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[
"Would a UV telescope be useful in any way?"
] |
[
false
] |
I get that celestial bodies moving away from us in an expanding universe get red-shifted from the Doppler effect and, thus, are visible on infrared telescopes like Hubble (correct me if I'm wrong). So, would it be possible to track celestial bodies with a UV satellite telescope? The idea of tracking stars coming toward us at relativistic speeds has a funny ring in my mind. Sub question: is it even possible for a celestial body to charge toward us at near-light velocity?
|
[
"Although not strictly forbidden by the laws of physics, there are no celestial bodies \"charging towards\" us at at relativistic speeds. UV telescopes are certainly useful though, as there are objects that emit normally in the UV - high mass stars for example."
] |
[
"Color shifting is due to the movement of galaxies relative to ours. But we are not seeing the galaxys because they are shifted, we see them because they have Black body radiation output that we can analyze. On the black body spectrum we are able to see all portions of EMR (light). Including Uv, IR and visible. So we already use uv to understand more about the star emitting them. The other kind of shifting is blue shifting, when a body is moving towards us, like the andromeda galaxy is. Hope that helps.!"
] |
[
"Yeah man, I'm pretty sure hubble has a UV filter even."
] |
[
"The weather forecaster just said that summer officially starts at 11:54 am. What determines when a season starts and why isn’t it the start of the calendar day?"
] |
[
false
] |
Furthermore who makes that determination?
|
[
"This start of summer is the moment when the sun reaches its northernmost position in relation to the earth.",
"Because years are not 365 days long (but approx 365.2425) it shifts slightly between years.",
"",
"Winter is when sun in the most south.",
"Spring and Autumn start when the sun is exactly above the equator."
] |
[
"The longitude of the sub-solar point at the moment of the equinox? That varies from year to year. 2018 Sept 23, it was in the Pacific Ocean about 400 km NE of Papau New Guinea. 2019 Sept 23, it will be in the Arabian Sea. The point changes by close to 87 degrees from year to year.",
"As for being \"odd\", the solstice is at 15:54 UTC. That has to be almost noon ",
" on the Earth. You just happen to notice it because you are living at that place (time zone). If solstice was at 10:07 UTC, like it was a year ago, the people in South Africa would find it \"odd\".",
"Who makes that determination? Astronautical seasons are determined by the geometry of the Earth and sun. They exist without any person determining them, just like dawn and sunset time exist without any human determination. They have been calculated by humans pretty accurately since 1000 BC at least (the Babylonian Mul.Apin compendium). Modern determinations are calculated by the NASA Jet Propulsion Laboratory, the Russian Institute for Applied Astronomy, and the French IMCCE."
] |
[
"Which point in the equator? I just think it’s odd that it is at peak at almost noon here which is -5GMT."
] |
[
"if matter and energy are one and the same, shouldn't earth have been gaining tons and tons of mass over the years via sunlight?"
] |
[
false
] | null |
[
"The Earth emits alot of radiation as well. In fact, the amount emitted is the same as the amount received from the Sun.",
"Every object emits so called \"thermal radiation\". EM radiation with a frequency and intensity that depend on the temperature of the object. The light from the Sun heats up the Earth, the Earth radiates it back into space. ",
"If at some point the Earth would receive more radiation (as measured in total energy) than it emits, the temperature of the Earth goes up, which increases the total amount of energy emitted through thermal radiation and an equillibrium is reached.",
"If at some point the amount of thermal radiation emitted by the Earth goes down (for example due to increase CO2 levels in the atmosphere that, while transparent to sunlight, absorb and reemit the Earths thermal radiation, partially back down to Earth), the temperature goes up, causing more radiation to be emitted until once again equillibrium is achieved at some new temperature."
] |
[
"Note that Earth actually emits slightly more than it receives, since nuclear fission in the core adds a bit more energy to the equation."
] |
[
"At earth's distance from the sun, total solar irradiance is about 1361W/m",
" If we multiply this by the surface area of the disc of the earth, and multiply it by a year, that gives us 5.47*10",
" Joules per year. Assuming that was absorbed in its entirety and not re-radiated, that would result in a gain of about 61,000 tons per year.",
"For comparison, the earth gains an average of 60 tons per day of cosmic dust, resulting in a weight gain of about 22,000 tons per year.",
"Conversely, the earth is losing about 3kg of Hydrogen and 50g of Helium to space every second, that means that the earth is losing about 95,000 tons per year to space.",
"TL;DR: Even if the entirety of all the solar energy hitting the face of the earth was converted into mass, the earth would still be losing weight."
] |
[
"Why do ionic bonds form crystals rather than small molecules?"
] |
[
false
] | null |
[
"Because they don't have any sort of terminating geometry. If you pair a sodium ion with a chloride ion, each ion still has plenty of space adjacent to it that another ion could fit into. And because ionic bonds don't involve the sharing of electron pairs, individual ions within an ionic compound don't have a strict limit on the number of bonds they can form. Instead, that number is governed by geometry and kinetic energy."
] |
[
"Thought this was a pretty good explanation. From the wiki page on ionic bonding:",
"The electrostatic attraction between the anions and cations leads to the formation of a solid with a crystallographic lattice in which the ions are stacked in an alternating fashion. In such a lattice, it is usually not possible to distinguish discrete molecular units, so that the compounds formed are not molecular in nature."
] |
[
"Not all ionic bonds form crystals. Take proteins for example. The linear structure of a protein is simply a bunch of amino acids linked by covalent peptide bonds. The secondary and tertiary structure of the protein is determined, in part, by non-covalent interactions such as ionic bonds. However, compounds that are ",
" composed of ionic bonds will form crystals."
] |
[
"As scientists, are you ever worried about what you might discover?"
] |
[
false
] | null |
[
"Imagine a case where a scientist analyzing demographic-type data found a irrefutable correlation of a trait (say, intelligence) with race (or gender, or some other sensitive topic). Do you keep it a secret, or do you publish knowing that you'll immediately be compared to Hitler?"
] |
[
"Working in a lab which has been accused of trying to play god and which many a nutter thinks has the potential to kill all life on Earth... no. ",
"Without getting into specifics which would compromise my identity, The protocols are entirely unnecessary for us but for our counterparts working with synthetic biology in bacterial systems, those organisms cannot survive outside of the lab for many a reason. The chance of them suddenly mutating to do so is no greater than a new super bug evolving directly from the common flu with no help from us.",
"You can relax =D "
] |
[
"As a scientist, I have no idea what you're asking.",
"Most scientists aren't, in fact, astrobiologists.",
"Are you asking more generally \"Are scientists worried that their discoveries might end up harming people?\"",
"The answer would depend on the scientist. My field doesn't really have any kind of potential to harm people, but I'm sure no scientist wants to be responsible for the next asbestos or thalidomide tragedy.",
"Spooked by these terrible events in the past, most scientists exhibit due diligence to ensure they don't cause negative outcomes. I'm sure NASA has considered the possibility of finding extraterrestrial life, especially microbial life, and they will have protocols in place. Maybe there's a NASA scientist on ",
"/r/askscience",
" who will be able to tell us what those protocols are.",
"NASA has always taken a very cautious approach to extraterrestrial life. In 2003 the Galileo space probe was originally going to be crashed onto a Jovian moon. On its descent it was to search for gaseous traces of life. NASA was concerned that this could cause contamination of the moon with terrestrial (Earth) microbes. So instead the probe was crashed into Jupiter. The rovers currently on Mars were sterilised prior to launch to prevent microbes from surviving the trip."
] |
[
"Is there a measurable increase in salinity of surounding waterways after a particularly cold winter when salt is used in the roadways?"
] |
[
false
] |
Wondering because I see salt stains everywhere and I grew up around the Chesapeake Bay area.
|
[
"Yes.",
"\n The Chicago area waterways are a good example. Increased chloride levels due to road salt are seen in several waterways in the area. At high levels this can be toxic to aquatic flora and fauna. The levels increase and decrease with the season, but have shown a steady increase once the sixties.",
"\n",
"Article with links to studies."
] |
[
"When Flint, MI had lead in their drinking water, the cause was using water from a river whose water was corrosive. The cause of the corrosion was due, in part, to salt run-off from nearby roads. This, in turn, corroded the water pipes, many of which were lead."
] |
[
"*has lead in their drinking water. Sadly this is still a problem, as the corrosive water removed plaque that had built up inside the lead pipes over the years and prevented lead from leaching into the water. Many parts of the city are still advised not to use to water for drinking, bathing, or washing clothes or dishes. "
] |
[
"How hard would I have to punch to deflect light?"
] |
[
false
] | null |
[
"You don't have to punch at all. Light bounces off of you all the time. That's how other people see you."
] |
[
"I mean, if someone was shining a beam of light from below, how hard would I have to punch to change the direction of the light, if only for an instant?",
"I'll clarify this in my post."
] |
[
"Punch what? The beam of light? Just stick your hand out into the beam and the light will be deflected"
] |
[
"Science AMA Series: Hi, I’m Dr. Kerry Assil, Eye Surgeon For The LA Kings And Founder Of The Assil Eye Institute, AMA!"
] |
[
false
] |
Hi reddit! I’m an , and lecturer who has worked with the LA Lakers, Kings, numerous other Gold-metal athletes and A-list celebrities. I have spent the last 20+ years of my career working with the most advanced and cutting edge technologies to improve vision and eye health. I know what works, what doesn’t, the newest implantable lenses, the biggest myths & fears of so many Americans that may be avoided, if they only had the right information. June is Cataract Awareness Month and it’s always been associated as a grandma’s issue – well, no longer. Cataracts are now affects Americans as young as their late 40s and 50s! *
|
[
"What does it mean to be an eye surgeon for a sports team? What are your responsibilities with them?"
] |
[
"What's your opinion on LASIK/PRK surgery? Are there still reservations about long-term side effects, or should they be considered safe?"
] |
[
"mikovsh, I am very concerned for you as the history does not quite make sense. Since you are now living in the US, if it is not inconvenient for you to travel to Los Angeles, I would be more than happy to examine your eyes because several potential solutions come to mind. "
] |
[
"I want to hang dry my clothes; which would be faster; exposing it to sunlight or a breeze?"
] |
[
false
] |
Would it be faster to dry a garment indoors against a window that's exposed to direct sunlight, or outside, where there's a slight breeze (but in the shade)? Basically, I'm asking is the sunlight more effective at drying stuff, or is open/moving air? Strange question, I know, but I'm very curious.
|
[
"It depends on the humidity of the indoor room. If the indoor room is small and not ventilated, the moisture from the drying clothes will quickly raise the humidity of the room to the point that is significantly slows down the drying of the clothes. If you place a large dehumidifier in the small, ventilated room, or if you give it good ventilation (open some windows) it will keep humidity low and keep the drying time short. "
] |
[
"It also depends on the humidity out doors as well. I had friends in the Costa Rican rain forest that claimed that hanging clothes to dry outdoors simply didn't work. The humidity caused them to stay damp.",
"As a person who lives in a dry, near desert climate, drying indoors is a win/win situation, as the clothes dry quite quickly and I don't have to run my humidifier as hard when I am drying clothes indoors."
] |
[
"Definitely a breeze, hands-down. Without it the air close to the surface of the fabric will quickly saturate. Moving the air will keep the delta humidity between fabric and air high, creating a more efficient exchange. The sun on the other hand will add more energy to the system, increasing efficiency slightly. Consider how much heat energy you need to boil water.. "
] |
[
"Are any human body cells anaerobic?"
] |
[
false
] | null |
[
"Mature red blood cells lack mitochondria or other organelles in order to make more room for hemoglobin, so they're totally dependent on anaerobic fermentation. The lens fibers of the eye are similar, being essentially sacks of clear protein."
] |
[
"Cancer cells can sometimes shift to anaerobic metabolism as they deregulate cell metabolism. It's thought that this happens because intermediates from the relatively messy and inefficient anaerobic reactions can be utilised by the cancer in various biosynthetic pathways in the building of new cells. ",
"This shift towards anaerobic metabolism has been dubbed a 'hallmark of cancer'.",
"Source: ",
"http://www.cell.com/cell/fulltext/S0092-8674(11)00127-9"
] |
[
"It could make sense as long as they carried more oxygen than they use. Kind of like how tankers can transport the same fuel they run on."
] |
[
"If, according to Quantum Mechanics, physical values are quantized (i.e. discrete), in what sense are irrational real numbers \"real\"?"
] |
[
false
] | null |
[
"Quantized just means that the values the physical property can have discrete rather than continuous . For example, for the particle in a 1D box, the energy levels the particle can have can be expressed as (n",
" h-bar",
" pi",
")/(2 m L",
"), where n must be an integer. Notice that there isn't a fixed separation between the levels, as it depends on n",
" not n.",
"Being discrete does not prevent irrational numbers from being important. The function describing the values could easily have irrational numbers involved thanks to the properties of the differential equation governing the system. Discrete doesn't mean the number terminates at a given decimal, it just means that the function has that specific set of values.",
"There's also not proof yet that length is necessarily a quantized quantity. Most of the time, the quantization that matters is a quantization of energy or momentum not of length or time. Pi is defined as the ratio of the circumference of a circle to it's diameter. So, pi can't just be an approximation of that ratio."
] |
[
"If space and other physical quantities are seemingly discrete (i.e. quantized)",
"Quantum mechanics ",
" treat space or most other physical quantities (such as energy, length, time, momentum, etc.) as discrete. Quantum mechanics is completely formulated in a smooth spacetime and for ",
" systems (such as a free particle) the allowed energy states are a continuous distribution.",
"For example, consider a typical photon, whose energy is ",
". ",
" is of course a constant, and so is ",
", but the wavelength ",
" can take any value since spacetime is treated as smooth, and so a photon can have ",
" energy.",
"What is quantized (discrete) in quantum mechanics are the ",
". That is to say, even though a photon can have any energy, light can only interact with a material in discrete interactions. Photons propagate as waves, but ",
" as particles. That is to say, if a system emits a certain amount of energy as light towards some other system, that other system will either absorb it all, or not absorb it all -- it won't absorb half of it, or some fraction of it, leaving the other fraction to continue onward.",
"If space and other physical quantities are seemingly discrete (i.e. quantized) on a physical level, how \"real\" are the majority of real numbers (i.e. the irrationals)?",
"Even if you assume a discrete spacetime (which is done in certain theories of quantum gravity such as Loop Quantum Gravity), it changes nothing about the statements of pure mathematics. It just means that certain parts of the universe can't be modelled using the Real numbers, but must be modelled using either the Integers or the Rational numbers. Real numbers will still occur in any system where some measurable value doesn't have to take on a discrete quantity, and even if no such systems exist in reality, we can still speak meaningfully about imagined systems which were not constrained in such a way.",
"For example, we know space and time do not have a Euclidean geometry, but we can still model systems ",
" a Euclidean geometry and get meaningful answers. They may only be meaningful as approximations to real, actual systems in nature, but the math would still be useful and logically consistent.",
"Is the ratio of a physically extant circle to its diameter pi or just an approximation?",
"Given how a circle is defined, the diameter of a circle is always pi. Whether it is possible to ",
" a \"physically extant circle\" is a separate matter from how such a circle would be defined mathematically.",
"Consider an analogy with the complex numbers, or the quaternions. Whenever we make measurements of physical systems, the measurements we get are always real numbers. However, does that mean complex numbers or quaternions aren't real? Certainly we use them to successfully model processes which occur in nature, even if no direct measurements can yield a complex or quaternionic value. And using these number systems can give us algebraically rich, desirable features. For example, the set of complex numbers has a mathematical property called \"algebraic closure,\" where every polynomial equation that can be constructed using them has at least one root. The real numbers do not have this property. Similarly, the quaternions lack a certain property called commutativity -- where A x B is not the same as B x A. Both the real numbers and the complex numbers are commutative, so can't be used to model non-commutative structures.",
"Even though these numbers don't \"occur in nature\" so-to-speak, there's certainly a logical, mathematical reality to them, and some features of nature can be described using them.",
"Does that help?"
] |
[
"Ah, I see. Yeah ...",
"I was thinking of irrationals as values of infinite precision, and at the same time, thinking of Real Numbers as \"real-world\" values. I guess I was coming to the not-so-shocking conclusion that Real Numbers are not necessarily \"real-world\" values.",
"You can think of irrational numbers as real numbers with an infinite precision, but also be aware that there are also rational numbers with infinite precision as well (for example, 1/9 = .111...).",
"You are partly right though -- \"real-world\" values do not necessarily have to be Real numbers, though they must be in some subset of the Real numbers (such as the integers, or the rational numbers).",
"I think I was just under the impression that, in QM, Quantized = Discrete in the case of all physical values.",
"Gotcha. Yup -- that is a common mistake. Indeed, ",
" physical values in QM have continuous distributions or take on a range of values, at least in the majority of circumstances. However, due to the quantized nature of the fields themselves (resulting in \"field quanta,\" i.e. particles), and certain other laws such as Heisenberg's uncertainty principle, there are many systems which do have a discrete distribution in terms of their allowed values. For example, the spins of electrons in atoms, the quantum numbers of elementary particles, and the photon emission spectrum of hydrogen.",
"Another subtletly to point out is that in many cases, having a discrete distribution doesn't necessarily mean that measured values have to be integers or even rational numbers -- it just means that they can only be ",
" real numbers. For example, we often speak of particles having a spin of \"1\" or \"1/2,\" but the units we measure in matters -- and the measured spins are actually multiples of ",
", the reduced Planck constant, which has a value of 1.054571726(47)×10",
" Joule-seconds. Although ",
" has a non-integer value, the spin states of particles can only change by integer multiples of ",
". So that's what is meant when saying that spin is \"quantized\" (or discrete).",
"Hope that helps!"
] |
[
"Why was 100 chosen as the unit of measurement for something being complete?"
] |
[
false
] | null |
[
"‘Mathematics’"
] |
[
"‘Mathematics’"
] |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"If you disagree with this decision, please send a ",
"message to the moderators."
] |
[
"Neutron star material..."
] |
[
false
] |
I once read that a teaspoon of matter from a neutron star would weigh as much as 8000 elephants. If a teaspoon was able to be acquired, what would happen if it were suddenly on earth? It seems like nothing could hold or move it, and it would fall to the center of the planet due to the fact that nothing could deal with the weight to surface area ratio. Is the internal temperature of the earth hot enough to do anything to it? Any insight would be greatly appreciated.
|
[
"All the energy that kept it compressed would be released and explode"
] |
[
"The degenerate matter of the neutron star would likely instantaneously expand outward of something very reminiscent of an explosion, as the neutrons decay into protons, electrons, and high energy gamma rays. The extremely high density of such matter would ensure that it would try to find equilibrium in relatively low-pressure system (our atmosphere) and release its energy as quickly as possible."
] |
[
"It's a bit heavier than \"",
"\" 8000 elephants. Assuming constant density (which it isn't, but to make the calculations easier...)",
"p ~~ 4x10",
" g.cm",
"A teaspoon has 5cm",
" volume",
" which means that a teaspoon of neutron degenerate matter has mass 2x10",
" g or 2x10",
" kg. That is 2,000,000,000kg!! (2 trillion kilos). ",
"An average elephant (Asian) ",
"has mass 3,600 kg",
". "
] |
[
"If gravity acts on objects because they are following a straight line path through curved space-time, then why do objects that are at rest still fall?"
] |
[
false
] | null |
[
"I think the question you're trying to ask is \"if an object is at rest, then why does it fall, because [you] understand gravity to be the effect of following a straight line path\".",
"One thing to remember is that the object is following a path in spacetime, not just in space. So while an object at rest (in space) could be thought of as having a zero dimensional \"path\", an object at rest (in spacetime) will not vary in position, but ",
" vary in time.",
"Consider the (annoyingly busy) image ",
"here",
". The vertical axis is time and the horizontal axis is position. The two edges of the barn (red) are fixed in space but still trace out paths. (Incidentally, the image actually explains the \"bar longer than barn\" \"paradox\", if you're interested.)"
