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Thursday, July 28, 2016

AskScience AMA Series: Hi! I'm Dr. Olwen Grace, a researcher at the Royal Botanic Gardens, Kew in London. I study the world's succulent plants and what evolution can tell us about the useful properties of wonder-plants like Aloe vera. AMA!

AskScience AMA Series: Hi! I'm Dr. Olwen Grace, a researcher at the Royal Botanic Gardens, Kew in London. I study the world's succulent plants and what evolution can tell us about the useful properties of wonder-plants like Aloe vera. AMA!


AskScience AMA Series: Hi! I'm Dr. Olwen Grace, a researcher at the Royal Botanic Gardens, Kew in London. I study the world's succulent plants and what evolution can tell us about the useful properties of wonder-plants like Aloe vera. AMA!

Posted: 28 Jul 2016 05:00 AM PDT

Hi, I'm Dr. Olwen Grace, a researcher specialising in the evolution of succulent plants (plants that store water) at the Royal Botanic Gardens, Kew in London. I lead the team that confirmed the origins of Aloe vera on the Arabian Peninsula - a longstanding botanical mystery - using genome sequencing techniques. We published the findings in an Open Access paper in BMC Evolutionary Biology and you can read an article about the story in New Scientist.

I'm currently working to solve the second Aloe vera mystery: why has this species reached wonder-plant status, supporting a global trade, and not the 500 or so other closely related species in the genus Aloe?

The research goes beyond solving a botanical enigma. If we can understand how Aloe vera differs from its closest relatives (or not) then we can highlight other species of Aloe, growing throughout Africa, that might have similar potential.

I'm fascinated by the ways in which adaptations in the plant kingdom are valuable to people, and how we can harness nature's solutions to problems facing humanity today.

I'll be on from 5-7 PM UTC (12-2 PM ET) and look forward to your questions!

submitted by /u/AskScienceModerator
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Does the temperature of water affect how it is absorbed by a towel?

Posted: 27 Jul 2016 09:16 PM PDT

Are there more units beyond acceleration?

Posted: 28 Jul 2016 05:40 AM PDT

Displacement: m Velocity: m/s Acceleration: m/s2 ...?

submitted by /u/scottylime
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How statistically random are the answer distributions on standardized tests?

Posted: 27 Jul 2016 08:48 PM PDT

This may be an impossible question to answer but I'll try to explain the scenario. Multiple choice exam with answers A-D. 300 questions. Supposedly there were 10 different orderings of the questions/answers. After working through the test and for 50 questions you notice 25 of my answers have been A, then on question 51, you have it narrowed down to A and D, is it a smart move to choose D if its a total tossup. I would think so assuming they are random but are standardized tests really random? Not sure I'm asking this in a good way but I tried

submitted by /u/r8v10
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How is a sonic boom sound created?

Posted: 28 Jul 2016 06:19 AM PDT

So when a jet breaks the sound barrier there is a loud boom sound. How is this formed and why?

submitted by /u/coolylame
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If we fired every single nucleur weapon we have on the planet into the sun simultaneously, would anything happen to the Sun at all?

Posted: 28 Jul 2016 05:53 AM PDT

What do scientists propose as an answer to the problem of global warming?

Posted: 27 Jul 2016 04:43 PM PDT

Beyond cutting emissions, what solutions are there for reversing or mitigating the environmental changes & damage?

I would think something along the lines of a massive carbon sink would be self-defeating, as it would ultimately repeat the situation we are in, with vast carbon deposits available for reprocessing into fuel.

submitted by /u/Psyladine
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How does "burning fat" physically work?

Posted: 27 Jul 2016 04:11 PM PDT

Like, do the fat molecules actually just fall off your body and into the environment? Meaning that gym floors must be filled with people's invisible ex-fat (I thought of this question while working out)?

submitted by /u/My_Genuine_Questions
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Can someone spot where my misconception of graphene orbitals is coming from?

Posted: 28 Jul 2016 04:10 AM PDT

To be honest, Im not sure how should I phrase my question, I have a situation which I simply cant stomach, its about graphene. Feel free to correct my as I go a long, my misconception might be hidden somewhere in there.

Carbon has an electron configuration of 1s2 2s2 2p2. Meaning the first shell/level has 1 orbital that has 2 electrons in it.

