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[
"How important is the way that we breathe?"
] |
[
false
] |
[deleted]
|
[
"What do you mean? Chest vs abdominal breathing or nose vs mouth breathing. ",
"For breastfeeding children, they are primarily nasal breathers, and are able to both suckle and feed and breathe at the same time. Because their nasal airway and oral esophageal pathway are closed off from one another. This however makes them way more vulnerable to compromising their airway, since there’s no alternative. ",
"As you grow up that pathway opens up, and you can breathe from your mouth. ",
"Children <10 tend to be abdominal breathers. Doesn’t really mean anything but they breathe by expanding their abdomen instead of their chest. ",
"Adults can do either abdominal or chest breathing. And can also do mouth or nasal breathing. But cannot both drink or eat and breathe at the same time like a baby can."
] |
[
"Physical therapist here.",
"It’s true that adults tend to become chest breathers, and many become neck breathers (using their neck muscles to help the lungs expand. ",
"Over time and disuse of the movement, many adult lose their ability to breathe diaphragmatically (abdominal breathing), which becomes a problem for other areas of the body. Neck pain, reduced lung capacity, and core and pelvic muscle weakness or dysfunction are some of the things can develop in people who exclusively neck/chest breathe. ",
"Taking time everyday to breathe deeply enough to engage the diaphragm and other abdominal muscles is important to good breathing throughout the lifespan."
] |
[
"Nope, that’ll pretty much always do the trick! ACSM guidelines suggest 30 minutes of moderate cardio (intense enough to make you breathe hard and sweat) 3-5 times a week, and that’s appropriate for most older adults as well. ",
"There is unfortunately a large segment of the adult population that doesn’t do that. Curse of the Western lifestyle - lots of sitting and not much else. Muscles atrophy when they’re not used enough, and so the diaphragm becomes weak, uncoordinated, and eventually ineffective. ",
"If you want to specifically practice diaphragmatic breathing: \n- sit or stand in front of a mirror. \n- Place one hand over your chest and the other on your belly. \n- As you breathe in deeply, your belly hand should move first. Inhale for about 4 seconds. \n- Your neck muscles should ",
" engage at all. \n- As you breathe out, your chest will deflate first, followed by your belly. Exhale for 6-8 seconds. \n- You should feel your belly muscles help squeeze the last of your air out of your lungs. ",
"This is also just a great exercise anytime you’re feeling stressed, can’t sleep, or are dealing with pain. There are videos of this technique on YouTube that you can search for and follow along with. Happy breathing!"
] |
[
"If somebody across from me on a large field shot a gun while holding a walkie talkie with the speak button on, would you hear the sound first on the walkie talkie or from the sound itself?"
] |
[
false
] | null |
[
"Walkie-talkies use radio frequency electromagnetic waves to transmit signals. These propagate with the speed of light, approximately 300,000 km/s. On the other hand, sound from the gunshot (or any other sound) will travel at about 340 m/s (precise value depends on atmospheric conditions).",
"For all intents and purposes you can consider the time it takes for a walkie-talkie signal to travel from one walkie-talkie to the other to be zero. With that, you see that if the gun is shot 340 meters away, the sound will be heard on the walkie-talkie on second earlier than directly through the air.",
"(note: I'm also assuming that there is zero processing delay in the electronics of the walkie-talkie. I don't know the engineering details of these things, but I expect that this is a reasonable assumption and that these delays are in the order of magnitude of miliseconds only)"
] |
[
"Incidentally, Admiral Grace Hopper ",
"had a fantastic 2-minute demonstration",
" that puts the speed of light into tangible terms. While it's convenient to discount the travel time of light as \"instantaneous\", in some situations (not this one, of course) it definitely makes a difference!"
] |
[
"For those of you who don't know who ",
"Grace Hopper",
" was:",
"EDIT: This summary doesn't even do her justice. There's just not that many people of her caliber."
] |
[
"Has anyone ever attempted a computer-based ecosystem?"
] |
[
false
] | null |
[
"This is more ground-up than what you're describing, but it is fascinating:",
"http://en.wikipedia.org/wiki/Conway%27s_Game_of_Life"
] |
[
"Ecologists have been developing very simplified models of ecosystems for a long time. The famous ",
"Lotka-Volterra",
" model of predator-prey interactions was developed in the 1920s, for example. Ever since, more and more complex models have been developed to understand more subtle ecological interactions. You can look at a much more recent example ",
"here",
"."
] |
[
"This is instantly what I thought of. However, Conways' game of life while showing some simple \"organisms\" is more or less mathematical physics (still falling short of the great complexity we see in biological systems). The big thing here is that the system of rules has emergence, self-organization and later it was shown self-replication. Another fun caveat is that it's Turing complete, so it's a computer in a computer!",
"I am very interested in finding a system like your asking about but I do not think the mathematics, the biology or the harmonization of the two is there yet. I can however suggested some good reading that alludes to all the complexity in finding said computer system (which ultimate outlines that new paradigms in computing will need to be invented):",
"Integral biomathics: A post-Newtonian view into the logos of bios"
] |
[
"Why is there dust on the moon?"
] |
[
false
] |
If there is no atmosphere how is there dust? The sand on earth is created by erosion from wind, sun and sea. How did the dust on the moon get there?
|
[
"It's formed by impacts - everything from large to micrometeorite events. These generate not only fine particles, but also rock vapour which then re-crystallises onto existing grains.",
"https://gsa.confex.com/gsa/2008AM/finalprogram/abstract_152612.htm"
] |
[
"Pulverized rock from meteor impacts most likely."
] |
[
"There's dust in space which makes its way to the moon. Also when ",
", stellar bodies, maybe a better word, of that type form, there's local dust that eventually gravitates toward the planet.",
"Related: Since there's no erosion on the moon, moon dust can be pretty shard-like. Comparatively, dust and dirt here is like polished river rocks. Moon dust can be a big problem for landing equipment and also space suits have to be designed to be very resistant to it."
] |
[
"[Medicine] How does limb reattachment work?"
] |
[
false
] |
I've seen examples of limb reattachment on TV, from fingers to hands to legs. But how does this process work? How is it possible for a body part to be completely cut off, yet still be able to function again if attached properly? (I know this is probably insanely complicated, but a simple-ish answer would satisfy my curiosity) Bonus: Is there a special title for a surgeon who does this?
|
[
"This is known as ",
"replantation",
". ",
"For digit and hand replants, you basically repair and reattach the bones, then tendons (to provide support for other soft tissue structures), followed by connecting the arteries, veins, and nerves via very delicate suturing. ",
" ",
"In the majority of amputations, the sequence in replantation procedure is as follows: bone shortening and stabilization, extensor and flexor tendon repair, arterial anastomoses, venous anastomoses, nerve coaptation, and skin coverage.",
"The outcome and degree of impairment is determined by factors such as the type of injury (clean cuts are good, crush injuries are bad), duration of ischemia before replantation, age (younger = better), and smoking, alcohol, or other factors that affect the blood vessels (atherosclerosis, diabetes, etc).",
"The surgery is likely performed by a ",
"microsurgeon",
". "
] |
[
"And then the body's natural healing processes take over? ",
"If so, what conditions are necessary to trigger the body's natural response? Like, does tissue need to be within a certain distance, or touching, or connected via fluids, etc? Also, do we ever see cancerous and other abnormal growths during the healing process? Or, is it inevitable that the \"proper\" thing grows to other end?"
] |
[
"There is one thing I never understood that I'm reminded of reading this thread.",
"When somebody breaks their neck and severs their spinal column, we're currently (as far as I'm aware) unable to repair the severed nerves, leaving the person a quadraplegic, yet when a hand or finger is severed it can be reattached and feeling and function in the limb can be almost completely restored. ",
"Why is this, and why can't we restore a spinal column in the same way we restore the nerves in a severed limb? Is it just that the spinal column is that much more complex, or are the nerves different, or does our body react differently to this type of damage?"
] |
[
"Can I use my phone camera to look at the eclipse?"
] |
[
false
] |
Ok. I know you aren't supposed to look at the sun directly (duh). But during the eclipse, suppose I put my phone up so it blocks the sun fully and record a video.. That would be safe, wouldn't it since I'm not looking at the sun per say, but my screen showing the sun... Right? I just want to make sure I can do this before I try it. :)
|
[
"It's safe for you, and most digital image sensors are pretty well protected. If you're taking short exposures (<1 second) both you and the camera should be fine, just don't spend a lot of time lining up your shot."
] |
[
"Well, that's what I mean.. I'm not talking about taking a quick shot.. I'm talking about taking my cell phone, covering up the sun and starting a video recording for the whole eclipse.",
"I would be viewing it in real time ala iron man heads up display.",
"Would this mess up the cell phone camera or my eyes doing such? The sun would be fully covered by my cell phone."
] |
[
"Your eyes no, but to find out the potential long term damage to your cell phone you'd have to get the specs from your manufacturer. It will vary by sensor. However, you could do a simple old trick - if you can find any old film negatives (uncommon these days) or a couple of pieces of neutral density filter and put it over the camera lens, it would reduce the incoming light to a much safer level. ",
"To be honest, the eclipse only runs a few minutes and most current image sensors are pretty tolerant. If you're out of warranty and like your camera phone, try the filtering trick.",
"Oh and despite the media ZOMG IF YOU LOOK AT THE SUN YOUR EYES BURST INTO FLAME, quick looks at the sun don't damage anything. The danger with eclipses is that the overall light is greatly reduced and so you can be tempted to stare into it too long. UV-based retinal damage is permanent."
] |
[
"Are there any negative health effects from consistently going to bed around 5am and waking up at 2pm?"
] |
[
false
] | null |
[
"Yes, though I doubt it's permanent. Virtually every process in your body - metabolism, immune response, tissue regeneration you name it - is tied to the circadian rhythm, a 24 hour cycle maintained by a proteinaceous clock within each cell. ",
"The clock is synchronized by a group of light sensitive neurons, so it is attuned to daylight and when you keep a 5am-2pm sleep schedule you are awake while your body performs functions normally reserved for sleep. "
] |
[
"There is a tremendous host of problems associated with shift work. If you want more information, I would recommend googling \"harvard nurses study night shift work.\" (But there's more available than just through the harvard nurses study.)",
"That may or may not be relevant to your situation. Somebody voluntarily nocturnal is probably not vulnerable to exactly the same problems as somebody who has to work at night, and may or may not be sleeping adequately in the daytime.",
"Unfortunately, looking at shift work is probably your best way of figuring out if it's bad to sleep during the day and stay awake all night, because an interventional trial wouldn't be any better of a comparison for you, and because there's pretty much no academic interest in whether people that voluntarily sleep in the day are hurting themselves :)"
] |
[
"Oh hell yes. Some examples effects, interfering with your liver's night janitor job that happens between 3-5 AM and which gets your blood cleaned up for the next day. Result dirtier blood during your awake time which leads to less concentration, greater irritability, poorer digestion, and therefore poorer quality tissue synthesis. IE. you will make poorer quality you that's more prone to inflammation. If you have any inflammatory diseases, expect them to be worse. If you have immunity problems, expect them to be worse. If you are in a program that demands this sort of schedule from you, consider switching to something more humane. Take a look at the studies on Night Shift workers, they have nothing good to say about the practice. "
] |
[
"Why do so many medicines make you higher risk for TB infection?"
] |
[
false
] |
Seems like every commercial for medication lately warns of higher TB infection rate and to tell your doctor if you've been anywhere outside the US lately?
|
[
"Generally those medications suppress your immune system as part of the way that they treat the symptom for which they are prescribed. Autoimmune diseases like rheumatoid arthritis, psoriasis, and Celiac disease are due to your immune system reacting to your own body. To treat this, the medications suppress a part of your immune system. ",
"The part about travel outside the US is because TB is much more prevalent in certain countries. You could acquire a latent TB infection (be infected but not show symptoms) but if you begin taking a medication that suppresses your immune system it is possible that you can develop an active disease state. ",
"If you have travelled your doctor would want to know where & when and you may need a TB test prior to beginning treatment with one of these medications."
] |
[
"To expand on this, TB typically forms granulomas in the lungs which is the best way our immune systems can deal with TB. Throw as many cells as soon possible until it's covered in so many layers that the TB cells can't interact with anything. ",
"It's difficult to say if this is how our immune system has evolved to deal with TB or TB has evolved to modulate our immune system to survive but ultimately when there's a breakdown of immune function then TB has open reign. It's quite common for children to get TB from grandparents for this reason."
] |
[
"Autoimmune diseases like rheumatoid arthritis, psoriasis, and Celiac disease are due to your immune system reacting to your own body.",
"Just a small correction: They react to an offender/allergen.",
"In some cases the trigger is known like in Celiac or little understood like in the others."
] |
[
"Why does sound travel faster in less dense gas like helium but slower in denser gas like argon?"
] |
[
false
] | null |
[
"Because the molecules are lighter. Imagine a long train with many wagons connected by springs. If you move the first one a bit you should have enough intuition to believe that this will start a wave of motion of the wagons down the length of the train. If the wagons are heavily loaded the springs will be contracted quite a lot before the motion stops and the next wagon gets up to speed due to inertia. If the wagons are unloaded they will faster respond to the motion.",
"This is the same for gas molecules - even an ideal gas where the molecules do strictly speaking not interact. One can work out the details and ",
"one finds",
" that the speed of sound in an ideal gas is given by",
"v = sqrt(γkT/m)",
"where γ is a constant that depends on the degrees of freedom of the gas molecules, k is Boltzmanns constant, T is the temperature in Kelvin and m is the mass of the molecules. So you see that the speed of sound is inversely proportional to the square root of the mass -> lighter mass = higher speed of sound."
] |
[
"So why would sound traveler faster in solids and liquids water? Sound travels much faster and further in water and steel than in gas."
] |
[
"Basically, the molecules in a solid or liquid \"feel each other\" more than molecules in a gas, so their stiffness is higher, increasing the speed of sound. It is important, though, not to confuse this with density. Just as in gases, a solid with the same stiffness but higher density will have a slower speed of sound."
] |
[
"What is mainly heating the earth? The sun or the core?"
] |
[
false
] |
I learned that Saturn at the North Pole is about 30ish degrees while near the equator it is way colder than from the poles. Since saturan is way father from the sun than it is from earth, does earth gets most of its heat from its core or from the sun?
|
[
"Depends. The inside of the Earth gets almost all its heat from the Earth itself. Not just the core.",
"Almost any temperature on the surface of the Earth will be dominated by the sun's influence far, far more than the internal temperature (unless you are standing over something volcanic).",
"The sun's heating penetrates only a relatively short distance into the planet, so it quickly becomes dominated by internal heat."
] |
[
"Yeah, heat generated within the Earth eventually reaches the surface and radiates away. Mostly it is just retained within. The sun's energy input vastly outmatches what the Earth produces (surface area doesn't make a huge difference) but it radiates away very quickly.",
"Basically, Earth is capable of radiating away a great deal of energy into space via blackbody radiation. The inside of Earth retains its heat because it is insolated from space. But any reasonable amount of energy input to the surface will radiate away easily since it lacks that insolation. This includes both solar radiation as well as internal energy that reaches the surface."
] |
[
"I assume you mean heating the Earth's surface, so I'll answer that. ",
"This paper from 2010",
" says that the heat flux at the surface of the earth due to internal heat is 47±2 terawatts (TW) or about 47 trillion watts. That sounds like quite a bit but now let's look at what's coming from the sun. ",
"NASA",
" says that the sun provides 340 W/m",
" of energy to the earth's surface. When you multiply that by the surface area of the earth you get ",
"173400",
" TW. So the internal heat of the earth contributes about 0.027% to the earth's total heat budget at the surface",
" "
] |
[
"If you burn radioactive paper does it change the radioactivity?"
] |
[
false
] |
Well... I think my title says it all. Thanks.
|
[
"Not typically. Radioactivity is usually a much more a property of just the nuclei of the atoms in the material, so is not substantially effected by chemistry like burning, which is the effect from the electrons orbiting the atom.",
"There is, however a small change in decay rate for those atoms which undergo decay by ",
"electron capture",
", because the electrons directly participate in the decay. Chemistry will change the distribution of electrons in the atom, hence the effect. This effect would be bigger if you ionized the atom, removing electrons which could participate and slowing down the reaction."
] |
[
"I saw the thread about the Curie notes still being radioactive and it got me thinking. Thanks for the info. "
] |
[
"Her papers are contaminated with Radium-226, which decays via ",
"alpha emission",
", which should be almost perfectly independent of chemistry."
] |
[
"Can you short out power lines using Mylar balloons?"
] |
[
false
] |
This question was prompted from . A character releases a bunch of Mylar balloons which make contact w/ a power line, creating huge sparks and disrupting power to a nearby building. Mythbusters of reddit, please tell me: Could that work in real life or is this just some TV magic?
|
[
"Let's clear up a basic misunderstanding: Mylar is Dupont's term trademark for biaxially oriented PET film. It is a very clear film that you can see through. It can be used as is, or it can be printed on and/or metallized.",
"For some reason that I've yet to understand, people think that Mylar is only the metallized version of the film. The youtube video provided by kenks88 for example, fails to make this distinction.",
"So to read your question literally, the answer is no. Plain PET film will not short out a power line. I am quite surprised that a metallized Mylar film will short our a power line as the vapor coat is exceedingly thin - you would think it would act like a fuse - melt and breakdown before any serious damage could be done, but apparently that is not the case."
] |
[
"Yes",
"http://www.youtube.com/watch?v=XPqL6alKALQ"
] |
[
"Thanks!"
] |
[
"Is it in the foreseeable future that we will be swallowed by a black hole?"
] |
[
false
] |
After reading an article by iO9 ( ), which talked about the two largest black holes ever found, I started to wonder this. Would we all be killed somehow by something sooner? Would the black hole be from our galaxy or another one, and how would it get here?
|
[
"Standard post:\nBlack holes are not cosmic vacuum cleaners. If my laptop suddenly turned into a black hole now I would not be sucked into it.\nIt would still exert the same gravitational force on me as it is at the moment."
] |
[
"As long as you don't try to type on it, right? If you put a part of yourself inside the event horizon, then you'd be goners?"
] |
[
"because of the small mass of his laptop he would have to get very close to the event horizon to feel the extreme gravitational pull. Obviously the event horizon itself would be so tiny, it wouldn't be directly observable (actually it isn't either way, ha-ha), because it is directly related to the mass of the black hole. ",
"This also tells us that the area where the gravitational pull is very high is also very small, since the area where light cannot escape the pull is very small. Based on this observation he should be able to put the hole right through his hand and not even feel much."
] |
[
"Is there a difference between having a 2 hour nap then 6 hours sleep and just having an 8 hour sleep? Brain wise?"
] |
[
false
] |
So what usually happens to me is that I arrive home from school, and usually have a two hour nap. Lets say from 5pm - 7pm. Then I stay up until 12am and wake up at 6am. Is there a difference if I stay up until 10pm and sleep till 6am? Does anything happen in brain function?
|
[
"This study",
" found that there is no difference between 8/0 and 6/2 schedules in terms of cognitive performance. They tested different combinations of nighttime sleep opportunities (ranging 4.2-8.2 h) and afternoon nap opportunities (ranging 0-2.4 h). Performance had a near-linear dependence on the ",
" (day+night) sleep duration, regardless of how it was divided.",
"Sleep content may of course be quite different when sleep is divided up into multiple blocks, because sleep is normally composed of cycles between non-REM and REM sleep. These cycles may be interrupted, although it's not clear whether this has any effects on sleep function. We frankly don't yet fully understand the functional relevance of the NREM/REM cycle.",
"The main practical concern with a long daytime nap is that there is reduced sleep pressure when attempting to initiate sleep at night. For some individuals, this can contribute to insomnia, especially if it is combined with other factors that contribute to insomnia. One such example is excessive use of artificial light sources leading up to bed. Light exposure at this time of day delays the circadian clock's rhythm, meaning the (already weakened) signal to go to sleep can end up pushed far back into the night."
] |
[
"Probably not without problems, for two reasons. First, there are times of day at which it is very difficult to initiate sleep and maintain consolidated sleep. Schedules that involve trying to sleep outside of the biological night or afternoon siesta time are therefore a struggle. Second, this is going to really disturb structure, and may therefore alter the amount of time spent in the deeper stages of sleep.",
"Both of these problems arise with \"polyphasic\" sleep schedules. In addition, many polyphasic schedules also try to drastically shorten total daily sleep far below eight hours, which is also a bad idea."
] |
[
"Could you then have four 2-hour naps throughout the day and never have to \"go to sleep\" in the traditional, continuous sense?"
] |
[
"How can organisms that reproduce asexually evolve, if at all?"
] |
[
false
] |
[deleted]
|
[
"Asexually reproducing organisms show much less variation in DNA as compared to sexually reproducing organisms.\nHowever, when an asexually reproducing organism like a bacterial cell is about to divide, it needs to replicate its DNA. This DNA replication is not always perfect, and errors can be introduced. Thus, the daughter cells don't have the EXACT same DNA as the parent cell. Over time and successive generations, these errors accumulate such that the progeny or daughter cells have substantially different DNA as compared to the original parent.\nThis gives rise to subtle variation, and if evolutionary selection pressure exists, eventually leads to evolution."
