any visual phenomena. This is because in order for your brain to be able to represent a particular visual phenomenon it first needs to experience that [kind of] sensation and then encode the statistical patterns that are associated with it. Your brain basically starts out knowing nothing about the visual world and through visual experience builds a dictionary of various visual features. The beginnings of this are initiated before birth through so called retinal waves, which induce the initial organization of primary visual cortex into so called feature maps (orientation maps being the most studied), but this process has been shown to require actual visual experience to stabilize. ",
"To answer your question then, it depends on the source of their blindness. If the individual had an intact retina before birth they might have a faint visual experience during direct stimulation of the visual cortex, while those missing the retina entirely would most likely not experience any visual sensation. There is also a chance that given enough time the visual areas of the brain would look for new inputs, from different senses, such that even if they had early visual experience the visual areas of the brain may have been rewired to process other sensory modalities.",
"Source: PhD student working on computational modelling of the development of the early visual system.",
"Edit: Corrections."
] |
[
"Part of the reason I ask this question is because I have come across this statement before - especially from students of philosophy - and I doubt it to be completely correct.",
"It seems pretty certain this is correct because we have done extensive lesioning studies, which have shown that cutting off inputs to the primary visual cortex entirely disrupts the organization of this area. You may be correct in so far that the visual areas of the brain are optimized to capture the statistical structure of natural vision better than say auditory areas but demonstrations of cross-modal recruitment of brain areas seems to indicate that this specialization does not stop the primary visual cortex from say processing sound.",
"To say the brain knows nothing about vision at birth is probably incorrect but if what it knows isn't used it certainly wastes no time discarding it."
] |
[
"Your brain basically starts out knowing nothing about the visual world",
"Part of the reason I ask this question is because I have come across this statement before - especially from students of philosophy - and I doubt it to be completely correct. It is rather like language - it used to be believed that language was completely learnt, but we now know that there is some language related wiring in our brains that means we are born with some things pre-wired (see Chomsky, Universal Grammar etc). I expect that the brain already has some wiring related to processing visual information and generating visual sensations, and that it is ",
" completely learnt - although it may of course wither away to almost nothing if not used."
] |
[
"What is luciferase? How does it appear in general life, and is it connected to anything in the medical realm?"
] |
[
false
] |
Context: someone mentioned Luciferase is in vaccines as tracking agents, and while I don't believe that, I want to know what it actually does both connected to humans. I did some quick google searches and know it's connected to lighting/fireflies, but that's the base of what I know. Disclaimer, I'm not a scientist. I wish to educate myself for my own sake. Also, if flair is improper, please tell me.
|
[
"It’s the enzyme responsible for the fire in fireflies. It can be used experimentally to show that a particular cell has been successfully targeted by some agent or procedure. It’s not used in any production vaccine, only some experimental precursors."
] |
[
"Luciferase is a glowing protein found in fireflies (hence why “lucifer” is in the name—it’s latin for “light of the morning”, “lux” being “light” in Latin). As far as I know from my biology classes, it’s often used as a tag so you know what is being used/produced and where. I’m not an expert by any stretch of the imagination (I’m just a recently graduated neuroscience student with a strong background in biology and pharmacology), but let’s say we take the Covid mRNA vaccine as an example. Let’s view a cell as a huge Word document. Make it a textbook, or something. The point is, you can’t print the whole document at once because it would be impractical and you’d use up too much time and paper. The whole Word document is DNA. Now let’s say you want to print out specific chapters of your textbook. You send a copy of the chapters you want to print to your printer. This copy of the chapter you want to print is mRNA. Then your printer takes the electronic version of the chapters you want to print and translates it into a paper document. That paper document is whatever protein you want to print. In the case of an mRNA COVID vaccine, my understanding is that they’re basically giving normal cells a the instructions needed to print out a “Wanted, enemy #1 poster” (I.e. harmless fragment of COVID-19, like a virus mug-shot) so that our immune system can examine it and go “huh. Our enemy had characteristic spikes. Good, now I know to attack anyone who shows up with those spikes”.",
"As you may guess, we want an actual guarantee that our cells are printing the “wanted” ads for COVID. But there’s one major issue with our cell computer-printer system: it’s really, really, ",
" tiny. And autonomous. Which means we know that there is a Word Document, we kinda know what’s written on it, but we have no idea if our tiny computer is printing out the “Wanted poster” like we want it to. What’s worse is that we’re looking for said “wanted poster” in a cellular haystack. That’s where a protein like luciferase comes in. What Luciferase allows us to do is add a section to the “wanted poster” mRNA that tells cells “hey, that wanted poster? I want it to GLOW in the DARK!” Basically, you’re making your “needle in a cellular haystack” emit light. It’s a lab tool that allows scientists to go “oh, look, these cells glow, that means they’re printing the Wanted poster. Oh, that cell glows a LOT? Well, it’s making a LOT of Wanted posters.” Basically, luciferase allows you to keep track of how many proteins of interest are being produced and where. ",
"Edit: as another user has said, it’s not used in the vaccine per sé, but in the pre-vaccine as a test to confirm that the vaccine will do what you expect it to do.",
"Hope this helps."
] |
[
"What I want to see is a lactobacillus with hACE inserted in its membrane, and luciferase inserted - the gene that glows when the COVID-19/ACE2 complex forms - see Sherlock's antigen test - this way people could go and drink a lactobacillus drink, when asymptomatic, and start progressively growing brighter and brighter after infection with COVID 19. The bacterial ace2 receptors will serve decoy duty, protecting the human cells, giving the body time to mount a decent defense. And build decent long term antibodies in the process. And the lactobacillus will harmlessly continue to replicate in the microbiome, doing double duty - eating virus, protecting us, and glowing so that we know. And hospitals know. And airports know. And schools know. And nursing homes know. Even if completely asymptomatic. ",
"Here's a series of links if interested.\nACE2 effective as a decoy\n",
"https://www.nature.com/articles/s41392-020-00374-6",
"CRISPR and Fluorescence for Fast testing\n",
"https://www.medrxiv.org/content/10.1101/2020.09.28.20201947v1",
"Use of Lactobacillus with hACE2 in its membrane\n",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6661465/",
"Do lactobacillus out there already have an ACE2 like receptor that decoys for hACE2?\n",
"https://www.nature.com/articles/s41467-020-14867-z.pdf?draft=collection",
"And is that why fermented vegetables help with COVID-19 survival?\n",
"https://www.medrxiv.org/content/10.1101/2020.07.06.20147025v1",
"Or is it Nicin that prevents the spike from binding hACE2?\n",
"https://www.sciencedirect.com/science/article/pii/S004268222030204X"
] |
[
"When hunting, do different wolf packs use different tactics when taking down prey like a dear or are they generally the same for all wolves?"
] |
[
false
] |
[deleted]
|
[
"In at least some cases, there have been observations of older female orcas intentionally teaching hunting techinques to juveniles in their pod (that is to say, teaching, as opposed to simply imitation). ",
"Source1",
" ",
"Source2",
". I don't know if there is hierarchical leadership in the hunting, or if it's just generally the old leading the young."
] |
[
"I don't know about wolves, although I did come across ",
"some research",
" indicating that it is possible to simulate the hunting techniques of wolves as an emergent behavior that doesn't require either leadership or communication.",
"While we're waiting for someone who knows more about wolves, ",
"here's an article",
" explaining that what you're asking about does happen with Orcas. Various tactics and behaviors are learned and passed on from generation to generation and whale to whale, resulting in differences between various groups and populations."
] |
[
"Fascinating, but who teaches the tactics? Is there a leader who coordinates the attacks or do all the members of the pod simply know what to do and when?"
] |
[
"Some medications can pass the blood brain barrier, others can't. Why?"
] |
[
false
] |
Fluconazole and intraconazole are two very similar antifungal medications That treat almost the same things. The first readily passes through the blood brain barrier, the second doesn't. Why?
|
[
"Actually, take a look at the molecular structures of the 2 drugs that you listed, you can see that they are quite different. ",
"http://www.doctorfungus.org/thedrugs/images/fig_fluconazole.gif",
"\n",
"http://www.doctorfungus.org/thedrugs/images/fig_itraconazole.gif",
"Right at the start, you can see that itraconazole is ",
" larger than fluconazole. So I'd bet that the molecular weight is already surpassing Lipinski's Rule of 5. Typically, structures above 400-500 daltons can not pass through the BBB. ",
"Remember, just because the therapeutic effect of a drug might be similar, the structure can vary widely to cater to pharmacokinetics."
] |
[
"related question:",
"Is it true that lipid soluble substances pass through the blood brain barrier easier than water-soluble substances?"
] |
[
"Yes, very much so. The barrier consist for the most part of a lipid layer where hydrophillic compounds will have a hard time passing over.",
"Ninja edit: unless there's a transporter specific for the hydrophilic compound of course."
] |
[
"Ion Plated Titanium?"
] |
[
false
] |
Alright, so I've heard ion plating titanium results in a hardened surface. I've seen this mainly use in jewelry and watches. How does ion plating increase the hardness of the surface? Is there a difference with black ion plating and blue/another color ion plating? I ask this because my friend is considering buying a Citizen Perpetual Chrono A-T and can't decide on black or blue ion plating. I personally can't see a single difference in the models except $100 on the price tag. Also, where else is ion plated titanium used? or is it merely cosmetic appeal like in jewelry?
|
[
"In general, ion plating increases the hardness of the surface because the layer that is plated on is some compound with additional resistance to deformation/abrasion/wear. In the case of Titanium Ion Plating, it's probably TiN that is being deposited on the surface. TiN is a very hard and chemically stable compound, and there is evidence to suggest that the TiN produced from Ion Plating is mechanically more robust than TiN produced using other plating methods. From what I've read though, TiN often produces a gold-coloured coating but I would guess that it wouldn't be hard to then coat that to produce a black or blue colour. Without knowing what the actual material being used is for the Citizen watches, I don't think we can say with any certainty whether the plating is effective or just for aesthetic appeal."
