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[
"During meiosis do chromasomes cross over only at specific points? For example is it possible to cut a gene in half during the crossing over?"
] |
[
false
] |
Eg. If 2 chromosomes crossed over and the gene for haemoglobin was split between the maternal and the paternal chromosome. Would this actually be possible or are there systems which prevent genes from being broken due to crossing over? I mean how likely is it that the gene will cross over right between the start and stop codons in the DNA so that no gene is actually cut? Or does the large amount of junk DNA make cutting an important gene unlikely?
|
[
"Crossovers definitely do occur within genes. As long as there is not a single nucleotide lost or added when this happens, then nothing is wrong. If such a thing occurs it is called an ",
" and is either an insertion or deletion of nucleotides within the gene. If this happens with one or two nucleotides it can have serious consequences, because the gene is ",
"frameshifted",
", and the gene would either produce a defective product, or more commonly, no product.",
"Frameshifts will often create new stop codons and thus generate nonsense mutations. Perhaps that is just as well as the protein would probably be too garbled anyway to be useful to the cell. An indel of 3 nucleotides is generally more stable as the reading frame is preserved, but there can be some problems, Huntington's disease is caused by a 3-nucleotide indel.",
"These problems are rare, and if there are no indels, then crossover in the middle of the gene has no deleterious function, as it will pair up with the appropriate part of the non-sister chromatid."
] |
[
"Incidentally, events called translocations can occur where part of one chromosome accidentally crosses over with its non-partner chromosome. In those cases, it's possible to fuse two genes, and a new \"fusion protein\" can be generated. (This is pretty rare, since translocations do not occur very often, and most random translocations would not result in two coding regions of DNA being fused together in a way that would produce a protein.)",
"For example, the cancer CML (chronic myelogenous leukemia) is almost always caused by a translocation between chromosomes 9 and 22, creating a fusion between a gene called BCR and a gene called ABL. The ABL protein is usually regulated by other proteins, but those proteins can't regulate the BCR-ABL fusion protein, so cells with the BCR-ABL translocation can divide in an unregulated way and become cancerous. (More info ",
"here",
".)",
"So a translocation event like this can definitely damage a gene, but crossovers between different chromosomes don't happen normally."
] |
[
"Most mutations occur in S phase."
] |
[
"Why are the eyes of burn victims often left intact?"
] |
[
false
] |
[deleted]
|
[
"Eyes are covered and filled with fluid which is mostly water. Water has to absorb a lot of heat to increase in temperature as compared to most other materials. Because water can carry a large amount of heat, we use it in heating system and cooling system (like radiators).",
"Skin, muscles, and connective tissue have much less water thus as they are exposed to high temperatures they themselves increase in temperature much faster than the water logged eyes."
] |
[
"And don't forget about the blinking reflect. Eyelids provide more protection than I think people give them credit for."
] |
[
"I'm not sure they'd be terribly effective against large burns."
] |
[
"How were the elements formed after the big bang?"
] |
[
false
] | null |
[
"Hydrogen would be formed by electrons and protons forming pairs(via the electromagnetic force). Wikipedia seems to suggest there was enough energy for helium to be produced as well. ",
"http://en.wikipedia.org/wiki/Big_Bang_nucleosynthesis",
"The rest of the elements would be produced by fusion in the core of massive stars, or in supernova explosions. ",
"Helium carbon oxygen neon silicon and iron are produced directly from fusion.(may be more or less not exactly sure). ",
"The rest of the heavier elements are produced from the enormous energy output of supernovas. "
] |
[
"Well it's easier to start the story from the Big Bang.",
"So after the universe cooled down enough protons and neutrons started coming together and you end up with a universe of 75% hydrogen and 25% helium and a minute amount of lithium. So all first generation stars started from this matter.",
"A star uses fusion to obtain energy. The first stage in brief is to take to hydrogens and make a helium. So a star from birth converts all it's hydrogen to helium. When it's done it then starts fusing the heliums together and this sequence follows on until the star is made of iron, atomic number 26. So all the elements up to iron are made in stars.",
"Some stars with a large enough mass when they reach this stage will explode in a supernova. This extreme pressure and heat has the ability to cause even more fusion reactions and we get the elements all the way up to uranium being formed.",
"Any other place on the periodic table after uranium comes from humans smashing atoms together at high speeds. "
] |
[
"As for non main sequence, there are a few more explosive events other than supernovae that are thought to produce the heavier elements. Classical Novae and X-ray bursts are the most prominent."
] |
[
"I think I have some really profound ignorance about how gravity works, please help."
] |
[
false
] |
Suppose a person is living in an orbital space station and has a long enough rope, the other end of the rope is on Earth. Could he just about as easily (excluding fatigue for now, the lenght of the operation) pull up say 5kg payload in a bucket from Earth onto the space station as doing the same on Earth from a well? Could even a person from Earth fairly easily climb up that rope (excluding fatigue again)? If yes why is it so incredibly expensive and hard to get payload and people into orbit via rockets? What is this "escape velocity" thing and why does it apply only to rockets and suchlike, when a bucket on a rope doesn't need to leave with escape velocity, the space station guy can pull it up as slowly as he wants to. Similarly, if you have a rope tied to an object and throw it into a black hole, beyond the event horizon, why cannot you pull it out? I know my questions seem very stupid, there seems to be a very fundamental concept I am missing.
|
[
"1a. In order to put a thing in orbit, it has to be moving ",
" parallel to the surface of the Earth. Seventeen thousand miles an hour fast, for low-Earth orbit. The energy required to ",
" something from rest to that relative speed ",
" the energy required to lift that thing straight up into the sky."
] |
[
"1a) I believe if you do it right, the energy for parallel acceleration is taken from the rotating Earth itself."
] |
[
"Not nearly. If we fix our coordinate frame at the Earth's centre of rotation, such that a fixed point on the Earth's surface is moving around it in a circle, that point is moving only about a thousand miles an hour. You need ",
" to be in low Earth orbit.",
"It's true that it requires less energy to get to orbital velocity if you accelerate west-to-east instead of east-to-west, but the difference is only around six percent, something like that."
] |
[
"Distance, time and light (simple)"
] |
[
false
] |
[deleted]
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[
"While moving the period should change a little as light have to travel a little farther when it starts again."
] |
[
"While moving the period should change a little as light have to travel a little farther when it starts again."
] |
[
"Well, that's not true. Light still travels the speed of light. If you move backwards, the blinking will be offset in time by d/c, where d is distance, c is speed of light.",
"The laser is sending out somewhere close to n photons/second, like a BB gun constantly shooting BBs. As you moved backwards, the wall would see a temporary decrease in BBs, or in this case, photons/second (which is the definition of luminosity). If you moved forwards, a temporary increase would be seen.",
"If you were to place a sensor on the wall that could show when the blinking laser was on or off, you would see a square wave with an exact period. If you moved back, you would see the period temporarily decrease for the time you were moving. Move forward, temporarily increase.",
"Extremely slight to human perception, but that's molasses.. This is the basis of LIDAR based speed sensors and other light based range finders."
] |
[
"Do we have any idea if ancient peoples had the sames types and rates of cancer that we experience now?"
] |
[
false
] | null |
[
"An old hypothesis, and partly true. Absolute lifespan for many pre-industrial lifespan was in many cases not significantly shorter than now, but average lifespan was much shorter due to infant mortality. There have been 80 and 100 year old folks for many centuries. There is also some evidence now that cancers have increased, for people matched by age, and the effect varies with consumption of sugar. "
] |
[
"An old hypothesis, and partly true. Absolute lifespan for many pre-industrial lifespan was in many cases not significantly shorter than now, but average lifespan was much shorter due to infant mortality. There have been 80 and 100 year old folks for many centuries. There is also some evidence now that cancers have increased, for people matched by age, and the effect varies with consumption of sugar. "
] |
[
"Source for sugar related studies?"
] |
[
"When a black hole is said to be spinning, does that refer to the accretion disk or can we actually make observations about the behavior of matter below the event horizon?"
] |
[
false
] | null |
[
"The \"spin\" of the black hole isn't about the accretion disk, no, nor really is it about the behavior of matter inside. It's a property of the black hole, but remember the matter inside isn't sitting around doing something - it can't be supported against gravitational collapse by any force in the universe (so speaketh General Relativity). There's no ball of matter inside that's spinning. ",
"It might be easier to think of it as the black hole's \"spin parameter\" instead of how much it is spinning. (This is a case of simple language creating misconceptions.) When the black hole forms, the stuff it's made of has angular momentum - it's spinning around an axis. Angular momentum is conserved, and it doesn't vanish when the black hole is made. The black hole retains it in the form of this spin parameter, and it has an effect on the space-time around it ",
" of the event horizon which can be measured, just like the gravitational effects of the black hole's mass. So would the charge of the black hole, if any black hole with a net charge existed. These three parameters (mass, spin, charge) ",
" describe the black hole according to the no-hair theorem, which is pretty incredible - there's this thing that used to be a really complex system of all kinds of gasses with molecules going all kinds of ways, each with different properties, and now it's just this compressed thing that can be ",
" described with just 3 numbers!",
"The same idea of \"spin\" not really meaning something physical spinning also applies to electrons. They have \"spin\", and angular momentum, but they are not physically little balls of matter that spin around. It's an analogy to something familiar with similar properties."
] |
[
"A black hole is the entire structure of the thing, including (hypothetical) singularity, event horizon, etc. The singularity, which if it exists (it does according to GR) is always within the event horizon, and yes it's described as a region of infinite density and zero volume. It's this \"structure\" that would be a ring in the Kerr metric, but as the previous poster points out... it doesn't matter because it's causally disjoint from the rest of the universe. ",
"Everything that we need to understand of the black hole, and its impact such as frame-dragging, is the event horizon. The only way to expand our experience beyond that is to fall past the event horizon, and that's a one-way trip. ",
"Edit: Actually a complete theory of quantum gravity would presumably give us insight into the behavior of the region within the event horizon as well."
] |
[
"Mathematically, isn't a black hole represented as a single, indefenetely small point? And a spinning black hole as a indefenetely thin ring?"
] |
[
"Shouldn't black holes exert the same gravitational force as an object of similar mass but lower density?"
] |
[
false
] | null |
[
"would be the same, wouldn't the gravitational force exerted by both the earth and the black hole on a far away object be the same?",
", and at the same distance, yes."
] |
[
"For the region with r < R, where R is the radius of the Earth, the fields are different. There's no event horizon or singularity inside the Earth, the field just goes to zero at r = 0."
] |
[
"For the region with r < R, where R is the radius of the Earth, the fields are different. There's no event horizon or singularity inside the Earth, the field just goes to zero at r = 0."
] |
[
"How do anti-depressants work? specifically in regards to treating social anxiety?"
] |
[
false
] | null |
[
"That's not accurate. If SSRIs blocked 5-HTRs, what receptors would serotonin activate?",
"SSRI stands for selective serotonin-reuptake inhibitor. They block the serotonin ",
" from recycling free-floating serotonin, thus extending their time spent in the synapse."
] |
[
"Selective serotonin reuptake inhibitors (SSRIs) are the most commonly prescribed antidepressants for social anxiety disorder (SAD). As another person commented, SSRIs work by preventing a process called ",
". When neurotransmitters, like serotonin, are released by a neuron, they move into the synapse, a small space between neighboring neurons. The next neuron (referred to as the ",
" neuron) will bind the serotonin molecules released by the first neuron (the ",
" neuron), but neurons can only bind so many neurotransmitters. Excess serotonin that does not bind to the post-synaptic neuron gets cleared from the synapse by ",
" on the pre-synaptic neuron so that it can get reused. SSRIs block the activity of these transporters, allowing more serotonin to remain in the synapse to eventually bind to the post-synaptic neuron.",
" these drugs work for treatment of SAD (and a bunch of other anxiety and mood disorders) is still somewhat unclear. They are better than placebo when it comes to reducing symptoms, so they're effective, but whether the drugs' mechanism of action is directly related to the pathophysiology of anxiety and/or depression is still unknown. The fact that SSRIs usually take over a month to exhibit their full effects suggests that the actual treatment mechanism is not serotonin regulation itself but instead is something \"downstream\"-- some sort of change that is ",
" by increased serotonin availability, but may or may not involve serotonin itself thereafter."
] |
[
"It depends on the type of anti depressant. SSRI’s (selective serotonin reuptake inhibitors) help regulate your Serotonin levels and increase them by binding to the same receptors that receive serotonin. This blocks the actual serotonin from binding to the receptors which leads to increase free floating serotonin."
] |
[
"How do we know how many isotopes exist in the universe for an element, and their percentages, to determine the atomic mass? As we discover new isotopes, does a printed periodic table become obsolete because that element will have a new atomic mass?"
] |
[
false
] |
[deleted]
|
[
"There are 22 mononuclidic elements. The abundances of those don't change. Those are important for calibrating detectors and such.",
"For the rest, standard atomic weights are revised biennially by the IUPAC's ",
"Commission on Isotopic Abundances and Atomic Weights",
" (CIAAW). Should you ever have trouble sleeping, volunteer to join an IUPAC committee.",
"As recently as 2009 the decision was made that some elements cannot be described by only one relative atomic weight. For instance, hydrogen is now written as a relative atomic mass with a range of [1.00784, 1.00811]. That's called the \"we give up please stop sending weird samples\" rule.",
"So yes, many printed periodic tables are obsolete and the <100 people in the world who need that information are bothered.",
"Physically, the ",
"atomic masses and ratios are measured using a mass spectrometer",
". That's the easy bit. The hard bit is collecting representative samples.",
"The rules for sample collection are complex, strict and boring. They must be collected from somewhere on Earth. There are some other criteria about how samples should be representative, natural, non-radioactive etc.",
"As an example, Boron collected in the USA has a different isotopic ratio to Boron collected in Europe. Which one is more \"real\"? The answer is... more work is required."
] |
[
"The percentages used aren't the percentages \"in the universe\", they're the percentages on Earth. And we know them because they can be measured.",
"If you take a bunch of natural chlorine, you can do mass spectrometry, for example, to determine the ratios of each isotope in the sample.",
"The numbers don't need to change anymore when we discover new isotopes, because any nuclide which hasn't been discovered yet most likely has a half-life far too short to be found naturally on Earth."
] |
[
"I'm not a pedantic asshole",
"Well, you are, but that's okay. That's why we all come to reddit.",
"I'm guessing that there are probably less than 100 people in whatever country you in who even know about the CIAAW. Worth mentioning to your lecturers.",
"For more fun history, the CIAAW was created in 1899 to set atomic weights. The last major review was 2003 and the next is expected around 2028.",
"Only once since 1951 has a relative atomic weight changed and that was 2007. Zinc changed to 65.38 ± 0.02 from 65.409 ± 0.004. And nobody noticed or cared."
] |
[
"What exactly is itching?"
] |
[
false
] |
From a medical perspective what is the function of itching and what exactly is it? I mean in a way id as a layman say that it is the opposite of pain. Both have a function to let you know where to focus your attention on, on your body. Pain in a way asks you to stop doing what you'r doing and itch is asking you to do what you're not doing. But what exactly is itching and what in your body causes it? Sure it is a reaction to something but do we have specific "itch" sensors or how does this work?
|
[
"Itchiness is not a single phenomenon. There appear to be several different pathways that can cause itching. The best known one is the histamine response that antihistamines (benadryl, claritin, etc.) are good at blunting.",
"There seem to be other itch receptor pathways, though, and I'm not sure if anyone knows for sure how important they are, or what is supposed to trigger them in nature. ",
"http://www.ncbi.nlm.nih.gov/pubmed/20004959"
] |
[
"Itchiness is not a single phenomenon. There appear to be several different pathways that can cause itching.",
"Here are some nice tables from a review on itchiness that show the pathways/mediators (",
"Table 1",
" and ",
"Table 2",
"). ",
"Also, while I'm making a comment, I thought I'd add that pain (e.g., scratching) inhibits/relieves itch. Conversely, analgesics (opioid receptor agonists) reduce pain and enhance itchiness."
] |
[
"I asked a ",
"very similar question",
" almost two years to the day, ago. ",
"This other thread",
" the discussions in this thread, answered a lot of my questions and led me to \n",
".\nSorry, pointed you to wrong interesting article, ",
"here is the correct one",
"\n I hope it helps you. "
] |
[
"Why would melting ice caps raise sea levels?"
] |
[
false
] |
I always imagine an analogy with a glass of ice water filled to the brim. When the ice melts, the water doesn't spill over the edge. So why would melting ice caps raise sea levels? I feel like I'm leaving something out here, but I can't figure out what. Thanks
|
[
"The biggest icecaps are on top of land (Greenland and Antarctica)"
] |
[
"Likewise, as large ice shelves break off of the Antarctic coast, glaciers that were being held back by them will begin to flow more quickly."
] |
[
"Likewise, as large ice shelves break off of the Antarctic coast, glaciers that were being held back by them will begin to flow more quickly."
] |
[
"What are the chances the Voyager 1 Probe ends up in a black hole?"
] |
[
false
] | null |
[
"It's so unlikely that you have to get into weird distant future time before the chance even starts to get reasonable.",
"If you're floating through interstellar space, any time you approach a star or black hole, you are going faster than its escape velocity. Escape velocity tells you the amount of kinetic energy you need to coast infinitely far away from a point around a star or black hole - this is the kinetic energy you need to \"use up\" by fighting gravity to escape the object. This is the same as amount of kinetic energy you ",
" by falling in from far away. So if you fall in from a distance, you are always faster than escape velocity, and you won't get caught by the gravity of the object. The only way to get captured is to (a) hit the object straight on, or (b) have a complex interaction with orbiting planets that changes Voyager's speed dramatically (i.e. like a slingshot in reverse).",
"But Voyager is going much slower than the escape velocity from the ",
". So it will continue basically drifting around in orbit around the Milky Way for a long time. So, what are the chances that it will directly hit an object in its orbit?",
"In our orbit, there is about 1 star per cubic parsec. Most stars are smaller than the Sun, but if we pretend they are the same mass as the Sun, that'll give us an upper limit. Voyager and the stars around it are drifting at 10s of km with respect to each other. If we put that maths altogether, you expect about one collision with a star every ",
". The odds are slightly higher if we include scattering off planets etc, but that gets hard to calculate, and it'll still be extremely unlikely. To hit a black hole is much much rarer than that, because black holes are much smaller in radius, and much less common.",
"On this crazy time scale, ",
"things get weird",
". Basically, if there has been enough time for there to be a reasonable chance that Voyager has had a close encounter with a star, there has also been enough time that every star has had a close encounter with another star. These close encounters will scatter the stars around, and many will be ejected from the galaxy or will fall inwards. There is a reasonable chance that Voyager will be ejected from the galaxy too, and will just float through intergalactic space forever. Alternatively, it ",
" get scattered inwards, and eventually through many scattering events end up falling into the supermassive black hole at the centre of the galaxy.",
"And those are basically the two final options, if Voyager survives that long. Most likely it gets ejected from the Milky Way by some chance encounters, but it possibly might end up in the supermassive black hole at the centre of the Milky Way instead. This is so far in the future though that it gets crazy to try to predict."
] |
[
"Wow, thanks for sending me down a Wikipedia rabbit hole!"
] |
[
"Space is so vast that even when the Andromeda Galaxy collides with ours, the chance of two stars actually colliding is extremely low, despite there being billions of stars in each Galaxy."
] |
[
"Do humans ever actually die purely of old age or is there always some underlying disease that may have been caused by old age?"
] |
[
false
] | null |
[
"This is an interesting question. Believe it or not until recently people were not interested in the cause of death in the extremely old. Focus was (and is) on causes of death in the younger people. Consequently it was extremely rare for a person who \"died of old age\" as it were to have an autopsy performed.",
"This study",
" from 2005 was one of the first to examine the cause of death in the elderly who \"died of natural causes\" The findings were : \"acute organic failure causing death\nwas found in 100%, including cardiovascular diseases in 68%, respiratory illnesses in 25%, gastrointestinal disorders in\n5%, and cerebrovascular disease in 2%.\"",
". Our goal was to assess the prevalence of common causes of death and the demographic variables in\na selected population of centenarians.",
". The autopsy reports and medical histories of all individuals 100 years, dying unexpectedly out of hospital,\nwere gathered from 42,398 consecutive autopsies, performed over a period of 18 years at the Institute of Forensic\nMedicine, Vienna. These records were evaluated with regard to age and sex, circumstances of death, season, time and the\ncause of death, as well as the presence of any other comorbidity.",
". Forty centenarians (11 men, 29 women) were identified with a median age of 102 6 2.0 (range: 100–108)\nyears. Sixty percent were described as having been healthy before death. However, an acute organic failure causing death\nwas found in 100%, including cardiovascular diseases in 68%, respiratory illnesses in 25%, gastrointestinal disorders in\n5%, and cerebrovascular disease in 2%. Additionally, centenarians suffered from several comorbidities (cardiac\nantecedents, neurologic disorders, liver diseases, cholecystolithiasis), which were not judged to be the cause of death.",
". Centenarians, though perceived to have been healthy just prior to death, succumbed to diseases in 100%\nof the cases examined. They did not die merely ‘‘of old age.’’ The 100% post mortem diagnosis of death as a result of\nacute organic failure justifies autopsy as a legal requirement for this clinically difficult age group."