] |
[
"Asexually reproducing organisms show much less variation in DNA as compared to sexually reproducing organisms.",
"I'd say that it's the mixing/matching of sexual reproduction that allows more combinations to be tried, not the rate of mutation."
] |
[
"I agree. I meant that the high variation observed in progeny of sexually reproducing organisms is a result of recombination instead of mutation"
] |
[
"If the distance between water jets increases the further away I am from the shower head, why aren't there perceptible gaps in light being emitted from very distant stars?"
] |
[
false
] | null |
[
"There actually are gaps in the light emitted by distant stars, however, this is perceived by us as a change in the light intensity. When we see a star, we are seeing the photons emitted by that star. The farther you get from the star, the less photons impact your eye and the less intense the light becomes. In fact, the intensity of the light from a point source, which we can assume a star to be at interstellar distances, will fall by the square of the distance. So:",
"I = Is * r^2\n",
"Now, why don't we see the spaces between photons as \"gaps\"? Well, even when the photons from a star get to your eye there are still a very large number of them. If there weren't, you wouldn't be able to even see the star because the intensity of the light would be below the minimum intensity that you can see. Additionally, unlike your shower head, there are no specific points where photons are produced."
] |
[
"Just for fun, I looked up the number of photons emitted from a 60 watt light bulb. I didn't do the math on this, but it looks pretty good. ",
"Source: Bucknell's Astronomy 101 page",
" A 60-watt light bulb emits 60 joules/sec of energy ( 1 Joule/sec == 1 watt). Pretend for a moment that all of this energy is emitted in the form of photons with wavelength of 600 nm (this isn't true, of course -- as a blackbody, a light bulb emits photons of a wide range in wavelengths). Calculate how many photons per second are emitted by such a light bulb.",
" This problem asks you to calculate how many photons per second are emitted from a 60-watt lightbulb. Since 60 watts is 60 Joules per second, we know that we need enough photons to carry 60 Joules of energy each second.",
"So how much energy does one 600nm photon carry? We'll need to use the relation between energy and wavelength",
"Ephoton = h c / lambda\n= (6.63 x 10^-34 J s) x (3.00 x 10^8 m/s)/ 600 x 10^-9 m\n= 3.32 x 10^-19 J \n",
"OK, so how many of these photons will we need to make 60 Joules? Let's assume we need some number N of them. Then,",
"60 Joules = N x 3.32 x 10^-19 J \n",
"and",
"N = 60 J / 3.32 x 10^-19 J\n= 1.8 x 10^^20 \n",
"So, in order to emit 60 Joules per second, the lightbulb must emit 1.8 x 10",
" photons per second. (that's 180,000,000,000,000,000,000 photons per second!)"
] |
[
"Thank you for your answer!",
"I'm trying to imagine the sheer number of photons that would need to be emitted from a star to still provide a somewhat steady \"shower\" of photos at such a great distance. It seems impossibly large."
] |
[
"How much thinner is the air at cloud level?"
] |
[
false
] |
In a percentage, if possible. :) Oh, and I guess I'm talking about normal day time clouds, whatever altitude those reside at.
|
[
"There are lots of clouds visible during the day, and they occupy a range of heights. If you want to calculate air pressure at a given altitude, you can use this formula:",
"P=(1 atm)*(1 - (height in km)/(44.3 km))",
"So, plugging that in for a few common cloud types:",
"Stratus clouds",
" are the uniform, boring clouds that cover the whole sky on an overcast day. They are also pretty low (less than 2 km) so pressure ranges from 1 to 0.78 atm.",
"Cumulus clouds",
" are the big fluffy clouds you see on a pleasant day. They are also pretty low (1 km) so they exist at around 0.89 atm.",
"Cumulonimbus clouds",
" are your typical tall thunderstorm clouds. They can get very tall and typically range from a few hundred meters to about 6 km, meaning it spans a pressure of around 1 to 0.46 atm.",
"Altocumulus clouds",
" start higher (2 km) but also top off at about 6 km. They look like uniform small puffs. Pressures range from 0.78 to 0.46 atm.",
"Noctilucent clouds",
" are less common but are off the charts in altitide (the formula above breaks down at these heights). Around 80 km high, they are made of ice crystals and are at less than 0.1 atm."
] |
[
"Your average fair-weather cloud is a cumulus cloud. Cumulus clouds are usually below about 1000m. The standard atmosphere tells us that the density of the air 1000 m above you is about 85% to 90% of the density of the air where you are (the ratio gets closer to 90% as your starting altitude gets lower, and closer to 85% as it gets higher)."
] |
[
"Thanks, and extra thanks for giving me more cloud types. I had no idea the atmosphere 'dropped off' that fast."
] |
[
"How do microscopic black holes behave?"
] |
[
false
] |
When I say microscopic, I mean black holes that are small enough that they behave like quantum mechanical particles. What would such a black hole's wave function look like? Could you model their behavior as a field theory where the black holes are the excitations? Does such a theory shed light on quantum gravity?
|
[
"In a sense, microscopical black-holes are just like very weird scattering-matrices. They form and immediately decay into many soft quanta, so they just act as scattering amplitudes for quantum processes. ",
"The only way we can ever observe micro black holes in experiments is if we have additional dimensions. In this case, the Planck mass is actually lower than what we expect and thus colliding experiments might have enough energy to produce black-holes. But these black-holes will come in something that we can Kaluza-Klein towers, which is a phenomena that happens in higher dimensional scenarios where different levels of excitation in the other dimensions are seen here as \"particles with different masses\", loosely speaking. ",
"Unfortunately, even if we have black-hole formation, it's quite unlikely that we'll actually be know, as we need to see more than one excitation to tell the difference between a black-hole or a resonance caused by any other particle. ",
"If you're curious, you might want to read this paper: ",
"http://arxiv.org/pdf/1006.2466",
" It's quite accessible and it talks extensively about the phenomenology of black-hole production. "
] |
[
"That was an asteroid, not a blackhole, I believe."
] |
[
"Not even a little..."
] |
[
"Why was such a massive, fundamental particle like the Higgs Boson so hard to find?"
] |
[
false
] |
I mean, it seems kind of obvious for something tiny like the neutrino to have been difficult, because it's so tiny and barely interacts with anything. But the Higgs, as I've heard described, is both massive... Like, much heavier than a proton or neutron, and also has to interact with all matter for it to have any mass at all. What's the issue? Also, same question for gravitons I guess.
|
[
"Having a large mass doesn't make things ",
" to study, it makes them ",
" to study. The Higgs boson is not stable; it decays with a lifetime around 10",
" seconds. So you can't find Higgs bosons in nature, if you want to study them, you need to produce them using a collider.",
"The more mass your particle of interest has, the more energy you need to give to your colliding particles."
] |
[
"Then the question would be, how can something described as so short living interact with all of matter to give everything mass?",
"The Higgs boson itself doesn't give particles mass. It's interactions with the Higgs field which gives particles some of their masses. So even though all of \"normal matter\" interacts with the Higgs field in some manner, it doesn't mean that it should be easy to produce Higgs bosons.",
"Doesn't that energy have to decay into something else that can be detected?",
"Yes. That's exactly how Higgs bosons ",
" detected in experiments.",
"Same with gravitons. If gravitons are the particle of gravity, and gravity is affecting everything, how can it be both interacting with everything and be so short lived they can't be found?",
"Gravitons haven't been discovered (assuming they exist) because gravitational interactions are ",
" weak on energy scales that we can probe in experiments."
] |
[
"The Higgs ",
" gives particles their mass. The Higgs boson is an perturbation in that field (any particle is a perturbation of its respective field)."
] |
[
"What is stopping people from broadcasting at frequencies of radio stations?"
] |
[
false
] | null |
[
"Well that is regulated by the FCC. They will actually drive around and look for illegal broadcasts at different frequencies. I know because where I work we have some older wireless microphones that broadcast at the frequency of 3g radio towers. If they were to find us broadcasting they would find us and fine us. It would also be expensive to broadcast at the level of a radio station."
] |
[
"The FCC. If you set up your own radio station without a license, it's not hard to find you - just follow your radio signal!",
"But there have been ",
"pirate radio stations",
" in the past, and there ",
"might be some now",
". The UK is a good place for it, since England is a small island, and you can set up your radio on a boat and leave when it gets hot.",
"Meanwhile, feel free to ",
"set up your own",
"! Or at least, feel free until you get caught."
] |
[
"So let's say someone started broadcasting at the frequency of some other big radio station. Would it be possible to \"over take\" the waves of the other station, or would they just merge and create static in car radios?"
] |
[
"How can the Universe be infinite if it \"started\" at a certain time?"
] |
[
false
] |
I understand that the universe is expanding extremely rapidly, but nothing can expand in an infinite manner.
|
[
"If the universe was infinite at its start then there's no problem with it still being infinite. It's just less dense."
] |
[
"So the Universe did not start as an infinitesimally small point?",
"yes, it did.",
"No, it didn't. The Universe was infinite to begin with, however infinitely dense and hot as well. "
] |
[
"We don't ",
" how it started. It could quite possibly have been a single point at time t = 0 and then been infinite for all times t > 0."
] |
[
"Hurricane Patricia Megathread"
] |
[
false
] |
Come here to ask all of your questions regarding "the strongest hurricane ever known to assault the Western Hemisphere" : Hurricane Patricia Strikes Mexico With 165 M.P.H. Winds : How Hurricane Patricia Quickly Became a Monster Storm
|
[
"[In an ideal world,] how much harvestable energy is in Hurricane Patricia?"
] |
[
"NOAA actually addresses the question of Hurricane energies in ",
"one of their FAQs",
":",
"Subject: D7) How much energy does a hurricane release?\nContributed by Chris Landsea (NHC)",
"Hurricanes can be thought of, to a first approximation, as a heat engine; obtaining its heat input from the warm, humid air over the tropical ocean, and releasing this heat through the condensation of water vapor into water droplets in deep thunderstorms of the eyewall and rainbands, then giving off a cold exhaust in the upper levels of the troposphere (~12 km/8 mi up).",
"One can look at the energetics of a hurricane in two ways:",
"the total amount of energy released by the condensation of water droplets or ...",
"the amount of kinetic energy generated to maintain the strong swirling winds of the hurricane (Emanuel 1999).",
"It turns out that the vast majority of the heat released in the condensation process is used to cause rising motions in the thunderstorms and only a small portion drives the storm's horizontal winds.",
"Method 1) - Total energy released through cloud/rain formation:",
"An average hurricane produces 1.5 cm/day (0.6 inches/day) of rain inside a circle of radius 665 km (360 n.mi) (Gray 1981). (More rain falls in the inner portion of hurricane around the eyewall, less in the outer rainbands.) Converting this to a volume of rain gives 2.1 x 10",
" cm",
" /day. A cubic cm of rain weighs 1 gm. Using the latent heat of condensation, this amount of rain produced gives\n5.2 x 10",
" Joules/day or \n6.0 x 10",
" Watts.",
"This is equivalent to 200 times the world-wide electrical generating capacity - an incredible amount of energy produced!",
"Method 2) - Total kinetic energy (wind energy) generated:",
"For a mature hurricane, the amount of kinetic energy generated is equal to that being dissipated due to friction. The dissipation rate per unit area is air density times the drag coefficient times the windspeed cubed (See Emanuel 1999 for details). One could either integrate a typical wind profile over a range of radii from the hurricane's center to the outer radius encompassing the storm, or assume an average windspeed for the inner core of the hurricane. Doing the latter and using 40 m/s (90 mph) winds on a scale of radius 60 km (40 n.mi.), one gets a wind dissipation rate (wind generation rate) of \n1.3 x 10",
" Joules/day or \n1.5 x 10",
" Watts.",
"This is equivalent to about half the world-wide electrical generating capacity - also an amazing amount of energy being produced!",
"Either method is an enormous amount energy being generated by hurricanes. However, one can see that the amount of energy released in a hurricane (by creating clouds/rain) that actually goes to maintaining the hurricane's spiraling winds is a huge ratio of 400 to 1."
] |
[
"If you mean \"what is the strongest possible hurricane\" (highest wind speed and lowest pressure), then Patricia is essentially it. Kerry Emmanuel, who is one of the most respected hurricane researchers, developed a \"",
"maximum potential intensity",
"\" index, which when applied to Earth's climate as it is now allows for hurricanes with winds up to around 100 m/s (220 mph), which is not much higher than Patricia's peak winds, which were likely greater than 200 mph.",
"There is some debate",
" as to whether increasing sea surface temperatures above their current value really will increase the maximum potential intensity of hurricanes. The general thought in the field (though there are many scientists that disagree) seems to be that increasing sea surface temperatures will not increase the maximum potential intensity by much...until you hit a certain point with ocean temperatures around 50C (120F), and you can potentially form a theoretical ",
"hypercane",
", with winds over 500 mph. Of course, this is ",
" warmer than you will ever find on Earth even in the most pessimistic global warming scenarios, so as far as we know they will remain hypothetical for the foreseeable future."
] |
[
"What do the “A’s” in batteries stand for?"
] |
[
false
] |
What does it mean and what is the function of having two AA’s vs having say 4 AAAA’s?
|
[
"The dry cell battery was invented in 1888, and by World War I there were lots of manufacturers making lots of different batteries, in different sizes, voltages, materials, etc. The US government came up with several of its own standards for describing batteries, in rapid succession.",
"Then in 1924, the manufacturers, government, and a few companies that used a lot of batteries got together and came up with a much simpler system that would outline a few standard sizes that everybody could agree on, with simple names. The smallest widely-used battery at the time got named \"A\", then in order of increasing size there was \"B\", \"C\", \"D\", all the way up to \"J\". (The popular 6-inch battery was called the \"6\" because that was already how everybody knew it.) The standards also included voltages and tests, so that battery users could be reasonably sure that an \"A\" battery from any manufacturer would be safe in a device designed to take one.",
"These naming conventions were picked up by an early engineering standards organization, the eventual predecessor of today's ANSI. As new battery sizes and voltages were introduced for new purposes, a succession of standards organizations have added new designations. And many of the old battery sizes are no longer widely used (or used at all...when was the last time you bought a \"J\" battery?)",
"The AA (two As because it's even smaller than the \"A\", but there's no letter before \"A\" in the alphabet) was added to the standard after WWII, as the smaller battery size had become popular during the war. AAA (even smaller than AA) was added in 1959, plus \"M\" and \"F\" designations were added for \"mercury\" and \"flat\" batteries (think hearing aid batteries). Standards continued to be updated and revised to encompass the dizzying array of different battery chemistries and shapes and sizes available...",
"...but the only thing more As mean is \"this one is smaller than a battery with less As\"."
] |
[
"Fun fact, pretty much every household in the US has a bunch of AAAA batteries, though most people don't know it. 9V batteries are simply 6 1.5V quadruple A batteries connected in series to give 9V.",
"http://www.rfcafe.com/references/electrical/aaaa-cells-inside-a-9volt-battery.htm"
] |
[
"Huh, I alwys thought 9v batteries were a stck of squat semi-rectangular cells."
] |
[
"Could someone explain what it takes to destroy organic molecules?"
] |
[
false
] |
Curious because of this article . Edit: What are the limiting factors of life originating from asteroids? What needs to happen, besides time and a "habitable" location, for life to not take hold in a solar system?
|
[
"Define \"destroy.\""
] |
[
"I'm not asking for a dictionary definition. I'm asking what ",
" mean by it.",
"You could mean \"completely annihilate,\" in which case my answer would be to use antimatter to \"destroy\" organic compounds. That really is the only way to \"annihilate\" matter.",
"Or if you mean \"reduce to useless fragments,\" in which case further verification is required - what is \"useless\" in your terms? What level of catabolism is required before something is considered \"useless\"? Something can be useless to us, yet useful to other living things.",
"That's why you need to elaborate on your question."
] |
[
"Do you know, offhand, at what temperature and pressure would CH bonds start to come apart?"
] |
[
"How to say certain complex chemical formulas?"
] |
[
false
] |
Hi there. Anyways, been doing some chemistry stuff and I've been thinking; how do you say some more complex chemical formulas? (especially stuff with parentheses/brackets) For example, the chemical formula for azurite, Cu3(CO3)2(OH)2. Thanks!
|
[
"Cu = copper\nCO",
" = carbonate\nOH = hydroxide",
"The parentheses group the items so you know that there are two carbonates and two hydroxides.",
"Azurite's chemical name is quite boring. Copper(II) Carbonate hydroxide. To see more on naming rules for inorganic compounds, start ",
"here"
] |
[
"You'd say \"azurite\" :) If I ",
" to say it, I'd read it as written (see-you-three-see-oh-three-two-oh-aych-two), but a better thing would be to say what that formula is describing; something like \"the unit cell of azurite has three coppers binding two carbonates and two hydroxides\". But drawing the thing is a ",
" more efficient way of communicating. In organic chemistry papers they'll often give the systematic name for some new compound once or twice but what you really pay attention to is the drawing of the thing, where they label it compound \"(a)\" or something and then just refer to it as that for the rest of the paper. ",
"Because however you do it, describing a complex chemical structure is words or systematic names is rather awkward compared to the visual. Which isn't really the same when it comes to describing any complicated 3-dimensional structure."
] |
[
"In grad school one of my profs said that the hardest part of writing articles for him and his students was naming any new compound. If they were lucky they'd find a named compound that had different functional groups to their's but otherwise the same connectivity and just replace where necessary.",
"And you're right, most people just use the structure than (a) or (1). "
] |
[
"Cause of flu/cold symptoms"
] |
[
false
] |
After recovering from the 24hr stomach flu, I had to wonder, what exactly causes the symptoms that I had. How does the attack of the virus in my body translate to body aches, nausea, headaches, etc, etc.? Likewise, how does the same work with cold symptoms? Whats the difference?
|
[
"A virus will infect and take over the cells of the body, it will then use the cells own machinery to replicate and spread. Usually this does not cause any symptoms but will become a larger problem if left unchecked. The immune system, when it kicks in and develops a response the the specific virus, will kill all infected cells and mop up free virus particles. It is this which causes the majority of the symptoms (like coughing, sneezing, vomiting, sores etc). What these systems are will vary depending on the virus, the site of the infection, what cells are affected etc. There is also something called the psychoneuroimmunological response, which is just a fancy way of saying the immune system talks to the nervous system. It will tell the host they are sick (so they don't do anything to make it worse), make them tired (so they rest and stay away from others), make them hot (this inhibits viral replication) etc. Generally most of the symptoms of a virus are related to the immune response. There are exceptions, viruses of the liver can affect the way the cells work which will reduce liver function to name one.",
"If you have a bacterial infection, this is completely different. Bacteria will invade and infect tissues causing local damage. The immune response will lead to local inflammation (redness, swelling, heat, pain). On top of this the bacteria may release toxins which can have any number of effects."
] |
[
"Vomiting and diarrhea are common symptoms of gastroenteritis, when this is caused by a virus this is called viral gastroenteritis. Usually in this case these symptoms are a result of damage and inflammation of the epithelial cells lining the gut/intestines by your immune system trying to remove the virus, or through viral killing of these cells. So these are not 'useful' in this context, they are simply a symptom of the viral infection and your immune system trying to remove the virus. Remember this is different from the effects of the psychoneuroimmunological response which are useful."
] |
[
"So then what about the vomiting and diarrhea? How is that reasoned to be a \"useful\" immune response? Are these side effects of a deeper response?"
] |
[
"Why when I wear flat shoes do my feet get sore? Shouldn't evolution of humans walking without shoes have shaped my feet to accommodate this?"
] |
[
false
] |
When I wear flats (or any shoes with virtually no support) after a long day my feet are sore, specifically the arch. Why would evolution from years of our ancestors wearing poor shoes or no shoes in the past not have fixed this to this day?
|
[
"Wearing flat shoes is not equivalent to wearing no shoes: flat shoes limit the ability of your foot to stretch and spring in comparison to an unshod state.",
"Also, we don't have a comparison of you in the same health using the same activity with a variety of different footwear conditions, including barefoot, so we don't really have a good dataset for comparison: it could be, for instance, that you are experience footpain that a person with a different lifestyle wouldn't experience regardless of footwear (for instance, you might be less accustomed to standing or walking for long periods of time.)"
] |
[
"That probability is for ",
" mutations. The probability is higher if selection favors the mutation. "
] |
[
"Why would evolution from years of our ancestors wearing poor shoes or no shoes in the past not have fixed this to this day?",
"We haven't hardly lived long enough or unifiably worn shoes for that to matter; evolution to the degree that you are talking about does not occur that rapidly."
] |
[
"Have we seen evidence of a fourth or higher spatial dimensional universe by looking at everyday natural objects in this, our three dimensional visible universe?"
] |
[
false
] |
[deleted]
|
[
"No, but you can read about attempts to do so ",
"here",
"."
] |
[
"A 4-d object would appear to be able to violate conservation of mass, or teleport, or be in 2 places at once. Let me give a 3d to 2d analogy. ",
"If you have people living in a 2d word, a sphere passing through it would appear as a circle that can grow to a max size, and then shrink back to nothing. A ring pushed through perpendicular to the page would look like 2 separate circles starting together, then moving apart and finally back together before it disappeared.",
"We've never observed anything like this."