] |
[
"The \"ION plating\" on Citizen watches is not Titanium Nitride (TiN). Citizen's process produces a Titanium Carbide (TiC) coating, which is actually tougher than TiN. The TiC coating is a very thin layer of carbide ceramic crystal which has been permanently deposited and bonded on to the base metal. This layer is intrinsically extremely hard (TiC is very nearly as hard as diamond) because its constituent titanium and carbon atoms form a dense, highly symmetric, cubic structure. The high hardness of this layer prevents the base metal from being scuffed or scratched when exposed to abrasion. ",
"TiC, and some similar compounds such as tungsten carbide, are widely used in the metalworking industry as cutting tools. These carbide tools are capable of cutting metals faster and more cleanly than conventional tool steel, they also last much longer as they tolerate high heat without softening. Some exotic materials, like Inconel or Hastealloy, are practically impossible to machine without carbide tools. I should note that these tools are often ",
" carbide ceramic, and are not layers deposited on a base metal. In some circumstances steel tools are plated with TiC or TiN to improve their cutting properties and lifespan. ",
"Edit: TiC is usually black in color, but it can be doped with other elements (I seem to recall Cobalt, but might be off the mark) to produce different colors. ",
"Cheers. "
] |
[
"Edit: TiC is usually black in color, but it can be doped with other elements (I seem to recall Cobalt, but might be off the mark) to produce different colors.",
"I work with PVD coating and we use methane with titanium nitride for a range of colors: golden, copper, bronze or black."
] |
[
"What causes a blocked nose to remove all sense of taste?"
] |
[
false
] | null |
[
"You can find the basic answer with a simple Google search / on wiki. Please start there and come back with a more specific question."
] |
[
"There is no answer to why it happens when the nose is blocked only when u are sick"
] |
[
"Whether you have a cold or are plugging your nose, the effect is the same: odorants are not reaching your olfactory receptors."
] |
[
"How exactly do you explain the Feynman diagram for gluon radiation?"
] |
[
false
] |
So it means that the electron and positron get annihilated. But why is the initial positron travelling backwards in time? The annihilation supposedly produces a gamma ray. But does that gamma ray turn an antiquark into a quark, and make the antiquark emit a gluon?
|
[
"The arrow on the positron is not in which direction it is moving. It is the direction of charge flow. Positrons have opposite charge to that of the electron and thus the arrow is in the opposite direction.",
"The thing about the backwards time can be viewed in the way that the positron and the antiquark are going backwards in time and calculations accounting for positrons as being electrons that travel backwards in time give the same results as viewing it as a forward travelling positron with opposite charge to the electron. However, the arrows on the particle lines do not represent the direction in which the particles are travelling in time, they are always moving from left to right as the time axis points out. The arrows indicate the direction in which charge flows.",
"The rest is correct. An electron and a positron annihilate to produce a photon, the photon then decays into a quark and an antiquark of which the latter emits a gluon and since quarks can never be found alone, they're bound by the gluon."
] |
[
"It's standard to represent antiparticles as \"backwards in time\" (If you rotate the vertex, it becomes an electron changing it's direction after releasing/absorbing a photon).",
"In this case, the gamma pair-produces a quark-antiquark pair. Now the quarks can't ever be isolated. They're always bound together. And they're bound by gluons."
] |
[
"how and why does that happen?",
"In this case it has to decay or convert into something, you cannot have an interaction where an electron and positron collide and produce a single photon - you will violate the conservation of energy and momentum.",
"Any particle with charge couples to the photon, so any charged particle-antiparticle pair can be produced so long as there is enough energy in the collision to produce the mass of the outgoing particles. In order to produce outgoing quarks and a gluon, which will ultimately form a spray of hadrons, there must have been a lot of energy in the collision, so the electron and positron must have been accelerated to tremendous energies.",
"This sort of collision was seen at the ",
"LEP",
" collider at CERN, whose tunnel now houses the LHC. The outgoing quarks and gluons form three sprays of particles called jets. This diagram corresponds to a ",
"three jet event",
"."
] |
[
"If RNA Polymerase is needed for protein synthesis to make proteins and RNA polymerase is a protein, then what made RNA Polymerase?"
] |
[
false
] |
Also, what made/how did the first RNA Polymerase molecule form?
|
[
"In cells, it is a never ending cycle. RNAP makes mRNA, and if the mRNA encodes the RNAP genes then the ribosome makes new RNAP. Every time a cell divides it needs to start with a little RNAP from the previous cell so it can keep the cycle going.",
"When it comes to evolution, we have to speculate because RNAP evolved very early and we don't know of any cells that get by without it. The most popular hypothesis is the RNA world - the first RNAP would have been an RNA-based enzyme (ribozyme) instead of a protein-based enzyme. To support this view, the ribosome is primarily a ribozyme. ",
"But unfortunately we haven't identified a ribozyme polymerase yet, at least not one that works nearly as well as RNAP. Efforts to ",
"reverse engineer",
" such a polymerase in the lab have been somewhat successful, making ribozymes that can synthesize tens of bases in a row."
] |
[
"RNA polymerase transcribes its own pre-mRNA from the RNA polymerase gene. Then RNA polymerase is translated from its mRNA on the ribosome. We ",
" the first amino acids came together simply by associating (supramolecularly) with codons of similar hydropathies. The condensation reaction that RNA polymerase catalyzes does happen on its own, just more slowly. Thus a bunch of amino acids could have come next to one another in some specific sequence on some random stretch of RNA then condensed to a polypeptide that then went back and replicated more of that RNA whence it came.",
"There is also the idea of an RNA world in which RNA molecules acted as catalysts (ribozymes). Further, if DNA came first, then we can posulate that transcription from DNA to RNA occuring during a phase of single-stranded DNA could have happened by conjugate pairs just self-associating. Then we get back to the RNA polymerase RNA and how it could have formed (above)."
] |
[
"I think this is a bit of a chicken and egg problem, and you're probably not going to find the answer terribly satisfying; a RNA polymerase comes from an earlier transcript of RNA that was made by an earlier RNA polymerase. ",
"A polymerase produces an mRNA transcript from the DNA, and that mRNA is then used to synthesis a polypeptide chain that folds into whatever the native shape its supposed to assume. The creation of polymerase is no different in this regard. ",
"And this chain of polymerases making the next polymerases extends back probably as far as life has been around. ",
"We don't really know how the first proteins (any proteins, not just polymerases) came to be. It's one of the big mysteries of biology, partly because we simply don't have fossils that go back that far. ",
"One of the promising theories is that RNA itself might have served as a enzymes in the early history of life. Unlike DNA, and like a poly peptide, RNA can assume a variety of tertiary structures, which allows RNA to produce structures capable of carrying out behavior like an enzyme does. Indeed, one of the big pieces of evidence that suggest this is that Ribosomes, which generate polypeptides, are thought to use RNA to actually carry out the reaction that adds a new amino acid to the peptide chain. In essence, the protein components of ribosomes really just exist to support the RNA which is doing the work. And there are other ribozymes in the cell as well. ",
"So, tl;dr: RNA polymerases are produced by other, older, RNA polymerases, which in turn comes from older polymerases. This goes back probably to when life started on Earth, although at some point the role of polymerase was probably carried out by some sort of ribozyme that had a similar function. And we're not really certain about how protein synthesis began. "
] |
[
"Why do lower gears produce more torque?"
] |
[
false
] |
[deleted]
|
[
"It doesn't. Think about pushing a door shut. Is it easier to close it by the hinge or by the end? Where do you need to put more force to get it shut? Near the hinge. A moment equals length times force. The higher the length, the higher the moment acting on the point. If I have an actuator spinning a gear at the same speed, the change in angular momentum would stay consistent, correct? Torque/moment is constant. To keep that constant in the equation you put in the text, t = r * f, as radius goes down, force must go up. It can be easy to mix the two ideas in your head, but just remember the units. Force is in Netwons (Kg * m * s",
" whilst torque is in N*m. ",
"edit= formatting."
] |
[
"The ratio of the gears from the engine shaft and the output shaft determines the final torque. The torque coming out from the engine can be assumed to be fixed. Then the radius of the engine shaft gear determines the force at the edge of the gear: the smaller the radius, the greater the force. Then that force is translated into the output torque by the output shaft gear: the greater the radius, the greater the torque."
] |
[
"Careful! The rate change in angular momentum is torque! If the angular velocity is smaller, the angular momentum is smaller ( Momentum is mass * velocity).",
"edit: dont know why I'm getting downvoted, here's proof: ",
"https://physics.ucf.edu/~roldan/classes/phy2048-ch10_new.pdf",
"Same thing is happening to ",
"/u/concealed_cat",
". They're right as well. You can't just downvote someone on this sub because they go against what you thought (especially if proof is laid out). Please consider this folks before interacting on our subreddit."
] |
[
"Is there a gas lighter that hydrogen?"
] |
[
false
] | null |
[
"I don't think you quite know what a molecule is. Hydrogen is a single atom and a molecule is multiple atoms bonded together. No molecule is going to be lighter than the smallest atom possible."
] |
[
"An even though hydrogen comes in a molecule of two, it's still lighter than everything else."
] |
[
"No, hydrogen is the lightest gas when compared to other gases at the same temperature and pressure. The next-lightest is Helium-3."
] |
[
"When I try to push two magnets together and exert a lot of energy - where does the energy go?"
] |
[
false
] |
Pushing two north poles together on my neodymium magnets. I can never get them together, and it takes a lot of push them near each other. Where does this energy go?
|
[
"So it \"goes\" into potential energy. I never thought about it that way, thanks!",
"What happens when you push two electromagnetic things together (creating potential), then turn the magnets off? How does the conservation of energy apply there?"
] |
[
"that's an interesting question - basically you would be working against the energy being put in the system by electricity. not quite sure but i imagine it gets dissipated when the magnetic fields break down"
] |
[
"Should be lost as heat in the wire coil. Changing the current to turn the down the field will self-induce a back EMF. "
] |
[
"Neuroscientists, how to properly advance into sleep research?"
] |
[
false
] | null |
[
"Hey this kind of question of academia and grad school isn't what ",
"/r/askscience",
" is for. It is better suited for ",
"/r/AskAcademia",
" and ",
"/r/GradSchool",
". You should try your luck there. "
] |
[
"Alright. Will try it in these subs."
