title
list | over_18
list | post_content
stringlengths 0
9.37k
⌀ | C1
list | C2
list | C3
list |
|---|---|---|---|---|---|
[
"Has the angle of the rising sun in relation to due East altered at any point on the Earth in the past few years?"
] |
[
false
] |
More details here I know the surrounding assumptions are not your bag and you are skeptical of them but I was wondering if someone could confirm the empirical data and, hopefully provide a scientific hypothesis as to why this has occured (if it has). Thanks in advance guys. :-)
|
[
"Ok, you are simply refusing to answer any questions about your process or accept any suggested answer. You very obviously are an anti-science psuedo-intellectual. If you were interested in science you would take any criticism of your process, adapt your experiment to correct for that problem and improve the validity of your measurements. Of course, I am also interested in other people that have the proper instruments to accurately measure this, because it would be pretty incredible if it were true.",
"If you want people in a scientific community to even begin to take you seriously you have to tell us some things, What instruments did you use to measure the declination and what was your process in taking that measurement? Where precisely did you take that measurement and what is the landscape of the horizon? Did you get the \"base\" declination for the broad designation of Chicago or did you determine and input your exact long/lat? At what point during the sunset was your measurement taken, did you measure the exact moment the sun crossed the horizon or some other time? How is the base measurement taken, and did you use the same process? If you repeat this expiriment every day for at least a week do you get consistant results?",
"These are just the questions I have off the top of my head, and I know jack shit about astronomy except for 1 intro class in university that I barely passed. I am certain that those experts out there in the scientific community would come up with many more. You are making an extrordinary claim, 1-2 degrees is one thing, but the amount you are measuring is extrordinary. In all forms of science extrodinary claims require extrodinary evidence. Post your process and let it be open for examination and comment and perhaps your measurements are correct and you have discovered something amazing."
] |
[
"Ok, you are simply refusing to answer any questions about your process or accept any suggested answer. You very obviously are an anti-science psuedo-intellectual. If you were interested in science you would take any criticism of your process, adapt your experiment to correct for that problem and improve the validity of your measurements. Of course, I am also interested in other people that have the proper instruments to accurately measure this, because it would be pretty incredible if it were true.",
"If you want people in a scientific community to even begin to take you seriously you have to tell us some things, What instruments did you use to measure the declination and what was your process in taking that measurement? Where precisely did you take that measurement and what is the landscape of the horizon? Did you get the \"base\" declination for the broad designation of Chicago or did you determine and input your exact long/lat? At what point during the sunset was your measurement taken, did you measure the exact moment the sun crossed the horizon or some other time? How is the base measurement taken, and did you use the same process? If you repeat this expiriment every day for at least a week do you get consistant results?",
"These are just the questions I have off the top of my head, and I know jack shit about astronomy except for 1 intro class in university that I barely passed. I am certain that those experts out there in the scientific community would come up with many more. You are making an extrordinary claim, 1-2 degrees is one thing, but the amount you are measuring is extrordinary. In all forms of science extrodinary claims require extrodinary evidence. Post your process and let it be open for examination and comment and perhaps your measurements are correct and you have discovered something amazing."
] |
[
"Magnetic North moves around over time. Over the last decade or so it has been moving very rapidly, about 40 miles per year. This will not affect position of the sunrise, but it will affect your measurement when taken with a magnetic compass. ",
"(Relevant link.",
")"
] |
[
"Is there a phrase to describe the back-and-forth evolutionary process between organisms, e.g. predator and prey?"
] |
[
false
] |
I'm thinking of things like the prey evolves a particular defense, the predator evolves a counter to that defense, and so on. I seem to remember this sort of thing from high school biology, or just reading about it. Is there even a term of art for it? Or is there a good phrase to describe the constant process each year of developing a new influenza vaccine to (artificially) account for the mutation/change/natural selection that was a result of the previous year?
|
[
"coevolution"
] |
[
"Red Queen's hypothesis",
", in reference to the quotation by the Red Queen: \"It takes all the running you can do, to keep in the same place.\""
] |
[
"Evolutionary arms race"
] |
[
"What happened to all the Aquatic Dinosaurs?"
] |
[
false
] |
I'm curious as to why the aquatic dinosaurs disappeared. I know there are a lot of theories and hypothesis as to why the land dinosaurs were wiped out, but it seems that sea life has been left out of this discussion. For example, the asteroid. How did that affect the ocean?
|
[
"First off, the obligatory \"Giant marine reptiles were not technically dinosaurs\" (some were actually pretty closely related to certain lizard groups, others were in completely different groups, none were dinosaurs proper)",
"Second: These marine reptiles tended to be large, active top predators. Life is always a bit more precarious for top predators. Blot out the sun for a few years and you'd see phytoplankton populations crash, leading to a crash in small fish. This would decrease populations of the larger fish that top predators eat. Lacking food, many would starve. And top predators usually have pretty low populations because their food supply is limited even during the best of times, and each individual needs to eat a lot. Fewer individuals mean lower chance of survival."
] |
[
"Sharks saw a 20% species reduction. That says nothing for the populations though, which may have seen much larger reductions. And, as you point out - there are many small and deepwater species."
] |
[
"Also, it is hypothesized that the meteor hit organic rich sediments which released large amounts of SO2 and CO2 into the atmosphere. SO2 keeps solar radiation from entering the atmosphere, thus cooling the earth rapidly. CO2 lets solar radiation into the atmosphere, but does not let it out. This causes warming. This rapid cooling and then warming affect would have killed many organisms on land and it water. ",
"In addition (not sure if it was the SO2/CO2 or another chemical) chemicals released into the atmosphere created acid rain, which acidified the oceans. This would certainly damage the aquatic ecosystem. "
] |
[
"Some questions on the common ancestor of apes and humans."
] |
[
false
] |
1) What did the common ancestor of modern apes and humans look like? I always imagine it looking like a modern ape but I can't really believe that to be the case. 2) Would that common ancestor be regarded as an ape if it would still exist (unchanged)? 3) Is there a book that focusses on the evolution of that ancestor to the apes of the present day? (Are there enough fossils to create such a book?)
|
[
"I think I understand now, thanks.",
"So... we regard apes as a monophyletic group, that is we think that they all derive from the same common ancestor. Or to put it another way they form a completely self contained group if we were to draw an evolutionary tree of animals.",
"The principle observations for establishing monophyletic groups is that the species you're considering share a wide variety of traits and they don't posses some traits that another group has. For instance take humans and chimps, we have very similar body plans, pretty advanced cognitive abilities, we share a great number of genes etc... But we don't walk on all fours or have super efficient kidneys; so we don't include things like birds or cats in our group.",
"One important assumption in phylogeny (the practice of building evolutionary trees) is that when you have two animals that you believe are related and they share some traits then it likely indicates that the joint ancestor of those two animals also had that trait. The more species you have in your monophyletic group that share a feature the more likely you'll assume that the ancestral species had that trait. For instance, all 5 groups of apes today have fairly extensive body coverage of hair so it seems reasonable to believe that our our joint ancestor also had body hair. But what about hair colour? Chimps & Gorillas have black hair, human hair varies a little but tends to be dark, orangutans are orange haired and gibbons have a very wide variety of hair colours. So we might assume our joint ancestor had dark or black hair but as it's not a universally shared trait we'd assign it a much lesser probability of being true.",
"The flipside of that is; any trait not shared probably arose after the 2 species diverged from their common ancestor. Human body hair is very, very fine to the point of making us \"the naked ape\", this isn't shared by any other ape, it isn't even shared by our closest relative so we'd assume this trait evolved after we diverged from the joint human-chimp ancestor.",
"Lastly, our joint ancestor isn't just a bundle of all the shared traits. It was a species in it's own right and it likely had a great number of features that it doesn't share with the still living apes. Things that got lost or bred out as the main ape lineages diverged away from that ancestral species. So compiling a set of shared features in a monophyletic group gives you a good idea of the minimal set of features the ancestral species probably had but it doesn't tell you EXACTLY what that ancestral species was like."
] |
[
"1) well Humans are apes, so the last common ancestor between Humans and OTHER apes would be at the homo-pan split. The earliest species thought to be on the hominin lineage (or arguably before the split) are orrorin, ardipithecus and Sahelanthropus. Google them to get an idea of what it would look like. ",
"If you want to know about the very earliest apes then you are looking at something like Proconsul, again, google it to get an idea of its appearance. It was similar in appearance to a monkey yet had ape features like the lack of a tail. ",
"2) As humans are apes, yes it would have to be an ape.",
"3) There are loads of books on human evolution, hundreds."
] |
[
"For modern apes to form a group (clade) like they do, they must originate from a node at which there was an organism that was itself an ape. Otherwise you are looking at 5 instances of convergent evolution on the general ape phenotype (Lesser apes i.e. Gibbons, Orangutans, Chimps, Gorillas and Sapiens). ",
"On the topic of the book, get The World of Human Evolution (I think thats the title) by Chris Stringer from the Natural History Museum, its exactly what you want. It talks about human origins but also other ape lineages, covering species like sivapithecus, gigantopithecus, dryopithecus, etc. "
] |
[
"Is interstellar space travel even possible considering the amount of random dust/matter out there? Wouldn't a collision with something the size of a grain of sand destroy the craft?"
] |
[
false
] |
If a space craft were travelling extremely fast through space, hundreds of thousands of miles and hour, and it came in contact with just a single stationary or moving molecule, dust particle, or something even larger, wouldn't that essentially destroy the entire craft? I know how utterly empty the vacuum of space is but surely there are rogue pieces of matter. What if there was an object the size of a grain of sand? A marble? Golf ball? A cloud of gas? Chances are too that said matter wouldn't just be stationary but it also would be travelling extremely fast in some direction. Thanks sciencers
|
[
"I'll assume 0.5c is \"extremely fast\".",
"The (classical) kinetic energy of a bare proton at 0.5c is:",
"...which ain't much.",
"The objective answer to your question obviously depends on the parameters of the spacecraft and the debris encountered, but if we make some assumptions, you can get an idea. Let's find out how much matter it would take at 0.5c to cause a 1 kiloton impact event.",
"1 kiloton of TNT is roughly ** 4.184e12 J **",
"That's about a third of a milliliter of water. It doesn't take much..."
] |
[
"But wouldn't a third of a milliliter of water traveling at 0.5 C simply punch a tiny hole through the craft, like a bullet? After all, a bullet doesn't simply expend all its energy the moment it hits something. It often passes through and keeps going having expended little energy."
] |
[
"That's for the engineers to figure out.",
"And being drunk, I'm not exactly in the engineer mindset :)"
] |
[
"How do deserts enrich the Earth's seawater?"
] |
[
false
] |
In "Our Planet", a docuseries produced by Netflix and narrated by David Attenborough, while speaking about the Arabian desert and the surrounding water he mentions that "dust blown from the land contains nutrients that fertilize the surrounding waters. So it is the desert itself that enriches the sea". What does this process look like and what nutrients are provided?
|
[
"The wind picks up the tiny sand particles which are then later on dropped in the sea. This mainly transfers iron to the sea (which clings on to the sand), so much so, that the iron in the Atlantic ocean is 70-90% iron which came from deserts (mainly the Sahara). ",
"Iron is necessary for fertilization of the sea because it naturally is only present in low amounts. The iron is than directly used by phytoplankton, which is then eaten by all kinds of animals. ",
"https://earthsky.org/earth/iron-from-the-sahara-helps-fertilize-atlantic-ocean/"
] |
[
"The parent means \"of the iron found in the ocean, 70-90% comes from the Sahara\""
] |
[
"There are also many other inorganic nutrients present in sand, like phosphorus and nitrogen. These elements among many others are essential to life and get lost permanently due to sedimentation to the bottom of the oceans."
] |
[
"Do any unpowered lenses exist that can reveal a wavelength of laser light not otherwise visible to the naked eye?"
] |
[
false
] |
Is there a combination of laser light wavelength and transparent lens material that reveals the presence of laser light to a human observer without a powered system like an IR or NVG scope? Ideally the light wavelength would not be visible to the naked eye, but would be visible by the human eye looking through the lens material. Thanks.
|
[
"Non-linear optics",
" (which allows the incoming frequency to be different from the outgoing frequency) typically is only observed at super high intensities like from lasers.",
"This is how most green laser pointers work -- they double the frequency of an infrared laser diode using a Second Harmonic Generator non-linear crystal. This process is only efficient if the nonlinear crystal is inside the laser resonating cavity where the intensity is highest, and would be very weak just applying it to the laser output.",
"Note you probably don't want to use a human eye to detect the output directly, there's lots of the original frequency left over -- for example poorly made green laser pointers are especially dangerous because there is a lot of infrared light which doesn't trigger your eye closing even as it burns.",
"For all everyday intensities, materials obey linear optics which means the frequency of light doesn't change.",
"So my answer is maybe, you could possibly detect super-intense lasers using a non-linear crystal, but I wouldn't put that apparatus to my eyes without some well-tested filtering ..."
] |
[
"chances are you are not going to be able to accidentally phase match a crystal with a laser you don't know is there."
] |
[
"So, it's not the lens that allows you to see infrared light. The lens is just a normal lens - it concentrates light into a small area for the actual enhancement to happen...",
"Here is an article on how night vision goggles work: ",
"http://electronics.howstuffworks.com/gadgets/high-tech-gadgets/nightvision3.htm",
"Basically, the lens just sends the light into a tube. The tube contains three things: a photocathode or photodiode array, which emits electrons whenever it is hit by light within a certain wavelength range (this is why it can detect IR), a plate that essentially shoots out a whole bunch of electrons whenever an electron hits it, and phosphorescent screen that lights up wherever electrons hit (like old TV screens).",
"So this entire scheme requires power because the electrons need to come from somewhere (even the photocathode/photodiodes need power). This means that without power, the lens is just a normal lens, and the tube won't do any enhancing at all."
] |
[
"How long, without a nuclear detonation, until we can make Low Background Steel again with normal atmospheric gasses?"
] |
[
false
] |
As above really!
|
[
"That depends on the background level you want to reach. A dark matter detector (looking for a few events in tonnes of mass in several years) has much more stringent requirements than a Geiger counter where a few decays per hour and kilogram don't matter. For dark matter detectors: Probably never due to natural radioactivity. You always need some purification process."
] |
[
"It is just a matter of effort. ",
"This article",
" describes the effort to get an extremely low background for Xenon1T, one of the dark matter experiments.",
"Where possible they used copper instead of steel. The copper samples showed some natural radioactivity, e.g. from radium decays. They considered plating it with gold to reduce the amount of radon (radioactive decay product of radium) escaping from it, but the gold plating contained too much potassium (again naturally radioactive) so they decided against that.",
"The steel samples they used showed activity from human-made sources, from natural sources before making the steel, and even from radioactive nuclei produced by cosmic rays while storing the steel.",
"And so on."
] |
[
"What if the oxygen for the BOP was generated electrolytically from water or thermally from decomposing minerals? Arent't there also air filters for clean rooms that could remove particulates almost completely?",
"Is it just more economic to recycle low background steel than produce it with these methods?"
] |
[
"If a radioactive isotope is accelerated near c, will the decay slow down or remain the same relative to observer?"
] |
[
false
] |
I would assume the decay would slow down, but the more I think on it, the less I'm confident.
|
[
"It will be slower.\nFor example, when cosmic rays hit the atmosphere, they can produce muons. A muon is more or less like an big electron and its lifetime is only 2 µs.\nSo if you don't consider the time dilation, a muon cannot travel more than 2 µs times 300000 km/s = 0.6 km. So you wouldn't expect them to reach the ground. But they do.",
"From our point of view, they live longer than 2 µs. From their point of view, they live 2 µs but the length of the atmosphere is contracted."
] |
[
"Yes, it's very common: around 10,000 muons per m² per s (at sea level). And since they are charged they are fairly easy to detect. So any student with a basic detector can see muons.",
"Actually, many experiments which try to directly detect dark matter have to run under a mountain to get rid of the muon background."
] |
[
"Wow, that's an incredible example. Thanks for that.",
"How often can we detect cosmic rays producing muons in the atmosphere? Is it common?"
] |
[
"How large is the biggest (most massive) supermassive black hole we've discovered?"
] |
[
false
] | null |
[
"NGC 1277"
] |
[
"Adding on to this, its mass is about 17 billion solar masses."
] |
[
"what about NGC 4889?"
] |
[
"How did the human butt become an object of sexual interest?"
] |
[
false
] | null |
[
"This all sounds right but it'd be perfect if you had a few sources"
] |
[
"This all sounds right but it'd be perfect if you had a few sources"
] |
[
"Among primates, and many other mammals, the rump is used to indicate when a female is in heat. The \"female shape\" indicates a sexually nature, well nourished individual. "
] |
[
"Why are the inner planets smaller and solid, while the outer planets are large and made of gas?"
] |
[
false
] | null |
[
"Early in the formation of a solar system you have a large disk of dust (meaning all types of molecules, gaseous or solid) orbiting a protosun. The temperature in the disk depends on how close you are to the protosun. In the inner part of the disk the temperatures are so high only metals and rocky dust are solid. ",
"If you go further out you reach a point where water molecules becomes solid, the ",
"frost line",
". Because there are a lot of water molecules in the dust cloud, this means there is a lot of solid material beyond the snow line when compared with the inner part of the disk.",
"Now planets begin to form, collecting all the dust in their orbit. Due to the ice particles planets that form beyond the frost line grow much faster, eventually becoming heavy enough to capture and hold hydrogen and helium gas molecules. Because these two gases make up 95% of the mass in the universe these planets grow even larger, becoming gas giants.",
"Planets in the inner part of the disk never become heavy enough to capture gas molecules, because after a few 10.000 years the protosun enters the T-Tauri stage, during which ",
"strong solar winds",
" blow all the dust away. "
] |
[
"I believe we are still lacking in enough data to make such wide-sweeping statements. ",
"This is a recent update on Kepler's findings",
" (the percentages are the changes since their last version of the image) - you can see that they're finding more Neptunes than Jupiters, but the number of Earths and Super-Earths are ",
" much lower than the actual number of planets, due to the difficulty of finding them. However, the issue currently is that this ",
" be a real feature - hopefully the next few years will bring in enough data to resolve this."
] |
[
"and, in fact, may not even be common",
"Is there actually any indication of this? I was under the impression that the reason current instruments pick up gas giants orbiting close to their parent star is because they are more sensitive to this type of planet than a large, low-velocity gas giant such as Jupiter or Saturn (which would perturb the parent star little and would not transit in front of it very often).",
"For example, if you were trying to spot Jupiter using the transit method, you might have to wait nearly a decade for a transit to occur!"
] |
[
"Why is monosomy often lethal? Can someone break down this explanation?"
] |
[
false
] |
The explanation states "Many monosomic individuals don't survive because if just one of those genes is represented by a lethal allele, monosomy unmasks the recessive lethal that is tolerated in heterozygotes carrying the corresponding wild-type allele, leading to the death of the organism. In other cases, a single copy of a recessive gene due to monosomy may be insufficient to provide life-sustaining function for the organism, a phenomenon called 'haploinsufficiency'." Is there any way someone could break this down into even simpler terms? I appear to be illiterate when it comes to genetics!
|
[
"Say an organism needs to produce a protein called LIFE to stay alive. Most organisms of that species will have 2 copies of the gene that acts as a blueprint for synthesizing the LIFE protein, but some will have one normal copy of the gene for LIFE, an one mutated copy which encodes the protein LOFE. Having only one copy of the gene, or blueprint, the organism will not be able to produce as much LIFE as an organism with 2 normal copies- depending on how much LIFE is required by the organism this decreases amount may or may not be sufficient to keep it alive. If, however, the organism has only one copy, and it it is the mutated LOFE gene, the organism will not synthesize any LIFE, and will not survive."
] |
[
"For the first case, a lethal allele means that it doesn't do what your body needs it to do and as the name implies having them causes you to die. They are usually but not always recessive simply because dominant ones will generally kill whoever carries them before they can have kids. The most famous example is the agouti gene in mice. AA means the mouse is black, AAy means the mouse is yellow, and AyAy means the mouse is dead. As you can see, having a single A is sufficient for life regardless of the presence of Ay. If the mouse is monosomic, however, then it can either be A or Ay and having only Ay is fatal. Monosomy would be fatal in 50% of those cases, assuming both parents are heterozygous.",
"The other scenario is that gene A codes for a protein or something that you need to live, but one copy of A does not produce enough. Allele a does nothing. You need to be AA and will die if you are Aa or aa. Being monosomic in this scenario means you are just A, which is functionally the same as being Aa, and therefore you do not survive. Monosomy is 100% fatal in these cases."