] |
[
"I tried to write a system that treated entangled particles as bound through some sort of subspace in high school. When I showed it to a professor they pointed out that I added a ton of assumptions for no real benefit. You don't gain extra predictive power.",
"If we observed some sort of particle emitted from one entangled particle, then it disappears and reappears near the other, immediately prior to absorption, I'd say this might be evidence of hyperspace or maybe a 4d connection."
] |
[
"Is there an \"ideal length\" for a nap?"
] |
[
false
] | null |
[
"About 30 minutes, give or take 10. Its enough to send you into a stage 2/3 restful sleep, without plunging you into the deep stage 4 \"slow-wave\" sleep. That way you can wake quickly without being burdened by \"sleep inertia\", which is that groggy feeling you get after being woken from a deep sleep. A half-hour nap is enough to recharge memory function and brain activity, but it won't really give your body the physical rest it needs. If you want to take a longer nap, anything over an hour and a half is enough to go through deep sleep and wake without feeling sleep inertia, while also benefiting from some restful deep sleep."
] |
[
"So then...can I see your source on that?"
] |
[
"Then how do the polyphasic sleepers do it?"
] |
[
"A question about forces"
] |
[
false
] |
So forces are the exchange of gauge bosons. But where do quantum fields fit into this idea?
|
[
"In our present understanding, quantum fields are the fundamental concept. The existence of quantum fields leads to the existence of particles such as gauge bosons, as well as to other kinds of physical entities (e.g. bound states and extended field configurations like solitons)."
] |
[
"Gauge bosons are a means by which the field generated by one object is felt by another. To go beyond such a vague statement requires getting into the actual technical structure of quantum field theory."
] |
[
"My understanding is that interactions are essentially transmition of data across a field - what does this mean for gauge bosons?"
] |
[
"Where did early organisms get their energy if there were no other organisms to digest and no photosynthesis?"
] |
[
false
] |
In a closed system, life couldn't exist on earth because there would be no energy input. However, with the sun giving off energy, it's possible. Animals eat other animals which ate plants which used photosynthesis to get energy from the sun. But what happened before photosynthesis evolved? For even a single celled organism to divide, it needs energy. Absorbing another organism might make sense, but that organism would have needed to find energy as well. Aren't even nutrients full of potential chemical energy that had to come from somewhere?
|
[
"I'm not entirely sure of the evolutionary progress from single cell to photosynthesis and what was consumed in the meantime. However, there are organisms currently on the planet that do not photosynthesize or consume others. There are a number of different types of ",
"autotrophs that produce food through chemosynthesis",
". For example, there are ",
"species that can survive off the energy of the earth through hydrothermal vents (very far under water)",
".",
"Edit. For clarification: these organisms use highly volatile chemicals or some other abiotic energetic situation to their advantage. These things occurred naturally on the Earth, requiring no organism to create the nutrients but merely take advantage of the diversity of abiotic energy sources available."
] |
[
"Hello, geology graduate student currently researching habitability on Mars.",
"The answer to your question is chemotrophy. At oceanic spreading centers, specifically on off-axis hydrothermal vent systems called black smokers, there are colonies of multicellular organisms that live without any photosynthetic energy, and instead subsist on chemicals emitted from the hydrothermal vents.",
"This chemotrophy is generally sustained by microorganisms (bacteria and archea) that gain energy from oxidation and reduction of certain chemical species. I don't have my notes in front of me but the Iron-hydrogen and iron-sulfur redox couples are ones that microorganisms on Earth exploit. This is also hypothesized as a possible mechanism by which life on Mars also arose or persist. Mars has similar geologic environments (low-temperature serpentinite deposits) to those at black smokers, although the processes and life may occur underground.",
"For more information, read about astrobiology, extremophiles, black smoker hydrothermal systems, and theories on how life originated via educational websites (those that end with a .edu).",
"Hope this helps! Cheers!"
] |
[
"One prominent candidate for the cradle of life on earth is these underwater vents - these environments are very stable, even in an age where earth is being bombarded with meteors, they have a ready supply of nutrients and energy that can be accessed relatively easily, and when you look at the genetics of a whole lot of bacterial species it looks as though the earliest forms of life were thermophiles."
] |
[
"About how many atoms could fit in a cell?"
] |
[
false
] |
Alright, alright. I know cells are all different shapes and sizes, but could you do an average iced cell? A single cell that is in the middle of the sizing chart? Thanks. But I've really been wondering about this. Cells are tiny, but atoms are the smallest things in existence. Now, Im no pro at science, ( still In school), but I REALLY want to know. I also read that about 250 trillion atoms could fit in a two dimensional period on your screen,(Answers.com, don't know of they are correct, so sorry if my info is wrong), so I cant really imagine how many could fit in a cell. Thanks!
|
[
"There's no \"average size cell\" because there's such a huge range of sizes, but human cell that's about 10",
" kg would contain approximately 100 trillion atoms."
] |
[
"Wow! Thank you very much!"
] |
[
"atoms are the smallest things in existence",
"Not really. Atoms themselves are made up of a nucleus comprised of relatively tiny protons and neutrons as well as even tinier electrons. Protons and neutrons are made up of even smaller particles called quarks (but since they don't exist in a free state at most conditions, we can skip them). But the smallest known particles (by mass) are neutrinos. ",
"Though physical size is hard to say - the standard model states that elementary particles (electrons, positrons, quarks, neutrinos, etc) have zero size. Physically this likely isn't correct, but they are just too small for us to measure."
] |
[
"Why does it seem like we can see something better if we can hold it?"
] |
[
false
] | null |
[
"What do you mean?"
] |
[
"Like ok if you see something new yes you can look at it but it doesn't always register in your brain what it is. But if you can hold yes it's more senses you can use to identify it but it seems like you can also see it better too."
] |
[
"I'm not sure I understand. Things closer to you are easier to see. Something in your hand is isolated and free of clutter in the background and maybe in that sense could be said to be easier to see. Otherwise I'm not really sure what you're asking."
] |
[
"Why are so many nerve/seizure related drugs used for treating mental illnesses?"
] |
[
false
] |
Why are so many nerve-related/seizure related drugs used for treating mental illnesses? Examples include, Lamotrigine for bi-polar/mood disorder, Gabapentin for anxiety/panic disorder, Venlafaxine for depression, Duloxetine for depression, etc.
|
[
"The real reason is \"because some of them help, sometimes, and the rest is immaterial.\" But that's not a very satisfying answer.",
"Anticonvulsants work by altering neurotransmission, like virtually all drugs used in psychiatry. You can't treat the brain without, you know, treating the brain. For instance, carbamazepine blocks sodium channels on neurons, making them less likely to fire rapidly and repeatedly. This effect is helpful for seizures, but also for mania. Names like \"anticonvulsant\" and \"antidepressant\" really only reflect the intention of whoever developed them, not their actual potential. (Venlafaxine and duloxetine were both developed as antidepressants, though.)",
"The reverse happens, too. Amitriptyline was among the first antidepressants, but is now much more commonly used for neuropathic pain, migraines, or sleep. Benzodiazepines were developed for anxiety, but are the first-line treatment if a seizure doesn't resolve quickly. As for cholinesterase inhibitors like donepezil for dementia, is that a neurologic drug or a psychiatric drug?"
] |
[
"It's more than random luck, but less than predictable. Nearly all neurologic and psychiatric drugs have to clear the hurdles of being able to cross the blood-brain barrier, and do something once they get in. And not all anticonvulsants are popular in psychiatry. For instance, phenytoin (Dilantin) is a very effective anticonvulsant, yet never saw much use in psychiatry. Levetiracetam is quite popular for some forms of epilepsy now, but if anything tends to cause worse psychiatric symptoms.",
"Neurons only have so many things for a drug to bind to, and many are similar enough that one drug can affect multiple targets. In fact, it's often harder to make a \"clean\" or selective drug than it is to stumble onto one that does six different things, half of them undesirable. Likewise, many brain structures and neurotransmitters have multiple different roles.",
"Histamine, for instance, has a hand in sleep, attention, appetite, digestion, and the allergic response. The first antihistamines also blocked lots of other receptors in the brain, leading to experimentation to see what similar molecules might do besides helping with allergies and nausea. The one that happened to also block certain dopamine receptors seemed to help with schizophrenia, and became the first antipsychotic. The one that happened to stop serotonin and norepinephrine seemed to worsen mania yet help depression, and became the first tricyclic antidepressant. Hell, the very first antidepressants were accidentally discovered in the search for better tuberculosis drugs, if you can believe that.",
"Or we could look to the rest of medicine. Beta-blockers have more uses than I can count: Half the cardiovascular diseases, migraines, some thyroid issues, blood pressure, stage fright, essential tremor, excess sweating... The point is, if a medicine acts broadly, it will have broad effects.",
"There are some pretty serious underlying questions raised, sure. How well does our classification of disorders match up with underlying processes? Are we treating those processes, or just symptoms? What counts as mental illness, and what do \"disease\" or \"illness\" really mean to us in the first place? But in the end, there's no good line between neurology and psychiatry, and a lot of drugs work for both."
] |
[
"All of these drugs are blunt tools for prodding neurotransmitter systems to and fro. They are somewhat hopefully and optimistically named after their intended clinical function, but unsurprisingly have broad clinical effects.",
", ",
", ",
", ",
" are all spurious categories. There are structural and functional categories which make a bit more sense—ie, ",
", Nav-inactivators, dopamine antagonists, etc."
] |
[
"If I open a door to an air conditioned room from a warm hallway am I letting warm air in, or letting cold air out?"
] |
[
false
] |
This is something I've always wondered. I asked but didn't get any responses.
|
[
"Assuming equal air pressures, both. The air will equilibrate (mix to an even temperature/energy state)."
] |
[
"The cold air sinks and hot air rises. The cold air is also denser. So the cold air will push out from lower down and the hot air will push in from up high. Probably a little more cold air will fit in the warm hallway since it's denser."
] |
[
"But if the pressure is the same, would that not mean that although the individual particles in the warmer room may have more kinetic energy each, overall both volumes of air would have the same net kinetic energy?",
"If that is the case, then the warmer room should have overall less gas particles, thus resulting in faster per-particle diffusion, but the rate being equal overall from both sides.",
"Im harkening back to my college physics here, so my understanding may be somewhat spotty though."
] |
[
"Would Mercury's close proximity to the Sun make it rich in heavy and precious metals?"
] |
[
false
] | null |
[
"I don't know why you use \"would\". It already is rich is heavy and precious metal. ",
"Planets are formed when after the star (read: our sun) form, materials in the area start to condense and merge together. Close to the star, its hot, so only things that condense at high temperature can condense. Hence Mercury is mostly metal. As it goes further away, things with lower boiling point, like rocks, condense, giving us rocky planets like Earth. Beyond the frost line (between Mars and Jupiter), water and gas can start to condense, giving us all the gas giants and their icy cores. ",
"Astronomy is awesome. "
] |
[
"While it's certainly true that Mercury has a lot of heavier metals; the community hasn't really come to agreement on why. Nebular condensation temperature is important, but that does really explain why Mercury is so different from Venus or Earth. The usual explanation is that Mercury used to have a big, sandy mantle like the Earth, which was mostly lost in a collision with another protoplanet. But I've seen work on radiatively driven migration of elements in the protosolar nebula, so my impression is there's no consensus."
] |
[
"Also, one should not forget that currently astronomers believe there has been a lot of migration from initial planet formation so the old trope of \"rocky planets closer in, gaseous ones farther out\" is not as strong as once thought."
] |
[
"What phenomenon occurs when a full moon creates an observable circle in the foggy night sky around it?"
] |
[
false
] |
[deleted]
|
[
"Without a picture it's hard to be sure, but there are two different phenomena that can cause a ring to appear around the moon:",
"A 22-degree halo",
" can form when high, thin ice clouds are in between you and the moon. The ice crystals refract the light at ",
"a specific angle",
" (around 22 degrees) since they are all regular hexagons. If the ice crystals are oriented randomly, then there will be some reflecting light from every point 22 degrees away from the moon, ",
"forming a ring around it",
". ",
"Example picture",
"A more common phenomenon is a ",
"lunar corona",
". This is due to ",
"a more complicated phenomenon",
": diffraction. This can manifest as white rings, colored rings, or some combination, but almost always very close to the moon in the sky. This phenomenon is more common because almost any thin cloud between you and the moon will make this occur. ",
"Example picture",
"From your description, I suspect it's a 22-degree halo, but check the example pictures I provided to be sure. Another quick check is that your outstretched hand will usually cover a corona, but a 22-degree halo will be much larger."
] |
[
"Saw a moon dog the other night. It was pretty mild evening here in the desert. Was wondering if dust could cause such things in addition to ice crystals. "
] |
[
"Thank you for your reply and photos. I believe it was a 22-Degree Halo in the sky last night. Your picture matched what I was seeing and now I know what to describe it as. "
] |
[
"When others use the English language, I find some accents to be friendly, impressive, sexy, warming; or in other words, superior. I also find other accents to be threatening, cold, unimpressive; or to be inferior. Why?"
] |
[
false
] |
[deleted]
|
[
"This is more linguistics than anthropology.",
"Linguists often study these sorts of language attitudes by using what are called matched-guise tests: they record a single speaker and present utterances to raters as if they were coming from two different speakers. Some of these studies, like ",
"Bilaniuk 2003",
" have a single speaker speak two different languages, while others, like ",
"Campbell-Kibler 2009",
" compare a single speaker and use resynthesized speech to produce two different sets of tokens.",
"What these studies find is that a single speaker can be judged quite differently based on the presence or absence of a either one or a constellation of linguistic features, on the basis of what they're talking about, and on the basis of who exactly is doing the judging. It's not a matter of 'simply recognizing' something about a person. There's nothing inherent to Russian spoken without heavy vowel reduction that makes it an objective marker of low intelligence, or low culture, or submissiveness. There's nothing inherent to saying ",
" (as opposed to ",
") that makes it an objective marker of nerdiness as opposed to jockiness. These are socially constructed meanings, and while people do use them to present themselves as having certain identities, it's important to recognize that these features carry only the meaning we choose to give them.",
"Another interesting finding that bears mention is that of ",
"Niedzielski 1999",
", a study which showed that the social 'information' available about a speaker can sort of 'override' our perceptual machinery. Niedzielski had about 40 Detroiters listen to some prerecorded speech from a Detroiter with the Northern Cities Vowel Shift, a shift going on throughout the Inland North. They then listened to resynthesized vowel tokens and identified which were closest to the Detroiter's speech. All of them heard the same Detroiter, but one half of them were told that the speaker was Canadian, and the other half that the speaker was American. The half that 'heard a Canadian' identified the Detroiter's speech as containing vowels characteristic of the NCVS, while the half that 'heard an American' identified the Detroiter's vowels as being quite standard, and very different from what they actually were."
] |
[
"I don't have much to add to ",
"/u/rusoved",
"'s comment beyond if you want further reading, check out the book ",
", available ",
"here",
". The two applicable chapters are \"Italian is Beautiful and German is Ugly\" and \"They Speak Really Bad English Down South and in New York City\". The basic gist of both chapters are the same: Our perceptions of accents are colored by our perceptions of the people (we think) speak those accents. Southerns are \"stupid\" and \"friendly\", so we say Southern accents ",
" \"stupid\" (but also \"friendly\"!). Most of the media representations we run into in the United States of Germans are of Nazis, and we have stereotypes of German efficiency, so we say that German ",
" \"harsh\" and \"mean\" and \"angry\" and \"clipped\". "
] |
[
"In addition there was an experiment by John Baugh of Stanford where he tried to rent an apartment using several different accents. He's been doing this experiments for years and it's always similar results: when he calls using an accent that is readily recognizable as being from a minority, the renter is less likely to say that the apartment is available. ",
"he sums up his experiment in this clip from a good documentary called \"do you speak american\" from PBS",
"https://www.youtube.com/watch?v=HJ778_tsqjs",
"OP should watch the whole thing, its interesting. "
] |
[
"How does a Belousov-Zhabotinsky reaction work?"
] |
[
false
] |
I understand it has something to do with being 'auto-catalytic' but the explanation I was given was a bit vague. Also, how does it not violate the 2nd law of thermodynamics?
|
[
"It doesn't violate any laws because the oscillation dampens over time. After a short while, the reaction reaches equilibrium and stops making pretty colors. The kinetics of the reactions dictate that it must oscillate on its way to equilibrium. "
] |
[
"This page",
" has a good explanation of how oscillating reactions happen in general. It's a royal pain in the ass to use, but if you want to see the kinetics run their progress with a plot of different concentrations with time, a program called ",
"Kinsim",
" can simulate it for you if you feed it a set of reactions and rate constants."
] |
[
"Do you know any more about the actual kinetics if the reaction? Why exactly dies the oscillation occur?"
] |
[
"Why is carbon dioxide used in fizzy drinks and not another gas?"
] |
[
false
] |
Why not use nitrogen which is a more abundant or another gas?
|
[
"A big reason is solubility. CO2 is soluble in 10 degree C water up to about 2.5 g per liter. Nitrogen is only soluble to 0.025 g per liter under those conditions. Oxygen for instance is at 0.055 g per liter.",
"Some gases are higher, but you don't want to drink them - ammonia can reach 700 g per liter, chlorine gas is around 10 g per liter, SO2 it's 170 g per liter.",
"There are other benefits, too - it's reasonably safe to consume, can be produced in situ by multiple reaction schemes, and the carbonic about formed in water gives a taste that fans of sparkling water will know well."
] |
[
"The dangerous thing about liquid nitrogen under normal circumstances is just its very low temperature and its effective heat capacity due to the liquid->gas transition. It’s used as a way to freeze things very rapidly. Unless the resulting thing is cold/large/conductive enough to give you a frost burn on contact as a result, there’s nothing inherently dangerous about its use. Elemental nitrogen itself is about as chemically inert as anything you’re likely to encounter under normal conditions.",
"This thread is discussing gases dissolved in water at room temperature, rather than as superchilled fluids, which is a very different context."
] |
[
"Most gases dissolve in water, but CO2 is special in that it doesn't just dissolve, it ",
" with water to form carbonate and bicarbonate ions and hydrogen ions:",
"H2O + CO2 <==> HCO3- + H+ <==> CO3-- + 2 H+",
"This does two things. First, it \"clears away\" the CO2, allowing even more to dissolve in. As a result, you can pack a ",
" more CO2 into water than you can other gases -- as ",
"/u/rlgl",
" says, about 100 times more!",
"Second, the hydrogen ions created by this reaction mean that soda water is acidic. That gives it a tart, sour taste that we enjoy.",
"The other poisonous gases with high solubilities that ",
"/u/rlgl",
" mentioned (chlorine, ammonia, sulfur dioxide) also react with water in a similar way."
] |
[
"Did I Get Electrocuted?"
] |
[
false
] | null |
[
"Where should i post this then, cause I'd like to know what may have happened."
] |
[
"Where should i post this then, cause I'd like to know what may have happened."
] |
[
"OK thanks"
] |
[
"What is the biological and/or evolutionary purpose of balding? If there is none, why hasn't it been weeded out by now?"
] |
[
false
] |
[deleted]
|
[
"Traits aren't put there because they are evolutionarily favorable. It's more that traits are taken away because they are evolutionarily unfavorable.",
"There isn't really a selection pressure against bald people - they're still good for surviving and mating and raising kids and such - so there's no reason why baldness can't be passed on. Apparently, it cropped up at some point and hasn't been selected against."
] |
[
"It's more that traits are taken away because they are evolutionarily unfavorable.",
"Which is another way of saying that traits which ",
" unfavorable aren't taken away."
] |
[
"If it doesn't lead to you dying, it will most likely stay there."
] |
[
"Since birds are dinosaurs, are birds reptiles?"
] |
[
false
] | null |
[
"Yes, from a taxonomic standpoint, birds are reptiles. When we classify animals today we base their relationships on a shared evolutionary history. The taxa we name must consist of a common ancestor and all of the descendants of that common ancestor. It's called a monophyletic group. Any other type of group is arbitrarily excluding descendants and won't actually reflect their shared evolutionary history. ",
"We determine these relationships using different sources of data, including DNA and the morphology of living and fossil organisms. Groups are united by features that they share and that are unique to them (or \"derived\"). They will also possess traits that are present in other groups and are \"ancestral\". It's not always straightforward, because things like convergent evolution can happen.",
"Reptiles were traditionally defined by what they're ",
": they were animals that lay hard-shelled eggs (amniotes) that ",
"aren't mammals or birds",
". The term \"reptile\" was used to classify cold, scaly animals into a group, but that completely ignores how they're all actually related. Even some groups more closely related to mammals were considered reptiles, so if you wanted to include everything classically referred to as a reptile in a monophyletic group, you'd just have a group with ",
"every amniote",
", including mammals and birds. If you make the group more restrictive but exclude birds, you're not including all the descendants of the most common ancestor shared by all reptiles. And it seems silly when you think about things, like the fact that we know ",
"crocodylians and birds are each other's closest living relatives",
". Saying crocs are reptiles but birds aren't doesn't change that fact, but choosing to ignore that relationship makes it harder to understand the evolution of these groups. Once you start to look under the hood, you see incredible similarities between birds and other reptiles. Birds are dinosaurs, through and through, and it's really cool."