] |
[
"Not the right sub. Maybe try ",
"/r/Neuro",
" or ",
"/r/gradschool"
] |
[
"Would soap bubbles last longer in a micro gravity environment?"
] |
[
false
] |
[deleted]
|
[
"Bubbles would last longer, in that gravity would not be pulling them to the ground where they'd pop.",
"But bubbles would not exist indefinitely; the temperature of the surrounding air is still the same, thus water evaporating away from the bubble would still diffuse through the air at about the same speed, and the bubble would eventually pop."
] |
[
"Low gravity would have a second effect as well. Bubbles sometimes pop mid-air due to gravity pulling downward on the liquid in the bubble, causing the bubble to sag. When the bubble sags, the top of the bubble becomes thinner, eventually becoming thin enough to pop without anything touching the bubble. In low gravity, this effect would be reduced.",
"Edit: Added last sentence."
] |
[
"wouldn't the drier atmosphere cause the bubbles surface tension to poot out quicker?"
] |
[
"Is there any significance that water has a density near the round number of 1000 kg/m ^3?"
] |
[
false
] | null |
[
"Yep, it's by design. The gram was defined as the mass of 1 cm",
" of water under certain conditions. This wasn't actually the best way to define mass, because you have to be careful with the water purity and the temperature etc, so for a long time they actually just used a \"standard\" kilogram to define it instead, and now they define it based on Planck's constant. But these new measurements are basically all \"backwards compatible\" to the original definition, so you end up with the density of water being pretty close to 1 g/cm",
".",
"Similarly, a kilometre was defined as 1/40000th of the circumference of the Earth, as measured in a north-south circle that passes through Paris. We now have a better definition based on the speed of light, but the circumference of the Earth is still very close to 40,000 km."
] |
[
"As ",
"/u/astrokiwi",
" points out, that was the original definition of a kilogram.",
"The significance of that is up to you - how important ",
" it that most humans like nice round numbers? (with the possible exception of USAnians)"
] |
[
"If I may add, the measurement for distance is defined by the speed of light (velocity) and the frequency of a certain state of caesium-133 (time).\nA second is the time it takes Cs-133 to oscillate 9 192 631 770 times in their \"ground state hyperfine transition frequency\" and the speed of light is defined as 299 792 485 meters per second.",
"So if you send a beam of light in vacuum and count the 9192631770 oscillations precisely, you find the distance the light traveled in that time and divide it into 299792485 parts precisely, you have found an exact meter. Easy, wasn't it? xD",
"Gotta love the CGPM!"
] |
[
"Why do languages have genders (e.g. el/la in Spanish, der/die/das in German)"
] |
[
false
] |
Language is supposed to facilitate communication, but I don't seen any logical reason why a tree should use a different article than a flower. How does that make it easier?
|
[
"There have been proposed explanations in ",
"/r/linguistics",
" threads before, although I don't know which ones as the question has been brought up multiple times.",
"The most common proposal I've seen is that it having genders can reduce ambiguity in some cases. In Spanish, for example, there are two singular pronouns for the direct object pronoun \"it\": ",
" (masc) and ",
" (fem). Let's take the examples:",
"Apologies for the shitty Spanish--both are supposed to mean ",
" ",
" ",
". In English, the sentence is ambiguous as to whether you left your wallet at home or just your money. In Spanish, the ambiguity isn't present--in the first sentence \"it\" must refer to the money because it is masculine, while in the second sentence it must refer to the wallet because it is feminine.",
"So in languages with genders, it can reduce ambiguity by making it clear which noun a pronoun or adjective is referring to in cases where they have different genders."
] |
[
"This",
" is a relevant thread from ",
"/r/linguistics",
". Essentially, gender is only one kind of noun categorization. It's just the type that happens to be used by a lot of Indo-European languages. There's also ",
"this",
" thread, which is a discussion of how new nouns are assigned genders."
] |
[
"You're better off posting your question in ",
"/r/linguistics",
", I think. All the things I could post veer pretty quickly into wild speculation...and at least there, you can often find wild speculation backed by a university degree."
] |
[
"Can an illness such as the flu be passed through semen?"
] |
[
false
] |
I hope this isn't too vulgar, but I've been genuinely curious. Can the flu or the common cold be transmitted through fellatio and the ingestion of semen?
|
[
"To transmit the infection, you have to transmit ",
" cells. The testicles are cut off from the immune system (otherwise your body would attack your sperm since they contain varied genetic material and would be seen as \"foreign\"). So the answer to your question would be ",
" You can transmit through bodily fluids including saliva, however and if you're getting fellatio I'm sure there will be some saliva swapping. "
] |
[
"I am not sure, but I would think it is a moot point. If one is close enough to receive the semen, then I would think that person is well within the contagious zone from other means. Unless the semen contact were to happen in a multiple migs type situation, or a sperm donor situation. "
] |
[
"Semen is made up of a lot more than just sperm. It includes seminal fluid made by the prostate gland. ",
"Semen can and does contain infectious agents. Not sure about the flu virus, but you only need to think of the HIV. Transmitted by semen. ",
"If you ingest via fellatio, and actually swallow, a large portion of any infectious particles (viruses, bacteria) will be killed by stomach acid (which can get to a pH of 2, i.e. very acidic). ",
"Bottom line is YES, illnesses CAN be transmitted by semen."
] |
[
"Is it possible for a planet to exist without orbiting a star?"
] |
[
false
] | null |
[
"They are called rogue planets and, as they do not orbit a star, are even more difficult to detect than regular planet outside our solar system.",
"Estimations say that there are ~2 free floating planets per star in our galaxy.",
"http://en.wikipedia.org/wiki/Rogue_planet"
] |
[
"Well, yes. Although for all practical purposes it makes no difference if its a giant asteroid or a planet. If the colliding body exceeds a certain size, there won't be much left after a collision.",
"That being said, the likelihood of a free floating planet entering the solar system and crashing is extremely unlikely. Even the likelihood for one passing through is incredibly small if you look at the distances between things. The closest star is 4 light years away, that is over a thousand times further away than Pluto is from the sun. The likelihood of a planet having exactly the right vector to hit earth is a bit like dropping a grain of sand from an aeroplane and going through the eye of a needle on the ground. Although the more I think about, the chances of that happening are probably way bigger than the planet thing."
] |
[
"Well, yes. Although for all practical purposes it makes no difference if its a giant asteroid or a planet. If the colliding body exceeds a certain size, there won't be much left after a collision.",
"That being said, the likelihood of a free floating planet entering the solar system and crashing is extremely unlikely. Even the likelihood for one passing through is incredibly small if you look at the distances between things. The closest star is 4 light years away, that is over a thousand times further away than Pluto is from the sun. The likelihood of a planet having exactly the right vector to hit earth is a bit like dropping a grain of sand from an aeroplane and going through the eye of a needle on the ground. Although the more I think about, the chances of that happening are probably way bigger than the planet thing."
] |
[
"I understand how antibiotics work, but how do antiviral medicines work?"
] |
[
false
] | null |
[
"There are different classes of antivirals with different viral targets. Since viruses have no basic common features (unlike bacteria, which all have peptidoglycan cell walls), there are no broad-spectrum antivirals analogous to the beta-lactam antibiotics. So it's impossible to say how antivirals as a whole work, since they all pretty much have different targets. For an example, though, let's look at the most important and successful antiviral drugs-- those used in HIV treatment.",
"Anti-HIV drugs have several main classes, each of which targets a different HIV component.",
" These drugs bind to and block the action of HIV reverse transcriptase, which transcribes the viral RNA into DNA, which is then integrated into the host cell genome. This brings us to...",
" These drugs bind to and block the action of HIV integrase, which mediates the integration of HIV cDNA into the host cell genome.",
" Several of the HIV virus's proteins are produced as a single polypeptide, which is cleaved into its individual functional pieces by a viral protease. These drugs bind to and block the action of this protease, stopping the production of functional viral proteins.",
"I think there are several other classes of HIV treatments, but these are the main ones. There are other antiviral treatments out there, targeting the specific proteins of other viruses. "
] |
[
"As ",
"/u/a2soup",
" mentions, there are no broad-spectrum antivirals, due to the vast diversity and the lack of universally conserved viral genes that could serve as a drug target. In general, most antivirals work by inhibiting a viral protein, most commonly an enzyme. Since viruses are fairly simple beasts, with only a few types of genes, most of the drugs that target them fall into one of a few different classes. ",
"By far the most common type of antiviral are polymerase inhibitors. In order to replicate, viruses must be able to replicate their genome, and thus almost all viruses code for a polymerase protein that does this replication. Reverse transcriptase inhibitors in HIV are a classic example of a polymerase targeting drug. Many polymerase inhibitors are nucleotide or nucleoside analogues, which look enough like proper RNA or DNA building blocks to bind to the polymerase, but don't work correctly and thus gum up the works. Other examples of polymerase inhibitors are acyclovir for herpesviruses, sofosbuvir for hepatitis C.",
"Many viruses also encode a protease, which cleaves precursor proteins into their functional subunits. A number of HIV and HCV drugs are protease inhibitors.",
"Another essential step for all viruses is entry into the cell; in enveloped viruses this is always mediated by some sort of protein capable of fusing the virus's lipid envelope to the cell membrane. Several antiretrovirals (anti-HIV drugs) inhibit entry, most notably maraviroc, though this has been a less fruitful target than others, possibly because these proteins tend to be highly variable.",
"At the other end of the viral lifecycle, targeting viral egress is also useful for some viruses, most notably flu. Tamiful and several other anti-flu drugs inhibit neuraminidase, a viral enzyme that cuts off sugar molecules on the cell surface that would otherwise stick to the viral particles and prevent them from leaving the cell.",
"Integrase inhibitors are a more recent (and very effective) class of antiretroviral. Since integrase is only found in retroviruses, this class of drug is limited to HIV and other retroviruses.",
"Most existing antivirals fall into one of the above classes, although others coming down the pipeline target other proteins, or directly target the viral genome. There are also drugs that boost the immune response, such as interferon (typically a treatment of last resort because of the deeply unpleasant side effects), and antibody drugs like ZMapp, which bind the virus and either inhibit it or target it for destruction by the immune system."