The second shell/level has 2 sub-orbitals, the first (s) holds 2 electrons, and the second (p) (which can be divided in to x,y,z) holds 2 electrons also (one in x and one in y)

Graphene has 3 sigma bonds and 1 pi. The 3d visualizations show the orbitals like (https://postimg.org/image/mfcryoi1d/). What I dont understand are the shapes of the orbitals. Is there any geometrical/vector explanationon how one the 3 s like (round ish) ones are formed?

The way I try to picture this is, one round (2s) orbital and two eight shaped (2p) (x and y) orbitals should give birth to 3 of 'those' orbitals, leaving the z intact. But.. it simply doesn't work in my head... HELP

submitted by /u/Milchy
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How do firefighters fly helicopters over fires?

Posted: 27 Jul 2016 04:45 PM PDT

Fires can cause some crazy updrafts so how do the pilots manage to get above them to drop a retardant down?

submitted by /u/atomiccrouton
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Does fire cause drag?

Posted: 27 Jul 2016 09:08 AM PDT

If I prepared two arrows identically and lit one on fire, and not the other, then fired them from the same bow at the same inclination, would the unlit arrow travel further? I imagine that the hot air flowing overthrow rest of the arrow length and fletching would have some effect, but is it significant and positive or negative? Or is there any other effect caused by the flames themselves - laminar vs turbulent flow or do the flames add to the effective surface area of the arrow as it penetrates the air?

Edit: I should clarify that I'm not asking specifically about an arrow, but any two identical arbitrary objects moving through the air, one flaming and the other not. And consider that the flames themselves are significant relative to the size/mass of the object. Would a race car with a huge engine fire coming out the back experience more drag than not - would a flaming piece of debris falling from the sky fall slower than an identical piece that was not alight?

submitted by /u/CheapBastardSD
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If you took 0.333... and removed the '0.' would 333... be an integer?

Posted: 28 Jul 2016 06:28 AM PDT

If honeybees are non-native to North America, won't the original (or other) pollinators flourish and fill in the gaps left behind by the decreasing population?

Posted: 27 Jul 2016 02:28 PM PDT

I'm assuming the original pollinators weren't completely displaced by the invasive european honeybee, but even then the other pollinators' populations will expand without competition from those bees. I haven't been able to find any articles addressing this whenever bee population articles come up.

submitted by /u/spondylo
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When did psychoanalysis and other Freudian theories start falling out of favor for treating mental health issues, and start getting replaced by cognitive behavioral therapy?

Posted: 27 Jul 2016 03:28 PM PDT

Back in 2012, the BBC did an exposé on psychoanalysis being a preferred method of treating autism by French doctors. After some digging, I found that mental health treatment in France often uses psychoanalysis and other Freudian tactics, when other countries had shifted to CBT-related methods long since.

I just want to know when in history that change began, when the psychological and psychiatric communities began moving away from Freudian tactics and started embracing CBT more.

submitted by /u/ssaaabbbccc1234
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How do police radars measure your speed?

Posted: 28 Jul 2016 04:49 AM PDT

If I'm not mistaken it deals with red/blue shifted light but I don't know for sure as to how it works.

submitted by /u/The_Red_Spectre
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What causes us to feel heartache? Are there any evolutionary advantages to the pain we go through?

Posted: 27 Jul 2016 04:14 PM PDT

How does electromagnetism work with conservation of momentum? Specific scenario in body.

Posted: 28 Jul 2016 04:32 AM PDT

Let's say I'm in my spaceship at rest relative to a large ferrous asteroid currently 10 light-seconds away. At time t=0 I activate my enormously powerful electromagnet. What starts moving at what time, and how is momentum conserved in all reference frames?

submitted by /u/C_A_L
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Whats the difference between h.264 and x265?

Posted: 27 Jul 2016 03:51 PM PDT

I've seen massive 1gb 720p or FHD videos compressed down to less than 2-300mb using x265. How is this possible and do you lose any quality? Are there any downsides?

submitted by /u/Fortune_Cat
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What causes tube memory?

Posted: 27 Jul 2016 01:34 PM PDT

When I was an Artillery officer I never had an instructor be able to explain what causes it. It occurs even when the gun has not been fired in a day, so not heat related Here is the definition: From FM 6-40 chapter 3 https://www.fas.org/man/dod-101/sys/land/docs/fm6-40-ch3.htm (a) Tube memory is a physical phenomenon of the cannon tube tending to react to the firing stress in the same manner for each round, even after changing charges. It seems to "remember" the muzzle velocity of the last charge fired. For example, if a fire mission with charge 6 M4A2 is followed by a fire mission with charge 4 M4A2, the muzzle velocity of the first round of charge 4 may be unpredictably higher. The inverse is also true.

submitted by /u/loki143
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If a pregnant woman eats very little, will the baby take nutrients from the mother's muscles or fat stores? Or will the baby be malnurished?