] |
[
"Also, as an aside, cells undergo mitosis until they become pre-cancerous or their telomeres are too degraded and then they senesce i.e. stop dividing. In one case, an extremely old woman had her immune cells (B-cells I believe, but I may be wrong) sequenced and it was found that all her immune cells came from two stem cells. This leads to impaired ability to fight infection and the individual becomes more susceptible to opportunistic pathogens. Also, also, damage accumulates as you age, ranging from increased mutations in somatic cells to reduced anti-oxidant production in the liver. Sometimes, a tipping point is reached and you fall victim to organ failure. "
] |
[
"some of that is addressed in the main body of the article:",
"Sixty percent (n ¼ 24) of the deceased were described by\ntheir family or their family physician as having been healthy\nat the time of death. However, 58% had cardiac antecedents\nsuch as chronic heart failure, stable angina pectoris, a history\nof myocardial infarction, or an implanted pacemaker. In\nthe remaining individuals, preexisting conditions included\nhypertension (23%), diabetes mellitus (10%), respiratory\ndiseases (10%), and gastrointestinal diseases (5%). Neurologic\ndisorders such as Alzheimer’s disease, Parkinsonism,\nor hemorrhagic stroke were present in 43% (Table 1).\nAdvanced neoplastic disease with widespread distant\nmetastases was found in three corpses. In only one person\nof this cohort, the malignancy had been diagnosed during\nthe lifetime",
"As well as the discussion of the findings:",
"Our major finding is the striking contrast between an\nautopsy-proven cause of death in 100% and the fact that\n60% of the centenarians were described as having been\nhealthy before death by their relatives and even by their\nphysicians. The Viennese results are consistent with Danish\nand Finnish data on living centenarians (16,17), presenting\nchronic cardiovascular diseases in 72%. In the Viennese\nstudy, 68% of nonhospitalized centenarians died due to\ncardiovascular diseases, which is in contrast to autopsy\nreports of hospitalized centenarians dying because of\ncardiovascular disorders in only 20%–31% (13,18). It is\ninteresting that pulmonary infections caused death in only\n10% in the Viennese study, being in contrast to Mac Gee’s\n(13) autopsy investigations of a hospitalized geriatric\npopulation, dying predominantly because of respiratory\nand urinary infections as well as malignancies. Malignancies\ndid not cause any death in the Viennese study population. In\nthese findings, approximately half of the individuals were\ndiagnosed with neurological disorders, and 10% with\ndiabetes mellitus; the percentage of both diseases again do\nnot differ from the Danish and Finnish data on living\ncentenarians (16,17). Very old people usually are assumed to be slender, gaunt,\nor even cachectic (18). However, 79% of the female and\n64% of the male corpses in the Viennese study had a normal\nor even elevated body weight, perhaps reflecting the\nindividuals’ general good health. Only patients dying due\nto pneumonia had a reduced body mass index (19).\nOur study population did not suffer from chronic\ndebilitating or bedridden states. This fact is stressed, for\nexample, by the autopsy-proven complete and stable\nconsolidation of any fractures. Women had a higher\nincidence of fractures, suggesting a higher incidence of\nosteoporosis (9).\nThe Viennese study confirms that reaching the age of 100\nyears is not exclusively reserved for individuals being free\nfrom any severe or chronic disease. The centenarians might\nhave been healthier than their birth cohort members who did\nnot reach the age of 100 years. They may have also\nbenefited from disease onset at a later age or from an\nadaptability enabling them to maintain sufficient biological\nfunctions regardless of the presence of several diseases and\natrophy of organs.\nThe distribution and the patterns of causes of death in\ncentenarians—with the exception of respiratory diseases—\nwere nearly similar to the cohort of unexpected out-ofhospital\ndeaths in patients aged 85 years that have been\ninvestigated at our institute (19) (Table 2). Nevertheless, the\nlongevity population seems to have the ability to live with\nchronic diseases significantly longer than their birth cohort.\nThis ability is associated with specific genetic predispositions\n(1). Therefore, genetic analyses of centenarians and\ntheir long-lived siblings and/or long-lived multigenerational\nfamilies would help to identify the genes that contribute to\nhuman longevity (20,21).\nUntil recently, advanced age has been considered to be\na disease itself (4). However, our study demonstrates that\ncentenarians die as a consequence of organ failures and\nnot because of ‘‘old age’’ as commonly assumed. With\nsome difficulty, physicians have learned to avoid the facile\nexplanation of obscure conditions in very old individuals as\nbeing the result of ‘‘old age.’’ Atypical and/or asymptomatic\npresentations in centenarians are often mistakenly interpreted\nas an unspecific cause of death (22).\nIn summary, the majority of centenarians suffered from\nchronic comorbidities even though they were considered\nto be healthy. Thus even centenarians should receive an\nautopsy; their deaths should not be merely attributed to old\nage or senile debility. The 100% post-mortem diagnosis of\nacute organic failure causing death justify autopsy as a legal\nrequirement for this clinically difficult age group."
] |
[
"What happens to the donors genetic code after a blood transfusion?"
] |
[
false
] |
So I donated blood the other day and it got me thinking. what happens to my DNA after the blood is used? Does that person now carry a little bit of identifiable ME for a little while? And if so for how long?
|
[
"Erythrocytes don't have DNA! They need all the space they can get for hemoglobin, so right before it is fully mature it packages up its nucleus (where the majority of the DNA is), and ejects it. This package also contains the organelles, including the mitochondria which also have their own DNA. ",
"The good thing about not having DNA or organelles is that erythrocytes don't use any oxygen, they create their ATP via glycolysis of glucose which then leads to fermentation of lactic acid. This means more oxygen for the tissues in your body.",
"Now, there will be some white blood cells in a transfusion, but very few as blood transfusions are almost never whole blood transfusions anymore. When processing donated blood, different parts of your blood are separated out. A 'blood transfusion' is pretty much almost all red blood cells. Red blood cells are filtered to reduce the amount of white blood cells to an insignificant amount. They won't live long enough to have much of an impact on the recipient in nearly all cases."
] |
[
"Very cool. Thanks for the response!"
] |
[
"One kind of interesting note on this is the matter of antigens. The body can still recognize it's own cells (or at least it's own type) by the antigen receptors on the cell's membrane. This may sound complicated, but you've probably heard it dozens of times as type A, B, AB, and O blood types. The antigen receptors act as ID tags on the erythrocytes (though antigens are used throughout the body) and identify the cell so the leukocytes (white blood cells) don't attack them. This is why blood transfusions have to be by type, rather than blind. A needs A type, B needs B, AB can use any kind, and O can be used for any as it doesn't have any antigen receptors (if I recall correctly.)"
] |
[
"This graph appears to show a decline in measles cases prior to the introduction of the measles vaccine. Why is that?"
] |
[
false
] | null |
[
"The graph doesn't really show a reduction, rather a 'boom and bust' cycle with a reduction in amplitude in the last couple of phases.",
"This is neatly explained by the other comments to a greater or lesser degree.",
"But when reading graphs of this sort you must read all that is shown and understand the limitations (what is not shown)",
"To get you started, first notice that the measure is number of cases Reported, not the true number. There are clues there to possible distortion. "
] |
[
"Because the immune system of adults is 'too powerful'; it ",
" to pathogens such as measles, and the immune reaction can cause a whole scala of interesting symptoms that are potentially more damaging than the pathogen itself."
] |
[
"Immunologist here! These different terms can be super confusing in the best of cases! Just to clarify in this instance:"
] |
[
"How did the dinosaurs gain traits to go from cold-blooded to warm-blooded when tgey evolved into the ancestors of modern birds? Or did the ancestors of modern birds turn warm-blooded after feathers covered the entire body?"
] |
[
false
] | null |
[
"Warm bloodedness is largely a function of metabolism. It has to do with a variety of physiological and chemical processes in the body.",
"It's also kind of a spectrum. larger birds are better at maintaining body temp than smaller birds. Small mammals like bats and some hibernating rodents go into torpor because their core temperatures are not constant and become very low during hibernation season.",
"Feathers and body thermoregulation may have evolved together or traits for thermoregulation may predate feathers by a lot . There's some research that suggests that some dinosaurs may have been more warm blooded than cold blooded, and this includes dinosaurs that are not thought to have been covered in feathers "
] |
[
"Bluefin tuna generate enormous amounts of heat when pursuing prey, and have ",
"complicated heat exchange systems",
" to keep this heat from being lost through their gills. They're sort of warm blooded on demand. Sharks don't do any of that, but the large ones have enough metabolic activity to be consistently a few degrees warmer than their surroundings. Partially warm blooded animals are called mesotherms. ",
"I'm talking about fish because they're not extinct (not yet, please save the tuna) and we can actually take their temperature. With extinct animals you can sometimes make a really good guess based on how their bones grew and suspected thermoregulation structures like the dimetredon's sail (but it's not really even a dinosaur). Current thinking is that dinosaurs were probably fully warm blooded like modern birds, and warm-bloodedness evolved multiple times."
] |
[
"Just FYI there is much debate whether dinsoaurs were warm or cold blooded, or something in between. ",
"See here",
" for example. Some dinosaurs, such as the ancestors of birds were probably warm-blooded. Those that were fully feathered were almost certainly warm-blooded"
] |
[
"Why is angular momentum so important in studying the atom? Are atoms subject to gyroscopic precession?"
] |
[
false
] |
I'm starting a quantum mechanics course at university. I want to know why angular momentum is so important ? Many Thanks
|
[
"Because angular momentum is a conserved quantity, meaning the total angular momentum operator commutes with the Hamiltonian of the system. So it's a quantum number which can be used to label your energy eigenstates.",
"And that's ultimately what you're trying to do when studying bound quantum systems: find and characterize their energy eigenvalues and eigenstates.",
"Angular momenta are also important for transitions. Angular momentum and parity selection rules prevent certain transitions from happening.",
"And yes, anything with a magnetic dipole moment can precess in an external magnetic field."
] |
[
"To add to this in a slightly more ELI5 style: quantum mechanics leads to the discretization of the orbital angular momentum of electrons that are bound to atomic nuclei. This, in turn, leads to the different orbitals that electrons can occupy. This, in turn, leads to the ways in which atoms form different bonds with each other and interact. This, in turn, leads to basically all of chemistry and hence most of life and every day materials. So in that sense, chemistry exists and can be understood largely due to being able to understand quantum mechanical orbital angular momentum of electrons bound to atoms."
] |
[
"The electrons rotate around the nucleus, so clearly they have angular moment. ",
"The reason why it is important is because the electric force between the proton and electron is spherically symmetric, meaning that the proton cannot change the angular momentum of an electron through electric force.",
"Recall how useful this spherical symmetry and conservation of angular momentum was when solving Kepler's two-body problem. It will turn out to be equally as useful when solving the hydrogen atom (again a two-body problem), as well as numerous other examples. ",
"Also, to answer your other question: Yes, atoms can be subject to something like gyroscopic precession, though gravity is too weak for them. See Larmor precession: ",
"https://en.wikipedia.org/wiki/Larmor_precession",
" "
] |
[
"Why do whales beach themselves?"
] |
[
false
] |
[deleted]
|
[
"Here's an article that discusses it: ",
"http://www.scientificamerican.com/article.cfm?id=why-do-whales-beach-themselves",
"TL;DR - In most cases it is due to injury or illness - in some cases they just don't know",
"EDIT: this Wikipedia article also discusses some of the thought to be causes: ",
"http://en.wikipedia.org/wiki/Beached_whale"
] |
[
"Military sonar has been implicated in some cases but whales were beaching themselves long before sonar was invented: ",
"photo of whale stranding, 1902",
"16th century dutch engravings",
"beached whales, 1577"
] |
[
"Military sonar has been blamed pretty successfully.",
" ",
"However, courts ruled that national security trumps everything. "
] |
[
"If the Oxford vaccine targets Covid-19's protein spike and the Moderna vaccine targets its RNA, theoretically could we get more protection by getting both vaccines?"
] |
[
false
] |
If they target different aspects of the virus, does that mean that getting a one shot after the other wouldn't be redundant?
|
[
"They both target spike. Moderna works differently. Moderna uses mRNA as the delivery mechanism of the vaccine. Our body then turns that mRNA into a protein that the immune system recognizes and creates antibodies to. ",
"So essentially the end product our immune system sees is similar, it’s just how the vaccine creates that product that’s different."
] |
[
"We don’t ",
" ",
". It is probably not a good idea. ",
", The second dose of ",
" the ",
" COVID vaccine had more severe reactions than the first dose. ",
"However, and most importantly, we don’t have data on ",
" ",
", so no one can tell you it has been proven safe. It might not kill you, but for instance, one of the patients treated with the second dose of the high dose of the Moderna vaccine ran a fever of 103. You probably don’t want something like that to happen.",
"If you start a 2 shot regimen",
", you should get both of the same. You should probably not get another vaccine unless you test negative for antibodies later. (Doctors can do this for other vaccines too—they wear off then they give you a booster)",
" changes marked with strikeouts and italics for clarity and validity"
] |
[
"Is there likely to be a danger of taking more than one? Lets say you grab whatever comes first, then a few months later it turns out the next one offers better protection."
] |
[
"Are mosquitos good for anything at all?"
] |
[
false
] |
I was always told that everything in the animal world had a purpose. Are mosquitos just good for nothing? If they are useless, why haven’t we killed them off by now to prevent all the disease they give?
|
[
"Hi there! I work with mosquitoes right now for my research and I get this question a lot from curious folks. First, thinking that an animal needs to be \"good for something\" is not how we should view another living thing. Animals and plants evolved to suit their environment, they are very good at that though it may not be useful to us. Everything also has a role to play within their ecosystem and mosquitoes are no different. So here is my love letter to mosquitoes:",
"If you are asking do they benefit the ecosystem, then yes absolutely. Mosquitoes are an important source of food for many animals as both larvae and adults. Mosquito larvae are aquatic, they feed fish, dragonfly larvae, damsefly larvae, diving beetles, water scavenging beetles, turtles (red-eared sliders love mosqutio larvae!), and some frogs (if you're in the NE U.S. our leopard frogs love mosquito larvae) (",
"Quiroz-Martínez and Rodríguez-Castro, 2007",
"; ",
"DuRant and Hopkins, 2008",
"; ",
"Saha et al., 2012",
"; ",
"Bowatte et al., 2013",
"; ",
"Sarwar, 2015",
"; ",
"Bofill and Yee, 2019",
"). There is also a mosquito genus (",
") that does not bite humans but feeds on other mosquito larvae (",
"Trpis, 1973",
"). Adult mosquitoes feed birds (blue birds, purple martins, cardinals, etc.), bats, and spiders (",
"Kale, 1968",
"; ",
"Roitberg et al., 2003",
"; ",
"Medlock and Snow, 2008",
"; ",
"Reiskind and Wund, 2009",
").",
"Additionally, mosquitoes pollinate flowers (",
"Thien, 1969",
"; ",
"Thien and Utech, 1970",
"; ",
"Peach and Gries, 2016",
"). Most of a mosquito's diet is nectar. Only females drink blood and that is only when they need the extra protein to create eggs. Many mosquitoes are very important pollinators to smaller flowering plants that live in wetter environments. For example, the snow pool mosqutio (",
" in my home state of NJ is the primary pollinator for the blunt-leaf orchid (",
") (",
"Gorham, 1976",
"). The role moquitoes play all over the world as pollinators is actually grossly understudied by scientists. Most of the focus on their biology/ecology is as vectors but there is so much more going on in this taxon than disease.",
"If you are concerned about disease and protecting humans, I hear you on that, but out of the 3,500 or so species of mosquito out there we really only worry about mosquitoes of three genera; ",
", ",
", and ",
" as far as disease goes (",
"Gratz, 2004",
"; ",
"Hamer et al., 2008",
"; ",
"Hay et al., 2010",
"). That leaves I think 35+ or so other genera, some of which would never bite a human let alone transmit disease to us. Of the species that prefer mammals humans are not even really their first choice, they tend to prefer livestock over us. Many species don't bite mammals at all! For example, ",
" feeds almost exclusively on birds and ",
" feed on frogs (",
"Molai and Andreadis, 2005",
"; ",
"Priyanka et al., 2020",
").",
"So wiping out every mosquito species would be overkill. Could we remove the species that are harmful to humans and not have any issues within the ecosystems they are apart of? That is a difficult ethical question that has long been debated within the entomology/ecology community. You will find scientists on both sides of the fence. There was a study that came out a few years ago saying it would be fine, but that study is hotly debated. Personally, I'd say if it were possible to at least remove the invasive species that cause disease, such as ",
" in the U.S., then I am okay with that (",
"Moore and Mitchell, 1997",
"). They shouldn't be here anyway. But it could be very difficult to remove all invaders without also harming native mosquito populations. And, for some species that have been here in the U.S. for hundreds of years (",
") what would removing them from local populations do to the ecosystem? Perhaps it would allow for a bounceback of native species they have been outcompeteing, or perhaps they are so abundant and woven within the fabric of the ecosystem it would cause an issue. I honestly don't have an answer for this. Even if there is low to no impact ecologically by eradicating all mosquitoes, is it the ethical choice to make? Ask 10 scientists, get 15 answers.",
"Should we eradicate ",
" in their native homes of Japan, Korea, China, and a few islands? Personally, I would be against it. I'd rather use control methods and keep populations low where they intersect with humans. We are also making incredible strides with genetic engineering! Perhaps one day we could use gene editting to make these troublesome species poor vectors for the diseases we fear. If their bodies are no longer an effective home for the disease then we don't have to worry about them.",
"Edit - I completely forgot to mention this - but if we remove an entire species or several species that may not impact the ecosystem in a \"make it or break it way\", and then something happens to other species that have similar roles, we have no backups. It's not is this species a huge or sole food source it's this species along with other species are filling a role in the ecosystem and if we lose too many species within a particular role we could have a catastrophe on our hands. Another example, mosquito larvae eat plant detritus in ponds. They are not the only organism that does this, but if we remove all of them and there is a similar collapse in say frogs (as we know amphibians are currently in trouble) then we are out two detritivores within a system.",
"I'll leave you with this quote from Aldo Leopolds's ",
":",
"A thing is right when it tends to preserve the integrity, stability, and beauty of the biotic community. It is wrong when it tends otherwise."
] |
[
"Very well placed, and in layman’s terms. Thank you for the well thought out response. ",
"I did not know they drank nectar at all! You have shed a new light on them. I would still get the skeeves if one was crawling on me, but I respect them greater from a distance now.",
"If you have time to spare in your day, do you have any more cool facts of note about mosquitos?"
] |
[
"Thank you for reading my longwinded response! I very much understand getting the skeeves and I don't blame anyone for that response. I used to work in a lab where we had an ",
" colony. They frequently got loose and would bite me all day. I now have an allergy to this species' bites, I get huge welts. So I get how you feel!",
"Let's see, cool mosquito facts. I think I probably do!"
] |
[
"I keep reading about how Covid has had a worse effect on minorities in the US particularly blacks. Is this all because of environmental/societal reasons, or do people of African decent actually have a harder time with the virus physically?"
] |
[
false
] |
[deleted]
|
[
"There are a variety of factors involved.",
"In the case of kidney failure due to COVID-19, many people of African descent are more susceptible due to variants in the APOL1 gene. This isn't specific to COVID-19 though, the variants just make the kidneys weaker in general. Source: ",
"https://jasn.asnjournals.org/content/31/8/1688",
" and ",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4157456/",
"Interestingly, people with darker skin are more likely to be vitamin-D deficient, which may be another risk factor. (Plus, people of West African descent are usually lactose-intolerant, and an important source of dietary vitamin D is milk.)",
"Also minority communities have a higher rate of pre-existing conditions due to societal and environmental factors. This increases the risks for complications.",
"Finally, people of low socioeconomic status may be unable to effectively practice social distancing (imagine living in very crowded conditions to save on rent)."