] |
[
"I do not believe it is a rule, but it is a very good idea. A linked image uses bandwidth from the people who host it, and if a link to a small website gets anywhere near the front page then Redditors can easily use all of the bandwidth, \"hugging\" the page to death (resulting in errors and blank screens) in a sort of accidental DDoS. This happens fairly often with small educational websites that were expecting ten people a day and suddenly get 10,000. The power is in your hands.",
"Imgur also often works better for people on mobile."
] |
[
"Got an imgur mirror for that picture?"
] |
[
"Would it be possible to make teeth completely from human enamel?"
] |
[
false
] |
Could teeth be engineered completely from human enamel, and if so, would they fuse to the bone upon implantation? Or is dentin the only material that can fuse into the jawbone?
|
[
"Bone and enamel are both a type of calcium phosphate called hydroxyapatite with a collagen substructure. The difference between the two is mainly in porosity and mineralization - enamel is 98% mineral, bone is 70-90, depending on location, and bone is generally more porous than enamel. We can synthesize hydroxyapatite easily in the lab, and its already used in dental implants. In fact, there's a really nifty chemical reaction where you combine two calcium phosphates in different aqueous forms and hydroxyapatite precipitates out and acts essentially as a cement."
] |
[
"Part of the problem is that it isn't just hydroxyapatite - its hydroxyapatite crystals that have been formed in very specific ways by the body. We can't really duplicate the structure on that level, although we can come pretty close - this crystal structure determines the majority of the properties of the material, including strength. I believe hydroxyapatite is, in fact, used in tooth filling, but I don't think that man-made versions are strong enough to serve as enamel material where pressures can reach over 100 gigapascals during chewing. ",
"Hydroxyapatite is great as an implant because bone and soft tissue bond pretty well to it, without much inflammation or rejection issues. If you make it right, it can also be reabsorbed by the body as the body's bone grows back in (I don't really know if this applies in a dental setting)."
] |
[
"All hydroxyapatite is crystalline (except for some types that can be produced by sintering or similar process and tend to be more amorphous). The hydroxyapatite in bone and enamel has certain size crystals, while we can make hydroxyapatite with many different sized crystals. We can make hydroxyapatite crystals that have sizes pretty close to those in bone, but for some reason, whether there's a macrostructure above the crystalline structure that we haven't observed yet, or if the collagen fibers add additional strength, or w/e (maybe someone else knows, but I don't) our hydroxyapatite crystals that are bone crystal sized tend not to be quite as strong. ",
"The idea that heat and pressure form crystals is pretty simplified, and probably incorrect for many many types of minerals and ceramics. For example salt, NaCl does not require heat or pressure to form and forms crystals when not in an aqueous environment. ",
"That's pretty much all of my knowledge in this field - here's a good article that could explain more. ",
"http://medind.nic.in/taa/t06/i1/taat06i1p81.pdf",
"Don't be afraid of the technical language, just google or wiki any word you don't know and you should be able to understand it."
] |
[
"Since perpetual motion can't be achieved on earth due to friction, does that mean it can be achieved in space?"
] |
[
false
] |
If we were to shoot an object out into space, wouldn't it maintain the same speed forever, assuming that nothing gets in the way? If so, wouldn't that be considered perpetual motion? I'm just so used to hearing that perpetual motion is impossible since it violates the laws of thermodynamics, but space seems to challenge that. Maybe it's just a matter of location, ex: imposible in a non-vacuum environment?
|
[
"When most people speak about \"perpetual motion\", what they mean is extracting energy from a system continuously, i.e. producing work from it (electrical generators, motors, stuff like that). There is nothing in thermodynamics which states that so long as something isn't producing energy, it cannot stay in motion forever. In practice, most things do emit some form of energy through motion, but if you fired a bullet in intergalactic space, it could and likely would travel forever, or until the end of the universe (which is possibly forever, depending on how that comes about).",
"So, yes. In fact, the Earth is in near-perpetual motion around the sun. Not quite perpetual, but certainly so on billion-years scales. The sun will burn out first."
] |
[
"Sorry, no. Using \"only a theory\" means you need more of a scientific education. Gravity is \"only a theory\". The heliocentric model is \"only a theory.\" Entropy is just as well established. ",
"You shouldn't post answers that are not only unfounded, they are misleading. This subreddit has the purpose of educating people genuinely looking for answers from the educated science community. "
] |
[
"the universe does not produce an unlimited amount of energy, that would violate thermo dynamics, though the universe may be infinite, it would not produce energy as a net."
] |
[
"Hybridized resonance structures"
] |
[
false
] |
What exactly does the hybridized resonance structure represent in terms of the molecules actual induction forces, hybridized orbitals, and bond lengths?
|
[
"Ok, this is a short question, but you bring up a lot of ideas. ",
"One useful way of drawing for visualizing atoms and molecules is with Lewis structures. ",
"Lewis structures",
" show the nuclei and valence electrons in a molecule. Now, if you draw a Lewis structure for ",
"benzene",
", there are two equivalent ways of drawing the Lewis structure. These two Lewis structures are called resonance structures. These resonance structures are not structures that can be individually resolved and considered, but in fact the electrons delocalize to a hybrid of these possible Lewis structures. So, the hybrid resonance structure provides information about where the electrons are in the various resonance structures, but all in one structure (",
"for example here",
" you can see how the benzene resonance structures are combined to indicate delocalization). In benzene, the observed bond lengths turn out to be important verification of electron delocalization (meaning that the electrons are spread evenly around the benzene, not alternating single bond, double bond, single bond...). The ",
"wikipedia article on resonance",
") has a section about bond lengths that specifically addresses benzene. So you can see that the benzene bond is some mixture of a single and double bond. ",
"Hopefully that is a clear description of how we can understand electron delocalization with resonance structures and the effect it has on bond length. So you brought up two other ideas: induction forces and hybridized orbitals. ",
"Induction forces are a totally separate idea. Induction forces are the forces that arise from other nearby charges. ",
"For example",
" the dipole of an isolated water molecule is 1.85 Debye, but the dipole moment of water in liquid is much higher, 2.95 Debye. This difference is due to induction effects and it is unrelated to resonance. ",
"Hybridization orbitals are also unrelated to resonance structures and hybrid structures. Hybridized orbitals are a way of understanding molecular orbitals and bonding in terms of atomic orbitals. So a carbon atom has valence s, p_x, p_y and p_z orbitals and it can hybridize to sp, sp2 or sp3, which can help us understand the way that carbon behaves in molecules. There are different things being hybridized in hybridized molecular orbitals and in hybridized resonance structures and each answer different questions. "
] |
[
"I thought that induction would be affected due to the electrons being more delocalized through resonance. I also brought up the hybridized orbitals because I wasn't sure how the p- orbitals would be affected, because I wasn't sure where the double bonds would or wouldn't be in the hybridized resonance structure. I'm in Organic Chemistry 2, but our teacher didn't really delve much into resonance structures. "
] |
[
"You're right that the environment of the electrons will effect how susceptible they are to induction (this is also called ",
"polarizability",
"). But resonance and delocalized electrons are something that is an aspect to that molecule, no matter the environment it is in. While induction occurs when there are external fields present. Yes, electrons in a lone pair are different than electrons in a single bond and electrons in a carbon-carbon single bond are different than electrons in a carbon-hydrogen bond and so they will respond to an applied field differently; but Lewis structures are not the easiest way to approach the idea of induction. Does that help? ",
"Also, I suspect your teacher will delve more into resonance structures and delocalized electrons when you talk about aromaticity. In the general sense though resonance structures are often covered in general chemistry. "
] |
[
"Since there are rogue planets roaming the galaxy without a host star, are there also rogue stars roaming around intergalactic space? Rogue solar systems?"
] |
[
false
] | null |
[
"There are and they've been directly observed -- here's a 24-year-old ",
"press release",
" about it.",
"",
"As has already been stated, these stars are likely thrown out of a galaxy due to interactions (galaxy-galaxy harassment, tidal stripping, ...) or mergers. While stars themselves are not collisional (the spaces between them are much, much greater than the scale of their radii), galaxies are, and galaxy-galaxy interactions are very common, particularly in more dense environments like clusters. You could also think of galaxy evolution scenarios where something like a low mass tidal dwarf forms (also facilitated by galaxy interactions) and then dissipates, leaving orphaned stars in intergalactic space."
] |
[
"Yeah, true - though you wonder about the path that would lead to anyone deciding to look. It's also an inversion of the many-stars, few-planets view we're used to. You'd have the same handful of planets, then one or two distinct non-planet things. ",
"If everything outside the solar system in the milky way disappeared for us, say, a pre-optics observe would be able to see the Magellanic Clouds, Andromeda, and the Triangulum Galaxy - and in the northern hemisphere, only the latter two. ",
"Triangulum would be something of a legend; barely visible under good conditions, so only rarely seen and a challenge to confirm. You'd also need some fairly good telescopes to make it out as anything in particular. It might be confused for Uranus, which is typically a little brighter, and which might be identified earlier if there's no background stars. Vesta is in a similar range, incidentally, and Pallas and Ceres are a little dimmer. You'd have a scattered collection of sightings in a basket of \"not a known planet.\"",
"Andromeda would be more distinctly visible, but still tough outside of good conditions. It's dimmer than any of the traditional planets, but easy enough to see that with no competition from other stars, it would probably be pretty well known, and mysterious as a fixed point among the wanderers. ",
"The LMC and SMC are going to knock viewers for a loop when they cross the equator - distinct, large bright patches in the night sky. They'll get serious attention first, and astronomers will discover they're not single objects but made up of...well, the first stars anyone will see."
] |
[
"Given the number of stars, and the level of energy and chaos involved in galactic collisions, I’m sure there are at least a few solitary stars that have been ejected out thousands to millions of light years away from the nearest cosmic filament. It would be a strange existence. Never seeing even a single object of any kind outside of your own solar system until you have advanced to the level of doing the Hubble Deep Field."
] |
[
"How did Galilei exactly determine that Earth revolves around the Sun?"
] |
[
false
] | null |
[
"It wasn't really Gallileo, but the work of several people. ",
"Copernicus",
" was the one who published the idea seriously. (One of) Gallileo's contributions was the invention of the telescope, with which he observed the 4 moons of Jupiter, showing that not ",
" revolved around Earth. "
] |
[
"In addition, the movements of the other planets make almost no sense if you assume that Earth is at the center of the universe. The ",
"retrograde motion",
" of Mars in particular requires some very strange mechanics to justify a geocentric universe. "
] |
[
"Adding to your comment, the distinction is the fact that other planets in our solar system orbit the sun. Astronomers overturned the concept of a geocentric solar system because the other planets do not orbit earth, not because the sun doesn't orbit thhe earth. If we were the only planet, we would not be able to differentiate between geocentric and heliocentric. The flaw of the geocentric model is that it claimed that other planets orbit the earth, which was conslusively disproven centuries ago. If you have two celestial bodies, they orbit their combined center of mass (which is far closer to the sun than it is to us). There is not one object at a fixed oocation, and the other orbiting around it, since our entire galaxy is moving."
] |
[
"Are molecular structures in liquids random, or do they follow some patterns like solids do?"
] |
[
false
] | null |
[
"I am gonna assume you meant arrangements of molecules in liquids, not the structure of the individual molecules themselves.",
"The answer is yes and no. Normal liquids do not have the long range order that characterizes crystalline compounds. However, neither do amorphous solids. On the other hand, ",
"liquid crystals",
" do show this type of order despite being fluids. Short range order can exist in liquids, for example ",
"water clusters",
". "
] |
[
"Molecular structures in fluids are ",
" random. The structures are dictated by the interactions between the molecules and can be represented by a ",
"radial distribution function",
". ",
"From the wiki:",
"In simplest terms it [radial distribution function] is a measure of the probability of finding a particle at a distance of r away from a given reference particle, relative to that for an ideal gas.",
"The radial distribution function for a solid contains much sharper peaks (approaching delta functions) than that for a fluid because the molecules are distributed much more evenly."
] |
[
"This is not entirely true. Liquids have some quantities which define it to be in a liquid like state (Distance between atoms for instance) but in terms of overall order there is none. ",
"One of the tools we use to determine if our simulations are liquid like or crystalline in what is known the Stienhart order parameters. These parameters use the spherical harmonics to determine if the structures are periodic in nature. The parameter can take on values from 0 to 1, but here's the catch. For a perfect crystal (FFC latice, BCC latice, etc.) the value is between 0.3 to 0.6, but for a bulk liquid the parameter is 0 or that the order of the system is non-existent. ",
"While not entirely random in the sense there is still some reason to what happens, it is still contains a lot unpredictability. "
] |
[
"What's the difference between the 'cell-mediated immunity' & the 'antibody immunity'.?"
] |
[
false
] |
Several newspaper outlets report these two figures as measuring markers of herd-immunity whilst giving results of the seroprevelance survey done. What's exactly the difference between the two? Cell Mediated Immunity vs the antibodies?
|
[
"cell-mediated immunity is the “innate” immunity ",
"No? Adaptive immunity can also be cell-mediated (for example T-cells and NK-cells). From Wikipedia:",
"the adaptive immune system includes both humoral immunity components and cell-mediated immunity components ",
"https://en.wikipedia.org/wiki/Adaptive_immune_system"
] |
[
"To be on point cell mediated immunity is where some cells of the body (like killer t cells) directly attack the pathogen to cause its destruction. Where as humoral immunity(also called as antibody mediated immunity) as its name suggests it has something to with the body humors i.e. the body fluids where the antibodies(tiny proteins) produced by memory cells disable the pathogen by surrounding and adhering it and in a way making it easy for macrophages to grip the pathogen for the process of phagocytosis. "
] |
[
"Antibodies bind to a target and allow immune cells to identify and attack pathogens, but there are some immune cells that can recognize pathogens without needing an antibody. In terms of measuring herd immunity, I imagine antibody levels are better as a measurement as you can tell what the antibody is specific against. Measurements for cell mediated immunity might look at immune activity, but I'm not sure how you could correlate that to % of people who are immune."
] |
[
"Is there any material that will heat up very slowly but cool very quickly (or the opposite), or does a slow/fast heating speed mean a slow/fast cooling speed as well?"
] |
[
false
] | null |
[
"Actually I don't think the conservation of energy has any bearing on OP's question, because it only concerns the rate of heat transfer, not the total amount. "
] |
[
"These are called ",
"Eutectic Systems",
"."
] |
[
"These are called ",
"Eutectic Systems",
"."
] |
[
"Can you please explain what is happening here?"
] |
[
false
] |
Why does its swirl like that and how long will it do it? I have no idea what's happening here.
|
[
"It is called ",
"Rheoscopic fluid",
". They have found some sort of microscopic particle that is both rheoscopic and edible and thrown a handful of that in. ",
"Here's another video of rheoscopic fluid in action.",
"Edit: It is probably fine particles of ",
"glycerol stearate",
"."
] |
[
"So just to be clear: nothing is happening chemically. This swirl happens in all liquids, and you can see it happening if you add particles that follow the flow."
] |
[
"This is the important point. There are no magical (let alone chemical) forces creating this seemingly infinite movement. The fluid was set in motion physically by moving it around."
] |
[
"Does luminous paint (like on a watch) lose power as the years go by?"
] |
[
false
] |
I have a 5 year old watch and the luminous hands are not as bright as my brand new watch. Does the paint stop being as powerful over time or is it because there are new stronger types of luminous paint? Also, Sometimes I will shine my LED flashlight at the watch and the luminous parts get a lot brighter. Will this cause the luminous paint to lose power and retain less light over long periods of time? (I understand about how the light excites the atoms and causes it to stay lit.) Thanks
|
[
"Depends on the watch. Old watches like 60 years plus used Radium and glowed without light, these faded as time passed. Newer watches use Europium and that material does not suffer any practical aging. Except...",
"If you have a cheaper watch that lets in moisture or live in a humid climate the moisture in the air reacts with the Europium and causes fading.",
"Edit:",
"http://en.wikipedia.org/wiki/Super-LumiNova"
] |
[
"A quick wiki search showed 2 different phosporescent compounds commonly used. The first is Zinc Sulfide. The other, strontium aluminate, is about 10x better, but was only discovered in 1992. It's possible that the two watches use the different compounds.",
"http://en.wikipedia.org/wiki/Phosphorescence#Materials"
] |
[
"Some luminous paints are based on the radioactive decay of tritium. The decay of this substance produces electrons, which interact with a phosphor to produce visible light. Tritium illumination is especially popular in high end gun sights, but I've seen watches and emergency exit signs which use it as well. Since this for of illumination is based on radioactive decay, it has a limited lifetime, and grows more faint as the tritium source decays away. On the other hand, it is entirely self contained and does not need to be \"charged\" by an external light source. A point of reference: the useful lifetime of a tritium gun sight is around 5-10 years, for most models."
] |
[
"Why is it commonly believed that time didn't exist before the Big Bang?"
] |
[
false
] | null |
[
"The Big Bang is the creation of the universe. Since time (like physical space) is part of our universe, it also came into existence at the Big Bang.",
"The usual analogy used to try to understand this is the North Pole. Anywhere on the Earth you can walk north, except the North Pole. Once you are at the North Pole, you can't keep going north. Not because you don't understandd the concept of north/south, but because the concept of north-ness is 'created' at the North Pole. In the same way, time is created at the Big Bang. You can't go back in time at the Big Bang because \"back in time\" doesn't exist at the Big Bang.",
"That is, asking \"What is before the Big Bang\" is as meaningless as asking \"What is north of the North Pole\"."
] |
[
"Not just the uniform background radiation.",
"Wikipedia has a section on it",
", which I'll summarise below, but basically it's",
"When Hubble noted that the universe was expanding, there were other theories besides the Big Bang devised to explain this fact. Those theories also made predicitions about what the universe should look like now, but when astronomers checked, the universe doesn't look like that. So, those theories were abandoned, and you don't hear about them now. ",
"Evidence for the big bang:",
"large scale structure"
] |
[
"It is, you just haven't understood it.",
"What ",
"/u/SurprisedPotato",
" said was that the Big Bang theory ",
" the beginning/creation of time at that point. It's an integral part of the theory.",
"Other theories that didn't, i.e. that you can go back in time to before the Big Bang, have been proved to be false."
] |
[
"What technological challenges are preventing scientists from taking a human brain (and no other organs) and keeping it \"alive\"?"
] |
[
false
] |
[deleted]
|
[
"In terms of the technological challenges, here are the ones I came up with:",
"Vascular Integrity.\nYou have the arteries and veins ending at the neck, not to mention thousands of tiny capillary ends. These have to be attached to some kind of circuit that will pump blood. Where does the blood come from; how is it oxygenated, and how is carbon dioxide removed? How will you attach a circuit to the severed neck?",
"Cerebrospinal fluid\nThis is produced in the brain, circulates down the cord and is reabsorbed. This will also need to be drained and recycled.",
"Toxin removal\nWaste products from the cells will need to be removed, requiring some kind of dialysis/filtration procedure.",
"Nutrition\nEqually, you would need some way of providing nutrition; a TPN solution added to the circulating fluid might do.",
"The things above might be the bare minimum, but other things that come to mind would be protection from infection, the problem of keeping the blood from coagulating in the circuit, and basic homeostasis – keeping electrolyte levels normal, temperature and glucose maintenance, and hormone levels –cortisol, aldosterone, insulin, thyroid hormones would all need to be supplemented.",
"In effect you would need to recreate the complex homeostatic mechanisms that we currently need liver, kidneys, pancreas, adrenals, lungs, heart and all the rest to do."