] |
[
"Say you have fifty thousand genes. A handful of them will be bad versions - lethal versions. ",
"If they are paired up with another set of genes, which will certainly also have some lethal members, it’s extremely unlikely they will be the same ones as yours (unless the other set is from a close relative). Their good versions of your few bad genes will protect you. ",
"If you just have that one set of genes, you are dead for sure."
] |
[
"Other than water and salt, are there any products that we eat which have absolutely no biological origin/ingredients?"
] |
[
false
] |
[deleted]
|
[
"Two examples I could think of are baking powder and various essential minerals in compounds, e.g. Iron(II) sulfate and Magnesium hydroxide.\nMany more chemicals that fit your description are probably food additives, like colours and preservatives."
] |
[
"If you are Scandinavian you might well eat ammonium chloride, and use it as a flavoring in your baking. (If you didn't grow up with it you'll probably gag on it.)",
"Some antacids are essentially powdered rocks (calcium and magnesium carbonate.)"
] |
[
"Additionally our body needs a wide variety of minerals to work; magnesium, iron, potassium, ect."
] |
[
"What are the differences between the modern Windows filesystem and the modern Unix filesystem? Where did those differences come from?"
] |
[
false
] |
In a computer science course I'm in, we covered that Unix file systems use a logical filesystem on top of the physical file system. I understand a bit, but it can get a bit confusing. As I understand it, the logical file system sometimes allows for smaller file sizes (via File Holes) and allows for easier mounting of seperate drives and devices, as they all become effectively just a part of the overall filesystem tree. I think I'd just understand this stuff a lot better if someone here explained it to me though, so thanks for any help. :)
|
[
"This is really an issue of engineering rather than science, so I'm not sure it's on-topic, but I'll try my best to answer anyway.",
"The idea of a \"logical file system\" that you got from your class is fuzzy and conflates a bunch of different issues; it's not really a useful way of thinking about how operating systems work. Additionally, the features you mention (mount points and \"file holes\" aka sparse files) are supported on both Windows and Linux.",
"Like a lot of complex softwsre, a filesystem is usually organized into layers. In Linux, it looks something like this:",
"This basic structure is the same across Linux and Windows, but there are a lot of superficial differences. For example, the Windows VFS treats the first component of a path as a special drive identifier, and keeps a table of mappings like \"C:\\ is the NTFS filesystem in partition 1 of drive 1.\" The Linux VFS just has a single root directory, and it keeps a mapping of other filesystems to subdirectories.",
"Sparse files are different; they're handled by the FS implementation. (\"The VFS said create a 1GB file and write 512MB of data, so I don't need to actually reserve space for the other 512MB yet.\") NTFS on Windows, and all the commonly-used Linux filesystems like ext4 and btrfs, support this functionality.",
"The main thing you need to understand is that a lot of these design decisions are fairly arbitrary. Implementation decisions are fairly easy to change, as long as your on-disk format is extensible enough. VFS changes are harder because they're visible to applications. (For example, Windows 95 had to include a complicated compatibility layer because it allowed long filenames, but still had to support programs written on the assumption that all filenames would be 8 characters with a 3-character extension.) So some of these characteristics have no better justification than \"that's the way we designed it 30 years ago.\""
] |
[
"logical filesystem",
"In Linux, we call it the VFS. I've never heard the term logical file system. The VFS is responsible for a number of features, and I won't get nearly all of them. The basic notion for question is to identify which specific file system driver (ext4, btrfs, vfat, etc.) can fulfill an IO request and forward the request on to that specific driver. It allows userspace a uniform set of syscalls to interact with any file system, and for the kernel, an intermediate layer to understand how to dispatch those syscalls to the particular module. ",
"Windows has its own VFS. No idea what he's talking about. Any OS that supports multiple file systems and uniform IO syscalls between them has to, or else on Windows, you'd have NTFS, FAT32, etc., specific IO syscalls, and userspace would be responsible for determining which file system driver to invoke to satisfy a request. ",
"As I understand it, the logical file system sometimes allows for smaller file sizes (via File Holes) ",
"Just to reiterate: the Linux VFS simply allows you to do this in a uniform way across all filesystems (well, all those that support it -- it's an optional feature). See ",
"fallocate(2)",
". This is no different than open(2), write(2), close(2), etc. ",
"and allows for easier mounting of seperate drives and devices, as they all become effectively just a part of the overall filesystem tree.",
"Just because I'm a little peeved at how your professor is framing the issue: You can mount stuff outside the filesystem tree on Linux. It's called a mount namespace.",
"More than anything it sounds like your professor is stuck way in the past with Windows and doesn't appreciate the advances made since 9x."
] |
[
"So when my professor said that Windows effectively lacked a virtual filesystem, and handled everything on the physical file level, was he wrong? Or am I still misunderstanding?",
"He is wrong, but you have to have some fairly low-level knowledge about Windows to know how it really works.",
"The paths in Windows you usually see are \"win32 paths\" - actually they are internally referred to as \"dos paths\". But at the lowest level they are translated to \"native paths\" (or NT paths). Actually this maps down to the NT object namespace. This is a general virtual filesystem that like on linux not only contains files, but also devices and other kinds of special objects. On Linux the root is usually a physical filesystem, on Windows it's always virtual (that is possible on linux too though, you can use a tmpfs as your root). You can explore the object namespace by using the ",
"WinObj tool",
".",
"If you access the win32 path c:\\some\\dir\\file.txt then it is translated to the path \\??\\C:\\some\\dir\\file.txt. \\?? is a symbolic link to \\GLOBAL??. Then \\GLOBAL??\\C: object is a symbolic link that points to the device, for example \\Device\\HarddiskVolume1. Accessing a sub path of a disk device redirects to the file system driver if the disk is mounted. So finally the path \\some\\dir\\file.txt is delivered to the file system driver, which then looks up that file.",
"There is by the way a lot of sublety in how the win32 paths are translated into native paths, Google's Project Zero recently wrote about it in a lot of details: ",
"https://googleprojectzero.blogspot.dk/2016/02/the-definitive-guide-on-win32-to-nt.html"
] |
[
"How can some animals live for several centuries without dying off from cancer far earlier?"
] |
[
false
] |
In an earlier thread on , many concluded that at some point cancer rates would overwhelm treatment. As we age, the risk of cancer increases due to likelihood of certain errors increasing with time. So, how do certain , with very long life spans, overcome this problem?
|
[
"First, the examples in your second link seem mostly to be ",
" lifespans, which is not the same as average lifespans. A single individual living far beyond the average lifespan isn't really indicative of anything, just that they're \"lucky\" enough to avoid mortal accidents, cancers, etc.",
"Next, many of the animals on that list have slow metabolisms, especially the invertebrates and cold-blooded organisms. I believe it was discussed in your first link that the slower the metabolism, the slower the aging and the slower the growth of cancerous cells. It may be much more likely for the organism to die of other causes than of slow-growing tumors."
] |
[
"I thought I read that on reddit, but after searching I found this: ",
"http://www.livescience.com/9680-cancer-kills-wild-animals.html"
] |
[
"Rule number one about science: Don't tell people what you think. Tell them what you've proven."
] |
[
"Why does my tv antenna work better when I stand near it?"
] |
[
false
] |
I cut the cord about 3 years ago and use an HD antenna to watch broadcast networks. In my latest move, my antenna was dropped and now works funky. Specifically, in SF when tuned to CBS 5.1, the antenna cuts out frequently (2 seconds of clear broadcast, 2 seconds of static and lost signal) when I watch it from bed or the couch. When I walk over to the antenna though, it suddenly works perfectly clear. Note: I don't touch it all, but somehow my proximity makes it work. Why is this? My tv antenna works better when I stand by it -- why?
|
[
"The human body acts as an antenna in, and of itself. The human body does conduct electricity (think salt water), and so it can be a pretty good antenna.",
"If standing next to your antenna all day doesn't suit you though you can ghetto-rig aluminum foil to help strengthen an existing antenna. "
] |
[
"The body both conducts electricity well enough to act as an antennae while ALSO absorbing other radio signals, which may remove the competing static signals.",
"Humans are also surrounded by an electrostatic field of sweat."
] |
[
"Maybe your body acts as a sort of RF filter. Does it matter where you stand around the TV? I presume you are standing on the side of the antenna that your broadcast is coming to achieving this?"
] |
[
"How close are we to having Star Trek like deflector shields?"
] |
[
false
] |
[deleted]
|
[
"You should stop replying in askscience if you have no idea what you are talking about. There is a reason why your posts keeps getting downvoted."
] |
[
"Here",
".",
"Some of it seems rather recent. Apparently they came up with some sort of plasma bubble that protects the contents from radiation..."
] |
[
"See also ",
"3M electrostatic wall"
] |
[
"How are some birds able to imitate human speech?"
] |
[
false
] |
Reading made me curious - how are birds such as parrots and mynahs able to imitate human speech when their "vocal" tracts are so different from those of humans? For example, birds do not have lips, so how are they able to produce labial consonants? Is it just that they are able to trick the human ear into hearing certain sounds when only approximations of them are being produced? Do they use techniques similar to those used by ventriloquists?
|
[
"In addition to a larynx, birds have a ",
", a complex two-part noise-making apparatus. By manipulating the numerous muscles that attach to it, they can create an incredible array of sounds, even several distinct sounds at once. Syrinxes are far better than larynxes for producing sounds-- in fact, Turkey Vultures, the only bird that doesn't have a syrinx and has to rely on its larynx, can only communicate in pretty awful hisses and grunts.",
"Here's",
" a page with some animations that illustrate how birds can use each side of their syrinx independently for weird results.",
"Basically: bird voiceboxes are superior to puny mammal voiceboxes."
] |
[
"Is it just that they are able to trick the human ear into hearing certain sounds when only approximations of them are being produced?",
"In a certain sense, yes. As you may or may not know, speech isn't just pure tones - overtones (in a musical sense, not in a literary sense) give a sound a lot of important qualities. And if you reproduce the main tones and enough of the overtones, you get a decent approximation to the sound.",
"Keep in mind that the reverse works too - we don't have bird-like vocal tracts, but humans can accurately reproduce most all bird sounds."
] |
[
"I'm mostly kidding - we love our African Grey. He's a gas - but he is quite musical and talkative.",
"Actually, the worst thing he does are two specific sounds. The first is the sound of a backing up FEDEX truck - so every time we hear that we rush to the door - I think he gets a kick out of that (in fact, my yard man also says - I always hear a fedex truck backing up, but it is your bird).",
"The other annoying sound, which we are beginning to break him out of the habit of, is a ear-splitting scream that he does when we leave his vision... his way of reminding us he's there. We've gotten him pretty much out of that one.",
"But we love his talk. WATER, BYE, HELLO, ALOOOOHA. lots of muttering under his breath. ",
"Oh ya, and he has our sniffles, coughs, burps, and sneezes down pat. He can sneeze with the best of us, and he is fond of greeting me with a joyful BURRRRPPPPP!",
"What I find amazing is that he decides on his own what words he will say and what words he won't. Try as we can, we can NOT teach him certain words. On the other hand, a word that is rarely mentioned will suddenly appear in his dictionary. When we go to our sailboat for a couple of weeks, we leave him with friends and when we get back everything he says is in their voices, at least for a week or two."
] |
[
"What is radiation poisoning and how does it work, also how is it treated?"
] |
[
false
] |
Specifically radiation from nuclear bombs, but anything else is appreciated.
|
[
"Hey, this is something I have to worry about at my job! Well, sort of, I have to worry about my dosage.",
"Radiation poisoning is radiation killing cells in your body. Specifically, it destroys or mangles your cells' DNA. There are three general bodily functions affected by radiation; gastrointestinal, hematopoietic (blood), and nervous system. ",
"Radiation from nuclear bombs have two different methods of attack. Beta particles can only penetrate the first few layers of skin and cause burns. Beta particles are whats typically caused by fallout. Gamma particles can penetrate through your body and cause whole body burns and irradiation. This is particularly damaging because it destroys bone marrow (hematopoietic stem cells, can no longer make functional WBC or RBC), damages the linings of various organs and causes massive amounts of internal bleeding."
] |
[
"Very interesting, thank you!",
"How would you treat having a higher dose of radiation, and what is occurring to fix the problems caused by the radiation poisoning?"
] |
[
"You should read the ",
"Mayo Clinic",
" page on treatment. It'll be much more indepth than what I can offer. I also have the utmost respect and trust for the Mayo Clinic, and have had friends with exces radiation exposure be treated there(albeit for fairly low dosage compared to fallout)."
] |
[
"What factors have caused the more recent uptick in nut allergies among youth?"
] |
[
false
] |
I don't think I met anyone with a nut allergy until I was in my 20s and even now, most of the people allergic seem to be young children. Is this a built up immunity that we didn't worry about previously or something else?
|
[
"I do all those things and haven't been sick either. Correlation doesn't mean causation"
] |
[
"Do you have a citation on this? The studies I've seen have shown correlation on a nation-wide scale, but negative evidence in actual experiments as to whether increased levels in the diet increases risk of allergies."
] |
[
"Correct!!",
"It has nothing to do with \"manufacturers\" and their \"substitutes\", that's just silly pseudoscience. The prevailing theory of allergy prevalence is called the ",
"hygiene hypothesis",
", which suggests our immune system continues to attack perceived invaders, even in the absence of parasites and bacteria. This is why auto-immune disorders and allergies (both examples of an over-active immune system) are seen predominantly in developed nations ",
"http://www.coronadobiosciences.com/images/img-hygiene-hypothesis.jpg",
" "
] |
[
"Can adrenaline actually give you the strength to lift a car and how does it work?"
] |
[
false
] | null |
[
"here's a good breakdown",
". Basically the adrenaline gives your more blood and oxygen to your muscles which in turn allows you to be more effective. Like others have said, you don't suddenly gain super strength, but you ",
" suddenly able to use the full potential of your musculature. Your body normally prevents you from doing so because it isn't necessary (I don't need full strength to lift my coffee cup) and you could injure yourself very easily. ",
"Someone once explained it to me in comparison to gorillas. They're foolishly strong but lack the finer motor skills of humans because huge explosive strength is hard to direct into fine movement."
] |
[
"There was a 4 part mini series made by The Discovery Channel called ",
" in 2008 that has cool graphics and goes over this in the first episode. ",
"It was a really interesting and well made miniseries."
] |
[
"The extra oxygen delivery gives you increased stamina but not strength. The epinephrine/stress/fight response gives you strength over what you’d normally expect. It’s most likely a combination of the increase in calcium release and increased signal potential ion that allows for more muscle to be recruited.",
"When non active people start going to the gym, most of the strength gains in the first month are due to increased regulation that allows for more nerve firing to recruit more contraction.",
"Epinephrine most likely increases strength from a combination of allowing stronger signals for contractions and the increased calcium resulting in stronger than normal.",
"Epinephrine is known to cause calcium release in smooth muscle to increase tone like in the vasculature to increase blood pressure but it’s skeletal effects are less studied.",
"Oxygen delivery in and of itself isn’t going to make you stronger in absolute terms but allow you to continue force production over time instead of rapidly dropping off."
] |
[
"Can you improve your eyesight..."
] |
[
false
] |
by flexing your vision? For instance, you focus on something close to you, then focus on something far away from you, and repeating.
|
[
"Programs like that and the Bates Method exist(",
"http://en.wikipedia.org/wiki/Bates_method#Treatments",
"), but the results remain inconclusive and highly controversial. I wouldn't hold my breath about it.",
"A healthy diet and adequate vitamin intake, wearing sunglasses, and avoiding other life style risks such as smoking, etc is beneficial to sustaining good vision though. ",
"http://www.allaboutvision.com/buysmart/see_clearly.htm"
] |
[
"Just trying to help Ill be sure not to next time :D"
] |
[
"Thank you for the reply. I have also heard that the more you use glasses you become more dependent on your glasses. Is that true?"
] |
[
"When light goes from a vacuum, into water, then back to a vacuum. At what speed is it now traveling ?"
] |
[
false
] |
Is it traveling at the speed of light through water? Or, is it back up to the speed of light in a vacuum? If so where does it get that energy boost from?
|
[
"It’s traveling at the vacuum speed again. There is no energy boost associated with the change back to vacuum; the frequency of the light stays the same. But the phase velocity changes because the index of refraction changes."
] |
[
"Light actually goes slower in a medium.",
"This is because light in a medium isn't a pure electromagnetic wave anymore. Light in vacuum is just an oscillating electromagnetic field, whereas light in a medium is an oscillating electromagnetic field + oscillating electric dipoles (caused by motion of ions or electrons) + perhaps even oscillating magnetic dipoles."
] |
[
"Just to add ... the speed of light, either through vacuum or through the medium, is ",
"inversely proportional to the electric permittivity and magnetic permeability",
" of the vacuum or medium. In a medium, these two constants have higher values than they do in free space ... consequently, the speed of light is lower in those media. When light leaves a medium and reenters free space, the local values of those constants reverts back, and so light regains its faster speed. No additional energy is required for this; all light travels at the speed of light (in vacuum and in a medium) regardless of how energetic it is or isn't.",
"Hope that helps,"
] |
[
"Do scientists have any opinion as to whether virtual particles occur only in vacuums or if they occur anywhere?"
] |
[
false
] |
Bonus question: Do virtual particles that spring out of existence from nowhere then annihilate themselves violate the conservation of energy principle?
|
[
"The ",
" place that I have ever seen a concrete description of a 'virtual particle' is in the context of Feynman diagrams, where it is nothing more than a term in an algebraic expression.",
"The idea is that something like an photon is a ripple or disturbance in the 'photon field'. Such photons interact with electrons or positrons which are disturbances or ripples in the 'electron/positron field'. ",
"Even if there are no actual electrons or positrons in the room, the photon, or disturbance in the photon field, still interacts with the ground state of the electron field. Even with no electrons or positrons, the fully undisturbed state of the electron/positron field is still somewhat 'ripply'.",
"If you want to calculate the effect of this interaction, one can use perturbation theory, and represent the interacting fields using Feynman diagrams, and then 'understand' the interaction as the creation and subsequent annihilation of a 'virtual' electron/positron pair. However, this creation and annihilation is nothing more than an accounting technique in trying to fight through some horrendous algebra.",
"What is really happening is that a quantum field is not 'perfectly still' in its zero particle, or ground state. There are still fluctuations, and other fields will interact with these fluctuations. This interaction is sometimes described in terms of 'virtual particles', but unfortunately such 'virtual particles' have no meaning outside of the Feynman calculus."
] |
[
"Do virtual particles that spring out of existence from nowhere then annihilate themselves violate the conservation of energy principle?",
"No. They don't come from nowhere. Even a vacuum has energy and virtual particles come from that energy."
] |
[
"or is this based on the beliefs of the scientific community?",
"This isn't based on belief, but on evidence from experiments and quantum field theory."
] |
[
"What recent advances in your field are lesser known to the masses but could have significant impacts on our way of life in the next 5-10 years?"
] |
[
false
] | null |
[
"problems like?"
] |
[
"problems like?"
] |
[
"http://www.youtube.com/watch?v=1GhNXHCQGsM"
] |
[
"What is happening when I wake up starving, wait an hour or two and don't eat, and the hunger dissipates?"
] |
[
false
] |
I can't think of a good, concise way to word this question without telling it like a story. I usually wake up around 8 or 830 AM every morning. Some days I don't wake up hungry, but twice a week I'll wake up STARVING, like almost nauseous. I bear the hunger and by 9 or 10 I'm not hungry and can wait till about 1 PM to finally nourish myself. I know this is unhealthy, but I'm in college. Anyway, what is my stomach doing when it just stops being hungry? EDIT: Damn. Thanks for answering y'all. I guess I should eat more.
|
[
"It's not starvation mode.",
"When you get this feeling, your body has burned off much of the free, easy glucose in the blood, liver and muscle, and is in a transition period where it decreases the rate of glucose metabolism and begins to rev up the burning of fatty acids. Until this process is complete, and the fatty acid metabolism is up to speed, you'll feel wanting. But then you'll suddenly feel fine again.",
"You usually don't feel hungry like that in the AM because you slept through the transition period and are already burning fat efficiently by the time you wake. For most people, the culprit is likely eating late in the evening or having a \"midnight snack.\" By doing this, your body won't run low on glucose until later in the night, possibly not until the time you wake up. If you wake up still in (or not even yet having started) the transition phase, you'll get the ravenous hunger feeling.",
"Actual starvation phase begins much later. Here, the body starts breaking down muscle and organ tissue. Exactly when this starts varies a lot, depending on the individual fat stores and such, but doesn't generally begin until 10 days or two weeks without sufficient intake. If the starvation is dramatic (like, bam, all of a sudden eating almost nothing), then the muscle/organ breakdown may begin earlier."