] |
[
"https://www.mayoclinic.org/diseases-conditions/coronavirus/expert-answers/coronavirus-infection-by-race/faq-20488802",
"\"While there's no evidence that people of color have genetic or other biological factors that make them more likely to be affected by COVID-19, they are more likely to have underlying health conditions. Having certain conditions, such as type 2 diabetes, increases your risk of severe illness with COVID-19.\"",
"Other factors include a higher likelihood of working a public-facing or essential job - for example Black Americans represent ~11% of America's population but ~30% of its licensed practical and vocational nurses - and a higher prevalence of living in larger, multi-generational family homes."
] |
[
"Excellent answer, one addition is that air pollution leads to worse covid outcomes, and in the US, air pollution is correlated with low income areas (denser, more industrial pollution, etc)"
] |
[
"I there a maximum strength for a permanent magnet of a given mass?"
] |
[
false
] |
Pretty straight forward. If we held a 1 gram "blank" neodymium magnet to a junk yard electromagnet and another to a magnetar (magnetic neutron star), they should both become just as powerful, right? What limits the power they can achieve?
|
[
"The maximum \"strength\" of a permanent magnet is when the magnet is a single ",
"magnetic domain",
". You can think of a permanent magnet as a collection of many atom-sized magnets all pointing in generally the same direction. When they are all perfectly aligned, the magnetic field sufficiently far away from the magnet is proportional to the mass of the magnet for a given material."
] |
[
"Well for an absolute top bound, you could start with the elementary particle with highest spin-to-mass ratio (I guess a neutrino, whichever is bounded to be the lightest). Then you divide the 'given mass' of your magnet, for example one gram, by the neutrino mass. You'll get the number of neutrinos present, e.g. the number of spin 1/2's present. Then take the product of the number of spins and the magnetic moment of each spin and you'll get the maximum magnetic moment you could have."
] |
[
"Indeed. And the saturation magnetization of iron-based alloys is around 2 tesla. But that is in the lab where electrons are behaving normally; a magnetar is a different beast."
] |
[
"If an ant was the same size as a tiger, would still be able to lift 20 times its own weight?"
] |
[
false
] | null |
[
"No. The problem starts when you scale up the length and all other measurements in equal proportion, then your volume (i.e. mass) grows with the third power of that length, while the strength of your bones and muscles, which depend on their cross section, only grow as the square of that length. An ant the size of an elephant would collapse under its own weight.",
"You just have to look at the body shapes of very small animals, e.g. ants with their long thin legs sticking out sideways and their large abdomens supported by a very narrow waist, to very large ones like elephants, where the legs are very massive and under the body to be able to support its weight. "
] |
[
"Also Ants breath thorugh holes in their body and they would suffocate when they were as big as tigers."
] |
[
"Although millions of years ago there were much bigger bugs (not quite tiger sized, but huge for bugs) that were able to survive while breathing through sphericals, but the atmosphere had a much higher percentage of oxygen then."
] |
[
"[Medicine] What steps are taken to diagnosis a cell as cancerous ?"
] |
[
false
] |
I know preventive scanning is big deal due to the earlier one is diagnosed, usually the better the outcome (depends on stage, etc.), but when diagnosed with a possible cancerous tumor, what steps do you take to verify?
|
[
"Just to clarify further upon what's been said:",
"A pathologist will usually get the sample from a biopsy. They will prepare it onto a film and have a look at it under the microscope. Because cancers are rapid, uncontrolled growth of cells, they tend to look different to normal cells. Very basic things to look for are:",
"Pleomorphisms - normal cells will look similar to their neighbours. Cancerous cells have unregulated growth so they can look all funny and different to each other",
"Hyperchromatic nuclei - As we've said, cancerous cells are trying to replicate a lot. The process of replication requires making a copy of the DNA. The DNA is located in the nucleus. Thus the nucleus will look much darker because there's more DNA material there compared with normal cells.",
"Increased nucleus to cytoplasm ratio - this kinda goes along with the previous point. Because the cells are producing more DNA, the nucleus is bigger and will proportionally take up more room than the rest of the components in the cell compared with non cancerous cells.",
"Mitotic figures - as previously established, cancer = replicating heaps. Because of this, we're more likely to catch cells in the process of replication (ie mitosis). That's essentially what mitotic figures are.",
"There are also a few other ones which I can't remember off the top of my head.",
"Edit: formatting"
] |
[
"As mentioned by others, the diagnosis is typically based on visual inspection: either of biopsied cells under a microscope, or of a tumor or the progression of a tumor visualized by medical imaging technologies.",
"It's a situation where a trained observer would know it when they see it, but the question of how to objectively identify an individual cell as being cancerous is actually a fairly interesting one. For one thing, there's not really a good definition of what cancer is exactly; it is a term for a set of diseases which all involve disregulated cell proliferation and resistance to cell death. In different forms of cancer, the features of the diseased cells can be entirely different in terms of what causes their dysfunction and how exactly it is manifest.",
"However, there are characteristic biochemical abnormalities that could be used to identify many different types of cancer. You may have heard of cancer markers. These are molecules which are produced either by cancerous cells or by normal cells in response to cancer cells, and either their presence alone or their abnormal abundance can indicate certain types of cancer. There are also a number of genetic features which can definitively indicate cancer. In several tissue types, there are pairs of genes which, if both members of the pair are mutated in a way that impedes their function sufficiently, cancer is guaranteed. Additional indicators include certain structural features of the cells, certain metabolic properties (i.e. energy consumption rates & metabolic byproducts), properties of the local extra-cellular matrix, abnormal responses to certain cell signaling molecules, characteristic gene expression profiles, and surface markers (signaling molecules present or absent on the surface of cells)."
] |
[
"There are also biochemical markers of cancer that can be detected in the cell in a variety of ways. For example our lab works a lot with the ",
"epidermal growth factor receptor",
", which is upregulated in several cancers. However, these are more experimental techniques. As _Momotsuki explained, having a pathologist look over a biopsy is still the gold standard for most diagnosis."
] |
[
"If you had a CPU made from room-temperature superconducting material, could you overclock it infinitely fast?"
] |
[
false
] |
And would speed increase scale 1:1 with increased power forever? Would a room-temperature s.c. be the end of moore's law?
|
[
"My Background: Perkee is my name, Computer Engineering is my game. The conductors aren't of major concern. What you care more about is the switching speed of the logic gates in the computer. Logic gates are made out of transistors, which have to saturate/desaturate a semiconductor with electrons before it changes state. Electrons move at a finite speed, so you can't go infinite.",
"I don't know if superconducting semiconductor bits would make sense or make this work faster. I'm guessing that you can't have a superconducting semiconductor."
] |
[
"In addition to this, to switch each transistor at infinitely speed would take an infinite amount of current which is impossible in and of itself. Also superconductors have a breakdown current density that if they surpass, they gain resistance and thus quit being superconductors. So even if one was able to make a switching superconductor, it still couldn't be infinitely fast."
] |
[
"Actually one of the main speed limiting mechanisms in semiconductor logic is the RC charge time. Granted you can't have both a semiconductor AND a superconductor at the same time, so you'll always have some resistance. But if you allow disruptive technologies, superconducting logic has the potential for very high speeds. See ",
"this",
"."
] |
[
"Why don't people have different natural hair colors like blue or green?"
] |
[
false
] |
Are there any natural hair colors besides red, black, brown, and blonde?
|
[
"Mammals main source of coloring is melanin, which produces browns, blacks and shade of tan. Other animals such as birds have multiple types of pigment along with melanin including, carotenoids which produce red, orange or yellow feathers. Also Porphyrins, an amino acid that can produce red, brown, pink and green colors. The source of these pigments comes from many of the foods that birds eat. So the way a birds body digests and converts these substances is another thing that our bodies did not evolve to do. The forth material that produces colors like blue and green is keratin. Our hair is made up of this same material although the way keratin is used in other animals is a bit different. The structure of the keratin reflects certain light waves which makes it appear blue. The color of the keratin isn't blue itself. A birds feathers on a microscopic level can have a structure that reflects blue light. Butterfly wings also work in this way. Our hair doesn't have this complex structure to do the same."
] |
[
"We already eat many of the same foods that birds eat. Flamingos get their pink color from carotenoids in crustaceans like shrimp. The pigment is then deposited in the feathers which shows up well because the feathers start off white. No mammals to my knowledge have developed the means of converting these additional pigment materials to colors so far, so unless there becomes a strong evolutionary advantage to doing this than its hard to say, but I would guess unlikely."
] |
[
"Humans simply do not produce pigments which are blue or green. Irises appear blue or green in a similar way the sky appears blue, not due to pigments. If you ground up an iris, it would no longer appear the same color.",
"The main pigment we have is melanin, which serves an important evolutionary purpose in producing vitamin D. There's simply no benefit to producing a blue or green pigment; we already have one which does it's job just fine."
] |
[
"Why is it that when you rub your eyes you start seeing weird colours and patterns?"
] |
[
false
] | null |
[
"The act of rubbing applies a mechanical pressure on your eyes. This can cause some of your sensory cells to activate, and it will temporarily deform your retina. Because the sensory cells in your eye are typically only activated by light, and because the only signal they can send to the brain upon activation is \"I'm detecting light!\", when you rub your eyes you're essentially indirectly & manually stimulating your rods and cones in a disordered fashion, and your brain perceives this disordered input as shifting colored blobs. ",
"For example, gently poke a finger into your eye socket, beneath your eye and above the bone, while looking up. With your finger gently poking in under the eye, and while still looking up, move your eye back and forth left to right; you'll see a weird circular blob (it's like a dark oval surrounded by an irridescent shimmer) floating around the top of your vision. This black circle is a blind spot created by you poking and distorting your retina, to the point where it can't directly absorb light coming in through the pupil. Hence the dark spot. "
] |
[
"Is it harmful? The retina deformation/manual activation, I mean, as opposed to activation by light."
] |
[
"Does the dark blob at the top of your vision appear at the top because your brain flips the image your eye \"captures\"?"
] |
[
"Is the phase of AC over a very long wire the same at both ends?"
] |
[
false
] |
If you have a wire that is very long (100s of km) and you put an AC current over that wire, will the phase of the AC at both ends be the same? Considering that there is a delay between the current moving from one end to the other.
|
[
"If the wavelength of the current becomes small compared with the physical size of the wire, you have to start treating it like a ",
"transmission line",
".",
"When you manipulate Maxwell’s equations inside the transmission line, you get a set of wave equations for the voltage and current called the ",
"Telegrapher’s equations",
", and the solutions are generally damped, propagating waves. So the phases of these waves differ at different positions."
] |
[
"Let me expand on this a little, since the \"100's of km\" in your question struck me as related to power transmission (50 Hz or 60 Hz power for example), and because phase must be measured relative to something, and we should clarify that (otherwise @RobusEtCeleritas is correct on phase relative to ground).",
"In the case of power transmission, the voltages are nearly always delivered in three separate phases, 120 degrees apart (there are lots of reasons for this - it is ",
"super-handy for motors",
", and you don't need a neutral/ground, among others). In this case, the ",
" phase between the three phases remains 120 degrees, regardless of how far you transmit it. Relative to ",
", however, the phase shifts with distance along the wire as @RobusEtCeleritas notes. How much? The wavelength of 60 Hz in free space is 3e8 m/s / 60 Hz = 5,000 km (and a bit less on a power transmission line, let's say 80% slower, so 4,000 km). So yes, over \"100's of km\" the phase will shift relative to ground, and at, say, 500 km, the phase will have shifted 500 km / 4000 km * 360 degrees = ~45 degrees ",
".",
"If you are talking about high frequencies, then phase can change quite rapidly with distance. In a microwave oven (2.45 GHz) the phase is completely reversed in only a few centimeters of wire (free space wavelength is 12 cm, and more like 8 cm in wire, so reversing in only ~4 cm)"
] |
[
"Let me get a little more precise with the wording: In power systems there are Neutrals and Grounds (or Earths as some in Europe call it). Technically, Neutral is the 'return' path for the power that completes the circuit, while Ground is physically attached to ground (in your house there is a copper-clad rod driven in the ground usually near your power meter that makes the connection). The Neutral is necessary to give the current a path that closes the circuit \"back to the source\", while the ground is a safety used to protect you should something go wrong - like if the neutral line fails open somehow, the current can go through the ground wire instead of through ",
" to the ground. If you are familiar with house wiring, the black wire is power, the white wire is neutral, and the bare copper wire is ground. Neutral and Ground are generally not interchangeable (there are some details here about how and where they tie together like at your service panel, but that's a longer discussion).",
"In the case of three phase, you can wire things so the potential (voltage) you need for a device is relative to another phase, and not neutral! As a matter of fact, if you get your loads balanced well, the current flows between the three phases and none of it goes through the neutral. This is safer, saves wire, has fewer failure modes, etc.",
"If you are familiar with 240V circuits in USA homes, it is a simpler example of what's happening in 3-phase circuit. In the USA your house receives two 120V circuits from the power company, and each of those circuits are 180 degrees out of phase from one another - so when one is at its lowest voltage, the other is at its highest voltage. Thus if you measure either side to Neutral - or Ground - you will get 120V. However if you measure ",
" them, you will get 240V, because one is most negative while the is most positive and vice versa. (Interestingly, there is no way to get 240V between either of them and ground or neutral - I'll let you think about that one :-). Thus, for high-power equipment in your house (electric dryer, hot water heater, range-top, oven) you connect up both of the anti-phase 120V lines to either side of, say, a burner and the current flows directly from one phase to the other, and nothing goes through the neutral! Well, if there's no current through the neutral, why do you even need it?? It turns out that in these perfectly balanced situations you don't need a neutral. (In real life, sometime the clock or something on the stove runs on 120V, so that part connects one leg of the 240V pair to neutral, so you do wind up needing a neutral connection, though in some applications the can be smaller conductors since they carry less current). 3-phase systems are similar to this 240V system - with the right balance on the loads there is no current left over for the neutral, so it isn't needed. ",
"I hope this helps!"
] |
[
"Is a snake's digestive track in one direction?"
] |
[
false
] |
Hello. I was having a discussion with a friend about snakes and how they go about digesting their food. We kept using the frame of reference that food goes in through our mouths, then through the digestive tracks of the stomach, then eventually out. We figured snakes were the same way, except their digestive tracks are part of their elongated bodies. Then I started wondering, does food go in one direction then? Is it through the mouth, then slowly pushing toward the tail, where their output mechanism gets rid of it? Or is it through time, the food shifts from going outward towards the tail and upward towards the head, almost like a thrashing, until the food is broken up enough to exit the system? I'm not sure of these answers. This might be a dumb question on my part. Just curious though. How do snakes digest their food? Do snakes use a more powerful acid they have to break down food than humans have? Is there a rate at which the average snake passes food matter from one stage to the next? If so, how does that rate compare with humans, as its a smaller system? I'd figure if that were the case, it would be a shorter time span to eat and output waste for a snake, than it is a human, but then again, that could be wrong, maybe its not relative to the size of the system, but the differences in the digestion process from snake to human and back. Who knows? Might as well ask yall though lol. I'm not a herpetologist but one of you biology folks might be.
|
[
"I don’t know about discomfort, but I can add that after a large meal, snakes often go into an extended period of low activity.\nSo, yeah, they don’t like to move around a lot with a full belly, either."
] |
[
"When snakes eat something really big, it just kind of sits in there for a long time. You can actually see this from the outside of the snake, and the whole body of the snake expands to account for large objects."
] |
[
"Ah good point! So it just sits there in their body slowly disintegrating? Is it comfortable for the snake to do it like that? I just imagine me being bloated from a meal, the last thing I’m thinking is “let’s go move around” lol. Maybe snakes are the same way?"
] |
[
"If there are no, or minimal resistance, as in space, what are the limiting factors to the \"top\" speed of a certain propulsion system?"
] |
[
false
] |
Just read the article on the new plasma engine and was wondering what factors limit the top speed to 35 miles an hour. If there are no, or minimal resistance, as in space, what are the limiting factor to the "top" speed with a certain propulsion system?
|
[
"First off, ",
" ",
" is 35 miles ",
". As far as I know, the only physical \"speed limit\" in space (you simply can not go any faster than this) is the speed of light... Up to that point, as long as you keep adding thrust, you keep accelerating. Take the Ion Drive for example, it's not a hugely powerful engine, in fact it's pretty weak compared to chemical rockets, but it uses its fuel much more efficiently, so it can apply gentle thrust over MUCH longer periods, and eventually, you get going really, really fast.",
"In this case, I have a feeling that the top speed is a limit based on fuel consumption, i.e. we can only run this drive for so long before not having the fuel to complete orbital maneuvers, and / or the return trip... So in this known amount of time, at a known rate of acceleration, we can say that the spacecraft will be able to achieve a speed of 35 MPS before we have to cut the engines to avoid being stranded in space."
] |
[
"In the most simplistic model, kinda, but in reality it depends on your destination. If your destination is moving with respect to you, you'll be using something like a Hohmann transfer. If you're going somewhere with an atmosphere, you can aerobrake on arrival. If you're going someplace with moons, you can use them to gravity assist you and slow yourself down.",
"And of course, even in the simplistic model it's not quite half and half, because the fuel you use to speed up must speed up the craft as well as all the fuel you'll need to slow down, whereas the fuel you use to slow down must only slow down your craft."
] |
[
"Assuming you want to stop at the end of your trip, and not just continue indefinitely, wouldn't it follow that you can only use ~half your fuel to accelerate, as you'll require the same amount of fuel to decelerate at the other end?"
] |
[
"Does E = mc^2 imply special relativity?"
] |
[
false
] | null |
[
"could there be other ways like the “ether” that are also compatible with E=mc",
"?",
"Yep. You're correct. You can violate special relativity and still have this"
] |
[
"I mean you would still get heavier and heavier as you sped up",
"Relativistic mass in this sense is a bit of an outmoded concept. It is much more useful to think of mass as the rest energy/c",
". So in relativity you have",
"E",
" = m",
"c",
" + p",
"c",
"where p is the momentum. You can have non-relativistic theories which lead to the p",
"c",
" being replaced by basically any function of the momentum (you can even have directional dependence in principle)."
] |
[
"Can you expand on how exactly you could violate special relativity? I mean you would still get heavier and heavier as you sped up, so it looks a lot like special relativity"
] |
[
"Let's say i'd like to have a balloon 100km up in the air. What would be the ideal mix of gas inside the balloon?"
] |
[
false
] |
100% helium?
|
[
"Hydrogen.",
"The density of air at 100km is only 0.5 milligrams per cubic metre.",
"Hydrogen would be 0.035 mg/m",
" and helium 0.07 mg/m",
" .",
"If you had a hydrogen balloon of 200,000 m",
" , you could use it to lift a small apple. (But only if the fabric of the balloon was weightless.)"
] |
[
"With ultra-light 3.4µm polyethylene fabric, you'd need a balloon nearly 20km in radius in order for it to contain enough gas to lift its own weight at 100km altitude."
] |
[
"Thank you so much for this. (a little bit late but never too late)"
] |
[
"What is the definition of death? How long can someone be 'dead' and be 'brought back to life'?"
] |
[
false
] |
I ask because of the recent tragedies with footballers collapsing mid-game. It's being reported that Fabrice Muamba was dead for 78 minutes, 48 mins from collapse to hospital and a further 30 minutes after. He has now, a few weeks later, been discharged from hospital. My understanding was that death is the point where your brain is damaged by lack of oxygen and nutrients, usually due to the heart stopping and no longer being able to provide it with blood, to the point where it cannot regain its functions, even if you're put on a ventilator afterwards to get your heart and blood moving again. And of course there's the case of Piermario Morisini, who actually died. Part of my question is how was it possible for Muamba to 'live while dead' for over an hour while most, such as Morisini, aren't so lucky? Was it due to some treatment he received? If so why couldn't the same treatment be used on Morisini, or indeed on any of us? Was Muamba's a case of miraculously good luck? I'd heard before about people like Slash and Phil Anselmo being clinically dead after ODs and still being resuscitated, but my understanding was that the maximum one could last for was about 5-10 minutes.
|
[
"I don't think you're really asking what the 'definition of death' is. You're asking why some people survive ischemic insults that other's do not, or what treatments can prevent ischemic brain injury.",
"There is a lot of treatment using ",
"hypothermic protocol",
" to protect the brain in the event of a cardiac event. It has been proven an effective way to protect the brain.",
"There are plenty of studies and reviews ",
"one here",
" showing that 10 minutes tends to be an absolute limit for brain tissue damage being severe and irreversable. That said, the study their is older and cites 30C as the mark for cooling that protects brain tissue. We are noting that temperatures around 32 are effective as well.",
"Every human being is different, and all will respond differently. Some people suffer major brain insults after only seconds of hypoxia, while others resist the effects much longer. There is no consensus yet on which area of the brain first suffers damage as well, so it is difficult to predict the effects.",
"It would also depend on what you consider life. Any individual with an anoxic brain injury can be kept alive on a ventilator, so long as the heart is functional, and can be given parenteral nutrition if their GI system has suffered insult. It's a fine line between keeping a body alive and removing a person from life support as well.",
"Does this provide an answer for you? If not, what else would you like to know?"
