Pages

Saturday, December 14, 2019

How do brazil nut trees absorb so much selenium from the soil?

How do brazil nut trees absorb so much selenium from the soil?

How do brazil nut trees absorb so much selenium from the soil?

Posted: 13 Dec 2019 06:52 PM PST

Also how does Amazon rainforest soil have so much selenium?

submitted by /u/inquilinekea
[link] [comments]

What is the difference between a hypernova and a super luminous supernova?

Posted: 13 Dec 2019 03:17 PM PST

For some species of ant, like Army Ants, what determines whether they become a small worker, a large soldier, a male, or a queen? Is it random or do queen ants choose which profession ants will be when they lay the eggs?

Posted: 13 Dec 2019 05:12 PM PST

What is the correct equation for the spherical harmonics representation of geopotential? NGA and Wikipedia show different equations (sine vs. cosine of latitude).

Posted: 14 Dec 2019 06:03 AM PST

The EGM2008 model's page on NGA's site uses P(cos(lat)) (PDF warning).

The Wikipedia pages on Geoid and Geopotential model both use P(sin(lat)).

Which one is correct?

submitted by /u/wickedmath
[link] [comments]

Why is the range of the strong and weak nuclear interaction so small compared to the infinite ranges of the other two interactions?

Posted: 14 Dec 2019 02:02 AM PST

I've tried researching it a bit on my own, and it seems like it has something to do with the mass of the force carrying bosons, i just dont really understand how.

submitted by /u/KetchupStorm
[link] [comments]

How can a black hole have charge if photons can't escape from it?

Posted: 13 Dec 2019 08:53 AM PST

I asked before but had no takers, so figured I'd ask again. Photons are the force carriers of the EM force, of which charge is a part, right? So how can a BH have charge if this is the case? Unless somehow the charge is distributed on the surface of the BH, at or outside the EH, but that doesn't really make sense right?

submitted by /u/hvgotcodes
[link] [comments]

An orange is a pomelo x mandarin hybrid. I have a pomelo and I have a mandarin. Can I get them to make an orange, and how?

Posted: 13 Dec 2019 11:27 PM PST

Sodium chloride tastes salty to us. What would other sodium compounds taste like?

Posted: 13 Dec 2019 05:11 PM PST

Why is the Axiom of Infinity required in mathematics? What is lost or becomes possible if it is not assumed?

Posted: 13 Dec 2019 05:13 PM PST

As far as axioms go, it seems anti-intuitive to me. "infinity exists" seems not only NOT axiomatic, but impossible.

Like, the amount of numbers is infinite, but they don't exist the way physical reality exists. When you find infinite values in your calculations about the real world, either something is wrong with your theory or your measurement.

Is there something else that the Axiom of Infinity does that makes other normal math possible?

submitted by /u/FancyRedditAccount
[link] [comments]

Is the second tied to a constant or can it changed under more precise measurement?

Posted: 13 Dec 2019 08:05 PM PST

What is the current definition of a second?

How is it measured?

Could it change (be slightly faster or slower than our current second) under a more detailed measurement or have we made it a constant that cannot change?

submitted by /u/SHoDAN9000
[link] [comments]

If air pressure never changes in the cabin of a passenger airplane, why do water bottles flex and expand?

Posted: 13 Dec 2019 01:46 PM PST

What is the physiology behind tinnitus?

Posted: 13 Dec 2019 09:55 AM PST

Hi r/askscience! I can't seem to find any information on this. Does anyone know why tinnitus occurs, not just its causes but underlying mechanisms? Are there any known treatments out there?

Technical or nontechnical explanations totally ok. Thanks!

submitted by /u/derby_kid
[link] [comments]

Did Oumuamua and Borisov come from the same direction?

Posted: 13 Dec 2019 05:23 AM PST

Is there any known way to detect plate tectonics on an exoplanet?

Posted: 13 Dec 2019 08:07 AM PST

I am always amazed by what small clues can be picked up by radio telescopes, just been wondering if there is any way to detect this (even hypothetical).

submitted by /u/_Wahala_
[link] [comments]

What Gives Boiled Over,"Burnt" Water Its Smell?

Posted: 12 Dec 2019 08:54 PM PST

How does UV light kill bacteria?

Posted: 12 Dec 2019 05:53 PM PST

Has there ever been a mountain range taller than the modern day Himalaya / Karakoram? If so, how does science know it was so tall?

Posted: 12 Dec 2019 08:26 PM PST

How does turmeric react with alkaline substances?