] |
[
"You realize that Russian scientists kept dog heads alive for days in 1920's (or 30's, don't remember exactly) experiments? I'm pretty sure they could have done the same with human heads and with some more research they could have rather easily done so while removing the \"useless\" parts of the head (skin, muscles, bones, etc.)",
"There are videos of the experiment on the interwebs, although I'm too lazy to find them back (it's midly NSFL too, you can't unsee a decapitated dog trying to bark). "
] |
[
"You'd think so but I think a lot of people would want to save that floating brain's soul. "
] |
[
"Special relativity question that I can't resolve (diagram included)"
] |
[
false
] |
There are two photon detectors and a light source directly in between them that emits a single pulse of light. Referring to the picture, in frame O, the two light detectors are stationary. You can see that the pulse of light emanates in all directions, with its intensity scaling down as 1/r . So the photon detectors should both detect some number of photons n1 hitting them that is directly related to the radius of the circle of the pulse at the time it hits the detectors. In frame O' (the pic on the right), the same situation is looked at by an observer that moves to the left of frame O at a constant velocity. Thus in frame O', the two detectors move to the right. The black dot indicates the center point between the two detectors, and the a gray dot indicates where the light pulse emanated from (w.r.t. frame O'). As I showed in the diagram, the circle that the light pulse traces out has to have a smaller radius at the time it hits the left detector than it does as viewed in frame O. And thus, according to my simple understanding, the number of photons n2 that hit the left detector should be greater than n1. Obviously, the photon detector can only have one reading. There's some invariant number of photons that come in contact with it. Can someone help me see where I went wrong? How is this apparent contradiction resolved? Thanks guys.
|
[
"If you take a source which is isotropically emitting in its rest frame and then boost that source, the emission will no longer be isotropic in the boosted frame. This is known as ",
"relativistic beaming",
"."
] |
[
"I think I should've only included one photon detector (the one on the left), because I'm really only ever referencing that one. I just put the other one in there to be able to clearly show a center point between the two as a kind of reference point. This probably made what I was getting at a little confusing.",
"Thanks for your answer, but I know about the relativity of simultaneity and all that, I simply curious about how it looks like a certain number of photons hit the left detector in frame O, and a greater number hits the same detector in frame O'."
] |
[
"Thanks, I've been trying to read through that article and reformulate some questions. So does this mean that if a star were moving toward us at relativistic speeds, it would appear dimmer to us on top the normal blue-shifting effect? By dimmer, I mean it would appear dimmer than it would at the same distance if it weren't moving. Do I have this right?"
] |
[
"Saturated fats. I'd like to understand them better"
] |
[
false
] |
I have an interest in nutrition but my understanding is fairly basic. When it comes to fats, my understanding is not much more sophisticated than: Saturated fat = bad, poly-unsaturated / mono-unsaturated fats less bad. I so however understand that fat is essential in our diets. The thing that bothering me at the moment is coconut. I love the flavour of coconut but have avoided it for some time, as per 100g, 33g is fat, of which 30g is saturated fat. Source: However, I sometimes read things saying that, this is not actually a problem and that coconuts and coconut oil are actually very healthy. For example, the last section (coconut oil) on this page: So, is it the case that foods high in saturated fat are actually not detrimental to your health in the way that we've been led to believe? Do different types of saturated fat have very different nutritional properties? Any thoughts please?
|
[
"Semi-layman here. I remember hearing this stuff from my college professor.",
"So, a fat is a triglyceride, basically a glycerol attached to 3 hydrocarbon chains. The difference between saturated fat and unsaturated fat is in the hydrocarbon chain. The unsaturated fat has a double bond in one of the C-C bonds, essentially giving it a \"kink\" in the system.",
"This kink essentially screws with the ability for the fat to settle, as it cant layer itself perfectly (one of its chains is sticking out in an angle). This makes it more difficult for the fat to solidify, making it a liquid.",
"So what does this exactly mean? Bacon fat is saturated fat. If you cook bacon, you'll notice that all the oil and grease will solidify at room temperature. Vegetable oil is unsaturated fat. It stays liquid at room temperature.",
"As a result, saturated fat (bacon fat) is processed differently in the body compared to unsaturated fat (vegetable oil). My understanding is that unsaturated fat is easier for the body to process (the body can begin metabolizing the fat at the C-C double bond), while the saturated fat is more energy dense and more difficult to process. As a result, unsaturated fats tend to be used up in regular metabolism, while saturated fats get stored in adipose tissue (fatty tissue). ",
"Anyone who understands this better or knows that I'm wrong, please let me know. I'm recalling this from a college chemistry course I took almost 4 years ago."
] |
[
"This may help",
"http://en.wikipedia.org/wiki/Fatty_acid#Digestion_and_intake",
"I'm not well enough versed to answer your question directly without speculation, sorry :("
] |
[
"I'm also a layman in these areas so don't quote me on this but here are my thoughts.",
"As far as I know there's a mindboggling number of combinations that fatty acids can arrange themselfs into to make fats. And all of these fats have different properties and effects on your body. So to just sort them into these four or five categories is not enough to judge what is healthy and what is not. A good rule of thumb that I have been using is that naturally occuring fats are safe to eat and human made fats are best avoided.",
"The problem is that food companies have a tendency to sneak these human made, re-estrified fats into pretty much everything, but that is another discussion. I hope I managed to help you and not just confuse things further. :)"
] |
[
"How much safer are electronic cigarettes than real ones? In what ways if any does it increase the risk of cancer or other diseases?"
] |
[
false
] | null |
[
"One thing to note too is how much safer they are for everyone else around you. Especially in closed spaces."
] |
[
"One thing to note too is how much safer they are for everyone else around you. Especially in closed spaces."
] |
[
"E-cigs are more healthy than smoking cigarettes merely by the elimination of many carcinogenic chemicals found in cigarettes. ",
"Among the 250 known harmful chemicals in tobacco smoke, at least 69 can cause cancer. These cancer-causing chemicals include the following:",
" (National Cancer Institute - US government) -- Arsenic, Benzene, Beryllium (a toxic metal), 1,3–Butadiene (a hazardous gas), Cadmium (a toxic metal), Chromium (a metallic element), Ethylene oxide, Nickel (a metallic element), Polonium-210 (a radioactive chemical element), Vinyl chloride",
"Most people who smoke cigarettes have nicotine addition to some degree. Don't forgot that you can practice harm reduction instead of cession. Everyone finds themselves addicted to a substance, action, or object at some point in their life. Harm reduction can be a viable alternative to quitting by minimizing the damage caused. E-cigs is a valid harm reduction technique for smoking when you don't want or can't quit."
] |
[
"Is time infinitely divisible, or is it composed of a finite number of instants?"
] |
[
false
] |
Can any physical processes occur during time intervals less than 1 Planck time?
|
[
"Not known. However, it's not unlikely combining relativity and quantum mechanics would involve quantized space-time. "
] |
[
"Do you know of the ",
"Planck Length",
"? Basically, it is the shortest possible length one can use in the ",
"Heisenberg Uncertainty Principle",
" and have it still make sense. If you take this length, and divide it by the speed of light, you get a unit known as the ",
"Planck Time",
". Since we know reasonably well that quantum mechanics is the dominating paradigm of physics at the super small, we can infer that while time itself may or may not have a \"granularity\" that is finer than the planck time, a granularity finer than that would hold no physical significance. Of course, the scales we are talking about are very, VERY small. The ratio of the diameter of a hydrogen atom to the planck length is roughly equal to the ratio of a sphere one billion lightyears in diameter to that same hydrogen atom. Similarly, the ratio of a nanosecond to the planck time is equivalent to roughly a billion, billion times the current age of the universe to a nanosecond. It is highly unlikely that humans will ever be able to probe lengths and intervals of time this tiny. A single photon with a wavelength near the planck length would carry about the same energy as half a lightning bolt. "
] |
[
"There is no physical significance proven to the idea of Planck Lengths and Planck times. It's just that they are natural units, because they can be formed by a combination of fundamental, universal physical constants. The_Serious_Accountant has the best answer, because we simply don't know if time is quantized yet."
] |
[
"How is bleeding controlled in surgery? Especially heart transplants?"
] |
[
false
] | null |
[
"Bleeding in surgery is managed by a variety of means: ",
"Cautery",
"Floseal",
"With respect to heart surgery, often large clamps can be applied to both the aorta and vena cava (",
"like this",
") in order to isolate the heart from circulation. Then cannulas can be inserted through which blood can be drawn out, circulated through a bypass machine, and then placed back into the body."
] |
[
"The bloodiest surgeries I have ever encountered are liver transplants by far. These operations can have ",
" amounts of blood loss.",
"The reason why liver transplants can be so bloody are:",
"First, almost all of the proteins involved in clotting are manufactured by the liver. Therefore, someone with liver failure in need of a transplant will likely be deficient in these clotting proteins and have a tendency to bleed.",
"Second, patients in liver failure also tend to have a low amount of platelets. Platelets are involved in clotting, so this further worsens these patients' propensity to bleed.",
"Third, the liver receives a lot of venous blood returning from the gastrointestinal system via the portal vein. Patients with liver failure have cirrhosis, which is basically scarring of the liver tissue. This scarring process also alters the architecture of the blood vessels and capillaries of the liver, meaning that blood can no longer easily flow through the liver any more. This increases the pressure of the venous blood system (a condition called ",
"), and blood vessels under higher pressure will bleed more.",
"Lastly, the liver is a very vascular organ and receives a large amount of blood flow by two major blood vessels, the hepatic artery and the portal vein. Furthermore, the inferior vena cava, which is the major vein that collects all the blood from the lower half of the body and returns it to the heart, runs through the liver itself.",
"All of these vessels need to be exposed, controlled, and cut to take out the liver. Careful exposure of these important structures means meticulous dissecting away of tissue, in a patient who will bleed copiously.",
"I have seen many liver transplant patients be transfused in the range of 50 to 100 units of blood. Each unit of blood is about 250 cc, so we are talking 12,500 to 25,000 cc or ",
". If an average person has 5 L of blood, this can be about 5 times their entire blood volume.",
"In these cases, we sometimes transfuse blood at rates of 1 L per minute or more because that's how fast it's being lost and we need to keep up or the patient will bleed to death. Imagine taking a 2 L bottle of soda and pouring it out on the ground. That's almost the speed at which blood can be lost during liver transplantation.",
"I have personally been involved in several liver transplants that have required close to ",
".",
"In contrast, a heart operation usually requires about ",
".",
"Other surgeries that can be very bloody are trauma surgeries where major blood vessels are injured. The ones that immediately come to mind are pelvic fractures and gun shot and stabbing wounds. I've found these to sometimes reach the 20-50 units of blood range.",
"Edit: spelling"
] |
[
"Cutting the skin actually doesn't bleed much. But there is cautery use a lot in the beginning. Also suction is used along with sterile gauze and lap pads etc. "
] |
[
"If I had 2 objects of mass, say, 5kg and placed them both in a frictionless environment, say, 10m apart, due to Newtons Law of Universal Gravitation, would these 2 objects move together and eventually touch after a long period of time?"
] |
[
false
] |
The Universal Law of Gravitation states that: F = G(m1m2) / r So if 2 objects were placed in a frictionless environment theoretically they should move. I was wondering if they would actually move if done in real life, and how long it would take them to touch. i enjoy learning about gravity and think reddit can help solve some of my wierd questions about it.
|
[
"That's more or less what the Cavendish experiment is."
] |
[
"The bodies will follow some sort of ",
"Kepler orbit",
" around their center of mass, assuming they never collide with each other. It depends on the starting conditions what path they take. In the limit that you have no angular momentum (i.e. the masses fall straight towards each other), you get the ",
"radial trajectories",
"."
] |
[
"Is there any way to get a force with respect to time form of that law?"
] |
[
"Why do Turtles live so long?"
] |
[
false
] |
I read somewhere that it was because they had a slower metabolism. Usually things that metabolize slower live longer (I believe.) I was wondering if that was true and whether there was something else that was responsible for this, possibly molecular (not something like they have a shell that protects them, though that probably factors in too)
|
[
"Soooo.... Why do turtles live so long?"
] |
[
"It's because they secretly travel through space for millions of years with elephants riding on their backs and that gives them the gift of longevity when they transition from the akashic plane to this one. See: ",
"Pratchett et. al",
" ",
"Jay Kay (but how wild would that be?). Yes; Turtles (and a lot of our other scaly friends) have much slower metabolisms. (",
"Crocodile eats a chicken a month, it's fine",
")",
"Turtles(Sea Turtles at least), have the same approximate lifespan as humans. They can feasibly live above 100 in ",
"captivity",
". Edit: I can't remember where I found that number so I can't double check it. Edit Edit: Found it, It's cited as ",
"Moreover, sea turtles don't exhibit senescence the way mammals do. It's basically as if you could look 21 forever.",
" At the ends of our chromosomes we have these fancy dealies called ",
"Telomeres",
". Basically they are these noncoding region on either end of a DNA strand. (It's as if a book started and ended with TTAGGGTTAGGGTTAGGGTTAGGGTTAGGGTTAGGGTTAGGG...) \nWhy are these important? That comes down to a problem in the way our DNA replicates itself. DNA basically has to clip off a tiny bit every time. This is where telomeres come in. Instead of cutting off something useful, like say... part of the ",
"Hoxa1 gene",
" it just snips off a little bit of gibberish. Now, every time a cell splits, it looses a little bit of that until it eventually reaches a point called the \"Critical Length\" Where the cell is like... \"Woahh... Quit that, I'm pretty sure you really want that gene that makes you have eyes\" and stops replicating. The cell starts to senesce. ",
" There's been a couple super cool studies where they look at telomere length in old turtles and young turtles. They were not able to find a significant difference in telomere length of old turtles and of young turtles. They also found that turtles have HUUUUUUUGE telomeres (20kb) compared to mammals(1-6kb)\nWhat does all this mean? It means that either:",
"a) They have exceptionally long telomeres from birth and then all cellular replication ",
" at sexual maturity.",
"b) They have an active expression of the ",
"Telomerase",
" enzyme. This is an enzyme, that for all intents and purposes, puts more TTAGGG at the ends of DNA strands.",
" They have crazy telomere up in here.",
"1) ",
"http://max2.ese.u-psud.fr/epc/conservation/Publi/abstractr/AE_CHA99a.pdf",
"2)",
"http://www.ncbi.nlm.nih.gov/pubmed/19168993",
"3) ",
"http://www.jstor.org/stable/3981"
] |
[
"Telomeres are one factor that contributes to aging, but not even close to the only one. Activation of telomerase is a common method by which cancer cells remain immortalized. Thus, harnessing telomerase would come at a cost of increased cancer, which we don't really know how to deal with yet."
] |
[
"Why has autism been on the rise for the past few decades?"
] |
[
false
] |
My best friend for 18 years now has an older brother who lives with autism. His case is quite mild as he just experiences social problems and a quiet voice. He is quite skilled when it comes to memorization, because he can recite hundreds of poems with ease and never spells anything incorrectly. Anyway, last week I learned that my nephew had just been diagnosed with autism as well. He doesn't talk and seems to enjoy lining things up in order of height or size. When talking to others about autism, they usually seem saddened by individuals who have autism because they are forever socially impaired. But at the same time, everyone I know has heard of autism and knows of someone who has it. I've even heard recently that autism levels have spiked to 1/66 children born today! So I've come to askscience why autism is on the rise. I don't expect an absolute answer since it seems most of the information available is just speculation and theory, but I would like a good response with information backing it up. After researching the topic I've seen the rising levels blamed on everything from genetics to pollution, so I only have a very general idea of what is causing the rise.
|
[
"See, this is the kind of thing science teaches you not to leap to conclusions about. Is it really ",
" that's on the rise? What exactly does that statistic measure? It's the prevalence of the ",
" of autism, which is not the same thing. ",
"As it were, the CDC ",
"just recently",
" pointed to expansion of the diagnostic criteria, better screening and increased awareness as the most likely cause here, rather than an increased amount of the disorder itself. Although it's still possible that other factors could be involved. ",
"And that's really the state of things, as far as I know. High-flying speculation on what the cause of this \"increase in autism\" is really quite pointless until it's been fully established that a real increase actually exists. Nobody had heard of autism a century ago. -Doesn't mean it didn't exist. "
] |
[
"Also from that article in ",
"Nature",
"Not everyone agrees with Insel's assessment. Some argue that the current data aren't strong enough to say for certain that the increase in autism diagnoses represents a true change in its prevalence. \"It feels like the numbers are going up. It really does,\" says Richard Grinker, an anthropologist at George Washington University in Washington DC. But \"when I look at the science, that doesn't stand up\", he says. \"You simply can't take prevalence estimates of autism as if they are the kind of hard scientific evidence that you would get from mapping out the increase in a virus.\"",
"Lest we be accused of only looking at one dataset. "
] |
[
"You know it is also troubling that murder rates increase at the same time of the year that ice cream trucks are out and about. Maybe ice cream trucks drive people mad and then those people go out and kill people. ",
"Be careful about describing correlations. They are fine to generate a hypothesis but should never be left to stand on their own without being tested. "
] |
[
"Is antibiotic resistance only a problem in populations?"
] |
[
false
] |
I know that antibiotic resistance can be problematic when the drugs are used in large populations like livestock over time, but do they have practical risks for individuals? Could someone on low-dose antibiotics over a long period of time develop their own "superbugs" that would put them at risk, or end up selecting for stronger bacteria that would be resistant to other antibiotics as well? For that matter if I had a reservoir of antibiotic-resistant e. coli in my system, then drank some polluted water with its own e. coli, what would be the likelihood of the my strain conferring its resistances on the newly-added strain?
|
[
"Yes, this does happen. I can't speak specifically for bacteria but in my field (fungi) long-term exposure to azole antifungals (for example, in allergic bronchopulmonary aspergillosis) can and often ",
" lead to resistance. It is absolutely not a macro-phenomenon; it works in individuals too."
] |
[
"It's the same in bacteria and viruses, especially chronic infections that take a long time to treat. The perfect example is HIV, you generally hit it with three or more drugs, this keeps resistance from popping up, as an individual virus would have to develop resistance to all three.\nSame for tuberculosis, treatment is months long and requires multiple drugs."
] |
[
"Interesting side note: we suspect that a lot of MDR TB may actually be chronic pulmonary aspergillosis. They appear very similarly in all but serology/PCR."
] |
[
"Does Ice conduct electricity?"
] |
[
false
] | null |
[
"No. Pure water is ",
", it conducts electricity because there are salts soluble in water. ",
"So ice will not conduct electricity, because there is nothing to \"transfer\" electrons between anode and cathode. (even if there are salts they are not in ionic state and they can't move) "
] |
[
"But ",
" will conduct electricity under extreme enough circumstances, so under that logic, OP's question doesn't even make sense."
] |
[
"Ofcourse you're right, that's why conductivity of highly distilled water is magnitude of 10",
" (on the boundry of insulators), not like very good insulators (magnitude of 10",
" and much, much higher) . It's significantly rising when there is electrolyte. ",
"Still, ice have much higher resistance, so there is no doubts like in liquid water. "
] |
[
"How can the sum of an infinite series not be ambiguous?"
] |
[
false
] | null |
[
"All of those series are divergent. "
] |
[
"i still don't see why one way of writing it produces a result that's more valid than the other"
] |
[
"The series are divergent. The normal rules of arithmetic do not apply to them."
] |
[
"Compared to other stars, is there anything that makes our Sun unique in anyway?"
] |
[
false
] | null |
[
"Its location. We are far from other stars and other galactic radiation sources. The Sun is also not part of a binary system- most stars are part of a multiple system.",
"The Sun is also a lot more stable than similar sized stars."
] |
[
"Yup, even our closest neighbour, ",
"Alpha Centauri",
", is a trinary star system. It consists of two stars that are kinda close, forming a binary pair, and a third tiny star that's orbiting the centerpoint of the first two, really far out."
] |
[
"most stars are part of a multiple system",
"Most? I didn’t know that!"
] |
[
"Why does the praying mantis have only one ear? What's the evolutionary advantage, if any?"
] |
[
false
] | null |
[
"evolution is not necessarily advantageous. "
] |
[
"it's likely that there simply wasn't enough advantage to having two ears, rather than a specific advantage to having one."
] |
[
"or to go farther, it developed a single ear early, and that was ",
", and it propagated down the line."
] |
[
"How can Gamma Ray Burst 090423 be 30 billion light years away but the universe is 13.8 billion years old?"
] |
[
false
] | null |
[
"http://www.reddit.com/r/askscience/comments/m1mdc/how_can_the_universe_be_150_billion_lightyears/"
] |
[
"Yeah, it would make more sense if it was wider than it was long... "
] |
[
"http://map.gsfc.nasa.gov/media/060915/060915_CMB_Timeline600.jpg",
" I have this Wmap/expansion on my desktop. It's probably showing the inflation rate proportionally wrong then."