] |
[
"The heart does not need to stop for brain death to occur, if your tissue cannot absorb oxygen or if your MAP(Mean arterial pressure) is below 30mmHg then the brain is not perfused.",
"Brain damage (which implies death of neurons) post cardiac arrest has many mitigating factors. Some cells can die within minutes (as little as 3 I've been taught.) Other factors also come into play.",
"This",
" is a really good write-up that I can answer more questions about if you require."
] |
[
"Shocks with a defibrillator are attempts to restore normal heart rhythm, they do not circulate any blood. It seems like your posts implies this, though I'm sure you didn't mean that.",
"The purpose of CPR is to keep the brain, heart and lungs perfused and oxygenated until the body can resume these functions on it's own."
] |
[
"Why is it faster to recharge batteries from 0-50% than from 50-100%?"
] |
[
false
] | null |
[
"It's basically like inflating a tire: when it's empty it doesn't take a lot of force to add air to it, and as it fills up more and more force is needed to add the same amount of air to it.",
"Batteries are similar, so the more energy they already contain, the harder it gets to add more. "
] |
[
"The fact that the tire is leaky is a separate concern. The issue is that the fuller the tire gets, the harder it is to pump air into it. If you've ever pumped a baseball or something similar, you probably noticed that you slow down as you get towards the end because it get harder and harder to push on the pump to add more air."
] |
[
"The fact that the tire is leaky is a separate concern. The issue is that the fuller the tire gets, the harder it is to pump air into it. If you've ever pumped a baseball or something similar, you probably noticed that you slow down as you get towards the end because it get harder and harder to push on the pump to add more air."
] |
[
"Can someone explain what exactly a \"neutron beam\" is?"
] |
[
false
] |
Inspired by . What exactly would cause such a beam to occur? Does it pose a threat to humans? Are there any other dangers of this occurring outside of a contained environment?
|
[
"to me it sounds like a mistranslation of what we'd call neutron emission. But I'm not a nuclear engineer, so I could be quite wrong."
] |
[
"What shavera said. But on a sidenote, we can indeed create neutron beams with particle accelerators. These beams of neutrons are often used to study properties of materials."
] |
[
"Neutron beams pretty much wouldn't be visible until they hit something.",
"This isn't that surprising, though - lasers are the same way. If you see a laser from the side, it is being scattered by dust/air."
] |
[
"If one section of an interferometer is orders of magnitude longer than the other, will there still be interference between the particles/beams?"
] |
[
false
] |
, B1 and B2 are beam splitters, M are mirrors, the interferometer is calibrated so that detector D1 will always detect the photon, and detector D2 will never detect the photon because of destructive interference. With the classical interpretation, interference happens between the light waves as they travel through the apparatus, and so there will only be interference if the waves interact with each other, and so when one path (let's say the upper path in the diagram) is much longer than the other path (the lower path), no interference will be detected until the wave from the other path reaches the second beam splitter (B2) and subsequently the detector(s). With the quantum interpretation, the interference happens with the , and , whether by firing particles one-by-one so only one occupies the apparatus at a time or by other means. The wave function is non-local so I'm not sure you can talk about its "propagation" in space, since its effects are "instantaneous" and sometimes can be described as propagating backwards in time. So my question is... If you do an experiment with an interferometer as described above, with one path much longer than the other (say the upper path is 1m and the lower path is 1,000,000,000m or approximately 3.33 light seconds), will you still have interference (D1 always fires, D2 never fires) in the 3.33 seconds where the light hasn't even arrived at the second beam splitter?
|
[
"they are all shorter than the coherence length.",
"They don't have to all be shorter than the coherence length. Unless the beams pass through a turbulent medium or something that disturbs the phase, you only need the difference of the path lengths to be less than the coherence length to be able to observe interference.",
"How would interferometry even work if path lengths always had to be identical?",
"They don't have to be identical. ",
"The difference in the path lengths has to be less than the coherence length.",
"If the coherence length is 5 m, one arm could be 100 m. Then the other path would have to be (roughly) between 95 and 105 m. That gives a 10 m range for one arm to change length and still be able to count fringes."
] |
[
"Almost definitely not. \nThe source emitting the light will only be coherent up to a certain point- the ",
"coherence length",
". ",
"Bearing in mind that even the coherence of ",
"laser light",
" will drift over time. This happens for every source, it just happens that lasers are the easiest to deal with. ",
"Line sources (like bulb filaments) are particularly difficult to treat, as there is no guarantee that one point emitting light at any given time will be coherent with another point on the line.\nAs an aside- this is why in the ",
"double slit experiment",
" classically a candle was used, which had point filters placed in the way of the light rays- to filter parallel, coherent rays that could be considered to be coming from a point source. ",
"I digress, back to the lasers. We can see with a handy ",
"laser diode calculator",
" that a typical laser diode sold from rp photonics has a coherence length of about 4.5 meters. So given your setup- no, interference will not occur.",
"The fact is that interferometers are always set up so that the beams are about same length when recombined in order to ensure that you don't get coherence length problems. ",
"You will not get interference if the phase difference of the two beams is greater than the coherence length.",
"EDIT: A word. I was not suggesting that the beams be precisely the same length. The question was about radically different beam lengths, I was trying to explain that they need to be roughly the same length for the phase difference to be within the coherence length."
] |
[
"it's not so outragous to think of an observational set-up with a very nice hydrogen maser, one of the mirrors is a corner cube reflector on the moon, and the other is in the same terrestrial building as the maser itself,",
"That only works if the coherence length of the maser is greater than twice the distance to the moon. Which might very well be possible --- masers are after all the basis for atomic clocks and can have extremely narrow linewidths and corresponding long coherence lengths."
] |
[
"What percentage of a computer's power consumption ends up as heat? Is a computer an efficient heater?"
] |
[
false
] |
As we know, computers convert electrical energy into heat energy. But do they convert all of it that way? I suppose some of the current ends up as electrical signals to monitors and peripherals. But what about the rest?
|
[
"Roughly all of it. Household appliances (except special cases like heat exchangers) will end up converting all the electricity they pull from the grid into heat.",
"The difference is that some (like computers) will do something useful like computing things by switching electronic gates on and off very quickly. Others, like light bulbs, will directly transform electrical energy into light and radiation which will quickly turn into thermal energy once it hits an object. "
] |
[
"I suppose some of the current ends up as electrical signals to monitors and peripherals.",
"They have negligible power (unless you charge some other object via USB or similar) and this power is typically dissipated in the peripherals then. Charging a phone and then taking the phone away is an option to convert less than 100% of the drawn energy to heat directly. You'll convert the rest by using the phone then."
] |
[
"It either goes back to the grid or comes out as heat, eventually. Which means they are just as efficient as an electric heater in that regard. ",
"They're less efficient in that they lack proper radiators to direct the heat to you, and running them at full power can damage expensive components, which doesn't happen in a heater. But in terms of what you pay per Joule? Yeah, about the same. ",
"Edit:\nHere's some literature: ",
"https://www.pugetsystems.com/labs/articles/Gaming-PC-vs-Space-Heater-Efficiency-511/#Conclusion",
"This is also true of your refrigerator and pretty much anything else that plugs in. "
] |
[
"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!
|
[
"This kind of fear has been around since the 1700s when the loom was invented, and has never proven to be true. Machines have created more jobs than they destroyed since their inception, it's just the nature of employment that has changed over time."
] |
[
"Linguistics: Why does Australia (seem to) have less linguistic variation internally than the USA? Is it because Australia is younger, or has fewer people, or is it because of a different initial mix of people? "
] |
[
"If you mean a society that works solely on plastic, then yeah definitely. ",
"Money has value in our society today because we think it does. Technically it's called fiat money, which means it's not backed by any commodity, such as gold.",
"The first banknotes were commodity backed in the sense that you could return them to the bank and get a certain amount of gold for a dollar or pound - this hasn't been the case in a long time though.",
"It seems plausible that in the future we could shift to plastic, and just the knowledge that we could return to the bank and draw money would be enough. Here money plays the role gold reserves did in the earlier example, and the economy would be cashless."
] |
[
"How does higher temperature lead to less rainfall?"
] |
[
false
] |
In wake of the CA forest fires lots of people are talking about how climate change is to blame. This doesn't make sense to me (or generally the desertification fears of climate change). I understand that at a higher temperature water on the ground will evaporate faster (but it seems like at a temp change that's very low the change vapor pressure wouldn't be that much but maybe). But where does the water go ? I would assume this would result in faster cloud formation and then more frequent rain. Plus would less water in the ice caps mean more water in the rain cycle? So I guess the general question is way does a warmer temp not just increase the rate of the rain cycle ?
|
[
"Hi G0DatWork thank you for submitting to ",
"/r/Askscience",
".",
" Please add flair to your post. ",
"Your post will be removed permanently if flair is not added within one hour. You can flair this post by replying to this message with your flair choice. It must be an exact match to one of the following flair categories and contain no other text:",
"'Computing', 'Economics', 'Human Body', 'Engineering', 'Planetary Sci.', 'Archaeology', 'Neuroscience', 'Biology', 'Chemistry', 'Medicine', 'Linguistics', 'Mathematics', 'Astronomy', 'Psychology', 'Paleontology', 'Political Science', 'Social Science', 'Earth Sciences', 'Anthropology', 'Physics'",
"Your post is not yet visible on the forum and is awaiting review from the moderator team. Your question may be denied for the following reasons, ",
"/r/AskScienceDiscussion",
"There are more restrictions on what kind of questions are suitable for ",
"/r/AskScience",
", the above are just some of the most common. While you wait, check out the forum \n",
" on asking questions as well as our ",
". Please wait several hours before messaging us if there is an issue, moderator mail concerning recent submissions will be ignored.",
" ",
" "
] |
[
"Warmer air holds more water. The air itself holds it. That’s why relative humidity is a thing. 50% humidity at 5c will feel dryer than 50% humidity at 30c. The air at 5c can only store x amount before it is full, that same air at 30c can hold way way more than said x amount. "
] |
[
"So the increase in water saturation as a gas at a temp change of 1C is more than the amount of water that evaporates? "
] |
[
"Is there a \"Reynold's number\" for electricity?"
] |
[
false
] |
Is electrical transmission in wires somewhat analogous to fluid flow through pipes?
|
[
"Electrical transmission in pipes is somewhat analogous in the sense that if you look at the equations that describe pipe flow with no viscosity or boundary layer effects, those equations are exactly the same as the equations for electrical transmission in a line. ",
"However, when you add viscosity and boundary layers, the equations for fluid flow change dramatically and no longer resemble those in electrical transmission lines. For there to be a Reynolds number, there has to be a viscosity, and so the answer to your question is probably no, there is no analogous electrical Reynolds number because there is no analog for the equations of fluid motion that yield a Reynolds number. ",
"But, and here I'm totally speculating, if you were to assume that a line had a transmission loss by resistance (Ohm's law), and that electrical mass was given by inductance through an inductor, I suppose you could define the quantity ",
"Re = L * omega / R ",
"where R is the resistivity, L the inductance, and omega the frequency. This quantity is dimensionless, and since this is something like \"inertial effects / viscous effects\", there may be an interpretation as a Reynolds number, but only in limited sense."
] |
[
"Is electrical transmission in wires somewhat analogous to fluid flow through pipes?",
"Very loosely. The conservation equations do end up taking rather similar forms.",
"Is there a \"Reynold's number\" for electricity?",
"Reynolds number is just one important non-dimensional parameter in the Navier-Stokes equations. There are other important ones, like Mach number, Prandtl number, etc.",
"There are important non-dimensional terms in Maxwell's equations as well. Things like Debye–Hückel length or relative permeability."
] |
[
"This quantity is actually referred to as the \"Quality Factor\" or \"Q\" of an inductor, interestingly enough...",
"Edit: Also, the dielectric constant of a material in it's full form includes an imaginary part which corresponds to loss... I think the ratio of the real and imaginary parts of the dielectric constant might correspond more directly to the Reynolds number, but I'm getting a little out of my depth at this point."
] |
[
"What's the difference between Gravitational lens and Gravitational waves?"
] |
[
false
] |
I was watching a video where they talked about using quantum computers to prove gravitational lens in simulation but now I hear about gravitational waves. These concepts go over my head, looking to be taught what these are and if they're related in simple enough terms. I could also just not know enough to ask the question appropriately.
|
[
"They are two complete different effects, although both stem from general relativity, our best understanding of gravity.",
"Gravitational lensing occurs when you have a mass, and due to its gravitational field -- which is basically static -- light passing by that mass is deflected. When light is deflected this way, one wind up with various effects, such as multiple images of a single object.",
"Gravitational waves are a phenomena produced by accelerating masses which have the effect of distorting space and time, and these distortions move through space like a wave."
] |
[
"Gravitational lensing is usually seen when a massive galaxy or group of galaxies is between us and something we want to see. ",
"Berkeley got a ",
" example",
" of this just last year. The link shows the same supernova on four sides of a galaxy that is much closer to us. Think of holding up a wineglass in front of a candle (or beer mug in front of a neon 'Bud Lite' sign) you can see the light (lite) behind the glass in a bunch of places from the glass. All are refracting the same light through different paths to your eyes.",
"\nThe really cool thing about lensing is that the paths are different lengths, "
] |
[
"Gravitational lensing is due to a static unchanging gravitational field, whereas as gravitational wave is how a ",
" in the gravitational field propagates."
] |
[
"Does anyone know anything on Human Cytomegalovirus HCMV?"
] |
[
false
] |
I was wondering what changes (through genetic engineering) would be necessary to make Human Cytomegalovirus (HCMV): a) more virulent/communicable b) more severe (i.e cause sterilization in humans) Any thoughts?
|
[
"Why? Are you ",
"thinking of this?"
] |
[
"Is that the virus they use in the movie? haha never saw it...",
"I'm thinking about the pros/cons of genetic engineering.."
] |
[
"That would be ",
"here",
". There is very specific moral questions and ethical concerns with this."
] |
[
"[mechanical engineering/planatery] why is 3 km/s considered as hypervelocity?"
] |
[
false
] |
wouldn't it be more accurate to describe it as hypersonic? afte rall in space we have hypervelocity objects flying closer to a few of kilometers per second which does make the hypervelocity limit on earth seem a bit too low to coin it as such
|
[
"I think the Wikipedia article actually describes it pretty well. It is the point where structural materials such as metals behave more as a fluid on impact than a solid/metal. Hypervelocity contains a pretty wide range of velocities ranging from a few km/s to tens of thousands of km/s."
] |
[
"The meaning also depends on context.",
"To an astrophysicist, a hypervelocity star is one that is traveling too fast to stay gravitationally bound to its parent galaxy. It is believed that these exceptional stars and planets were boosted beyond escape velocity by ",
"rather rare circumstances",
" involving a binary star pair, a black hole, and a slingshot maneuver. ",
"Many nearby stars are quite slow measured relative to the sun, often 20-30 km/s. Barnard's Star is exceptionally fast at 142 km/s true relative velocity. 13,333 km/s is fast even by astrophysicist standards."
] |
[
"It's not part of the definition of hypervelocity, but 3 km/s is also about the point that an object's kinetic energy is equal to the explosive power of an equivalent mass of TNT. When you're hitting an object that fast, it's similar to setting off a bomb."
] |
[
"Is it possible to weaponise a placebo?"
] |
[
false
] |
I was wondering if you made a harmless gas that looked, smelled, and sounded like, say, mustard gas, would that incapacitate soldiers who didn't have gas masks?
|
[
"Well, for a placebo effect to work, you need to convince someone that they should be effected in some way. But you're not going to get any effect just because you tell someone they should. For something like mustard gas, you would know if you had been exposed. After a minute of no obvious effect, people will figure it out. It's much easier to get a placebo effect for something that is less well defined, like a headache. Tell people they'll be exposed to a gas that gives headaches, you'll probably get a small placebo effect.",
"What's more likely is that you promote the idea that you'll be deploying chemical weapons, then pretend to deploy them, and people will get the hell out of there. That's not a placebo effect though, that's just people making a decision (stay vs. leave) based on the evidence available to them."
] |
[
"Well... What gas are you using? Is it in an enclosed space? Is it denser than air? What doesn't mustard gas smell like? Would soldiers know what it smells like? ",
"Remember that any gas still displaces air. If it does this at a fast rate it can be dangerous. Liquid nitrogen is dangerous because it displaces air quickly and can incapacitate people since they run out of oxygen. "
] |
[
"It's not impossible. Mass conversion disorders are physical disorders that have a psychological cause. The weirdest one I ever heard about was mass temporary blindness. Basically, you get enough people in a place to experience a symptom and the belief can spread. Sometimes you see it with something like seizures or other conditions. It's important to note that the physical symptoms may be genuine; it's not as if people are just \"faking it\". Since this is a phenomenon observed in the regular world, I suppose it is possible to engineer a scenario that could produce it. I don't know what that would be, and it might not consistently work.",
"That is different than the placebo effect though, I suppose, but my suspicion is that some theater might be part of this hypothetical weaponized conversion disorder paradigm. If so, maybe using a fake gas or something might be part of the show."
] |
[
"What the primary cause of the median income benefit from attending a 4 year university?"
] |
[
false
] |
I know the median college grad in the US earns over a million more dollars in their lifetime than the median high school grad. Is this entirely due to the benefits of the degree, or is there a statistical bias? It seems that many people I know who earn a degree don't use it at all, but do well in an unrelated field. If this question is too detailed for an askscience post, is there a good review on the subject available?
|
[
"Right so there are two questions you're asking here. One is:what is the effect of a 4 year university degree on earnings, all else the same? The second question is a statistical question: what is a statistical bias of a parameter and how does it apply here? ",
"Ok So lets begin. ",
" To first answer your question, the effect of a four year degree is massive. I'll use the following space to explain a lot more. ",
"Let's talk briefly about a standard regression: a classic example used in statistics classes is adult height as a predictor for adult weight. We know a couple things about this, height and weight have a relationship in a positive direction (i.e. the taller you are the more you have to weight). We know that it's a better model to use height as a predictor for weight rather than weight as a predictor for height (i.e. just because you're fat doesn't mean you're tall). We also know a lot of other things affect weight besides just height (e.g. gender). In addition to having more things that affect weight, we also have a distribution for a single height. Many people at one height level will weight different amounts. So we put all these points of data into a computer (or by hand if you're fucking brilliant...which is impossible), and figure out that height loosely predicts weight and there is some basic amount that everyone will weight by default. We can say for every inch you're taller, you're likely to 7 lbs more. But suppose we only have fat dudes in the data set that number, 7lbs per inch would be much larger like 10 or 12 lbs per inch. That is a directional bias. With out getting too much into statistics, there are ways of seeing how good your model is at predicting their weight or how good each parameter is at predicting weight. ",
"Cool now that we have talked about what a basic model looks like lets talk about your question. We can make a model that will take inputs like height, weight, parental income, education level, and use these inputs to try and predict income. Now the biggest issue here is the MASSIVE distribution we can have for one education level. What makes Bill Gates/Mark Zuckerberg/Steve Jobs/Gabe Newell different from the guy in Starbucks? Those billionaires previously mentioned never even graduated from college. There has to be something statistically different about them right? Well having four people isn't enough to give us good insight into what is going on here though. We know that a lot more is happening than just the stuff we listed in our model. The issue that we're having is all the stuff not listed is affecting our ability to predict income. Even worse it affects each parameter we've included. That said some parameters are so powerful that even with all of the bias included, we can still say that have an effect one way or the other. So lets talk about what we do know.",
"First of all we can say pretty certainly that a four year degree is an indicator of many things other than just knowledge. It can be an indicator of intelligence, diligence, dedication, leadership, etc. Think about everything learned in college both inside and out of the class room. Everything from organizing your life, and activities all the way over to practicing getting along with classmates and roommates. These all can positively affect your income but are not necessarily the direct result of knowledge accrued, in class, from a four year degree. So imagine when we include a four year degree or equivalent as a place holder, suddenly we have something that is adding a lot bigger of a boost to predicted income than just the knowledge. The boost in the direction is bias. ",
"Now a few questions for you so I can help you go further into the subject. How much statistics are you comfortable reading about? Do you want to read econ papers or will wiki suffice?",
"I'll append a few articles for you to begin explore more and as always feel free to ask questions.",
"Here is a great ",
"chart",
" from the Bureau of Labor Statistics. ",
"NYTimes",
" article on return on investment of colleges.",
"Definitions of types of bias from wiki (no pretty link because of the url parenthesis): ",
"http://en.wikipedia.org/wiki/Bias_(statistics)",
"Tools of the trade: \n",
"Regression",
"then more specifically",
"Econometrics"
] |
[
"Ok. I wrote that at 2 am and kinda left out some of the big links. ",
"Borjas wrote one of the better/best text books on labor economics. ",
"This is a slideshow",
" of some basics on human capital development that I think he put out. Either way the information provides a basic breakdown of a earnings as a function of inputs.",
"So for an OLS model, Y = b_0 + b_1 X_1 + b_2 X_2 + U",
"The bias you incur on each b_i is entirely dependent on the variables that you have included. This wiki article explains the direction of the bias for ",
"omitted variable bias",
". The main point I'm trying to make is you would have to first select a specific model to be able to do a write up on what biases are included in their estimation of the effects of a four year degree. Now the honest answer is that you can include literally any variable under the sun and if it turns out to have some significant predictive power, then it is an omitted variable bias if it is not included in the regression. ",
"A commonly used earnings model is the ",
"Mincer equation",
". In this particular model, as mentioned in the Borjas slides, some OVBs may include ability/skill or leadership. These would all have the estimaters over estimate their true beta value. "
] |
[
"Thank you for the great write up. I read the links you provided, and they provide good background on the total difference, but they didn't provide any background on what those differences came from.",
"Honestly, I'd rather not papers on the subject, as I read enough papers in my day to day job. I am quite familiar with statistics, however. I am looking for a specific write-up by someone who has attempted to separate the benefits of a 4-year degree from the various biases that naturally arise."