] |
[
"it stops because ",
" cells start ",
" breaking down glycogen (imagine a long chain of glucose molecule holding hands) and fat in your body. If you wait a little longer to eat (several days), they begin ",
" breaking down proteins ... this involves cells breaking down protein in muscles into amino acid which is then converted into glucose in the liver. ",
"After these assholes have eaten up most of protein, which is required for proper organ functions, your body begins to die. ",
"The end. "
] |
[
"Does that mean skipping breakfast is a good idea if you're trying to lose weight?"
] |
[
"Do humans contain 'white meat' and 'dark meat' like poultry?"
] |
[
false
] | null |
[
"Mammalian muscles differ from avian muscles by having ",
"multiple muscle fiber types in each muscle",
". So avian muscles are generally either translucent pink or darker translucent pink, while mammalian muscles are much redder and grainier in appearance, and more opaque. The color in all cases comes from myoglobin, of which fast twitch muscles, such as the chicken breast muscles used in flying, have the least, and slow twitch muscles, such as muscles used for standing around a long time, have the most.",
"edit: Except for ratites, like ostriches, emus, and rheas, which have dark red meat like mammals."
] |
[
"Pork is pink to red",
", but while were at it, I'd like to know what cheetah meat looks like. I'm guessing a pale pink, since their fast twitch muscle fibers make up ",
"\"83% of the total number of fibers examined in the vastus lateralis.\""
] |
[
"Why do pigs have white meat rather than red meat like other mammals?"
] |
[
"If all matter in space slowed to a stop, would there be any noticeable change?"
] |
[
false
] |
[deleted]
|
[
"Try this on for size",
"."
] |
[
"Try this on for size",
"."
] |
[
"Are you asking what would happen if ",
" stopped? I seek clarification on that, because metric expansion is not actually motion, though it sounds like that's the conceit behind the question.",
"The answer is that if metric expansion stopped all at once, tomorrow, we wouldn't know it for a very, very long time. We can only tell metric expansion is occurring because we observe light that was emitted very long ago (i.e., very far away) at some known frequency, and see that it is now of some other, lesser frequency. So light has to cross a great distance before the effect of metric expansion — or in this case, the absence of such an effect — can be observed."
] |
[
"Those black areas underneath the skin of potatoes - Toxic? Edible? Normal?"
] |
[
false
] |
[deleted]
|
[
"I used to own a restaurant that was famous for the fries that were sold. Due to the high volume I bought, the company that manufactured the fries wined and dined me for a couple of days, and gave me a tour of a farm and their factory. ",
"The dark areas commonly found on fresh potatoes are called sugar ends. ",
"http://www.kimberly.uidaho.edu/potatoes/Pnw427.pdf",
"It's been about 20 years since the tour, but even back then a lot of high science was involved from farm to shipping, and it amazed me.",
"I learned about high tech pest management, breeding, farm management, harvesting, cool processing techniques like steam peeling and optical recognition of defects and rejection of sliced fries with defects(sugar ends), and controlled atmosphere storage tech."
] |
[
"Cool!"
] |
[
"Thanks. On smaller scales, abrasive peeling is a thing, but you should check out steam peeling. ",
"It's even done with tomatoes, but with a twist, it's done under vacuum so it can be done at lower temperatures."
] |
[
"Is it possible to create a sound that dissipates unusually quickly?"
] |
[
false
] |
I'm imagining creating a sound that can easily be heard close by, but after leaving a certain range the sound grows inaudible very rapidly. Is it possible to manipulate a sound wave to do something like that, or is the rate at which sound waves die out only affected by the air it travels through?
|
[
"I think the easiest way to do this would be to change the source of the sound rather than the sound itself. There are specialty speakers and devices designed to do this - I know I've run into them at museums and other places.\nMost quality monitor speakers have a waveguide designed to create as wide a soundstage as possible but these try and do the opposite. A quick google gave me these:",
"http://en.wikipedia.org/wiki/Directional_sound",
"http://www.panphonics.com/directional-audio/sound-shower",
"As for how sound seems to 'dissapate' at different frequencies, it's a function of the human ear.",
"http://en.wikipedia.org/wiki/Equal-loudness_contour",
"Hope that helps - if you have some project in mind feel free to PM me"
] |
[
"I can't think of a way to synthesize a sound that will dissipate unusually quickly when played through an ordinary loudspeaker. But a clever spatial arrangement of out-out-phase elements can create a significant near-field sound that dies out quickly. Tuning forks and wine glasses, for example, sound louder up close than you'd expect from measuring the amount of sound they radiate to long distances.",
"PDF",
"PDF",
" There are some related ideas at ",
"http://en.wikipedia.org/wiki/Directional_sound",
" (which unfortunately lacks references)."
] |
[
"Yes. Of course sound can be focused! You could do this by creating a sound source that focused the sound instead of a wall that did it (imagine a parabolic speaker arrangement).",
"But even better is the ability to use ultrasound to do this. Ultrasound refracts and spreads less than lower frequency sounds. You can create beams of it. And, ultrasound is audible through its envelope because there is an inherent half wave rectifier in the human auditory system. This is being exploited now by people create advertisements in front of stores that have audio that goes with them - and the audio can only be heard if you stand in the correct place. You take several ultrasound beams with the same signal and focus them on the same point in space. Their superposition creates a signal that dissipates rather quickly.",
"hth"
] |
[
"Is there an industrial or structural reason that any recyclable plastic bottle most always has a non-recyclable plastic cap?"
] |
[
false
] |
I have looked pretty far and wide for an answer. The only reason I could think of would be that bottle makers want a harder plastic cap, either for the threading or to prevent it breaking, but if high density polyethylene is strong enough for the container, why isn't it strong enough for the cap? Can you not dye HDPE? Is polypropaline just more durable?
|
[
"Both polyethylene and polypropylene are thermoplastic polymers. That is, they can be heated up and reformed, thus 100% recyclable. This is in comparison to thermosetting polymers like Bakelite, which cannot be heated up and reformed, as they will break down when heated.",
"The main reasons that you are told not to recycle the polypropylene cap:",
"Polyethylene and polypropylene have different melting temperatures. They need to be processed separately. ",
"Also, the bottles are crushed by the recycling facility before shipment (if they're sent out to melt at another facility) to save space. Leaving the cap on would cause problems with injuries and the crushing process. Polypropylene is harder, and would likely shatter instead of compressing nicely like the bottles.",
"Finally, the human element is the last line of defense against making sure extraneous materials aren't traveling with the polyethylene bottles down the line towards the melt. Workers would be a lot more likely to miss the small caps, which would then remain solid as the bottles are melted. ",
"Edit: Forgot to answer why the cap is polypropylene instead of polyethylene. One, polypropylene is cheaper. Two, polypropylene is one of the next best things to Teflon for \"slipperyness,\" so the cap comes off a lot easier than it would compared to PE on PE."
] |
[
"Those need to be removed as well, otherwise they'll stay solid when the bottles melt! That's one of the main problems with scaling up recycling, there isn't an easy way to automate this. ",
"You should remove the ring when you toss out the bottle into the recycling bin. Most plants use people to manually sort the bottles and pop off the ring if it hasn't been removed yet. Some throw it out, some recycle the PP. It's the easiest way to do it currently. ",
"Bottles are so non-standard in every way that it would be both hard and inefficient to develop an automated system to take off the rings, especially if the bottles have been crushed for transport."
] |
[
"What about the little plastic rings that stay on the bottle neck? Are they small enough that it doesn't matter, or are they filtered out somewhere in the process?"
] |
[
"A question about death"
] |
[
false
] |
Recently, my grandfather passed away and my nephew (age six) has not been told much. This got me thinking, at what age do children typically understand death? My gut tells me it would be formal operations, based off of Piagetian theory. Is this correct? Or can children comprehend death in concrete operational?
|
[
"He isn't asking what is death, he's asking at what age in development a child can grasp the concept of \"death\"."
] |
[
"Why? This is a perfectly valid question for ",
"/r/askscience",
" . ",
"If only I knew the answer. "
] |
[
"The way I see it, is that death is an explainable biological phenomenon (e.g. cessation of brain-function, respiration or whichever definition doctors these days use). ",
"Death can be caused by severe trauma, illness, or 'old age': cell division over the years shortens telomeres in the DNA, which in turn leads to malfunctions in celldivision and ultimately death. ",
"Now, I'm not claiming that I have a clue what death is, but trained medical staff, or philosophers studying the subject can definitely know what is going on, thereby making it comprehensible. ",
"What about sleep? Coma? These concepts have been pretty well explained by science. \nWhat is so special about death that makes it incomprehensible?"
] |
[
"If the door of an in flight commercial airplace was opened, would everything be sucked out a la hollywood films?"
] |
[
false
] |
Going even further, if somehow there was a small hole in the passenger section of the plane, would the suction immediately cause it to grow bigger and bigger eventually sucking out the passengers (again, as seen in hollywood films)? Thanks in advance! edit - commercial airplane*
|
[
"Watch the mythbusters episode, also commercial airline doors open in a little then push out making it impossible to open whilst the cabin is pressurized aka at altitude "
] |
[
"It is impossible for the door to open in flight while the cabin is pressurized. The pressure differential keeps it sealed shut.",
"And being sucked out through a small hole is a myth. The real danger in an uncontrolled decompression is from hypoxia and hypothermia.",
"http://en.m.wikipedia.org/wiki/Uncontrolled_decompression",
" "
] |
[
"Others have stated the safety features of a passenger door. However, in the case of a ",
" the size of that door, the result is rapid decompression and ",
"major damage can occur",
".",
"A small hole won't cause catastrophic damage."
] |
[
"Why are certain programming languages more suitable for creating certain types of programs?"
] |
[
false
] |
So for example C+ is suitable for the creation of device drivers, Java is suitable for web applications, etc. What component of the software architecture makes one programming language more suitable for the creation of a certain type of program over another? What makes any one language more versatile than another language?
|
[
"Programming languages have different design goals that tend to encourage certain kinds of programming. Be aware that every serious programming language can simulate any other serious programming language so you could technically write any possible program in any possible language (actually because of type checking and a few other things this isn't 100% true but its not important).",
"C (and C++) are designed to give the programmer close access to the underlying architecture of the computer. You can access memory directly through things like pointer arithmetic and you are responsible for allocating and freeing memory yourself. In addition, these languages are compiled into machine code rather than interpreted. These features make C and C++ ideal for writing code that need to be very fast and does a lot of low level memory operations and syscalls (like device drivers). These features come with costs. C is known for being difficult to write securely and difficult to read and maintain. Also, since C is compiled, it might perform differently on different architectures. ",
"So what we see here is that there is a ",
" tradeoff when making a programming language. The C designers sacrifice some safety, readability, and flexibility in order to have a language that was fast and gave the programmer direct access to the machine. ",
"Now consider Java. Java is an interpreted language that runs on the Java Virtual Machine (JVM). This means that Java can be run on anything that has a JVM without being recompiled (write once, run anywhere). This has a performance cost associated with it that makes Java less suited for low level programs like device drivers. Java also has automated garbage collection, which makes programs much easier to write but also has a performance cost. Java is also statically typed, which prevents programmers from writing some bad programs but can reject good programs and also requires extra programming work. These all fit into Java's design goals, which were (among other things): ",
" and ",
".",
"Now consider Python. Python is designed to be extremely easy to code in. It is not statically typed so programmers have to write less boilerplate code. It has lots of paradigms (first-class functions, OOP stuff) so that programmers can use whatever style they are used to. It is interpreted, so programmers don't need to worry about targeting specific machines. This makes it very good for quickly developing small scale programs but not as good for large scale applications that must be correct or for applications that must run extremely quickly. ",
"Every language is designed with these tradeoffs in mind, making some better languages for some applications than others. "
] |
[
"It's all somewhat of a subjective thing in most cases as to which languages are \"better\" at any task. Most modern languages can do almost everything.",
"However, in most cases when someone makes a statement like \"C is good for device drivers.\" or \"Python is good for databases\" we are expressing a subjective opinion that the environment, standard libraries, and/or language features makes a certain task relatively easier to express than in other languages.",
"It's sort of like the \"vocabulary\" of the language makes it easier to do or say certain things. In human language, a good analogy would be the way certain obscure languages work compared to more modern language. There is no word that holds the same meaning as \"Computer\" or \"iPhone\" in ancient mayan, so although you could probably get by if you had to speak to an ancient mayan (\"I then opened my minurature magic instant communication device\") having a discussion about technology that was restricted to only that language would be difficult. In that sense, someone would rightfully say that \"English is better at talking about technology than ancient mayan\""
] |
[
"The OS isn't necessarily the lowest layer in a system. A hypervisor often runs underneath an OS, or multiple virtual OS's could be run on a single machine. There is also a BIOS, which is needed to actually start running the OS. ",
"So I don't think it breaks the definition to have an OS running on top of a JVM. The JVM would expose virtual memory addresses and syscall interfaces to the OS just like a hypervisor would. "
] |
[
"Why do some substances (metals, wax, etc.) lose density when heated, whilst others (egg, meat, etc.) tend to solidify?"
] |
[
false
] | null |
[
"Metals become liquids when heated because their particles gain energy and so they can move about. Eggs contain complex proteins such as Albumin. At a temperature higher than about 60 degrees Celsius, the complex molecules become denatured by the heat. They change into something else which happens to be a solid. The first example was a physical change and it is reversible, The 2nd is a chemical change and is not easily reversible as a new substance is formed."
] |
[
"I wouldn't necessarily say that a new substance is formed in the egg case! Incoming pedantry:",
"All proteins are long chains of units called amino acids. What makes proteins special is that the units within these chains can interact, and so when folded you get things like hydrogen/ van der waal interactions and other chemical phenomena (hydrophobic/hydrophilic groups being probably the most major) that makes certain folds more stable than others. ",
"Since these bonding types are dependant on temperature and pH, at differvent temperatures/pH different folds are more favored physically (not to mention proteins often have several favorable configurations that requires outside intervention to control). When egg is cooked, albumin unfurls and cross links into a larger and solid structure. Albumin can't return to its previous structure because of its current bonding and because it's orginal fold was likely assisted with other chaperone proteins!"
] |
[
"Eggs contain lots of proteins, which are long chains of assorted amino acids ",
"twisted into complicated knots, pleats, and folds.",
" ",
"The covalent bonds holding the chain together are strong and will not break much until the egg starts to burn. The intermolecular forces holding the knotted chains in their current shape are relatively weak - hydrophobic amino acids attract and some amino acids form hydrogen bonds with eachother, but not very sturdily. Without these forces the proteins would unravel and tangle.",
"When heated some of these bonds break and the proteins un-fold, then re-fold into a random mass of tangled strands. This is called ",
"denaturation.",
" These tangles also expose more of the hydrophilic amino acids and trap more water. "
] |
[
"Does Urine Therapy have any real scientific proof supporting its 'benefits'?"
] |
[
false
] |
I have met a few people who actually will drink a small cup of their own urine every morning, and they claim that the health benefits are worth it. One guy told me that after he started doing it he stopped testing positive for Hepatitis-C which he claimed to have had for 15 years.
|
[
"Straight off of wikipedia:",
" \"There is no scientific evidence of a therapeutic use for untreated urine.\" It links to some articles as well.",
"I'm currently looking around trying to find some peer-reviewed articles, I'll get back to you if I can find anything conclusive."
] |
[
"http://www.skepdic.com/urine.html",
"A great search engine that would be useful to you to bust common myths is ",
"Skeptical Search Engine",
". It searches popular skeptics sights."
] |
[
"Not to derail the specifically scientific discussion of urine composition, but I feel it's relevant to ask why your friend believed so strongly that urine therapy had any merit? I see this quite often (even within my own peer group) of people swearing by these (sometimes bizarre) alternative treatments based at the absolute best on anecdotal evidence and at worst some inferred convoluted conspiracy.",
"Again, not trying to make some soap box pontification about the state of society or the gullibility of people or whatever, just genuinely curious about how he arrived at this conclusion."
] |
[
"If I hold my hand to the back of a blow-dryer, will the rotor blades go faster or slower?"
] |
[
false
] |
[deleted]
|
[
"The rotor blades will move faster, because there is \"no air\" to offer resistance to the rotor blades. It works similar to a vacuum cleaner, when you cover its mouthpiece. It will spin up because you are removing the load from the motor. A similar effect can be seen in a car with a manual transmission. What happens if you are driving at a certain speed(with a certain RPM) and then press the clutch without removing your foot from the speeder? The RPM increases. This is again because you disconnect the load(road, wheels) from the engine, via the clutch. The effect is probably also noticeable when you have a boat engine that you pull out of the water(it will go faster because there is no load) or when you pull out your hand mixer from whatever you are mixing.",
"With regard to the resonance: You can't change the frequency of the sound that the motor emits, so there is no reason that resonance would interfere here. The resonance can however \"overpower\" the noise from the motor, making it difficult to hear. But an FFT should reveal this.",
"Out of curiosity and boredom, i have decided to do a little experiment. By doing an FFT of a recording of the sound of a blow-dryer, you should be able to determine the frequency of the sound, and you should be able to see how it changes. I have done a recording of my vacuum cleaner(i don't have a blow dryer), and will post the results soon. ",
"Edit: Here is the result. I did a spectrogram, which turned out to be easier than to separate the sound files. ",
"Image is here",
". ",
"Sound file is here",
".",
"You can easily see that the most powerful frequency, which is about 9kHz, steps up to about 12kHz when i cover the mouth piece. Vacuum cleaners run at about 10k RPM, according to google, so that seems reasonable.",
"You can also see that some extra noise is introduced in the very low frequency area, at about 2kHz, when i cover the mouthpiece. 2kHz corresponds to a wavelength of ~ 17cm. I would expect some sort of standing waves to arise, and strangely enough, the room for the vacuum cleaner bag is just about 17cm. This leaves a few questions: ",
"But the conclusion is clear: All the sound sources, including the most powerful one, which is assumed to arise from the motor, increases in frequency whenever the mouthpiece is covered. Some extra noise is added at low frequencies when the mouthpiece is covered, but that does not appear to affect the other sounds. "
] |
[
"You are not creating \"no air\" on the front side of the rotor blades which push against the motor.",
"That is true, but that is not the way propellers work. They \"dig into the air\", on one side of the propeller and pulls through the air(or, in fans, pulls the air through). They don't dig into the air on both sides. If they did, there would be no propulsion in ships or planes. And when there is no air to dig into, there is nothing acting to slow down the engine. If there was a huuuge pressure on the backside of the propeller, it would probably be difficult for it to push more air into that area, making it turn slower. But that is not the case, when there is no air in front of it to pull through. ",
"If you let the air move, it's as if it were in a gust of wind of that speed, helping it spin more easily.",
"I am a bit confused by your statement. Are you saying that if the motor/propeller was not blocked, it would run faster? That is not true. If there was a gust of wind, that wind would carry additional kinetic energy to the propeller, which would be transformed into rotational energy, thus increasing the speed of the propeller. But if there was no gust of wind, the air would remain motionless until affected by the propeller, which would transform its rotational energy into kinetic energy air, making it move. And when the energy is lost from the propeller, it slows down."
] |
[
"I am a bit confused by your statement. Are you saying that if the motor/propeller was not blocked, it would run faster?",
"Yes. ",
"If you put an even stronger vacuum behind it, it'll even spin backwards overpowering your motor -- just like a windmill does."
] |
[
"Do dogs really love their owners, or are they just really good at getting us to feed them?"
] |
[
false
] | null |
[
"Does it count if studies show both dogs and humans produce oxytocin when making physical contact?"
] |
[
"Super subjective question and I’m no dog behavioralist, so this is speculative. Dogs are pack animals, the same as us. Love is a very strong emotion, and one of its primary functions is to bond members of a group together. Although we may experience more nuanced and complex versions of emotions, I believe that they are present in most animals, at least mammals, as drivers of basic instinct. Taking this, and the fact that we are part of a dog’s pack, I’m pretty sure they really do love us (and this ignores the more obvious signs like how excited they are to see us come home, etc.)."
] |
[
"Yeah that would be pretty great starting evidence actually!"
] |
[
"How much lower were water levels during the time of Polynesia expansion ?"
] |
[
false
] | null |
[
"Wikipedia says that's 3.5-1 kyr before present? ",
"Not very different. Reconstructions say that global sea level has been fixed at modern values (to within 1-2 meters) for the past 4-7 kyrs. Furthermore, I can't think of any local changes in polynesia that would cause deviation from the global average over that time period. ",
"Thinking more broadly about the implications of the question: even if the sea level were different by 10 metres or so, the most impressive parts of polynesian expansion are isolated volcanic islands in deep water. For these islands the drop in sea level would not change the land area that much nor make them particularly easier to find or travel between."