] |
[
"Another class of drug used to treat HIV are fusion inhibitors. These drugs target and block the cell surface receptors utilized by HIV to infect cells. "
] |
[
"Our planet needs heat from the sun to sustain life. Would it be possible for an exoplanet or a rogue planet to achieve life-sustaining heat exchange through geothermal processes?"
] |
[
false
] | null |
[
"They're limited compared to the ecosystems that do fundamentally require the sun, but even on Earth, there are entire ecosystems that function this way, e.g., ",
"those that are developed around hydrothermal vents",
"."
] |
[
"While not a planet we have an example of at least an energy system like that with Jupiter and it’s moons. Particularly Io where it’s being gravitationally pushed and pulled so that it’s the most geologically active body in the solar system. Most don’t seem to think there’s life as we know it (all Jovian moons are coated in radiation from Jupiter) Europa is worthy of special consideration since the thinking there is that the same gravitational contortions are occurring but the ice shell on it protects the deep liquid ocean below from the radiation. Sorta like a world full of deep sea vents."
] |
[
"Only if the planet has enough gravity to hold an atmosphere so dense that it would retain the heat. Unlikely in an earth-like planet, maybe a mini Neptune or bigger planet can get warmer from inside than outside, in which case life in that planet would have to evolve to survive at extremely high pressure AND very cold temperatures."
] |
[
"How does medicine act differently when administered via different methods?"
] |
[
false
] |
If I have pills of acetaminophen, and I swallow them, they provide pain relief within usually 30 minutes or so. Would there be a different affect if I were to crush a pill and inhale the dust, specifically through the sinuses? What if I were to use the pill as a suppository? Would these different methods of administration affect how the medicine behaves?
|
[
"Well, I'm not sure about your question specifically, but you're basically talking about the bioavailability of drug forms. ",
"The first important concept is that anything that is absorbed from the esophagus to the upper rectum will go through \"first-pass metabolism.\" These areas all have venous drainage that goes through the portal system into the liver. The liver then metabolizes the drug, and whatever is left goes into circulation. Now, this can cause a couple things to happen. For some drugs, the first-pass metabolism is small enough that enough drug can get into the circulation to do it's job. Others have a large first pass metabolism and need a larger dose or different route of administration to get the desired effect. Yet others are metabolized ",
" their active forms, or into more active forms, etc. You get the gist. ",
"With that in mind, you can also consider alterations in this formula. For example, the mouth, nose, and lower rectum drain directly into the systemic circulation. As a result, sublingual tablets (like nitroglycerin) and enemas can avoid the first-pass metabolism and rapidly affect the entire body. Sublingual tablets also tend to use far lower doses, again because first pass metabolism isn't something you have to account for. ",
"Other drugs can be applied locally to exert their effects, like creams. This avoids potentially toxic effects on the body (e.g. Nystatin is a very toxic drug if it's in the blood, but can be used topically for fungal infections). Similarly, drugs like albuterol can be taken in an inhaled form (inhalers, for asthma). This delivers the drug quickly and directly to the lungs, and avoids direct action on other tissues.",
"I hope this make sense! Here's a bit more on drug bioavailability (and partially my source) if you are interested: ",
"http://tmedweb.tulane.edu/pharmwiki/doku.php/drug_absorption_distribution"
] |
[
"This is all correct, and I'll add on to it as well. First pass metabolism is really only possible only possible with drugs that are swallowed (called \"P.O.\" for \"per os\"), because other routes do not go through the hepatic portal system; P.O. administration is often used because it's non-invasive, and has use for prodrugs like Vyvanse (which is converted to amphetamine by the liver).",
"Meanwhile, other routes of administration such as intravenous (IV), intramuscular (IM), and subcutaneous (SQ) injections, sublingual (under the tongue) or buccal (held in the cheek), rectal, and intranasal, among others, are different ways to get drugs directly into systemic blood circulation, which also bypasses first pass metabolism. Each of these methods can have distinct advantages and disadvantages. For example, IM is now used over SQ (into the fat under the skin) for epinephrine, because this drug increases blood flow to the muscles, so uptake is faster. IV allows very strict control of blood levels of a drug but takes time for venipuncture, while IM is slower to take effect but easier to administer.",
"Finally, there are some more \"exotic\" routes of administration such as intrathecal injection (common in anesthesia) into a couple spaces in and around the meninges (which surround the spinal cord and brain), such as with epidural anesthesia like for pregnancy. They may also do many other intra-somewhere injections like intraarticular (into a joint) for very precise anesthesia, or some other desired effect. I'll also include topical administration here, by which drugs are directly applied to the skin to achieve effect; there also transdermal, which usually involves patches on the skin, but is actually allowing the drug to diffuse across the skin and into blood circulation.",
"Hope that gives you an even better idea of how varied routes of administration are, and why they are used in different situations."
] |
[
"Wow, I never knew that there were so many ways of administering medicine! Thanks for the reply, both of you."
] |
[
"Is there a way to prevent harm from a solar flare?"
] |
[
false
] |
I have seen a lot of information about solar flares becoming a possible threat in the near future. I guess the question is more directed towards a personal level. Is there any kind of material that could combat the energy given off from a solar flare? Like something to line a laptop case with in the inside so that, if something does happen, I could keep personal information safe. Or some material that could be spread on people's rooftops to keep their entire houses safe. On any level, is there a way to prevent, or at least lessen damage? Any information at all about solar flare prevention possibilities would be greatly appreciated.
|
[
"Laptops would be unaffected. The largest issue is long runs of conductive material. Power lines, twisted pair telephones, cable television, etc would all be affected. Everything else? Not so much. "
] |
[
"Interesting. So even if it knocked off all power, we would still be fine with batteries and solar panels?"
] |
[
"I don't know how a storm would affect solar panels, but I know most household goods would be untouched. This is, of course, assuming its a normal flare and not an anomalously large one. "
] |
[
"How does your body know something you ate is bad and needs to throw it up (or send it on an express delivery out the back end)?"
] |
[
false
] | null |
[
"Your stomach and digestion process is controlled by the incredibly powerful enteric nervous system. A set of neurons numbering in the hundreds of millions that can operate completely autonomously without input from your brain or spinal cord (often called a second brain because like an octopus leg it can carry our functions and process information by itself). It can react to the events within your stomach such as changing numbers of enzymes and bacteria and their secretions. It is this system which tells your body how to handle a case of runaway bad bacteria or deal with other such events."
] |
[
"Set that's what I mean, how does it detect something wrong. How does our stomach know something we ate is not safe to digest but we can't even tell by looking at it or smelling it"
] |
[
"Set that's what I mean, how does it detect something wrong. How does our stomach know something we ate is not safe to digest but we can't even tell by looking at it or smelling it"
] |
[
"Why do things only burn in high atmosphere?"
] |
[
false
] | null |
[
"They don't travel at the same speed when they are lower. For things coming in: The atmosphere slowed them down so much that they don't produce much heat any more when they enter the lower atmosphere. For things we shoot out: Rockets start slow, they only get really fast once they are in the upper atmosphere."
] |
[
"Read up on the ",
"Chelyabinsk meteor",
" of 2013. Of the roughly 480km depth of earth's atmosphere, it reached 29.7km above ground level before it exploded and broke into pieces due to the huge amounts of energy it was picking up from friction with the atmosphere as it became more and more dense.",
"As such, your initial premise is incorrect -- things will burn in the lower atmosphere. However the trajectory has the be correct, and the mass and composition sufficient to reach lower altitudes while retaining sufficient speed and remaining in sufficiently large enough pieces without breaking up."
] |
[
"Spacecraft reenter at somewhere in the neighborhood of 8 kilometers per second, at which point even the thin upper atmosphere offers a lot of resistance. The heating is not actually due to friction but rather the compression of air in front of the spacecraft--they're concentrating the heat from a large volume of air into a small space right in front of them.",
"By the time they reach the lower atmosphere, the spacecraft have already lost the vast majority of their speed to drag, and the thicker air continues to slow them, so there's not as much compression."
] |
[
"When anticipating a loud noise, does the body do anything outside of instinctively cover the ears?"
] |
[
false
] |
Is there some sort of mechanism inside of the ears that can reduce sound damage, or are the hands just about it?
|
[
"Yes, one such way is sound dampening via the stapedius muscle. The stapedius is the smallest muscle in the body and it acts to stabilize the stapes, which is actually the smallest bone in the body. ",
"The stapes normally functions to move against the oval window (the entrance to the inner ear) to cause a vibration that travels into your inner ear and gets interpreted as sound by the brain. The whole process of hearing is much more complex but I don't want to digress too much. ",
"The stapedius' job is to contract and pull against the stapes so that it can't vibrate as much against the oval window, thus causing less sound wave transference into the inner ear. It does this in anticipation of loud noises, typically when you're talking. Interestingly, that's why you sound different when you hear yourself on a recording vs when you hear yourself talking. When you're hearing the recording, your stapedius isn't contracting so you hear yourself as others hear you.",
"Hope this helps!",
"More reading:\n",
"https://en.m.wikipedia.org/wiki/Stapedius_muscle"
] |
[
"The facial nerve supplies the stapedius muscle, damage to this nerve (heard of Bell's palsy?) causes stapedius to paralyse, can cause hyperacusis where sounds are perceived much louder than usual. "
] |
[
"My condolences about the teenage girls, although I do appreciate the personal answer.",
"I suppose what I was wondering (even if I didn't know the terminology) was if the acoustic reflex could activate in anticipation of a loud noise rather than a reaction to it, but it's probably better to know the underlying mechanics."
] |
[
"Do successive covid reinfections increase or decrease in severity?"
] |
[
false
] |
Will they eventually wear-down a person's immune system or prime it to better handle it? eta... I mean an individual who gets it several times, which I guess would include variants. Particularly health workers who are continually at risk of exposure. With it being endemic, it's likely we all will potentially get more than one case of it even with vaccination, so with long-covid being a concern, will we all just eventually get weaker and more debilitated till it takes us out, or will we find it less and less of an issue?
|
[
"This is honestly a really difficult question to answer now given we have so little data on reinfection and long covid effects. ",
"There are signs pointing to the virus staying dormant / hidden after recovery (ie hepatitis or herpes), and potentially having longer term complications we might not yet be aware of but it’s still too early to tell."