] |
[
"Reptile is not really associated with an entire clade. The taxon you're actually looking for is ",
"sauropsida",
", which includes reptiles and birds.",
"Reptile",
" is more of an English language word than a proper scientific term because it is not truly associated with a ",
"clade",
" or ",
"taxon",
". But, it's a little fuzzy because ",
"herpetologists",
" study animals in this family but exclude birds."
] |
[
"I do want to point out that for quite some time now there ",
"has been the argument in paleontology that all nomenclature should be based on phylogeny",
" and as a result of that ",
"there do exist",
" true ",
"phylogenetic definitions of Reptilia",
" which include birds, although it's often pretty closely synonymous with the sauropsida you mention."
] |
[
"Would a plant live forever under perfect conditions?"
] |
[
false
] |
As in, if a plant lived in an environment that had infinite nutrients and pollinators along with the perfect quality of soil and atmosphere at all times (as well as free of disease and competition), would it live forever?
|
[
"There is a large, ongoing debate on what exactly defines cellular aging. So a plant made of living cells, like every other living organism based on cell theory, may or may not live indefinitely given completely ideal situations depending on your stance in that debate.",
"Several theories exist in what cellular aging is, and I will only very briefly touch on 2.",
"First is telomere shortening and epigenetic changes. The telomeres are considered \"caps\" on the ends of chromosomes. These telomeres do not code for proteins but act to hold the chromosome together, similar to an aglet on your shoelace. Every time the cell divides, the telomeres get a little bit shorter. Eventually the telomere gets short enough that pieces that are lost in division actually lose genes that code for proteins. Once the genes are messed up, no more of that protein can be made, leading to a cell death. This theory works hand-in-hand with the ",
"Hayflick limit",
".",
"The second theory is called oxidative stress. A cell can be looked at as if it is just a very long interconnected series of chemical reactions, referred to as biochemistry. The reactions are dependent on one molecule and another one interacting in just the perfect way. This only happens in completely ideal scenarios. Realistically, think of it like cleaning. You can use bleach to clean a surface and ammonia to clean. But if these two cleaning agents mix, you now have an unwanted product of chlorine gas. Reactions that are suppose to go one direction can sometimes interact with molecules that send the reaction a completely different direction. The reactions can sometimes make molecules call oxidants. Oxidants can take electrons of neighboring molecules. In a cell, this means that an oxidant can take electrons from a molecule that needs it, say a protein. When the oxidant takes electrons from the protein, the protein usually (sometimes but not always) loses function. ",
"This is only a 1 to 1 molecule interaction of an oxidant to a protein however. Many oxidants are formed constantly. The cells can survive for a long time even though there are oxidants present. The oxidants can be considered sub-threshold injury. The oxidants have to build up to a point where the threshold is passed in order to kill the cell. Before that threshold is crossed, however, the overall efficiency of the cell goes down. If the oxidant ruins enzyme A, the cell can no longer handle substrate A as efficiently as before. The decrease in efficiency can be seen as an indicator of cellular age.",
"The point I am trying to get at is that even if all external factors are perfect constantly, the cells in the plant can still age and eventually die. This response does not take into account the effects of mutations that would occur if no aging occurred.",
"Edit: Formatting"
] |
[
"Of any \"plants\" that would survive in perfect conditions I think woody tissue plants would have the best shot. Their structure and internal functions are largely carried our through already dead cells i.e. the heartwood. The living parts of the tree turnover rather quickly, and get replenished all the time. We have seen trees that are thousands of years old and don't show signs of stopping.",
"Stuff like cancer isn't an issue for plants because they have the ability to just let the part that is diseased get cut off."
] |
[
"Anything that reproduces via clonal colonies like a grass or moss would have the best shot."
] |
[
"How high can a fly fly?"
] |
[
false
] |
Up in the air, in nice weather.
|
[
"You want ",
"this",
" ",
"Basically it has to do with the temperature of the air, needs to be at least 50° for most of them to fly. Not unreasonable to find them over 3k feet, and that's not even taking into account the wind hitchhikers; which have been spotted up 6k feet. ",
"Edit:\nAs ",
"/u/heanster",
" pointed out",
"Just to clarify: this is not 3k above sea level, it's 3k above the ground. I frequent a campsite at 5.5k, and there are flies everywhere. ",
"Edit:\nThank you to ",
"/u/sage_006",
" for the clarification. ",
"That's obviously degrees Fahrenheit? For those people in every country in the world other than the United States that's around 10 degrees Celsius."
] |
[
"How was a fly 'spotted' at 6k feet? Who saw it, how did they know it was there?"
] |
[
"As an avid hang glider pilot, I've never spotted a fly while flying, but I have seen butterflies numerous times at 4-5k MSL. I suspect they get caught in thermal updrafts and can't get out before they've climbed a few thousand feet."
] |
[
"Why do we need sleep?"
] |
[
false
] |
Are there biological processes in the brain that only occur while in REM sleep? Do our cells need "breaks"? Is it like the importance of rebooting a computer? What is keeping us from always being awake?
|
[
"From what I've read, your brain needs time to compartmentalize and go over the events of the day--a PC doesn't learn from its surroundings so it doesn't really NEED a reboot so it's not the same. If people are awake more than a certain amount of time, they become delirious--so this need to analyze information is what is making us tired.",
"/saw this on new queue, decided to comment. Will delete if it's wrong."
] |
[
"There are also certain hormones for things like growth and tissue repair that are released in higher amounts during sleep. In addition, while you're sleeping your body can create and store energy for future use as not as much is being used as compared to when you are awake and performing various activities of daily living."
] |
[
"Your brain spends energy growing new connections (synapses, which equals more axon terminal branches, or maybe even dendrite branches?)\nduring sleep. This forms and/or reinforces memories.",
"I cannot confidently say that this is the ONLY thing sleep achieves. But I am certain that this is true. Those who are significantly sleep deprived show a significant lack of ability to learn (form memories, short term). And also a significant lack of ability to remember (form memories, long term)."
] |
[
"To make tea, I boil water in a glass kettle on a glass stove top. My roommate insisted I put a metal ring between the kettle and the stove so it doesn't crack. Is it really necessary?"
] |
[
false
] | null |
[
"I'll assume this is an electric stove (of course, in a gas stove a spacer won't make too much of a difference).",
"I'm really surprised at that suggestion. To me anyways, the metal ",
" actually limits the area by which heating can occur, so it is actually promoting uneven and localized heating, which increases the risk of glass breaking.",
"When preparing an oil bath for a reaction, for example, care is taken to make sure the bottom of the glass container and the top of the hotplate are dirt free, as a grain of dirt can cause localized heating and cause the glass to crack. So in that sense, we want as much contact as possible.",
"Now, perhaps your roommate is worried about a ",
" change in temperature - a very hot stove and a very cold kettle, and the two makes contact and the whole thing explodes. However, the chances of that happening is quite low, as a kettle is... designed to withstand heat, not to mention the water contained within is an excellent heat sink. Hopefully you're not bringing a kettle out of the freezer to put on a hot stove immediately... A spacer won't save you there.",
"Perhaps the glass experts can chime in on this!"
] |
[
"... it is somewhat sad that this is not obvious.",
"I was in the process of making pickles."
] |
[
"gah, don't pour water in a heated pyrex vessel either, heat it as one unit."
] |
[
"Why do steroid hormones such as Testosterone and Cortisol suppress the immune system?"
] |
[
false
] |
I was reading a book and a chapter of which talks a bit about the mystery surrounding the evolution of steroid hormones such at those in the title and why they suppress our immune systems i.e. what is the evolutionary trade off for that effect? Bearing in mind the book was written in the 90s I wonder if this question now has some satisfactory answers, thanks!
|
[
"First: steroid hormones are a large class of hormones with widely different effects. Even look at the two you named. Testosterone is a sex hormone involved in reproduction, while cortisol is a glucocorticoid, involved in energy regulation and stress responses. Weirdly enough, high levels of either can suppress the other. Anyway.",
"Check out ",
"this",
" paper. Even if you don't have access the whole thing, you should be able to see the abstract which should give you an idea.",
"Its an issue of resource partitioning. Animals have a limited set of resources (energy, carbohydrates, amino acids, whatever) that they have to divide up between body maintenance (including the immune system) and reproduction. Normally an animal wants to keep itself together, so most of those resources go towards body maintenance. When its time for some of that sweet sweet lovin', testosterone and estrogens are increased. Among other effects, the immune system is suppressed, freeing up resources for reproduction, including courtship, mating, pregnancy, and supporting the offspring (assuming they're not left to their own devices). The paper I linked above seems to imply that this trade-off only occurs when resources are limited. If you have plenty of food, enough to support both full body maintenance and reproduction, there's no trade-off to be made and you get the best of both worlds. ",
"I didn't look too much at glucocorticoids because I couldn't find a straightforward paper like the other right off the bat, so this is going to be a bit of speculation. My work is about glucocorticoids, so hopefully this won't be too far off the mark but if someone knows better please correct me.",
"Glucocorticoids are released under stressful conditions like exposure to a predator, new environments, or unsafe environments like the open arms of an ",
"elevated plus maze",
". Acute (short-term) elevations of glucocorticoids actually boost the immune system, while chronic elevations are immunosuppressive. (",
"Source",
") The acute part makes sense-if you get hurt running from a predator, your immune system will be ready to go. But if you're in a constantly stressful situation, your energy needs to go to getting you ",
" of that situation. An immune system won't do you any good if you get eaten, so the immune system is suppressed, freeing up more energy for whatever else needs to be done."
] |
[
"Well, the body needs to know when to stop an inflammatory response, i.e. once the white blood cells are finished doing their dirty work. These chemicals are released as an all-clear. And when they're introduced artificially to the body, that all-clear signal is given when there is still a danger to the body."
] |
[
"Are you sure testoserone suppress it? I thought it was the contrary"
] |
[
"How does your brain determine if a sound is coming from behind or in front of you?"
] |
[
false
] |
Wouldn't you need a third ear for your brain to triangulate a sound and figure out for certain whether it was in front of you or behind you...? How does your brain determine that a sound is coming from behind?
|
[
"For localising sounds, your brain uses a number of cues. Front/back (and elevation) decisions are usually made by exploiting ",
"spectral notches",
". In normal-person language, your head and outer ear is not symmetrical front to back. This means that certain sound frequencies will be more or less dampened by these structures depending on where they come from. So that if you compare the spectra of a sound to what arrives at your inner ear, certain frequencies will be effectively filtered out, creating a 'notch' in the amplitude at that frequency. We're acutally pretty bad at this type of localisation - generally we're only able to localise sounds to within an accuracy of 10-15 degrees in elevation. When sounds are coming from directly behind of ahead, we're also fairly likely to confuse the two. This is because for the most part we like to compare signals between the two ears, and in this scheme those inputs are effectively identical.",
"For left/right (azimuthal) localisations it's comparatively easy, as you can use differences in the loudness of the sounds and even the time delay at which it arrives at each ear. The balance over which of these two cues you use depends on the sound frequency - essentially we use loudness comparisons for high frequencies and arrival time comparisons for low frequencies. Having two ears is great for this and the auditory system employs some of the fastest and most temporally precise brain processing available to make these tiny amplitude and time differences apparent. And consequently you're better at it - you can detect a 'just noticable difference' of around a single degree (this means that you can tell that two sounds coming from this angle apart are not in the same location - to be able to say which is on which side, you need a couple more degrees). ",
"You'll notice this behaviour yourself when you're trying to pinpoint a sound source - you'll tilt your head so that one of your ears is pointing at it (and the other directly away), thereby increasing the most sensitive cues we have for localising sounds."
] |
[
"My answer to a ",
"previous question",
":",
"The way the sound interacts with your head and ears causes some frequencies to be emphasized and others to be attenuated. Since your head and ears are not symmetric front-to-back that effect is different depending on whether the sound came from in front of or behind you. ",
"Relevant Wikipedia article.",
"See also: ",
"Head-related transfer function"
] |
[
"Firstly, check out ",
"this",
" link to follow the anatomy in my description if you like.",
"The inferior colliculus in actually already fairly high in terms of this type of processing. The inputs from the two ears (via the cochlea and audtiory nerve) first enter the brain in the auditory brainstem, located in the pons. There is a fairly well described circuit involved in the calculation of both interaural time and loudness differences - processed in the medial and lateral superior olives, respectively. Impotant things to note - the audiotry brainstem is organised to separate frequencies into a sort of map all the way from the cochlea up to the cortex (though it's a lot more messy up the higher you go).",
"For loudness differences, the lateral superior olives (one on each side) recieve an inhibitory input from the opposing ear (via the medial nucleus of the trapezoid body) and an excitatory input from the closer ear. For each frequency band, there are a bunch of neurons that respond most strongly when their excitatory input is stronger than the inhibitory one. It's a simple push-pull type mechanism where the ear with the strongest input (where the sound is loudest and therefore closer to the source) will drive the biggest response on the lateral superior olive neurons on it's side of the brain. On the other side of the brain, the inhibitory inputs will be stronger, stopping the neurons from signalling on up the chain. This works best for high frequencies - because these are significantly attenuated by your head.",
"For time differences it's more complcated because you have to be extremely precise - your ear is capable of telling the difference down to microsecond ranges between the arrival times of low-frequency sounds at your two ears. Low-frequency sounds aren't so effectivle attenuated by your head, but they have big long waves which lets us detect when they travel past us. That's officially ninja-scale processing and takes place in the medial superior olive. This is a little less understood, but in mammals (birds have a well-studied but different system) the neurons in this nucleus recieve both an excitatory input from both ears, and an inhibitory input from the opposite ear (also driven by the awesomely cool medial nucleus of the trapezoid body). It's thought that this inhibitory input acts to 'delay' one of the excitatory inputs so that they essentially arrive together to drive the neuron very strongly if the time difference matches this special delay. So each neuron would have it's special frequency inputs and its specific delay. Again, this is a symmetrical system.",
"For spectral cues in elevation processing, the story is more complicated and lesser understood. In the auditory brainstem, the auditory nerve also feeds into the dorsal cochlear nucleus, which does all sorts of funky things - like helping to control instinctive ear movements in animals that can move their ears (eg. cats!)- and also in which some neurons seem to be selective for detecting these spectral notches caused by your head-related transfer function. (That's the fancy word for the way your head and shoulders influence sounds as they get to your ear. They can be generalised roughly using sort of average shapes to help make surround sound so convincing.)",
"These cues, calculated and compared in the auditory brainstem, then come togather in the midbrain in the inferior colliculus, which then feeds into the thalamus and auditory cortex. It's important to keep in mind that these cues are originally calculated in one place, then further processed and even recalculated later on, then sort of interpreted and understood even later. It's a very complicated system, so it's difficult to point to one place and say 'here's where we localise sound'. It's very much a group effort requiring a lot of brain areas all doing their jobs. ",
"If you'd like some more info, ask away - my PhD thesis was on exactly this. ",
"Here",
"'s a freely accesible review paper on the topic if you'd like to go full-science ;)"
] |
[
"Are children born with a language acquisition device etched in the human brain or is it developed by hearing language."
] |
[
false
] |
In other words, languages have common rules, if a baby was raised in solitude would they develop their own sense of language with the same rules. i.e. Nouns are things you can point at, and verbs are what they are doing simple rules like that.
|
[
"You are not including sign language acquisition by deaf babies or hearing babies with deaf parents. ",
"http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1868823/"
] |
[
"if a baby was raised in solitude would they develop their own sense of language with the same rules.",
"Probably not, we know this based on children who were not exposed to language during a critical period such as Genie the feral child and other feral children. Some of them are more functional than others and this may be due to some of the children being exposed lightly to language during childhood and/or having more interaction with other people. Genie, I believe was able to learn words and understand things but she wasn't able to get to the level of an average child. ",
"Also what you described is called the forbidden experiment where the question is asked, what would happen if we raised children without any exposure to language. Some of the closest we can get to doing this experiment ethically is via animals and looking at language development in groups were people would not have been exposed to language. Nicaraguan Sign Language is actually the evolution of a made up sign language children in Nicaragua developed. Deaf children in Nicaragua were gathered up and brought to the first deaf school. Before this point they would not been exposed to language(speech or sign) and would have used their own home made signs to communicate. Once at the school, the first generation developed a language on their own to communicate amongst themselves. The school attempted to teach a standard sign language but the children weren't using it. As the generations passed, grammar and structure and rules were being introduced by newer generations of students and eventually it developed into a full blown language. It is children and the successive generations that developed the language. ",
"An experiment was done where zebra finches, a type of bird with a particular song that they sang, would be separated at birth and kept in isolation. This way they would not be exposed to their song. The first generation of finches couldn't even be considered songs, they were just rasps and chirps. These finches were then bred and the next generation instead of being isolated would be allowed to be with their fathers(females don't sing). The new finches at birth would imitate their fathers but would introduce subtle changes. This was repeated, where the finches were bred, and they were paired with their fathers and eventually after multiple generations, a song emerged that was similar to the song that was in nature. \n",
"Zebra Finches Experiment",
".",
"The idea of there being a language module in the brain was championed by Noam Chomsky and he called it universal grammar. A good ElI5 is ",
"here",
". Within UG there is the idea of principles and parameters, where principles are things like \"all languages must have nouns and verbs\" and a parameter would be \"noun first and verb after\". The parameters are what give languages their variation because based on exposure a parameter will be set. So children do seem to have simple rules and default parameters. ",
"Poverty of the Stimulus"
] |
[
"That's... not the way it works. People obviously don't do this voluntarily - children all around the world can be born deaf and grow up in a family that does not know a sign language. So the child develops his or her own language and the parents learn it. "
] |
[
"How come the majority of people in the world are right-handed?"
] |
[
false
] |
Was there an evolutionary advantage to having your right hand as your dominant?
|
[
"To add to the current answer a little bit and address the question in your title, the majority of the world is right-handed due to genetics with some influence of culture. There is a lot of really interesting research out there trying to predict hand dominance early in life. Some people have done studies where the data suggests the direction a newborns head prefers to flop indicates their preferred hand during childhood suggesting that hand preference is something that is born into us. There are theories suggesting there is a single gene we have not identified with one of the more well known ones being the ",
"Right Shift Theory",
". The short explanation of this theory is there is a dominant gene that shifts development towards a left-hemisphere dominant development of language that also shifts our handedness to prefer using our right hand. Most of these theories suggest that we have this gene that shifts us to right hand dominance, but if someone does not inherit the right shift gene then it becomes a 50/50 chance of developing right and left hand dominance which matches up with 10-15 percent of the population being left hand dominant. ",
"Other researchers",
" argue the genetics of handedness are not that simple though since we have not been able to identify a single gene that determines your handedness and instead most theories of handedness and genetics believe it is influenced by multiple genes.",
"We also know that genetics are not the only explanation for handedness due to differences we see across countries, which you can see here on the ",
"infographic of rates of left-handedness by people by country",
". There is also variation within countries as seen by ",
"this map of the US",
" created by the Washington Post. So there is likely some cultural influence on whether someone will be right-hand dominant on top of the genetic components.",
"The why of right hand dominance is probably the hardest part of the question to answer since giving a definitive answer for why evolution resulted in certain aspects of humans is very difficult. It likely has to do with the specialization of our hemispheres or slight changes in the brain structure in some way, however, hand preference is not exclusive to humans. For example, ",
"baboons show a strong right hand dominance",
". Researchers have also found ",
"paw-preferences in cats and dogs",
", although they are no necessarily biased towards the right side like primates. The animal research tends to point towards lateralization of the brain leading towards hand preference, but I can't say I know all of this particular section of research well enough to make a definitive conclusion about that."
] |
[
"I'm not sure that there is conclusive evidence, but the most probable theory I've read is that it's linked to the specialization of brain hemispheres (which in turn is believed to be advantageous for species of higher intelligence - this of course just shifts the problem to the question why our brain is wired as-is): For most people, the left brain hemisphere predominantly handles language and motor skills, and since it controls the right half of the body, this could be an explanation on why motorically difficult tasks are performed with the right hand. It has also been suggested that right-handedness is a byproduct of the development of language (making the left brain hemisphere more important).",
"Also, I think that there is an evolutionary advantage of having a dominant handedness (though it doesn't matter which one here) when a species starts to work on tasks that require learning from others and/or use of tools (sharing knowledge and tools is simpler if both participants have the same dominant hand).",
"One last thing because I thougt it was interesting: If there really were an inherent evolutionary disadvantage of being left-handed, we could expect that the number of left-handers should be zero or close to zero now - this has lead to the hypothesis that left-handedness can also be an advantage in some situations, namely when fighting: Here, it is an advantage to be proficient at \"unusual\" moves, hence to belong to the minority (that this advantage exists can be seen in modern sports, take table-tennis where left-handedness is about twice as prevalent among top players as among the general population).",
"Edit: Most of what I wrote above came from articles to the general public (Why are most people right-handed), but if you're interested, here's an article that discusses the matter (particularly the section 6 on evolutionary forces acting on handedness): ",
"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2666081/"
] |
[
"Has anyone looked at direct cultural ties to left or right handedness? I had temporarily lost the use of my right hand over a medical condition, and came to the realization of how much easier people that are right handed have it when I was learning to write with my left hand. In English, right handers drag away from the fresh ink, left handers have to lift and place, or float over fresh ink to not smudge.",
"In contrast, I have a Jewish friend that is left handed and grew up learning to write Hebrew first. Writing in opposite of English, from right to left, being left handed has the same advantage of dragging away from the ink and naturally not causing smudges. ",
"I can hypothesize there being more left handed people within culture's that write right-to-left just based on ease, but I'm curious see some actual data.",
"Edit: spellcheck"
] |
[
"What effect does the arctic summer sun have on plant life?"