] |
[
"Yep, just to add a graph to this explanation, ",
"averages of different records of sea level, relative to modern sea level",
" suggest sea level was within ~2 meters of modern for the last ~5 thousand years. "
] |
[
"Thanks for the response . I was curious maybe water levels were low enough that land was easier to find . "
] |
[
"How do other apes keep their nails short?"
] |
[
false
] | null |
[
"Hah, alright. How do orangutans trim their mustaches then?"
] |
[
"Same way I do. "
] |
[
"I always see my dogs chew them, and I've seen videos of primates biting them, among other animals with similar claws and nails. As I've witnessed caring for many different animals and observing others, active animals will use their claws and they'll break here and there from regular use. It's not like nail biting is some high level skill that was created after humans were able to think linguistically and condition themselves through Hollywood films to bite their nails out of nervousness or something."
] |
[
"Is there any way to improve intelligence or are we stuck with what we have?"
] |
[
false
] |
Barring implants, neural "cyborg-ification", etc.
|
[
"Richard Feynmann claimed that he wasn't exceptionally intelligent, but that he focused all his energies on one thing. Of course he ",
" exceptionally intelligent, but he makes a good point. ",
"I think one way to improve your intelligence is to actually try to understand things in a very fundamental way. Rather than just accepting the kind of trite explanations that most people accept - for instance, that electricity is electrons moving along a wire - try to really find out and understand what is actually happening, and you'll begin to find that the world is very different from what you have been taught and you'll be able to make more intelligent observations about it."
] |
[
"Well that depends on what you mean by intelligence. You can train your math skill, increase your knowledge, attain a knowledge-seeking attitude, have intellectual confidence(which imo counts for a lot) etc etc but improving your ability to learn might be tricky.",
"If you mean the average intelligence of our species then you can certainly improve it a lot by proper early education and intellectual inspiration."
] |
[
"I disagree, we derailed evolution and natural selection",
"No, we ",
" the outcome of natural selection. It is irrational to think that we aren't part of a process of natural selection. The only way we can conclusively not be part of natural selection is if we all die.",
"No matter how sophisticated our reasons and thought processes, we still compete with other animals and each other, and we are still part of nature.",
"Thus, natural selection hasn't provided us with the tools we need for today's society.",
"How are you coming to this conclusion? Those who don't have the tools required to deal with today's world die out. Those who do, survive. Natural selection.",
"Software that meets people's real and imagined needs, prevails over software that doesn't. Natural Selection.",
"Music that appeals to popular taste prevails over music that doesn't, all aesthetic considerations aside. Natural Selection.",
"“Nobody ever went broke underestimating the taste of the American public.” -- Henry Mencken. Natural Selection.",
"What if every person was as smart as Einstein, wouldn't the world be a better place?",
"If everybody was as smart as Einstein, nothing would change, because that would become the new average. Natural Selection.",
"As long as we make choices, as long as nature requires things of us, as long as we have offspring, we are embodiments of natural selection.",
"Every idea, every computer program, every motion picture, every book, every ",
", is an example of natural selection. Choice is natural selection. Natural selection is choice."
] |
[
"Is there a maximum and/or minimum possible wavelength for light to have?"
] |
[
false
] |
If so why?
|
[
"No. Since the Lorentz transformations are continuous in the velocity ",
", we can always boost into a reference frame in which a given light ray has arbitrary wavelength."
] |
[
"You run into trouble at very long wavelengths - if dark energy is constant, then the part of the universe you are in causal contact with doesn't increase beyond limit. A wavelength longer than this part of the universe cannot be called radiation in a meaningful way."
] |
[
"All wavelengths are possible since we can always just locally boost into a frame with arbitrary relative velocity to a given frame. As I already wrote, Lorentz covariance means all wavelengths are possible. "
] |
[
"Does it take the same amount of energy to run a mile at 5 minute pace that it takes to run the same mile at 6 minute pace?"
] |
[
false
] |
If a person was to run a mile at a fairly fast pace, they would expend X amount of energy. What if the same person were to run the same mile in the same conditions but at a slower pace... Would they expend the same amount of energy?
|
[
"For humans, yes. Energy efficiency of the human running gait is independent of speed. Search for \"human\" on ",
"this Wikipedia page",
".",
"Do note that this is true only if you are comparing running vs running (not running vs walking), and only in humans (as far as we know)."
] |
[
"The faster you run leads to an exponentially increasing amount of heat generated.",
"Why do you think this is so? Isn't the heat loss constant per number of ATP produced?"
] |
[
"From a basic thermodynamic standpoint, this cannot be true, while the wiki says that: \"it is commonly thought that the COT remains constant across all submaximal running speeds\"\nOne reason this cannot be true could be seen for energy used to cool yourself down: The faster you run leads to an exponentially increasing amount of heat generated. (More energy is used - haste makes waste) So you can imagine the amount of energy you have to use producing sweat to cool yourself down after a 5 minute mile would be much greater than the sweat-energy used for running an 8 minute mile. "
] |
[
"If an object of large mass would suddenly appear 1 light-second away from you, would you feel the gravity instantly or with a delay of one second?"
] |
[
false
] |
[deleted]
|
[
"The speed of gravitational waves in the general theory of relativity is equal to the speed of light in vacuum, "
] |
[
"Keep in mind that photons are massless - but they do have momentum. This means that photons will naturally follow the geometry of space-time.",
"Arm that with the knowledge that the more dense (massive) an object is, the more it distorts the geometry of space-time.",
"Also keep in mind that the gravity is already in the area where the photons are traveling - so as the photon travels it encounters the gravitational wave and follows the natural geometry that distortion produces.",
"(There is also a basic problem with your concept of \"photon traveling away from it\" - since that probably doesn't happen - whereas a photon traveling near it will be caught by the distortions. Unless you are specifically talking about hawking radiation)",
"Edit... if you were talking about hawking radiation I quote this from a wiki on it...",
"A slightly more precise, but still much simplified, view of the process is that vacuum fluctuations cause a particle-antiparticle pair to appear close to the event horizon of a black hole. One of the pair falls into the black hole whilst the other escapes. In order to preserve total energy, the particle that fell into the black hole must have had a negative energy (with respect to an observer far away from the black hole). By this process, the black hole loses mass, and, to an outside observer, it would appear that the black hole has just emitted a particle. In another model, the process is a quantum tunneling effect, whereby particle-antiparticle pairs will form from the vacuum, and one will tunnel outside the event horizon."
] |
[
"Keep in mind that photons are massless - but they do have momentum. This means that photons will naturally follow the geometry of space-time.",
"Arm that with the knowledge that the more dense (massive) an object is, the more it distorts the geometry of space-time.",
"Also keep in mind that the gravity is already in the area where the photons are traveling - so as the photon travels it encounters the gravitational wave and follows the natural geometry that distortion produces.",
"(There is also a basic problem with your concept of \"photon traveling away from it\" - since that probably doesn't happen - whereas a photon traveling near it will be caught by the distortions. Unless you are specifically talking about hawking radiation)",
"Edit... if you were talking about hawking radiation I quote this from a wiki on it...",
"A slightly more precise, but still much simplified, view of the process is that vacuum fluctuations cause a particle-antiparticle pair to appear close to the event horizon of a black hole. One of the pair falls into the black hole whilst the other escapes. In order to preserve total energy, the particle that fell into the black hole must have had a negative energy (with respect to an observer far away from the black hole). By this process, the black hole loses mass, and, to an outside observer, it would appear that the black hole has just emitted a particle. In another model, the process is a quantum tunneling effect, whereby particle-antiparticle pairs will form from the vacuum, and one will tunnel outside the event horizon."
] |
[
"What happens when E=MC^2 is applied in a medium in which the speed of light is slower?"
] |
[
false
] |
[deleted]
|
[
"There is no medium in which the speed of light is slower. What's ",
" happening is that atoms in the material absorb and re-emit photons, and the delay between the two makes light appear to travel through it slower. It's often convenient to refer to this as slowing down the speed of light, but the actual speed of the photons does not change at all."
] |
[
"c refers explicitly to the speed of light in a vacuum."
] |
[
"No, c is a constant"
] |
[
"Why is Kelvin an SI base unit?"
] |
[
false
] |
Our chemistry teacher explained to us recently that temperature is just the avereage kinetic energy of all the particles in a sample. But then shouldn't temperature be measurable in Joules? Or Joules/mol? And if it is, then why is Kelvin a base unit if it can be derived from units of energy?
|
[
"Because different materials can have different amounts of energy in them per unit molar mass--molar heat capacity. If we defined temperature as energy per unit molar mass, for instance, then a glass of water in front of you could/would be at a different \"temperature\" than the table it's sitting on, even if they're both at equilibrium.",
"Temperature is material-agnostic and that's why it's a useful and distinct unit.",
"http://en.wikipedia.org/wiki/Heat_capacity"
] |
[
"From a thermodynamic perspective, temperature is much like fugacity. ",
"Temperature is a number associated with ability for flow of energy from one item to another item. Energy does not flow from high energy to low energy, but from high temperature to low temperature. Temperature and energy are different and the relationship varies by compound and state as ",
"/u/numbakrunch",
" explained. ",
"This is just like how atoms don't flow from high concentration to low concentration, but rather from high fugacity to low fugacity. ",
"I know this is trying to explain a simple concept with a more complicated metaphor, but it really helps to understand temperature and fugacity if you think of them this way. ",
"So to awnser ",
"/u/doctaamonstaa",
" 's question, temperature is not measured in energy (joules) because temperature is more of a way to quantify the ability, desire, or ease for the energy to leave the system and less of a way to quantify how much energy is in the system. "
] |
[
"Fugacity is basically just pressure but corrected for the fact that gasses are not ideal."
] |
[
"How is it possible for shampoo to smell so different from it's taste?"
] |
[
false
] | null |
[
"Because of the difference between \"taste\" and \"flavor\" from a scientific standpoint.",
"Flavor is the total sensory experience of something you put into your mouth, minus the somatosensory (touch, feel) aspect. This includes both taste (the chemical properties your tongue can detect, ie salty, sugary, bitter, acidic, umami) and aroma/odor (the volatile chemicals detected by your nose.)",
"When you smell shampoo, you are getting only the aroma--which is usually a major component of flavor. When you put shampoo in your mouth (and really, try not to do this on purpose) you are also getting the taste. Shampoo probably has a bunch of salts, including ones your tongue can detect; basic chemicals that taste bitter; and detergents and oils that will make the whole mixture stick to the tongue for a while. These chemicals will produce a taste (a horrid one) that overwhelms the aroma and becomes the dominant flavor of the shampoo.",
"Still, in the mouth is better than in the eyes . . . ",
"Reference: ",
"http://cst.ufl.edu/taste-vs-flavor-whats-the-difference.html"
] |
[
"So in short, your nose only smells volatile substances, but when you put something in your mouth, you get the dual action of your nose and your tongue, with the latter sensing both volatile and non-volatile. Yes?"
] |
[
"Typically, the manufacturers will add something based on Denatonium to it, in order to prevent large-scale ingestion. It typically requires 10ppm to be functionally inedible. Bitrex is a common branded form, which (as is my understanding), is not volatile at all and as such, has no effect on the smell, but a huge effect on the taste.",
"https://en.wikipedia.org/wiki/Denatonium",
" - More legible, Wikipedia page",
"(",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3066567/",
" - Notably less legible paper)"
] |
[
"Why are thermal images so blurry? What is hard about making thermal imaging lenses?"
] |
[
false
] | null |
[
"Cost is the major reason. Most IR detectors have a resolution lower than even the cheapest cellphone camera. Thre IR detectors and lenses are very expensive\nThe Flir T660 has a 640x480 resolution, very high for IR cameras. The cost is $25000 to $30000"
] |
[
"There's also pretty strict export laws (because an infrared camera is a pretty important piece of a heat seeking missile) ",
"So it might be that you're seeing blurry images from the lower-res versions that are legal to export, as the restricted ones are much more expensive. "
] |
[
"Several factors that drive the cost up:",
"As many thermal cameras work in the wavelength range 8 – 16 μm, you need detectors that work with it, that are less common than silicon massively used with visible, so there's less economy of scale.",
"The wavelength also means that pixels can only be reduced to a similar size, before they stop proving additional detail in the image. 17 μm pitch is quite common, so 640x480 sensor has to be at least 10.1x8.2 mm in size. While with visible light you can make >40 MP resolution sensor of the same size. "
] |
[
"Why is Intel still using 14nm in their cpu's when the technology for 5nm is already out?"
] |
[
false
] |
Intel's new rocket lake is using a 14nm and yet Samsung's new chip for its phones is using 5nm so the technology cleary exists. Is there no benefit for Intel to using a smaller node?
|
[
"Comparing process technology is very difficult. This is because there are many different tradeoffs (static leakage, dynamic power, and frequency being the main components).",
"The short answer is that you can't compare the numbers across companies (Intel's 10nm is (or will be) better than their 14nm, but Intel's 10nm and Samsung's 10nm are going to be very different).",
"This is a good article if you want more of the history of how things got to be where they are:",
"https://www.extremetech.com/computing/296154-how-are-process-nodes-defined"
] |
[
"Just to add on here for any confused readers, the name of the process node doesn't actually correspond to any physical dimension on the CPU. It used to measure the gate length, but it hasn't done so for years. Now it's basically used as a marketing figure, justified by \"well these are all the ways we've improved our process since node X, and that was Y nm so this is Z nm.\""
] |
[
"Intel is trying to move to 10nm and 7nm but is having manufacturing problems (yield issues). This is 100% intels fault - they for years only released incremental upgrades to gain maximum profits as they would not have to reconfigure manufacturing lines. They failed to be innovative - they were looking at competitors and putting out chips just slightly better. Now they are losing major support form the likes of apple and microsoft that are now developing for alternative platforms. In all they may be a minor player in 10 years."
] |
[
"Why are melting Ice Caps causing the world water level to rise, when (correct me if i'm wrong) the higher percentage of the ice is in the water already and ice has a lower density than water?"
] |
[
false
] |
[deleted]
|
[
"Maybe in covered surface you're right but the volume of ice on land is far greater than the volume of sea ice. Sea ice is a couple of meters thick and the land ice on Greenland and Antarctica is up to 3 kilometers thick, that's a lot."
] |
[
"This is correct but the bigger contributor to sea level rise is simply the fact that warm water expands. "
] |
[
"Oceanography Undergrad here. Yes, you are correct. The rough number we use (if I remember correctly) if about 50% of the sea rise so far is due to thermal expansion. The other 50% being land ice. ",
"edit*\nWent back and read part of the IPCC report. Here is some additional data:",
"Over the period from 1961 to 2003, thermal expansion contributed about one-quarter of the observed sea level rise, while melting of land ice accounted for less than half.",
"During recent years (1993–2003), for which the observing system is much better, thermal expansion and melting of land ice each account for about half of the observed sea level rise, although there is some uncertainty in the estimates."
] |
[
"Is there a study that shows exactly how damaging chronic ibuprofen use is to the stomach lining?"
] |
[
false
] |
I used to know a kid that took 4 200mg ibuprofen 3X a day for years due to migraines/sinus headaches, and he also drank heavily during this time (it was in college). He didn't show any adverse effects like bloody stools or anything for the 3 years that I knew him. Is it just something that only affects certain people? How dangerous is it exactly?
|
[
"Nothing in biology or medicine is 100%, so there will always be individuals who don't fit the standard mold. However, on the whole we know that NSAIDS like ibuprofen can lead to GI damage due to its effects on prostaglandins, which are protective.",
"The clinical presentation of NSAID gastropathy may range from dyspepsia and abdominal pain to serious and potentially fatal complications such as perforation, ulceration and haemorrhage. [...] The incidence of clinically significant NSAID-related upper gastrointestinal adverse events is four times that in the general population not receiving NSAID therapy. ",
"source",
"For example, in an endoscopic study by Geis et al., gastric or duodenal ulcers were present in 24% of NSAID-treated individuals with OA or RA, whereas the Food and Drug Administration Arthritis Advisory Committee notes that symptomatic ulcers and potentially life-threatening complications have been found in up to 4% of patients per year. The potential impact of these adverse events is highlighted by data from Spain, which show that the mortality rate associated with NSAID or ASA use is ∼5.6%, equivalent to 15.3 deaths per 100 000 users. To put this risk into perspective, data from the USA in 2006 indicate that the risks of dying as a result of a car accident or firearm injury are approximately 15 and 10 per 100 000, respectively.",
"(RA = rheumatoid arthritis; OA = osteoarthritis; ASA = aspirin; NSAID = nonsteroidal anti-inflammatory drug)",
"Case-control studies and meta-analyses have shown that the risk of upper GI complications is increased ∼4-fold in NSAID users, compared with non-users, and the risk of peptic ulcer disease is increased 5-fold. The risk is highest during the first month of treatment [relative risk (RR) 5.7; 95% CI 4.9, 6.6], and then remains elevated afterwards. ",
"Figure demonstrating risk factors here",
".",
"In contrast to the well-documented risk of upper GI damage associated with NSAIDs, NSAID-related lower GI damage has not been widely studied and remains poorly characterized. This damage includes increased mucosal permeability, mucosal inflammation, overt or occult blood loss, malabsorption, protein loss, ileal dysfunction, diarrhoea, ulceration, strictures, major bleeding and perforation. [...] In a landmark study, Allison et al. found post-mortem evidence of small intestinal ulceration in 8.4% of NSAID users, compared with 0.6% of non-users (treatment difference 7.8%; 95% CI 5.0, 10.6%; P < 0.001). [...] A systematic literature review reported that mucosal breaks or small intestinal injuries were present in up to 71% of NSAID users, and that up to 88% of patients with lower GI bleeding were NSAID users.",
"source",
" <- There're a lot more data in that review article if you want more specifics, but the paragraphs above are the highlights I think."
] |
[
"4x200, three times a day is actually below the maximum dose. Max dose is 3200mg per day. Also, there is no specific interaction between alcohol and ibuprofen at an allowable dose. They can both cause stomach irritation, but this won't necessarily be the case for everyone. "
] |
[
"thanks!"
] |
[
"Do snowflakes spontaneously form from vapor? Or do droplets first fall then crystallize?"
] |
[
false
] |
Was trying to understand the origin of a snowflake and whether or not there is an instantaneous transition from water vapor or if the droplet forms and crystallizes during its descent. I imagine hail is just droplets freezing during descent? Is it the temperature difference that produces one over the other?
|
[
"I have a Master's degree in Meteorology, currently working on my Ph.D. Should probably take the time to get the flair, but eh.",
"The processes that form hail and snow are very different. Snow, or ice crystals, are formed in cloud regions where temperatures are uniformly below freezing. All snow is initially formed from ice nuclei; these are tiny particles in the atmosphere which water has initially frozen to (or, if temperatures are extremely cold, can be just pure water - but that is rare, as it requires temps below -38 degrees C...pure water doesn't always actually freeze at 0 degrees C, but that is a separate physics discussion for a different time). From there, excess water vapor in the atmosphere can undergo deposition (gas -> solid) onto the nuclei, forming a crystal. Exactly how this happens depends on the exact temperature. Here is a nice chart showing the different ice crystals which grow at different temps (and this chart isn't complete or perfect, I will say):",
"http://ryanhanrahan.files.wordpress.com/2012/01/habits.gif",
"Ice growth is dependent on both temperature and the \"willingness\" of water vapor to move to the solid form (excess vapor pressure over ice).",
"For \"good\" snow, you want dendrites; these maximize air pockets giving you a good, \"thick\" snow that accumulates very quickly. In forecasting snow events, meteorologists look for cloud formation (rising motion) in the -12 to -18 degree C region of the atmosphere. We call it the \"dendritic growth zone\".",
"Hail is formed by a different process. Hail requires very strong rising motions, or updrafts, to keep frozen particles aloft. There is currently a lot of research in this area that is challenging the traditional approach thought of for hail stone formation. Current thinking leads to two ways hail stones grow: \"dry\" and \"wet\" growth. Ice nuclei form in the cloud, but the strong updrafts present cause these nuclei to mix with supercooled water droplets. When the ice nuclei encounters supercooled water, the water freezes to it. This is \"wet\" growth. If the ice nuclei enters a region of excess water vapor, the water vapor undergoes deposition onto the ice nuclei. This is \"dry\" growth. The hail stone encounters these regions throughout its life cycle as it moves through the cloud. Wet growth leads to clear ice, whereas dry growth lead to \"foggy\" ice. This is what may give the hail stone its onion like appearance:",
"http://upload.wikimedia.org/wikipedia/commons/d/d5/Hagelkorn_mit_Anlagerungsschichten.jpg",
"The stronger the updraft, the longer the hail stone can stay in the cloud, the larger it grows.",
"Hope that helps!"