Posted: 27 Jul 2016 09:17 AM PDT

And the other way around. If the mother eats a lot will the baby be born larger?

submitted by /u/skeeetball
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I notice sometimes that when I'm in my car and in an area with spotty radio reception, touching certain areas of the car (mainly on and around the receiver unit) significantly improves the signal. Why does this happen?

Posted: 27 Jul 2016 11:51 AM PDT

How much and what kind of light causes colors to fade on books, posters, comics etc?

Posted: 27 Jul 2016 03:55 PM PDT

I have a large collection of comic books and other books and I'm a bit paranoid about exposing them to too much light, especially sunlight.

Out on the street and in some shop windows, we can see old posters or books that have been there for a long time and the colors are faded. Some books that I've purchased second hand also have fading on the spine which was obviously exposed whereas the cover was not.

I keep most of my books on shelves that are never directly exposed to sunlight but I often keep the curtains open so the reflected natural light gets in. My home has a mix of incandescent and fluorescent lighting.

I'd like to keep my books as pristine looking as possible so any info about what to do to avoid color fading would be great.

submitted by /u/BlueHarvestJ
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Does the big Gas planets have a rocky or solid core?

Posted: 27 Jul 2016 02:38 PM PDT

I'm guessing that since the gas planets in our solar system have magnetic fields they have molten cores, but are these cores covered by something solid like rock? Are the gas planets in fact just rocky planets with huge atmospheres? What happens with all the asteroids they attract? Do they all completely burn up or does some reach a solid bottum? When these planets formed didn't they also attract rocks and solid materials besides gas? If yes - what happened to it?

submitted by /u/Absjalon
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Wednesday, July 27, 2016

My roommate washes his dishes immediately after eating with only water. How clean is the dish compared to using soap after letting the food set for a while?

My roommate washes his dishes immediately after eating with only water. How clean is the dish compared to using soap after letting the food set for a while?


My roommate washes his dishes immediately after eating with only water. How clean is the dish compared to using soap after letting the food set for a while?

Posted: 26 Jul 2016 08:40 PM PDT

Edit: Forgot to mention that it is hot water

submitted by /u/secretionstation
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How worried should we be about the Clathrate Gun?

Posted: 27 Jul 2016 07:08 AM PDT

Clathrate gun

Year after year is becoming hotter than the next.

Scientists are being 'caught off-guard' by record temperatures.

Natalia Shakhova says we may have only DECADES before things get really bad.

This thread yesterday really scared the shit out of me. Are things really this dire? Could the human race be gone in less than 100 years?

submitted by /u/claxius
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What keeps the protons in the nucleus of a atom from repelling each other?

Posted: 27 Jul 2016 03:39 AM PDT

In chemistry, we were taught it has do do with the quarks and gluons, but didn't get much deeper than that. How exactly do these quarks and gluons peek the protons together?

submitted by /u/Dylanamin
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How much of an issue to sattlelites/ISS/rockets is man-made space junk? Is there anything really we can do to "clean up" orbiting trash?

Posted: 26 Jul 2016 08:17 PM PDT

Can a blind person experience photic sneeze reflex?

Posted: 26 Jul 2016 08:14 PM PDT

Why does Alcohol relieve pain?

Posted: 26 Jul 2016 07:40 PM PDT

Obviously "because it gets you drunk", but what specifically about ethanol gives it analgesic effects at the level of the the CNS/brain?

submitted by /u/Bouttoknockitout
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Why will subtracting a number by its inverse always give an answer divisible by 9?

Posted: 27 Jul 2016 05:49 AM PDT

724-247=477, 21-12=9 and so on

submitted by /u/gpm21
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Why did people think that clones would age faster than normal?

Posted: 26 Jul 2016 06:50 PM PDT

I saw the story about Dolly the sheep's clones aging well, and wondered where the theory the clones aged at an accelerated rate came from? Is there any scientific evidence to back it up?

submitted by /u/Albino_Moose
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If the arctic habitat for polar bears is disappearing, why don't we relocate them to the antarctic?