] |
[
"If you looked into a box with mirrors in the interior..."
] |
[
false
] |
[deleted]
|
[
"If the two way mirror was \"perfect\" you would not be able to see anything inside of the box because there wouldn't be a light source."
] |
[
"Theoretically perfect mirrors would just keep the light bouncing around inside the box forever. You wouldn't see anything in that case, because the box would be opaque.",
"It makes sense if you think about what happens to a photon in the box. It'll travel in some direction, and hit a wall, and then there are only two things that can happen to it: either it goes out through a two-way mirror, in which case you see it, or it gets reflected back into the box, in which case you don't.",
"In reality, there's a third option: it gets absorbed and its energy turns into heat. Every real material absorbs some photons, and that's why real mirrors are never perfect."
] |
[
"What it you closed the two-way mirror on the box, trapping light in it. What would you actually see?"
] |
[
"Can the Tetris effect include sounds too?"
] |
[
false
] |
The Tetris effect is when a person looks at a pattern so much that when he or she closes his or her eyes, the pattern can still be seen. So if a person heard a repeating noise enough does the same thing happen? Furthermore, why does the Tetris effect happen?
|
[
"I was actually going to bring up pokemon. I'd love to see some actual studies verifying it though."
] |
[
"I was actually going to bring up pokemon. I'd love to see some actual studies verifying it though."
] |
[
"I remember reading an article on something similar to what you're describing, however it was only looking at the phenomenon after long exposure to games. They coined it ",
"game transfer phenomena",
", wherein you hear sounds from video games after you stopped playing. There doesn't seem much about it online, but I've certainly experienced something similar after playing video games for an extreme amount of time."
] |
[
"Why is the set of real numbers between 0 and 1 uncountable, but not the set of all integers?"
] |
[
false
] |
The answer that I have found elsewhere is that the integers can be listed as such 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13... and that the same cannot be done for the real numbers between 0 and 1. I don't see why this is true because I can list them as follows. 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.01, 0.11, 0.21, 0.31... Notice that there I have constructed the second list by taking the mirror image of the first list about the decimal point, so there is definitely a 1 to 1 mapping of integers to real numbers between 0 and 1. The other reason usually given is that if you take a set which is assumed to contain all the real numbers between 0 and 1 then you can create a new number by making the first digit different than the first digit of the first number, the second digit different than the second digit of the second number and so on. But you can also do this with the integers! Just create a new integer and make different than the first number in the ones place, different than the second number in the 10's place and so on. Please help me see where I am wrong above.
|
[
"I don't see why this is true because I can list them as follows. ",
"0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.01, 0.11, 0.21, 0.31... ",
"This enumeration will never reach any real number that has a non-terminating decimal expansion. For example, 1/3 or 0.333...(repeating).",
"But you can also do this with the integers! Just create a new integer and make different than the first number in the ones place, different than the second number in the 10's place and so on. ",
"This doesn't work because every integer has a finite number of digits. It can be a very large number, but it'll still be finite. So there's always a way to enumerate the integers in such a way that any integer is reached within a finite number of steps. Specifically, by just enumerating them in their normal order, the number X and be found on the X+1",
" spot in the list.",
"The crux of the matter is that because real numbers don't always have a terminating decimal expansion, nor a fractional representation (in fact: most don't), such an enumeration isn't possible with reals."
] |
[
"You do not have ",
" irrational number in your list. You don't even cover all rational numbers, although that is possible with different approaches."
] |
[
"An underappreciated property of countable infinity is that every element is finitely reachable. There's an infinite number of elements, but by virtue of being able to list them out, each of the infinite number of elements is at a finite index value. In principle you can \"reach\" any element of an infinite countable set in a finite number of steps.",
"Your list of real numbers does not have the number 0.111111... at any index value. Name any list index of your real number list and you can compute the number of decimal digits the number at that index will have. It is a finite number of digits, proportional to log(n) for the nth number in your list. So 0.11111... cannot appear at any nameable point in your list. No number with an endless decimal expansion will appear in your list, and that's most real numbers.",
"But you can also do this with the integers! Just create a new integer and make different than the first number in the ones place, different than the second number in the 10's place and so on.",
"Try it on the easiest list of integers -- just the integers in order. What is an example of an integer whose Nth digit differs from the Nth digit of N? The 7th digit of 7 is..., well, you have to preface that 7 with a bunch of 0s for that to make sense. So the 7th digit of the new integer you're creating has to be different from 0. Same for the 8th digit, and 9th digit, and so on. You quickly find the Nth digit of the new integer you're constructing cannot be 0 for N > 1. This means the integer has an infinite number of digits. That's not an integer."
] |
[
"Oceanography - help is much appreciated!"
] |
[
false
] |
Hello AskScience. I am in the midst of writing a paper for my Oceanography class, and I have hit a slump in terms of sources for my topic. I chose to write my paper on the effects of natural disasters (such as the March earthquake in Japan or Haitian quake) on sea life/ecology, and am running aground (pun intended). If anyone knows of any good links to credible oceanic websites that may have information, or if anyone happens to know of some good articles on the subject, I would be forever in your debt! Thank you for your time! TL;DR I need help finding sources pertaining to the effect of natural disasters on oceanic life.
|
[
"Are you aware of google scholar? It's an excellent tool.",
"For example, I used it to find this"
] |
[
"Google Scholar"
] |
[
"Try Google Scholar as mentioned, and make sure to try many different keywords. If you are in college, go to your library and ask your librarian which databases you have access to. You could try databases like \"Fish, Fisheries & Aquatic Biodiversity Worldwide\". For example searching for \"tsunami\" gives you 1220 results to sort through, most about ecological effects post-tsunami on fish, fisheries, and aquatic biodiversity (as the database name indicates)."
] |
[
"Why are vaccinations only effective if everyone in a population is vaccinated?"
] |
[
false
] |
There's a pertussis outbreak where I live due to a small group of people who don't vaccinate their children. Many of the cases involve kids who were previously vaccinated against pertussis. Why will people catch diseases that they're vaccinated against? What type of exposure does a vaccination protect against?
|
[
"The vaccine for whooping cough (to use your example) is about 85% effective, and this is because people's immune systems do not always develop a perfect immune response to a vaccine. ",
"Let's consider a boring person's life. Let's say this guy goes from home to work, and only ever sees the people he works with and his boring wife who never leaves the house. His coworkers are equally boring. They like to trade sandwiches after taking a bite. One of their spouses gets whooping cough. We'll take a few example cases:",
"Only Mr. Boring is vaccinated. Mr. Sickwife is not vaccinated, and will likely get the cough from his wife and bring it to work. Mr. Boring has a 15% chance of getting sick, and everybody else at work is close to 100%.",
"Half the people at work are vaccinated, not including Mr. Sickwife. He's going to get it, and bring it in. Mr. Boring's risk is still 15%, and the unvaccinated coworkers are still at high risk. ",
"Half the people at work are vaccinated, but including Mr. Sickwife. Mr. Boring's risk is down to 2.2%, and the unvaccinated coworkers are down to 15%. ",
"All his coworkers are vaccinated. Now, there's a 15% chance that Mr. Sickwife gets infected. Everyone else at work's odds are 2.2%.",
"All the coworkers ",
" are vaccinated. There's only a 15% chance that Mrs. Sickwife gets sick in the first place. Mr. Sickwife's odds go down to 2.2%, and Mr. Boring and the other coworkers are down to .3%.",
"Edit: put \".003%\" where I should have used \".003\" or \".3%\". "
] |
[
"Not to say there is anything wrong with this explanation (because there isn't), but here's another, slightly more abstract way of explaining it. When someone gets sick, they'll pass the virus on to their friends and coworkers, and those people will pass it on to ",
" friends and coworkers, and so on. The key question is: when one person gets sick, how many of their friends are they going to successfully infect ",
"? If each sick person infects an average of ",
" one other person, then the number of people that get sick will grow at each step, and you get an epidemic. (Kind of like a chain reaction, except with sick people) But if each sick person infects an ",
" of ",
" one other person, the number of sick people at each step becomes less and less, and the virus dies out.",
"Pretty much everything that we do to limit the spread of an infectious disease is aimed at reducing the average number of people that one sick person will pass the disease on to. That includes vaccination. When you get vaccinated against a disease, it reduces the chance that you will get infected, even if you are exposed to the virus. Therefore, hopefully you can see that if a lot of people are vaccinated, then one sick person will infect fewer people on average. For example, suppose one sick person regularly interacts with 20 other people. If nobody is vaccinated, that sick person might infect 15 of the 20 other people. If half of them are vaccinated, the sick person might infect 8 of them. And if they're all vaccinated, the sick person will only ",
" infect 1, on average. (I just pulled those numbers out of a hat)",
"Perhaps you can see where I'm going with this: the number of people that a sick person infects, on average, goes down when the percentage of the population which is vaccinated goes up. If enough people are vaccinated, the average number of other people that a sick person infects will drop below one. And that's what makes the difference between an epidemic and an extinct disease."
] |
[
"To be fair, from a medical perspective, the importance of ",
"herd immunity",
" is also about protecting the immune-deficient, elderly, vaccine non-responders and the unvaccinated (including children before the age of vaccination)."
] |
[
"Why not 1024bit encryption or beyond?"
] |
[
false
] | null |
[
"512 bit encryption gives you about 10",
" possible keys. If you took every single atom in the known universe and somehow turned every single one of them into the fastest supercomputer ever build, it would still take an unimaginable many times the age of the universe to try all possibilities. While quantum computers lower that number, it doesn't really change the overall message. Forget about it. ",
"The only caveat is where there are better attacks than simply trying all possibilities. Eg. RSA do use 1024 and higher bit encryption.",
", I did not mix up symmetric and asymmetric encryption. I explicitly wrote that if you can do better than simply trying all keys the first argument does not apply. And even used RSA as an example. If an attacker wants to find the prime factors by simply trying all primes (simple brute force) he essentially has to go through all possible numbers of up to the length of the key. ",
"You point out he can skip composite numbers. But by the prime number theorem about every log(N) number is a prime, so for 1024 bit keys that's about every 1000 integer. So that only gives you something like 10 bits of security less.",
"And that's even ignoring the problem of how an attacker knows if a number is prime or not. He could skip even numbers and perhaps a few other tricks, but in reality that would not gain him much. The main reason RSA keys are so long is because we have much better attacks than brute force.",
"This has nothing to do with symmetric or asymmetric in particular. I could make a symmetric scheme that was secure but still had better than brute force attacks."
] |
[
"Careful, you're mixing up symmetric and public key encryption. In symmetric crypto, the key space is fully usable, meaning you really do have 10",
" available keys. RSA on the other hand uses large prime numbers, so there are a lot of holes in the space. That's why you see 4096 bit keys in RSA and 256 bit keys in AES, with both being estimated as having approximately the same strength, if I recall correctly."
] |
[
"Please correct me if I'm mistaken, but my understanding was that a classical 512-bit encryption key that could be deciphered by a quantum algorithm would require only 512 qubits to do so."
] |
[
"How easy / difficult is it to *NOT* catch an illness in a pandemic situation?"
] |
[
false
] |
Let's say some lethal mutation of the flu virus goes pandemic in a worst-case scenario situation. Would my germaphobic habits give me a reasonably good shot at survival? I guess it just seems that most people catch viruses from unhealthy or at least germ-friendly habits. Or from their kids. Sure there's the unlucky possibility of somebody sneezing on your face, but that's pretty rare.
|
[
"It depends really. If the virus/illness/what-have-you is air or waterborne, it can be difficult to avoid until it's too late. If it's a person-to-person kind of illness, it can be a bit easier to avoid, and I think the habits you've developed as a germ-phobic person may make this kind of \"pandemic\" easier to avoid.",
"However given that pandemic situations are a lot different than normal virus spread, it may not work as well.",
"Perhaps the best bet is to move to Madagascar."
] |
[
"I realized about 90% of the way through that my statement sounded a lot like the game Pandemic (which wasn't intentional), so I threw the Madagascar thing in as a half-joke.",
"Truthfully it might still work out though; since the island has a pretty crappy travel infrastructure overall (thus making it difficult to spread disease via person-to-person contact, as getting to other people will be problematic), and with travel likely being restricted during pandemic-type conditions, it wouldn't be unreasonable to think Madagascar would be a good place to go."
] |
[
"Wait, are you serious about Madagascar, or are you just referring to the games Pandemic?",
"Edit: Sorry if this isn't science related but I'm just curious."
] |
[
"Are there solar systems of stars, where a supermassive star has a group of smaller stars revolving around it?"
] |
[
false
] | null |
[
"Even large stars don't have ridiculous masses, so all of the stars end up orbiting each other, so it won't be quite like a solar system with one in the middle. One of the largest and heaviest stars is UY Scuti, its about 1,700x as large as the sun, but only about 32x heavier so if you put it and the the sun in a system together they would both orbit the common center of mass which would be outside both stars, in our solar system the center of mass is within the sun so it seems we orbit the sun.",
"There are larger multi star systems, Alpha Centauri is a triple system made of Alpha Centauri A, Alpha Centauri B, and Proxima Centauri. The biggest multistar systems i can find reference to is Nu Scorpii which is at least a 5 star system but believed to be a 7 star system, and AR Cassiopea which is known to be 7, this is about as close to a solar system of stars as you will find!"
] |
[
"UY Scuti is one of the largest known, but nowhere close to being the most massive. The heaviest ones are well over 100 solar masses, with ",
"R136a1",
" clocking in at a whopping 265 times the mass of the Sun."
] |
[
"Yes, they are called binary stars. They make up roughly 1/3 the number of stars in our galaxy. Although you if you mean more than 2 stars that's rare but there are a few potentials. If you are willing to be loose with the definition of a star, the current theory is that every galaxy has a super massive black hole at the center. A black hole being a remnant of a star, it could loosely fit the question. "
] |
[
"Why is personality an inheritable trait in dogs?"
] |
[
false
] |
Is personality reinforced over generations of breeding?
|
[
"The same reasons personality is fairly heritable in humans."
] |
[
"The only guarantee is that your kids won't find either of you funny. ;) (sideways glance at etiquette bar)"
] |
[
"Though it doesn't answer the entire question, ",
"Brunner's Syndrome",
" is a nice example of a clear link between genetics and personality in humans. In Brunner's a mutatation of the MAOA gene for the MAOA (monoamine oxidase A), which is responsible for breaking down lots of brain neurotransmitters, stops the enzyme from working properly. This leads to increased levels of neurotransmitters in the brain, leading to various aggressive and destructive behaviours.",
"Brunner's is an example of a single gene disorder, but many characteristics are determined by the combined effects of several genes and the environment. For example there are several genes which are believed to increase the likelihood of developing type 2 diabetes, but this is often only in combination with environmental factors, such as obesity etc.",
"The heritability of personality may be due to a combination of many different genes, for example slight variations in the efficiency of MAOA and other similar enzymes would alter levels of neurotransmitters in the brain. Similarly variations in receptor sensitivity, hormone release and many other things could subtly alter personality, and these would be inherited from the parents of a dog.",
"Modern genetics is not advanced enough to fully understand how personality is inherited beyond simple single gene disorders such as Brunner's, as there is a complex interaction of many genes and environmental factors."
] |
[
"Could it ever be possible to invent a bionic eye that allows people to see light outside of the visible spectrum, such as ultraviolet or infrared?"
] |
[
false
] | null |
[
"Your brain could probably handle the input anyway, experiments have shown that mice and new world monkeys are capable of comprehending the difference between red and green after having their natural red-green colorblindness fixed by gene therapy."
] |
[
"There is a crappy first link from a little googling, but I recall some people getting their lenses replaced with ones that transmit UV. Normal lenses in our eyes absorb UV (hence the cataracts), and some of the synthetic lenses transmit UV. (I recall anecdotally they stopped implanting these because of the below effects freaking people out). ",
"Anyhow, some portion of the population has some mildly UV sensitive photoreceptors, so in this subset of the population whom had UV transmitting lenses inserted, they could see near UV. ",
"Apparently it's spectacular, and honestly I wish I could reasonably afford to have the replacement lenses put in myself, I'd love to see the world as the birds and bees do (google some UV flower photos if you doubt the difference)",
"http://www.komar.org/faq/colorado-cataract-surgery-crystalens/ultra-violet-color-glow/",
"http://en.m.wikipedia.org/wiki/Aphakia",
"Edit: just realized that doesn't answer OP, still cool. "
] |
[
"The short answer is yes, the bionic eye would need receptors that are responsive to the spectrum (Ultra-Violet and Infrared are just beyond the range of the human visual spectrum) and then it would need to transmit the signal through the optical nerve. Although it's important to note that it's actually the activation pattern in the brain that determines what color you will \"see\"",
"Sensation (stimulus detection) is not the same as perception (sensory experience). "
] |
[
"How does the gene mutation originated in a single individual becomes the evolutionary change for the whole species?"
] |
[
false
] |
Suppose an advantageous mutation happens in Eve, then I understand how her descendants would inherit that gene. But even after a millennium or so, the Eve clan would still be an abysmally small percentage of humans as a species. Do multiple individuals go thru the same changes at the same time so that after millions of years the original mutation becomes the norm? How does this synchronization happen? Hope I have explained my doubt clearly. Edit: My question is - how does it happen in unrelated individuals at the same time?
|
[
"Do not listen to that person. They are wrong. That's not at all how evolution works. For a gene to mutate and then be favorable in a single individual is not evolution, and it doesn't just happen that simply. And favorable genes are not just selected to be passed down. That's a misunderstanding of natural selection. Genetic transfer onto progeny is random. Hence Mendel's law of random segregation. Favorable traits are not \"chosen\" because they are favorable. If that was the case, we wouldn't have Down syndrome, or Kleinfelters or any other genetic disorders. \nSometimes mutated genes are randomly selected to be passed to progeny. Sometimes they are favorable in their environment. Sometimes they are not. Sometimes the favorable trait will allow for greater survival and therefore that organism may outlive a wild type. But that also doesn't mean that the wild type is now inferior and will die out. If that was the case, there wouldn't be millions of living species on the planet. Factors like gene dominance, and population size hugely affect evolution. ",
"Edit: typo. Also, sorry my thoughts are scattered. I was in a huge hurry to shut that person up before you became severely misinformed. "
] |
[
"If the mutation has a significant survival/reproductive advantage, then non-Eve clan people would be less fit, and Eve clan descendants would comprise a significant proportion of the population. If you're saying that the mutation is advantageous but only in a minor way that doesn't really affect fitness then there's no reason that there would be strong pressures selecting for that trait, and it would be more prone to being affected by genetic drift instead.",
"If the environment is selecting for a particular trait, then you can get any number of mutations that result in a trait that confers the advantage (say, cold tolerance in face of cold weather). It doesn't have to be the same mutation in the same location or even the exact same trait (e.g. increased hair vs. more effective heat generation vs. better food acquisition skills); as long as you get a fitness advantage evolutionary pressures will select for that trait no matter what."