] |
[
"Great answer, but I'll just tack on a more basic summary in response to OP's question:",
"The snowflakes form directly from vapor for the most part. Very small dust particles (called ",
"ice nuclei",
") are of the right size/shape to start accumulating ice directly from vapor, and at the right temperature (the above-mentioned -12 to -18 C) water vapor deposits rapidly onto the growing ice crystal, eventually becoming a snowflake."
] |
[
"So does the size of snowflakes depend on how much pollution is in the air or excess water vapor to build onto crystals?"
] |
[
"What is the difference between magnetism and electricity?"
] |
[
false
] |
Hi ! I was sitting in my Physics class today and my teacher told us we were beginning to cover magnetism and electricity. After the introduction to the topic, I made a comment that they were the same thing (I was under that impression) My teacher, who is a psychopath when it comes to students saying things, exploded telling me that they are completely different, then refused to explain. Anyway, I was wondering, what are the distinct differences, are they even different? Thanks in advance!
|
[
"Well, let's not be hasty. The teacher is correct that electricity and magnetism are not \"the same thing.\" There is a reason why you have to learn both, and not just one! The are indeed both aspects of the same thing (the electromagnetic field), but each aspect is important and distinct. It's just that they transform into each other under Lorentz boosts, so what looks like an electric field in one frame of reference looks like a magnetic field in another, and vice-versa."
] |
[
"Electricity and magnetism are intimately related, so much that they are considered one force--one of the four fundamental forces of nature--electromagnetism. A changing electric field furnishes a magnetic field, and vise versa (as per Ampere's law). Your teacher doesn't know what (s)he's talking about."
] |
[
"One difference is that electric charge exists and magnetic charge doesn't... ",
"as far as we know",
"."
] |
[
"Blood typing O blood type"
] |
[
false
] |
Alright so I've been wondering this for a while. There are 3 different types of blood. A,B, and O. Each can mix with each other initially at birth (DNA gene) Anyways my question being the O type of blood is the most common. And around 50%ish. The A is about 27% and the B. being the least common of the 3. Now what I don't get is that O is recessive. Why is this? shouldn't it be less common if it's recessive to the A and B blood type. Any thoughts or answers would be awesome.
|
[
"ABO blood types are different because of different proteins on the red blood cell surface. There is an A protein and a B protein. Blood type O is the lack of either of those proteins. So, if you receive the gene for A from your mother and O from your father, then you will have blood type A. So O is recessive because if you have either protein, you are automatically A, B or AB. Sometimes the cells display codominance of the genes meaning they express the genes for both A and B, thus AB blood type.",
"I can't answer for the commonness of each blood type. I would imagine that given a long enough time scale, we'd see an equilibrium between ABO types."
] |
[
"The thing is that dominance/recessiveness and allelic frequency are completely independent. I don't know the frequency of the A, B, and O alleles off-hand, but we can use some made up numbers to see how at least this is possible. ",
"So lets say that A is completely dominant over O, B is completely dominant over O and A and B are codominant. If A represents 10% of all alleles and B represents 5% then the remainder (85%) is the O allele. Assuming there is no selection pressure, lets just randomly assort these alleles according to their frequency in the population.\nAA= 1% \nAO= 8.5%\nAB= 0.5%\nBB= 0.25%\nBO= 4.3%\nOO= 72%",
"These are numbers I pulled out of thin air but you can see how if a recessive allele is common enough there is enough likelihood of two recessive alleles coming together that the recessive phenotype can still be the most common. "
] |
[
"There at least 30 blood group in humans. They have to do with the presence of antigens in the surface of red cells in the blood. O means the lack of them... you can read more here: ",
"http://en.wikipedia.org/wiki/Blood_type"
] |
[
"Is it possible for something to have negative mass?"
] |
[
false
] |
Is there anything in the universe that has properties opposite of gravity resulting from having the opposite of mass?
|
[
"The existence of negative mass would not cause any contradictions, and the mathematics work out in a self-consistent way, so it can't be ruled out. However, we currently have no reason to believe that anything with negative mass actually exists."
] |
[
"Firstly when you derive E=mc",
" from the four impulse you actually get E",
" =m",
" c",
" +... which implies |E|=|m|c",
" >0. Secondly your argument is on the same level as form example this: Galileo transformation says x'=x+tv but SR says something else so SR is wrong. You cannot argue the non existence of something through showing a contradiction in a theory that does not include it. The theory can simply be wrong or a special case of bigger theory.",
"To answer the question: Negative masses are not prohibited by general relativity and you can solve the field equations, but these solutions are currently seen as nonphysical since neither the standard model nor experimental evidence suggest the existence of such matter."
] |
[
"Negative mass would make either the Alcubierre drive possible, or would allow you to create / sustain a wormhole which GR tells us would allow communication into the past.",
"Either of these things (which are only possible with negative mass) would allow FTL communication, which thus breaks causality as you can create a reference frame where any FTL communication is actually traveling into the past (even without the wormhole) "
] |
[
"Do plants need gravity to grow?"
] |
[
false
] |
I was thinking how plants grow in outerspace (artificially of course). I know the ISS has some expirements going on where they grow plants but I was not sure how well they grow or what special measures need to be used. Thanks
|
[
"There was a news item here in the U.S. this past week about astronauts on the ISS eating vegetables grown in microgravity for the first time. From that perspective their main concern seems to be artificial lighting to mimic sunlight more so than gravity. "
] |
[
"Before the food growing, they have probably done tons of experiments with plants before."
] |
[
"I would be interested to know what effects gravity or the lack thereof would have on plants in space"
] |
[
"Is if more fuel efficient to add gas while going uphill?"
] |
[
false
] |
The road I drive on each day to work has many hills and slopes. Is it more fuel efficient to add more gas while going uphill or should I accelerate before the hill comes and add less gas while actually on the hill?
|
[
" slow down while rising up the hill, then allow your car to speed back up on the way down. Otherwise, you'd have to apply gas on the way up, only to apply the brakes on the way back down. ",
" get into an accident caused by abnormal driving behaviors that confuse/surprise other motorists. You'll be all over town visiting repair shops. You'll also have to pay your deductible and higher premiums on your auto insurance. "
] |
[
"This is on the highway, and I'm driving against the traffic, so it's usually pretty clear. I never apply brakes on the highway unless someone cuts me off.."
] |
[
"The amount of work done (and therefore the amount of gas used) will be the same with all other variables held constant... of course all other variables aren't constant. What you may be overlooking is that you can use the Earth's gravity to give you some momentum to get up the hills: Try to coast down hills (no need to give any gas here), get going as fast as it is safe to go and then let that speed take you up the hill and add a little gas to maintain your speed as you go up the hill.",
"I do this all the time on my way to work, and it really makes me mad when the car in front of me has to stop to make a turn at the lowest part of the hill so all my momentum is lost to braking. :("
] |
[
"If you know you have contracted a cold and it's still in its incubation incubation period, what proven steps can you take to lessen its severity?"
] |
[
false
] | null |
[
"I found this with a bit of googling",
"\n",
"http://www.sciencedaily.com/releases/2011/11/111101130200.htm",
"So I guess one thing someone can do is to stay warm. It gives some sort of boost to the body's mechanism for destroying infected cells. I don't know how much of an effect this'll have though. I think the largest factor is always gonna be the antibody production, etc.."
] |
[
"I can't answer your question, so don't upvote this, but the common cold and influenza are completely different things. Influenza is caused by the Influenza Virus, whereas the common cold is usually caused by Rhinovirus.",
"http://en.wikipedia.org/wiki/Rhino_virus"
] |
[
"Thanks for the clarification! I made the change."
] |
[
"What is the effective actual brightness in relation to the human eye of planetary objects in the distant solar system? What I mean is: are photos of Saturn the brightness they are due to long exposures or would they actually be relatively dim objects due to their distance from the sun?"
] |
[
false
] |
[deleted]
|
[
"You can see most of the planets with your bare eyes on a dark night, except Mercury (because of its small size and because it is usually only visible at twilight due to its proximity to the sun) and Uranus/Neptune (too far away, but you can see with a good pair of binoculars). Most pictures of outer planets are taken with a good zoom lens and a long exposure. ",
"If you stay up until about 5am tonight you should be able to see Saturn. If you have good vision you might be able to make out its rings."
] |
[
"For example, if I was in a spacecraft orbiting Neptune would it be as bright as most photos show?",
"This really depends on a few factors, including how close your spacecraft is to Neptune.",
"As a basis for comparison, think about how bright the light is from a Full Moon. If the Moon were twice as close, it would take up 4 times as much area on the sky, and the moonlight would then be 4 times as bright.",
"The same goes for Neptune, although with a few additional corrective factors. It's 30 times as far from the Sun as the Moon-Sun distance, which means Neptune is only receiving 1/900th the sunlight as the Moon per square meter. However, Neptune is also about 4 times as reflective (surprisingly, the Moon is actually very dark, about the same reflectivity as asphalt), so Neptune actually ",
" about 1/225th the sunlight per square meter as the Moon.",
"On top of that, you also have to account for the fact that Neptune is quite a bit bigger than the Moon. Since it's radius is about 14x the size of the Moon, that means it takes up about 200x more area of the sky. When combined with the 1/225th per square meter of sunlight reflected, it turns out that if your spacecraft-Neptune distance were just about the same as the Earth-Moon distance, it would be just about as bright as the Full Moon (though it would take up a much larger portion of the sky). As you change your distance to Neptune, again that would increase or decrease that brightness as the distance squared."
] |
[
"For example, if I was in a spacecraft orbiting Neptune would it be as bright as most photos show?",
"This really depends on a few factors, including how close your spacecraft is to Neptune.",
"As a basis for comparison, think about how bright the light is from a Full Moon. If the Moon were twice as close, it would take up 4 times as much area on the sky, and the moonlight would then be 4 times as bright.",
"The same goes for Neptune, although with a few additional corrective factors. It's 30 times as far from the Sun as the Moon-Sun distance, which means Neptune is only receiving 1/900th the sunlight as the Moon per square meter. However, Neptune is also about 4 times as reflective (surprisingly, the Moon is actually very dark, about the same reflectivity as asphalt), so Neptune actually ",
" about 1/225th the sunlight per square meter as the Moon.",
"On top of that, you also have to account for the fact that Neptune is quite a bit bigger than the Moon. Since it's radius is about 14x the size of the Moon, that means it takes up about 200x more area of the sky. When combined with the 1/225th per square meter of sunlight reflected, it turns out that if your spacecraft-Neptune distance were just about the same as the Earth-Moon distance, it would be just about as bright as the Full Moon (though it would take up a much larger portion of the sky). As you change your distance to Neptune, again that would increase or decrease that brightness as the distance squared."
] |
[
"[x-post] Saw this in r/gifs and just want to know what causes this and how to replicate it? Link inside."
] |
[
false
] | null |
[
"My chem teacher did this. It is really easy to replicate. Get some rubbing alcohol, put it in a 5 gallon jug, close the top of the jug and shake the jug around. This will cause the alcohol to vaporize. Light a match take your hand away from the opening and quickly through in the match. It will do that but faster (the gif is in slow motion). "
] |
[
"OMG you knew Richard Feynman! ",
"We used to put on magic shows — chemistry magic — for the kids on the block. My friend was a pretty good showman, and I kind of liked that too. We did our tricks on a little table, with Bunsen burners at each end going all the time. On the burners we had watch glass plates (flat glass discs) with iodine on them, which made a beautiful purple vapor that went up on each side of the table while the show went on. It was great! We did a lot of tricks, such as turning “wine” into water, and other chemical color changes. For our finale, we did a trick that used something which we had discovered. I would put my hands (secretly) first into a sink of water, and then into benzine. Then I would “accidentally” brush by one of the Bunsen burners, and one hand would light up. I’d clap my hands, and both hands would then be burning. (It doesn’t hurt because it burns fast and the water keeps it cool.) Then I’d wave my hands, running around yelling, “FIRE! FIRE!” and everybody would get all excited. They’d run out of the room, and that was the end of the show! ",
"Later on I told this story at college to my fraternity brothers and they said, “Nonsense! You can’t do that!” (I often had this problem of demonstrating to these fellas something that they didn’t believe-like the time we got into an argument as to whether urine just ran out of you by gravity, and I had to demonstrate that that wasn’t the case by showing them that you can pee standing on your head. Or the time when somebody claimed that if you took aspirin and Coca-Cola you’d fall over in a dead faint directly. I told them I thought it was a lot of baloney, and offered to take aspirin and Coca-Cola together. Then they got into an argument whether you should have the aspirin before the Coke, just after the Coke, or mixed in the Coke. So I had six aspirin and three Cokes, one right after the other. First, I took aspirins and then a Coke, then we dissolved two aspirins in a Coke and I took that, and then I took a Coke and two aspirins. Each time the idiots who believed it were standing around me, waiting to catch me when I fainted. But nothing happened. I do remember that I didn’t sleep very well that night, so I got up and did a lot of figuring, and worked out some of the formulas for what is called the Riemann-Zeta function.) ",
"“All right, guys,” I said. “Let’s go out and get some benzine.” ",
"They got the benzine ready, I stuck my hand in the water in the sink and then into the benzine and lit it … and it hurt like hell! You see, in the meantime I had grown hairs on the back of my hand, which acted like wicks and held the benzine in place while it burned, whereas when I had done it earlier I had no hairs on the back of my hand. After I did the experiment for my fraternity brothers, I didn’t have any hairs on the back of my hands either. "
] |
[
"It is sometimes called the ",
"\"whoosh bottle.\"",
" I've done it several times with 70%-90% isopropyl alcohol with great success. Place less than 50 mL in a 5 gallon jug, swirl, ",
", and light with a match or grill lighter. ",
"If you try this, be sure to wear goggles and have both a metal object (pie pan) to cover the opening to put out lingering flames and a fire extinguisher near by in case something goes amiss (never needed to use one)."
] |
[
"Since the universe began, has time been going the same speed?"
] |
[
false
] |
I understand how time is relative so this is a difficult question to explain. The big bang happened in an instant. If I was in the middle of the big bang when it happened would it still be instant? Does a second to me right now feel longer than a second would feel during the big bang (provided that I was in the middle of the big bang somehow)?
|
[
"If a span of time objectively ",
" longer, that span would ",
" longer.",
"Time is measured according to the duration and frequency of time-dependent phenomenon. A ",
"second",
", for example, is defined as \"the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.\" If that many periods took twice as long to pass, then the second would be twice as long. But twice as long relative to ",
"?",
"Any change in the \"speed of time\" that affects everything equally is meaningless. You might as well assert that the entire universe reverses itself every nanosecond, but we don't perceive it because we're reversed as well."
] |
[
"Great answer. It's not called \"relativity\" for nothing."
] |
[
"There isn't any way to be sure. However, since there is no reason whatsoever to suspect otherwise, we don't."
] |
[
"When I think of flight (as in an airplane) my mind perceives it as the wing creating a low pressure system above the airplane which basically allows it to float up into that space. How wrong am I?"
] |
[
false
] | null |
[
"Pretty much yeah",
"The shape of the wing causes a low pressure system to form over the wing. This is what creates the lift that keeps the plane in the air.",
"For science: ",
"http://en.wikipedia.org/wiki/Lift_(force)#section_2"
] |
[
"if you remember basic classical dynamics, in order to create a lift upward the wing has to push something downward and air is all that is available. The fact that it is fluid dynamics does not invalidate the principle of the underlying microscopic theory.",
"He is correct."
] |
[
"The lift generation comes out from the mathematical solution of the differential equations that describe the flight phenomenon. These are the so called Navier-Stokes equations. The Bernoulli principle is an ideal subset of Navier-Stokes that cannot fully describe the actual phenomena in a lifting body or airfoil or 3D-wing. By solving the Navier-Stokes in 2D or 3D one can actual see how pressure side and suction side of a wing co-operate in order to produce lift, together with the remaining aerodynamic field (temperatures, vector velocities, entropy etc. etc.). So, in conclusion there is no straightforward explanation of \"how planes fly\" and no wrong or correct school explanations, but incomplete explanations. Only by solving the above mentioned differential equations in an appropriate grid and with the appropriate solid & boundary conditions will understand flight."
] |
[
"In the double slit experiment, why is coincidence counting needed?"
] |
[
false
] |
I know there are many different setups of this experiment. I'm referring to this one here: While I understand the overall experiment, I'm not sure what the coincidence counting is needed for. I've read elsewhere on the web that it's used to distinguish the entangled photons from stray light and background noise. However, if it's only used for that, wouldn't that in theory allow FTL communication, if we were somehow able to get rid of the noise in a different way?
|
[
"The coincidence counter is not just used to reduce noise, and is in fact critical to the experiment. This is because without the coincidence counter you will not see an interference pattern at all because the photons coming from the BBO (in contrast to coming from a single slit) are not spatially coherent . The placement of the coincidence counter acts to select a spatially coherent subset of all the photons that go through the double slit. This requires actually sending the slower-than-light signal from the coincidence counter to know which subset of photons to find the interference pattern. "
] |
[
"Thank you very much for this explanation!"
] |
[
"Coincidence counting is the only possible way to detect light / photons. Every time you detect a photon, you destroy it and thus you have created a \"detection coincidence\". This is also true in everyday life, technically you count how many photons hit your retina. "
] |
[
"Why does paneer not melt?"
] |
[
false
] |
I was cooking some food today and I've always wondered, why doesn't paneer melt? Every other cheese I can think of gets more liquidy/greasy at high temperature. Paneer gets softer but retains its original shape even when boiled or fried.
|
[
"It is a hot acid cheese where the milk is heated and acidified for curding. Cheeses like mozzarella are kept below 110F to separate casein and whey. Whey needs higher temps to colagulate so this style is mostly casein. When made around 200F like the one you are asking about the whey is incorporated into the cheese. The whey protein in the structure prevents melting to occur."
] |
[
"I don't think this is true in the case of paneer. It isn't a dry crumbly cheese. It's definitely higher moisture than something like cheddar, which melts easily. The texture of it is something like firm tofu."
] |
[
"\"When you melt cheese, you're essentially softening the milk proteins and fats to varying degrees of pliability and usability. When a cheese is heated, the protein matrix — which trapped the fats and proteins in milk and helped form solid curd when the cheese was made — collapses, encouraging the flow of cheese into a more liquid form.",
"The way a cheese melts is determined by its moisture content: low-moisture, and therefore normally drier, crumbly, harder cheeses, call for higher temperatures because they have such a concentrated formation of protein bonds that are harder to break down. When they melt, they don't flow in the same way that softer, more pliable, higher-moisture cheese does, which melts at lower temperatures and whose protein bonds collapse more easily.\"",
"http://www.thekitchn.com/cheese-on-melting-the-cheesemo-88264",
"Probably originally referenced from Harold McGee's On Food and Cooking."
] |
[
"If the Earth were flat, how far would you be able to see?"
] |
[
false
] |
Assuming that gravity and atmosphere stayed the same, would you be able to, for example, see New York from England on a clear enough day?
|
[
"I'd think it would be more of a question of ",
"scattering",
". According to ",
"Wikipedia",
" you can see about 300km in the cleanest possible sea level atmosphere."
] |
[
"Based on a human eye resolution of 1.2 arcminutes (I read that on Wikipedia), you could see the Empire State Building from about 1100 km away. "
] |
[
"Just type \"1300 feet/(angle)\" into Goolge where (angle) is the minimum resolution."
] |
[
"American Chemical Society AMA: I am Gerry Wright, Director of the Michael G. DeGroote Institute for Infectious Disease Research at McMaster University and Associate Editor of ACS Infectious Diseases. Ask me anything about antibiotic resistance and antibiotic discovery."
] |
[
false
] |
Hi Reddit! I am a Professor of Biochemistry and Biomedical Sciences at McMaster Univeristy and Director of the Michael G. DeGroote Institute for Infectious Disease Research ( ). I have been working on antibiotic resistance and discovery for over 25 years. My lab uses a combination of chemistry, microbiology, biochemistry and genomics to understand how antibiotics work, along with exploring mechanisms and evolution of resistance. We use this information to learn how to find new antibiotics and alternatives to antibiotics. I am also an Associate Editor of the journal ACS Infectious Diseases ( ), a publication that highlights how chemistry sheds light on and helps in the fight against pathogens. I am happy to answer any questions you may have on antibiotic resistance and discovery.
|
[
"How far away are we from complete resistance to current antibiotics?"