] |
[
false
] |
As illustrated by , the arctic summer sun doesn't set. Does the constant sunlight have any effect on plants in that area? In an unrelated question, how productive would a field of solar panels be under this sun? Would the panels produce a lot more energy than elsewhere in the world?
|
[
"In theory, it would certainly help plants grow. In reality, though, it has very little effect, because the limiting factor of plants in the arctic is nutrient availability. The soil there has a layer of permafrost that prevents anything big and vascular from growing. It's why most plants in the arctic are low-growing shrubs and mosses"
] |
[
"Hey thanks, that's definitely something I didn't think of. How well would a greenhouse work then? If you brought in nutrient-rich soil, would a greenhouse be amazing? This is probably an economics question, but I wonder if the increased sunlight and reduction in artificial lighting would offset the extra heating needed to deal with the arctic cold. "
] |
[
"In theory, a greenhouse should thrive in the arctic. I'm sure it's been done before. But, it would have to be extremely well maintained because if it were to be self-sustaining it'd only be so for a short time in the year, then increased energy costs during the other 6-8 months would likely make the greenhouse inefficient. I suppose if you used CAM plants (ones that temporally isolate carbon dioxide uptake and fixation) during the winter months and C3 or C4 plants during the summer you could have a pretty nice greenhouse."
] |
[
"Is there a material that is the equivalent of a superconductor, but for light instead of electricity?"
] |
[
false
] |
I understand that there are "superconducting" materials which can achieve an electrical resistance of zero ohms - is there a similar material or class of materials (not a vacuum) that can achieve a zero attenuation for light or other EM wavelengths?
|
[
"Not a physicist, hence: wouldn't \"a vacuum\" essentially be OP's answer? Notwithstanding that it's not technically a material."
] |
[
"All materials (that are currently known) have tiny resistances in the absorption and emission of photons. This GIF is a good reference - ",
"http://www.physicsclassroom.com/mmedia/waves/em.gif",
" - which unfortunately means that any EM wave travelling through a medium will be slowed. ",
"If such a \"superconducting\" material existed, it wouldn't violate any laws or anything, but it's resistance would be ≈ 0 meaning it wouldn't even interact with the wave.",
"Tl;DR : Not currently, but it wouldn't do anything."
] |
[
"You're confusing resistance and joule losses with signal velocity, or alternatively absorption with phase velocity. ",
"A superconductor has zero resistance, that says nothing about delaying or slowing a signal. It's resistance and therefore energy loss is zero, but it's reactance can be any value and it's signal velocity could be anything. It's overall impedance could also be non-zero, with a zero real value but a non-zero imaginary value. ",
"If a optical superconducting equivalent existed (beyond the obvious case of a vacuum), it would only have to have zero absorption, no energy loss, the imaginary part of the refractive index zero. It could still have a real valued refractive index for a net subluminal phase velocity. An ideally manufactured fibre optic cable would have zero absorption, but it most certainly would have an effect on phase velocity and refraction at boundaries. "
] |
[
"Is there another type of electromagnetic radiation past gamma radiation?"
] |
[
false
] |
Is there anything with a shorter wavelength than gamma radiation?
|
[
"No. ",
"Gamma rays",
" are, by definition, electromagnetic radiation with wavelengths shorter than 1 picometer (10",
" m, one trillionth of a meter). For some purposes they are broken down into subcategories like ",
"very-high-energy gamma",
" and ",
"ultra-high-energy gamma",
", but these are really just arbitrary categories.",
"If you're confused as to why there couldn't be anything higher: The boundaries between different wavelengths of electromagnetic radiation are largely artificial, human inventions. If a higher-energy photon was discovered or theorized, it would still just be called gamma radiation. There's no fundamental difference between a photon with a wavelength of 1 picometer (gamma ray) or 100 km (radio). The fact that gamma rays are called something different than visible light, radio waves, and x-rays is just a relic of the fact that all these different phenomena were discovered and named independently, far before the realization that they were just different manifestations of the same phenomenon. "
] |
[
"Just wondering"
] |
[
"Even for visible light, the precise border is a bit arbitrary, because human vision doesn't magically stop at a precise wavelength - it just gets weaker the more you get into the infrared / ultraviolet until the intensity needed to see something gets unreasonable."
] |
[
"How does DNA change over the course of our lives?"
] |
[
false
] |
Does DNA change due to life experiences? Could my child be genetically better at handling certain things I’ve had to handle in life?
|
[
"DNA methylation is incredibly stable. It is fun to think about changes in an epigenetic state resulting in some heritable change with their offspring, but I would caution thinking about this differently than a simple change in the sequence of DNA. So while we expect to so pre-programmed changes in methylation and histone modifications as cells differentiate, the stochastic (random) changes in chromatin state (methylation, histones) remains pretty stable relative to other variable changes that might occur.",
"While we do expect to see differential methylation at individual cytosines at a much higher rate than single nucleotide polymorphisms, keep in mind that a single differentially methylated cytosine is not usually sufficient to impact expression levels. Add on to this that most of the changes will revert due to maintenance mechanisms and self-reinforcing feedback loops (which are strongest in areas impacting gene expression or constituative suppression) and you are starting to limit its impact.",
"Additionally, many changes in chromatin state are due to changes in the DNA, making the change occur at roughly the same rate as most phenotypes resulting from mutations. ",
"Lastly, there is a lot we do not know about the heritability of the chromatin state. The maturing zygote seems to erase all epigenetic marks and reform them around the maternal zygotic transition.",
"So your genomic chromatin status changes in a predictable manner as you age and develop in a predictable manner. There are random changes in this chromatin status, and they are theoretically heritable (but we have many unaswered questions here). This can have a big impact on how a cell behaves (ie cancer, dissease), but I think it is important to think of these like DNA mutations and not like some responsive change to external stimuli that can then be passed on. That may be the case, but outside of nematoads we really don't have good evidence (despite looking very hard)."
] |
[
"DNA methylation is incredibly stable. It is fun to think about changes in an epigenetic state resulting in some heritable change with their offspring, but I would caution thinking about this differently than a simple change in the sequence of DNA. So while we expect to so pre-programmed changes in methylation and histone modifications as cells differentiate, the stochastic (random) changes in chromatin state (methylation, histones) remains pretty stable relative to other variable changes that might occur.",
"While we do expect to see differential methylation at individual cytosines at a much higher rate than single nucleotide polymorphisms, keep in mind that a single differentially methylated cytosine is not usually sufficient to impact expression levels. Add on to this that most of the changes will revert due to maintenance mechanisms and self-reinforcing feedback loops (which are strongest in areas impacting gene expression or constituative suppression) and you are starting to limit its impact.",
"Additionally, many changes in chromatin state are due to changes in the DNA, making the change occur at roughly the same rate as most phenotypes resulting from mutations. ",
"Lastly, there is a lot we do not know about the heritability of the chromatin state. The maturing zygote seems to erase all epigenetic marks and reform them around the maternal zygotic transition.",
"So your genomic chromatin status changes in a predictable manner as you age and develop in a predictable manner. There are random changes in this chromatin status, and they are theoretically heritable (but we have many unaswered questions here). This can have a big impact on how a cell behaves (ie cancer, dissease), but I think it is important to think of these like DNA mutations and not like some responsive change to external stimuli that can then be passed on. That may be the case, but outside of nematoads we really don't have good evidence (despite looking very hard)."
] |
[
"DNA does change, but mostly at very slow, random rates (vast oversimplification here) rather than in response to life experiences. That said, as others have mentioned, while the genome isn't changing significantly between generations based on life experiences, the epigenome can and does. We don't have perfect ideas of the mechanism, but it looks like ",
"there are generational changes based on life experiences",
". Probably this is somewhere related to chromatin state, but exact mechanisms for this aren't well understood"
] |
[
"If a human needs 2000 calories per day, could a human be said to run on 96 watts?"
] |
[
false
] |
2000 kilocalories = 8360000 joules 1 day = 86400 seconds 8360000 joules/86400 seconds = 96 watts I have to be doing something wrong here. We don't require on average less than a lightbulb, do we?
|
[
"Surprising as that may sound, you are right, the ballpark power expenditure of humans is roughly that of a 100W light-bulb running constantly. If that sounds surprising, keep in mind that incandescent lightbulbs are extremely inefficient, with less than five percent of the energy put in being converted to visible light. This is because the bulbs are black body emitters, which need pretty damn high temperatures (about 3000K) or so to emit significant amounts of visible light and most of the energy used to heat them up ends up being dissipated as heat (e.g. as infrared thermal radiation). ",
"Edit: An interesting tangent is that lighting, because it is both so ubiquitous and inefficient is actually responsible for a huge fraction of our energy consumption, lighting eating up roughly 20% of all the electricity produced. This is why the switch to significantly more efficient sources such as LEDs may have a large impact on reducing electricity/energy consumption worldwide. "
] |
[
"He didn't claim they are the most efficient, but that they are significantly more efficient compared to incandescent lights."
] |
[
"He didn't claim they are the most efficient, but that they are significantly more efficient compared to incandescent lights."
] |
[
"Can someone die from an adrenaline rush induced by the body ?"
] |
[
false
] |
If someone finds themselves in an intensely stressful situation, one necessitating a fight-or-flight response for example, the body releases adrenaline. Can the body release too much of it, as in a lethal dose ?
|
[
"Pheochromocytoma",
"A condition where excessive adrenaline is excreted is called pheochromocytoma. ",
"Many cardiac manifestations are associated with pheochromocytomas. [26] Hypertension is the most common complication. Cardiac arrhythmias, such as atrial and ventricular fibrillation, may occur because of excessive plasma catecholamine levels. Other complications include the following:",
"Myocarditis",
"Signs and symptoms of myocardial infarction[27]",
"Dilated cardiomyopathy",
"Pulmonary edema: Either of cardiac or noncardiac origin",
"https://emedicine.medscape.com/article/124059-overview#a5",
"If a person was predisposed to stroke or coronary disease and then had a burst of sustained adrenaline, then it can precipitate an event. There are plenty of examples of someone experiencing a preceeding stressful emotional event to go on to have an acute myocardial infarction. In a young healthy person, I have not heard of a severe health consequence from an adrenaline burst...but conceivably possible."
] |
[
"Catecholamine wash of the body can occur for many reasons. Yes one can die. And do. That's why anesthesiologists have better outcomes if talking to the patient the night before surgery as opposed to as they go into the operating room."
] |
[
"Indeed. Isnt this similar to being \"scared to death\"? As in you have a situation so scary that it releases a large enough amount of adrenaline that could kill you?"
] |
[
"Do bugs feel pain?"
] |
[
false
] |
Speaks for itself, do bugs feel pain. and if they do, is it relative to the way human beings do?
|
[
"There is pain and there is nociception. They are related, but distinct.",
"Nociception, the simpler of the two, is the detection of damage or injury. Pretty much all multicellular organisms feel it in some way or another. You could argue that microorganisms feel it as well in a different form.",
"Pain is an unpleasant, partially emotional sensation associated with nociception. The saying is \"Pain is in the brain\"; the signal transmitted by the nerves is nociception; \"there is damage here\"; and the brain processes this into what we call pain. Since pain is at least partially emotional, only animals with a complex enough nervous system to have emotion will experience pain.",
"Insects very definitely do experience nociception. I used to work in a memory/learning lab and we could teach fruit flies with noxious stimuli like electric shock to the feet. They learn very quickly.",
"But I do not think they feel pain; their nervous systems aren't complex enough. I say \"think\" because we don't have any way to measure pain objectively. The only way you can find out how much pain someone is in is to ask them and have them self report. Hard to do with an insect."
] |
[
"https://pay.reddit.com/r/askscience/comments/qsemo/do_insects_feel_pain/"
] |
[
"Absolutely bugs feel pain. Insects actually have surprisingly sophisticated central and peripheral nervous systems that are comprised of neurons very similar to our own. ",
"Now, there is no way to know how they actually experience it, just as there is no way to know if your experience of pain is the same as mine. All we know is that you, me, and the bugs all go to great lengths to avoid it. "
] |
[
"Is there a physical limit to the size of a black hole? If conditions were right, could it continue to draw in matter?"
] |
[
false
] |
Barring any catastrophic collisions or explosions from nearby novas, is there a limit to how large a black hole can get?
|
[
"I've got no idea what that other guy is talking about.",
"Black holes can and do continue to get larger as they absorb more matter and energy. Additionally, no known force can destroy a black hole except maybe hawking radiation, and that would take trillions of trillions of years.",
"Even if you had a supernova explode right next to one, it would just feed the black hole and make it bigger."
] |
[
"No, there's no limit. If you keep throwing mass into a black hole it just keeps getting bigger."
] |
[
"So even if, say, two supermassive black holes collided, it wouldn't get bigger? I have been led to believe that the intense gravity pulls all nearby matter into it, slowly growing. Or does that not increase the size, it's only dependant on the size of the star it formed from?"
] |
[
"Why does the universe not have a \"center\" and \"edges\"?"
] |
[
false
] |
If the universe started at a single point and its space fabric expanded in all directions, at a velocity no greater than c, why does it not have a definite volume? why is there no specific point of origin? Why is there not a current frontier of space, instead of a radius of 14 billion LY of observable universe at every point in existence, which implies that the universe has no limits?
|
[
"I like this answer from Harvard:",
"\nNo. The Big Bang was not an explosion IN space. It was a process that involved ALL of space. This misconception causes more confusion than any other in cosmology. Unfortunately, many students, teachers, and scientists(!) mistakenly picture the \"Big Bang\" as an explosion that took place at some location in space, hurtling matter outward.",
"In reality, ALL of space was filled with energy right from the beginning. There was no center to the expansion, and no magical point from which matter hurtled outward. The confusion arises in part because of the amazing conclusion that the OBSERVABLE portion of the universe was once packed into an incredibly tiny volume. But that primordial pellet of matter and energy was NOT surrounded by empty space... it was surrounded by more matter and energy (which today is beyond the region we can observe.) In fact, if the whole universe is infinitely large now, then it was always infinite, including during the Big Bang as well.",
"To put it another way, the current evidence indicates only that the early universe - the WHOLE universe - was extremely DENSE - but not necessarily extremely small. Thus the Big Bang took place everywhere in space, not at a particular point in space.",
"Source: ",
"http://www.cfa.harvard.edu/seuforum/faq.htm#e1"
] |
[
"It's just really hard to understand that space itself is something. ( atleast for me)"
] |
[
"Most people find quantum mechanics incredibly confusing and impossible to understand, and yet it's one of the most verified models we have ever created. Our own abilities have nothing to do with validity. "
] |
[
"Are molecular ' daisy chains' possible?"
] |
[
false
] |
For instance, could a bunch of benzene rings be linked through each other into a sort of pseduo-polymer - or is there just not enough space in the centre? A couple of other questions in the same vein: Is it possible for two crystals to be constructed through the gaps in each other's structure - locked but not actually bonded? Can organic polymers be bent into rings?
|
[
"So there is an area of chemistry very much related to your question. It's called ",
"Supramolecular Chemistry",
".",
"\nSo as already mentioned benzene rings are too small and have too much electron density to be able to interlink. However with larger rings it is possible, and this class of compounds are called ",
"catenanes",
". So far as I know the record for interlinking rings is 5, it's called ",
"Olympiadane",
". It's a really original name. There are also a class of compounds where you have a ring around a rod that has stoppers on the ends, these are called ",
"rotaxanes",
".",
"\nYou can also get a crystal where you have more than one network that aren't chemically bonded to one and other but can't be pulled apart without breaking bonds (I think this is what you were thinking of). This is called interpenetration. It mostly occurs in ",
"metal organic frameworks",
", these are metal centres with large bridging organic ligands that mean there is a lot of space in the structure. [Cu(4,4'-bipy)2]PF6 is made of 4 interpenetrating networks. I can't find a good picture of this at the moment, but here is a ",
"schematic"
] |
[
"Sure, though you need fairly big organic molecules to get non-bonding connectivity. Benzene rings are too small and too electron dense to allow any bonding through their center but you can do things like make mechanically cross-linked polymer systems where one material is locked into place \"inside\" another.",
"Polymers (or oligomers) can also be bent into end-to-end rings. Due to the random walk nature of polymers this shouldn't happen often though, as when randomly moving around the ends of a long chain it is very unlikely that the two ends will touch one another and even less likely they will touch in the right orientation to bond. However, in certain cases where you have constrained geometry monomers you can get certain size rings in decent quantities, such as measurable 8 and 12 monomer rings where the bond angles work for cycles (just an example). You can also look at the class of compounds called crown ethers to see large regular cyclic organic molecules, and in some sense they could be considered oligomers.",
"As for the intermixing of two different crystal structures I don't have a great example but it could be possible. Putting two different solids in close contact could result in atoms from one migrating into the other and filling the interstitial or void sites. However, long range continuations of one's crystal structure into the other would be very difficult as most structures do not have the right spacing to allow such a pattern. It could be possible with some deformation on small scales though. Someone else might have more info on this topic than I do."
] |
[
"That... is ridiculously awesome. Thanks!"
] |
[
"In the movie Gravity when Sandra Bullock is spinning out of control, would simply closing her eyes stop the spinning sensation?"
] |
[
false
] | null |
[
"Yes, kind of. But only after she stops flailing and waits a few seconds.",
"Rigid objects with no external forces acting on them ",
" will inherently* only spin about a single axis at a constant speed, so all that appendage-flailing changing her moment of inertia and center of mass has to stop. When she holds still at the end of the scene, her rotation smooths out. They actually did really well simulating the physics in that specific case. ",
"According to NASA",
" (and my entire aviation career) the vestibular system will actually reach equilibrium with your rotation ",
", causing the sensation of spinning to disappear after a short time. If she closed her eyes, she would not physiologically experience a spinning sensation except maybe the sunlight shining through her eyelids.",
"This is a famous concept in aviation which leads to lots of spatial disorientation and occasionally flying a perfectly good airplane ",
"into the dirt",
". Essentially your inner ear fluid catches up to your body's spin and stops giving you the \"hey you're spinning now\" signal, which causes pilots to think they're flying straight and level when they aren't. It's also what causes your eyes to repeatedly track one direction and saccade back when you play dizzy bat (",
"optokinetic nystagmus",
").",
"*",
" I was apparently unclear about the one axis thing above for two reasons:",
"Objects with three distinct principle moments of inertia experience a ",
"flipping effect",
" when spun about the intermediate axis, which hypothetically could apply here but does not apply to the general case of rotating objects.",
"Otherwise rotating rigid objects not subject to external forces experience a resultant rotation which can be described by a single axis. If you disturb this rotation by nudging the object briefly you merely change the orientation of that axis. Things don't rotate simultaneously in two different directions without external forces or mass redistribution. If she keeps her arms and legs still, she will resolve to a single rotational motion and her ears will eventually get accustomed to it. We are assuming she stops flailing and spins smoothly because A) it's the ONLY way she can get rid of the spinning sensation and B) she actually does this in the film.",
" For those asserting that you will still feel a \"spinning sensation\" due to centrifugal force, not quite, the axis of tensile force in your body (which is centripetal force) is stationary with respect to your body, and would feel like being pulled apart, not spun around.",
" If you're going to fight about centrifugal force existing or not, take it somewhere else, we don't have to distinguish frames of reference to discuss literal feelings. You're both ",
", one is just more convenient given the situation literally being about her rotating frame of reference and how it feels. In this case, centrifugal force existing is convenient.",
" ",
" To save a lot of extra reading ",
"he says at the end of a several hundred word essay]) -- there's a lot of conflation between the astronaut and a spinning top. This is not a valid comparison, as the top experiences a force from the surface on which it's spinning which is what causes it to precess. Sandra Bullock experiences no such effect."
] |
[
"Wouldn't you have the sensation of centripetal forces acting on you? Those forces would want to pull your arms and legs and legs out unless you're only spinning end over end."
] |
[
"If you are spinning fast definitely! If you spin even faster you can pass out or even die!",
"The red bull guy doing a high altitude jump almost died due to passing out during a spin in free fall!"
] |
[
"When burning fat, what exactly is preventing a person from entering ketoacidosis?"