Posted: 12 Dec 2019 09:22 PM PST

Today I learned, through a hilarious series of mishaps at my job, that turmeric will turn red when mixed with acid (as in, the Comet powder one might use to clean up when one has spilled a large amount of turmeric powder on a white tile floor). We didn't have time to hunt down some alkaline stuff to throw on it to see if it reacted differently, but I'm now super curious if turmeric acts as a pH tester on both ends of the scale, or just the acidic side.

submitted by /u/opentheyear
[link] [comments]
vào lúc No comments:

Friday, December 13, 2019

I have a theory: If there is an infinite amount of negative numbers and there is an infinite amount of positive numbers then the total amount of numbers would be odd. Because 0 is in the center. For every positive number there is an negative counterpart. Am I right? Can we prove this with math?

I have a theory: If there is an infinite amount of negative numbers and there is an infinite amount of positive numbers then the total amount of numbers would be odd. Because 0 is in the center. For every positive number there is an negative counterpart. Am I right? Can we prove this with math?

I have a theory: If there is an infinite amount of negative numbers and there is an infinite amount of positive numbers then the total amount of numbers would be odd. Because 0 is in the center. For every positive number there is an negative counterpart. Am I right? Can we prove this with math?

Posted: 12 Dec 2019 11:05 PM PST

Do microplastics accumulate in human tissue (particularly the kidneys, and possibly even brain)?

Posted: 13 Dec 2019 02:26 AM PST

When generating a bubble from the bottom of a fluid/gel filled chamber what defines the diameter of the bubble?

Posted: 13 Dec 2019 02:42 AM PST

I am experimenting with generating various sized bubbles within gel filled chambers. The input is at the base of the chamber and have tried with a couple of different sized apertures at the same pressure. So far this hasn't necessarily generated consistent sized bubbles.

If anyone has further reading I could look at, I'd appreciate a point in the correct direction.

submitted by /u/WorldLighter
[link] [comments]

How did Ole Christensen Rømer calculate the speed of light?

Posted: 12 Dec 2019 11:33 PM PST

I understand that he used the orbit of io but I seriously don't get how it's orbit or precived orbit can change based on distance alone since the sun is constantly emitting light and all orbits are constant.

I could see how it could be calculated if the sun sent light in pulses, what am I missing?

submitted by /u/AntonioOSalazar
[link] [comments]

Can mirrors amplify light?

Posted: 12 Dec 2019 07:49 PM PST

Also could we use use a giant mirror to capture light from the sun, then use a bunch of mirrors in a certain way to amplify the light, and then just shine that light at a big solar panel?

submitted by /u/thelastdose
[link] [comments]

Are classical mechanics (ie. conservation of momentum) sufficient to describe the collision of a neutron with a proton?

Posted: 13 Dec 2019 01:53 AM PST

I was thinking about how classical mechanics usually can't be used to describe the subatomic world, but was wondering if there were any exceptions, like the one i listed for example.

submitted by /u/KetchupStorm
[link] [comments]

What was the first commercial device to use strong encryption?

Posted: 12 Dec 2019 07:33 AM PST

Was it the AT&T TSD 3600? And is that why the NSA was so panicky in implementing the clipper chip into this device? Before this device were all commercial telecommunications open to being wire tapped by law enforcement agencies?

Sorry for all the questions, just trying to understand.

Thanks in advance.

submitted by /u/G0nad_
[link] [comments]

I've always wondered, is it possible to look in a reflective surface and see someone but that someone can't see you in the same reflection?

Posted: 12 Dec 2019 09:50 AM PST

I'm not an expert but I know that in a mirror for example reflection is in a straight angle. Or something like that. I'm putting this question because every time I take the train to go home late at night, the window it's a bit reflective and I can see people behind me. And the question is, can they see me looking at them through the same window?

submitted by /u/NicuManevra
[link] [comments]

How are file copy or transfer functions on computers ensured to be perfect to the original file?

Posted: 12 Dec 2019 09:30 AM PST

To elaborate, when a file is copied on a computer from one place to another (USB to Internal, or the internet), are the files copied perfectly and if so, how? There are so many components made by many different manufacturers, how is the 'chain of custody' ensured, and by what? The internet brings the abstraction of all the components to a way higher level, how are good transfers ensured there?

submitted by /u/GluteusMax
[link] [comments]

Why is silver a better conductor than gold?