] |
[
"How much resistance is due to animal agriculture compared to overprescription/not finishing prescriptions? Does one seriously outweigh the other?"
] |
[
"Hi Dr. Wright,",
"At our current rate of growing antibiotic resistance, how long can we expect our current arsenal of antibiotics to remain effective (say, 50% of the time)? ",
"As a follow-up, how far along are we towards being able to design rather than discover antibiotics?",
"Thanks for doing this AMA!"
] |
[
"Is cancer natural, or a result of modern world pollutants?"
] |
[
false
] | null |
[
"May I know what other 'theories' about cancer you are referring to? For a start I will say yes, cancer can occur naturally even without modern world pollutants. There are many 'natural' ways for mutations to occur and that is how evolution is possible in the first place."
] |
[
"The main alternate theory she's looking at is here:\n",
"http://www.dr-gonzalez.com/history_of_treatment.htm",
"Basically, the idea (from the early 20th century) is that pancreatic enzymes are the bodies main defense against cancer. The treatment includes high doses of pig-derived pancreatic enzymes, a soecialized diet, and coddee enemas (?!). Seems like BS to me, but it's a powerful argument when coupled with the hopefulness it's packaged with! "
] |
[
"I would suggest to stick to research supported modern theories and medicine. Doctors are not perfect so if need be seek advice from more than one but please do not let 'alternative' approaches that are not backed with proper research replace modern treatments."
] |
[
"Some questions raised by a teacher..."
] |
[
false
] |
We had a substitute in math today named Dr. Handkins. He majored in both mathematics and physics for his undergrad, and minored in chemistry. He got his masters in Ministry and his Doctorate in ministry as well. He has been a pastor for 43 years now. Here are some questions he brought up: 1.) 25% of the universe is made up of known matter (protons, electrons) and 75% is made up of dark energy/dark matter that we know absolutely nothing about. Of that 25% of known matter, we know about 5% of it. So we know about 5% of the nature of the universe. Making claims on how we came about (the Big Bang) and calling it "scientific or empirical evidence" is at the very least pushing it, to me. 2.) The odds for the chain of mutations that occurred in evolution are so astronomically low that evolution seems much more complex and unlikely than God. Even with billions of years, the chances are still extremely unlikely. 3.) Scientists declare evolution like it is actual empirical evidence. When scientists talk about evolution, they turn into philosophers. For something to be real empirical evidence, it has to be able to be tested in a lab anywhere as long as the conditions are the same, and over and over you will get the same exact results. Evolution (and the Big Bang) cannot be tested. And even if it could be tested, you might not get the same results! It seems that so many atheists criticize religion for believing things with lack of evidence, but it seems like those who accept evolution are doing the same! So, that's all he said. Any answers/explanations to this? Thank you.
|
[
"He's an idiot and part of the reason why science education is failing in this country. He is not a scientist and does not understand science at all.",
"1) Just because we don't understand some of the universe doesn't mean that the parts we do understand aren't valid.",
"2) The odds that someone with his genetic code exists are so astronomically low that it seems more likely that he doesn't exist. Q.E.D., your teacher doesn't exist. ",
"3) Except you know, there is an enormous body of empirical evidence. But people like him just ignore that since they haven't ever bothered to read it. He is right that some scientists do become philosophers though, e.g. all the \"what is the evolutionary reason for X?\" questions and answers on askscience."
] |
[
"I was going to rage out at you and then I reread and realized that it was your teacher who said these things and not you.",
"Making claims on how we came about (the Big Bang) and calling it \"scientific or empirical evidence\" is at the very least pushing it, to me.",
"Calling the big bang a claim and then putting evidence in quotes is pushing it, to me. Hubble expansion, cosmic microwave background. Look them up.",
"2.) The odds for the chain of mutations that occurred in evolution are so astronomically low that evolution seems much more complex and unlikely than God. Even with billions of years, the chances are still extremely unlikely.",
"Ignoring your misunderstanding and your introduction of a non sequitur and false dichotomy, you think the odds of the universe coming into existence and eventually leading to human life are ",
" than the spontaneous existence of being who can know everything, do anything, can think, and knows Hebrew even before it supposedly created the universe? He says that redshift and CMB aren't enough evidence to support the big bang but he believes in magical wizards?",
"3.) Scientists declare evolution like it is actual empirical evidence. When scientists talk about evolution, they turn into philosophers. For something to be real empirical evidence, it has to be able to be tested in a lab anywhere as long as the conditions are the same, and over and over you will get the same exact results.",
"This person has not actually read anything about evolution. FUCK JUST DEALING WITH THIS IS MAKING ME ANGRY. Evolution is not just a historical study, it's demonstrated all the time in the lab (e.g. Lenski) and in the real world.",
"Evolution and the big bang are TOTALLY DIFFERENT CONCEPTS. One relates to biology and one to cosmology. They have nothing to do with each other. There is tons of evidence for both, this person just hasn't read any of it. Even if the world were 5000 years old, evolution would still have been shown to occur."
] |
[
"2.) The odds for the chain of mutations that occurred in evolution are so astronomically low that evolution seems much more complex and unlikely than God. Even with billions of years, the chances are still extremely unlikely.",
"The process of natural selection is ",
" equivalent to just picking mutations at random over and over again. In fact, it has such amazingly high performance compared to random selection that it is an often used technique in mathematical optimization.",
"As an example, consider the problem of trying to find the optimum travel path between the 500 largest US cities that minimizes the total distance traveled. There are an unimaginably large number of possible paths and this is an exceptionally different problems.",
"You can just select paths at random and compute your mileage, but you can grind through trillions of such solutions without getting anything good.",
"You can also mimic natural selection by computing 50 or so random paths, and then keeping the 25 best paths with the lowest mileage. You then mutate the 25 best paths randomly to get another set of 50 paths, and repeat the process. After just 1000 or so \"generations\" of pathways, you will start to see very good solutions to the problem emerge.",
"The bottom line is that natural selection will approach near optimal solutions at a blindingly fast pace."
] |
[
"Is the well known image \"March of Progress\" OK to be considered acceptable as a symbol for human evolution?"
] |
[
false
] |
Its hard to explain exactly how I mean this. I have studied some and understand much more than before how humans evolved. I know that this image has been trashed to the side by most anyone with a better understanding of evolution because it presents itself as showing evolution as being a linear progress toward the end goal. That goal being modern day human. F. Clark Howell remarked that "The artist didn't intend to reduce the evolution of man to a linear sequence, but it was read that way by viewers.… The graphic overwhelmed the text. It was so powerful and emotional" So is it actually incorrect to show an image like this depicting different stages along the history of modern day human's evolution? I only ask because this image seems to have become strongly connected to evolution. I see it on things as simple as bumper stickers, t-shirts, and even on a more serious level I have seen versions of it on covers of "On the Origin of Species" So is it acceptable to use it simply as something to symbolize evolution on a level of trying to make a statement? Like in the south where I live, the moment I see someone with this sticker on their car I immediately think to myself that's a rare treat to find another intellectual person in the bible belt that has accepted the overwhelming evidence of where we came from. Or should I think of it more as they lack real understanding of Evolution to be using this imagery to portray it. Sorry if this doesn't make any since, just trying to clarify this a little.
|
[
"Well, it's not ",
" wrong, but it's \"wrong enough\" that it's probably best not to promote its use. The modern human population does have lineage we can trace back through time, and if you followed that lineage back you'd probably see something ",
" resembling what you see in that image, going from right to left.",
"But if you walked through time from left to right, starting with the chimpanzee-like thing",
" on the left, you wouldn't see a straight progression to the human on the right. You'd see tons of branches shooting off at various points as populations split from one another and started evolving independently, many of them wouldn't make it to the present (i.e. they go extinct), and some of them might come back together and merge with one another after spending only a brief time apart (as non-African ",
" seem to have done with a population of Neanderthals (",
"Green et al, 2010",
", ",
"Yang et al, 2012",
"), and as the ancestors of modern Melanesians seem to have done with Denisovans (",
"Reich et al 2010",
")).",
"Someone driving around with that image on their bumper sticker probably accepts evolution, which is great. But they probably don't ",
" understand it on a deep level, because depictions like that are gross oversimplifications that really take all of the interesting bits out of evolution and distill it into this strange anthro-centric notion of \"progress\", which really isn't what it's about at all. A ",
"phylogenetic tree",
" serves as a much better symbol to represent evolution, because that's actually what the process looks like, and if we can get people to understand that, I think we'll have a much easier time showing them what evolution is really all about."
] |
[
"\"The march of progress is the canonical representation of evolution – the one picture immediately grasped and viscerally understood by all.... The straitjacket of linear advance goes beyond iconography to the definition of evolution: the word itself becomes a synonym for progress.... [But] life is a copiously branching bush, continually pruned by the grim reaper of extinction, not a ladder of predictable progress.\"",
"-Stephen Jay Gould, ",
"Gould really didn't like it; I believe there was also an entire other essay about his views on it. I would recommend you read ",
" if you haven't already. Sweet book.",
"In general, there is other iconography I think should be preferred. As written, the linear progress icon is bad because it does misinform and confuse. But it is probably fine to use in some circumstances. "
] |
[
"I couldn't agree more. I think its an image that will forever at least drive the conversation toward a discussion about evolution. And I don't care how small the knowledge an individual has or how set in their views against evolution they are, there is no way that any amount of discussion is a bad thing. I'll take every opportunity I can get to share what I've learned and hope it can lead to someone accepting the facts offered up.\nI just know that I have gotten a little flack from a few of my other intellectual friends about the depiction because the history of inaccuracies it relates to. \nI still think it is striking imagery. I definitely don't believe that it shows that humans are the end goal, and if anything to me it gives me a chance to discuss why that wouldn't be correct."
] |
[
"What's the average temperature in the universe?"
] |
[
false
] | null |
[
"Are you talking about the average temperature of the matter in the universe? Or the average temperature of the radiation we observe?"
] |
[
"The average temperature over the course of the universe's lifetime is 2.73K, which equates to -270C or -454F, according to ",
"this article"
] |
[
"Average over space, the minimum/lower limit of the average temperature is the temperature of the Cosmic Microwave background with 2.73K. But there are galaxies, stars, hot gas around, so the average is going to be higher than that. ",
"When we average over time as well, <T(r,t)>, that's probably gonna be even higher. The universe was a much hotter place. "
] |
[
"Are any physical constants a power of 2?"
] |
[
false
] |
I've been fiddling with this problem for a while now, and I'm stuck because our units are mostly arbitrarily defined. My original goal was to find out if the speed of light was a power of two. I assume and would work as units, but given that these values are derived using the speed of light (where one Planck length divided by one Planck time is equal to the speed of light), I can't use them to solve it.
|
[
"If you use Planck units then many physical constants are 2",
" ."
] |
[
"There are dimensionless and dimensionfull constants. The latter have values that change depending on what units you express them in, so you could just jigger your units until something looks like a power of two, but that's not very meaningful.",
"Dimensionless constants, or ratios of dimensionfull constants, have values that can be compared to powers of two. The fine structure constant is close to 1/137, the proton-electron mass ratio is around 1800. There's a weird phenomenon where the sum of the lepton masses divided by the square of the sum of the square root of their masses is eerily close to 2/3, and nobody knows if it's a coincidence or not.",
"But there's nothing I can think of that's a power of two. If there is it's likely not due to some deep reason that we know of."
] |
[
"In plank units the speed of light is 1. (That's a power of 2, but not a particularly exciting one.)",
"2 as the base of a logarithm is a fundamental notion in information theory.",
"2 is also the size of the 'spin space' for spin-1/2 particles - for example there are two 'electron slots' per orbital, similarly, there are two types of chirality in 3 dimensions."
] |
[
"Would the trans-atlantic cable still be in existence?"
] |
[
false
] |
It was laid so long ago, Has anyone looked for it? Is it too deep or the currents moved it? Or has the saltwater corroded it into dust? Sorry if this may not be a suitable question for
|
[
"The transatlantic telegraph cable was insulated by ",
"gutta-percha",
". Wikipedia is lacking in detail, but from my Bell labs book (The Idea Factory) and ",
"here",
", the ",
"Teredo Worm",
" and several other species attacked gutta-percha. The steel wires and copper conductors will also have corroded by now, and will be covered in a thick layer of biological gunk. The copper may have had a detrimental effect on life around it. I don't know about ocean currents moving it, but I doubt it as the cable was quite heavy.",
"The cable that Bell laid, the ",
"TAT-1",
", is retired but could still plausibly be intact. It's polyethylene with good wire armor, making it quite unpalatable, and its shielded electrically so sharks never took an interest in it (which could create a weakness). "
] |
[
"Sharks have what is known as electroreception. Basically the ability to sense electric fields. Living beings have electric fields too. You do the math on that one :)"
] |
[
"Parts of the Atlantic that the cable crossed are so deep that decay happens very slowly. Witness the Titanic. I'm sure that it is still down there, although the condition is undoubtedly poor.",
"Fun and somewhat related fact, the wreck of the feared German WW2 battleship Bismarck has actually had a newer trans oceanic cable laid across it. "
] |
[
"How does the Aristotle's lantern (the jaw apparatus found in a sea urchin) work?"
] |
[
false
] |
Hello! I'm a non-scientist (obviously!) who is currently working on a design project. While doing my research, I came across the structure of the mouth of the sea urchin (known as Aristotle's lantern) and I'm really fascinated. I tried to read more about it on the internet, but due to my non-science background, I have trouble understanding it. Can somebody please explain to me how does the mouth of a sea urchin work? How is it formed structurally? What is the mechanism behind the movement? How is it held together? Thank you very much :))
|
[
"Aristotle's lanterns are, at least in my opinion, some of the coolest and most unique structures in nature. I first learned about them in detail during my undergraduate invertebrate zoology course, where I also got the chance to ",
"dissect a sea urchin",
" (warning: potentially gross I guess). You can see the Aristotle's lantern pulled out in the bottom left, next to the empty upper half of the sea urchin test.",
"Like most aspects of echinoderm anatomy, Aristotle's lanterns are pentaradially symmetrical, consisting of ",
"five pyramidal \"jaws\"",
" (each of which has a single \"tooth\"). These are composed of calcium carbonate, the same material as the other hard parts of a sea urchin. The teeth ",
"all come together",
" at the entrance to the mouth, and the whole structure is held in place with ",
"muscles and connective tissue",
", and they typically open and close as one unit as you can see in ",
"this video",
". If you want to get into specifics, check out ",
"Carnevali et al. 1993",
" which discusses the skeletal and muscular structure of one species in great detail. Also, just for fun I wanted to link this paper I came across by ",
"Frank et al. 2016",
" which presents a design for a ",
"soil sampling device",
" inspired by the Aristotle's lantern, which is pretty neat."
] |
[
"Thank you so much for the detailed explanation, it really helped me a lot! Also the soil sampling device is very interesting :)"
] |
[
"Was this course at Friday Harbor, by chance?"
] |
[
"Are blood transfusions between species possible?"
] |
[
false
] | null |
[
"Yes, in some cases, it just depends on whether or not the recipient has any antibodies against the donor blood.",
"\nBest example of this is dog blood being transfused into cats. Cats can receive a one time transfusion from a dog in a emergency. \nHere is review article about this subject:\n",
"https://www.ncbi.nlm.nih.gov/pubmed/22983454"
] |
[
"Yepo. I've had about 12 patients undergo xenotransfusions (cats getting dog blood). All did fantastic for the transfusion itself, though the underlying disease process was sometimes fatal. ",
"This is a procedure most vets are still too nervous to do, but being a medicine resident at an exceptionally busy hospital means I get to do cool things. "
] |
[
"Hyperliteralism aside, no, blood from one animal is generally not compatible with another animal.",
"If someone receives incompatible blood in a transfusion, it means that the recipient's immune system doesn't recognize the antigens (sort of molecular surface features, determined by genetics) on the donated blood cells. The immune system then reacts to destroy the foreign cells by producing antibodies against them. ",
"Different antigens within a species are the reason why there are different blood groups, and even though a type A recipient and type B donor are both human, their blood isn't compatible for transfusion. ",
"Different animal species have different antigens too, so no antigen present on, say, a cat's red cells would survive transfusion to a human body. The human immune system would destroy those cells.",
"One \"successful\" transfusion of sheep's blood to a human (i.e. the recipient didn't die) was done in 1667 but nobody was ever able to replicate it. Further experiments always resulted in sicker or dead recipients. We've understood the idea of antigens for a little over a hundred years and that model explains why putting sheep or cow blood into a human never worked very well.",
"Sources: ",
"http://www.smithsonianmag.com/smart-news/350-years-ago-doctor-performed-first-human-blood-transfusion-sheep-was-involved-180963631/",
"and my blood bank class from lab tech school. ",
"(ETA clarification of \"successful\" blood transfusion.)"
] |
[
"Why do bug bites itch?"
] |
[
false
] | null |
[
"The short answer is ",
". The longer answer will seem unnecessarily complicated, so I've included some citations.",
"Pruritus (itching) as a cutaneous sensation (typically characterized as unpleasant) is frequently associated with irritation/damage secondary to dermatological conditions, systemic disorders [generalized] and insects/infestations [localized]. (Beers, et al., 2006)",
"-Skin Conditions: Seborrheic Dermatitis, Atopic Dermatitis, Folliculitis, etc",
"-Systemic Disorders: Diabetes, Hypothyroidism Chronic Kidney Disease, etc",
"-Insects: Mosquitoes, Sarcoptic Mange (Scabies), Pediculosis Capitis (Head Lice), etc",
"Itch receptors are unmyelinated, penicillate nerve endings (C-polymodal) located in the skin (superficial epidermis: free teleneuron), mucous membranes and cornea. 'Itch' is transmitted via dorsal root ganglion (no spinal reflex, unlike pain). Direct activators would include: Histamine, Acetylcholine, Bradykinin, Serotonin, Endothelin - with prostaglandins (Histamine potentiation) and interleukins playing a role in itch elicitation [IL-2, IL-4, IL-6], etc. (Ständer, et al., 2003; Song, et al., 2018)",
"A useful way to conceptualize pain (and itching), is via circuitry (see: ",
"Melzack and Wall",
", 1965) - To quote Sapolsky:",
"\"Neuron A’s dendrites sit just ",
"below",
" the surface of the skin, and the neuron has an action potential in response to a painful stimulus. Neuron A then stimulates neuron B, which projects up the spinal cord, letting you know that something painful just happened. But neuron A also stimulates neuron C, which inhibits B. This is one of our feed-forward inhibitory circuits. Result? Neuron B fires for a while and then is silenced, and you perceive this as a sharp pain—you’ve been poked with a needle. ",
"Meanwhile, there’s neuron D, whose dendrites are in the same general area of the skin and respond to a different type of painful stimulus. As before, neuron D excites neuron B, and the message is sent up to the brain. But it also sends projections to neuron C, where it inhibits it. Result? When neuron D is activated by a pain signal, it inhibits the ability of neuron C to inhibit neuron B. And you perceive it as a throbbing, continuous pain, like a burn or abrasion. Importantly, this is reinforced further by the fact that action potentials travel down the axon of neuron D much slower than in neuron A (having to do with that myelin that I mentioned earlier—details aren’t important). So the pain in neuron A’s world is not only transient but also fast. Pain in the neuron D branch not only is longlasting but also has a slower onset. ",
"The two classes of fibers can interact, and we often intentionally force them to. Suppose that you have some sort of continuous, throbbing pain—say, an insect bite. How can you stop the throbbing? Briefly stimulate the fast fiber. This adds to the pain for an instant, but by stimulating neuron C, you shut the system down for a while. And that is precisely what we often do in such circumstances. An insect bite throbs unbearably, we scratch hard right around it to dull the pain, and the slow, chronic pain pathway is shut down for up to a few minutes.\" (Appendix 1, 2017)",
"2018",
"2003"
] |
[
"So itchiness is a subconscious interpretation of pain?"
] |
[
"Depends on what you mean by subconscious, but for practical purposes...yes. ",
"This",
" paper is a good overview if you're interested in liminality."
] |
[
"Everyone knows that sharks can smell blood in the water. But are there any air-breathing animals that can smell underwater? Or water-breathing animals that can smell in the air?"
] |
[
false
] | null |
[
"Otters blow bubbles with their nostrils underwater as they stick their nose in potential food. They then suck the bubbles back in, in-order to smell if the thing they are investigating will be tasty. It’s pretty cool."