] |
[
"First of all, since (almost) all cells in our body contain DNA, there are lots of places for mutations to occur; however, not all mutations matter for evolution. Somatic mutations occur in non-reproductive cells and won’t be passed onto offspring. Now, once you have a mutation in a gene that CAN be passed onto a offspring basically what you get is more variation. Sometimes, perhaps this offspring does not get any offspring of its own and hence this mutation would go lost - even if it was very beneficial. Sometimes it gets passed on further to in the offspring, and slowly its presence in a population increases. Here is a quite good intro link on ",
"mutations",
".",
"Bear in mind that in a population there is already variation (in other words allels, different variants of the same gene) and this is something natural selection, sexual selection and genetic drift can act on. What you need is something in the environment to change, which inturn could favour individuals with allele A instead of allele B. Now, over time, the percentage of individuals carrying allele A in this population will most likely increase and there you have it, evolution. My understanding is that speciation is a process that tends to act on pre-existing variation, while mutations are what creates variation in the first place. It is also worth to remember that the concept of species is fairly vague."
] |
[
"How can planets within a galaxy maintain their orbit, when their galaxy is being cannibalized by another roaming galaxy? Also, how do galaxies roam around in the first place?"
] |
[
false
] | null |
[
"Stars within galaxies are spread out incredibly far. Consider the fact that the nearest star to our sun is 4 light years away. Galaxies are mostly empty space.",
"Galaxies roam around under the influences of their own inertia and the gravitational forces exerted upon them by other galaxies"
] |
[
"This is the best answer. The space between any significant objects in a galaxy is mind-numbingly vast. Even if two galaxies were to encounter each other head-on, the chances of the objects (stars, planets, whatever) colliding with their respective partner's others is very, very small. However, the gravity with all of the combined masses would leave a visible mark on each galaxy after the \"collision\". "
] |
[
"Gravity decreases with the square of the distance. So a planet is influenced much more by the star it orbits around than by an entire galaxy thousands or millions light years away.",
"The same is true for our planet, its orbit is not greatly influenced by the rest of our galaxy."
] |
[
"are compounds / alloys / materials / etc routinely checked to ensure they experience the 'correct' amount of gravity?"
] |
[
false
] |
To start with, I know this is a stupid question, but I've Googled lots & can't prove it obviously wrong. *everything has mass, easily measured by gravitational effect (weighing it) *everything has a density, again straightforward - mass / volume = density. But do we verify everything is as it should be? We seem to measure mass by weight, but what if by some quirk, a certain material only experiences 95% gravity? Are there common tests (perhaps using momentum?) to check the mass of a material is what weight indicates it should be? there be alloys, plastics, compounds, whatever out there which 'weigh' less than they should & we haven't noticed? As stated at the start, I know this is stupid, but it's not been as easy to debunk as I expected.
|
[
"It sounds sort of like you're asking about the equivalence principle, which says that the mass that makes things difficult to move (inertial mass) is the same as the mass which makes things experience gravity (gravitational mass). The first direct tests of this were done by Lorand Eotvos, and there are some experimental groups testing the equivalence principle with higher precision. You can read a bit about it ",
"here",
" (pdf)."
] |
[
"This",
" is a paper describing an experiment to be performed in the near future to test the weak equivalence principle, which, as ",
"/u/iorgfeflkd",
" mentioned, is very related to what you're asking. So research testing this is still ongoing."
] |
[
"Thanks & thanks to InfanticideAquifer too.",
"I knew it was a daft question, but didn't know the name of the principle so my googling was going nowhere. Found it really interesting people are testing actively testing it."
] |
[
"Is IQ a predictor of personality traits, such as empathy or antisocial behavior?"
] |
[
false
] |
Fairly simple question with, I'm sure, a fairly complicated answer. Is the measurable intelligence of a person in any way related to their likelihood of being a functionally integrated, relatable member of society? Are those with high IQs more likely to be sociopaths, or have higher emotional intelligence? Are those with low IQs more likely to be aggressive and antisocial, or are they more likely to be empathetic?
|
[
"But it's not quite as simple as it might seem and we'll need to cover a little about statistics. ",
":",
"http://law.jrank.org/pages/1363/Intelligence-Crime-Measuring-size-IQ-crime-correlation.html",
"Terrie Moffitt and colleagues studied 4,552 Danish men born at the end of World War II. They examined intelligence test scores collected by the Danish army (for screening potential draftees) and criminal records drawn from the Danish National Police Register. The men who committed two or more criminal offenses by age twenty had IQ scores on average a full standard deviation below nonoffenders, and IQ and criminal offenses were significantly and negatively correlated at r = -.19.",
"http://psycnet.apa.org/journals/abn/90/2/152/",
"Donald Lynam and colleagues studied 430 seventh-grade boys in Pittsburgh, Pennsylvania. They measured both IQ and self-reported participation in delinquent acts. Those boys who committed serious delinquent acts, such as stealing cars, breaking and entering, or selling drugs, scored 8–10 IQ points lower than boys who had not. IQ scores and delinquency were correlated at r = -.22, with the correlation between verbal IQ and delinquency being much stronger than the correlation with performance IQ (r = -.33 versus -.06).",
"http://psycnet.apa.org/psycinfo/1997-05214-008",
"Hakan Stattin and Ingrid Klackenberg-Larsson followed 122 Swedish males from ages three though thirty. They measured IQ at ages three, five, eight, eleven, fourteen, and seventeen and counted the number of registered criminal offenses through age thirty. Frequent offenders, those men with four or more criminal offenses, averaged IQ scores of only 91 points; sporadic offenders averaged 97 IQ points; and nonoffenders averaged a full 102 points. Remarkably, IQ at age three significantly correlated with registered crime at (Spearman's) rho = -.25. IQ at the later ages also correlated with crime at around rho = -.20.",
"https://www.researchgate.net/publication/231928892_The_Relationship_Between_Maternal_Attributes_in_the_Early_Life_of_the_Child_and_the_Child's_Future_Criminal_Behavior",
"Deborah Denno analyzed data from 987 African American school children in Philadelphia. Her data contained multiple measures of intelligence collected at ages four, seven, and thirteen as well as officially recorded criminal offenses. Chronic, violent offenders consistently had low IQ scores. For example, female chronic offenders were almost four times less likely to be in the top third of verbal-IQ test scores than female nonoffenders. Similarly, male violent offenders scored 10 to 17 percentile points lower on measures of vocabulary, reading, and language than nonoffenders.",
"https://www.ncjrs.gov/App/abstractdb/AbstractDBDetails.aspx?id=105466",
"But these are all relatively low correlations.",
"This graph with invented data",
" helps illustrate why the correlation can be so low. ",
"Because serious criminal behaviour is reasonably rare the correlation is mostly in one direction. Criminals are likely to have low IQ's (at least the ones who are caught or admit to it in surveys) but any given person with a low IQ isn't very likely to be a criminal. ",
"Most people, high or low IQ tend to integrate into society. \nSo whatever someones IQ they ",
" still won't be a criminal. ",
"Here is a graph of mean income by IQ decile.",
"Source:",
"http://tino.us/2011/04/david-brooks-and-malcolm-gladwell-wrong-about-i-q-income-and-wealth/",
"Other test scores which tend to correlate with IQ also tend to correlate with income",
"But studies tend to show that the correlation between income and IQ is only 0.4 or so or 16% of the variance. Which is still pretty low.",
"Again lets refer to a ",
"graph with invented data with similar correlation.",
"There can be very high variance within the individual deciles so even if overall IQ is very informative any particular individual can do pretty well. ",
"The invented data illustrative graphs are from:",
"http://slatestarcodex.com/2015/05/19/beware-summary-statistics/",
"There's a set of people with a strange dislike of intelligence measures of any kind who desperately want to avoid ever accepting that there's any real relationship between IQ and various things but theirs is very much a political position where the conclusion informs what data may be accepted, like lysenkoism. "
] |
[
"I'd caution you about assuming causation here. It's not hard to imagine that those with criminality risk factors are also unlikely to get a decent education - and the lack of education will reflect as a low score on an IQ test."
] |
[
"Statistics like that are unable to reflect the impact of other factors that occur as income rises. In the data referenced, there would need to be further specific study to discover what factors would lead to that decline in relative earning. ",
"For example, some studies have shown that after a particular level of income had been met and the earner's fundamental needs are being met securely, then happiness derived from additional income begins to plateau. That, in turn, can affect the earner's decision making process for how they choose to spend their time and energy. ",
"Other studies have shown inflection points for higher IQ people and social engagement, happiness and even lifespan. As you mention, it would be interesting to see a multivariate examination of those factors, especially if it were conducted to also consider one's culture of origin. "
] |
[
"How big would a typical iron magnet have to be to have a field with the same magnitude as the earth's magnetic field?"
] |
[
false
] |
If you had a normal fridge magnet, how large or massive would it have to be to produce a magnetic field the same size of earth's?
|
[
"Do you mean magnitude of the magnetic field, or the vector field? If it's the former then a regular fridge magnet actually has a magnetic field 100 times the strength of Earth's. For the latter, you would need a bar magnet the same diameter of the Earth - in fact you can approximate the magnet field of Earth by imagining such a bar magnet going through the ",
"center of the Earth"
] |
[
"The Earth's core is a fairly weak magnet in the sense that the maximum magnetic field strength it produces, even inside the core, is weaker than what you get from a fridge magnet. The average internal field inside the core is about 25 Gauss (",
"http://newscenter.berkeley.edu/2010/12/16/earth-magnetic-field/",
"), the field at the core edge (core-mantle boundary) is maybe around 4 Gauss and out here at the surface it's just half a Gauss. A weak fridge magnet might be 50 Gauss! A strong rare earth magnet might have a field right at the surface of the magnet of 10,000 Gauss (1 Tesla), so in that sense, you can easily buy a magnet with a maximum field strength 400 times stronger than what you might find in Earth's core.",
"But Earth's core is hugely more powerful than a small magnet in a different sense. Because it is so large, the total ",
" in Earth's field is really enormous. Because it's maintained by currents in the core rather than a frozen-in permanent magnetization, it also requires a huge constant supply of power from core motion to keep it going, maybe 4 terawatts. This is comparable to the total amount of electricity produced by humans right now.",
"If you tried to build a bar magnet the size and strength of Earth's core, it would take an enormous amount of energy to magnetize it, and if you tried to build a comparable electromagnet, it would consume a huge amount of power to keep it going.",
"So it depends on what you mean by powerful. You already have magnets in your house that would attract a piece of iron or deflect a charged particle a lot more strongly than Earth's core would, but to magnetize a bar magnet the size of the Earth to make an Earth-size magnetosphere would take an amount of energy probably comparable to the electricity that the whole world uses in a year."
] |
[
"Surely the bar magnet need not be the size of the earth, just the size of the earth's magnetic core? ",
"Or is the mantle also magnetic? "
] |
[
"If gravity is the curve of spacetime and not a force, then why is it considered one of the four fundamental forces?"
] |
[
false
] |
The four fundamental forces: Gravity, Electromagnetism, Strong and Weak. But since Einstein, hasn't gravity been considered just the curve of spacetime and not actually a force? So why is it still a "Force"?
|
[
"Because it's one of the fundamental Things That Affect Stuff. For the reason you describe, scientists sometimes prefer to talk about fundamental ",
"."
] |
[
"The other 3 arent really \"forces\" either, force is a Newtonian formulation of mechanics concept. Its dropped in GR and QM/QFT afaik"
] |
[
"Makes sense, I figured it was that way, but I just wanted to make sure :)"
] |
[
"Why is it that Zirconium and Hafnium always have traces of the other in their samples?"
] |
[
false
] |
I read that Hafnium and Zirconium are twin elements and that samples of zirconium and hafnium almost always have atoms of the other. Why is this?
|
[
"\"The chemical properties of hafnium and zirconium are nearly identical, which makes the two difficult to separate.\" (cf. ",
"http://en.wikipedia.org/wiki/Hafnium",
")"
] |
[
"The chemistries of the two elements are extremely similar. They undergo pretty much the same reactions and even have virtually identical atomic radii and ionisation energies, so a sample of one dug out of the ground is likely to contain some of the other because they \"look\" the same in a chemical sense."
] |
[
"Thanks. are there anything else like this?"
] |
[
"Why do I see RGB when I look away from a projector light?"
] |
[
false
] |
Didn't really know how to phrase the question... If I look at the light from a projector, not directly in front but at an angle, and then look away, for an instant I see the light become 3 distinct colors, all showing at the same time side by side by side, Red Green Blue from left to right. This only lasts for a very brief moment and is an easily repeatable experiment, but I could never understand why it happens. My guess is the old "the eyes shut down when you turn them" thing, or something... any ideas?
|
[
"This is because the DLP projector is rapidly alternating between projection of the red, green, and blue component images. This is called the 'rainbow effect.'",
"Wikipedia has an entry on it"
] |
[
"This is it! Thanks!"
] |
[
"Very common with DLP projectors, other projection technologies don't do that."
] |
[
"How do fish/whales/dolphins/any aquatic life drink?"
] |
[
false
] | null |
[
"Mostly they don't.",
"Marine mammals get a lot of their water from their food. They tend to live on meat, because blood and body fluids are a lot less salty than seawater. ",
"Water is also produced as a byproduct of metabolism. When nutrient molecules are broken down to release energy, the largest byproducts are CO2 and water. (For example, if you eat 100 grams of dry sugar, your body will break it down into 60 grams of water and some CO2.)",
"Marine mammals are also good at conserving the water in their bodies. They have large and efficient kidneys, which create concentrated urine and prevent them from losing too much water. And, because they breathe so slowly, they don't lose as much water in their breath as we do. (An average adult human loses 12 ounces of water per day just by evaporation through the lungs.)",
"It's hard to be completely sure, but we think that if marine mammals get enough fresh food, they never need to drink at all."
] |
[
"Captive dolphins given a freshwater hose to play with drank the water directly and stopped eating. They seem to only eat when motivated by “thirst.”"
] |
[
"I'm in the US, but I'm a nurse, and our healthcare industry uses metric. ",
"So when I talk about medical situations or chemical reactions, I tend to think in metric units. When I talk about human activities that I might have to explain to patients, like how much water to drink, I tend to think in freedom units."
] |
[
"If I have a heavy workout, does the ensuing repair of my muscles burn more calories over the next xx amount of hours as opposed to the regular resting rate? Any information on this?"
] |
[
false
] |
[deleted]
|
[
"Yes, and it is related to the ",
"EPOC effect",
". This is why numerous diets aimed at athletes (Intermittent Fasting, Cheat mode, carb backloading, UD2.0, etc. etc.) have the dieters consuming most of their calories immediately following exercise, to aid in the restorative efforts of the body.",
"In terms of calculating calorie expenditure, the most accurate way of determining your daily caloric needs is by tracking what you eat, to the gram, while tracking body weight and composition. There are too many confounding variables to guarantee that your BMR is 2050 kiloCalories based on height and weight alone."
] |
[
"you're replacing fat with muscle",
"Well, resistance training does tend to decrease the BFP (body fat percentage), and increase muscular mass, but \"replacing fat with muscle\" is a shorthand that will make many people cringe. Perhaps because it suggests that fat is somehow automagically morphed into muscle, which is obviously not the case."
] |
[
"you're replacing fat with muscle",
"Well, resistance training does tend to decrease the BFP (body fat percentage), and increase muscular mass, but \"replacing fat with muscle\" is a shorthand that will make many people cringe. Perhaps because it suggests that fat is somehow automagically morphed into muscle, which is obviously not the case."
] |
[
"What does temperature actually mean?"
] |
[
false
] | null |
[
"Temperature is defined by 1/T = dS/dE.",
"That means that the inverse temperature is the rate of change of entropy with respect to internal energy (at constant volume and number of particles)."
] |
[
"That doesn't explain anything at all.",
"Why do you think that?",
"the units of temperature are not the units of what you said.",
"That's incorrect."
] |
[
"That doesn't explain anything at all. the units of temperature are not the units of what you said. "
] |
[
"What would it feel like to lick a hydrophobic surface?"
] |
[
false
] | null |
[
"I cant speak for super-hydrophobic substances, but there are plenty of hydrophobic surfaces in the home. The exact \"taste\" (you wouldn't really taste much, it's more of a physical sensation you're describing) would depend on the texture. Try the following:",
"The frying pan is probably a better representation. You'd probably lose moisture off of your tongue by diffusion/friction in combination. Whether something tastes dry again depends on the texture! Polystyrene will taste cringe-fully dry (as it is) but the shiny side of an iPhone charger doesn't because it's so slick. "
] |
[
"Those surfaces are understandable because I've had plenty of contact with them. The thought of putting Polystyrene in my mouth makes me feel very uncomfortable!"
] |
[
"Apple products taste like the tears of Chinese sweatshop workers. Licking one engenders feelings of bitterness and regret. ",
"Try licking a Droid charger. Its pure euphoria."
] |
[
"How powerful would a laser need to be to reach the bottom of the ocean?"
] |
[
false
] |
You're in a submersible at the bottom of the marianas trench, a ship above you with a hypothetical laser pointed to the ground in front of you. How strong does this laser need to be to look like a normal laser dot? Alternatively; You have a hypothetical laser at the bottom of the ocean, how strong does it need to be to reach space? Edit: WOAH! This blew up more than I'd expected. Thanks everyone for the anwsers and great discussion
|
[
"Which would then put the bottom of the trench and the light at the same place, along with everything else. Mission accomplished."
] |
[
"Ok so. Seawater absorption is complicated and depends on lots of things (contents of water, wavelength, etc). There's a paper that suggests about 7% per meter under relatively ideal conditions.",
"So multiplying that over the depth of the Mariana trench, you come out with loss such that to get 5 mW of power to the bottom of the trench, you need 1.5 x 10",
" W of power at the surface. Which is too much. I haven't done the math to see just how much of the ocean you'd be vaporizing at that point.",
"EDIT: By \"too much\" I really meant \"more than all the power.\" That amount of power is many many many multiples of the sun's power. It's more than all the possible power.",
"EDIT 2: Please look below for other calculations based on different coefficients of absorption. It makes a huge difference... but only in the sense that the answers range from \"more power than the universe is equivalent to\" to \"only a few hundred times more than the luminous intensity of the entire galaxy\". So in a practical sense the answers are the same, though they are wildly different.",
"EDIT 3: I've gotten some messages about coefficients of absorption. Basically different parts of the ocean absorb water differently. The coefficient of absorption of seawater ranges from about 0.013 to... whatever you want it to be, really. The wavelength matters a whole lot. The 7%/meter answer I got was an average based on white light in real-world pelagic seawater. With real-world seawater your answer ranges from roughly 10",
" watts to 10",
" watts for lasers of optimum sea-water penetration. Get out of that wavelength and the power skyrockets. EVEN SO. Whether you're talking about 10",
" or 10",
" or even a fraction of that... you're talking about unimaginable amounts of power. Power such that the universe cannot supply.",
"If you want to try it yourself, x=e",
" is a supersimplified version of the equation (Lambert's), where x is the input power, a is the coefficient of absorption and d is the depth in meters. That'll give you the number of input units needed to get one output unit. ",
"This paper",
" has a bunch of science and a table on the absorption rates."
] |
[
"It's worse than that, if you ran a laser with that power it for 1 plank time (about 5 *10",
" seconds), you would create a black hole roughly 10",
" times as large as the observable universe. "
] |
[
"Do spacecraft have a way of converting solar energy to propulsion (for use in orbit, not for takeoff)?"
] |
[
false
] |
[deleted]
|
[
"There are solar sails, which are just in their early stages of testing. There's also solar powered ion propulsion, but you still need the ions before you can propel them."
] |
[
"The word attitude here means orientation. A control moment gyroscope is a way of building up angular momentum by spinning a gyroscope and then transferring some of that angular momentum to the spacecraft by rotating the spinning gyroscope. The resulting torque causes a rotation of the craft which changes its orientation in space."
] |
[
"Unmanned satellites usually carry some propellent onboard for stationkeeping. If you run out of that and can't correct the spacecraft's orbit, you basically have to send up a new one.",
"Spacecraft also have gyroscopes or flywheels for adjusting rotation. Those can be solar powered, as they use electric motors. They're only useful for attitude control, and can't be used to move the spacecraft around and adjust orbits. "
] |
[
"Why does it take a few minutes for your eyes to go back to normal after wearing colored glasses? (Ex. bright orange dentist glasses)"
] |
[
false
] | null |
[
"The glasses change the frequency of the light that your eyes are receiving so then your brain realizes there is an excess of, say red and blue due to those being common for 3D movies, your brain may tone down the amount of red and blue frequency's it is \"outputting\" so once you take the glasses off it has to re-adjust, same thing happens when putting them on, you just don't notice it. It is kind of like when listening to loud music for a while everything else seems more quiet. ( P.S. This is a half-way educated guess from a biologist (I think that adds to my credentials))"
] |
[
"like when you have to resurface from diving?"