] |
[
"Hey, my wheelhouse. In general, there are no guarantees, novel or new viruses in human beings tend to be more lethal at first and have a shorter duration. As time progresses the most advantageous route for a virus to take in order to be able to spread and produce the most viral load is to keep symptoms low, extend duration, and keep the host alive. So in a general sense, if COVID becomes endemic and never goes away and continually mutates, the chances of it becoming more lethal instead of less is pretty low.",
"That said, we have very little info on reinfection, strains, and a whole mess of other data which could end up putting covid into a less expected path which could make it more deadly instead of less. Each mutation brings new challenges; however, the hope is that a virus should become more transmissible and less deadly with each new iteration. Unfortunately, there is on way to guarantee this will happen."
] |
[
"They should decrease in severity but there's no universal rule. Because your immune system remembers it even when there's no or little antibodies floating at moment",
"According to some continuous exposure won't work as a immune's training tool unless symptomatic reinfection happens once again, but vaccines do. I've tried to research this, found no conclusive data so this part of the answer is theoretical in nature."
] |
[
"What stops bacteria from living on soap?"
] |
[
false
] |
What exactly is soap made of, that it kills/removes bacteria? Why hasn't bacteria adapted/evolved to this? Thank you!
|
[
"Detergents (soap) dissolve the cell membrane, which kills cells. All cells and enveloped viruses are destroyed by detergents. Bacteria can't readily become resistant to soap because it essentially dissolves the whole cell. Small mutations or genetic variations upon which natural selection works do not give an advantage in a situation like this. Why does't soap kill our own cells? Well it does. Very easily, if it gets access to living cells. But our living cells are protected by a thick layer of skin, the outermost layers of which are dead cells and cross-linked proteins, which can't be killed or readily dissolved."
] |
[
"Yes, you're right, washing an open wound with soap will damage some of our own cells, but it also does a good job killing any bacteria that are exposed. This is why hand washing is important for infection control."
] |
[
"No, NaOH is used to make soap, but the final product is within physiological pH. "
] |
[
"Ask Anything Wednesday - Engineering, Mathematics, Computer Science"
] |
[
false
] |
Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical post? No question is too big or small for AAW. In this thread you can ask any science-related question! Things like: "What would happen if...", "How will the future...", "If all the rules for 'X' were different...", "Why does my...". Please post your question as a top-level response to this, and our team of panellists will be here to answer and discuss your questions. The other topic areas will appear in future Ask Anything Wednesdays, so if you have other questions not covered by this weeks theme please either hold on to it until those topics come around, or go and post over in our sister subreddit , where every day is Ask Anything Wednesday! Off-theme questions in this post will be removed to try and keep the thread a manageable size for both our readers and panellists. Please only answer a posted question if you are an expert in the field. . In short, this is a moderated subreddit, and responses which do not meet our quality guidelines will be removed. Remember, peer reviewed sources are always appreciated, and anecdotes are absolutely not appropriate. In general if your answer begins with 'I think', or 'I've heard', then it's not suitable for . If you would like to become a member of the AskScience panel, . Past AskAnythingWednesday posts . Ask away!
|
[
"It showed that mathematics cannot be automated.",
"In the 1920s Hilbert had famously asked for an axiomatization for all of math in which proofs could be found by machine. In 1931 Gödel showed that it's impossible to axiomatize all of math. And in 1936 Church and Turing showed that, even if you settled for only a piece, unless that piece was trivial, there wouldn't be a way to automatically tell the truths from the non-truths. ",
"Regarding the halting problem in particular, consider Goldbach's conjecture. It states that every even number greater or equal to 4 can be written as the sum of two primes. You can easily write a computer program that searches for the first counterexample to this conjecture. This program will then run forever if and only if the Goldbach conjecture is true. If the halting problem was solvable, you could just feed this program to the halting machine and turn the crank to see if Goldbach's conjecture was true. A similar trick could also be done to settle the Riemann hypothesis. And it would've saved Andrew Wiles a lot of work on Fermat's last theorem.",
"I hope this gives you a taste of the immense importance of the halting problem."
] |
[
"Theoretical computer science question: what's the deal with the halting problem? I understand the premise of the question, as well as the outline of the proof that no algorithm could answer for every program. But what impact does/did it have on the field of computer science?"
] |
[
"Could dark matter particle be a particle with an imaginary charge? ",
"Dark matter does not interact with electromagnetic radiation, which is produced by electrically charged particles. Charge is quantized, which means there is a meaningful way of representing charge as rational numbers: positive, negative and even fractional.",
"Would a particle having imaginary charge make sense theoretically, and if so, would the matter constituted of such particles be undetectable by electromagnetic radiation, just like dark matter is?"
] |
[
"Would an EMP blast affect human brains?"
] |
[
false
] |
My understanding is that EMP blasts are strong, short-lived magnetic fields that can induce voltage in a loop (frying some electronics in the process, as they are famous for). But the brain has ions of charge floating in a slightly conductive fluid. Would any areas of the brain be considered "loops" that current could be induced in? Would a strong EMP blast affect human brains?
|
[
"An electromagnetic pulse works on the displacement of electrons (as far as my understanding goes). The electrical activity of the brain is mediated by sodium and potassium, which are vastly heavier than individual electrons. That being said, a study showed that electromagnetic pulses can affect different areas of the brain:",
"(",
"http://news.bbc.co.uk/2/hi/health/8593748.stm",
")"
] |
[
"Check out ",
"Transcranial magnetic stimulation",
"Basically EMP in a small scale controlled way."
] |
[
"This is not true. The mechanism of action of TMS on the brain has nothing significant to do with the inverse compton effect generated EMP like from a nuclear bomb. Nor with the more run of the mill EMP from flux compression generators or virtual cathode oscillators.",
"With TMS you're using near field induction from a rapidly changing magnetic field generated by a kiloampere current a centimeter away from the brain. The rate of change in the field strength is proportional to the voltages induced and typical field strengths are from 2-5 tesla. These pulses typically last a couple hundred microseconds.",
"With EMP from the scattering and acceleration of electrons from the photoelectric effect of xray photons from a nuclear bomb in the high atmosphere there are multiple time scales and differentiable effects. For more detail see, ",
"http://www.empcommission.org/",
" . ",
"The gist, in contrast to TMS, for the majority of the energy the timescales are much shorter and it is a far field (millions of times the wavelength of the waves) propagation through an electromagnetic wave. It is not directly inductively coupled.",
"Neurons do not work like electronics. While there is a voltage associated with an action potential in a neuron the actual charge movement is all completely transverse to the direction of the action potential. The charge is only moving ~15nm across the bilayer lipid membrane of a given axon. While electrical potential transients (voltage) can depolarize (or hyperpolarize) a neuron extremely fast transients of some microseconds (like EMP) are well below the integration timescales for charge movement in neurons. It won't effect functioning.",
"By the way, to the op, this question has been asked tens of times already and there are good answers. See ",
"http://www.reddit.com/r/askscience/comments/z3lkd/if_you_were_hit_by_an_emp_pulse_would_you_notice/",
" for example."
] |
[
"Is there a theoretically perfect immune system? What scientific breakthroughs would be possible if a person had one?"
] |
[
false
] | null |
[
"Amazing? Yes. Perfect? Not so much. While it's possible for individuals to be very healthy and to develop immunities to variety of viruses, said viruses change over time. (This is the reason you need a new flu shot every year)"
] |
[
"I read somewhere that sharks have better immune systems but a vastly decreased chance of autoimmune disorders. Is this true and if so why?"
] |
[
"I read somewhere that sharks have better immune systems but a vastly decreased chance of autoimmune disorders. Is this true and if so why?"
] |
[
"What is the mechanism by which molecular orbitals hybridize?"
] |
[
false
] | null |
[
"but it's important to bear in mind that's not what's really going on \"down there\". ",
"What is really going in \"down there\"?\n Thx"
] |
[
"Oh. So physics isn't looking for what is really happening, just a bunch if models to explain why things happen. Its a bit depressing that we will never really know :("
] |
[
"I think it is rather unfair and inaccurate to say hybridization is a mathematical fiction while touting molecular orbital theory as truth. In both models we use linear combinations of atomic orbitals (LCAOs) to describe the bond angles in central atoms; combinations of wavefunctions are only as fictional as the wavefunctions themselves, so if you want to make the claim that VB theory is a bunch of horseshit, the Shrodinger equation is probably a bunch of horseshit to you too.",
"To address your post further down the thread, hypervalent molecules can easily be described within the VB model via 3c4e bonds and resonance, just like in MO theory. And yes, while there are disagreements as to whether the d orbitals are actually used for hybridization, I don't really see why VB theory has to be shunted just because MO theory provides a more robust picture in some cases (eg H2O).",
"I think you may be confusing the hand-waviness of VSEPR with VB theory; they are not the same. VSEPR is a bunch of ad hoc bullshit that mostly works. VB theory is mathematically sound, and LCAOs are the tie-in with MO theory."
] |
[
"In the 'Two Slits' experiment when only one electron is fired, how does it produce the pattern that it does?"
] |
[
false
] |
If there was only one electron that was exhibiting wave-like properties, then shouldn't there be an chance that it could end up anywhere on the 'back wall'? How could one single wave produce a pattern as if there was a cancellation at certain points caused by the interaction of two waves?
|
[
"There is no particularly intuitive explanation. Basically, it comes down to the fact that fundamentally, elementary particles (photons, electrons, etc) exhibit a particle-wave duality. They act as particles, and as a wave, at the same time. That means that while they can be shot as a single particle, they still act as if they were a wave. You can't think of them as a particle like you would think of a ball or bead.",
"It isn't intuitive, but really, nothing about quantum mechanics is. ",
"This video might help you: ",
"https://commons.wikimedia.org/wiki/File:Wave-particle_duality.ogv"
] |
[
"The electron is a travelling wave packet, and when the slit width is on the order of the deBroglie wavelength of the electron, it will diffract just like a wave. Since the electron's position wavefunction is a probability distribution, the pattern takes a lot of iterations to become apparent. "
] |
[
"Because the electron probability distribution passes through both slits simultaneously and interferes with itself. "
] |
[
"What is a flame made of?"