] |
[
"How do you de-ice roads when too cold for salt?"
] |
[
false
] |
In Southern Ontario, the busiest highway in Canada (401) is still a skating rink after about 72 hours without any snowfall. Temperatures have been around -40C for the last day or so, meaning too cold for salt. What other options for getting rid of ice. It just seems odd to me seemingly nothing can be done. Edit: Tired (from driving) when I posted, more like 48 hours without snow, still applies
|
[
"Normal road salt is NaCl, it is effective from 0 to -15. At lower temperatures, CaCl can be used down to about -23. At lower temperatures still, the priority is tire adherence rather than ridding the road of ice, so abrasives (sand) or sand/salt mixtures are used. In more northern communities, say around Kirkland Lake, the roads remain ice and snow covered and winter maintenance consists in maintaining a drivable abrasive layer on the topmost surface."
] |
[
"One of the main arguments in favor of limiting salt use is that the salt will follow the spring runoff and salinate neighboring streams and aquifers. This concern would be particularly relevant in a dry place such as North Dakota."
] |
[
"This just came up in the news today, but apparently the city of Toronto is using ",
"a beet juice salt mixture",
" that is effective down to -32 C. "
] |
[
"If you are in a car going the speed of a bullet and shot a gun backwards out the window what would the bullet do?"
] |
[
false
] | null |
[
"fall while spinning"
] |
[
"Mythbusters did an experiment on this. It would drop strait down if the speeds were matched precisely.",
"http://www.youtube.com/watch?v=BLuI118nhzc"
] |
[
"And the car would speed up a tiny, tiny bit."
] |
[
"How Exactly do Cornavirus Test Kits detect Coronavirus?"
] |
[
false
] |
I've been hearing a lot about Cornavirus testing and I was wondering how the tests work. What mechanisms allow it to detect Coronavirus?
|
[
"DNA would only amplify if the sequence of SARS-CoV-2 is present, since the primers would be specific to the viral genome. Primers are what determine what gets amplified in PCR. ",
"This specific technique is called RT-qPCR."
] |
[
"The method is called real time polymerase chain reaction (or qPCR). It looks for specific gene sequences found only in this virus (SARS-CoV-2) but not in other viruses. We first take the virus's RNA and convert it to DNA using an enzyme called transcriptase. Then by cycling through different temperatures, we heat up the DNA until it separates into single strands, then cool it down to let an enzyme called polymerase duplicate the DNA. We do this quite a few times, so very little DNA quickly becomes a whole lot.",
"We have a probe that glows when it's attached to virus genes, and if we hit a certain amount of light within a certain number of cycles, we say it's a positive target."
] |
[
"We first take the virus’s RNA and convert it to DNA using an enzyme called transcriptase.",
"Wouldn’t you need reverse transcriptase for that?"
] |
[
"If Earth were knocked ten miles off course, how much if any would the temperature change?"
] |
[
false
] |
If say a big enough asteroid collided with the Earth, and knocked us back or forward towards the sun by ten miles, how much would the temperature change on Earth?
|
[
"The radius of Earth's orbit is, on average, ",
"1.5x10",
" m",
". We're looking at a change of 10 miles, or 1.6x10",
" m, a factor of 10",
" change.",
"Power receieved from the sun goes as distance",
" (inverse square), so we're looking at an increase of\n(1 - 10",
" )",
"\n~= 1/(1 - 2x10",
" )",
"\n~= 1 + 2x10",
"\nin energy recieved from the sun.",
"We need to match that to power radiated from the Earth, which goes as temperature to the power of 4. So to increase energy radiated from the Earth by a factor of 2x10",
" , the temperature needs to rise by\n(1 + 2x10",
" )",
"\n~= 1 + 0.5x10",
" ",
"So according to our simple model, global temperatures would increase by about 10",
" , or about one millionth of a degree."
] |
[
"It has to do with our inclination to the sun. For winter in the northern hemisphere, when the earth is closest to the sun, the northern hemisphere is tilted away from the sun. Each ",
"ray of light",
" is spread out over a larger surface area, so there is not as much energy to result in heating."
] |
[
"No. There is a difference of millions of miles in the Earth's orbit. \nPicture from Wikipedia ",
"http://en.wikipedia.org/wiki/File:Seasons1.svg",
"Edited for picture/numbers."
] |
[
"How do scientists achieve extremely low temperatures?"
] |
[
false
] |
From my understanding, refrigeration works by having a special gas inside a pipe that gets compressed, so when it's compressed it heats up, and while it's compressed it's cooled down, so that when it expands again it will become colder than it was originally. Is this correct? How are extremely low temperatures achieved then? By simply using a larger amount of gas, better conductors and insulators?
|
[
"If you want to go to really, ",
" low temperatures, you usually have to do it in multiple stages. To take an extreme example, the record for the lowest temperature achieved in a lab belongs to a group in Finland who ",
"cooled down a piece of rhodium metal to 100pK",
". To realize how cold that is, that is 100*10",
"K or just 0.0000000001 degrees above the absolute zero!",
"For practical reasons you usually can't go from room temperature to extremely low temperatures in one step. Instead, you use a ladder of techniques to step your way down. In most cases, you will begin at early stages by simply pumping a cold gas (such as nitrogen or helium) to quickly cool the sample down (to 77K or 4K in this case). Next you use a second stage, which may be similar to your refrigerator at home, where you allow the expansion of a gas to such out the heat from a system. Finally the last stage is usually something fancier, including a variety of ",
"magnetic refrigeration techniques",
". ",
"For example, the Finns I mentioned above used something called \"nuclear demagnetization\" to achieve this effect. While that name sounds complicated, in reality the scheme looks ",
"something like this",
". The basic idea is that 1) you put a chunk of metal in a magnetic field, which makes the spins in the metal align, and which heats up the material. 2) You allow the heat to dissipate by transferring it to a coolant. 3) You separate the metal and coolant and the spins reshuffle again, absorbing the thermal energy in the process so you end up with something colder than what you started out with."
] |
[
"77K or 4K",
"This sounds very specific, do those two numbers mean something in this context?"
] |
[
"Celsius and Fahrenheit are relative scales (to the properties of water in Celsius's case for example). 0 doesn't mean no energy, it's just relative.",
"Kelvin is absolute. 0 means 0. It's not scaled based off some substance's properties. Since degrees is only used for relative scales, kelvin is just K."
] |
[
"If someone built a perfect cube made from one-way mirrors, what would we see if we observed it?"
] |
[
false
] |
I don't know too much about the mechanics of one way mirrors, I assume that there would be no light inside, making it seem black. How could we add a light source to to the cube and how would it change what we see?
|
[
"There is no such thing as a perfect one way mirror. How it works is that the \"mirror\" side is brightly lit and the other side is dark. The person on the bright side will see his own reflection. Light still passes through from either direction. ",
"In your scenario, the outside of the cube is the mirrored side. All you would see looking in is your own reflection. "
] |
[
"If you see something other than the contents of your medicine cabinet or black cardboard/wood/steel",
"Be freaked out."
] |
[
"So if I cup my hands around my bathroom mirror and press my face against my hands and can then see inside my medicine cabinet I should be freaked out?"
] |
[
"How do satellites and spacecraft determine their position and orbital parameters?"
] |
[
false
] |
In a spacecraft, what methods are available to determine your position and velocity? GPS? Inertial/gyroscopic accelerometers? Reverse-GPS from terrestrial transmitters? What about before GPS, or when outside earth orbit, on the way to moon or something?
|
[
"There are a few different ways to determine the heading (called \"attitude\") of a spacecraft, and a few other ways to determine the position. Starting from the simplest, working up:",
"Magnetometers: these are literally just compasses. 3 are used in all 3 axes to get the magnetic field's direction, or a single \"3-axis magnetometer\" can be used. These only work in low earth orbit where the magnetic field is strong.",
"Sun sensors: these determine which direction the sun is in. If you have a few of them on different sides, you'll always know where the sun is.",
"Earth sensors (or horizon sensors): these tell you where the earth is, usually using an infrared image of the earth in front of cold space. Also works for any other planetary body. ",
"These first three sensors give you a single heading each. If you have two headings, you can calculate which way you're pointing in inertial space.",
"Star trackers: these are super fancy. They can tell you the direction you're pointing anywhere in the solar system by taking a picture of any constellation and \"remembering\" which direction that constellation is in. You only need that one measurement to get your heading, which is nice.",
"To find your position, you can use any 3 of the above measurements to triangulate your position, as long as you can project where all of those planetary bodies/sun/magnetic field should be at the moment. It's surprisingly pretty easy to do that, so you're set! ",
"In addition, you can also use GPS in low earth orbit, or ground based Radar anywhere in the solar system. This works just like radar on the ground: send a pulse of radio waves in a known direction and measure the time it takes to reflect back to you. ",
"Source: I'm an aerospace engineer who designed this satellite: ",
"http://en.m.wikipedia.org/wiki/Perseus-M",
"Edit: I should also address your velocity question. It's pretty intuitive: just figure out your position twice over a set time, and you divide change in position by change in time to get a velocity approximation. It's a little more complicated when you take into account the fact that your orbit is changing direction as it circles the planet/sun, but thankfully smart people in the 1800s already figured that math out for us (they just meant it to be used for planets and asteroids)"
] |
[
"By using celestial navigation and gyroscopes."
] |
[
"Startracker, sun sensors, accelerometers, gyroscopes mainly.\nYou can also calculate the position from the ground and upload it to the satellite. ",
"Check attitude control (attitude and orbit control systems) for a more exhaustive list (earth sensors...)",
"GPS signals are sent toward the earth so only low orbits satellites should be able to use it with a correct precision. Highest altitude would mean that you cannot have the guarantee to get signal from enough GPS transmitters to ensure a precise positioning (and you don't want that really, especially after the separation with the launcher)"
] |
[
"Is it safe to drink boiling water from a plastic (PET) soda bottle?"
] |
[
false
] |
Is there any danger of chemicals leaching into the water if I put hot tea into a plastic pop bottle (and cool it to make iced tea)? Edit: I know studies found leakage of BPA from heated polycarbonate bottles, but that is a different kind of plastic, and I can't find any results for PET.
|
[
"Its never safe to drink 'boiling' water. You will injure yourself."
] |
[
"I think he meant boiled."
] |
[
"http://suchismitamajumder.wordpress.com/2009/06/15/how-plastic-grading-works/",
"Enjoy."
] |
[
"Can water really be broken down and used as fuel? If so, why aren't we using water as fuel for everything?"
] |
[
false
] | null |
[
"We don't use water as fuel because it isn't a fuel. Hydrogen is a fuel, but you only get it by breaking water, and the energy released is necessarily less than you put in. So in this sense water/hydrogen are being used like a battery.",
"There are several economic reasons for restricted adoption of hydrogen storage, like the explosive risk, need to compress, metal embrittlement, and cost of fuel cells."
] |
[
"Hydrogen is the \"fuel\" portion you could extract from water. Long story short: there are more efficient, less costly ways to access hydrogen that don't require the energy input required to separate the hydrogen from the oxygen in water."
] |
[
"Water can be split into Hydrogen and Oxygen through a simple process called electrolysis. Hydrogen and Oxygen can be used as a pretty nifty fuel. However electrical current must be passed through the water to cause the splitting. Essentially you are expending more electrical energy for the electrolysis than the energy you would get back from burning the Hydrogen and Oxygen."
] |
[
"What did paleolithic humans eat?"
] |
[
false
] | null |
[
"specific answers to this question will depend a lot on what part of the planet you're talking about and also what season of the year, the only good way to summarize it would be \"whatever they could get their hands on that wasn't poisonous, and sometimes even then\""
] |
[
"The answer depends on where the humans were living, and what time of year it was.",
"Humans can eat just about anything and our ancestors had as wide a diet as we do today. Eating anything from game, fish, and local plants. They ate whatever was available, and they likely used food preservation techniques like smoking and drying.",
"Contrary to what proponents of the fad paleolithic diet would have you believe the ancient diet was likely not that much better for you than what we eat today.",
"While caveman didn't have access to the refined sugars, flour, and carbs that we have today they did eat large quantities of fat. All parts of an animal from the meat, bones, and organs would have been eaten and little would have gone to waste.",
"Mummies for example have show alarmingly high rates of arteriosclerosis or hardening of the arteries and it's likely early man had similar issues due to diet.",
"The ability to eat milk products is relatively recent, cavemen were probably all lactose intolerant. ",
"Virtually every single fruit and vegetable you find at the supermarket has been genetically modified by some means, mostly through thousands of years of selective breeding, and you likely wouldn't recognize their wild variety. For example it took researchers decades to determine what plant wild corn was because it was so different than what we would recognize."
] |
[
"as one example though, aboriginal australians haven't really had any need to vary their traditional diet much over the past 60,000 years. consider this paper: ",
"https://projectyoubewell.com/wp-content/uploads/2018/04/An-assessment-of-the-composition-and-nutrient-content-of-an-Australian-Aboriginal-hunter-gatherer-diet.pdf",
"\"The hunter-gatherer diet (which assigns an adequate intake of 2390 kcal perperson/day) is essentially one of cereal and fresh fruit plus dried fruit (combined together), with a moderate amount of meat.\""
] |
[
"What does \"flatten the curve\" mean in a real world situation?"
] |
[
false
] |
As a concept I understand that the goal of flattening the curve is to allow the hospitals to treat all the sick people that are coming in with all kinds of diseases, including covid-19. However, I'm having trouble applying this concept to real world situation. Let's say there 10 million people living in a city with density of 10000/km / ~26000/mile and there are 15000 hospital beds to treat sick people. Using tents/military resources that number of beds can be doubled if necessary. Currently, there are 1000 covid-19 cases and they have been increasing at an average rate of ~30% everyday for the past 7 days. So when social distancing/stay at home measures are implemented what is the target rate of virus spread? I'm not looking for a supper precise number but a ball park? Is it below 20% or more like below 5%? I'm not a scientist or a statistician so if there is a better way to formulate this question, please, let me know what it is.
|
[
"It's easy enough to answer your question; the only thing missing is the average amount of time someone has to spend in the hospital before they recover. For COVID-19 it looks like if you get hospitalized, your condition is usually pretty bad, so let's use 14 days for this example, ",
"which is reasonable.",
" Also, let's talk about ICU patients only because they're the people who are very likely to die if they receive inadequate care. A reasonable estimate is that 1.5% of all infections will require an ICU, which is ",
"about half the rate we've observed in the US; I halved the rate of ICU use among confirmed cases to account for the people who get infected but never get diagnosed because they're either asymptomatic or only mildly ill.",
"Hospitals usually run about 70% full, so you have 9,000 of your 30,000 ICU beds available for COVID-19 patients. Since it takes 14 days for someone to be discharged after entering the ICU, the steady-state rate of infections that won't overwhelm the hospital system is given by ",
"Little's law",
" from queueing theory. ",
"We have 9000 slots / (14 days / ICU bed used * 1.5 ICU beds used / 100 illnesses) = about 43,000 illnesses per day allowable in your city of 10,000,000, or 0.4% of the population getting sick per day. That doesn't sound so bad, right? 43,000 people getting sick per day in just one big city would be way worse than what anyone's saying this will get, right?",
"Well, 30,000 beds is a LOT of ICU beds. Far more than any city in the country has. ",
"New York City actually has about 1,800 ICU beds.",
" Remember how hospitals run 70% full? That means NYC has 540 ICU beds available for COVID-19 patients. Let's plug that back into our expression, and we get 2,600 illnesses allowable per day (0.026% of the city getting sick per day). Guess what? ",
"NYC is seeing about 4,600 new confirmed cases per day",
" and it hasn't yet peaked. Do you see why this is such a major problem? The only reason those extra people [(4600 - 2600) infections * 0.015 ICU admits per infection = 30 people per day] aren't dying ",
" is that we're still filling up those slots - we haven't reached steady-state yet. But NYC ICUs are very close to 100% full right now. At the peak, I wouldn't be surprised if we see many hundreds of people die ",
" in NYC who would have lived if they had gotten medical care. Especially if you include not only the COVID-19 patients but everyone else who needed ICU-level attention (e.g. because of heart attacks, strokes, bad car accidents, or gunshot wounds) but couldn't get it because all the beds were already full."
] |
[
"The target rate of virus spread is 0. There's no \"acceptable\" rate. Practically, that's impossible, so we just try to get as close as we can. At the very least, the imperative is to get the rate of new cases to a level where ICU/hospital discharges are occurring at the same rate as admissions before the ICUs are over capacity. Where that rate exactly is depends entirely on the region's current capacity and effectiveness of delivering any treatment they might have."
] |
[
"The numbers are essentially irrelevant, and I'm not doing the math. But the ultimate point is to ensure that the available resources, including the additional resources being deployed by the government, aren't overtaxed by the number of people needing them. Which means that the number of people recovering needs to be maximized, the speed at which they are recovering needs to be maximized, and the deaths need to be minimized."
] |
[
"We are able to create Diamonds in the lab that have the same hardness and almost the same optical brilliance as the natural kind. What are the chances of us doing this with petroleum Oil?"
] |
[
false
] | null |
[
"Actually, it's just ",
"recently been accomplished in the lab using bacteria.",
" Still, translating that to production would take a while and may be more difficult or expensive than extracting natural petroleum."
] |
[
"Well, we put energy into making diamonds. We could make hydrocarbons like octane easily, but would have to do the same. The problem is using energy to make something we use for energy is pointless. Comparing it to diamonds, that we use for looks and cutting, is not a fair comparison. "
] |
[
"Due to conservation of energy, the only way we are going to be able to make out own hydrocarbons for any gain whatsoever is if we take the energy from somewhere else. ",
"Basically this just goes back to what is the best clean energy source. Nuclear, solar, geothermal, etc. The hydrocarbon would be merely a means of storing and transporting the energy, as electricity has losses and is hard to store on large scales. That said, it wouldn't necessarily be hydrocarbons. We can make fairly decent hydrogen fuel cells, way better than burning gasoline. Also, perhaps kinetic energy storage, better batteries, or super capacitors may prove to be better in the future. Who knows. "
] |
[
"Where does a black hole store its charge?"
] |
[
false
] |
[deleted]
|
[
"It doesn't really have a location for that. Same for the mass. You can observe the electric field outside and calculate the charge of the black hole but you can't point to a specific place and say \"there is the charge\"."
] |
[
"I think this comment answers your question: ",
"https://www.reddit.com/r/askscience/comments/7rg40r/_/dswsuro"
] |
[
"Sorry, but not really.",
"For example, a conductor's charge is around the edges, and a dielectric has a distribution of charge.",
"My question was if a black hole stores it charge on its event horizon or within it ",
"Thanks, though:)"
] |
[
"Bathroom Doorknob and Recently Washed Hands"
] |
[
false
] |
I've always wondered, if you must touch the door knob and cannot use the paper towel trick, are you better served having wet, damp, or bone dry hands in an effort to reduce germ transfer, etc..
|
[
"While drying your own hands reduces the amount of bacteria you transfer personally, I believe the OP is looking for how much bacteria is transferred to you from the doorknob as fire regulations require interior doors to open inward and therefore you would have to grab a handle/knob that potentially others who have not washed their hands have transferred bacteria to."
] |
[
"http://www.medindia.net/news/Dry-Your-Hands-Well-After-Washing-to-Stop-Spread-of-Bacteria-73764-1.htm",
"TL;DR - Drying your hands properly after washing reduces the amount of bacteria you transfer more so than just washing."
] |
[
"Good point. Strange how sometimes in text you don't see these things until someone else points them out, and then it seems stupid I didn't see it in the first place..."
] |
[
"For a polyglot, does the language of thinking affect the thought process?"