] |
[
"What do you mean?"
] |
[
"How \"strong\" of a vacuum can you make by pulling a piston out of a cylinder?"
] |
[
false
] |
Asking for my dad - he sent the following explanation of his question, and I couldn't really answer: "Suppose you have a piston at the bottom of a cylinder, which has no opening at the bottom. When you draw the piston out, a vacuum is created. It is easy to imagine that very quickly the pressure difference will become about 14.7 psi (atmospheric pressure) outside, and getting close to zero inside. The question is, what happens next, if you continue to pull the piston? It is relatively easy to overcome 14.7 psi. Is it impossible to pull it any further? Will there be another force holding the piston back? If so, what force? Maybe, you can continue to pull the piston out—after a certain point the pressure differential becomes about 14.7 psi and that’s all you have to overcome for the rest of the stroke. What I’m saying is the pressure difference can’t be more than 14.7 psi, and yet you can continue to increase the volume inside the cylinder. Or maybe the reduction of pressure close to a vacuum inside the cylinder becomes non linear compared to the increase in volume (contrary to Boyle’s Law). Apparently, a perfect vacuum is impossible. But the references I’ve found so far are not consistent on the meaning of “perfect vacuum.” It could mean zero pressure, or it could mean no molecules of air, which might not be the same thing. I think “impossible” probably means it’s difficult to extract every last molecule of gas from a chamber—the fewer they become, the harder it is to capture them."
|
[
"You can see see what happens by looking at the ideal gas law: PV=nRT, where P is pressure, V is volume, n is proportional to the number of gas molecules, R is a constant, and T is temperature. Assuming that the temperature and number of gas molecules stay the same, what you are doing is increasing the volume, which at the same time decreases the pressure. So as you double the volume, the pressure halves. When you quadruple the volume, the pressure reduces to 1/4. So as you can see, when you pull the piston out, you continue to increase the volume, and the pressure will get closer and closer to zero, but will never reach zero."
] |
[
"The \"theory\" part was already answered, but you also get a lot of technical problems. Once your pressure goes low enough (assuming your sealing holds down to these pressures), the walls of your piston will start outgassing because stuff starts boiling. The water on the walls (there's always a few atomic layers of water on basically any surface on earth) will start to evaporate, cracks and impurities in the metal will start to release gases trapped in them, the lubricant of the piston will start sublimating/evaporating etc.",
"This means that you create more sources of molecules and atoms as you decrease the pressure and it will be hard to go below some thresholds.",
"If you build a ultra-high vacuum (UHV) setup for research you have to choose your materials very carefully so that all these effects are reduced. We use copper gaskets to seal our assembly (the flanges have knife edges that cut into the copper to guarantee a tight seal) because rubber is not able to seal to such low pressures. Then you have to bake out the system at 150°C (wrap heating tape around the setup and let the system bake at that temperature for several days) to get rid of all the stuff adsorbed on the inner surfaces so they can get pumped away.",
"There are also usually several types of pumps involved in the process to be able to pump UHV chambers."
] |
[
"The absolute pressure inside the cylinder drops asymptotically to zero as you pull the piston farther. Approaches zero but does not reach zero. In terms of pressure the differences becomes nil.",
"Once you get below a millionth of an atmosphere you're at the verge of the strange world of high vacuum. At that point it's the number of molecules of gas per unit volume that is really important. Think of the vacuum inside the large hadron collider, it zooms particles around a ring that is 16 miles around and they don't hit anything. That's a hard hard vacuum."
] |
[
"Just thought of traveling with and against light, am i on the right page?"
] |
[
false
] |
So your in a spaceship traveling away from earth and at the same time you are looking at your family/world through a telescope. Does this mean that what your looking back at is light rays and that it would appear your family is 'frozen' as in your looking at the same rays so its the same image your seeing not a moving one? So in the same way, when you turn around and start heading back towards earth you're looking through the telescope and those light rays are hitting your eye faster than usual so it would appear as your family is in fast forward mode? I thought about this because my friend once told me if you left earth at light speed for 3 days then turned around and came back, all your friends would be in their old age.
|
[
"you're looking through the telescope and those light rays are hitting your eye faster than usual",
"Here's what happens: you start moving away very fast from the earth, trying to run from the light rays, although classical intuition would tell you that the velocity of the light rays you observe would be smaller, the fact is that you do not change. No matter how fast you go, the speed of light is always the same. And the way that nature finds to make it all consistent is by making time flow at a different rate to you. "
] |
[
"Well, first, you can't ever ",
" move at the speed of light. You can get arbitrarily close, however. So let's assume you're moving at a large fraction of the speed of light.",
"For a more thorough discussion of what your friend was talking about, take a look at ",
"this article on the Twin Paradox",
".",
"When you are moving away from the earth and looking back at it, you will see people moving slower than they see themselves moving, due to the increasing distance between you and the earth. You will also see them redder than they are (due to redshift, which is analogous to the doppler effect, which is why police sirens going by go from high-pitched to low-pitched). I also believe what you see through the telescope will be dimmer than if you were not moving relative to the people you're looking at, but I'm not positive on that.",
"Then, when you turn around and start moving toward the earth, you will see things moving faster, bluer, and (I believe) brighter."
] |
[
"The important part is 'increasing' as opposed to distance. "
] |
[
"Could a massive flood create a lake that remains for thousands of years?"
] |
[
false
] |
Imagine say, a valley in which farmlands were exploited. Would it be possible for a rain-caused flooding to be intense enough to flood the place, and then remain (despite the water cycle leading to evaporation) there pseudo-permanently? Thank you and my apologies if it's a dumb question, this is really far from my scientific field. Edit: Those two answers have provided me with enough information to form a better understanding of the dynamics of it all. Thanks to both of you, you rock!
|
[
"This is similar to what what created the Mediterranean Sea, the event was called the ",
"Zanclean flood",
" and it happened about 5.33 million years ago. Now the Mediterranean sea and the Atlantic are connected--but it wasn't always the case--and the Mediterranean had previously dried up producing 300-1000 m thick salt deposits. The largest deposits occurring within a ",
"10,000 year",
" period. Apologies for the paywall, but this ",
"Nature article",
" titled ",
" Krijgsman et. al. goes over the idea step by step."
] |
[
"Your question has already been answered sufficiently, but I also have an interesting tidbit to contribute if you'd like;",
"http://en.wikipedia.org/wiki/Reelfoot_Lake",
"Reelfoot Lake, located a few hours from where I live, was formed when a large amount of land sunk and flooded following an earthquake. Originally it was just the Mississippi River that flowed through the region, and it's now the largest natural lake in Tennessee!"
] |
[
"Also worth noting that it's only possible here because the Med is below sea level. It was an inundation by sea water that caused it, not a rainfall event."
] |
[
"How do scientists know that our sun is a 2nd generation star?"
] |
[
false
] | null |
[
"Actually, the modern theory is that our sun is at least a third generation star in order to explain the heavier elements.",
"There is a detailed recent explanation of this by a Ph.D. astrophysicist here:",
"https://www.forbes.com/sites/startswithabang/2019/10/26/ask-ethan-how-many-generations-of-stars-formed-before-our-sun-did/"
] |
[
"By its spectrum. First generation stars should only contain helium and hydrogen. The sun has higher metallicity, it contains heavier elements that have to have come from a previous generation. Also, we are here - the nebula from which our solar system coalesced contained the heavy elements to form rocky planets. Again, that could only have come from the remnants of an earlier generation. Lastly, we know how stars evolve, depending on their mass and temperature. The sun is too young to be first generation."
] |
[
":O Thank you!"
] |
[
"Why is fish meat white while meat from mamals is red?"
] |
[
false
] |
Basically just the title. I have been told that fish meat is richer in egg white proteins. But i dont really know what that means. And even the doctor told me that, had no idea if that contributed to the colour.
|
[
"Fish have lower levels of myoglobin which is the protein in muscles responsible for the red colour due to a contained Iron atom. The myoglobin protein is similar to haemoglobin in blood, it carries oxygen. However myoglobin is fixed in the muscle and acts as an oxygen store for when the muscle is under heavy aerobic strain (needs more oxygen). Since fish have their mass supported by the water, they tend to not put such a strain on their muscle aerobically and the myoglobin is needed in lower amounts, although it is more concentrated in the tail due to constant use.",
"\nAdditionally it has nothing to do with egg white protein (ovalbumin)."
] |
[
"On the other hand, some pelagic fishes like tuna pack in a lot more myoglobin, and thus have darker meat."
] |
[
"Salmon is not red, but more of a pink orange. This is due to the presence of a pigment called astaxanthin. It is found naturally in the diet of the salmon. Some fisheries that grow salmon will add the pigment into the diet so that the finished meat is more brightly colored. There is nothing 'wrong' with doing this, but some people consider it unethical to do so."
] |
[
"What are the harms of excessive masturbation?"
] |
[
false
] |
I've been wondering if there is anything unhealthy about it. Can you explain some of the harmful effects and if it is bad, and how much should someone masturbate per week?
|
[
"Before anyone else tries, yes we all know masturbation is hilarious. But you're in AskScience, so let's try and keep the responses on topic, answering the question, and perhaps even with references."
] |
[
"It's possible to give yourself epididymitis, swelling of the epididymis, by excessive masturbation (or excessive intercourse, or especially forceful episodes of either). You could also bruise or rub raw your penis and/or testicles. "
] |
[
"There was a study done, but it ",
"showed no significant correlation",
"."
] |
[
"Can technology similar to the Enchroma glasses for the colorblind be used for people to see infrared or ultraviolet?"
] |
[
false
] | null |
[
"He's not correct. The enchroma glasses work by reducing certain wavelengths so that other ones (the wavelengths a colour blind person has trouble seeing) are more pronounced. This only works for people who can detect those wavelengths, just not well. Since no humans have cones capable of detecting say radio waves, these type of glasses will never work outside of the visual spectrum. To see new types of waves we need glasses like night vision glasses, which take in IR radiation and turn it into visual radiation. ",
"Extra caveat: Humans can actually see low frequency UV radiation, but the lenses in our eyes' block it. In the past, when cataract surgery involved just replacing the natural lens with a glass one, people who received the surgery could see UV radiation, and described it as being somewhat blue. Claude Monet was one of the people who received this surgery, which might explain the colour pallet he used."
] |
[
"Those glasses don't let you see anything you can't already see, they only block certain wavelenghts.",
"In many color-blind people, the red-sensitive cones and the green-sensitive cones have overlapping sensitivity zones. Anything in the overlap will trigger both cones. The glasses simply block all wavelenghts that would trigger both.",
"There are no cones that see infrared or ultraviolet in normal humans, so this method can't help there.",
"What you would have to do is shift their wavelenght into the visual spectrum, in which case it would look the same color as whatever wavelenght it's shifted to."
] |
[
"Thanks a lot, that sounds awesome! I hope that we can someday have even more colorful art than we do today."
] |
[
"Do string theorists know or have an idea of what the strings in string theory are made of?"
] |
[
false
] |
Just a curiosity of mine. I'm watching a documentary on String Theory by NOVA and it's really interesting.
|
[
"In string theory, the concept of \"being made of\" or of which object is truly the fundamental building block is ill-defined. Strings, along with other objects, are just things that can exist in the theory. Instead of arguing for this abstractly I'll just make one example out of a billion possible ones, so you'll get an idea of how things tend to work in strings.",
"In type IIB string theory, when the string coupling strength is small, you do find the eponymous strings as objects you can have in the theory. It could be easy to convince yourself that these are fundamental and hence they are called F-string, F for fundamental. There are however also heavy objects, the D-branes, which however are not to be posited in addition to strings, but are actually found to be bound states of strings. Anyone would agree that means D-branes are ",
" of F-strings. This includes D1-branes aka D-strings.",
"Now imagine the string interaction is made stronger and stronger. It would be hard to say what happens, since in general strong coupling means untreatable, but we have a powerful tool: we know IIB is self-S-dual, which means if you do the following to IIB:",
"Then you obtain the same theory. All situations in IIB can be remapped to equivalent but different-looking situations by this S-duality. And so strong coupling becomes weak coupling, but with the D-strings in the role of the F-strings and viceversa. So now the D-strings are \"fundamental\" and the F-strings are \"made of\" D-strings. Which makes no sense unless you let go of the notion that there is always a hierarchy of emergence and that it is always possible to separate the bricks from the house. Emergence is relative in string theory.",
"This fuzziness extends also to the dichotomy between \"background\" (spacetime) and \"foreground\" (strings and other stuff moving on it). Flat space with a particular bunch of strings/branes on it can be completely equivalent to a curved empty spacetime for example. So there is no true separation also between spacetime and its content; they are only two manifestations of the same \"thing\".",
"I am not excluding however that there exists a fundamental, microscopic \"closed-form\" description of string theory, and AdS/CFT seems on the right path to provide it. But this kind of description would provide a ",
" object (e.g.: a holographic dual theory) from which in some limits there would emerge something resembling a spacetime and strings and branes (all at the same time necessarily). You could say strings are made of ",
", but it would be like saying pacman is made of transistors."
] |
[
"As someone with an interest in string theory, but without the computational chops for something like Polchinski just yet, I love your posts like this one. You can glean some of this stuff from texts without being able to work through the computations, but it's nice to have something that is condensed and somewhere between \"complete treatment\" and \"pop-sci level.\""
] |
[
"Just to add to ",
"/u/rantonels",
" excellent answer, even in non-string theory \"made of\" is a little bit of a nebulous statement. In the Standard Model, an electron, for example, is basically an excitation of \"the electron field\". It's a concrete bundle of energy deposited in a special type of field (a quantum/operator field). If one asked \"what is the electron field made of\", it'd be similarly unsatisfying. On one hand, one can simply say \"as far as we know (minus string theory), that's the end of the road and it just \"is\" until we find that it has some finer structure\", but then on the other hand, even if we do find it has some finer structure then one can just repeat the question: what is that finer structure \"made of\"? It never ends, it's turtles all the way down.",
"So from the perspective of the Standard Model, we are in a universe and our universe is \"permeated\" by this exotic thing that is an electron field."
] |
[
"Does the size (weight, height) of the surrogate mother affect the adult size of the offspring?"
] |
[
false
] | null |
[
"Probably genetics it’s the most important thing here, but you could probably not discard ambient effects, in this case, the surrogate mother “ambient”. I don’t really know if this have been extensively studied, but a surrogate mother may contribute with hormones, factors or other active molecules that may at the end affect the size of the offspring.\nIn genetics there is a law, that says that the phenotype is the sum of the genotype + the ambient. Probably this is one of such cases."
] |
[
"I read some (epigenetics research) a while back that the surrogate mother's body can affect the expression of the baby’s genes. The research was discussed, environmental affects the way the genes are expressed.",
"Researchers have also found occurrences of fetal microchimerism (traces of Male DNA) in their mother's brain. There is also most likely traces of female DNA from their daughters too, just harder to find. I would assume that that fetal microchimerism would occur with any type of pregnancy."
] |
[
"Not at all unless the surrogate is using her own eggs which is quite rare now in the world of surrogacy. The surrogate has absolutely no genetic influence on the baby.\nThis is what my reproductive endocrinologist told me when I was asking questions about it at one of my appointments (im a surrogate)"
] |
[
"Can I dissolve as much sugar in sea water as I can in distilled water? Why or why not?"
] |
[
false
] |
Asked fancier: does the concentration of a given solute affect the solvents saturation point for a different solute? EDIT: So there seems to be two camps, one that points out (validly) that theory and logic dictates that more salt=less sugar able to dissolve. The other camp says that's nice but not how it works in reality.
|
[
"Sugar and salt do not share a ",
"common ion",
".",
"One will not directly interfere with the other's equilibrium in water. However, both will compete for water.",
"Competition allows you to ",
"salt out",
" some substances. Check out this ",
"video demonstration of salting out",
" where a solution of methanol and water is separated by giving the water molecules something else to stick to. It will be less extreme than the video, but you will be able to dissolve less sugar in seawater than in distilled."
] |
[
"To explain the downvotes - salting out is a proper term for the phenomenon described above"
] |
[
"To explain the downvotes - salting out is a proper term for the phenomenon described above"
] |
[
"What theories do we have for how Pluto came to have methane?"
] |
[
false
] |
In particular, it seems like there are limited processes for abiotic methane formation, e.g. serpentinization. Is this considered a likely scenario?
|
[
"Exactly what Tiiba said. Methane is the simplest molecule with carbon in it. Ammonia, the simplest with nitrogen. Etc. Since hydrogen is by far the most abundant element, it's clear why we see CH4, NH3, PH3, OH2, and HCl whenever we have an abundance of C, N, P, O, or Cl.",
"What I think is really interesting is that far more complex molecules can come about in interstellar space, including the bright orange hydrocarbon ",
"tetracene",
" with an equally interesting ",
"chemical structure",
"."
] |
[
"Why does this say there's one comment, yet not show it?",
"I thought methane is pretty expected when you have carbon and hydrogen. Oxygen makes water, nitrogen - ammonia, phosphorus - phosphine. All this stuff came from a star, and when it cooled down enough to react with hydrogen, it did.",
"There's methane on Titan, all four gas giants, some brown dwarfs, and in interstellar space.",
"EDIT: I actually didn't know what serpentinization is. I found it in reference to methane on Mars. I guess the problem with Mars is that it's warm enough to lose its original methane (and a lot of water), but on Pluto, methane is rock.\nEDIT: Now it says 6 replies, but I only see this and ",
"/u/IanTheChemist"
] |
[
"Thanks for the response. Like my response to Tiiba, it's interesting to me that this can happen. It seems unlikely to me that that would occur because it is energetically favorable. What is the source of energy that results in these molecules forming? Radiation from stars?"
] |
[
"Time cloak: how does it work?"
] |
[
false
] |
I just saw this article ( ) on the front page. In terms that someone who understands at least the basic principles of relativity, quantum mechanics, etc. can understand, how does this work?
|
[
"It's a fascinatingly simple idea. ",
"A light pulse has a certain bandwidth (i.e. it contains a bunch of different frequencies), which is larger the shorter the pulse is. ",
"In this time-cloaking experiment, they \"pull apart\" this light pulse by accelerating the blue part of the spectrum and slowing down the red part of it, creating a spectral hole in the middle. This can be achieved by cleverly engineering an optical material's dispersion curve, i.e. the frequency-dependent refractive index experienced by the light pulse. ",
"Now that you have that spectral hole, you can put an event inside which is now \"cloaked\" (not really, but ok). Put the pulse together afterwards by reversing the initial dispersion and it will now look like that event in the middle never happened, the light pulse comes out exactly like it went in.",
"If you want more technical details, let me know."
] |
[
"No, not really. Optical manipulation ",
" time manipulation whenever light pulses are used to measure time. In the current example, you can put a dispersive event in the middle of that spectral gap and still you'd never find out at the receiver. The event was cloaked in time. The researchers also provide use cases for this technique, eavesdropping, for example."
] |
[
"And what do you think is the principle behind the atomic clock? Yes, that's right, a frequency—optical, in the newest and most accurate clocks—measurement.",
"Also, temporal measurement in the context of this experiment can refer to a stable time basis, which can be established via the clock rate of an optical transmission."
] |
[
"How do veins and arteries bend/twist without blood getting stopped or clogged?"
] |
[
false
] |
When a water hose is bent far enough, the flow of water through it is choked and very little water comes out. When we bend our arms or move our legs, shouldnt the same thing happen?
|
[
"Arteries are sturdier than you think. Thick walled and flexible, arteries can withstand a good amount of compression. As per veins, there is enough collateral circulation that if one gets compressed, the rest of the venous system can compensate."
] |
[
"you are right no a point. But cutting of does happen and is a problem, especially in disabled and knocked out people."
] |
[
"That's not what happens when a body part goes to sleep.",
"That's usually caused by nerve compression."
] |
[
"Will Mt. McKinley surpass Mt. Everest some day?"