] |
[
false
] |
Is it just really hot fumes/particles/dust/whatever coming from the combustion? Or is there some additional property in the actual flame?
|
[
"It's oxygen, the fuel (methane or cellulose or whatever), and the carbon dioxide (and some water and soot, depending on the reaction) product. The glow is from blackbody radiation, which is what is given off by hot things by virtue of their heat."
] |
[
"Thanks!"
] |
[
"The glow is from blackbody radiation, which is what is given off by hot things by virtue of their heat.",
"The black body radiation definitely exists in the flame, but in real life it's almost always overwhelmed by trace amounts of sodium and the like. That's why most fires are yellow.",
"Pure uncontaminated flame is actually pretty much invisible in day light. E.g. pure alcohol burning. Unless it's burning really hot (oxy-acetylene) in which case it glows an angry blue-white."
] |
[
"What factors determine the recovery rate of a physical wound?"
] |
[
false
] |
Other than severity of the wound, of course.
|
[
"For wound healing to occur various physiological processes need to occur. For example, your body needs to stop the area from bleeding, clean up the area, grow new skin, and repair the underlying matrix. ",
"This process can be complicated by a number of factors. For example a wound will heal differently based on if it is re-approximated (like with sutures) or left open. The sutured wound is said to heal by primary intention where as the open wound is said to heal by secondary intention. ",
"The mechanism of the wound can affect healing. You have acute wounds (like scraping your knee) and chronic wounds (like bed ulcers). There are wounds from blunt objects and sharp objects. Were you stabbed by a clean knife or dirty shovel? Wound location factors in. Wounds can have various depths and so on. ",
"For the sake of discussion, lets say I make a 5 cm cut with a scalpel on you right arm over your bicep. Various things about you can make that wound less likely to heal properly. If you have trouble supplying blood to that area (as in peripheral arterial disease or diabetes) various factors in the blood may not make it to the wound and thus delay healing. If you are 30, your wound will heal better than if you are 80 due to changes in collagen and thinning of the dermis. If you are malnourished you may be more likely to get an infection and infections throw a big kink in wound healing in general. Certain vitamins and minerals are necessary for collagen to regrow. Smoking can lead to fluctuations in blood supply and potentially impaired ability to fight off infection. And the list goes on. "
] |
[
"I've heard from treatments done to my nephew(he has GBM in his spine), sticking him in a pressurized chamber, like for the bends",
"Is this proven to have a positive effect on recovery times?"
] |
[
"Hyperbaric oxygen therapy is somewhat controversial. Some studies show improvements in certain subgroups, others do not. One thought is that it improves oxygen delivery to chronic wounds in people who have diseases like diabetes or previous radiation treatment where blood flow may by inadequate. Another is that it might be useful in people who have skin grafts or flaps. On the non-wound healing side of things, some people contend that it might help sensitize tumors to radiation therapy. ",
"Cochrane (source of high quality systematic reviews) has quite a few reviews out on hyperbaric therapy. ",
"Hyperbaric O2 significantly improves short term healing, but not long-term",
"Insufficient evidence for hyperbaric O2 in grafts or trauma",
"Hyperbaric O2 may help in radiation therapy of certain tumors"
] |
[
"Do magnetic lines of force have diameter?"
] |
[
false
] | null |
[
"Magnetic field lines are just a visualization of the vector field. They are not physical, and they don't have any width."
] |
[
"Ah, so why does it look like the iron filings are following discreet lines? Is that just something to do with how the iron is shaped? "
] |
[
"Is that just something to do with how the iron is shaped?",
"Yes. The iron filings are magnetized in a way that the field is a little bit stronger through them than just outside them. So the filings all align together and give the illusion of \"field lines\"."
] |
[
"Are \"mini black holes\" really even black holes?"
] |
[
false
] |
Using particle accelerators we can create "mini black holes." By this, do we just mean something as dense as a black hole? Isn't a black hole, by definition, something with so much gravity that light (that it produces) can't escape? Don't you need not just density but a ridiculous amount of mass for this phenomenon to occur?
|
[
"Well, some people have theorized we can create mini-black holes with a particle accelerator, but I've never seen it confirmed. They would be real black-holes, by definition a black hole is any grouping of matter smaller than in its own ",
"Schwarzschild radius",
"."
] |
[
"Even if they didn't evaporate, wouldn't the radius be so small as to be unlikely to ever encounter another mass particle? "
] |
[
"'micro' black holes will evaporate really, really fast thanks to Hawking Radiation. I believe the mass necessary to make something dangerous to us is many orders of magnitude beyond anything we are capable of. I don't really think of them as black holes, mostly because they are harmless.",
"http://en.wikipedia.org/wiki/Hawking_radiation"
] |
[
"Is there any way for us to know how far our planet has travelled, knowing that even galaxies are in motion?"
] |
[
false
] | null |
[
"This is not a well-defined question. In the reference frame of Earth, Earth has moved exactly 0 meters. In the reference frame of the Sun, Earth moves about 10",
" meters each year. There is no absolute notion of motion, and so no absolute notion of distance traveled."
] |
[
"Thank you at least for trying to answer. I was more wondering say since I've been born how far has earth moved from the supposed \"original\" spot. "
] |
[
"I already answered you. There is no answer to that question. It depends on your reference frame. "
] |
[
"When I inhale a scent, do I also exhale that scent? "
] |
[
false
] | null |
[
"\"Scents\" are aromatic molecules that pass by your olfactory receptors, binding to them, and sending a chemical message to your brain. Not everything binds, however, and may pass into the alveoli of your lungs. Then, when you exhale, the molecules are expelled. So in a sense, you are exhaling the smell. More specifically, you are exhaling the aromatic molecules that bind to olfactory receptors, and they return to the external atmosphere. "
] |
[
"Came here to say this. This is correct. Your receptors will pick up some of the molecules but not even close to all of them. Many of those molecules will pass back out."
] |
[
"The receptor sites are already being used."
] |
[
"Great Idea - but I'm not sure if the science works."
] |
[
false
] |
I thought of this while at the gym the other day. It sounds like a totally doable - and marketable idea. Either its a great idea and I'm the first to think of it or it is totally impractical and cannot be done. I'm asking you guys for your input. I realize that someone else could "steal" my idea but I've come to terms with the fact that without someone specializing in the skillset necessary it won't happen anyhow. Here it is - Color changing polyurethane. Specifically I mean Hydro Chromic floor coating. All gym, basketball, and other wood floors are coated with polyurethane. It is great when dry but when wet will become incredibly slippery and dangerous, as well if it is wet long term it will damage a floor. I know there are chemicals that change color temporarily in the presence of polar water molecules so why not add these to polyurethane so it can give an obvious warning that the area is wet. If it is stable you could actually print "caution wet floor" on top of the first coat of regular polyurethane and any time the floor was wet it would indicate exactly where the floor was still wet. It seems like one of those things that would instantly become a must have for large businesses trying to avoid lawsuits because it will always be a 100% reliable way of indicating where and when a floor is wet. As well on sports courts it could indicate to athletes where the floor is slippery so they can avoid it or wipe it up. Anyhow, maybe I'm giving away what could become a million dollar idea or maybe it is crap. You tell me. I demand SCIENCE.
|
[
"Floors are waxed. ",
"Waxed floors will not let water come in contact with color-changing molecules. "
] |
[
"Wouldn't this defeat the point of the wax being protective by making it reactive?"
] |
[
"Wouldn't this defeat the point of the wax being protective by making it reactive?"
] |
[
"Why is it that when we tickle ourselves, we're not ticklish, but when others tickle us, we are?"
] |
[
false
] | null |
[
"Your body is able to cancel out the \"feeling\" of being ticked when you tickle yourself. It can't predict the tickling when others do it, hence why some people are ticklish. ",
"If you plug your hand into a robotic hand, and use the robotic hand to tickle yourself, you still won't feel \"tickled\" ",
" you input a delay between your motion and the robotic hand's motion. Once this delay reaches some threshold I don't remember, you will feel tickled even though you are controlling the hand through a delay. This is because the brain loses the ability to cancel your nerve signals after a short period of delay."
] |
[
"There is a TED talk about this that I posted here in response to a similar question.",
"Found ",
"it"
] |
[
"Apparently people suffering from schizophrenia can tickle themselves.",
"See also ",
"http://www.ncbi.nlm.nih.gov/pubmed/10943682"
] |
[
"Does relativity make any of Kepler's laws false?"
] |
[
false
] |
[deleted]
|
[
"This depends on what you mean by \"false\". Relativity has small, but observable, effects on all of Kepler's laws. ",
"In fact, the anomalous precession of Mercury's orbit was one of the earliest pieces of supporting evidence for general relativity."
] |
[
"That's correct."
] |
[
"Correct me if I'm wrong, but doesn't relativity just simplify to yield Kepler's (and Newton's) laws in cases of (relatively) low gravity and velocity?"
] |
[
"Why is it so difficult to create a camera that takes a picture as well as the eye can see?"
] |
[
false
] |
Is it the fact that the eye is based on chemical reactions? How much of it based on the ability of the eye and how much that the brain corrects things? Things like: Blur, low light, change of focus, optical artifacts (reflections, light points, dark splotches), Depth of field, Wide angle
|
[
"A lot of it is post-processing - about half of our brain is in some way devoted to vision, and the image we 'experience' is very heavily processed."
] |
[
"Correct. The OP is asking a question based on the assumption that the visual data coming from our eye is the same as the visual data we perceive, but these are two different things. The actual image that's landing on our eye's physical lens is generally crappy. It's upside down, it's full of holes, it's blurred together with previous and subsequent exposures, it's crisscrossed with scratches...you'd never make heads or tails of it if you presented it as a single photograph. It's our brain that fixes everything and turns the image into something presentable. Not only that, but our brain also takes that data and uses it to \"clean up\" previous images that were similar, in order to clear out those holes, scratches, scars, etc. This not only contributes to the \"persistence of vision\" effect that allows us to watch movies, but it fills in the blanks when we miss crucial information, like blinking while trying to catch a baseball. ",
"And when it comes to vision processing and long-term memory, the brain's just as meddlesome! For example: describe the look of the waiting room at your last doctor's visit. Psychologists have found that your description will most likely be disturbingly predictable and generic. This is because our brains like to average out unimportant visual information. If you ",
" to see off-white walls, hand rails, and outdated magazines on faux-wood coffee tables at a doctor's office, that's what you'll remember seeing, even if it's 100% wrong.",
"Our brain will also ",
" visual information based on our emotional state. For example, if a short guy breaks into your house and robs you at gunpoint, when the police arrive and ask for an account, there's a 70% chance you'll describe him as being tall. Which is why eye witness testimony is unreliable. Our brains emphasize the appealing qualities of things we like, as well. In the end, we're left with a vision of reality which helps us make better personal decisions, but fails to be empirically accurate.",
"tl;dr - your eyes see better than a camera because your brain told you they do."