] |
[
"Star-nosed moles can smell and identify prey underwater. They also hold the record for fastest eater of prey. Also they are terrifying"
] |
[
"This is also done by the star-nose mole.",
"EDIT: here's a video! The underwater smelling is at the end.",
"https://youtu.be/fio1NUxszhY"
] |
[
"What makes metals metal?"
] |
[
false
] |
With regards to elements, how is metal defined and what makes some but not other elements metal, without much 'pattern' to it? (In that after Hydrogen and helium in periodic table, there's 2 metals, then some nonmetals, 3 metals, some nonmetals, then a lot of metals etc, but all with inconsistent amounts in each cluster)
|
[
"There are no strict definition, but generally metals have de-localized outer electrons and thus high electric and thermal conductivities. ",
"Metalloids have some metallic properties and some non-metals become metallic under high pressure. Which elements are classified as metals, metalloids or non-metal are matters of convention, and some are disputed."
] |
[
"Remember that the periodic table is a tool created by people, not a universally perfect arrangement of elements. So the lack of a pattern is because the periodic table was not arranged in such a way to prioritize the grouping of metals together.",
"Basically, metallic elements easily form cations (readily lose electronics), which also makes them highly conductive in contrast to elements which do not readily lose electrons at all (such as the noble gases) or tend to form anions."
] |
[
"If you're asking why there's no transition metals until the third row, that's because the s and p shells fill up twice before it's more favorable for a d shell to fill up. After the d shell fills you get metalloids, as the shells get higher energy down collumns they get more mettalic as the electrons start to be shared between atoms more.",
"What makes metals have mettalic characteristics(reflective, good conductors, tend to form positive ions,) is that as you go right on the periodic table, atoms tend to attract electrons more(are more electronegative). That's why things like oxygen and flourine are very easily reduced(all of the time it's referred to from the perspective of the organic molecule though), because it's easier for them to get a full octet.",
"All of this is because the positive charge is essentially becoming more concentrated for the availible energy levels as you go across the table. So you get differences in atomic width and electron affinites, which gives us chemistry.",
"http://en.wikipedia.org/wiki/Electron_configuration"
] |
[
"What technological obstacles need to be overcome to make solar energy viable?"
] |
[
false
] | null |
[
"As far as I see it, there are 3 major issues with solar energy. ",
"Initial cost- Solar panels aren't cheap. And while they do pay for themselves over a long period of time, it can take 10-15 years for a solar panel to have paid for itself. For many consumers, this period of time is too long for the payoff to be major as those that do own their own home don't have the guarantee that they'll be living in that home 10+ years from now to reap the benefits. As solar panel cost drops and their efficiency rises, solar power will continue to gain in popularity.",
"Energy storage- Energy storage may be the biggest reason that solar still has a way to go. To store the energy required to power a home or business through a night is costly. To store it in a way that you will continually be recharging and discharging that storage while not rapidly losing capacity is technology that is still being discovered. Add to the fact that whatever storage method used has to be designed to handle large fluctuations in power and you're in a very interesting situation. Frankly, we just don't have this technology yet, but the work being done in the fields of batteries and capacitors right now is leading to rapid advancements and we may soon have our answers for power storage.",
"Aging power grid- Right now, many countries power grids are beginning to show their age, and with it, their poor design and lack of efficiency. To truly feel and see the benefits of solar power, we'll need to centralize our power generation and have those areas that capture the greatest quantities of sunlight become \"power hubs\" for producing our energy. To be able to send that power from a hub to a distant place though is impossible using the current power grids available in many countries (with the US being a prime example of aging power grid). ",
"TLDR- Cost, storage, and old power grid are keeping solar from being more efficient.",
"NOTE: I'm at work and realize this is a garbled mess of english. I'll try to remember to come back and edit this at some point today. If not, I'm sure the comments about how I suck at English will remind me. "
] |
[
"At this point, money and political will are the only obstacles. See ",
"this",
" paper that just came out."
] |
[
"Inexpensive batteries.",
"Solar panels work well, but only when the sun is shining. Large scale power systems need to match power generation to power consumption. The only practical way to do that with solar energy is to store the excess energy somehow and retrieve it when needed."
] |
[
"What cells in my body are making the spike protein after I get an mRNA vaccine?"
] |
[
false
] |
Is it all of them? Just the cells in the muscle that they injected into? Or is just white blood cells?
|
[
"Both the Pfizer/BioNTech and Moderna vaccines are being given i.m., so if you’d like to know what parts of your body are producing the coronavirus Spike protein antigen, the answer seems to be the muscle tissue at the site of injection, the lymphatic tissue downstream in your armpit on that side, your spleen, and (for the first day or two) your liver. The bulk of the Spike that you’re going to make is probably made in the first two or three days, anyway, from what we can see from the animal models.",
"—",
"mRNA Vaccines: What Happens",
" from Derek Lowe’s In The Pipeline, Jan. 2021",
"He got that summary from these papers: ",
"Unmodified mRNA in LNPs constitutes a competitive technology for prophylactic vaccines",
"Induction of Robust B Cell Responses after Influenza mRNA Vaccination Is Accompanied by Circulating Hemagglutinin-Specific ICOS+ PD-1+ CXCR3+ T Follicular Helper Cells",
"Preclinical and Clinical Demonstration of Immunogenicity by mRNA Vaccines against H10N8 and H7N9 Influenza Viruses",
"A COVID-19 mRNA vaccine encoding SARS-CoV-2 virus-like particles induces a strong antiviral-like immune response in mice",
"The lymph nodes and spleen will be the most important sites for driving the immune response, especially in the first dose - the booster may have more widespread activity."
] |
[
"Because that’s how the immune system works."
] |
[
"Wow. Thanks for the write up!"
] |
[
"Does killing a stray ant in the home decrease the likelihood that more ants will appear in the future?"
] |
[
false
] |
Every now and then I see small ants in parts of my house. They are tiny and unobtrusive so I wouldn't mind letting a few just go and do their thing. But I also want to avoid a large number of ants appearing some day. When I've seen isolated ants, I've killed them under the belief that doing so would decrease the likelihood of a large number of ants eventually following after them. I base this on the idea that ants leave behind chemical trails that can encourage other ants to follow in their trail. But like I said, for just a few ants here and there I don't mind them and would rather not kill them if I didn't have to. So, is it true that killing a few isolated ants here and there would make it less likely for a bunch more to follow in their trails later on?
|
[
"Ants leave scent trails to find their way and guide other ants, so killing one ant won't necessarily stop others from following, but it will impede the progress of their exploitation into your home. ",
"http://icouzin.princeton.edu/pheromone-trail-networks-in-ants/"
] |
[
"So even if large numbers of the ants that go to a place never come back, they don't stop trying to explore there? That must be ",
" convenient for ant eating predators"
] |
[
"They tend to go where the strongest scent is. An ant that goes and returns by the same trail effectively leaves two layers. Every other ant that follows the same path leaves a thicker trail. ",
"One path, followed only once is a relatively faint scent. "
] |
[
"If it is believed that Mars lost its atmosphere because it lost its magnetic field & lost its protection against solar winds/storms, why does Venus have such a thick atmosphere since it too has no intrinsic magnetic field to protect from the sun & is closer to any solar storm?"
] |
[
false
] |
I mean, Venus had such a think atmosphere, thicker than Earths & is so hot around the entire thing, yet is a similar size. It just baffles me that Mars potentially lost its atmosphere because no magnetic field, yet Venus never did. Finally, does Earth actually need a magnetic field to keep its atmosphere protected from solar winds? Or are there just different mechanisms to protect an atmosphere & Earth’s happens to be a magnetic field?
|
[
"It would appear that Venus’ atmosphere actually shields itself. As the solar wind interacts with the ionosphere, the charges particles can induce a magnetic field similar to earth’s and protect the lower layers of the atmosphere. Here’s an article explaining it.\n",
"https://www.jhuapl.edu/NewsStory/210603-Solar-Orbiter-unveils-new-details-Venus-magnetosphere"
] |
[
"I'll start with what is probably the biggest factor. Volcanoes on Venus have spewed out a lot more CO2 (and other gases) than those on Mars.",
"Terrestrial planets would have started with a primary atmosphere primarily made of hydrogen and helium accreted from the solar nebula. But the terrestrial planets were (and are) too small and hot to retain these light gases, so the primary atmosphere was lost to space. A secondary atmosphere, mainly CO2 and nitrogen, with other gases like water vapor, was outgassed from the interior, both from the early magma ocean, and once a solid surface formed, from volcanoes. Volcanic activity has continued, to differing extents, to add gases from the interior over the following billions of years. Mars, in large part due to being smaller and so cooling faster, probably had a much steeper drop off in volcanic activity billions of years ago., with only occasional eruptions in geologically recent times. Another possible factor is that Mars may have ",
"formed with far fewer volatiles",
" to outgas than Earth or Venus. Earth and Venus have maintained higher levels of activity for longer. We don't know when or how quickly Venus's atmophere became so thick, but even the \"original\" secondary atmosphere from initial outgassing probably wasn't that thick to begin with.",
"Why then does Earth not look like Venus? Earth has an active and (mostly) closed carbon cycle (and nitrogen and water cycles). Most of the CO2 emitted by volcanoes dissolves in water to make carbonic acid. This acid chemically weathers rock, especially the frozen lava, dissolving metal ions such as calcium into the water. In the oceans, calcium and carbonate ions precipitate out of the water to form carbonate rocks such as limestone, sequestering the carbon. (Photosynthetic life evolved and used water and atmospheric CO2 to make biomass and oxygen gas, forming our tertiary oxygen-rich atmosphere. The formation of fossil fuels also sequesters some carbon.) Subduction of oceanic plates, a key part of plate tectonics, returns much of this carbon to the interior, where it can be re-outgassed. Venus obviously no longer has oceans or much of a water cycle, so the carbon it spews out stays in its atmosphere. Venus also doesn't currently appear to have as much, if any, subduction as Earth. Whether Venus has, or ever had, subduction and plate tectonics or something similar is an open question, but without water it can't store or recycle much CO2 anyway.",
"On magnetic field and atmospheric escape:",
"The interactions between various magnetic fields and planetary atmospheres are, to say the least, complex. Over the past few years especially, the idea that planets need an internally generated magnetic field in order to retain an atmosphere has been undergoing somewhat of a paradigm shift. As once recent (and warning, long PDF) ",
"review paper",
" concludes in its key points: \"A magnetic field should not be a priori considered as a protection for the atmosphere.\"",
"Both Venus and Mars have a weak global magnetosphere induced in their outer atmospheres by the solar wind. This leads to many of the effects of Earth's strong internally generated field, but to a lesser degree. Mars also used to have an internally generated magnetic field, which magnetized rocks in its crust. Many parts of the Martian crust, especially in the southern hemisphere, still retain this remanent magnetization, producing regional magnetic fields of surprising strength. (And no, Mars' dynamo did not shut off because the core froze, and the planet spins nearly as fast as Earth. The InSight mission ",
"confirmed that Mars' core is molten",
". This in and of itself was not surprsing; it was the expected result based on decades of research. But the molten core must be convecting to maintain a dynamo.)",
"Wikipedia has an overview of the major ",
"atmospheric escape",
" processes. Of note, while a magnetic field protects from sputtering escape and charge exchange escape caused by the solar wind, it also directly contributes to polar wind escape. For Earth, with a strong magnetic field, the magnetic field appears protective on the balance. But as ",
"Gunnell et al. (2018)",
" find, over a wide range of magnetic field strengths, particularly magnetic fields weaker than Earth's, the balance can be in the other direction. Magnetic fields can lead to greater loss. For Mars in particular, this conclusion is supported by ",
"Sakata et al. (2020)",
"--described in ",
"this Eos news article",
". On that note, those remanent crustal magnetic fields of Mars have a tendency to pinch off blobs of atmosphere into the solar wind.",
"Going beyond magnetic fields, the next thing people typically mention are thermal escape processes, or often just indirectly as \"gravity\" (but temperature is also important). In short, gas atoms/molecules have a distribution of velocities that corresponds to their mass and temperature. Lighter gases and higher temperatures correspond to higher velocities on average. At high temperatures and low gravity, the upper end of the distribution can stretch above the escape velocity and a portion of remaining gases continually escape. This is occurring in the upper atmosphere, particularly near the base of exosphere (exobase), and the temperature there is what matters, not the surface temperature (the same technically goes for escape velocity, but that's not going to be much different from the surface value).",
"But if you look at a plot like the ",
"one on the aforementioned Wikipedia page",
", Mars (like Earth and Venus) has low enough temperature and strong enough gravity to retain a CO2-nitrogen atmosphere. None of the terrestrial planets are capable of retaining hydrogen or helium. (So when solar UV ionizes water vapor, the hydrogen atoms are lost much more easily than the oxygen. With their oceans evaporating/sublimating into the atmosphere, and lacking an ozone layer like Earth, Venus and Mars are more susceptible to water loss this way.) So gravity, or more properly thermal escape, is not really a good explanation for why Mars has such a thin atmosphere.",
"Current loss rates for Venus, Mars, and even Earth are subject to uncertainty, but are all similar, roughly on the order of just under 1 kg per second (Venus) to a few kg per second (Mars), or ~30,000-100,000 metric tons per year. Mars is not losing atmosphere significantly faster than Earth. Lest those numbers seem like a lot, Earth's atmosphere is over 5*10^15 tons, while Mars' is ~2.5*10^13 tons. Atmospheric loss is generally a very slow process (at least around stars that aren't extremely active or rapidly expanding). Also, the vast majority of atmospheric losses are hydrogen (mainly from the photodissociation of water vapor). A distant second/third are oxygen ions (from photodissociation of water vapor and CO2) and helium (from alpha decay of radioactive elements in rocks). Very little nitrogen and carbon/CO2 escape in comparison.",
"Why and when Mars lost much of its atmosphere, and how much it actually lost, are still very active areas of research and any specific answers will likely change over even the next few years. But as far as why Venus' atmosphere is so much more massive than Earth's, let alone Mars', that can be mostly attributed to Venus' volcanic outgassing and practical lack of a carbon cycle."
] |
[
"That is known as an induced magnetic field, and exists in plenty of bodies throughout the Solar System. It contributes slightly to the retention of the Venusian atmosphere, but then it should have had the same effect when Mars had an atmosphere. ",
"As far as I understand it, the number one factor for atmosphere is retention is always the mass of a body and the corresponding strength of its gravity field. Venus having a similar mass to Earth manages to keep its atmosphere. Mars having a lower mass than either was always doomed to lose its atmosphere, magnetic field or not. ",
"The picture gets a lot more nuanced when all factors are considered, ie. distance from host star, strength of the solar wind, strength of an intrinsic magnetosphere (be it from the body itself or from the planet it’s orbiting), strength of any ",
" winds (which serve to leak atmospheric particles out from unconnected magnetic field lines), outgassing history, large impact history, etc. An excellent discussion of all that from the leading experts on evolution of planetary atmospheres can be found ",
"here",
". Gravity and exobase temperature seem to be the biggest factors in which gases can be retained in an atmosphere long term."
] |
[
"Recently been interested by how the allies decrypted the German communications during world war 2. Can anyone answer these two questions?"
] |
[
false
] |
Hi all, I'm not sure if this is the right sub for cryptography but I can't find anywhere else to ask it. I recently visited bletchley park and looked around the codebreaking exhibits. However there are two things that I don't get... The British had enigma machines before the war as they were used in banks for encryption. The Nazis sent an identifier at the start of each message that told the receiver what to set the dials to. Why did the allies not just set an enigma machine to those settings and decode it? After the Germans changed to using the Lorenz cypher the first task was to understand how the cypher worked. While I cannot get my head around how insanely intelligent these men must have been to do this, I can see the process. What I don't get is how they then broke codes. Apparently they picked common words like eine or heil and added these to the encrypted message. I get how the addition of letters worked but how did this give them an answer? What then did the Bombe / colossus do with the information the cryptographers got from this? If adding these common words to the encoded message gave them the cypher key then what is the need for the computer?
|
[
"I can't speak to your second question, but I can answer the first: The Nazis did not send an identifier like this at the start of each message. The daily Enigma settings were distributed monthly on sheets of paper. Unless the Allies could get their hands on these sheets (which they occasionally did), there was no way to know what enigma setting to use."
] |
[
"Hmm, the exhibits at the park said differently"
] |
[
"Apparently they picked common words like eine or heil and added these to the encrypted message",
"It was more like, they assumed those words would appear somewhere in the message and used that to narrow in on certain encryption settings that are consistent with the appearance of those words.",
"There was a ",
"good youtube video",
" discussing how this worked."
] |
[
"How do psychologists distinguish between a patient who suffers from Body Dysmorphic Disorder and someone who is simply depressed from being unattractive?"
] |
[
false
] | null |
[
"To answer that question, you must know that Body Dysmorphic Disorder (BDD) is a compulsive disorder, in the same family as OCD. A diagnosis of BDD features a prominent obsession with appearance or perceived defects, and related compulsive behaviors such as excessive grooming/mirror-checking and seeking reassurance. Keep in mind, these behaviors occur at a clinical level, meaning it is not the same as simply posting a 'fishing' status on Facebook; it's markedly more frequent and severe behavior.",
"The differential diagnosis between BDD and Major Depressive Disorder (MDD) focuses on the prominence of preoccupation with appearance and the presence of compulsive behaviors. While appearance can be a factor in MDD, an individual with BDD will be markedly more concerned with appearance and will exhibit the aforementioned compulsions. ",
"It should also be noted that MDD is commonly comorbid with BDD, meaning that they are often diagnosed together. BDD often causes individuals to develop depression. In these cases, however, the diagnostic criteria for ",
" disorders are met."
] |
[
"Awesome and thorough explanation. ",
"How’s the DSM-V? I was still using the IV when I practiced. "
] |
[
"Well, my center still technically uses the DSM-IV for coding, though we use the ICD-10 more commonly. ",
"I've just tried to get myself up to date on the DSM-5 for when we inevitably switch over."
] |
[
"Can someone explain why big bang theory is not an explanation of the creation of the universe but rather only the expansion"
] |
[
false
] |
Also what are some theories of the creation of the universe?
|
[
"It is not the goal of science to explain creation. Science wants to explain observable phenomena. We observe expansion, the Big Bang theory explains that. It is not like some scientist sit down on a Monday morning and decide that they should try to explain where everything came from.",
"Some people do hypothesize about possible solutions to current problems in cosmology which may imply some sort of Big Bounce scenario, but that is currently all speculation."
] |
[
"First cause is an unanswerable question; the big bang theory merely explains what happened after the big bang, not what caused the matter to be there in the first place. "
] |
[
"It is not the goal of science to explain creation.",
"What? I'm sure a lot of scientists would love to know how the universe was created. "
] |
[
"Can someone please simply put the 2nd law of thermodynamics?"
] |
[
false
] | null |
[
"Assuming you googled and wiki'd that \"heat cannot flow from cold to hot without external help\" or \"heat cannot be converted to work 100%\", what do you mean by simply put? "
] |
[
"The second law of thermodynamics states that for any spontaneous process, entropy increases.",
"Basically, if something can happen without you putting work into the system, the disorder in the system increases.",
"A good example: say I have a cup of really hot water. If I drop an ice cube into the hot water, the cube will melt. The process of the cube melting is ",
". The 2nd law states that this spontaneous process results in an increase in entropy, or an increase in disorder.",
"So, for any spontaneous process, the entropy, S, must increase. The mathematical formalism of this law is Simply S > 0, where S is entropy."
] |
[
"the universe is always moving toward a greater state of disorder"
] |
[
"Other than lightning strikes and lava, how do fires occur naturally?"
] |
[
false
] | null |
[
"Well it's dependant on a fire already burning elsewhere but raptors in Australia have been noted to carry burning twigs to start new fires to flush out prey:",
"https://www.iflscience.com/plants-and-animals/australian-birds-of-prey-have-harnessed-the-use-of-fire-to-flush-out-their-prey/"
] |
[
"Why am I not surprised that Australian wildlife is using fire to kill even more."
] |
[
"It'd be a pretty unlikely event to occur in nature. Hay bales combust because they're packed tightly when damp,which allows bacteria that's exothermic to grow in the inner damp bits. They catch on fire when either the heat gets high enough to light the outer dry straws. I don't think there's be many non agricultural scenarios where that much grass is stored in one place, though now I wonder if some rodents use that technique to heat their dens."
] |
[
"Do Prions exists among reptiles and birds?"