] |
[
false
] |
If I'm Russian, and totally fluent in English, does anything change in the way I think if I'm thinking in English? Does my obviously smaller vocabulary (in English vs Russian) impact my thought process? Without taking personal bias into account, which language is better to use internally and why?
|
[
"Which the information in your comment about linguistic variation is true, it doesn't follow that that variation has a large influence on our cognition. No one has been able to demonstrate that it does, despite it being such a compelling question. ",
"Part of the problem is separating language and culture. If you give a person who speaks a language without a large numerical vocabulary a counting task, and they do poorly on it, it has ",
" been demonstrated that their ",
" is responsible. Or, to use another example: A while back some person who wasn't a linguist did a study that tried to correlate tense forms in languages with saving habits, and found a significant result -- ",
" overlooked important confounding factors, like common linguistic (and cultural) ancestry.",
"Effects that we have found that don't have an obvious cultural confound, like the improvements in color discrimination for people who have more color terms, are ",
" effects, and are really only noticeable in laboratory settings. Other effects, like the fact that some languages have a better-developed technical vocabulary than others, are trivial. (Of course you'll find it easier to talk about computation in English than in Tok Pisin, but should people using Tok Pisin suddenly take up computer science in droves, they would invent/borrow the terms needed. The language isn't limited to the vocabulary it has ",
".)",
"The idea that our language influences our thought profoundly has the strong appeal of truthiness to it, but it's a dangerous claim to make. We don't even know what linguistic cognition looks like. We can't even say that \"think in English\" or \"think in Russian\" is well-defined. ",
"EDIT: OP, someone else has linked to a Guy Deutscher article in the NYT. It's a good summary of the issue, I think - but beware that people in the field disagree about how significant these findings are. He's only one viewpoint and a lot of people in the field have a less strong viewpoint."
] |
[
"You'll want to read about the ",
"Sapir-Whorf hypothesis",
" and ",
"linguistic relativity",
"."
] |
[
"There are no substantial, demonstrable effects that language has on thought. The most anyone's ever been able to show is very small millisecond-scale improvements on color discrimination tasks, and other similar things. The typical example is that Russian has two words for blue (one for light blue and one for dark blue), and native Russian speakers can categorize blues slightly faster than English speakers. Aside from minor effects like this, no. There's no evidence that language affects the thought process."
] |
[
"Blood bank pioneer Charles Drew was killed in a car crash in 1950. His injuries were too severe for him to be saved. Per wiki a passenger says a blood transfusion might have killed him sooner. Are there any reasons/conditions why a blood transfusion could kill a trauma victim sooner ? If so, how ?"
] |
[
false
] |
By 1950, the major blood groups and RH would surely have been known for transfusion, (eg in North Carolina where the crash occurred)
|
[
"Blood transfusions increase blood pressure. Since his superior vena cava was blocked, blood flow from the head/neck/chest was blocked. But blood flow to the head/neck/chest continued. This causes a spike in blood pressure localized to these regions. A further increase of blood pressure from the transfusion could result in a cerebral edema, throat swelling, or hemorrhaging"
] |
[
"To make an analogy, the blood vessels in the head were a balloon. One way in no way out. Put more in and balloon pops."
] |
[
"There probably wouldn’t be enough time to save him even if this occurred outside a trauma center. Trauma surgeons would have to open up his chest (thoracotomy) and do some sort of vascular repair but the outcome would likely be negative. I work in an emergency department with a trauma center and on multiple occasions have seen people who have had gun shot wounds through the SVC and IVC I haven’t seen any live. Not saying it’s not possible, I am also not a trauma surgeon so I don’t know exactly what they would do."
] |
[
"Are cryptographic hash functions fundamentally irreversible?"
] |
[
false
] |
If I were to take a slow motion video of the CPU operations and follow all the bit flips, I should be able to find the inverse function for, say, SHA512, or maybe not. Is there something fundamental about the operations that make this impossible? Do they destroy information? If not, does there exist a class of functions that theoretically are irreversible?
|
[
"If you know what exact operations the CPU is doing when performing the hash, you must know what the original number is. I don't quite follow here. They destroy information - a 256-bit hash of a 1 Gb file obviously doesn't contain all the information of the latter. The point isn't to create a unique value for any possible input but to minimize the risk of ",
"collisions",
".",
"Any non-invertible function is \"irreversible\". If I tell you the sum of two numbers is 5, you still can't say what those two numbers are. Or if I tell you sin(x) = 1, you still don't know if x is Pi/2 or that plus any multiple of 2Pi. "
] |
[
"They do destroy information - this is easily proven because hash functions have an output of a standard size, but can accept inputs which are much larger.",
"Two inputs can hash to the same value, so given an output there is of course ambiguity about what the original input was. If the function accepts input of any size, then there are an infinite number of possible inputs which would hash to the same output."
] |
[
"Its important to understand that just because a function is easy to explain or code up that does not mean that it would be an easy function to invert. It seems intuitive that it would be easy to invert if the function is so simple, but our intuition is just wrong here. Like I mentioned earlier, something as seemingly trivial as multiplying two numbers is hard to invert. ",
"The reason why brute force methods are the only available methods to break these hash functions is because that is the goal of the hash function. A lot of very smart people built these functions with the explicit purpose of being difficult to invert. It isn't just a coincidence that they are difficult to invert. "
] |
[
"How long would it take to run out of nuclear fuel if tomorrow the world switched to nuclear power?"
] |
[
false
] |
[deleted]
|
[
"MIT Nuclear engineer here. Short answer? We have no practical reasons, even if we switched entirely to fission power, to worry about running out of uranium. The concerns of \"peak uranium\" are so remote that there is no compelling reason to consider alternative fuel cycles (thorium, recycling, etc), and advocates of these systems are either trying to sell you something you don't need, or do not understand the economics of nuclear power.",
"Longer answer: the exact number depends significantly on the amount that you are willing to pay for the fuel and the expected energy use being the main sensitivities. The Uranium Red Book provides an estimate of the world's proven reserves at particular price points, but these estimates are highly influenced by the resources we spend looking for new reserves-- between the 2005 red book to the 2007 red book there was a huge increase in reserves due to exploration activities. Also, not all countries report their reserves, and the red book does not include anything in their estimate for non-reporting countries. So the red book should be looked at as a lower bound, not a median estimate, of what is available.",
"But let's be conservative for a minute and say that the latest red book is correct, and its estimate of our uranium resources is all that we really have at the given price points. Under $80/kg (roughly the current market price), we have reserves of about 3.7 million kilograms. Under current consumption, that would give us 50 years of reserves.",
"Are we out of uranium once we've used up the stuff that's cheaper than $80/kg? If we want to stay conservative, not quite. We have another 50 years or so in the known reserves above the $80 price point. But if we're willing to take a decent guess, we can infer, from geological sampling, that as you decrease the uranium concentration in the ore you consider reserves, the quantity of ore goes up by a factor of 10-- roughly speaking, this means that if you're willing to double your price point (ore with half as much uranium could be expected to have twice as much cost to mine), your reserves go up by a factor of five (ten times the ore, half the uranium in the ore). This relationship holds roughly true all the way up to seawater (though the Japanese say they have a seawater filtering technology that produces uranium at a price in the area of $360-$500, so as much as you believe them, collection of uranium from seawater becomes economically viable before the really poor ores become viable).",
"So we should, with rather conservative estimation, expect 50 years of uranium at the current price point, 250 additional years at $160/kg, 1250 more years at $320/kg, 6250 years at $640/kg (more if seawater extraction is viable), 31250 years at $1280/kg (this price point is a little under today's cost of reprocessed fuel), and so on.",
"The question this begs is whether or not these price points are cost-prohibitive, the answer to which is likely not. The raw fuel in a nuclear reactor represents about 5% of the total cost of the final electricity (with another 5% in the processing of that ore into useable fuel rods, and the bulk of the cost tied up in the capital of the plant).",
"So, to give an answer that is rather conservative: if the world switched entirely to nuclear power (which would increase its consumption by about a factor of seven), and assumed a 5% growth in electricity usage per year, we could expect, after 80 years with no reprocessing, seawater extraction, or anything funky, to have seen the price of nuclear-produced electricity to have gone up by about 35%. No problem.",
"EDIT: A brief note on breeder reactors to those who don't know what breeder reactors are. U-235 represents 0.7% of natural uranium, and U-238 is about 99.3%. U-235 is fissile, and U-238 isn't, but U-238 can absorb a neutron and become plutonium, which ",
" fissile. In typical reactors, we breed plutonium and use it to help fuel the reactor, but we don't breed more fissile plutonium than we consume in fissile uranium (at the end of a fuel element's lifetime, maybe a third of its power is coming from bred plutonium). A breeder reactor takes advantage of the same process, it just rearranges the core geometry to breed more fissile material than it consumes. It's not a perpetual motion machine of course-- it's breeding fresh U-238 into plutonium, not fission products into plutonium, but it does mean that instead of using the very small fraction of uranium that we do today (not even all of the U-235 that we mine makes its way into a reactor, and of that, not all of it is fissioned), we could use, theoretically, ALL of it. I think it expands our resource base by a factor of about 200, depending on assumptions used. In my book, this means that at around the $1500/kg mark, breeding becomes economically viable, and suddenly we have 200x more material than the figures I've been quoting."
] |
[
"I believe the standard argument for thorium reactors isn't \"We're going to run out of uranium\" but rather \"Why in gods name are we still using these old broke-ass uranium reactors that suck?\""
] |
[
"This would depend greatly on which fuel we used and the kind of reactors. The answer is that potentially, we would never have to worry about running out, ",
"*Edit: from Wikipedia:",
"As opposed to current light water reactors which use uranium-235 (0.7% of all natural uranium), fast breeder reactors use uranium-238 (99.3% of all natural uranium). It has been estimated that there is up to five billion years' worth of uranium-238 for use in these power plants.[70]"
] |
[
"What causes our bodies to develop a tolerance to drugs? What is actually happening?"
] |
[
false
] |
[deleted]
|
[
"There's another mechanism called enzyme induction. Normally drugs are metabolised by the liver or gut bacteria to something that can be more easily eliminated from the body via the urine. This is done by enzymes which catalyse certain reactions. If you can metabolise the drug faster, you can get rid of it from the body faster. To do this, more of the enzyme is made by the body (hence the term 'enzyme induction')."
] |
[
"It depends on the drug in question. In terms of many psychoactive drugs that have a liability for abuse and dependence, there is usually an adaptation at the neural level. This can be the result of changes in receptor expression (becoming less sensitive at the synapse) or other related systems. An example of the latter case is how chronic administration of CNS depressants will lead to compensatory increases in alerting systems, which no longer have anything to \"put on the brakes\" so to speak when the drug is taken away. A small version of this can be seen in how a night of heavy drinking can lead to falling asleep quickly (CNS depressant), but then waking early in the morning and being unable to return to sleep. That's a smaller timescale, but the idea is similar."
] |
[
"One mechanism for this is the body makes more receptors that the drug binds to. Therefore, you need to take more of the same drug to have the drug bind to the extra receptors. This becomes a cycle where your body becomes more and more tolerant to a particular drug."
] |
[
"Another undergrad biologist I know is convinced of this. Is there any merit?"
] |
[
false
] |
[deleted]
|
[
"Use common sense. If there was some truth to the idea that air ions could materially affect human well-being, and if this could be shown under laboratory conditions, someone would make billions of dollars by commercializing it.",
"Based on common sense, in a country that invented and sold millions of ",
", this is very unlikely to be real. It's most likely another New Age myth."
] |
[
"It's BS. So much in that just makes no sense. "
] |
[
"Could the undergrad be confusing this with Ozone? I have read a lot about ozone being bad for living organisms, but nothing on negative ions of oxygen."
] |
[
"Why don't more deep sea creatures wash up on shore once they die?"
] |
[
false
] |
I'm talking super deep sea creatures. Some humans haven't discovered yet. Do they not float to the surface when they die? If they don't, what do scientists believe happens to their dead bodies?
|
[
"Different things. Many sink and decompose, most gets eaten some do make it up and wash up. Most creatures that live at those depths are not positively buoyant, so they will not naturally float up. Currents play a big role in moving things around. Instances of tsunamis upwelling deep sea creatures are not unheard of, but you have to remember, this things live very very deep, so you need something mayor to stir things up enough so that itll come out."
] |
[
"You also need to take into account the incredibly vast difference in surface area between the entire Earth's ocean floor and the combined shoreline surface area of the entire world.",
"The Earth's seafloor surface area is ~224,397,000 miles",
" If we make an (I believe very generous) assumption that the Earth's average shoreline of ~217,490 miles where carcasses could wash up on is 1000 feet wide, then the combined surface area of the entire Earth's estimated shoreline is only ~41,191 miles",
"In other words, using these estimates, the shoreline is only 0.01% the surface area of the ocean floor.",
"(Someone please check my Google-fu and math, please)"
] |
[
"Water isn't much more dense even at the deepest parts of the ocean, because it isn't very compressible.",
"But yes deep sea creatures need to be more dense than water or of equal density, that's what not being buoyant means. If they were less dense than water, they would need to expend a gigantic amount of energy diving downwards literally every second to keep themselves in their underwater living habitat."
] |
[
"Why can submarines barely go deeper than the human free diving record?"
] |
[
false
] |
I stumbled across this interesting picture of marine scales: Why is it so hard for submarines to go deeper?
|
[
"Why submarines are designed for upper ocean work is described well above. That is to say, those operational constraints are sufficient for their missions.",
"Why it is so hard to go deeper has a few key issues:",
"Below 3000m it is very difficult to use \"soft\" or ",
"variable ballast",
", which uses tanks that exchange air and water to control overall buoyancy. The pumps required to expel water a great depths are the problem. This is why research submersibles use ",
"syntactic foam",
".",
"Another issue is maintaining atmospheric pressure inside. Cylindrical designs require much thicker hulls than spherical designs for the same depth rating. There is a point at which physical properties prohibit any practical cylinder due to excessive mass for the hull. Deep submersibles rely on spheres. For example the nearly complete ",
"replacement sphere for Alvin",
" is about 7-feet in diameter with a 3-inch thick Ti hull and five viewports for three occupants. Fun fact: the Cameron vehicle has a ",
"43-inch personnel sphere",
", makes Alvin seem roomy!"
] |
[
"To build a 560-foot vessel to withstand the pressure of say 800 feet is no joke. There is no real need for Ohio class submarines to go any deeper, as they are a ballistic missile platform. Their only mission is to remain undetected and be in a state of readiness at all times, so why bother going beyond that? I speak on this because I currently serve on an Ohio-class submarine."
] |
[
"Due to the fact that they have to be designed for combat military submarines are going to be worse at being submarines. They are designed with a goal of a weapons platform, which conflicts with optimizing for other things. Even down to propeller shape and design the navy has to make sacrifices. "
] |
[
"If magnetism is just a result of relativity applied to the electric field, does that mean the strong and weak force have analogous magnetic effects?"
] |
[
false
] |
I've heard of "gravitomagnetism" which is supposedly the gravitational analog, but I have never heard of strong or weak force magnetism. is the explanation of magnetism based on relativity.
|
[
"In the scope of Classical Electrodynamics, there's a clear equivalence on weather you build up a theory based on the \"E\" and \"B\" fields or a ",
"gauge potential",
". The first description is is not manifestly Lorentz invariant, while the gauge potential is a four-vector under Lorentz transformations. What that means is that the gauge potential encodes the information about how the fields should be transformed under Lorentz boosts - which means that weather you observe an interaction mediated by E or B is not a property of the interaction itself, but your frame of reference.",
"This situation is more obvious when you get to Quantum Electrodynamics, since there's no way to write down a fundamental \"electromagnetic\" interaction between fermions using the electromagnetic fields, you need to write down everything in terms of the gauge potential - that doesn't care about E or B. So in a sense, you can't really say that magnetism is a relativistic effect of the electric field more than you could say otherwise - you just happen to be in the wrong frame of reference.",
"The weak and strong interactions are also very different from the electromagnetic for several reasons:"
] |
[
"There's some good discussion here already, but let me add a bit.",
"The weak interaction -- better, the electroweak interaction -- and the strong interaction are very similar to the electromagnetic interaction when written down as a gauge theory which is Lorentz covariant.",
"If you write down electromagnetism in a gauge covariant form and then do a 3+1 decomposition (this is fancy language for splitting apart the space and time parts explicitly, choosing a preferred frame), you'll see where magnetism comes from, as I'll describe. The Lorentz force comes from the \"curvature\" of the gauge field, which is an exterior derivative of the gauge potential. This exterior derivative has a special structure that makes the B field kind of \"mixed up\" in the spatial part of the curvature tensor. The way that the B field is mixed up is exactly what's needed to form the cross product in the Lorentz force law, v x B. That cross product is what makes magnetism look different from the electric force.",
"Every gauge theory is built in basically the same way, in that the force comes from the curvature, which is the covariant exterior derivative of the gauge field. So if you did a 3+1 decomposition of the weak force and strong force, you'd see classical equations of motion that are similar in that they have cross products appearing.",
"The big differences have been mentioned in other posts. For one, electromagnetism can be seen macroscopically and have classical effects, so you can actually deflect an electron with a macroscopic magnetic field. That's why you can SEE (in a cathode ray tube) magnetism at work in daily life. You can't see the weak or strong forces macroscopically in daily life in this same way because 1) the weak force is short ranged, since the force carriers are massive and 2) the strong force has massless force carriers, BUT it's confining because it's strongly interacting -- so you need incredibly high energies to notice the strong force. These two forces are only seen in quantum mechanical systems, not classical ones."
] |
[
"I wonder if, in HQET, we get a chromomagnetic analog because the gluon self-interactions are ignored as too light compared to the quarks?"
] |
[
"Did surgeons try general anesthesia in real patients or volunteers before it was considered a safe procedure? What was the process of turning it into a general practice?"
] |
[
false
] | null |
[
"Here’s a link to the royal college of aneasthetists page on history of anaesthesia",
"https://rcoa.ac.uk/about-college/heritage/history-anaesthesia",
"It would have been a bit of both but a lot would have been going straight to patients from animal experiments"
] |
[
"\"What's this weird fungus growing on my batch of chemicals here? Better eat it.\"",
"Dr. Hofmann, Inventor of LSD. Probably"
] |
[
"\"What's this weird fungus growing on my batch of chemicals here? Better eat it.\"",
"Dr. Hofmann, Inventor of LSD. Probably"
] |
[
"At what moment does a tree \"decides\" to grow a new branch ?"
] |
[
false
] |
When animals and humans grow, they follow a certain path, which is planned by their genome. But trees seems to be completely random. What mechanism "decide" to grow a new branch?
|
[
"I cannot say for all species of plant, but many plants are not random and in fact have very deterministic patterns of branch growth. The reason it looks so random is likely due to environmental factors such as branches breaking off and branches growing at different rates due factors such as differences in sunlight.",
"New branches are usually determined very early on when they are a bunch of cells close to the very tip of the stem. Whether a bunch of cells become a new branch depends on their position relative to other cells and relative to where the around the stem the last branch came off. In some plants, it is the cells that are 180 degrees from the where last branch came off become the next branch. In others the new branch is at an angle based on fibonacci ratios. In others, it is noisy or random."
] |
[
"First, it's important to know that a branch is not a single entity that grows into any shape. It's a collection of little segments which grew at different times, at different angles, from different points of origin on the segments which had grown the year before. Each segment grows only briefly and will not grow longer again or change shape after that, but has several points on it from which new growth can begin next year."
] |
[
"Plants, including trees, grow at their tips where embryonic stem cells (apical meristem) are concentrated. Daylength, temperature, light, moisture, nutrients all affect growth rate. Growth habit appears to be a tissue property, controlling pattern of branching. Axillary meristems at branch points can sprout too, if the apical meristem is lost or damaged."
] |
[
"How do we know that elements in radioactive decay have actually existed for as long as the numbers purport?"