] |
[
false
] |
I heard that Mt McKinley is still growing. Will it be taller than Everest some day?
|
[
"Everest is currently growing 1/3 of an inch a year, ",
"source",
". I could not find the rate that McKinley is rising but I did find that the pacific plate is moving northward into Alaska at about 2 inches a year, ",
"souce",
". The source on Everest says that Everest is moving about 5 inches a year. Assuming the current state of plate tectonics does not change and both mountains erode at the same rate, I would say that Everest will remain higher. This is an assumption based on the fact that the Indian Plate is moving at a faster rate than the pacific plate and that a faster moving plate causes mass to be pushed upward at a faster rate. "
] |
[
"This is all fair information to point out, but as a side note, geologically distinguishing Mt. Everest from the plateau it is sitting on is pretty arbitrary. While it makes more sense for climbers/hikers/urban planners/etc to consider the height of the mountain from the surrounding terrain, when it comes to the geology Mt. Everest is most certainly taller. So it's not quite the same as comparing a person who is 72cm tall to someone 70cm tall.",
"Still, it's worth clarifying the definition isn't clear-cut."
] |
[
"I think the down votes are because Olympus mons isn't on earth."
] |
[
"Has flicker noise been explained yet?"
] |
[
false
] |
Either in electronics/instruments in particular or in general.
|
[
"It's not always from the same thing. The interesting thing about 1/f noise is that there are a lot of different physical phenomena that can produce it. Mathematically this is the case because a collection of two level fluctuators with a log/normal distribution of switching times gives a 1/f spectrum. The log/normal distribution occurs naturally because switching times usually depend on the exponent of some physical parameter.",
"This somewhat general mathematical/physical situation is probably why 1/f noise is so universal.",
"To answer your question more directly, 1/f noise has been explained in some places and not in others. I'm most familiar with a particular flavor of magnetic 1/f noise that occurs in superconducting metals. In those systems, we've tracked the 1/f noise to some kind of paramagnetic impurity on the metal surfaces. The exact mechanism isn't known yet."
] |
[
"Can you explain your question a bit more? ",
"Noise in electronics",
") is a fact of life, it can be caused by a number of things - thermal nose due to non zero temperature, inteference with the real world.",
"Think about what temperature means classically for a group of atoms in a wire - it means they are jiggling around at random. A current can be thought of classically as electrons going through a matrix of atoms. The atoms random movement due to their temperature will occasionally impede electrons' movement, and at a random rate."
] |
[
"Alright. Thanks for the update. I hadn't heard the mathematical argument yet, so I'll ponder that for a while. "
] |
[
"Is “long covid” the same or similar to other post-viral syndromes?"
] |
[
false
] |
I have been very interested in learning about long haul covid. To my understanding other viruses such as malaria can cause long term symptoms like fatigue and intense pain. A lot of these stories sound similar to the experiences of long COVID patients. Could past research into post-viral syndrome give us clues into how we might treat long haulers? (I am a bit unsure if this is the wrong subreddit to ask this question. Mods feel free to remove if it’s not the right place.)
|
[
"This is hard to answer because long COVID isn't clearly defined.",
"There is a post-ICU syndrome that can affect people who get severely ill. They can have permanent functional defects in neurocognitive and cardiopulmonary function. Some are clearly understood, some are not.",
"Some component of long COVID is probably just post-ICU syndrome. It's hard to tell, since this phenomenon was only really starting to get serious study before COVID hit. However, many of the people who present with symptoms of long COVID have never been hospitalized, let alone critically ill. My colleague runs out post-ICU clinic, and the majority of her long COVID patients were never hospitalized.",
"There is a possibility that this may be selection bias, as people who get post-viral syndrome from a cold may not recognize the association. Some manifestations can happen decades later, like rheumatic heart disease from strep throat."
] |
[
"\"check out treatment of long term covid with CBD oil. Seems there are some promising results\"",
"Just to be clear there are currently ",
"no proven treatments",
"02798-7/fulltext) for long COVID. There are some ",
"ongoing trials",
" evaluating CBD oil but they are far from conclusive. However, doctors can treat the symptoms of long COVID and vaccination prior to infection can reduce the incidence of it.",
"https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)02798-7/fulltext",
"02798-7/fulltext)"
] |
[
"\"check out treatment of long term covid with CBD oil. Seems there are some promising results\"",
"Just to be clear there are currently ",
"no proven treatments",
"02798-7/fulltext) for long COVID. There are some ",
"ongoing trials",
" evaluating CBD oil but they are far from conclusive. However, doctors can treat the symptoms of long COVID and vaccination prior to infection can reduce the incidence of it.",
"https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)02798-7/fulltext",
"02798-7/fulltext)"
] |
[
"If i had 1 mol of a dollar, and was able to spend 1 billion every second, how many years would it take to spend it all?"
] |
[
false
] | null |
[
"avagadro's number / number of seconds in a year / 1 billion",
"19 million years",
"Bonus: ",
"http://en.wikipedia.org/wiki/Miocene"
] |
[
"6.022x10",
" dollars * (1 second / 1 billion dollars) * (1 day / 86400 seconds) * (1 year / 364.25 days) = 19.13 million years"
] |
[
"whoops",
"fixed"
] |
[
"What conditions are necessary for protons to decay?"
] |
[
false
] |
[deleted]
|
[
"Protons are made up of 3 quarks (2 up quarks and 1 down quark).",
"how/why these seemingly very stable particles would undergo such a process.",
"If you're asking what triggers the decay, it's a completely spontaneous, random event and there is no way of knowing when a proton will decay. It's worth it to mention that no one has ever observed a proton decay so they are considered extremely stable particles."
] |
[
"Is it possible that protons simply cannot decay? Or is that impossible from a quantum mechanical point of view?"
] |
[
"Certainly the latter.",
"Proton decay isn't very well understood, there are a number of ways that protons are theorised to decay, for example they could break down into a Positron and a Pion (the pion would quickly decay into 2 photons), this process has a predicted half-life of something like 10",
" years.",
"http://hyperphysics.phy-astr.gsu.edu/hbase/particles/proton.html",
"Radioactive decay in general is considered to be completely random, everything has a probability of decaying every second. It isn't an induced process."
] |
[
"Would plants still be green for photosynthesis if we had a different kind of star for our sun?"
] |
[
false
] |
Let's say we had a blue dwarf, neutrino, or red giant instead of Old Sol. Assuming we were still in a comparable habitable zone and life developed along similar lines, would our plants still be mainly green?
|
[
"I'm surprised no one has mentioned algae yet. If you take a look at the different types of algae (red, brown, green) you will see that they occupy different trophic zones in the ocean. This means they live at different depths. Green algae are near the surface where red light is in abundance. As you go deeper, red light is still present in lesser quantity but green light becomes more important, so then you get brown algae to take advantage of red and green light. Go even deeper, and green light becomes the most abundant, and red is almost entirely gone; this is where you find red algae. ",
"It's also worth mentioning that chlorophyll has both a light spectrum it can absorb, and a smaller spectrum it can actually use for photosynthesis. So while red algae might be able to absorb some red light, it's not like the algae can produce anything with it.",
"I hope this answers your question in a roundabout way."
] |
[
"Electromagnetic Radiation is electromagnetic radiation, no matter its source. While the exact emission curves of different stars can vary, and a yellow star might put out more yellow light than a blue star, at the end of the day, plants derive their energy from a fairly wide range of colours of light, 400-700 nm ish, which covers reds all the way to blues. So green chloroplasts would still function well, regardless of the star, assuming all other variables are kept constant - and that's a big assumption. Every star has a different brightness, different luminosity, different gravitational influence, different habitable zone, etc. etc. But assuming you swap like-for-like, and are essentially JUST changing the colour of our star, then what I've written above applies. ",
"Now, if you're talking about evolutionary pressures, that's completely different. There's no real way for anyone here to make anything more than a random guess as to how life would have evolved if you changed something as fundamental as our star. Maybe plants would be a slightly different colour of green, better-optimised to absorb the bluer light of their blue star, compared to our plants and their yellow star. Or maybe there would be no terrestrial life at all because their star is more magnetically active than ours, and hammers their planet with too many high-energy particles and uv radiation for life to survive. It's hard to guess."
] |
[
"I feel like I've seen a paper on fungus creating blackcholoroplasts to absorb nuclear radiation? Couldn't that develop in plant life on a planet with a weaker magnetic field?",
"found it: ",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2677413/",
"and it shows that a rise in the melanin fungi rose when earth's magnetic field hit magnetic zero at one point"
] |
[
"How do missiles that lock onto vehicles work?"
] |
[
false
] |
[deleted]
|
[
"There're multiple guidance methods.",
"Beam-riding is the simplest. A narrow signal is bounced off the target, the missile seeker points the missile at the reflection. Fine for slow-moving or stationary targets, not so great for air-to-air combat when the launcher and the target are both moving at incredibly high speed. The russians still use this for modern anti-tank missiles, in a rather brilliant system, where the seeker is actually located at the rear of the missile, and steers the missile so that the beam is centered in the seeker, making it immune to almost any kind of jamming/countermeasure, whereas seekers that follow the reflection can be jammed by vehicles which deploy smoke or aerosol clouds when they detect the guidance beam, or outright blind the seeker(like the russian Shtora system)",
"An infrared-homing missile is essentially a rocket with steering fins and an infrared camera of varying complexity. The earliest seekers could only tell whether something really hot was there or not, and would chase the hottest thing visible to the seeker, be it a jet exhaust, a flare or the sun. These early missiles were 'rear-aspect'- they could only be fired from behind a target, because they were only sensitive enough to see something like a jet exhaust, and were easily decoyed by using heat sources like flares, or simply flying towards and then away from the sun. Modern seekers, like on the Israeli Python missile, have actual CCD imaging infrared cameras, which visually identify the target as an object, rather a point-source of infrared radiation. ",
"Then there're the two types of radar guidance, active and semi-active. Basically the same concepts apply, except using bounced radar signals rather than infrared. Semi-Active listens to the bounces from the launching aircraft's radar, Active has a radar in the missile itself. ",
"Source- I'm a goddamned nerd."
] |
[
"Depends on the guidance the missile uses.",
"An infra-red guided missile is said to have locked on when it gets a strong enough heat source to detect and track the target.",
"An active radar guided missile locks on when it constantly moves a radar beam over the target to track it, rather than just scans over it every few seconds.",
"A semi active radar guided missile locks on when it detects enough reflected radar energy from the target to follow it."
] |
[
"thought of a better way to explain it. Beam riding is like if you were in a pitch-black forest and had a missile that fired at whatever you shine a laser-pointer at. You have to continuously track the target with the pointer until it's hit, and you can't use the laser pointer to illuminate your surroundings. SARH missiles are like if you have a wide-angle floodlight, and the missiles can home in on anything that reflects the light. "
] |
[
"Do we know why people have specific fetishes?"
] |
[
false
] |
[deleted]
|
[
"Ignore tag this isn't my area of expertise.",
"The short answer is 'lots of different reasons.'",
"The longer answer is, we don't exactly know but we suspect that many fetishes are a combination of imprinting, classical conditioning, and generalization. Essentially an early or salient presentation of an object during a sexual experience leads to a strong and persistent association with that object or thing. Further presentation strengthens the association. There is some thought there might also be some window in adolescence for this, but this is speculative. Some people suspect neural cross-talk including the classic example of the foot and genitals being close in the sensory homonculus. (Interestingly, I find a lot of mention of this in the news but I can't find a good clean literature source that he said it, however the location on the genitals on the sensory homonculus is accurate)",
"Some papers to support this: A neutral odor may become a sexual incentive through classical conditioning in male rats and An animal model of fetishism.",
"There are almost certainly other elements/causes of fetishes. This model just happens to be the easiest to replicate in animals and study."
] |
[
"I have a very, very broad range of fetishes, and can't think of anything in my childhood that's related to pretty much any one of them. So there has to be more than that."
] |
[
"I suspect the adolescence thing is probably limited to very specific instances/linked to older theories of sexuality. I think (sadly it was from a talk I heard and I can't find a lit ref) there might be merit to the idea that things present at first sexual experience or sexual encounter are more likely to become fetishes. However, the human brain is far more complex than any animal model will reflect, especially in a highly social behavior like sexuality."
] |
[
"Do children hold an equal amount of DNA from both parents? Is it as perfect 50/50 split?"
] |
[
false
] | null |
[
"This answer is incorrect, for a couple reasons. First, the Y chromosome is much smaller than the X chromosome. Second, mitocondrial DNA is passed on (almost always) only from the mother; a human embryo has no mtDNA from the sperm (hence the term \"mitochondrial Eve\"). Third, not all chromosomes are exactly the same size. One parent's chromosome may have additional repeated sequences missing from the other's chromosome.",
"There are probably other factors that don't spring to mind right now."
] |
[
"In rare cases you could have extra chromosomes, so you get two copies of a chromosome from one or both parents. That's definitely not the norm, though.",
"Would the gut fauna that's passed on through the mother's breast milk count? That's not a constant but it definitely has heritable properties."
] |
[
"The answer is yes, they do hold an equal amount of DNA from both parents. This is because both parents will each give the child 23 chromosomes, forming the 46 chromosomes the DNA consists of in a cell of a human (pairs of two, one chromosome from the mom and one from the dad). Gender doesn't change the amount of DNA that is passed on from an individual parent."
] |
[
"Can IV medications be given PO?"
] |
[
false
] |
At the hospital I work at, it is a common practice to reconstitute a gram of vancomycin and then unit dose it into oral cups to be given to the patient by mouth. I've been told we used to use vanco that was intended for oral use but then switched to just using the IV vials. Why can we do this if the vials say "for intravenous use only"? I know it is the same drug, but I would think that the IV form wouldn't be as effective since it is not expecting to have to deal with stomach acid. Can other IV drugs be given PO also? Not sure if it matters but the usually prescribed po dosage is 250-500mg 2-3 times a day.
|
[
"Vancomycin is a drug that does not cross the GI tract very well. Therefore, vancomycin given orally does not get into the bloodstream to any great extent, and vancomycin given IV does not get into the gut very well. We primarily use oral vancomycin to treat c. difficile infections (c. difficile lives in the gut, and IV vancomycin is not effective). Pill forms of vancomycin exist, but the company that makes them charges a lot of money for them. Therefore it is common practice to give the IV formulation, which is cheap, orally. It says \"for intravenous use\" most likely because it isn't FDA approved for oral use. "
] |
[
"Other IV formulations of drugs can be given through the oral route. I just finished a rotation at a hospital pharmacy and I can think of at least one example. We would dilute IV morphine sulfate with sterile water for injection to yield a concentration of 0.4mg per 1ml for oral use in Neonates. ",
"There are other drugs whose commercially prepared oral liquid formulations contain alcohol and/or paraben-derived preservatives. These products are harmful to babies and newborns. In my compounding rotation, I made preservative-free, alcohol-free, liquid formulations of these drugs, sometimes using drugs intended for injection. Acyclovir comes to mind. "
] |
[
"Pharmacist here. Vancomycin is a bit of a special case because of its absurdly poor oral bioavailability. It's given PO so that it works locally (in the gut) on infections like C. dificile. You won't be getting peaks and troughs with this because it's not really making it into the bloodstream. It's dosed two to three times a day (even up to four times a day) so that the gut bacteria get exposed to the medication as much as possible. It's difficult to ascertain how much of the medication is actually reaching the bacteria though. "
] |
[
"In HBO's Chernobyl, it is shown multiple times that merely looking into the exposed nuclear reactor core was particularly dangerous, even compared to just being close enough to do so. Why?"
] |
[
false
] | null |
[
"Are you referring to the scene where someone is looking over the edge of the hole in the roof, directly at the exposed core?"
] |
[
"Yes"
] |
[
"Depending on what exactly they’re looking over (the material and it’s thickness) it may or may not be providing good shielding against against neutrons and gamma rays. Also if the burning core is exposed and there’s a plume of contaminated smoke, if you’re standing directly over the hole, you’re probably getting more exposure from that, especially if you’re breathing it in.",
"So it’s plausible that the dose rate does increase significantly when you have a direct line-of-sight in that scenario, but it depends on the specifics."
] |
[
"Why does cortisol's effect in the human body take longer than adrenaline (epinephrine)?"
] |
[
false
] |
Is it due to the fact that cortisol induces change via gene expression, which takes a lot longer than adrenaline's G-protein coupled cascade is it due to the fact that cortisol has to be made from scratch in the nucleus because of it's lipid character while adrenaline can be stored in vesicles and immediately released? Much thanks! I find this a very vexing matter.
|
[
"The mechanism of action of steroids is much more important than is the way they are synthesized. We know this experimentally because you can take synthesis out of the equation by injecting the hormones as a medicine. An epinephrine shot has an immediate effect on the patient receiving it, but a dose of a glucocorticoid is much slower to act (makes a difference over hours). ",
"Steroid synthesis starts in the mitochondria and is completed in the smooth endoplasmic reticulum. The rate-limiting step in synthesis is transport of cholesterol (the starting molecule for steroid synthesis) into the mitochondria, which is done by a steroid regulatory protein (StAR). Steroids then have their effect by binding nuclear receptors in target cells, which activates transcription, which leads to translation, and finally new proteins are made that can start exerting the many downstream effects of the steroid hormone. ",
"Epinephrine, as you state, is synthesized in advance and released on demand. It exerts its effect by binding G-protein coupled receptors that amplify the signal by making a large number of secondary signaling molecules inside the target cell. The final downstream effects of epinephrine occur when this signaling cascade changes the way pre-existing proteins behave. For example, increasing the concentration of calcium in the cytoplasm of vascular smooth muscle cells or cardiac pacemaker cells will cause vasoconstriction and increased heart rate respectively. "
] |
[
"Thank you very much for such an in-depth answer to my question! I genuinely appreciate the time you put into this, I now fully understand the difference in speed. I had a Metabolism exam today, which is why I was intrigued by the matter. Again, much thanks! "
] |
[
"What class?"
] |
[
"Do humans desire to mate more than any other creature on Earth? If so, why?"
] |
[
false
] |
[deleted]
|
[
"Bonobos have even more sex for fun than humans."
] |
[
"It's difficult to define as you are throwing around words like \"desire\", \"pleasure\" and \"feeling\" which are all solely human constructs. To answer your question you would have to know how other animals feel which isn't possible.",
"I think the closest you can come to an answer is in the study of masturbation and homosexuality among other species. The most common example is homosexual dolphins.",
"When you consider lower life forms that are doing it because it is a reflex (some of which would have sex with a mirror showing their own reflection) it is impossible to determine if they receive \"pleasure\" or just do it because their genes tell them to."
] |
[
"Thank you very much for your input and I also learned from reading your reply that there are animals that engage in homosexuality, very interesting. From my understanding humans are the only species that engage in sexual activity while using birth control so it led me to wonder if we're the only species that values sex for the pleasurable feeling rather reproduction. As you mentioned \"pleasure\" and \"desire\" are human constructs and that's something I hadn't considered."
] |
[
"What is happening when a chip goes stale?"
] |
[
false
] | null |
[
"Mostly it is just atmospheric humidity entering the food, making it lose it's crunch. The water activity in a crisp chip is very low, so left exposed to the environment, it will come in contact with water in the air and lose it at a much lower, not even comparable rate. Theoretically this would happen until equilibrium is reached. The starches will then soften when exposed to water, making the chip more chewy. The opposite effect is seen in very turgid fruits and vegetables. Because their water activity is so high, they slowly lose water to the atmosphere. The equilibrium is in the opposite direction, although in this case, the water is actually helping the plant cells to stay \"crisp\" because of the water pressure against the cell walls. As water slowly escapes, they lose pressure and become limp. To test this out, you can leave a cucumber in a very humid, sealed container with some wet paper towels and compare it to a cucumber left on the counter for two days to see the difference. Also, you can try to re-crisp your chips and crackers by throwing them in the oven for a few minutes. "
] |
[
"This is why moist foods like bread get hard when they go stale while dry foods like chips get soft when they go stale. Both foods are tending towards their equilibrium water composition. "
] |
[
"\"On the tub\"?"
] |
[
"What is the material state of jelly?"
] |
[
false
] |
Title says it all really.
|
[
"It's a colloidal gel: a solid dispersed into a liquid medium."
] |
[
"Specifically, a pectin gel in the US and a gelatin gel in the UK."
] |
[
"Are the words gel and jelly related etymologically?"
] |
[
"What are the environmental cons of using hydrogen fuel for transportation?"
] |
[
false
] |
My mother is curious to know what the negative effects to the environment would be if all cars switched to using hydrogen fuel.
|
[
"Electrolysis needs energy, so the impact of hydrogen cars would be whatever impact their fuel source has. Luckily, the production process needs electricity, and that can come from any kind of power plant, including solar"
] |
[
"But the excess water emitted from the burning of hydrogen fuel wouldn't impact the environment in any way?"
] |
[
"The cheapest source of hydrogen comes from extraction of natural gas, the cell in the car requires platinum, the world supply of platinum would not be sufficient to change the American fleet to fuel cells. There is no infrastructure for transporting the hydrogen to the cars. Bottom line there are better solutions and this would indirectly slow down the progress of better alternatives."
] |
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