Posted: 12 Dec 2019 10:02 AM PST

So I know for a fact that silver is better than gold at conducting but it isnt sitting right in my head as my current understanding is the gold should conduct more as It has more free electrons that can move and carry charge

submitted by /u/WAR-267
[link] [comments]

Where does the oceanic crust created at the Mid-Antlantic Ridge subduct?

Posted: 12 Dec 2019 09:59 AM PST

My basic understanding of plate tectonics says that oceanic crust is 'created' at the mid-oceanic ridges and then subducts under the continental crusts. But looking into things earlier I noticed that there doesn't seem to be a subduction zone along the continental landmasses either side of the Mid-Antlantic Ridge. So where does the oceanic crust go?

submitted by /u/ManualPancake
[link] [comments]

Why are bound-bound cross sections greater than bound-free cross sections, and bound-free cross sections greater than the Thomson cross section (free-free)?

Posted: 12 Dec 2019 11:52 AM PST

I get the math but I don't understand physically why bb > bf > ff when it comes to cross sections. It's not like 3 > 2 either, difference is 27 or so orders of magnitude between bb and ff.

submitted by /u/olafwillocx
[link] [comments]

Is eczema an allergy or autoimmune disorder?

Posted: 11 Dec 2019 05:05 PM PST

Or is it something else? What causes it?

submitted by /u/mcjc1997
[link] [comments]
vào lúc No comments:

Thursday, December 12, 2019

How long does it take for a subverting tectonic plate to be totally recycled?

How long does it take for a subverting tectonic plate to be totally recycled?

How long does it take for a subverting tectonic plate to be totally recycled?

Posted: 12 Dec 2019 02:39 AM PST

How long until a tectonic plate completes a full cycle? From when the newest crust emerges on one end all the way to being subverted on the other. It would obviously be different for each plate, so feel free to give specific example(s).

submitted by /u/Brandwins
[link] [comments]

Is the International Space Station's orbit altered by the weight of new supply deliveries?

Posted: 11 Dec 2019 10:55 PM PST

I read that the ISS receives several tons of supplies at each delivery. Does this change the momentum or overall energy, or otherwise do anything to the object's orbit, and does its path need to be adjusted or boosted somehow to compensate for the additional mass?

submitted by /u/OnCommence17
[link] [comments]

What exactly makes something feel itchy?

Posted: 11 Dec 2019 04:19 PM PST

What causes something to feel itchy and what does an itch mean?

submitted by /u/joshuapjacob
[link] [comments]

Are Blue Whales actually the biggest ever?

Posted: 11 Dec 2019 08:38 PM PST

We are taught that blue whales are the largest mammals/vertebrates to ever exist. Isn't this unlikely considering our lack of seabed fossil evidence?

submitted by /u/conanmagnuson
[link] [comments]

Does candle wax have a "wax memory" (noticeable viseoelastic creep)?

Posted: 11 Dec 2019 05:53 PM PST

Today I was asked if I was aware that I should let a candle completely burn to the edge of the glass jar the first time to maintain an even burn throughout the remainder of the candles. Up until then I hardly noticed my habit of burning a candle with adequate time to melt the full width of the wax. Basically, I liked the candle more visually with minimal wasted wax clinging to the sides of a container so whenever I'd burn a candle I would attempt to burn the candle to the edge of the glass. I had never really thought of it any further that that.

They explained to me that he was always told it was due to the wax being easier to melt after it had already been melted once. I accepted this and asked if we could find out the name of types of matter with this property, after all this must have been an observed phenomena before and would likely share this trait with other forms of matter. We begun some routine searches of differing combinations of words like; wax, candle, melt, remelt. They were a bit strange at first, mostly directing us to candle sellers and DIY candle instructions detailing the importance of the first burn and the original pouring temperature and leading us to ideas like wax memory.

After further refinements to our searches we began ask more questions than we would find answers. With most of our searches turning up less than scientific sources (though not necessarily incorrect or science-skeptic) I started to get really curious about the physics behind some of these clearly well known patterns in candle burning. It was clear that correctly burning a candle could prevent excessive edge wax or create a desired tunnel in a candle without a jar. It also became resoundingly clear that environment, wax material, wick size, and quite a few other elements were at play and were almost as important as length of burn time and the first few burns.

It seems to me that after the candle was burned the first time, if it was inadequate to complete the burn, a "tunnel" could be formed creating a buffer then preventing radiant heat from reaching the edges of the wax. This would obviously reduce heat on the glass which could then radiate the lower heat to the cool air around it further reducing the potential heating of the dreaded edge wax. The creation of a tunnel deep enough to block radiant heat would naturally dig itself deeper as it's own walls prevented heat from escaping and allowing newly melted wax to fall below instead of heating outwardly. This might be desired in candles without containers, but a smaller wick could achieve that as well.