] |
[
false
] |
I have a rudimentary understanding of radiometric isotope dating, in that measurements can be taken of "parent" and "daughter" isotopes in minerals and the resulting ratio when calculated with the rate of decay gives us an age of that mineral. But my question is, is there any evidence to support the idea that these minerals have actually existed for this amount of time, or is it possible that these minerals came into existence already with a certain amount of x isotope and y isotope? For lack of a better phrasing, how do we know that a ten million year old mineral didn't "pop" into existence one million years ago, or otherwise form from some other method, with an already fixed amount of x isotope and y isotope giving the appearance that it has been decaying for 9 million years?
|
[
"We don't, broadly speaking (in fact, that nothing has been added to or left the material after it formed is a condition for accurate radiometric dating, although you can make adjustments to correct for changes if you know it isn't true). However, you can arrange things such that it is highly unlikely that something like that would happen. For example, zircon can form with uranium atoms as part of it's crystal structure, but rejects lead. That means it is unlikely to form with any lead in it at all: the lead that ends up in it can be assumed to be from the uranium decay, and not to have been there at formation.",
"Also, you can cross-check several samples from related formations using several techniques. While it's possible one set of isotopes may have coincidentally formed with an isotope ratio much younger than the dating would suggest, the possibility it formed with several such ratios all pointing to the same age is... well, very ",
" small. "
] |
[
"Zircon crystals have the added benefit of being resistant to chemical alteration and mechanically tough so they can stay largely unchanged after formation. \nAnd I second the cross checking, the fact that different dating methods from very different decay sequences converge is one of the best indicators of consistent half lives. ",
"There was also and experiment done with, I forget which element , but a sample of a radioactive element was stored in a safe for ~ 30 years, to fine tune the measure of its half life. "
] |
[
"although you can make adjustments to correct for changes if you know it isn't true",
"How do scientists compensate for this when attempting to use isotope dating on something like a fossil? Wouldn't the act of fossilization destroy any hope of being able to accurately guage the original isotope content?"
] |
[
"How probable are printed houses in 10 years? Are researchers right now accounting for all structural requirements?"
] |
[
false
] |
In light of the recent development in 3d-printing and the article about the USC professor who is working on printing a house in under 20 hours, I bet my dad that we would see a 3d-printed house in 10 years. He kept saying that it cannot be possible, speaking of at least a 2-story-house, because of structural requirements on ceilings and their weight-bearing capacities. So, how probable is a realization of this concept in the near future?
|
[
"If you talk about the structures only then it shouldn't be very complicated (and doable in 10 years, no sweat), there is a lot of other things to do when building a house though, just to name a few: the ground, electricity, plumbing, wallpapers, roof , heat, kitchen furniture, windows ...",
"What I have understood, it would be a little like buying a ruin that you'll have to completely renovate. A ruin created in 20 hours."
] |
[
"This machine",
" prints houses with openings for windows, pipes, and conduit, to avoid a lot of extra work to add those things in. Of course, the end result would be bare concrete walls, so certainly some people would want siding or drywall hung for a better looking exterior/interior, but still, that wouldn't take a long time compared to raising a stick built house."
] |
[
"Ok so since this guy has no clue what he is talking about. Let me give you a little more detailed explanation other than \"wallpaper\" and \"kitchen furniture\" for build requirements. ",
"So you have heard of 3D printed houses? Cool a lot of people seem to know this buzz word, but not many people know what the applications are. Let me focus solely on a home. And for your deadline a home built for low income housing. In a state with few housing regulations, or outside the US. ",
"\"Ground\" I assume you are referring to demolition and grading. This involves some sort of engineering depending on where you are let's assume you are getting a lot that has already been built upon. The most common (and immediate) application for this technology is replacing the very outdated stick gram homes in America as they are really only built for 60 years of safety of course there are variables to this time but that's not what we are talking about. Anyway you now have a flat build site with set in parameters as well as sewer and utilities hook up. Which might be replaced or might not. These are \"electricity, plumbing\"",
"\nSo we have all the preparations to build a house. This is required for any method of build, steel, concrete ect... But we are \"printing\"\nSo what our focus in 3D printing right now is multiple materials and accuracy of extrusion head. Let's assume we are wanting to build our structure in a concrete mix that hasn't been fully developed yet but allows us to pipe the concrete through an extrusion head and solidify almost immediately upon exit. Cool we can now make intricate structures instead of just 2\" walls. If the robotics (big ass servos with big ass motors) are strong enough to run one layer we can actually design the home with pipes electrical, fixtures, cabinets, furnature ect EVERYTHING you need in a house. By running multiple material type printers simultaneously in unison with each layer, say building pipes and electrical layer then run the support material around pipes and electrical then repeat you can actually have a pretty complex house and improve the design and function of existing architecture dramatically. If you are a good enough designer you can pretty much design this entire house bolt by bolt in a computer and send the commands to the printer (I can already do that small scale) ",
"If done properly all that we would need to finish the home is someone to literally slide the windows in place, add some caulking, screw on the doors to the pre-manufactured cabinets and door frames, bolt on light fixtures and the house is done. No \"wallpaper\" because modern homes use stucco which could essentially be dye added to our support material, heat could be printed in conductive wires in the floor or ducting could be designed in the computer so just bolt on a HVAC unit to the outside. And you are done. ",
"As for the roof have you ever seen an archway with a keystone? Well that would be essentially the same principle of engineering we would want to employ for the roof, and we could get some pretty beautiful designs from there. ",
"Now for OP's question\nNEVER underestimate technology so I would say everything I said above would be possible in 10 years. Honestly if I had the funding I could do it in 3. We are already building huts and small outbuildings in case study's using \"3D printers\" but for it to be something you would want to live in it's not too far off. Just takes a few visionaries like myself to keep plugging away at improving the world one giant leap at a time. ",
"Check out the architect Donald Wexler especially his case study neighborhood in Palm Springs for an idea of how 3D printed homes would be put together. He was a brilliant mid century modern architect who developed a way to pre-fab steel homes. I would assume the best way to manufacture a 3D printed home would follow his principle just on site. ",
"Oh and I'm an architect with 10 years of construction management experience who has been playing with 3D printers for a few years and left the field of construction to Get in the field of what I see as the future of construction and building design. Launching my own company selling 3D printed parts for various fields. If anyone is better at using python than I am and wants to PM me I could use some help!"
] |
[
"How are nutrients like fat, sugars, sodium, etc... removed from certain food products?"
] |
[
false
] |
How are fat and sugar removed from products like milk, peanut butter and fruit juice?
|
[
"Similar question but I don't want to start a new post - how do they removed caffeine from tea and coffee? "
] |
[
"Do you mean by manufacturers or in the body?"
] |
[
"By the manufacturers."
] |
[
"How does overlapping a conductor with an insulator prevent heat from dissipating further through the conductor?"
] |
[
false
] |
I have a question about the top portion of a thermos where the plastic cap threads into the steel flask.. How does the heat not continue to travel through that threaded portion of the steel? it appears to stop once it comes into any contact with the plastic. How does combining this Insulator with a Conductor prevent further heat transfer through the Conductor?
|
[
"It doesn't. Heat, just like electricity, flows most heavily along the path of least resistance (or highest conductivity). (i.e. \"electricity always flows through the path of least resistance\" except that statement is incredibly wrong and I have no idea why people always say it). Are you asking why the cap isn't hot? There I likely mostly makes contact with the rubber and there's an air gap between it and the rest (assuming we're thinking of the same type of thermos)."
] |
[
"https://futurism.com/wp-content/uploads/2014/10/Thermos.gif",
"From the image shown here, I would think the inside slightly down from the lip, it would start to get warm, but near the top you will have crossed the vacuum section and not get most of the heat transfer.",
"I would assume, so that they do not get sued when people burn themselves, that most manufacturers of items like this would leave the mouthpiece on the other side of the vacuum tube. That being said, if you have a specific manufacturer or model number, you could look this up in much greater detail."
] |
[
"No I'm not asking about the cap, but the metal opening where the plastic cap screws in to. In theory this metal opening should be hot, yes? Because this will be the path of least resistance. It's not hot at all though and it's doesn't make sense to me why that is. I was thinking it had something to do with the contact with the plastic."
] |
[
"How come I can eat salt and drink water but I can't drink salt water?"
] |
[
false
] |
[deleted]
|
[
"17 grams of salt is almost exactly 1 tablespoon.",
"So, OP, mix a full tablespoon in with your single glass of water and drink away. Add the same tablespoon per glass you drink once the first one makes you super thirsty.",
"edit: go ahead and try the \"mix it up and take a sip\" part. It's an extremely cheap test that is very eye-opening. Do not drink the whole thing..."
] |
[
"Just be ready to sit on the toilet for an hour as soon as you feel a fart coming on."
] |
[
"So at this point, are you better off drinking your post sea water urine?"
] |
[
"How will the world look in a few years, in terms of climate?"
] |
[
false
] |
[deleted]
|
[
"depends where you live really. Some places will get warmer, some will get colder. Some places will have less rain, some places will have more rain. In general though (some) extreme weather events will be more common. \n",
"http://www.nature.com/nclimate/journal/v4/n2/full/nclimate2100.html?foxtrotcallback=true"
] |
[
"this ",
"r/askscience",
". Not ",
"r/zodiac",
"...",
"\nWe are supposed to back up our claims with peer reviewed journals. It is not my fault that science has a problem with unreasonable paywalls. There are (illegal but in my eyes justified) ways around it though.",
"\nOP asked how things are going to change, but without any further information on his loccatioon it is not possible to make any definite claims. Yes of course the weather isn't going to totaly go crazy in the next years. I never claimed that. It is also quite obvious when you look at the 2 degree (celsius) change that all the politicians are talking about. Earth is still going to be inhabitable.",
"\nHere is a non-paywalled paper about the changes of the Palmer Drought Severity Index that also shows some maps with corresponding distributions. \n",
"http://www.cgd.ucar.edu/cas/adai/papers/Dai_pdsi_paper.pdf"
] |
[
"How many years are you talking about? ",
"I live in the upper midwest of the united states. There will be some changes here over the next ~50 years; some things like streamflow patterns will likely be profoundly changed. There will be significant changes to agriculture (for a variety of reasons, not all climate-related). It is likely that much of the coldwater fishery will be lost. But I would expect that in a vacuum life will continue much as it is now. ",
"Globally there are areas where there is far more vulnerability, however, and those are the folks who will get screwed. We can't know exactly where or exactly when (though someone with more top-of-the-head knowledge than I could make some good guesses), but climate refugees are already a thing and will continue to be. Currently inhabitable areas will become uninhabitable, areas that are currently too cold for ag will become arable. That means migration, and migration means conflict. The way in which climate change is most likely to impact people in the developed west is through global conflict, not directly through climatic risk. That's what scares me."
] |
[
"How do the different muscles in the body differentiate signals from the brain?"
] |
[
false
] |
The signal that tells the heart to beat is really strong, how do your biceps know not to move from it?
|
[
"They don't. Your brain sends the signals on the nerves that go to the correct region of your body.",
"Also, the signal that tells the heart to beat doesn't come from the brain; it comes from inside the heart itself. (The heart does regulate how fast the heart beats, but a heart with no input from the brain will not stop beating.)"
] |
[
"With enough fuel and the appropriate nutrients and the proper environment, it's possible it would continue to beat for a long time before normal cellular senescence would cause it to fail. "
] |
[
"Depends if he chewed it - if he did it would have stopped beating immediately, if not, a minute or 2 maybe. Long enough to be kind of gross."
] |
[
"Why do wet clothes stick to your skin when water acts like a lubricant for most objects?"
] |
[
false
] | null |
[
"Am I mistaking in that water does not act as a lubricant for most objects?"
] |
[
"Just think about all of the slippery when wet signs or slip n slides. Doesnt water lubricate fairly well in gerneral?"
] |
[
"I think it has to do with the impurities on the surface not the actual water itself. I do NOT know for certain though, I did some lazy research I could not find much about it. Hopefully someone who knows what they are talking about answers your question"
] |
[
"If you let a chess-computer play itself repeatedly, will it play the same game over and over?"
] |
[
false
] |
I would assume that there has to be some random variation in the choice of moves, at least in the early part of the game, right?
|
[
"This would depend on the AI. Most Chess AI's have some \"fuzzy logic\" built into them so they don't necessarily make the best choice in a given situation, meaning they may not always make the best move. ",
"It also depends on how far ahead the AI looks (this is big factor), as depending on how far ahead it looks, it may under or over estimate a particular moves performance impact.",
"So short answer: No, they will not play the same game over and over.",
": as ",
"/u/Rioghasarig",
" pointed out, the AI's \"look ahead\" factor doesn't affect OP's question, but it's more of a general \"this how an AI picks it's move\"."
] |
[
"If the fuzzy logic is based on a random number and it isn't reseeded, they might play the same game."
] |
[
"This is true, and this is where the \"it depends on the AI\" part comes in. Most ",
"PNRGs",
" use UNIX time as a default seed, so every time a new game occurs the seed will change meaning new moves.",
"However as you've said, if for whatever reason you use the same seed then yes you are likely to get the same game, but I don't know why you would hard code your RNG with a particular seed."
] |
[
"What is the leak up rate on the ISS?"
] |
[
false
] |
I work in PVD systems in a Chip Fab. The typical leak up rate, or "rate of rise" on our chambers is in the XX nano torr range. These chamber are small volume along the lines of 6-10K cubic cm. So we have hard vacuum and try to keep the atmosphere out. In comparison, the ISS is huge, is in hard vacuum and is trying to keep the atmosphere in. How much pressure is lost over a set period of time say a day, and how do they compensate? Is there bottled gas (air) on every payload coming to the ISS? Is the atmosphere mix the same as on earth or combination of fewer gasses
|
[
"Here's a NASA paper on the ISS leak rate: ",
"http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110012997_2011013524.pdf",
"Excerpt:",
"The current trending results cover data from October 2004 through February 2011. During this time period the \nISS leakage rate has increased from ~0.064 kg/day (0.14 lbm/day air) to ~0.227 kg/day (0.50 lbm/day air)."
] |
[
"Converting to volume at STP: It increased from 52 to 180 litres per day (ISS has normal air at sea-level atmospheric pressure)."
] |
[
"This page supports your statement: \"The astronauts in the Gemini and Apollo programs breathed 100 percent oxygen at reduced pressure for up to two weeks with no problems.\", but it also iterates a bunch of dangers (that may not apply on the ISS).",
"You may want to google \"Apollo 1\" for the reason NASA went away from pure oxygen environments."
] |
[
"What happens when an electron loses energy but is already at the shell closest to the nucleus?"
] |
[
false
] | null |
[
"That's the thing, it can't! This is actually one of the key properties of quantum mechanics, namely that energy levels are quantized (i.e. discrete) and transitions can only occur between them. One a system is in its lowest energetic state, it cannot relax down any further! So to take the case of an electron in an atom, say hydrogen, if the electron is in the state 1s, it cannot lose any energy because there is no lower energy level it could relax to."
] |
[
"A really cool example of this, coupled with the Pauli Exclusion Principle, is the existence White Dwarves and Neutron Stars. These compact objects would collapse under their own gravity if you only accounted for the classical pressure. However, since electrons/neutrons can't go to arbitrarily low energy, once the gas of electrons are in the lowest possible energy state, they remain in that state, acting as a sort of pressure and preventing collapse. This is often called the \"degeneracy pressure\" even though it really isn't a pressure in the traditional sense of the word."
] |
[
"/u/crnaruka",
" is correct, there is no atomic state lower than the ground state. However, in some isotopes, the electron can get captured by the nucleus, turning a proton into a neutron and lowering the entire energy of the atom further."
] |
[
"Why do my clothes feel “crunchy” after drying them on a clothesline?"
] |
[
false
] |
I’m American, and normally dry my clothes in a machine dryer and they always come out feeling soft, even if I don’t use any fabric softener or dryer sheets. I’m on vacation in Italy and have had to dry my clothes outside on clotheslines in several places, but they always feel rough and crunchy once they’re completely dry. What’s the difference?
|
[
"The short answer is that when fabric dries slowly and without being disturbed, the fibers that make it up can slowly arrange into large ordered domains. These domains in turn will make the fabric more rigid locally, which in turn will make it feel coarser and stiffer. This effect can be made worse if the water is hard since the minerals in the water can strengthen the arrangement of the fibers. ",
"If you want a more detailed answer you have to go back to the microscopic structure of the fabric. In this case let's look at cotton. Cotton is mostly made up of a messy array of cellulose fibers that look ",
"something like this",
". These fibers can relatively slip past each other to some extent, which is why initially the fabric can feel soft. But when you immerse the fabric in water these chains will swell. The water will tend to break up the hydrogen bonds between the fibers, allowing them to move even more freely. In more technical term we say that water acts as a ",
"plasticizer.",
" It's largely for this reason, for example that you want to add water when ironing clothes. ",
"Now as the water dries the polymer fibers will relax again by forming hydrogen bonds to each other. But now because they can move so freely when wet they can order themselves in larger domains. These ordered domains in turn make it harder to deform the fabric locally. As a result the material will feel rough on the surface and it will be stiffer as well. As I mentioned earlier this effect can be exacerbated if the water if very rich in minerals (hard) as the inorganic species can stabilize these local domains even more. ",
"Of course these changes also occur to some degree when you dry clothes in a dryer. However if the dryer makes the clothes tumble as they dry, it reduces the chance for larger ordered domains to form, so the effect is usually not quite as bad. On the other hand on a clothesline you allow the water to dry more slowly and the fabric stays still, which greatly helps the fibers arrange thesmselves locally. "
] |
[
"Thanks! Wasn’t expecting such an in-depth reply, and I appreciate it!"
] |
[
"He says that at the end of his first paragraph..."
] |
[
"Why do we have 2% milk, but not 3%, or 10%, or 50% milk?"
] |
[
false
] |
This might seem like a silly question for , but I figure there must be some science behind this, or else at the very least for marketing purposes we'd have all sorts of percentages of milk on our grocery store shelves.
|
[
"Because milk is about 4% fat in its natural form. If you like the idea of 50% or more you could put some ",
"St Andre",
" on your cornflakes."
] |
[
"Half and half just means half cream, half milk. It doesn't have to do with the overall fat percentage."
] |
[
"The percentage refers to the percentage of fat in the milk/cream. Cow milk contains about 3.6% fat, in many places you can buy this (whole or homo milk). Half and half is halfway between milk (2%) and table cream (18%). Whipping cream is 40-45% fat. "
] |
[
"\"Jack Andraka, 15, invents cancer test that is 168x faster, 26000x less expensive, and 400x more sensitive than the current standard. 3¢ and 5 minutes.\" Is this an actually proven method or is just being hyped by the press and ignoring some shortcomings of it?"
] |
[
false
] | null |
[
"In any of these \"teenager discovers X\" stories, the news articles always have almost zero details on what the person actually did, and this is no exception. What usually happens is that they are doing an internship in a professor's lab, and the internship goes well, and it gets picked up by the news, ignoring the details about the already existing infrastructure in the lab.",
"According to Jack's profile on the science fair website, he did things like Western blots and ELISA, and used an electron microscope. These are not things a 15 year old can do at home or in a highschool science class; the equipment costs tens of thousands of dollars or more. If you find the name of his supervisor, you'll find the lab where this work was done."
] |
[
"Basically he applied analytical strategy - paper-based assays - to antibody detection of a particular marker for cancer. None of these are novel individually, as these are all widely researched methods.",
"Are those numbers on speed, cost, and sensitivity ",
" - perhaps. I have not seen a number for ",
" though, so the utility of the test are yet to be seen. In other words, you can put a drop of positive sample into this thing and see it work so cheaply and quickly - and the media runs out the door screaming \"15 year old is leading the battle against cancer\". What happens when you put a drop of negative control on this? That's not exciting to report.",
"So yes, this is most definitely hyped by the press. This most likely will not be a ",
"gold standard test",
". It ",
" be a screening test, if there are no specificity problems - and that's a big \"if\". What is ",
" mentioned in the media is that most promising ideas never leave the lab bench. Did he come out of this idea on his own? He probably had ",
" of guidance along the way.",
"That said, this is more than an average fifteen-year-old would have achieved."
] |
[
"While this article doesn't give much information, there is a ",
"TED talk",
" given by the kid that goes into more detail. He did the research at home and then wrote approximately 200 labs requesting to use their equipment. After some persistence, one let him use their equipment."
] |
[
"Sound waves as an anti-weapon"
] |
[
false
] | null |
[
"Best sonic device I know of is the L.R.A.D. It isn't anywhere near potent enough to dismantle hardware (although it'll bust the hell out of human eardrums)."