] |
[
false
] |
There is research that speculates that prions in mammals can arise because of cannibalism. Reptiles and birds are notoriously cannibalistic.
|
[
"Mammalian prions do not arise because of cannibalism, but can be spread by cannibalism.",
"Anyway, the prion-forming protein in humans is also found in nearly every other vertebrate, birds and reptiles included. However, prions are only known to cause disease in mammals. The reason is unknown.",
"http://biology.unm.edu/toolson/biotox/presentations/evolution.html",
"There are also unrelated prion-forming proteins in several species of fungus."
] |
[
"I'm not sure if the specific mechanism is known yet, protein folding disorders are pretty tricky to determine the root cause of, especially when they're very rare. Here is a short review on general details of protein misfolding:",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3330701/#__ffn_sectitle",
"To put it short and sweet, protein folding depends on the sequence of amino acids it's made of. The amino acids have different side groups which may be basic, acidic, etc, which take up space or repel each other, attempt to face towards or away from the environment the protein is in and more. These interactions are affected by loads of variables - the pH of the environment, the osmolarity of the environment (amount of fluid vs things dissolved in it), whether or not other proteins interact with it, heat, and much much more. If any of the factors are changed from normal cellular homeostasis, the protein might become more likely to fold a different way than usual.",
"Additionally, when some proteins become misfolded, there's evidence that some kinds of prions induce misfolding in properly folded proteins when they come in contact. It seems possible that the prions have hydrophobic residues sticking out where they shouldn't be, so when the prion bumps into the normal protein, the hydrophobic bits in prions try to \"shelter\" from the cell environment, so the normal protein almost gets dragged out of shape, surrounding hydrophobic prion residues with its own hydrophobic residues, causing the protein to turn into a prion."
] |
[
"If there's anything that wasn't clear or got a bit technical let me know! I can try to adjust my explanations if you want.",
"I get you on the anxiety - learning all this stuff makes me equally paranoid and calm, because I learn a lot of stuff based on genetic and progressive diseases, so I both know what signs to be freaked out about and what is probably nothing too major. At the same time it's frightening to think of all this going on within me every second!",
"I'm in my final year of a biochemistry undergrad degree, so this stuff is more or less in line with what I do day to day! Lots of looking at diseases, looking at protein structure, function and interaction, and lots of applying techniques and methods to study this stuff. It's pretty cool, I enjoy it a lot! Feel free to contact me if you're studying more biological/biochemical stuff!"
] |
[
"Why are anticonvulsant medications used as mood stabilizers too?"
] |
[
false
] | null |
[
"PhD student in neuroscience here. That is a fantastic question, and quite honestly one that neuropsychiatrists are very much still attempting to answer. General consensus, and still very surface level is this:",
"Your brain is an electrochemical system, with tiny proteins known as ion channels. These ion channels open and close to let chemical species (ions such as potassium, sodium, chloride, calcium) in and out. The organization and types of ion channels govern how the cell responds and what it's electrical activity behaves like. So with epilepsy, one deficit is hyperexcitability driven by a balance mismatch of excitation and Inhibiton, the big control system in neural networks. To correct this, certain channel or receptor enhancers or blockers may be applied in a drug form.",
"Now these drugs are not targeted yet. So imagine trying to fix your car by completely drentching it in motor oil instead of applying it exactly where we need it to be. This is a similar situation in neuropharmacology. So it's possible that an anticonvulsant might trigger channels and receptors involved in mood disorders.",
"This is most often found by accident as we are still relatively uniformed behind the exact mechanisms of these complex disorders. ",
"This isn't to take away from the fact that these are life saving drugs. We are still very new to understanding and treating neuropsychiatric disorders.",
"Hope this helps!"
] |
[
"Further to ManNotTheBear's comments, many drugs are marketed with one indication but are then found to be effective for other indications in post marketing studies. One such example of this could be codeine. We use codeine to treat pain but it also causes respiratory depression and constipation - so in the UK it has marketing authorisation to treat ",
"persistent cough and diarrhoea",
". For codeine this is because the opiate receptors that it targets in the central nervous system are found elsewhere in the body too (e.g. in the gut).",
"",
"Anti-convulsant medications work by reducing seizure threshold (i.e. they don't treat epilepsy's cause), usually through modulating ion channels (e.g. voltage gated sodium channels). Interestingly, the manufacturer of a lamotrigine product states they know how the anti-convulsant effects work, but not how it acts on bipolar symptoms, ",
"here's an extract from the manufacturer",
": ",
" ",
"Pharmacotherapeutic group: other antiepileptics, ATC code: N03AX09. ",
"Mechanism of action ",
"The results of pharmacological studies suggest that lamotrigine is a use- and voltage-dependent blocker of voltage gated sodium channels. It inhibits sustained repetitive firing of neurones and inhibits release of glutamate (the neurotransmitter which plays a key role in the generation of epileptic seizures). These effects are likely to contribute to the anticonvulsant properties of lamotrigine. ",
"In contrast, the mechanisms by which lamotrigine exerts its therapeutic action in bipolar disorder have not been established, although interaction with voltage gated sodium channels is likely to be important.",
"",
"Why do we allow drugs to be used for conditions if we don't know how they work for that condition? Clinical trials. If it can be shown a drug is efficacious and the potential side-effects, cautions, contra-indications are know - then that is the information one really needs to know. Paracetamol is a widely used drug, it is given to babies, children, adults and the elderly - yet we still don't completely understand how it works."
] |
[
"Yeah it actually makes sense now! Thank you very much for taking the time to answer"
] |
[
"Upon launch, what kept the Space Shuttle from tilting backwards towards the orbiter?"
] |
[
false
] |
[deleted]
|
[
"If the rocket nozzles generate a thrust that points through the center of mass of the shuttle, then it won't rotate."
] |
[
"I'm a bit confused here and not seeing the boosters you're referring to. ",
"The external tank contained fuel for the orbiter's main engines, while the two tall white boosters mounted to either side of the eternal tank are entirely self contained solid fuel rockets which once lit simply burn through their fuel until they go out. "
] |
[
"This is the ELI5 answer. In more detail, the mass of the external tank and solid rocket boosters is ",
" small. The empty weight of each of the SRB's was around 200,000 lbs, and 1.3 ",
" pounds while fueled. The empty weight of the tank was only 60,000 lbs, but it weighed ",
" million pounds fully fueled. The orbiter itself only weighed 150,000 lbs empty, and had a max takeoff weight of only 240,000 lbs. The Space Shuttle Main Engines had a big gimbal range, and the SRB's were also gimbalable to around 10 degrees. With that level of range of motion, it wasn't too much of an issue to keep the vehicle propped up appropriately. Not to mention that as it flew, it turned over and allowed drag to help out the gravity turn and flew upside down into orbit."
] |
[
"Were astronomical phenomenon easier to see with the naked eye 5000 years ago than there are today?"
] |
[
false
] |
Did ancient Egypt, Mesopotamia, and the Indus Valley civilization see a different sky than we see today? How much easier was it for them to view astronomical bodies with the naked eye than it is today? Edit: Fuck, just looked at my title. *than they are
|
[
"Are you talking about light pollution? Yes, all light on earth obstructs our view of the stars. And it's probably safe to say that there is more anthropogenic light today than there was 5000 years ago just about everywhere. So they probably had a better view of the stars. Here's a ",
"picture",
" showing the difference in the night sky before and during a large blackout. Smog and atmospheric pollutants also contribute to obscuring our view. As far as seeing a different sky goes, although the stars move in the sky, this is very slow and stars' lifetimes are generally orders of magnitude greater than 5000 years so birth and death of stars wouldn't make much of a difference either. "
] |
[
"You don't even have to go back 5k years. A few hundred years ago at most, the sky was much better for astronomy at night.",
"With the introduction of electricity, light pollution became prevalent. That took off about 100 years ago. Dim stars become invisible because of the sky glow.",
"With the industrial revolution, the amount of particulates in the air of large cities increased a lot. That reduced transparency. It happened roughly 200 years ago.",
"If you go camping and you're at least 1 hour drive from any city, you can see how the sky was supposed to look like."
] |
[
"Say you are in a desert 300 miles from any light in all directions. You look at the sky. Then suddenly all light on earth goes out. You look at the sky again. Would the second look be any different?"
] |
[
"What is the fastest theoretical speed a planet (rocky or gas giant) or dwarf planet can rotate without breaking up? Also what is the timescale for one rotation in comparison to an Earth-standard day?"
] |
[
false
] | null |
[
"Depends on what the planet is made of, but in general, about 20-30 times faster than Earth rotates.",
"Let's assume that all layers of the planet rotate uniformly at all depths (which isn't always true). For a planet to begin to break apart, the centrifugal acceleration felt by the top layer of the planet at the equator must cancel the gravitational acceleration holding it in place. Thus,",
"G M / r",
" = ω",
" r ",
"ω = (G M)",
"/r",
".",
"If the planet has roughly uniform density, we can express the density as ρ=4πM/3r",
" so M=3r",
" ρ/4π, so:",
"ω = (G 3r",
" ρ/4π)",
"/r",
"=(G 3ρ/4π)",
".",
"This is a nice result because it only depends on the density of the material. So for a planet with the same average density of Earth, it would need to rotate with a period of ω",
" = 0.039 days, or about 26 times faster than Earth presently does. (Faster being in the angular sense.) ",
"This is a little more complex for gas giants, because they don't have a uniform density profile ",
"like this",
" and there is a significant amount of shear that happens between layers. However, if we only consider the topmost layer of a gas giant and assume it has the same average density as Jupiter, we find that it would have to rotate with a period of 0.080 days, or about 30 times faster than Jupiter currently rotates."
] |
[
"Yes to both. The faster you spin the planet, the less heavy everything on the surface feels. The speed that the grandparent calculated is when everything becomes weightless, i.e., it's the speed you need to be in orbit."
] |
[
"Yes to both. The faster you spin the planet, the less heavy everything on the surface feels. The speed that the grandparent calculated is when everything becomes weightless, i.e., it's the speed you need to be in orbit."
] |
[
"Can kinetic energy be directly converted to light?"
] |
[
false
] |
Most forms of energy can be directly transformed into one another, like charging batteries, burning wood, wind turbines etc. However, I dont know of any example where light gets created directly from kinetic energy, and I had some science teachers say that its impossible. Is this true?
|
[
"Sorry if this is a stupid question, but do the electrons in our bodies emit electromagnetic radiation when we run, since we're accelerating them?"
] |
[
"Sorry if this is a stupid question, but do the electrons in our bodies emit electromagnetic radiation when we run, since we're accelerating them?"
] |
[
"Ok that makes sense. Thank you. "
] |
[
"Besides human activity, how is the carbon in fossil fuels returned to the ecosystem?"
] |
[
false
] |
Based on the biogenic theory of fossil fuels, the carbon locked into petroleum, coal and natural gas comes from millions year old biomass. Human activity releases that carbon in the form of carbon dioxide, which is then returned to the ecosystem. Besides humans burning fossil fuels for energy, how is that carbon returned to the ecosystem? As a followup - is there any model that states all carbon would eventually be locked away in fossil fuels and the earth would end up barren as a result?
|
[
"A large portion of the petroleum in the ground gets released naturally over time; it isn't extracted and used/burned by humans. Still don't know, once it's released to atmosphere/the ocean, how it recycles back into the ecosystem other than micro organisms eating it. ",
"Doesn't quite support my statement in full but does explain about the micro organisms:",
"http://news.nationalgeographic.com/news/2014/03/140325-texas-pollution-oil-spills-animals-science/"
] |
[
"When buried fossil fuels reach the surface, they can oxidize into CO2 in any number of ways, from coal seam fires to microbial action on deepwater oil seeps. But most fossil fuels do not return to the ecosystem in this way. There is also a lot of carbon locked up in carbonate rocks--this can also weather out into the biosphere, but most of it stays rocks.",
"On the whole, the carbon is not returned to the atmosphere, resulting in a general decrease in carbon dioxide over time. This has helped balance out the earth's temperature: the sun has gotten brighter over time, but decreased CO2 has reduced the greenhouse effect holding in heat.",
"It's thought that over long enough timespans enough carbon will become locked up in rocks that plant life will no longer be able to survive."
] |
[
"Thanks for the response! I didn't know that any microorganisms were capable of handling it at all. I thought hydrocarbons were generally extremely toxic.",
"That would be a very slow release and return to the ecosystem, but since the creation of fossil fuels is equally slow, the system would be in balance over very long timespans."
] |
[
"Does reading improve your reaction speed and time?"
] |
[
false
] | null |
[
"Reaction speed to what?"
] |
[
"the length of time taken for a person or system to respond to a given stimulus or event"
] |
[
"This is a little too vague. Learning to read makes you faster at discriminating between different kinds if letters or words and makes you slower in some cases (as in the Stroop effect). It does not affect how quickly you can push a button when you see a light go on."
] |
[
"Pregnancies after 30? Is it a greater risk"
] |
[
false
] |
Hi guys I have heard that getting pregnant after 30 is a greater risk than before.So I am entirely certain that the people who propound this idea have no biology background or understand any physiology, But I am curious if there is any science behind this. My hunch is no.However is there any specific age after which pregnancy gets more risky?
|
[
"This",
" (PDF) shows that the risks of miscarriage and chromosomal defects does indeed increase as women age."
] |
[
"Maternal age",
" is an independent risk factor for low fetal birth weight, in addition to daewangbo's information."
] |
[
"It has long been recognised that ",
"increased maternal age is a risk factor for the foetus to have trisomy 21",
", a genetic condition more commonly known as Down syndrome.",
"Risk of stillbirth increases",
" as maternal age increases, however ",
"risk of placental abruption decreases with increasing age",
".",
"35 is generally considered to be the threshold age at which the period of increased risk of complications is greater, although women aged 30-35 generally have higher risk pregnancies than those aged 20-29."
] |
[
"Turing complete?"
] |
[
false
] | null |
[
"It means that by using the rules of magic the gathering, you can simulate a Turing machine.",
"A Turing machine is a hypothetical machine that manipulates data on a tape according to a set of rules. A Turing machine can be made to run any computer algorithm.",
"So this means that given enough time and space for the cards you could play a game of magic that solves any problem that a computer can."
] |
[
"Would chess then also be considered Turing complete?"
] |
[
"I can't seem to find anything definite about the matter."
] |
[
"Why did the Sahara Desert enter an arid-green cycle?"
] |
[
false
] | null |
[
"Short answer: wobbles in the earth's orbit and rotational axial tilt cause variations in amount of solar radiation reaching the earth. During periods of less solar heating, the inter-tropical convergence zone moves north, allowing the tropical monsoon moisture to move into areas further north on the african continent. ",
"https://www.nature.com/scitable/knowledge/library/green-sahara-african-humid-periods-paced-by-82884405"
] |
[
"Global warming isn't about those random and temporary fluctuations, though. "
] |
[
"Global warming isn't about those random and temporary fluctuations, though. "
] |
[
"Does HIV cancel out any allergies a person may have?"
] |
[
false
] |
From my (admittedly limited) understanding, HIV causes your immune system to fail nearly completely Allergies are an overreaction of your immune systems reacting to something that is not a threat to the body If you were allergic to cats as an example, contracted HIV, and somehow came into contact with a cat, would your body still react to it in similar ways? Edit: has said in a comment down there that they may have heard of leukemia and HIV essentially cancelling each other out in terms of white blood cell count. I too am interested in this so have popped it up here
|
[
"HIV does not really cause the immune system to fail completely. The immune system is extremely complex and has several different arms that are all necessary but not sufficient to protect us. HIV actually affects a relatively specific part of the immune system.",
"Allergy is a relatively nonspecific term. Allergies that cause anaphylaxis (aka type I hypersensitivity), like penicillin, peanut, shellfish allergies, etc. are caused by the rapid activation of pre-formed antibodies in the blood which are products of the \"humoral\" immune system, i.e. B lymphocytes and their derivatives. Although T cells (the CD4+ subset of which is the lineage affected in HIV) are involved in activating B cells and inducing the production of antibodies, once this has happened there is a long-term memory response preserved in the B-cell line, so wiping out the T cells is unlikely to affect an existing anaphylactic allergic response.",
"On the other hand, there is another kind of allergy known as a type IV hypersensitivity reaction that is mediated entirely by T cells. Examples of this reaction include contact dermatitis from nickel or poison ivy and the tuberculin skin test (aka PPD test). This kind of reaction is markedly blunted by HIV. In fact, the threshold for a positive PPD test (measured in millimeters of skin reaction) is lowered in patients with HIV because they are not able to produce as large of a reaction to the PPD and would otherwise end up with a high rate of false negatives."
] |
[
"Just to add to this, mast cells and eosinophils are the main effector cells of allergy, and they are largely unaffected by HIV. So long as one had the allergies already, most of the machinery will continue to work for a while. B cell longevity and memory is an interesting topic though, and I’d be curious to see how long it takes the T cell population changes to affect B cell memory in the context of allergy..."
] |
[
"CD4+ cells (those which HIV targets) control the signal of the immune response so it's probably best to understand AIDS as a disruption to the normal immune function versus simply suppressing it.",
"An example is a fairly common symptom of AIDS, ",
"allergic rhinitis",
". But studies have found a variety of autoimmune conditions that can flare up: ",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4105162/",
".",
"To answer your example, a cat allergy could indeed become worse with AIDS though a cursory look at the literature doesn't see any specific studies. It should be noted though that someone with HIV probably shouldn't be around cats since toxoplasmosis is basically a death sentence in severely immunosuppressed. ",
"https://www.uptodate.com/contents/toxoplasmosis-in-hiv-infected-patients",
"",
"EDIT: feel free to check ",
"r/ID_News",
" for infectious disease news"
] |
[
"Is there enough oxygen in the ocean for us to live in the ocean and breathe through a machine that extracts the dissolved oxygen?"
] |
[
false
] | null |
[
"No, no, no. Or at least: that is not what your links are saying.",
"To begin with, 34.3% is \"percentage of gases in sea water is based on the total gases dissolved in sea water at equilibrium with air\". The fact that 34.3% of the gasses dissolved in seawater is air is NOT THE SAME as saying that there is more oxygen in seawater as there is in air. Seawater is mostly seawater, with a relatively small amount of gas dissolved in. ",
"To make the direct comparison of how much air there is in seawater vs air, we're gonna need to do a little math.",
"This chart",
", listed on that same link you sent, shows us that the dissolved oxygen concentration is something like 220 micro-moles per kilogram of water. Note that for seawater, 1 kg is approximately a liter. So we've got something like 0.000022 moles of O2 per liter of seawater.",
"Now, the air we breathe is 20.8% oxygen. What's that in moles per liter? Just to get a ballpark figure, let's assume our air is approximately an ",
"ideal gas",
", and assume ",
"standard temperature and pressure",
" (e.g. sea level pressure, 25 celcius). That gives us",
"\n(1 / 24.46500 litersOfAirPerMole) * 0.208 molesO2 per moleOfAir = 0.00850194155 moles of O2 per liter of air.",
"That's about 350 times as much oxygen per liter.",
"So no. Air has a lot more oxygen in it than seawater does. Sorry. I'm not saying you can't build a mechanical gill machine that does this, but, well, a human tidal breath ",
"is around half a liter",
", so the machine would need to suck in 175 liters of water for each breath. So backpack-mounted is probably out, given current technology. The bottom line is that warm blooded animals generally need a LOT more oxygen than fish.",
"If you have a big enough power source (like, say, nuclear subs do), you can use electrolysis to break H2O into hydrogen and oxygen, but that's an entirely different thing, and doesn't on dissolved oxygen. That's why nuclear subs can stay down so long.",
"edit: Another way to calculate it would be to convert the amount of oxygen in a liter water to a volume of normal, standard-temperature-and-pressure oxygen. In other words, figure out how much gaseous oxygen you'd have if you got it all out of the water and breathed it in. 0.000022 moles oxygen per liter of water * 24.46500 liters gas per mole oxygen = 0.00053823 liters worth of gaseous oxygen per liter of seawater. Again, versus our air, which is 0.208 liters of oxygen per liter of air. Same result, though. 386 times as much oxygen is in a liter of air as in a liter of seawater.",
"another edit: For purely-rhetorical purposes, all these calculations were based off the 220 umol/kg figure supplied by his link. I personally have no idea if that's actually accurate or not. I have no idea if ",
"http://www.waterencyclopedia.com",
" is a reputable source."
] |
[
"You would then be able to recover at least a little energy, but that defeats the purpose if it just binds with oxygen, which is what you wanted to create. "
] |
[
"The important thing isn't so much the concentration, it's the throughput of the machine. If the machine can suck up 100 gallons per minute and extract the oxygen at some efficiency rate, it's going to be a lot better than if it can only process 10 GPM"
] |
Subsets and Splits
No community queries yet
The top public SQL queries from the community will appear here once available.