] |
[
false
] |
So I'm just trying to make sure that I understand this properly. From what I gather type I diabetics are at great risk for entering ketoacidosis because fatty acids are being broken down, releasing ketone bodies into the blood. If a person loses weight and burns a lot of the stored fatty acids in their body, what exactly is preventing them from acquiring ketoacidosis from the fatty acid breakdown?
|
[
"The reason people go into ketoacidosis isn't just that there is a breakdown of fat into fatty acids. It's that (classically speaking) in a type 1 diabetic they have an absence of insulin. What happens is that in the absence of insulin, hormone sensitive lipase breaks down fat into fatty acids that then build up in the form of acetyl-CoA (and from there into ketone bodies). ",
"Normally we would be able to use the acetyl-CoA but this lack of insulin has not been competing with a basal amount of glucagon which encourages our liver to do gluconeogensis. As a result gluconeogensis steals malate from the citric acid cycle. Less malate means less oxaloacetate. Less oxaloacetate means acetyl-CoA can't join in the citric acid cycle. That built up acetly-CoA then is transformed into ketones.",
"What prevents us from going into ketoacidosis when we lose weight is the presence of enough insulin that none of the involved pathways goes too far in the wrong direction: hormone–sensitive lipase so it doesn't release too many fatty acids, the enzymes of gluconeogenesis (and reciprocally glycolysis) so that oxaloacetate doesn't become depleted, and acetyl-CoA carboxylase to sequentially increase fatty acid biosynthesis and slow the rate of fatty acid movement into the mitochondria (via malonyl-CoA) so that you don't get too much fatty acid oxidation. "
] |
[
"Individuals with diabetes type I have absolute insulin deficiency (they do not produce insulin) and therefore this lack of insulin tricks the body into think that it cannot utilize glucose in the body. The body then breaks down other sources ( ex- protein and fats) to generate energy. The break down of fatty acids (from fat ) turns into ketoacids which is the major component in diabetic ketoacidosis (DKA).\nDKA in diabetes type I occurs when the individual is not adherent to their insulin, has an infection, acute stress ( injury, surgery), or possible illicit drug use. ",
"In a normal person, insulin is released so that the body can utilize glucose and prevent the formation of ketoacids. In normal individuals, glucose utilization is preferred so ketoacidosis will only occur in extreme situations such severe starvation where the body runs out of glucose to utilize so it turns to other energy sources. ",
"So if you do not have diabetes type I and you're just losing weight from diet and exercise you will not get ketoacidosis. "
] |
[
"There should really be a requirement that anyone with a question must check wikipedia first.",
"In healthy individuals, the pancreas releases insulin to slow ketone production before the ketone concentration in the blood gets too high. Diabetics cannot produce sufficient insulin, so they can't slow ketone production in the same way.",
"Simply put, non-diabetics slow the process enough so they're safe."
] |
[
"How much land does it take to support one human being?"
] |
[
false
] |
How big does my plot have to be before I can support myself with vegetables and fruit? I live in the UK, so temporate and usually more than adequate rain.
|
[
"The minimum amount of agricultural land necessary for sustainable food security, with a diversified diet similar to those of North America and Western Europe (hence including meat), is 0.5 of a hectare per person. This does not allow for any land degradation such as soil erosion, and it assumes adequate water supplies. Very few populous countries have more than an average of 0.25 of a hectare. It is realistic to suppose that the absolute minimum of arable land to support one person is a mere 0.07 of a hectare–and this assumes a largely vegetarian diet, no land degradation or water shortages, virtually no post-harvest waste, and farmers who know precisely when and how to plant, fertilize, irrigate, etc. [FAO, 1993]",
"From the FAO (the Food and Agriculture Organization of the United Nations",
"Note: .07 hectare = .17 acres"
] |
[
"Well, you can only go so far with vertical gardens because yield is limited by light input. Those squash won't grow as well in the shade of tomatoes."
] |
[
"Well, you can only go so far with vertical gardens because yield is limited by light input. Those squash won't grow as well in the shade of tomatoes."
] |
[
"Why does oil shine in all rainbows colours when it is in contact with water like rain?"
] |
[
false
] |
[deleted]
|
[
"It forms a very thin surface layer on the water. It's so thin that its thickness is in the order of magnitude of the wavelength of visible light. That in turn allows for interference between light reflected on the oil/air boundary with light reflected at the oil/water boundary. What wavelength constructively interferes is also dependent on the viewing angle. Since the surface you look at isn't perfectly flat, you see bands of multiple colours."
] |
[
"It happens when the film of oil/gas has a thickness close enough to the wavelength of light where the reflected beam can cause interference with the entering beam.",
"This i because two different substances with differing refractive indexes cause part of the light to reflect where the two meet and because light is a wave and as such can interfere with itself, causing some colors to cancel out and others to reflect"
] |
[
"https://www.reddit.com/r/askscience/comments/tflhw/what_causes_the_rainbowy_look_in_oil_that_has/",
" - 7yr",
"https://www.reddit.com/r/askscience/comments/1idrfn/why_are_oil_leak_rainbows_the_way_they_are/",
" - 6yr",
"https://www.reddit.com/r/askscience/comments/1a41uf/why_does_a_puddle_of_oil_look_like_a_rainbow/",
" - 5yr"
] |
[
"How many people do you have to have in a room before you can be certain that their birthdays cover all 365 days of the year?"
] |
[
false
] | null |
[
"Thank you for your submission! Unfortunately, your submission has been removed for the following reason(s):",
"/r/AskScience",
"To check for previous similar posts, please use the subreddit search on the right, or Google site:reddit.com",
"/r/askscience",
" ",
"Also consider looking at ",
"our FAQ",
".",
"For more information regarding this and similar issues, please see our ",
"guidelines.",
"If you disagree with this decision, please send a message to the moderators."
] |
[
"Hi! Perhaps my google-fu is not strong, but I couldn't find an answer to this particular problem on google, Wikipedia, or ",
"r/AskScience",
". ",
"The are a couple of common problems that are similar. The most common one is the \"Birthday Problem\", the resolution of which is that if you have 23 people in a room, there is a >50% chance that two of them will share a birthday.",
"There is also one related discussion on ",
"wikipedia",
" around how many people are needed to have a >50% chance of covering all the days of the year, but that is only one specific case and does not address higher probabilities.",
"I believe that what I'm looking for is different than what is discussed in either of those cases, but I shall defer to your judgement if you still disagree. ",
"Thanks for taking the time to review my submission."
] |
[
"I believe what you're looking for is on the birthday problem wiki. There's a section that discusses p(n) and p-bar(n) where p-bar(n) is the probability that all n birthdays are different. I think that's what you're asking for, no?"
] |
[
"Ask Anything Wednesday - Physics, Astronomy, Earth and Planetary Science"
] |
[
false
] |
Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical post? No question is too big or small for AAW. In this thread you can ask any science-related question! Things like: "What would happen if...", "How will the future...", "If all the rules for 'X' were different...", "Why does my...". Please post your question as a top-level response to this, and our team of panellists will be here to answer and discuss your questions. The other topic areas will appear in future Ask Anything Wednesdays, so if you have other questions not covered by this weeks theme please either hold on to it until those topics come around, or go and post over in our sister subreddit , where every day is Ask Anything Wednesday! Off-theme questions in this post will be removed to try and keep the thread a manageable size for both our readers and panellists. Please only answer a posted question if you are an expert in the field. . In short, this is a moderated subreddit, and responses which do not meet our quality guidelines will be removed. Remember, peer reviewed sources are always appreciated, and anecdotes are absolutely not appropriate. In general if your answer begins with 'I think', or 'I've heard', then it's not suitable for . If you would like to become a member of the AskScience panel, . Past AskAnythingWednesday posts . Ask away!
|
[
"I do not think so. For example, Venus is almost the same size as Earth, but its Karman line equivalent would be ",
"around 250km",
". It depends on a planet's atmospheric properties, which is a confluence of factors including its orbit, elemental composition, etc."
] |
[
"Assuming the laws are physics are broken, what do the laws of physics tell us then? \nDo you see the problem? You can't just assume that the laws are broken and the see what the laws are telling us."
] |
[
"First, this is an ask anything thread. ",
"yes, and I don't want to criticise you for asking something. Not at all. But you started your question with: \" assume that time travel is possible\"",
"This assumption immediately breaks physics. So I have to criticise your question. ",
"We also don’t know if quantum effects also happen at a large scale. Faster than light resolution means consequences traveling at c will never catch up. Butterfly effect could mean many small differences could result in a “probability cloud” situation. ",
"Quantum mechanical effects are incredibly tiny on big scales. ",
"This is called quantum decoherence.",
"Close up, it would be hard to see this effect. Far away, the effect would be obvious. ",
"It's actually the opposite. The further out you zoom, the less important quantum effects become. ",
"Now if I understand you correctly, you think that the past is not well defined, it is uncertain? I understand your thinking, but it's not really accurate. Stars are not probability clouds. They are macroscopic objects that don't behave like waves.",
"But! Only one of those causal timelines is visible at once (of course - collapsing the wave function). So, if there are different probabilities that are dislocated in time (I don’t have smarter words for this), then they could still have a gravity effect. ",
"Even if there is large uncertainty in the exact distribution of matter, that doesn't mean there is more matter. Think of an electron in an atom. An atom is a quantum mechanical object, we can only describe it using quantum mechanics. Thus it's location is defined by a probability distribution, i.e. it's wavefunction. But that doesn't mean the atom magically has more charge. The atom still only has 1 negative charge due to this electron. It would be the same with gravity. Just because the location of the electron is given as a probability distribution, it doesn't mean that it has more mass and a larger gravitational attraction. You just have to describe it's gravitational and electromagnetic interactions with probabilities. ",
"But I want to stress this again, that as objects get larger and larger their quantum physical behaviour becomes less and less obvious. It is extremely hard to make molecules of a couple hundred atoms behave quantum physically. A planet consists of such an unimaginably large number of particles that no quantum behaviour could ever emerge. ",
"I also know we have observations of distant galaxies that seem like they have more matter than we observe. We observe about 15% of the matter we expect based on gravity (I think - who is asking the questions around here, anyway!? I don’t know nuthin’!). What if the rest of the gravity is coming from those other probabilities? The “further” they are away (in time) the less impact they would have. ",
"we can measure the distribution of dark matter using gravitational lensing, so the distribution of matter is not unknown. The distribution of dark matter is very different from the distribution of ordinary matter. ",
"So, what would that math look like? I mean, I’m sure this has been explored before. What did the smart people come up with?",
"it's just probability distributions, nothing new."
] |
[
"Where do squirrels go during hurricanes?"
] |
[
false
] | null |
[
"Squirrels nest in hollow trees or in bird-like nests that are larger. In weather, if they feel the need to shelter, they seek anything available that qualifies as an umbrella. Hollow trees are your best bet for finding them sheltering. They will also readily use barns and houses if humans do not disturb them."
] |
[
"They lived in the wall in a place I was renting. I was living in a pretty wooded area so they were everywhere. I never told the landlord...they were my super secret squirrel friends..."
] |
[
"Is this where they typically sleep? Or is this just in extenuating circumstances like extreme weather?"
] |
[
"Violet in photographs?"
] |
[
false
] |
Every diagram I see of the visible spectrum includes violet next to blue. However every photograph I see of refracted light fades to black instead of violet. Is this simply because the RGB filter on a digital camera does not capture violet light, while our eyes do? Or am I just not looking at enough pictures to find a counter example.
|
[
"This photograph has a purplish bit at the end.",
" I suspect you just weren't looking at very good photographs. Filters may have been an issue, although these days digital SLR cameras are capable of capturing ",
"both ultraviolet and near infrared",
".",
"Interesting note on \"Indigo\": Isaac Newton was the first to call it a spectral color, but he wasn't referring to \"purple.\" Apparently, ",
"his notes indicate",
" that he used the word to refer to a color which we would call \"blue.\" This explains the inclusion of the otherwise redundant \"violet,\" and lets us insert an intermediate color between the deep royal blue of \"Indigo\" and the garish, sickly \"Green.\""
] |
[
"Let me help you out with a picture of a rainbow where you see violet :-)\n",
"http://www.flickr.com/photos/charlestilford/189639434/",
"So it appears to be not a general problem. Maybe in special cases where the spectrum of the source is limited ...."
] |
[
"In which medium are you looking at the photographs? Depending on how it is presented (for example a printed magazine vs. a computer screen), reproduction of certain colors can be impossible without spot inks. If it is a digital image you are looking at, provide a link to the example."
] |
[
"What's the cheaper source of energy, electricity or food?"
] |
[
false
] |
ethics aside if i have a man tied up is he going to raise the room temperature higher per 1$ of food, compared to a space heater with 1$ of electricity?
|
[
"Electricity costs on average about $0.10/kW-hr, so $1 would buy you 10 kW-hr, or 36 MJ. For comparison, a McDonald's double cheeseburger costs a dollar and has 390 Calories, or 1.6 MJ. Odds are, a normal food won't be our best bet.",
"A sorta-food option could be cooking lard, which is pure fat. A jar of Crisco retails for about $1 per pound. A 12 gram serving of Crisco has 110 Calories, so one pound will have 4,180 Calories, or 17.5 MJ. Still short of our goal. In any case, even if you could match it for energy content, you'd have significant bodily losses (not all calories are used for heat production, digestion efficiency, etc), whereas electric heating is nearly 100% efficient. Besides, your body's resting thermal output is pretty much constant and he'll be giving off 100W of heat regardless of what you feed him, so no matter what, spending the money powering the heater will increase the room temperature faster.",
"You sick bastard."
] |
[
"If you intend to feed you captive with lobster and caviar, it would probably be cheaper to plug in a space heater. ",
"1 kWh = 3600 kJ, fat contains 37 kJ/g, if (3600/37=)97.3 grams of fat is cheaper than 1 kWh electricity at your location, it might work. ",
"As an alternative scenario, may I suggest you only ",
" to capture that poor bastard, and spend that (lobster and caviar) energy yourself? ",
" "
] |
[
"But that's not entirely fair because the electricity is essentially being mass produced and sold at a price adjusted by the government. Crisco is a name brand, trying to squeeze as much money as they can for their product and not producing at the same scale.",
"I wouldn't be surprised if you could produce your own lard at a better cost. Or if lots of people used this technique for heating, then maybe you could get a company to produce and sell it for a better price. Heck, you can probably buy a non-name brand in bulk for a competitive cost.",
"But your heater probably wouldn't live long. So don't forget to factor in the cost (in time and possibly resources) of replacements."
] |
[
"Are there any substances that significantly help reduce the negative effect of sodium on blood pressure?"
] |
[
false
] | null |
[
"do you want studies or articles?",
"meta-analysis:",
"http://www.ncbi.nlm.nih.gov/pubmed/9168293",
"article:",
"http://www.livestrong.com/article/29315-potassium-lower-blood-pressure/"
] |
[
"basically, with the way the kidneys work, the more potassium you have in your blood, the more sodium is excreted in urine. "
] |
[
"It is true that potassium has the opposite effect on blood pressure as sodium. It is also true that most people don't consume enough potassium.",
"eat more potassium."
] |
[
"Have serial killers always existed?"
] |
[
false
] |
Like in for example the middle ages, were there sick people that killed others for fun then? How about much much earlier?
|
[
"Try ",
"/r/asksocialscience",
" for this."
] |
[
"In the middle ages, there was (probably) Gilles de Rais. He was a noble, and serial murderers who were commoners killing people in a village somewhere wouldn't have made the history books."
] |
[
"Homosexuality was actually quite taboo in old Norse culture. Vikings certainly weren't raping monks in front of each other.",
"That aside, the Viking age was precipitated by a cooling period combined with pressure revolving around the Church. First, farming in Scandinavia became more difficult. The Church had by that time converted many of the Norse's old trading partners, and the Church frequently applied political pressure to heavily tax or outright prevent trade with these heathens. This was combined missionary attempts that frequently involved executing those who refused to convert, burning holy sites and threatening Norse culture. One of the big ways that the Norse were able to survive was by conquering fertile land as they did in the Orkneys, but the primary reason for these raids was the acquisition of wealth. Hence attacking monasteries, which often held quite a bit of gold. This wealth could then be traded. It certainly didn't hurt that the targets were the same guys who kept coming over and threatening their religious practices either.",
"Towns were targeted as well as a strategic move to prevent enemy force concentration."
] |
[
"Does the pocket of air displaced around a fast moving vehicle affect the sound we hear via the Doppler effect?"
] |
[
false
] |
I came up with this question last night after an ambulance sped by my apartment.
|
[
"Short answer: yes. Long answer: only matters if you're a mathematician or searching for perfection. The compression of air for objects below about 370km/h (103m/s, 240mph, 0.3 Mach) is less than 5%, so the predominate cause of the frequency shift will be the Doppler Effect.\n",
"https://www.wikipedia.org/wiki/Compressible_flow",
"\nEdit: source"
] |
[
"I was just watching Top Gear as a Bugatti test driver got the Veyron SS to ~263mph; probably not enough over that 240mph threshold to matter much....?"
] |
[
"i know how the Doppler effect works; i'm specifically asking is it/how is it affected."
] |
[
"What speed does gravity propagate at?"
] |
[
false
] | null |
[
"See the FAQ"
] |
[
"I had a brief look, and I couldn't see the question I was looking for. Could you point me in the right direction?"
] |
[
"It's under the astronomy section:",
"https://www.reddit.com/r/askscience/comments/1kjp6z/does_gravity_travel_at_the_speed_of_light_if_the/cbpmm9a/"
] |
[
"Could you get ripped by consciously flexing your muscles for the majority of your day?"
] |
[
false
] |
I sometimes try to flex my core to help with back spasms and it seems to help.
|
[
"Possible to get ripped? No. Possible to make the muscle more stable? yes. ",
"The \"ripped\" look is caused by (among other things) hypertrophy of the muscular cells. The actual cause of this change is unknown, but is hypothesized to be in part a reaction to the soreness (and hence the microtears/DOMs) caused by weight lifting. The majority of the microtears occur during the ",
"eccentric contraction",
" phase of the muscle, when it can produce up to 40% more force than it does in the ",
"concentric contraction",
" phase.",
"Also, the ",
"SAID Principle",
" would indicate that with sustained concentric contractions, the muscle would simply get used to that, and would not gain further strength once it adapted to the contraction.",
"As to the item you noticed in flexing your core to help back spasms, both muscle groups are a part of your \"core.\" All your body movements will use these muscles in one way or another. If your abdominal muscles are not stable, then your spine and paraspinal muscles will have to work overtime to keep your body stable during a given motion. If your abdominals are stable, then it will take the extra strain off of your spine and thus, make the muscles more able to relax and not as likely to spasm."
] |
[
"I replied in the thread if you would like to read it :)"
] |
[
"Technically, I think you could.",
"I've tried this. It's... exhausting, and there seems to be some sort of fail mechanism in your body that makes you tired, bored, and want to stop. Also, it's embarrassing. In the end, it's probably more effort than going to the gym and I think there might be a risk of stroke, hernia, a some sort of internal rupture from all that straining. "
] |
[
"Does fluoride in tap water really have any noticeable effect on houseplants?"
] |
[
false
] | null |
[
"Yes and no..\n depends on the plant... or more particularly the root zone. ",
"If you are trying to grow organic vegetables for instamce the floride can effect the microbes in the root zone that help with nutrient exchange... ",
"If you are throwing miracle grow in a planter for flowers its probably not a big deal.",
"It also depends on whether the nutrients are chelated or not. If the nutrients are already ready for absorbtion by the roots... the floride is less noticable. ",
"If not... the rhizosphere will need the symbiotic relationship with fungus and microbes like mychorrizae to help convert non-chelated nutrients to a usable format."
] |
[
"I'd honestly worry about the chlorine long before the flourine in most cases (but maybe that's because I keep aquariums), although obviously you can keep ordinary houseplants using standard tap water(or else they would hardly be popular houseplants)"
] |
[
"Not as house plants, but i have an organic garden and i only use stored rainwater."
] |
[
"About collisions on the Moon."
] |
[
false
] |
After watching video, I was wondering why hasn't there been any major collisions that we have observed? Is it just because there aren't many objects traveling in the orbit of the earth/moon? Sorry for any confusion or errors.
|
[
"It's because there just isn't as much loose stuff floating around the Solar System these days. Likewise, we haven't had any major impacts on Earth in a long time, and the Earth is much larger and more massive and therefore more prone to being impacted. The largest meteorite impact since the invention of the telescope was the Tunguska Event in 1908 (caused by an asteroid or small comet airbursting over Siberia), but had it hit the Moon we probably would not have noticed.",
"Early on in the Solar System's history, the place was full (by which I mean still almost entirely empty, but not quite as empty as today) of material, most of which got cleared out by around ~3.8 gigayears ago during the Late Heavy Bombardment.",
"Edit: Also, basically all impactors originate not from the Earth-Moon system but from the broader Solar System, including the main asteroid belt between Mars' & Jupiter's orbits, comets from the Kuiper Belt, and other loose asteroids floating around."
] |
[
"I like this answer but I want to give one nitpicky correction: There are plenty of large things floating around in the asteroid belt. However, they are in stable orbits and in recent history nothing has perturbed those stable orbits.",
"Also the LHB is hypothesized at this point. "
] |
[
"Thanks for the clarification!"
] |
[
"Can you see evidence of the boundary layer on an airplane wing?"