] |
[
"This is what you see police/swat using to break up violent protests on YouTube correct? "
] |
[
"indeed."
] |
[
"Why do people kill horses almost immediately whenever they break a leg?"
] |
[
false
] |
I've heard on several occasions that horses are put down whenever they break one of their legs. Why are they unable to get treatment like us?
|
[
"Here",
" is a great pdf review of this issue. There's a series of complications in horses that make limb fracture repair very difficult. #1, Horses cannot be kept lying down for very long. Their respiratory, circulatory and digestive systems all begin to fail rapidly. (see ",
"here",
" for a review of complications under general anesthesia in horses. ) So they have to stand, which brings us to #2: Their body weight is so great that it's very hard to keep weight off the injured limb, and they have a high tendency to then injure the \"support limb\" (the uninjured limb). Particularly the support limb tends to get laminitis, which is separation of the hoof wall from the hoof bone - essentially the hoof begins to tear apart so that the limb bones begin to punch right through the bottom of the hoof. It's excruciatingly painful for the horse, is very hard to reverse and is often fatal. Also the surgical plates and screws developed for human fracture management often are not sufficient to bear equine body weight - there are cases of metal-and-screw repairs simply ripping right out of the bone that they were screwed into. Third: Horses are both not very intelligent and also very strong, and they have an unfortunate tendency to struggle with the cast and reinjure themselves. There's been a particularly sad problem in which the horse thrashes while coming out of anesthesia such that they either destroy the broken limb again, and/or end up breaking another limb. See ",
"here",
" for a typical case report. This is what killed ",
"Ruffian",
", for example. This is a serious problem - to quote the first-cited ref, \"postoperative recovery from anesthesia proved to be a major hurdle, with animals tearing apart in the recovery stall in a few seconds the efforts of many tedious hours of anatomical reduction and fixation of long bone fractures in the operating room.\" The best way around this is to lower the horse (by crane) into a swimming pool while it is still unconscious so that it wakes up in the swimming pool, then lift it out again (by crane again) once it's awake - obviously this is difficult and expensive. (This is the ",
"\"pool-raft recovery\"",
" method. Pic ",
"here",
". And ",
"here's",
" a full story about trying to fix the racehorse Barbaro's broken leg, with a pool raft photo.)",
"Fourth, a practical reason: Most owners can't afford it. Most horses are kept for practical jobs where they need to be able to run, jump, and carry a human's weight. Limb fracture repair is incredibly expensive and the horse will almost never be able to return to full use again. You're talking extremely expensive surgeries, then pool/sling recoveries, then months of intensive care, often with physical therapy in special horse-accommodating swimming pools, etc. Typically the only owners with BOTH the funds AND the desire to do this are owners of a racehorse that will be valuable at stud even if it cannot run again.",
"All that said though, some fractures can be repaired. There are now \"standing fracture repair\" procedures (",
"ref",
") in which minor fractures can be repaired with the horse upright and conscious the entire time. There are much better ",
"limb casts for horses",
" available now, and better bone screws. Minor fractures in the small bones of the hoof can often be repaired nowadays with weight-bearing casts that allow the injured limb to take some weight and spare the support limb. See ",
"here",
" for the \"external fixator\" (3rd photo down) to see an example, and scan further down to see a horse wearing an external fixator. (btw those pics are from the review cited at top.) The pins go straight through the leg bone and connect to a brace that holds the horse's body weight. You can only use external fixators for certain fractures that are in the lower part of the leg.",
"But even with all the above advances, serious open fractures of the main bones of the leg are still very hard to treat - ",
"this study",
" reported only 12% survival in such cases.",
"edit: typos",
"edit2: Great comments everybody, and sorry for the lack of responses - I wrote this yesterday on my day off, but I have to work full-time on a grant & some papers today."
] |
[
"Well for one thing, there are no more truly \"wild\" horses. \"Wild\" horses today are actually feral horses, meaning that they were originally in captivity. \"Wild\" horses in the Americas were introduced in the 1490's by none other than Christopher Columbus. The last of the truly wild-type horse species (Przewalski's horse) went extinct in the wild in the 1960's but have been successfully re-introduced. According to Wikipedia, there are around 300 of them in the wild as of 2011. ",
"*edited to be factually correct as pointed out by pathodetached."
] |
[
"If a wild horse broke its leg, it would have probably have died. Most animals who break a leg in the wild die. Especially animal who rely on running to live."
] |
[
"Some questions on lobotomies"
] |
[
false
] |
I am familiar with the history of this procedure. My questions are about people today. How are people who had lobotomies back in the fifties and sixties doing today? How have their brains compensated? How do they behave? Can an MRI exam show if a person had a lobotomy? Do MRI exams given for other reasons sometimes show that a lobotomy was performed without the person's knowledge? (This sounds sinister, but please try to answer if possible.) I understand that lobotomies are still used (rarely) today. When are they performed, why, and what are the outcomes in general? Anything else interesting? Thanks in advance.
|
[
"Check these people out:",
"Howard Dully",
"Alys Robi",
"Rosemary Kennedy"
] |
[
"From wikipedia",
"As Dr. Watts cut, Dr. Freeman put questions to Rosemary. For example, he asked her to recite the Lord's Prayer or sing \"God Bless America\" or count backwards. ... \"We made an estimate on how far to cut based on how she responded.\" ... When she began to become incoherent, they stopped.",
"That's the most fucked up thing I've ever heard."
] |
[
"No. It worked to damage the brain of patients who could not otherwise be controlled with medication, thereby essentially making them \"vegetables\". "
] |
[
"How does the heart work differently in space compared to earth?"
] |
[
false
] |
[deleted]
|
[
"Blood does not fall into the ventricles, the atria contract and force it in. If the circulatory system relied on gravity we wouldn't be able to lie down or hang upside down."
] |
[
"This is true, but it doesn't fill the ventricle because of gravity, but because of the lower pressure. That is basically how the blood moves trough the body, by following lower pressure. Gravity does affect blood flow in some way, but it's mostly in the extremeties, like your feet getting swollen if you stand/sit for long periods. You wouldn't get that in space as the blood in the veins would not be working against gravity."
] |
[
"This is true, but it doesn't fill the ventricle because of gravity, but because of the lower pressure. That is basically how the blood moves trough the body, by following lower pressure. Gravity does affect blood flow in some way, but it's mostly in the extremeties, like your feet getting swollen if you stand/sit for long periods. You wouldn't get that in space as the blood in the veins would not be working against gravity."
] |
[
"What direction do hurricanes spin in the equator?"
] |
[
false
] | null |
[
"They don't! ",
"This",
" is a map showing the paths of every tropical cyclone recorded in the past hundred or so years. They never cross the equator, and they never really get close to it either because the spin of hurricanes (and tropical storms, typhoons, etc) is due to the Coriolis force, which decreases in magnitude as you approach the equator and is zero at the equator. Most storms tend to veer away from the equator, and if a storm did approach the equator it would just slow down and dissipate."
] |
[
"This is how big clumps of clouds act at the equator:\n",
"https://vimeo.com/144409131",
"Away from the equator, big clumps of clouds start spinning and spontaneously form into tropical cyclones (hurricanes):\n",
"https://vimeo.com/144409194"
] |
[
"These simulations are neat! Can you tell us more about them? Is the convection from a Boussinesq approximation? Is the Coriolis force in the second simulation constant, or a beta plane?"
] |
[
"Gauss' Law: Say I have a charge +q inside a cube but it is not in the center. Is the flux through each face the same or is greater for closer faces?"
] |
[
false
] | null |
[
"The fluxes through each individual face will not in general be the same (the ones closer to the charge will have a larger flux), but the total flux through the cube will just be q/e",
"."
] |
[
"That was my thought because E is stronger at closer distances. However the flux integral has a factor of cos(theta) introduced via the dot product. The near face will have a greater magnitude of E but flux lines through that face have a greater theta and thus smaller cos(theta). The far face has a larger cos(theta) but E has a smaller magnitude. I wasn't sure if the two effects canceled precisely or if E ~ 1/r",
" weighs more than the angular change. Does that make sense?"
] |
[
"Working it out for the general case would be hard and maybe not even possible analytically. But it seems to me like the 1/r",
" would win out over the cosine, at least for most cases."
] |
[
"Does a person who is unfit use more calories doing the same level of exercise for the same time as a fit person who is the same height and weight?"
] |
[
false
] |
A fit person will of course have greater endurance at the same level of exercise but do they actually use less energy over the same time period as an unfit person of similar BMI. If it is the case that they use more energy what are the differences that cause this?
|
[
"You can't answer no when that wasn't the question asked. It was about calories, not the source of those calories. For all intents and purposes calories from fat are the same as calories from glucose due to the TCA cycle and subsequent pathways making them interchangeable. ",
"It doesn't answer the question of whether they use more or less energy overall."
] |
[
"What makes someone fit? A good measure is the anaerobic threshold - the point at which the body's metabolism is so high that it can't rely mainly on aerobic respiration (with oxygen) and instead there is a significant amount of anaerobic respiration (without oxygen). Anaerobic respiration is inefficient because for the same amount of energy (calories) you get less work done because fewer energy is channeled to the muscles (in the form of ATP). ",
"Fit people have a better blood supply because capillary beds are more developed within the muscle. So more muscle cells can receive blood which supplies oxygen, and hence less anaerobic respiration occurs. Also, better developed capillary beds have less resistance and the body needs to spend less energy making the blood move through it.",
"Furthermore fit people can supply blood faster and more of it to the muscles, as a result of their better functioning heart. ",
"Muscle cells in fit people also tend to adapt by altering their levels of gene expression so that they favour enzymes that help carry out efficient respiration, both aerobic and anerobic. The more efficient your respiration is, the less energy you need to carry out the same amount of exercise.",
"Hopefully that answers your question?"
] |
[
"Depends on the exercise but your movement pattern efficiency may be higher leading to increased work volume for amount of energy. Not really more \"fit\" in terms of aerobic or anaerobic capacities but can use the energy better for the task at hand."
] |
[
"If the particle discovered as CERN is proven correct, what does this mean to the scientific community and Einstein's Theory of Relativity?"
] |
[
false
] |
Source: *at CERN!
|
[
"First, to reiterate what's been stated here, yes other experiments will need to find similar results. What bothers ",
" about the result is ",
"SN1987a",
". This supernova is 168000 light years away from earth. So if neutrinos gain 60 nanoseconds for every 730 kilometers they should gain ",
" of time for this supernova. But we discovered neutrinos only 3 hours before, and that's due to the fact that the supernova is largely transparent to neutrinos, but delayed the emission of light (the neutrinos got a head start, but traveled slower)."
] |
[
"Not that I doubted you but I wanted to confirm your math ",
"http://www.wolframalpha.com/input/?i=distance+to+sn1987a+divided+by+730+kilometers+times+60+nanoseconds+answer+in+years+"
] |
[
"Just clarify, this isn't a new particle discovery, as implied in the post title. This just just the apparent measurement of an already know particle travelling faster than light, which contradicts Relativity Theory."
] |
[
"Are submarines affected by storms? In other words, how 'deep' do storms go?"
] |
[
false
] | null |
[
"I served on the nuclear submarine USS Spadefish (SSN-668). At normal operating depths even a large storm on the surface would not affect the submarine. The Navy FAQ on submarines says that violent storms may be felt as deep as 400 feet ",
"Navy Submarine FAQ",
", see item 21. The deepest we ever felt surface effects was about 150 feet and it was pretty good sized storm on the surface above us. "
] |
[
"No. ",
"If you look at either salinity or temperature data for a specific area, you will notice that at some point the salinity (If you are close to shore) changes abruptly. That point is called the pyncocline. In deeper waters you will see the temperature change abruptly, that is called the thermocline. ",
"Below either of these lines, there is little to no mixing of water from above. So as long as the submarine goes below those levels, they should feel no ill effect from the storm. ",
"The precise level varies from place to place, sometimes significantly. "
] |
[
"This is a concept in oceanography known as ",
"Storm wave base",
". The extent to which a wave affects the ocean is roughly 1/2 x its wavelength. My sedimentology textbook (Principles of Sedimentology and Stratigraphy, Samuel Boggs, fourth edition) cites Komar et al (1972) which states storms can affect the ocean as deep as 200m. So to answer the question, yes, they can in theory, but only in depths of <200m. Beyond that as the other posters have said, waves do not significantly affect the water."
] |
[
"Where does the bacteria in the human digestive tract come from?"
] |
[
false
] |
I've always wondered.
|
[
"We are born sterile but get colonized as soon as we are born through the vaginal canal or c-section. Its not only in the digestive tract but essentially everywhere there is an epithelium that separates us from the outside world (skin, nails, hair, nostrils, etc...)\n",
" As pointed out by ",
"/u/potatoisafruit",
", there is recent evidence suggesting that colonization occurs even before birth. Interestingly, this pre-birth colonization seems to have a ",
"protective effect against potentially pathogenic bacteria in the vaginal canal",
" "
] |
[
"Breast milk may also help to colonize an infant's gut microflora: ",
"http://www.ncbi.nlm.nih.gov/pubmed/20176122",
"\n",
"http://www.ncbi.nlm.nih.gov/pubmed/17922969"
] |
[
"We are not born sterile. Research this year has shown ",
"the placenta harbors a rich microbiome",
" before a baby is born. "
] |
[
"Can somebody give me an example of a predator and prey duo that have a very recent common ancestor?"
] |
[
false
] |
(Sorry if this is a dumb question.) -not counting cannibalism I was just thinking about how long it would take for two species to diverge from the same organism and become predator and prey. So, I wanted to see if someone could let me know which predator and prey duo are most closely related, with the knowledge that is available at this time.
|
[
"Fireflies are a great example. Nearly every species is poisonous to some degree. Except for those in the genus photuris. This group has lost its ability to produce poison. To compensate, the females of this genus can reproduce the light patterns of the closely related fireflies in the genus photinus. When the male photinus approaches the female photuris doing her mimic flashes, she grabs and devours the male. Her tissues then accumulate the poison the male had produced.",
"Thus, an otherwise non-toxic firefly genus regains its poisonous heritage by seducing and eating her genetic cousins."
] |
[
"there are spiders that specialise in preying on other spiders and even mimic breeding behaviour to get in range to strike, killer whales prey on other dolphins, but the closest thing I can think of is that female fireflys lure and eat the males of other species."
] |
[
"An interesting example you may or may not consider recent: Tanganyikan Cichlids (also other African rift lakes, but T. is the one I'm most familiar with).",
"Lake Tanganyika was largely isolated from other water bodies around 10-12 million years ago, and a common ancestor fish evolved in the absence of competition to fill many evolutionary niches.",
"There are now something in the order of 80 species in 12+ tribes, some of which prey specifically on others.",
"Fascinating creatures by the way!"
] |
[
"Is it possible to make a stealth car that would be invisible to a speed radar?"
] |
[
false
] | null |
[
"There are three fundamental approaches to radar stealth: absorption, deflection and transparency. Absorption means using some sort of material to absorb the radar energy, which obviously prevents it from being detected. Deflection means trying to send the radar energy somewhere else other than back towards the detector by reflecting it off in another direction. This is the main reason for the funny shape of the ",
"F117 Nighthawk",
", for example. Transparency means making the target out of a material which will simply allow the radar signal to pass through. ",
"Successful stealth aircraft and ship designs use a mixture of these techniques, and you will need to do the same to make your invisible car. Assuming you were starting with a normal car, the best place to start would be to add a faceted skin over the car. Make sure your faceted skin is convex or at least nearly convex and is made out of a highly conductive material. Make extra sure that anything that could act as a dihedral (two plates joined at right angles) or trihedral (three plates joined in a corner) is well covered. Typical chassis designs use a lot of these shapes, so you'll want to concentrate on those parts of the car most. The key is to avoid any concave (inwards) corners in the skin of your craft.",
"You'll also want to get rid of as much uneeded metal as possible. Concentrate on metal that is perpendicular or nearly perpendicular to the direction of motion of the car. Replace with a non-conductive and low density material. Next, look into adding some ",
"RAM",
" to remaining hotspots. It is important to chose your material carefully based on the radar wavelengths used by local law enforcement.",
"You'll need to test your design. Many military and large university radar labs will have a turntable in an anechoic chamber which can be used to test the RCS (radar cross section) of your vehicle. Few labs will have one large enough for a full size car (though they do exist), so maybe a scale model would be appropriate (although be sure to apply suitable correction factors to account for scaling).",
"Finally, hope that your local law enforcement doesn't invest in any ",
"multistatic radar",
" equipment. Multistatic radars change the stealth game, and will make basic designs quite difficult.",
"Active countermeasures (like jamming) are a completely different topic. Even the very simple jammers commercially available today are highly effective against crude narrowband pulse-doppler radars widely used in law enforcement. You can not reasonably expect this to be the case into the future. You will need to invest significantly in countermeasure development, including thinking about direct detection of your countermeasures and counter-countermeasures, to keep ahead of the law.",
"Good luck. Good luck indeed."
] |
[
"Radar speed detectors work by detecting the Doppler shift of a microwave signal reflected from the vehicle. As the vehicle moves towards the radar, the wavelength of the microwaves reflecting off it are decreased (frequency increases) which is then detected by the gun and converted to a speed reading.",
"Modern LIDAR (light detection and ranging) speed guns use pulses from an infrared (I think) laser beam reflected from the vehicle. The time taken for the laser to reflect from the vehicle and return is recorded for multiple pulses, and these multiple distance readings are used to calculate an accurate speed for the vehicle.",
"To make the car invisible to the Radar or LIDAR speed detector, you need to prevent the beam from reflecting. Radar absorbing paints have been used on aircraft for years, but the license plates, headlamps, and other flat reflective surfaces will be the main problem as they are much harder to hide. You could jam the speed detector with a high-power signal transmitting at the appropriate frequency (with Radar you need to shift the emitted frequency based on your speed) or detect microwave signals from a distance, but this is very easy to detect and is illegal in many states and countries.",
" It is possible to apply a radar and infrared absorbing paint, but headlamps, license plates, and other highly-reflective flat surfaces would still reflect the beam."
] |
[
"This episode",
" of MythBusters may be helpful."
] |
[
"How do anti-matter and black holes interact?"
] |
[
false
] |
My question arises from my pondering the matter/anti-matter asymmetry in the universe. Would it not theoretically be possible for the matter that makes up a black hole to actually be anti-matter? What then would happen when regular matter "fell" into the black hole? If it annihilates like a normal matter/anti-matter reaction I'm assuming the black hole would keep all of that energy contained. Would there ever be a way to test this hypothesis?
|
[
"A black hole, to the best of our knowledge, can be completely characterized by three numbers: its mass, its charge, and its rotation speed. If there exist other forces in Nature that we don't know about yet, then a black hole could also interact through those, and so you'd have more numbers. But importantly it's neither matter nor anti-matter. This is because if you had matter and anti-matter both falling into a black hole, even though they might annihilate each other, in doing so they would release energy, usually in the form of photons, and those would fall back into the black hole and increase its mass by exactly the same amount as if the matter and anti-matter hadn't annihilated. So at the end of the day the black hole doesn't care whether the stuff that formed it was matter or anti-matter."
] |
[
"Absolutely. Photons have energy, and so the black hole's mass increases by an equivalent E/c",
" (per a famous formula). This is because as far as gravity is concerned, mass and energy are two sides of the same coin, and both create gravity."
] |
[
"A photon has zero mass, but a finite energy. To a black hole, there's no difference between mass and energy, so when a black hole absorbs a photon, its mass increases by E/c",
" The energy of a photon is equal to Planck's constant times the photon's frequency (E=hv)."
] |
[
"Is it possible to somehow allow us to stay on another planet?"
] |
[
false
] |
Assuming terraforming and all that jazz has already been taken care of. I read on here a while back that if we were to go to a different planet with different rates of gravity, it would make us pass out due to blood not moving correctly. Is there a way to prevent this?
|
[
"The moon has a gravity of 1/6th that of Earth. The astronauts there did not pass out.\nHigher gravity can actually do this, and fighter pilots sometimes experience this in high-g maneuvers. A tightly constricting suit on the lower limbs can help somewhat, but it only extends the range somewhat, and is really only going to be useable for a relatively short time.",
"http://en.wikipedia.org/wiki/G-LOC"
] |
[
"There is also the problem of bone loss. All in all, this means that humans can't live on another planet in large number for long periods of time, unless its gravitational acceleration is fairly close to Earth's, or we develop technology that can overcome those problems."