] |
[
"Yeah, most of those optical illusions showing how your brain can be easily \"fooled\" are really tapping into the post-processing that in many ways provides you with a more accurate picture of the world (under normal conditions) than what an ordinary camera would get."
] |
[
"Can a planet have a non-rocky moon (i.e. gas)?"
] |
[
false
] | null |
[
"A gas moon would have to be very massive, enough to hold a significant atmosphere. I'm going to assume your moon has the size and mass of Neptune.",
"For it to be a moon, it would have to be orbiting a much more massive planet. If the mass ratio is not big enough then it will be a ",
"double planet",
" instead (Okay, actually the mass ratio is not the only variable here. If the bodies are too far apart from each other than this can also shift the barycenter out of the major body, and so they'd be orbiting each other instead of the smaller orbiting the larger.)",
"But the major planet cannot be more than 13 Jovian masses. At this point it would be able to fuse deuterium, and so we'd call it a ",
"brown dwarf",
" instead (which is technically not a star, but also not a planet).",
"The ratio between 13 Jovian masses and Neptune's mass is 150. The Earth-Moon system has a mass ratio of 81. Therefore, yes, it is possible.",
"However this kind of system is unlikely to form naturally. Moons formed from an accretion disc are usually a lot smaller than their parent planet.",
"Fun fact: the Earth-Moon system close to the boundary between a double planet and a planet-moon system. The barycenter is 1000km below Earth's surface, or 1/6 of Earth's radius.",
"Edit: spelling, links"
] |
[
"I don't know if IAU has come up with a precise definition, but I would define gas giants by ",
". Titan does have a solid surface, the Huygens probe stood there and ",
"took pictures",
". In a gas giant you'd just keep going deeper and deeper until temperature and pressure destroy your probe. In the case of Jupiter hydrogen is expected to become a supercritical fluid and much deeper it is supposed to be in a metallic state, but in any case ",
". There is no precisely definable surface."
] |
[
"An Earth-massed ball of nitrogen and oxygen would be much bigger than Earth itself due to their low density. Since gravity falls off with the square of the distance, I doubt it'd be able to hold itself together.",
"I assumed a Neptune-like body because that requires no speculation."
] |
[
"Are there any organisms for which a male and female specimen appear so different that one would never classify them as the same species without observing them mating or sequencing their genome?"
] |
[
false
] |
[deleted]
|
[
"Perhaps the anglerfish fulfills your desire?"
] |
[
"Video for reference ",
"http://www.youtube.com/watch?v=EWVfCGdlQPE&feature=youtube_gdata_player",
"Edit: I expect someone to post this in TIL in the near future. "
] |
[
"I guess the well known (among parasite enthusiasts) crab parasite ",
" will fit your criteria.",
"The female and male both start out in life as small bits in the ocean. The female 'takes over' a crab, then the male docks with the crab+femala, and they mate.",
"The life of a Sacculina would make a good alien horror film. It begins life as a swimming larva. As soon as the female larva smells a crab, she goes after it and looks for a soft spot in one of its joints. Via this soft spot, she spouts several cells into the body, which form a slug, discarding the majority of her body (a kind of molting). This slug crawls down deep in the underside of the crab, where it starts to grow. She develops multiple tendrils which start to move throughout the crab's body, sometimes even surrounding the eyes. She forms a kind of knob (see photo) in the underside, situated precisely where the crab would normally carry its eggs. The knob slowly chips away as the crab moves around in the water, revealing an opening. Unless a male comes around, the female will remain at this stage the rest of her life. However, should a male Sacculina land on the crab and find the miniscule opening, then he too injects part of himself into the knob, molting away the rest of his body. The male now searches for the necessary parts of the female, where it fuses and starts producing sperm. He remains here the rest of his life. Actually, the female has capacity for two males. The two males continually fertilize her eggs, producing thousands of larvae every few weeks.",
"Source",
"However, for a more gripping tale, you absolutely must read the August 2000 edition of Discover Magazine's ",
"full article"
] |
[
"Ask Anything Wednesday - Economics, Political Science, Linguistics, Anthropology"
] |
[
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!
|
[
"I seem to remember a Scandinavian country doing an experiment with universal basic income. Did that happen, and if so, what were the outcomes?"
] |
[
"I'm looking for videos on foundations of mathematics that would be appropriate for a seven year old. Does anyone have any suggestions?",
"Also is a question asking for recommended books, articles, videos, etc. on a specific topic appropriate for this sub?"
] |
[
"If something could travel with a velocity an order of magnitude faster than light, would we be able to identify it and measure its velocity?"
] |
[
"MRI Physics: Why is there a need of using multiple phase-encoding sequences for signal acquisition in MRI?"
] |
[
false
] |
I am going to be starting my PhD and I have been reading up on different modalities before I start school. Right now I am on MRI and I am curious as to why we need multiple phase encoding sequences for image reconstruction? If there is a gradient that is acting along the y-axis, don't the phase angles differ per row anyway? So for example, if you have three rows in your image, going from -y to +y, wouldn't the phase be +120 for the top row, 0 for the middle and, -120 for the bottom? Can these minute differences not be discerned from one k-space data set only? Why is there a need for different gradients to read these images? Any insight would be much appreciated. Thank you.
|
[
"There's a whoooooole bunch of different ways to think about it, and I'm just going to give one, which may or may not make sense to you. Each point in k-space corresponds to a particular Fourier encoding function - a spatially varying sinusoid with a particular frequency and rotation angle (if you were to plot this it would appear as a series of light and dark bands of some paritcular width - corresponding to frequency - and rotated at some angle; a \"stripe pattern\"). If you set the phase encode gradient to some level and play out the frequency encode graident, you're only sweeping across one line of k-space. The phase variation that exists across your matrix - as you correctly mention - only correpsonds to the encoding function at a single value of the rotation angle (i.e., a single stripe pattern). You need to project you object against all the encoding functions (all the stripe patterns), so you need to sweep both the phase and frequency gradients."
] |
[
"I might be misunderstanding your question (I don't do imaging - NMR and previous EPR person here), but the number of lines and how far you go out into k-space impact your field of view and coordinate-space resolution.",
"There's this nice figure in Ernst/Bodenhausen/Wokaun's text in the imaging chapter that made sense to me (you have two circular/cylindrical phantoms in a larger circle/cylinder, and multiple projections need to be made to properly reconstruct the image), but it's been a long while since I read that chapter in any detail. It's also at home, so I'll have to wait to check my memory. "
] |
[
"Hey, thanks for your response. Unfortunately, I am still having a little bit of a tough time understanding.",
"You mentioned that with one gradient, you are only sweeping across one line of the k-space. Sweet, that I get! But then, my question is, is if you get a varying phase angle across the rows of your image, why do you need more lines in the k-space? Is it because you cannot measure this phase change in just one image?",
"Hopefully if you have some time, maybe you can hit me with some of the different ways to think about it? Thanks a lot for your help. "
] |
[
"When I use differentials in my physics class, what am I actually doing, and why is it allowed?"
] |
[
false
] |
In calculus, we constantly remind ourselves that differentials such as dy and dx are not actual numbers or even limits, though dy/dx is. But my physics class has me writing expressions like like, for example, dW = λ dl and subsequently integrating them. What's going on here?