This might stand in contrast to there being a true "memory" present in the matter comprising many candle waxes. The memory idea seems more likely to be observational bias on the parts of people who have are burning candles in consistent ways leading to certain patterns in the wax shape. Those patterns are often self encouraging which explains why it's easy to intentionally mold a new candle into a desired state, so easy to accidentally misshape a candle early on, and so tough to reverse the trend once begun.

After a few hours of diving down this rabbit hole for no other reason than candles are neat, I am honestly left with a few questions. Is there actually any truth to the first burn is the most important line of reasoning? Or is it just a result of successive similar inefficient or efficient burns that creates tunnels and edge wax, leading to a nearly irreversible state after a few repeated similar burns? Something about non-viseoelastic creep I can almost understand, and why am I not studying for my final next week instead?

submitted by /u/Wtantis
[link] [comments]

What exactly is momentum and how does it differ from kinetic energy?

Posted: 11 Dec 2019 11:35 PM PST

I've always been confused as to why Momentum = mass x velocity, but KE= 1/2 x mv2 because to me they seem to describe pretty much the same thing. What's the reason for this and what exactly is momentum and KE?

submitted by /u/EtecaEteca
[link] [comments]

Is there a good way to quantify how "random" a given method of shuffling cards is?

Posted: 11 Dec 2019 12:45 PM PST

I used to shuffle cards the normal way, split it in half and then recombine, but then I realized: the topmost cards in the deck still stay mostly on top, and the bottommost cards still stay mostly on the bottom, so you're not really getting a completely random distribution, no matter how many times you shuffle the deck.

What I do now is split the deck IN THREE, like, say, A, B, and C, with B (the middle portion) being about as big as A and C combined... and then I take portions A and C and stick them together BACKWARDS, so now we have a deck portion CA and a deck portion B, and then I shuffle CA and B together like you would any two halves of a deck.

Is there any even better simple way to REALLY randomize the order of cards in my deck? Is there any way to quantify how random a shuffling method is?

Like, I was thinking, how accurately could you guess the position of any card in a deck, say, three shuffles down? With the traditional cut-in-half-and-interpolate method, you don't really have a good chance at guessing any of the middle cards' future positions, but with the top and bottom few cards you can basically predict they'll stay approximately where they are, moving a bit deeper into the deck as you go along. With MY method, you'd have much more trouble guessing even the outliers!

could anybody point me in the right direction to learn any more about this topic or anything? I know a few mathematicians but none of us are on speaking terms rn so I'd love some help from you sweet people

submitted by /u/biggerbluejay
[link] [comments]

At this point in time, are we able to simulate nuclear bomb tests by a computer with similar accuracy to a real life test? If so, are these test done as frequently as in the Cold War?

Posted: 11 Dec 2019 11:09 PM PST

Why do liver cells have varied cell cycles and is this why you can do a partial liver transplant?

Posted: 11 Dec 2019 07:30 PM PST

I was doing some research for an intro cell bio class and was looking into the cell cycle of a hepatocyte and while researching I found that the cell cycle usually takes roughly a year to go through it's cycle but could take up to 22 hours if need be. Why does this particular type of cell do this, do other cells in the body have this same variability in reproduction of the cell (without being cancer) and is this why you can do a partial liver transplant and it will grow into a full liver?

submitted by /u/jacknolan329
[link] [comments]

What is the difference between a 'perforating' gunshot wound and a 'penetrating' gunshot wound?

Posted: 11 Dec 2019 06:24 PM PST

Forensic pathology is an interest of mine, and I've seen dozens of autopsy reports and death certificates, but one thing I never got a clear answer on was the title question.

An example is Kurt Cobain. Washington State autopsy reports are not public record, but I've seen the death certificate. "Cause of death: contact perforating shotgun wound to head (mouth)"

By all indications, the man who discovered his body thought it was a mannequin until he saw blood leading from the ear into a pool under the upper body. Kurt used light gauge ammunition. "Birdshot", as they call it. Generally not enough to blow the top of someone's head off, like 12 gauge buckshot probably would.

Does that mean a 'perforating' wound is one that doesn't exit the body, and a 'penetrating' wound is one that goes through and through, leaving an exit wound?

I apologise for the ranting post, but for close to 20 years now, Kurt Cobain's autopsy report has been my "white whale", and it's personal to me. I thought I'd ask people more knowledgeable than myself to fill in some blanks I'll probably never get the chance to know directly.