] |
[
false
] |
I was recently flying and I noticed (although not entirely clear) that the air on the top of the wing seemed distorted, like light going through a prism. Is the difference in density in the boundary layer and surrounding air great enough to refract the air so that the naked eye can see it? Or was I just seeing an optical illusion?
|
[
"I was recently flying and I noticed (although not entirely clear) that the air on the top of the wing seemed distorted, like light going through a prism. Is the difference in density in the boundary layer and surrounding air great enough to refract the air so that the naked eye can see it? Or was I just seeing an optical illusion?",
"Good observation. First, yes, you can see evidence of air density changes on an airliner wing, and really just like a prism. ",
"Schlieren imaging",
" is used in experiments to visualize fluid flow based on the principle that different density regions will refract light differently. Part of what you're seeing is probably more due to water condensation in the air, but that effect is a function of pressure, which itself is partially a function of density variations. At the transonic speeds that airliners fly at, there is considerable density variation over the surface of a wing, and this is what you're seeing.",
"Second, to clarify, what you're seeing is not what is called the \"boundary layer.\" The boundary layer (as normally defined) for something like an airliner is on the order of ",
". I'm guessing the scale of what you saw was ",
"closer to this."
] |
[
"Any real observable effects of the pressure gradient would not come directly from the air itself. Much more likely that you are seeing the end result from the interaction of water particles in the contrail that forms on the plane wing.",
"I don't know whether contrail formation is defined by the boundary layer though."
] |
[
"I was observing this from the front of the wing so I don't know if it would explain this. I might have just been tricked through the window or something, was curious if anyone knew.",
"The contrail effects are due to vorticies at the tips of the wings from the pressure difference on the top and bottom of the wing. The pressure drop causes water molecules to condense rapidly. Hope that helps."
] |
[
"[Neuroscience] What is the difference between anticholinergics and antihistamines?"
] |
[
false
] |
Both of them seem to be described similarly, and I have heard people use them interchangeably. I found one source stating that antihistamines such as dyphenhydramine produce anticholinergic effects. If that is true, then why wouldn't it be classified as a histamine antagonist? Is the histamine system a subsystem to acetylcholine like the nicotinic receptors and muscaric receptors? I'm very confused. Are the histamine and acetylcholine even related at all?
|
[
"The simple answer is that mACh-receptors and histamine1-receptors look fairly similar to each other which allows for a lot of cross-reactivity. First-gen anti-histamines like diphenhydramine (which cross the blood brain barrier) are primarily anti-histamines (edit for clarification: histamine1-receptor antagonists), but they can also bind to mACh-R's because of the structural similarity. This mACh activity is probably what causes drowsiness with the first-gens (acetylcholine seems to be tied to alertness), which is why the 2nd-gen antihistamines (\"non-drowsy\") have gained in popularity (they don't cross the BBB, so they can't antagonize central mACh receptors). "
] |
[
"Thanks, this answers a lot of questions for me."
] |
[
"one thing that is critical to understand is that no drug is 'truly' specific for a certain receptor, or even receptor subtype. This goes for anything really, if you saturate a system with enough of a compound it will eventually start binding to non-specific receptors (in other words, it has lower affinity for these receptors due to its intrinsic structure, charge, etc). ",
"A lot of antihistaminergic, anticholinergic, antidopaminergic, and even antiandrenergic agents share a common structural motif, and some are even derivatives of each other. IE: certain antipsychotic medications (antidopaminergic primarily for the earlier generations) are derived from diphenhydramine, and they are also fairly potent at cholinergic receptors. as always, we are able to develop drugs that are more specific for a certain receptor and/or receptor subtype, but that does not always translate to better efficacy as these pleiotropic effects can often be beneficial in the clinical effectiveness of the drug. "
] |
[
"Why is it that we literally feel \"heartbroken\" (physical pain in chest area) when we get sad? What is going on?"
] |
[
false
] |
Would love to hear about the chemical, neurological, physiological, and/or any other basises for this phenomenon.
|
[
"The vagus nerve, which is the main nerve connection between the brain and our internal organs, has a lot to do with it:",
"Excessive activation of the vagal nerve during emotional stress, which is a parasympathetic overcompensation of a strong sympathetic nervous system response associated with stress, can also cause vasovagal syncope because of a sudden drop in blood pressure and heart rate. Vasovagal syncope affects young children and women more than other groups. It can also lead to temporary loss of bladder control under moments of extreme fear. (wikipedia)",
"Essentially, I guess, there is a certain amounts of bio-feedback between physical sensations and emotional sensations. If the emotional sensation is sufficiently intense to incite stress, the stress chemicals trip our physical systems, which leads to physical discomfort or pain. ",
"This is also a partial explanation for the wide-spread physical effects of stress (such as cardiovascular problems, depression, etc.) because when the stress is caused by emotions or social situations (which our evolutionary antecedents who developed the early parasympathetic nerves would probably not have experienced) we know a \"fight or flight\" reaction is impossible, unnecessary, or unwise, but our body continues to prime itself for a physical response to emotional stimuli, leading to strains on the cardio system (due to increased heart rate, adrenaline, etc.) and a build up of stress chemicals in the blood stream.",
"Apparently there is some research evidence to suggest that vagus nerve stimulation ",
"(VNS) can help treat depression and epilepsy",
"."
] |
[
"Don't forget, being \"heartbroken\" can lead to ",
"takotsubo's cardiomyopathy",
", which is incredibly interesting. Perhaps a cardiologist could shed some light on it other than just wikipedia."
] |
[
"I'm pretty sure chest pain's a symptom of vasoconstrictors, and vasodialators relieve angina.",
"Vagus is parasympathetic BTW, rest n' digest. "
] |
[
"Is there a relation between the amplitude and the frequency of electromagnetic waves?"
] |
[
false
] |
From what I know the energy of electromagnetic waves, or any waves for that matter, is quadratically dependent on their amplitude. That amplitude is dependent on the amount of photons the wave consists of, making it quantised. On the other hand, according to the Planck-Einstein equation E=hf, or the energy is linearly dependent on the frequency of the wave. Does this mean that the amplitude and the frequency of any specific electromagnetic wave are related? This doesn't seem to make much sense, as they should be independent. Or am I just misinterpreting this and does the Planck-Einstein equation just tell us how many photons of any specific wavelength are produced by a black body? Apologies in advance if this is a remarkably stupid question :)
|
[
"No there is not. The amplitude can be thought of as the number of photons that make up a wave (although it is a bit more complicated than that), each with their own energy."
] |
[
"Thanks for the answer. Now if you look at an EM wave consisting of just one photon, the energy in this wave depends quadratically on its amplitude, or E~Ampl². But the energy according to planck/einstein is purely dependent on its frequency, or E~f. Doesn't this imply that freq ~ Ampl²? And wouldn't this effect then remain if we're just adding up photons to form a more everyday EM wave?"
] |
[
"Isn't the energy then equivalent to the intensity times the speed of light, making it still dependent on the amplitude of the wave?"
] |
[
"The Universe is expanding, but what into?"
] |
[
false
] | null |
[
"It is largely accepted that the Universe is expanding, but what is it expanding into?",
"It's not expanding \"into\" anything. The statement \"the universe is expanding\" means \"the distance between any two sufficient distant objects increases in time\".",
"If one found itself at the wall of the Universe could you somehow break through it to see the other side?",
"So far as we're aware, there is no \"edge\" of the universe; it either wraps back around on itself smoothly, like a three-dimensional version of the surface of a sphere, or is infinite in extent. Current data favors the infinite case, but it's not something we can determine conclusively."
] |
[
"How is it possible for something to be infinite in size though?",
"Why shouldn't it be possible?",
"Sorry, I’m not very familiar with the theory but wouldn’t you run out of matter eventually as even though there would be a large amount there must be a finite amount.",
"Why do you think there must be a finite amount of matter? Our current physical models impose no such restriction, being perfectly capable of considering both infinite and finite spacetimes. Which we actually live in is a matter of observation, and the relevant parameters that we've been able to measure (such as the energy density of the observable universe) tend to favor an infinite universe over a finite one."
] |
[
"How is it possible for something to be infinite in size though? Sorry, I’m not very familiar with the theory but wouldn’t you run out of matter eventually as even though there would be a large amount there must be a finite amount."
] |
[
"Why are cochlear implants limited to human range of sound?"
] |
[
false
] |
It seems like it might be able to be extended (i.e. could hear dog whistles, etc.). Is it a limitation with the brain, the technology? Or is it simply to give the recipient "normal" hearing patterns?
|
[
"Sure, we have the technology to increase the frequency range on cochlear implants, but the reason they aren't is because human communication is done well within the range of normal hearing. Focusing on that range is the most efficient way to use the limited number of electrodes (22) that replace the 16,000 or so hairs normally used for hearing. Taking just one electrode outside the normal range of hearing would reduce the overall efficacy of the device with no improvement of the main purpose of the device, communication. "
] |
[
"I think there is something you are not taking into account. The way to increase the audible range is through the microphone and electronics. Very high-frequencies, say 50 kHz, could be programmed to excite one of the electrodes in the cochlea. As a result you would \"hear\" the 50 kHz sound in the sense that your brain would detect sounds at that frequency. To make it even more extreme, you could connect the cochlear implant to a light sensor in such a way that you could \"hear\" how much light there is."
] |
[
"I think there is something you are not taking into account. The way to increase the audible range is through the microphone and electronics. Very high-frequencies, say 50 kHz, could be programmed to excite one of the electrodes in the cochlea. As a result you would \"hear\" the 50 kHz sound in the sense that your brain would detect sounds at that frequency. To make it even more extreme, you could connect the cochlear implant to a light sensor in such a way that you could \"hear\" how much light there is."
] |
[
"Do we know of any genes that still produce a protein but its receptor has been lost?"
] |
[
false
] |
Like the title says, is there any gene that produce a protein that used to bind to a receport, but the receptor has been lost somewere down the line.
|
[
"Well in bacteria, their sequences could contain genes that they acquired from other bacterial species. So if that gene is active/producing a protein, it's possible that it serves no purpose if that protein only can be used by the bacterial species of origin. Maybe a microbiologist could clarify/correct me"
] |
[
"I can't think of one (at least, endogenously), and it wouldn't make sense for something like this to exist from an evolutionary standpoint. The closest thing I can think of is the reverse of what you're asking. This we refer to as ",
"orphan receptors",
". However, it's not that the endogenous ligand isn't produced, it just hasn't been identified yet."
] |
[
"I presume the proposed schedule is:\na) Gene produces protein which is useful & has receptors etc\nb) Something changes so that having that protein active is now actively harmful\nc) Mutation arises that turns the receptor for the protein off\nd) This contextually helpful mutation spreads through the population, leaving an 'orphaned' protein still being produced.",
"Doesn't seem impossible. It wouldn't be remotely tidy but evolution very often isn't.",
"No idea how plausible it is in reality, it'd depend on a bunch of things I've no idea about :)"
] |
[
"Can I have my DNA sequenced to find out my ancestry?"
] |
[
false
] |
Is there a place that would do this for a reasonable price?
|
[
"The Genographic Project",
" will give you information about your ancestors over the last ~70,000 years. Also, you can agree to having your DNA sequence placed (anonymously) in a large database of human sequences."
] |
[
"After the Genographic Project I was invited to have more tests run on the original sample they still had (they may still do this for free, I don't know ) by familytreedna. This got me in touch with people I had a certain number of markers in common with, some of whom shared my last name. After finding these people with the matching markers, and the matching last names, we just compared ancestors ( I didn't do all the leg-work myself, that was my long lost relative's doing, but that was the general process ). "
] |
[
"23andMe",
" may be what you're looking for. Sometimes they offer \"free\" kits with a year-long subscription to their analysis service (of $12/mo)."
] |
[
"Dish soap and bubbles. A common marketing ploy?"
] |
[
false
] |
Growing up, I've always looked at a sink filled with dish soap, and assume it's good stuff because, well... there's a huge amount of bubbly foam around it. The bubbles mean it's hardworking clean chemicals right? I look at it now, and I think: Why does this foam happen? I use sanitizer solution and this does not occur. Are the bubbles a result of legitimate reaction to the chemicals that work to keep our dishes free of bacteria, or is it just something else put into these products to make people have a visual appreciation?
|
[
"Sanitizer and soap work very differently. Sanitizer works by either killing the bacteria (like bleach) or removing it directly (like alcohol). Soap works with agitation to trap oil in balls that are soluble in water, and then washes whatever was attached to the oil down with the water. Unlike sanitizers, bacteria don't really become resistant to soap.",
"If you want the ideal oil-trapping soap, then you want it to create bubbles whenever you agitate it."
] |
[
"Nope.",
"Bleach and alcohol disrupt cells by chemically wrecking their membranes and cell walls. There's not really any way to become resistant to this. Antibiotics are a lot more subtle, affecting specific bacterial enzymes or structural molecules, and so are easier to evade or disrupt.",
"By analogy: it is possible for humans to develop a tolerance to spicy foods, and be able to eat habanero peppers without pain. But no matter how much you practice, you can't develop a tolerance to being hit with a sledgehammer."
] |
[
"Bacteria become resistant to bleach and alcohol?"
] |
[
"Why does heat rise?"
] |
[
false
] |
I know the typical explanation is that as air gets hotter, it expands, thus becoming less dense, and rising. But that only really makes sense if it's trapped in a balloon or something, right? I mean, it's the individual molecules that are hotter, and individual molecules can't become less dense... Or can they?
|
[
"A higher temperature means that the particles (could be molecules, could be single atoms, etc.) are vibrating more. When you have lots of particles together, making up air, the fact that they vibrate more causes the air to expand, making it less dense, so it rises, as you say. ",
"If you have an individual particle, the discussion of temperature and density becomes more difficult. Temperature is a statistical mechanical quantity, and only really well defined for large numbers of particles. But, loosely, one could say that a hotter particle vibrates with a larger amplitude, so \"takes up more space\" but still has a constant mass, meaning the density in the region the particle vibrates in will go down.",
"A better way to think about is is to imagine you've got N particles, taking up a volume V. As above, when you heat the particles, the volume goes up but the mass stays the same, so the density goes down, so the bulk volume of particles will rise. What you could do is just divide the volume V by the number of particles N, then you'd have a representative volume that an individual particle (on average) might move within when it vibrates. When the full volume goes up, this smaller volume must go up too, meaning that, in some sense, the individual particle has effectively become less dense. "
] |
[
"The mean free path of molecules in air is < 100nm. This means they don't travel very far without bumping into one another, and generally don't travel very quickly. They're kept in little neighborhoods by the surrounding particles.",
"Therefore, the assumption of treating small patches of volume as continuum fluid packets (rather than individual molecules) is actually quite good.",
"EDIT: Also, you should really think of it as cold air falling rather than hot air rising. The denser cold air pushes the less dense hot air out of the way as it is pulled down."
] |
[
"It helps to think of air like a fluid, like water. The oceans have currents because cold, dense water sinks (and there are many of factors but ill ignore those). Likewise cold air is ",
" more dense than warm air so it sinks. This will cause the air to circulate. As far as heat transfer goes, this is convection-when heat is carried around by a mass of liqiud. Heat can also be spread by diffusion, but it is negligeable on a macroscopic scale. (Note that heat is not the same thing as temperature)",
"Be careful not to mix ideas pertaining to macroscopic and microscopic. The influencing factors on individual molecules is very different than on a large volume of gas."
] |
[
"Why does it appear that electrons, neutrons, and protons are more common in the universe that positrons, antineutrons, and antiprotons?"
] |
[
false
] |
Does the universe have equal amount of antimatter as it does matter?
|
[
"Nobody knows why there is no natural antimatter, but there are some educated guesses.",
"Once upon a time (as recent as the 1960s) many scientists thought that while matter obviously dominates within our region of the universe, there should also be regions of antimatter. This was reasonable because it was produced in equal quantities inside a collider, and it appears exactly identical until it touches normal matter.",
"However, when matter touches antimatter it produces a characteristic flash of gamma rays. It also stands to region that there should be ",
" between regions of matter and antimatter, and that these borders should be highly visible sources of telltale gamma radiation to a modern gamma ray observatory.",
"No one ever found gamma rays from a border region.",
"This leaves us with two reasonable possibilities:",
"1. The borders are just really, really big and happen to be so far away that we can't detect them.",
"This is an unsatisfying explanation because if the nearest border is beyond the edge of the observable universe then it is unfalsifiable. However, it is not necessarily wrong.",
"2. Existing physics is wrong and antimatter behaves differently from matter in some way that led to it being less common.",
"Such a difference is called a ",
"charge parity violation",
"; two otherwise identical particles with opposite electrical charges should behave the same.",
"People have known about CP violations for a while (check the link), although overall symmetry is conserved if you ",
"consider time as well",
". No one has been able to translate observed CP violations into a mechanism that could explain the apparently total lack of natural antimatter."
] |
[
"This is currently a mystery."
] |
[
"tl:dr; There ",
" more matter than antimatter, we don't know why, lots of smart people are working on it, it may lead to a deeper understanding of the universe.",
"Question two first: \"Does the universe have equal amount of antimatter as it does matter?\"",
"We are very confident that the universe is utterly dominated by 'normal' matter. ",
"If there were significant amounts of anti-matter, we would expect to see it collide with 'normal' matter occasionally. It's very unlikely that there are any \"anti-matter galaxies,\" for example. We see galaxies colliding all over the sky at all distances (so, all ages of the visible universe.)",
"If even one of these were an anti-matter galaxy it would be really really obvious. Like, hydrogen bomb in the living room obvious. We would see it. We have never seen anything like this.",
"It is possible that some of the very bright things we see in really distant==old areas may involve anti-matter, but I don't think we've seen anything that really looks like it.",
"Now onto question one: Simple answer: We have no bloody idea whatsoever. Or, more accurately, it's one of the biggest puzzles in science, and we have a thousand ideas, but not a single good one. Really, it's well inside the top ten puzzles about the universe. So, top marks for asking this one!",
"Most models for the big bang predict equal amounts of matter and anti-matter. (handwaving a bit) This is one of the symmetries that physicists care about (actually, they really care about charge, parity and time, but matter/antimatter evolves from that.)",
"The key word here is symmetry. The apparent lack of antimatter seems to imply that a symmetry is broken. We don't know which one, how it is broken, or why.",
"However, we have identified and solved mysteries like this before. Chirality of beta-decay is the famous example - a broken symmetry that hinted at an entirely new fundamental force - the weak nuclear force.",
"So - it's a ",
" good question, it's a fascinating area for theoretical and experimental research, there's no reason to believe we ",
" find out, and it may very well lead to a richer, deeper understanding of the universe."
] |
[
"Would consistently exposing an infant to a foreign language help it with said language later in life?"
] |
[
false
] |
If I, for instance, played German movies or music to the kid during the day, would he have an easier time learning German, or would it just muddle with him learning English? Would early development be a good time to introduce multiple languages, or would they just get all mixed leaving the kid unable to speak one?
|
[
"Take out the \"foreign\" part, and this is how every baby in the entire world learns their native language(s). To learn a language you have to be exposed to it. It just takes a lot of exposure over a long time. If a Japanese baby is born in Japan to Japanese parents, but is locked in a room and never hears the language, the kid isn't going to learn Japanese (or ",
" language for that matter).",
"Absolutely not. Babies are extremely good at differentiating languages. There are millions upon millions of babies that grow up bilingual, we'd have noticed by now if it negatively impacted their language ability. The only sort of \"negative\" impact is that multilingual babies take a bit longer to reach language acquisition milestones than monolingual babies--but later on the multilingual babies catch up, so there's no real effect.",
"I won't say it couldn't perhaps aid the kid to some degree if he goes to learn German later in life (I've seen various claims before, so the linguist jury may still be out on that one... Not really sure). But almost certainly it won't make him fluent. Kids don't fully acquire a language just because they happen to hear it. They acquire a language because there's a ",
" to use it that's motivating them. They want to communicate with mommy and daddy, and to do that, they need to figure out how to speak their parents' language. That's a pretty strong motivation. But just playing it to them on a TV? There's not much motivation there. They also need practice using the language to be able to speak it, and if there's no human around that speaks German, then they're obviously never going to get any practice.",
"Yes. If multiple languages are introduced to a child early on, they can attain native fluency in multiple languages. A lot of children of immigrants are a good example of this, because they learn one language from their family and one language from the community. There are other ways to raise bilingual children too. Each language has to be exposed to the child for a very long time though (until they grow up), otherwise they can lose their ability to speak it."