|
[
"You're constantly using the Chain Rule. ",
"The symbol \"dx\" is not a number. If it were a number, there would have to be a way for me to figure out what the number is, so which one would it be? No matter what you pick, it would be too large for anything we do in calculus, so it can't be a number. Limits are always numbers or infinity, so it can't be a limit. So what is \"dx\"?",
"The symbol \"dx\" is a vector. More precisely, it is a \"",
"Vector Field",
"\". This means that at every value of x, I can find a vector dx and it can change as x changes. This is no ordinary vector that is just an \"arrow with length\" or \"a 1D array of numbers\", this is more abstract/meaningful than that. If f(x) is a function, the df represents how much the function f is changing at any given point. It's technical definition is beyond the scope of this post, but this is what it means. The function g(x)=x is a function and we just say that dx is another way to write dg. So dx represents how much the function g(x)=x changes at a given point.",
"Now, if we're in a single dimension, then df will be a 1-dimensional vector and if I have f(x) = F(G(x)), how does df compare to dG? Since we're in one dimension, the only option for df to be some real number times dG. This number is given by the Chain Rule and that real number is F'(G(x)). This means that df=F'(G(x))dG is another way to state the Chain Rule. This means that for arbitrary f(x), we have df=f'(x)dx, since f(x)=f(g(x)) because g(x)=x.",
"Note that it is very, very important to ",
" view f'(x) as a fraction. df/dx is ",
" a fraction. All that df/dx is is another way to say \"The derivative of f(x) with respect to the variable x\". It is not a ratio in any sense of the word. We only use the notation f'(x)=df/dx because the Chain Rule then kinda takes the form of fraction multiplication: df = (df/dx)dx. But this is where the analogy stops. Addition of fractions, multiplication of arbitrary fractions etc don't work. The only thing that kinda looks like fractions is this kind of cancellation and it is just using the Chain Rule. It is good to think \"And now, by the Chain Rule\" whenever you cancel out stuff like this instead of \"it's a fraction, so we cancel\".",
"It may be tempting to think \"Well, if dx is just a 1-dimensional vector, and 1-dimensional vectors are just the real numbers, then I ",
" be able to divide because you can divide real numbers!\". This is false. 1-dimensional vector spaces are ",
" just the real numbers, just like n-dimensional vector spaces are not ",
" R",
". It is always possible to find a way to identify a 1-dimensional vector space with the real numbers, but this identification is ",
". There are infinitely many ways to do this identification and all of them give different results if you start trying to divide. The simple fact is that if you just have a vector space, then you can add vector together and multiply them by real number, but you ",
" multiply and divide vectors. Regardless of dimension. df is a vector, dx is a vector, we cannot divide them.",
"This view generalizes nicely to larger dimensions. If f(x,y,z) is a function, then df is still a vector that tells us how f changes at each point. But just as x,y,z give us a way to uniquely specify each point, the vectors dx, dy, dz (given by the functions g(x,y,z)=x etc) give us a way to uniquely specify each df. That is, df is a 3-dimensional vector and dx,dy,dz provide a basis. The coordinates for this basis are then f",
", f",
" and f",
" so that df=f",
"dx+f",
"dy+d",
"dz, which is the Total Derivative. How changing coordinates works for something like this is more complicated than one dimension, but is still given by the Chain Rule, it's just stated in terms of Jacobians and such. "
] |
[
" It is a damn shame that people are actually ",
" ",
"/u/functor7",
"'s response. His response is 100% correct and gives an accurate description of differential forms, an object that often remains completely mysterious to most math/physics students even well into graduate school. Save your downvotes for responses that are actually ",
".",
"Of course, this is all correct and precise, but it seems unnecessarily complex for the purpose of answering the OP's question. In an intro physics course or a calculus course (basically any math before differential forms), it's best just to understand the differentials as \"little pieces of a whole\". The differentials only ever really appear as a tool to set up an integral whose value is whatever you want to calculate.",
"For instance, what is the work done in siphoning a tank of water of some constant cross-sectional area ",
" and height ",
"? In intro physics, this is calculated by first calculating the work done on a slab of cross-sectional area ",
" and \"small height\" ",
", which is much, much simpler. (The mass of the slab is ρ(h)A(h)",
", and the work done to raise it a height ",
" is just (ρ(h)A(h)",
")",
", which is the usual \"W = mgz\" for work done by gravity). Express ",
" in terms of ",
", and everything is in terms of ",
".) Then the total work is the sum of the work done on each of those slabs. The sum of such differentials is just an integral.",
"The understanding is that if we wanted to be precise, we could, by first expressing the total work as a Riemann sum and taking limits as ",
" --> 0. It's obviously easier just to understand that any time we add a lot of \"little things\" (differentials) we end up with an integral. In fact, that is probably the best way for students new to calculus to understand an integral and its applications. It's just as ",
"/u/RobusEtCeleritas",
" wrote below: it's better to first understand ",
" or ",
" as a finite difference which ",
", in principle, be used to write a Riemann sum whose limit is the desired integral.",
"I think explaining ",
" as a vector field or a differential form or a totally asymmetric bilinear functional or whatever does two things: (1) confuses someone even further and (2) sort of misses the point of the use of forms in intro physics. Intro physics is emphatically not using these expressions as forms. A proper understanding of differential forms is hardly necessary in all of undergraduate physics (albeit very useful for understanding classical electrodynamics), even for most of graduate physics."
] |
[
"\"Upvote ",
"/u/functor7",
"'s responses, they're correct and very good\" may as well become one of the subreddit rules at this point."
] |
[
"energy question"
] |
[
false
] |
As one draws closer to a star should one expect that there would be more chance of energy becoming matter than returning back to energy due to the thermal energy coursing thru that particular position in space? Or is energy and the transition into whisps of matter than back into energy not contingent on any of that and happens through out all of space?
|
[
"I don't understand your question."
] |
[
"I too am having trouble understanding your question. You're asking will energy spontaneously transform into matter the close you get to a star?",
"I don't think it works that way... Energy is released from a star via nuclear fusion, wherein the extreme temperatures and pressures inside a star cause two or more atoms to fuse together to form a new atom. ",
"The mass of the two individual atoms ",
" nuclear fusion is actually greater than the combined mass of the new single atom ",
" fusion, hence we derive (using E=MC",
" that some of the mass from the two atoms has been released as energy.",
"To my knowledge energy doesn't/cannot recombine into matter within a star."
] |
[
"I was under the impression that in space energy will transform itself into matter than into something else. Something like a Fineman diagram but will that occur closer to a star than out in deep space?"
] |
[
"Does the power required to maintain the elevation of a flight varies with the height at which it is flying?"
] |
[
false
] | null |
[
"Yes. That is why commercial airliners fly at 30,000 ft or thereabouts. It is a tradeoff between the air density being too thin to provide enough lift or adequately oxygenate the engines at higher altitudes, or so thick that the drag on the airframe at lower altitudes severely reduces fuel efficiency."
] |
[
"At any given altitude the drag an aeroplane experiences varies with airspeed like a U-shaped curve. This is because one source of drag (parasitic drag) increases with speed while another source of drag (induced drag) decreases with speed.",
"This means the power required to overcome that drag and sustain level flight follows the same sort of U shaped curve, and this means there is an airspeed that gives the minimum power to sustain level flight. Increasing altitude makes both the power and the airspeed required at that minimum increase.",
"At low true airspeeds increasing altitude requires more power, but at high true airspeeds it requires ",
". Remember the two forms of drag. Parasitic drag is greater the more dense the air and this is what dominates at high speed, while induced drag is greater the less dense the air and this is what dominates at low speed.",
"Note that flight at minimum power will not give the best fuel economy, because for fuel economy we care about distance covered.",
"The result is that airliners usually obtain the best fuel economy when they fly at their service ceiling. How high an aeroplane can fly may be limited by the power the engines can produce decreasing with altitude, or/and by the minimum speed for flight getting too close to the maximum speed. Getting too close to Mach 1 in an aircraft not designed for it makes Bad Things happen. And everything I've said here is about subsonic flight.",
"https://en.wikipedia.org/wiki/Parasitic_drag",
"http://www.nar-associates.com/technical-flying/altitude/part1/altitude_part1_wide_screen.pdf"
] |
[
"EDIT: Your question, as stated, is a little unclear. Are you talking about airplanes, hot air balloons, birds, or helicopters?",
"Also, are you just asking about maintaining flight (not falling) or actually travelling at that altitude?",
"My original answer, which was assuming fuel burning airplanes and trying to actually travel somewhere:",
"If we are talking about modern planes that burn fuel you have two factors to contend with:",
"As you begin gaining altitude, efficiency from reduced drag is greater than inefficiency from lowered oxygen, so as you continue higher you will save more fuel. If you fly too high, at some point the efficiency gained from reducing drag become less than the inefficiency from lowered oxygen and you will expend more fuel to travel the same distance.",
"There are also efficient and inefficient methods of gaining altitude (flying straight up then flying level burns more fuel than slowly gaining altitude... assuming of course, that gaining altitude isn't your only purpose (i.e. that you are trying to actual travel somewhere.))"
] |
[
"What determines which X chromosome becomes active during the X inactivation process?"
] |
[
false
] |
Shortly after the conception of a female mammal, one of the X chromosomes is inactivated. I'm curious as to what determines which of the two X chromosomes becomes the active one in a given cell? edit: clarifying question.
|
[
"It’s typically random, hence genetic mosaicism in most female mammals. You can see this more easily in calico or torture cats, because those genes are X linked, while genes that aren’t so phenotypically obvious aren’t the best examples, in a visual sense. They also tend to inactivate in patches."
] |
[
"The selection of the X chromosome that becomes an inactive \"Barr Body\" is random, based on the expression of the regulatory RNA Xist. Expression of Xist leads to compaction and inactivation of the chromosome via epigenetic marks on histones (including H3 K27 methylation, a canonical DNA silencing mark) and direct methylation of CpG dinucleotides. The selection of the inactive X is random, as others have pointed out. Interestingly, this is why all calico cats are female. The genes for fur color are located on the X-chromosome. So, the random, differential expression of one X chromosome over the other leads to the calico phenotype. Males, on the other hand, have only one, always active X chromosome, leading to fur color homogeneity. Some details of the regulation of X chromosome inactivation still remain mysterious, however. For a nice review, check out the review Chow and Heard in Curr. Opin. Cell Biol. from 2009 (",
"https://doi.org/10.1016/j.ceb.2009.04.012",
"). "
] |
[
"Correct me if I'm wrong, but I believe it's not shortly after conception because it occurs randomly in the somatic cells, not germ cells"
] |
[
"Is there a continuous version of product, like integrals for sums?"
] |
[
false
] | null |
[
"The Wikipedia article on ",
"product integrals",
" is a pretty good overview of the two most common definitions. They can both be shown to be expressible in terms of the usual Riemann/Lebesgue integral anyway."
] |
[
"Not really, we're more of mimicing the ",
" of the integral, rather than the interpretation. We get ordinary integrals from the intuition that we can add up a bunch of infinitely thin rectangles to get the area under a curve. The true definition of an integral is then some limit formula, and it happens to line up with our intuition in this case. But it's important to note that an integral is ",
" the area under a curve, it is a specific formula that agrees with the intuitive notion of \"area under a curve\". For these product integrals, we are basically saying that it's the ",
" of the integral that is important, not the ",
". How far can we get if we switch all sums to products and all products to exponents? Turns out, pretty far, there's even a version of the Fundamental Theorem of Calculus. So to get Calculus to work, we don't need to think in terms of area or even have that intuition, the only important thing is how the formula works."
] |
[
"Not really, we're more of mimicing the ",
" of the integral, rather than the interpretation. We get ordinary integrals from the intuition that we can add up a bunch of infinitely thin rectangles to get the area under a curve. The true definition of an integral is then some limit formula, and it happens to line up with our intuition in this case. But it's important to note that an integral is ",
" the area under a curve, it is a specific formula that agrees with the intuitive notion of \"area under a curve\". For these product integrals, we are basically saying that it's the ",
" of the integral that is important, not the ",
". How far can we get if we switch all sums to products and all products to exponents? Turns out, pretty far, there's even a version of the Fundamental Theorem of Calculus. So to get Calculus to work, we don't need to think in terms of area or even have that intuition, the only important thing is how the formula works."
] |
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