Thanks.

submitted by /u/chaosperfect
[link] [comments]

In fluorescence the emission wavelength is lower energy than the excitation wavelength. Where does the extra energy go?

Posted: 11 Dec 2019 01:15 PM PST

Does it just turn into kinetic energy?

submitted by /u/fleemfleemfleemfleem
[link] [comments]

Do scientists compensate for the movement of Earth and the Milky Way when they measure the red and blue shift of other objects in the universe? How can they know that the measurements are correct, if the reference point is also moving?

Posted: 11 Dec 2019 07:11 AM PST

How did early chemists determine that chemical elements were chemically indivisible, and their respective atomic weights? How did they determine that common stable substances were not elements?

Posted: 11 Dec 2019 04:50 AM PST

What prevents full on recovery of limb function?

Posted: 11 Dec 2019 05:34 AM PST

Let's say a soldier is hit by shrapnel. A dozen pieces cut through his arm, cutting tendons, blood vessels, and fracturing bones. He is airlifted back and the arm is saved. Yet, his arm is slower, weaker, and sometimes throbs painfully. Why?

submitted by /u/Accelerator231
[link] [comments]

Are there any atoms that can form either cations or anions depending on the molecule?

Posted: 11 Dec 2019 06:38 AM PST

Like for example can O be either O2- or O2+? Or can all atoms form either only cations or anions?

submitted by /u/submarinekid
[link] [comments]
vào lúc No comments:

Wednesday, December 11, 2019

What effects would a projectile on Earth fired with near the speed of light cause?

What effects would a projectile on Earth fired with near the speed of light cause?

What effects would a projectile on Earth fired with near the speed of light cause?

Posted: 11 Dec 2019 01:20 AM PST

If we were able to accelerate a projectile (say the size and weight of an airsoft ball or a sand of grain) with a railgun (or really, by any other means, but on Earth), what kind of effects would it have? Would if be an effective weapon? Would it heat up to the atmosphere too much? Would it bend space-time to a noticeable state? How much of a destructive force would it cause on impact? Is it even possible in theory, if enough energy could be harnessed?

submitted by /u/Csillagfityma
[link] [comments]

An alternate way of reaching the speed of light?

Posted: 11 Dec 2019 01:05 AM PST

So if your sitting on a giant clock that's hand is spinning clockwise, the further out you sit on the hand the faster you spin around the centre So what if the clock hand was 1000 miles long, and at the centre it was spinning 200mph, sitting at the end of the clock hand you would be going at least faster than the speed of sound Is there a length so great and base speed so high that the end of the clock hand would be able to go faster than the speed of light ?

Edit: thanks for the great response guys! I know so much more now

submitted by /u/hazbot2003
[link] [comments]

How did Mendeleev know the properties of the elements before they were measured by using his table?

Posted: 10 Dec 2019 05:06 PM PST

My teacher was going over chemical equations in class but never went in depth of how mendelev predicted the properties of missing elements?

submitted by /u/unachicanomas
[link] [comments]

Ask Anything Wednesday - Physics, Astronomy, Earth and Planetary Science

Posted: 11 Dec 2019 07:08 AM PST

Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Physics, Astronomy, Earth and Planetary Science

Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical /r/AskScience 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...".

Asking Questions:

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 /r/AskScienceDiscussion , 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.

Answering Questions:

Please only answer a posted question if you are an expert in the field. The full guidelines for posting responses in AskScience can be found here. 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 /r/AskScience.

If you would like to become a member of the AskScience panel, please refer to the information provided here.

Past AskAnythingWednesday posts can be found here.

Ask away!

submitted by /u/AutoModerator
[link] [comments]

Do water filters such as brita remove minerals such as calcium and magnesium from water?

Posted: 11 Dec 2019 03:15 AM PST

I'm wondering specifically due to its ion exchange function and a vendor told me they can function specifically as a water softener, is this true?

submitted by /u/Rajeshrocks311
[link] [comments]

Where did all of the oxygen from the Carboniferous period go?

Posted: 10 Dec 2019 08:40 PM PST

I was reading about the history of oxygen and realized there was an increase once photosynthesis developed. It peaked during the Carboniferous period, making insects very large (presumably), but what happened after that? Where did the oxygen go?

submitted by /u/kipknightly
[link] [comments]

Do other mammals get "morning sickness" during pregnancy?