] |
[
"Evolution assumes Natural Selection. For the most part, humans have removed natural selection from the equation. There's very little in the way of evolutionary pressure in \"modern\" society, so I wouldn't think evolution would be a major factor outside of re-introducing eugenics to our theoretical space colony. "
] |
[
"Eliminating Sleep with Neurotransmitter Monitoring and Intervention?"
] |
[
false
] |
Has any one read any studies of active neurotransmitter regulation to extend periods of wakefulness and thus eliminating the need for sleep and or reducing mental fatigue? Just by briefly reading through this study (and many others): it would sleep by artificially controlling or augmenting neurotransmitter levels that are regulated during sleep, particularly REM and stage 2 stage sleep, one could extend productive wakefulness exponentially or indefinitely. The brain depletes neurotransmitter levels throughout the day. By artificially balancing neurotransmitters could we permanently stay sharp and alert other than any psychological effects like altered perception of time, etc. ? I'm imagining a sort of insulin/morphine pump type device in the distant future that would continually monitor neurotransmitters and keep them perfectly balanced for refreshed wakefulness and productivity. I realize that our current understanding of the some odd 50+ identified neurotransmitters in the brain is very limited but in theory they could all be managed chemically/artificially. It would seem that the days people are sharpest and at their best mentally, their brain is chemically balanced. Could we artificially perpetuate this balance? By keeping the brain at its optimum chemical balance we would gain more benefit to cognitive function than any nootropic 'stack'. Other benefits could be in resetting 'sick brains' : eliminating anxiety, depression, other mental illnesses. I have had good luck with neurotransmitter supplementation of tyrosine, tryptophan, choline, and glutamate. Both with productive wakefulness and keeping a sharp mental edge so to speak. Could something like this be carried out in an extreme fashion should our understanding of the brain increase dramatically in the next few decades (which it will, eventually). Is this idea too far fetched? Any thoughts? I'm interested directly in neurotransmitter level intervention and effects on sleep and productivity. While orexin-A and modafinil are of interest, they are only acting artificially on receptors. Any thoughts, discussion, or links to research would be appreciated to satisfy my curiosity.
|
[
"The type of technology you are describing would be extremely unlikely to work. The main reason for this is that you would be overcoming the drive for sleep without addressing the functional need to sleep. It would be something akin to taking appetite suppressants to eliminate the need to eat -- this doesn't address the fundamental need to obtain energy. In the case of food, this can potentially be addressed through IV infusions. But there is no such simple equivalent for sleep, i.e., there is no chemical you can pump into the body to just replace the need for sleep.",
"Could we block the urge to sleep with pharmaceuticals? Quite possibly, yes. We have a reasonably good understanding of the neurotransmitters that promote different states of arousal. These can be manipulated (e.g., using modafinil or amphetamines), although with serious side-effects. We are also developing an understanding of the substances that accumulate in the brain that drive sleep, e.g., adenosine, IL1, prostaglandin D2, and NO. Caffeine works by temporarily reducing the effects of adenosine by acting as a competitive antagonist. We also understand the basis for the circadian clock, which promotes sleep at night and wake during the day, and in the future it could potentially be manipulated.",
"But all this overlooks the fact that life on Earth is fundamentally geared to have daily cycles of rest and activity. Circadian rhythms are ubiquitous down to the single cell level and sleep exists in every organism where we can reasonably define it. It is not a simple matter of just blocking some pathway or taking some stimulant -- ",
" aspect of our physiology is evolved to sleep.",
"Sleep serves myriad functions for the brain, including memory consolidation, synaptic pruning, and restoration of ATP stores. We think that these sleep processes are fundamentally incompatible with waking neuronal activity, i.e., it is necessary to take the network 'off-line' to perform certain types of maintenance. Cetaceans (e.g., dolphins) provide compelling evidence for this, and show an alternative strategy. They cannot afford to fall asleep completely, else they could drown or be predated. They get around this by sleeping unihemispherically -- switching one half of their brain off at a time.",
"If it were possible to maintain consciousness while performing all the functions of sleep, there would be little reason not to evolve that ability. The only plausible reason would be to keep you out of trouble by forcing you to lie unconscious rather than interacting with your environment. The argument being that it's safer and/or more efficient to behave this way. However, many species sleep in the open and are more vulnerable by virtue of being unconscious.",
"Sleep also serves fundamental functions for all the other systems of the body. Even supposing we could keep the brain in a perpetual state of wakefulness, we would not be addressing the roles of sleep/wake cycles in normal immune function, metabolic function, cardiovascular function, growth, protein synthesis, etc."
] |
[
"Think of how the body recovers from three days of sleep debt, it doesn't catch up by sleeping for 24hrs - most likely 8-14.",
"That is an outdated view. In fact, we now know that sleep debt accumulates on much longer timescales and ",
"there is something like a need to make up each lost hour",
". The problem is that the more sleep you lose, ",
"the worse your ability to subjectively assess your level of objective impairment",
".",
"I think perhaps if neurotransmitters were supplemented in addition to REM naps, one could theoretically hack sleep.",
"Like I said, that's not how it works. Sleep isn't just for the brain. Also, there's no evidence to suggest that REM sleep is more important than NREM sleep. In fact, our best validated measure of sleep need and the restorative value of sleep is NREM slow wave activity.",
"Steve Pavlina, while definitely not a scientific man, had very interesting experiences under polyphasic sleep and did quite well on just a few hours of sleep without neurotransmitter intervention.",
"Polyphasic sleep in humans has no scientific basis. Polyphasic sleep regimes effectively put people on an ultradian sleep/wake cycle, i.e., shorter than 24 h. Under those conditions, there are times during the day when it is nearly impossible to fall asleep, due to the circadian rhythm in sleep propensity.",
"http://www.sciencedirect.com/science/article/pii/0013469486901239",
"http://jcem.endojournals.org/content/38/6/1018.short",
"http://www.sleepforscience.com/stuff/contentmgr/files/8ed8b627e1f3848d6160a9c2a87f13b5/pdf/carskadon_dement_1980.pdf",
"The result is insufficient total sleep time across 24 h and chronic sleep restriction, unless one allows 12+ h of time in bed per day, which completely defeats the purpose of such schedules. Such schedules also disrupt the usual architecture of REM/NREM sleep cycling.",
"Other than rapid eye movement, very little physically occurs during REM sleep - brain processes are almost entirely chemical in the sleep stage.",
"That is not correct. There are many physiological changes associated specifically with REM sleep. I don't know what you mean by \"brain processes are almost entirely chemical in the sleep stage\". When are brain processes not \"almost entirely chemical\"?",
"By 'hacking' the brain chemically we could work against these natural processes.",
"What I am saying is that there is no way to achieve this. We are not large herbivores. ",
" of our physiology has evolved over millions of years to need approximately 8 hours of sleep per night. That is not something that you can address with chemical supplementation. You would have to rebuild every aspect of our biology.",
"We already eat higher caloric diets should we choose and have artificial lighting and such.",
"Sure. But these are all at odds with our evolved biology. Can we develop ways of mitigating the urge to sleep? Absolutely, we already have several ways to doing that, e.g., caffeine, light, stimulants. But those will always come at the cost of not performing the functional needs associated with sleep.",
"I've given you an answer based on our best knowledge of the science today. If you want to turn this into a speculative discussion, I recommend posting to ",
"/r/AskScienceDiscussion/"
] |
[
"The VLPO is a sleep-promoting nucleus in the hypothalamus, but it is not the only mechanism that drives sleep. Lesioning the VLPO results in a ",
"reduction of NREM sleep by about 50-60% in rats",
". I'm not aware of any cases in humans where there is specific damage to just that nucleus."
] |
[
"If I had two texts from the same language written hundreds of years apart, could linguists tell which one was written earlier?"
] |
[
false
] |
Assuming that you can't tell from the subject material being discussed.
|
[
"So let's assume we've never encountered this language before, but have a good idea of how it is pronounced, a good idea of how the grammar works, and a good idea of what everything means (because otherwise, this sort of thing gets next to impossible).",
"First of all, languages change, and over time these incremental, evolutionary changes will stack up. However, it is an empirical fact that languages do not change at a fixed rate (Blust 2000). Nothing like a strict ",
"molecular clock",
" exists in linguistics, and the rate and pace of language change is not very well explored. It is certainly the case that varieties separated far in time from one another will almost certainly look different, but just how different will vary from case to case.",
"That being said, there are some clues that can help us out. Languages tend to evolve down certain pathways. Often, this is simply a result of the physical structures involved with producing language. For instance, speech sounds can be rated on what is called the ",
"sonority hierarchy",
". This measures the relative amplitude (which is perceived as the relative loudness) of sounds. The least sonorous sounds are ",
"voiceless",
" ",
"stops",
" (sounds made by completely blocking the airflow, which also do not co-occur with vibration of the vocal folds), while the most sonorous sounds are vowels. Other sorts of speech sounds fall somewhere between these on a continuum. For a variety of reasons based both in production (what speakers do) and perception (what listeners do)--mainly to do with the complexity of timing the gestures needed to produce speech, the effort needed to produce some gestures versus others, and the ability to discern one sound from another, we tend to see certain patterns over time. ",
"For instance, it is harder to stop voicing (the vibration of one's vocal folds) than to maintain it. So often, languages will have processes where sounds that are otherwise voiceless become voiced between other voiced sounds. A classic example of this is found in the transition from Latin to modern Spanish: Latin ",
" 'wolf' > Spanish ",
" 'wolf' (intervocalic voiceless ",
" > voiced ",
"), Latin ",
" 'life' > Spanish ",
" 'life' (voiceless ",
" > voiced ",
"), Latin ",
" 'hearth' > Spanish ",
" 'fire' (voiceless ",
" > voiced ",
"), and so on.",
"Sounds are not the only area we could look at. We could also possibly find hints in the grammar of a language, though these are much harder to come by. There are a variety of processes that get lumped together under the heading of ",
"grammaticalization",
". These refer to the processes by which a lexical word (something like an ordinary noun or a verb) becomes a grammatical word (like an article), or even something like a prefix or a suffix. For instance, the words ",
" and ",
" in modern English, the indefinite articles, originate from the same word as modern English ",
". Certainly in Old English you find the same word ",
" being used for both meanings (both 'one' and 'a/an'). The process of ONE > INDEFINITE ARTICLE is well attested in the world's languages, and thus, if we saw one sample that only had a word for ",
", and another that had a word for ",
" and ",
", we would then have grounds to try and claim that one is relatively older than the other.",
"So there will be little clues here and there. Linguists probably would be able to draw some conclusions, but it very well may not be strikingly obvious at first. To use a particularly mean example, Old Japanese was recorded through the 800s CE. The term for ",
"Tanabata",
" a traditional festival held on the 7th day of the 7th lunar month, is fairly similar despite over 1,000 years of divergence. In Old Japanese, it would be pronounced [ta.na.",
"ba.ta], while in modern Japanese, it would be pronounced [ta.na.ba.ta]. Essentially the only difference is that Old Japanese had a ",
"pre-nasalized",
" ",
" where modern Japanese has just a voiced ",
". That being said, Old Japanese as a whole looks quite different than modern Japanese. Additionally, while we can say a lot about relative timing (",
" happened before ",
"), absolute timing (",
" happened ",
" years before ",
") is much more difficult."
] |
[
"duuuuuuuuuuuuude. this was fascinating; thanks for the detailed response!"
] |
[
"See: Shakespeare. It is definitely written before Harry Potter. It's easy for even the laymen to tell the difference between our current language and an earlier version of our language.",
"It is easy because there are clues other than the language itself that we have access to as members of the culture that produced Harry Potter, and the cultural legacy of the one that produced Shakespeare. While it is easy to tell that they are different, I don't think it is the case that a layperson could easily say, given a culture unfamiliar to them, that one is necessarily older than another.",
"Colors aren't ubiquitous in language. Different words for colors are invented at different times. So, if for example, something is described as \"blue\" (one of the almost universally last colors to be described in any language), then the linguist would know that this document is a newer document... in the scheme of things.",
"While it was originally proposed by ",
"Berlin and Kay (1991)",
" that color terms were evolutionary in how they occur, this has been challenged several times over (see, for instance, ",
"Levinson 2000",
"). Additionally, there is very little evidence of this evolution actually occurring in historically attested forms of a language, at least along the early developmental paths Berlin and Kay have proposed. For instance, we see original grue (a combination of what we label blue and green) gaining a companion of (bright) green in Japanese (青い ",
" 'grue' and later 緑 ",
" '(bright) green'), but not languages that have only white and black and later gain red."
] |
[
"Can you train/exercise your ears to hear better?"
] |
[
false
] |
A while ago I heard someone I work with, who is a fairly smart person, talking to another coworker. He said, “I watch TV with the volume on low to train my ears so I can hear better.” Would this work?
|
[
"Audiologist here.",
"You can't train your ears to hear better, but you can train your brain to hear better. A lot of \"listening\" really has to do with the brain and not the ear. The ears send the raw signals into the brain but it is the brain that makes sense of them, and that \"making sense\" can absolutely be trained. It doesn't affect your actual hearing though - ie. it won't turn up in a basic audiometric test.",
"Auditory-verbal_therapy",
" is what HA or CI users do to teach their brain how to listen/hear better using their devices.",
"Central Auditory Processing Disorder",
" is a disorder when the brain cannot process properly what the ears are hearing. There are treatments/therapies addressing CAPD where the aim is to train the brain to hear better. ",
"I've never heard of any of these therapies done by people with normal hearing in order to \"improve their hearing\"."
] |
[
"They are saying that you can't improve the mechanical function of your ears by \"exercising\" it the way you can your biceps.",
"You ",
" learn to interpret the crappy signals coming from your crappy ears more accurately though."
] |
[
"So, basically, you can practice and \"get better at\" listening skills, but you can't actually improve your hearing ability?"
] |
[
"How does delayed parenthood and fewer children cause cancer? [Medicine]"
] |
[
false
] |
In it states: The WHO's World Cancer Report 2014 said the major sources of preventable cancer included: ... Delayed parenthood, having fewer children and not breastfeeding I have never heard of that before and struggle to think of a plausible mechanism by which it could cause cancer. Presumably it only causes cancer in females and via some kind of hormonal mechanism but it's still surprising. Can anyone elaborate?
|
[
"But the article appears to imply the opposite. That delaying parenthood (e.g. via the use of oral contraceptive) will increase the probability of cancer, not decrease it?"
] |
[
"But the article appears to imply the opposite. That delaying parenthood (e.g. via the use of oral contraceptive) will increase the probability of cancer, not decrease it?"
] |
[
"This article",
" relates pregnancy to ovarian cancer. They find drastically reduced cancer rates in women who have had 1 or more full term pregnancies. While they don't investigate mechanisms, the one they propose makes sense. Pregnancy inhibits ovulation which is basically cellular growth and proliferation in the ovaries. Decreased cellular activity could logically lead to decreased cancer in the affected tissues. They don't find a link with breast feeding and ovarian cancer, but I assume the mechanisms would be similar with respect to breast cancer."
] |
[
"How do we know the rate at which stars are orbiting a galaxy's center?"
] |
[
false
] |
This question is prompted by the math-dark-matter article in the science subreddit: I imagine galaxies are rotating incredibly slowly and because they are so far away and tiny to our eyes, noting the distance a star has moved must be pretty damn difficult. So what method do we use to accurately tell the orbital period of stars in a galaxy?
|
[
"Redshift.",
"On average we can say that the the stars are all moving in approximately a circle, and they are all pretty much going around in the same direction. That means that if you look at a galaxy, one half of the galaxy is moving away from you, and the other half is moving towards you, depending on which way the galaxy is spinning.",
"You are right that they are moving so slowly that we cannot tell how fast it is moving from side to side, but when something is moving towards us the light it emits gets squashed (shorter wavelength) and becomes bluer and when something is moving away from us, the light gets stretched, and becomes redder.",
"We can use that to figure out how fast the stars are moving."
] |
[
"I figured it was a method similar to this, but, is this method accurate enough to distinguish between stars set at different radii? "
] |
[
"Surprisingly yes, the resolution of the rotation curves is quite impressive."
] |
[
"Using laboratory glassware, what would be the \"best\" way to brew coffee?"
] |
[
false
] | null |
[
"CAUTION: Coffee should NOT be brewed in a lab, you could very easily poison yourself even if you are very careful."
] |
[
"What do you mean by \"best\"? That's not a scientifically useful criteria. Cheapest? Fastest? Simpliest/Most eloquent/Hardest for an undergrad to screw up?",
"Even the ",
"National Coffee Association",
" can't really answer that question because \"best\" is so subjective. Making coffee is effectively just running boiling water across coffee grounds. However, you have a lot of controls: variety of coffee, degree of the grind, brewing process, etc. Whether you create a drip apparatus, a percolator, or siphon brew it, it'll all come out different based on many different variables. And your palate and preferences will differ from someone else's. But perhaps this pdf from ",
"Prima Coffee",
" addressing the siphon brewing of coffee will be more helpful."
] |
[
"Using used lab equipment in an existing lab that isn't geared to coffee production, yes, but he says he wants to SET UP a \"coffee\" lab.",
"If he were to set up an aeropress with a clean vaccum manifold purchased online, and put that in his kitchen, away from any sodium azide or ethidium bromide, and call that a lab, the only danger of poisoning is if he enriches the caffine too much.",
"On topic, cold brewing is worth investigating. A french press ina refrigerator type setup, I've heard good things about that. Also google \"black blood fd the earth.\" A professor at Berkley (i think) sells a special extract that has 40x the caffiene and none of the bitterness of coffee. No idea how."
] |
[
"I have a sheet of plastic-like material that is claimed to be polyetherimide. I suspect it may be polycarbonate. How can I check?"
] |
[
false
] |
I recently bought a sheet of material that was claimed to be PEI. As people who are into 3D printing know, PEI (Polyetherimide) is renowned for its qualities as a build surface (namely, it helps prints adhere extremely easily). I bought a smaller sheet of PEI before, from a different company, and that seems to adhere prints extremely well. This new sheet of "PEI", doesn't seem to hold prints well at . I'd like to try to test if this sheet is actually PEI (and if it is, I would hope not to entirely destroy it, but if it's PC instead, I'm fine with it being destroyed). Given the price paid, I suspect that it is a fake. I'm a hobbyist and thus don't believe I have access to an IR spectrometer, but if there are common ways to get access to one, I'd love to know. Alternatively, are there simpler ways of testing if it is PEI or not? My initial thoughts were melting tests or hardness tests or maybe some kind of chemical reaction, but I'm not sure what exactly to do. Thanks for your help! (P.S. I have removed all protective coverings, so that's not the issue.)
|
[
"Great idea! Did exactly this.",
"\"Good PEI\": No melting whatsoever. \n\"Known Polycarbonate\": Melted. \n\"Questionable PEI\": Melted. ",
"Went back and forth a few times, waiting in between. The questionable PEI, or should I now say, the polycarbonate, melted easily.",
"God, I'm pissed.",
"Thanks for the help!"
] |
[
"An easy low-tech solution: melt a small spot on it with a variable-temperature soldering iron, using a known sample of polycarbonate as a comparison. Polycarbonate should start to melt at about 150 C; PEI should stay solid past 200 C.",
"https://en.wikipedia.org/wiki/Polyetherimide",
"\n",
"https://en.wikipedia.org/wiki/Polycarbonate"
] |
[
"IR spectroscopy would be best, maybe you could ask some people at a local university if they could help you.",
"Maybe you could measure its density? PEI should be 1.27 g/cm3 while polycarbonate should be 1.22 g/cm3. However, you'll need a good way to precisely measure the mass and volume of your sheet.",
"You could also try reacting it with concentrated strong base (such as NaOH, be careful!). This should destroy polycarbonate but PEI will be pretty resistant."
] |
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