] |
[
"I'd agree that's not the most appropriate for this subreddit due to it being anecdotal, as well as a misinterpretation.",
"What goes on in their speech and what goes on in their minds are two very different things. Multilingual babies (even the ones only learning two languages) tend to mix languages for a while--only in speech though, it's not some jumbled confused mess in their minds. They don't think they're all the same language. As for why it sounded like gibberish, I'd guess because (a) kids are hard to understand in the first place, and (b) it's really hard to tell what's what when the kid's mixing together 4 languages.",
"If the kid is learning 4 languages and not getting a great amount of exposure to any one, then you're probably going to see a rather extreme version of the \"delay\" (mentioned in previous comment). That doesn't mean it was necessarily detrimental to anything. It just means you're giving a kid more to deal with, while exposing it to less of any given language, so the kid's going to take a good bit longer to sort that out and get the amount of language input they need to progress.",
"When you're juggling 4 languages, you're likely not going to do a great job at getting the kid sufficient input in ",
" of them. When there's insufficient input you tend to see partial acquisition in some of the languages--but importantly not all the languages, the kid will ultimately learn the language of their community no matter what. This can happen even when only learning two languages.",
"If the parents had kept what they were doing, you would have still seen a difference around the time the kid entered school. Once children go out and be a part of the community, their dominant language becomes that of the community (if it wasn't before--sometimes it is, sometimes it isn't). So the kid would have made rapid progress in English (if she lives in the US, or wherever), while the progress of all the other languages she was acquiring would depend on whether she was continuing to get exposure to them through her family. If they stopped exposing her to the non-English languages, then she largely lost what she'd learned (called language attrition)."
] |
[
"I'd agree that's not the most appropriate for this subreddit due to it being anecdotal, as well as a misinterpretation.",
"What goes on in their speech and what goes on in their minds are two very different things. Multilingual babies (even the ones only learning two languages) tend to mix languages for a while--only in speech though, it's not some jumbled confused mess in their minds. They don't think they're all the same language. As for why it sounded like gibberish, I'd guess because (a) kids are hard to understand in the first place, and (b) it's really hard to tell what's what when the kid's mixing together 4 languages.",
"If the kid is learning 4 languages and not getting a great amount of exposure to any one, then you're probably going to see a rather extreme version of the \"delay\" (mentioned in previous comment). That doesn't mean it was necessarily detrimental to anything. It just means you're giving a kid more to deal with, while exposing it to less of any given language, so the kid's going to take a good bit longer to sort that out and get the amount of language input they need to progress.",
"When you're juggling 4 languages, you're likely not going to do a great job at getting the kid sufficient input in ",
" of them. When there's insufficient input you tend to see partial acquisition in some of the languages--but importantly not all the languages, the kid will ultimately learn the language of their community no matter what. This can happen even when only learning two languages.",
"If the parents had kept what they were doing, you would have still seen a difference around the time the kid entered school. Once children go out and be a part of the community, their dominant language becomes that of the community (if it wasn't before--sometimes it is, sometimes it isn't). So the kid would have made rapid progress in English (if she lives in the US, or wherever), while the progress of all the other languages she was acquiring would depend on whether she was continuing to get exposure to them through her family. If they stopped exposing her to the non-English languages, then she largely lost what she'd learned (called language attrition)."
] |
[
"What is generally used to cool down superconductive elements?"
] |
[
false
] |
Not just in labs, I'd like to know what is used outside of it because I figure that labs probably use some way that is really effective but also expensive, which is logical, but unuseable in other ways beacuse of the cost, so I'm wondering what it is that does the trick for the outside of the lab use. EDIT: Thanks, I've been wondering for some time so I asked here rather than browse and possibly end up with wrong info.
|
[
"It will almost always be liquid nitrogen or liquid helium. Liquid nitrogen is the cheapest cryogenic that can cool existing superconductors below the critical temperature. In fact, the development of \"high temperature\" superconductors that can operate above the boiling point of liquid nitrogen (77K) was a godsend. Before that you had to use liquid helium, which is much more expensive and more of a pain to use. Unfortunately for certain applications (e.g. MRIs) you are still stuck using liquid helium, which tends to drive up the cost.",
"Of course, it would be great if we could develop superconductors that could be cooled with water or which wouldn't require any cooling at all. That would drastically reduce the costs of superconductors and open up many new applications. Unfortunately, ",
"we are not quite there yet",
", and at this point it's not clear whether such materials may exist."
] |
[
"The basic principle is as follows: compressing things makes them hot, then they naturally cool to room temperature, decompressing them makes them hella cold. It can be useful to store them in their compressed state to save on cost and then to decompress at will.\nEdit: typo"
] |
[
"Liquid Helium (LHe) is typically cooled using a system which works much like your air conditioner or refrigerator. The Helium gas is first compressed increasing its temperature. It's then sent through a heat exchanger with some gas that is colder on one side to suck out the heat from your compressed gas and thus lower the temperature of the compressed gas. Then the gas is \"throttled\" essentially rapidly expanded and the temperature is now much lower than the initial temp. You can repeat this process now by putting the output into the cold side of the heat exchanger to get even lower temperatures on the output. A series of these processes will eventually lead to cold enough helium gas to condense to LHe. This can be collected in a dewar and transported to your lab to be used in any cryogenic applications.",
"Source: our LHe liquifier tech quit and me and another grad student had to operate our LHe system for the university for a few weeks before they got a new tech. It's an old system but this process is pretty standard for liquification of cryogens."
] |
[
"How come (-1)^(2/4) =/= (-1)^(1/2)?"
] |
[
false
] | null |
[
"Those are equal."
] |
[
"You're screwing up the brackets, if you want to do (-1)",
" you have to evaluate what's in the brackets first, if you want to calculate (-1",
" )",
" then you'll get 1."
] |
[
"No, (-1)",
" = i",
"(-1)",
" = 1"
] |
[
"How does the human brain determine whether sounds come from in front or behind?"
] |
[
false
] |
So most people would understand that the reason we have two ears is to determine whether sounds are coming from one side or the other through the time difference each ear receives the sound. How then, does the brain distinguish between sounds in front and behind if the ears are aligned symmetrically? Similarly, you can generally hear whether sounds come from above or below you.
|
[
"Adding onto this, when it comes to up/down and front/back localization, we are best at localizing high-frequency, complex sounds. By complex, I mean sounds with multiple frequency components like white noise, as opposed to something simple like a pure tone. ",
"The high frequency part comes from the shape of the outer ears (the outer fleshy part called the pinna). Since they are small relative to the wavelength of low-frequency sounds, they only scatter high-frequency sounds. Therefore, we are much better at making front-back distinctions for high-frequency sounds.",
"The complex part comes from the way we think the sounds are processed in the brain. Namely, there is a structure in the brainstem called the ",
"dorsal cochlear nucleus",
" that is thought to be involved. It has a cellular structure similar to the cerebellum, and is thought to perform a similar sort of pattern matching/subtraction process in order to determine changes in the sound texture noted above."
] |
[
"Adding onto this, when it comes to up/down and front/back localization, we are best at localizing high-frequency, complex sounds. By complex, I mean sounds with multiple frequency components like white noise, as opposed to something simple like a pure tone. ",
"The high frequency part comes from the shape of the outer ears (the outer fleshy part called the pinna). Since they are small relative to the wavelength of low-frequency sounds, they only scatter high-frequency sounds. Therefore, we are much better at making front-back distinctions for high-frequency sounds.",
"The complex part comes from the way we think the sounds are processed in the brain. Namely, there is a structure in the brainstem called the ",
"dorsal cochlear nucleus",
" that is thought to be involved. It has a cellular structure similar to the cerebellum, and is thought to perform a similar sort of pattern matching/subtraction process in order to determine changes in the sound texture noted above."
] |
[
"Interesting note: The ",
"facial discs",
" around owl eyes help to funnel sound to the ears. In some owls, ",
"these are offset",
" which allow them to do an even better job of telling exactly where a sound is coming from. This is how they are able to grab a mouse under snow without even seeing it."
] |
[
"How can animals smell things from a large distance?"
] |
[
false
] |
For example, there's a type of bear that can smell things from 18 miles away. If smells are essentially particles interacting with nerves in your nose, how are the animal's nerves interacting with particles that aren't even nearby? How can an animal smell something that isn't even there by it?
|
[
"The particles are interacting with the nose.",
"The 18 miles thing is pointing out that even after the smell has traveled for 18 miles and has been very dispersed through the air, the animal's nose can still detect the very small concentration of particles.",
"It may be more accurate to say that an animal can detect X particles per million air molecules. ",
"However, the range gives a more understandable metric. The range for example will change if there is wind."
] |
[
"So how are the particles traveling that fast? If a shark can smell blood a mile away, wouldn't it take a long time for the smell to get to the shark? Then by the time the shark reached the source of the smell, it'd be gone?"
] |
[
"that fast?",
"How fast? Do you have any idea how fast it actually spreads?",
"Then by the time the shark reached the source of the smell, it'd be gone?",
"I am sure it happens most of the time."
] |
[
"How fast can a wheel spin?"
] |
[
false
] |
Is there a limit to how fast a wheel can spin? Say if you put a skateboard down a large flat ramp held on a track would the wheels continue to build up speed indefinitely until the ramp bottomed out? A Bugatti Vayron can do 400kph the wheels must be spinning at a very large RPM. But what if the car was held in place and suspended from the ground, could the wheels spin at an even faster speed? Is there a limit of rotation that gravity will “allow”? Sorry for being thick :(
|
[
"There is a practical limit (in addition to that imposed by relativity). I once got ahold of one of those toy gyroscopes and wanted to know how much angular momentum I could give it and try to make it precess. I used an air compressor to blow across it and spin it up. I got it so fast that the centrifugal force exceeded it's tensile strength and it disintegrated in my hands. The practical limit is the strength of materials. This is true in flywheels and for jet turbines too. "
] |
[
"My dad used to work in a Industrial workshop that often used ",
"ball bearings",
". ",
"One day at lunch they decided to have some fun and took one of the compressors at the shop (and not one of those small ones you have in the garage, I'm talking a giant industrial motherfu***) and some bearings and went out to a large open space in the shop.",
"They held the bearings in the hand and spun it up just like you did and then dropped it to the floor and saw it go haywire.",
"They thought it was pretty darn fun but had a similar experience to what you had. Unfortunately metal ball bearings don't disintegrate. ",
"One of them opened up and it was like a massive hailshot cannon had gone of in the workshop. It sent 4 of the 6 of them to the hospital. xD "
] |
[
"There is a limit, but it's not because of gravity. No object can move faster than the speed of light relative to any other object. So, relative to the axis of the wheel, no part of the rim can exceed the speed of light. Predicting what you would actually observe during the process of spinning the wheel up from 0 RPM to whatever the limit is would involve some ",
" complicated physics, since a rotating reference frame is non inertial (inertial frames are described by Special Relativity, which is simple, non-inertial ones are described by General Relativity, which is many times harder). This system of a rotating disc is what is considered in the ",
"The Ehrenfest Paradox",
".",
"The above is only a thought experiment since in real life the RPM limit would be much lower since the stresses on the wheel would mean it would tear itself apart. From the Ehrenfest Paradox article, a real rotating disc will tear itself apart when the tangential velocity exceeds the speed of sound in whatever the disc is made of."
] |
[
"Do green and purple stars exist?"
] |
[
false
] |
According to the Hertzsprung-Russell diagram, stars can be blue, red, orange, yellow, and even white. But why aren’t green and violet (purple) in the diagram? Have green or purple stars ever been observed in the universe?
|
[
"Stars are pretty close to \"black body\" emitters. They emit a wide range of wavelengths, depending on temperature. The hotter the stellar atmosphere is, the shorter/bluer the peak wavelength is (although the definition of exactly where the peak is depends on if you're looking at frequency or wavelength).",
"When something heats up enough to glow red - like an oven - the peak wavelength is typically still in the infrared. It's just that the spread is wide enough that it some red is emitted at the upper end. As something gets up to 3000-6000 K, the peak is getting more into red/orange/yellow, but that means you're also getting yellow/green/blue mixed in as well. This mix means you go from red to orange to yellow to white. The green gets mixed in with all the other colours, to make yellow/white.",
"As the peak wavelength starts to go to blue and beyond, you're now emitting plenty of light of all colours. It emits more light on the blue/purple end than on the red/orange end, so the star looks blue-white, but it's never just emitting purple light so it never quite looks purple.",
"The wiki article on ",
"colour temperature",
" has some good illustrations and tables that are helpful."
] |
[
"So the interesting thing about red shift is that if you red shift a black body spectrum, it stays a black body spectrum! Basically you can make a blue 10,000 K star look like a red 3,000K star, but you can't make a blue star look green.",
"This actually makes it harder to find the distance or velocity of stars - you can't just look at the broad colour to figure out that the star must be far away because it's green, instead you have to look at the individual spectral lines that depend on specific chemical transitions.",
"As for flame colour - in theory, sure, but stars really are basically all hydrogen and helium. Also note that the Sun isn't a chemical fire - it's nuclear reactions in the core, but what we see at the surface is not \"fire\", but just really hot gas (a partial plasma even). Caesium ions might be a certain colour when reacting with air at <1000 K or whatever, but when they're surrounded by hydrogen and at 5000 K, I suspect you won't get the same result."
] |
[
"Ah interesting, so green and purple are incorporated into the white but because there are so many other colors also being emitted, it won't just show as a singular color?",
"Thank you so much for your response. This is so interesting!"
] |
[
"Is there anywhere i can download science papers?"
] |
[
false
] |
[deleted]
|
[
"Google scholar is where I look for my papers. Most of the older seminal papers are free."
] |
[
"Go to a library in a univ near you. If you cant find it via their computers, then most good univ libraries will have ILL services that will get the articles for you somehow. ",
"If you still can't find them and you don't want more than 1 paper every 2 weeks you can PM me, I can try."
] |
[
"arxiv.org has preprints of physics and related fields. The papers are generally new, however. ",
"Being a preprint server, a lot of stuff on there is cutting edge, but there's also a lot of crap. I wouldn't blindly trust anything from outside of mainstream US and Western European universities."
] |
[
"Why does a brain’s surface area matter so much?"
] |
[
false
] |
Wouldn’t a smooth brain have a higher internal volume than a wrinkled brain and a slightly higher neutron capacity?
|
[
"If volume were all that mattered, then yes, the More you could stuff into a skull the better. But organised connections are crucial to the ability to effectively process information. ",
"Evolutionarily speaking, cortex (outer surface of the brain) is a relatively recent innovation, so as a latecomer to the brain game, it had to grow ",
" everything that was there first, namely simpler (but definitely ",
" simple) structures responsible for not-as-abstract processing, and also all the wiring needed to communicate between all those structures. ",
"But the cortex is not a simple blob; it is a complex processor composed of several distinct hierarchical layers, with local processing going on in each layer, and communications to and from the neighbouring layers, that further process those results and feed them outward (or back inward) to modify the operation of the other layers, forming a sophisticated calculating circuit. ",
"The best way to store the amount of this computing equipment is to fold it up so that surface area is maximised compared to volume."
] |
[
"It's not only blood vessels and like. It's much more.",
"Cannot just say what's the function of the inside of the brain. There's a lot of structures \"inside\". There are parts that control emotions, memories, autonomic functions like blood pressure, and respiration. And this is a very very vrrh very small tiny summary of what the \"inside\" of the brain does.",
"It is just a really complex organ, a lot more than you think to just explain it short and easy"
] |
[
"Here",
" is a good overview of the various layers and types of cortex that our brain possesses. ",
"If you want to actually see many of the various known portions of the brain, ",
"Here",
" is an interactive tool that you can step through coronal slices and highlight structures (and even see an MRI with labels of the same coronal slice!). You can also see horizontal slices and even see a cervical section of the spinal cord on the same site."
] |
[
"If there WAS an air bubble in a needle that was injected into someone what damage would it cause and why?"
] |
[
false
] |
I know care is always taken to avoid having an air bubble in a needle by flicking it and squirting a little out, but with my basic understanding of the physics and medicine that might explain this I can't think of why this could cause any damage. What would it do?
|
[
"They can occlude blood vessels because (if the bubble is large enough) the surface tension of the bubble is too great for the blood to break through it, so it acts like a solid object and stops blood flow. The severity of the damage they can cause is dependent on their size and where in the vasculature they lodge but they can potentially cause heart attacks or cut off the blood supply to your brain.",
"However, bubbles entering the vasculature like in the way you're mentioning via syringe would be unlikely to cause any problem because the bubble of gas is small enough that it can pass through the vessels into the lungs and be dealt with. ",
"Wiki has quite a comprehensive and useful discussion about air emboli and the situations in which they are most harmful: ",
"http://en.wikipedia.org/wiki/Air_embolism"
] |
[
"Air bubbles are only really dangerous if injected directly into a blood vessel. For subcutaneous injections like insulin, the small amount of air that could possibly fill the syringe would just be absorbed by the body, from what I understand. I'm a nurse and I frequently give subcutaneous injections of a blood thinner called Lovenox and there is actually an air bubble included in the pre-filled syringes to ensure that all of the medication is administered. ",
"Even with air bubbles in IVs and the like, it takes a fairly large amount of air to cause problems. ",
"The concern with air in IV lines is an air or gas embolism. According to Wikipedia, injecting 100ml of air at rates of 100ml/sec or greater into the venous system had proven to be fatal. (A much smaller amount injected directly into the arterial system can cause death, but is less likely to happen because arterial access is less common than venous access like an IV.) In other words, with IV access, the risk of death from air embolism is more likely to result related to rapid IV infusion. ",
"http://www.ajol.info/index.php/sajr/article/viewFile/34461/6388"
] |
[
"I don't believe it happens very often at all. I've really only heard warnings about it, and I've never heard of it happening to any nurse I've met. An embolism could be made up of a blood clot, fat embolus, foreign object, or air embolus, among other things. I'm sure it probably happens with few side effects if it is minor. A serious embolism of any type can travel to the brain (causing stroke), the heart (causing a heart attack), or the lungs. All of these conditions, if serious enough, have signs and symptoms a doctor or nurse is trained to look for. Venous embolism is very rare due to the amount of air needed to cause a problem or cut off blood supply. "
] |
[
"Just saw this on /r/wtf. Can anyone tell me what the heck this scary little thing is?"
] |
[
false
] |
What is this thing? Are those really teeth? Can teeth even be that small? Credit for this find goes to suggested coming here with it, so I did just that.
|
[
"I'm no expert, but I would say it is a fish related to the ",
"Danionella dracula",
". Notice the same holes next to the eyes. Same family as the zebra fish."
] |
[
"Thanks! That does look very similar. :)"
] |
[
"You might want to try using ",
"google reverse image search",
". It's not a well known service but it's very handy."
] |
[
"Is the surface of a black hole perfectly flat or can it have geographical features like mountains?"
] |
[
false
] |
Are they perfect spheres due to the immense gravity? Side question: If you could somehow take a chunk/rock off a black hole that's the size of a fist, and somehow keep it secure on Earth without ramifications - what state of matter would it be and could it be a classifiable element?
|
[
"If our understanding of gravity is correct, black holes don't have a surface at all. The event horizon that people talk about is not a physical barrier, it's a mathematical point of no return. In the current understanding of gravity (though alternate theories exist) the mass of the black hole is concentrated into a single point with no volume, and consequently no surface, called the singularity. Regardless of the theory, certainly there is no longer any atomic structure at all, and it doesn't really make sense any more to talk about elements or composition. ",
"The event horizon ",
" a perfect sphere. If the black hole is spinning, there's a second mathematical border called the ",
", which is shaped more like an M&M than a sphere. This region is where the black hole spin is dragging space itself along for the ride, and it's actually ",
"possible to extract energy from the black hole's spin",
". That is, you could throw a baseball through the ergosphere, and when it came back to you it would be moving even faster than you threw it. ",
"The most compact objects with surfaces that we know about are neutron stars, which have envelopes and crusts of atomic species where the pressure is less, but which break down into a material that is even denser than the nucleus of an atom. Atoms certainly are not the structure of material deep inside of neutron stars.",
"Since neutron stars are the densest objects we know of with surfaces, we can answer your question in regards to them instead of black holes. The outer crust of a neutron star can have small \"mountains\" on it, and a quick back-of-the-envelope calculation shows that they can't be reasonably be larger than ~1 cm because the gravity is so strong that it will pull down anything higher than that (similar to how there's a maximum height for mountains on Earth or Mars or any other planet based on the strength of gravity at the surface). As the neutron star spins, these \"mountains\" create an asymmetric moment of inertia and should emit gravitational waves. Instruments like ",
"LIGO",
" are currently trying to detect these gravitational waves (in addition to much louder-but-shorter ones like merging neutron stars). "
] |
[
"So if an outside observer was to watch an object get sucked in by a black hole, it would appear to them to be happening very slowly?"
] |
[
"The thing with gravitational time dilation is that it depends on who is viewing it (i.e. the point of reference). Time only seems to slow down near the even horizon for somebody watching from further away. Time actually passes completely normal for an object that is there and thus it doesn't really take years to pass the event horizon. ",
"And if it's so...Therefore.. Yes. Black holes would have mountains. Matter \"frozen\" just outside the event horizon with topological features. :)",
"This would be correct but the event horizon isn't actually something physical that you can touch. It is the point where gravity bends space that much that light cannot escape (basically the point of no return). Things outside the event horizon would just be orbiting the black hole. Things inside as well but they won't ever be able to find back out (the actual reason for light not being able to escape is that there is no way out. Every direction leads towards the singularity).",
"The Singularity itself is actually the \"black hole\" (the source of the gravity) and that doesn't have any surface due to no volume. The event horizon (what we normally refer to as the black hole) is a perfect sphere but isn't made out of elements and thus has no surface with topological features."
] |
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