Posted: 10 Dec 2019 08:32 PM PST

I have never seen or heard of any other type of animal throwing up more often while pregnant. Granted, I am not around many other animals other than dogs and cats, so my personal experience means little in the matter. That's why I'm here, I'm just wondering, as my wife suffered through HG during both of her pregnancies and it was hell for her, so I was curious if other animals could suffer from something similar.

submitted by /u/Ray745
[link] [comments]

Does higher octane/premium gas actually cost more to produce? What makes it so much more expensive?

Posted: 10 Dec 2019 05:25 PM PST

I've always been told the "premium" label on higher octane gas is a bit disingenuous. There's nothing really "premium" about it beyond the higher octane rating.

But why does that make it so much more expensive? Because less of it is produced? Is there some additive or chemical that costs more? Why is it sometimes >35% more expensive? That seems pretty crazy.

submitted by /u/PineappleDelivery
[link] [comments]

What percentage of people are lesbian, gay, bisexual?

Posted: 10 Dec 2019 02:55 PM PST

I am fully aware this is a controversial topic in society, but what does science know about it at the moment?

submitted by /u/patacsiipse
[link] [comments]

Why do quantum states have to live in complete metric spaces?

Posted: 10 Dec 2019 04:51 PM PST

The Hilbert space is used in quantum mechanics to define the space where the operators of a given system will act on. And, the quantum state of a system is an element of the Hilbert space.

I understand that a Hilbert space is a vector space equipped with an inner product, which is also complete regarding the metric induced by the norm, i.e, it is also a complete metric space. I understand that the inner product is useful to compute the probability amplitudes. However, it's not clear to me why we also need the space to be a complete metric space.

Is it because the Schrödinger equation describes unitary operators, which act on a complex space C^n. And C^n is automatically a complete metric space if we choose the standard inner product in C^n? In other words, it would be a consequence of choosing the inner product as the standard one?

Thank you in advance!

submitted by /u/mi_pope
[link] [comments]

Does tension change the properties of ice?

Posted: 10 Dec 2019 04:08 PM PST

Under compression (which causes increased pressure?), ice has a lower melting temperature. At low pressures, water freezes at higher temperatures. Does placing tension on a rod of ice change these properties?

submitted by /u/0Bradda
[link] [comments]

Why can foxes eat raw chicken while we cant, and how did we eat meat before we could cook it?

Posted: 10 Dec 2019 08:16 AM PST

the title says it all

submitted by /u/luer1001
[link] [comments]

To what distance are humans able to currently monitor any objects moving towards earth?

Posted: 10 Dec 2019 06:48 AM PST

What is the relation of Entropy and Diversity as effective numbers?

Posted: 10 Dec 2019 10:48 AM PST

This is a very general question. Diversity numbers have different orders, with D0 being species richness, D1 being Diversity on the order of 1 and equivalent to the inverse of Shannon's Diversity Index. The general formula for species diversity is defined by Hill. However there also exists Rényi entropy, Tsallis entropy, and even the q-Gaussian.

1) How are these metrics related?

I understand that Diversity is an effective number. So if Diversity is 15, the ecosystem can effectively support 15 species.

2) How do I determine which order of diversity should I choose?

On this graph from this website, you can clearly see that the ecosystem has 500 species, but the diversity(1) is equal to 420, diversity(2) is equal to 375, diversity(3) is equal to 350. (The author made a mistake and mislabeled Simpson's index as D3 when it should be Diversity(2). This looks like a clustering algorithm, so how should I choose the correct order of diversity?

submitted by /u/iseahound
[link] [comments]

If an infinite Taylor series can define trigonometric functions, and Euler series are constructed using trigonometric functions as their terms, why are there functions which can be described by Fourier series but not Taylor series?

Posted: 10 Dec 2019 06:16 AM PST

Take for example the Weierstrauss function, a kind of one-dimensional fractal which is continuous everywhere but differentiable nowhere. It can be described using a Fourier series, a sum of cosine terms, and not by a Taylor series (because those require the nth order derivative an infinite number of times and you cannot differentiate the function.) My question is, once you have a Fourier series built out of cosines, can't you just break out a Taylor series to define each individual cosine term? Granted, this would be an infinite summation of infinite summations. Is this just not possible?

Reposting this at a reasonable hour in the hopes it'll get answered.

submitted by /u/second_to_fun
[link] [comments]

Why does single nucleotide polymorphism on the TAS2R38 gene cause a bitter taste in those who have the mutated allele?

Posted: 10 Dec 2019 06:28 AM PST
vào lúc No comments:
Subscribe to: Posts (Atom)