Posted: 26 Jul 2016 08:00 PM PDT

Are there specific conditions that would unsurvivable to them in the south? Or would it just be too disruptive to the antarctic ecosystem?

submitted by /u/soyouwannabeapanda
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What is the path of electrical current flowing in this gif? Why does it burn the wood in this pattern?

Posted: 26 Jul 2016 07:28 PM PDT

Apologies if this has been asked before but I did not see anything when I searched.

This gif was recently posted in /r/gifs.

As you can see, a battery is supplying current to a piece of wood, and the electricity is burning the wood. The gif was described as the current "finding" the path of least resistance. It's been a while since I've taken an electronics course, but I am familiar enough with the basics of circuits.

However, and this may not have been the intention, it seemed like the post was suggesting that the slow burning in the gif was the slow movement of current. This seems incorrect to me since current would start flowing when the circuit was closed, and current would have to be flowing first in order for the wood to burn.

But what is the path of the current? Why does the wood burn with this pattern?

Some people tried to address these questions in the original post in /r/gifs, but some of the proposed explanations seemed a little pseudoscientific so I wanted to see what everyone here thought.

submitted by /u/PM_ME_REDPANDAS
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Is atmospheric noise truly random?

Posted: 26 Jul 2016 11:26 PM PDT

Many PRNGs say that one of the ways to get true randomness is through processing atmospheric noise. However, my question is, would we ever come to the point where we could predict how atmospheric molecules interact with each other in at least a closed chamber? Or is it completely random and unpredictable? The same question applies to the randomness of radioactive materials.

submitted by /u/challah_is_bae
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Would a box of photons have mass and therefor be "heavy"?

Posted: 27 Jul 2016 12:31 AM PDT

From Wikipedia:

"When two or more photons move in different directions, however, a center of mass frame (or "rest frame" if the system is bound) exists. Thus, the mass of a system of several photons moving in different directions is positive, which means that an invariant mass exists for this system even though it does not exist for each photon."

Essentially a system of multiple photons has a rest mass, even though individual photons don't. I understand this, but would this system be "heavy" in normal terms? Would it be pulled on by gravity like any other massive body is?

submitted by /u/FatalPaperCut
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What holds a chunk of an substance together?

Posted: 26 Jul 2016 07:09 PM PDT

I know there are 4 fundamental forces (gravity, electromagnetism, strong and weak nuclear). When I pick up a solid chunk of iron or gold or something, which force keeps that piece together as one piece. Why does it not just fall apart as a jumble of individual molecules?

Also, when I take 2 pieces of iron and touch them to each other, what force keeps them separate? Why do they not just fuse into one piece of iron?

submitted by /u/MyMostGuardedSecret
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What makes low mass brown dwarfs different from gas giants?

Posted: 26 Jul 2016 07:43 PM PDT

Does Gravitational Potential Energy Increase an Objects Weight?

Posted: 27 Jul 2016 02:59 AM PDT

if a compressed spring weighs more because it has more potential energy does an object weigh (very very slightly) more the higher it is as it has more gravitational potential energy?

submitted by /u/LiquidHelium
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Is the change in observed frequency from the Doppler Effect different for when the sound source is moving than from when the observation point is moving?

Posted: 26 Jul 2016 07:25 PM PDT

Hope that title makes sense. I ask because this came up in my physics class today when we were doing the Doppler Effect. We were using the formula f'=f[(V+Vo)/(V-Vs)] where f' is the observed frequency, f is the original frequency emitted from the source, V is the speed of the wave through the fluid, Vo is the speed at which the observer moves toward the source of the sound, and Vs is the speed at which the sound source moves toward the observer.

When you use speeds of say,

  • 20m/s for Vo

  • 20m/s for Vs

  • or 10m/s for Vo and 10m/s for Vs

it gives three different frequencies. Is this correct? If yes why is it so? Why does the frequency change depend on whether the source of the sound is moving or whether the observation point is moving?

submitted by /u/Pack670
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How do candle wicks stay lit?

Posted: 26 Jul 2016 05:29 PM PDT

Is there one origin of sexual reproduction, or more? What creatures have sexes homologous to humans?

Posted: 26 Jul 2016 07:53 PM PDT

There are bzillions of creatures which exhibit sexual reproduction, but it's not always implemented in the same way- in some fungi, they have hundreds of 'mating-types' (and even if there's just two, we seem to refrain from calling them 'male' and 'female').

This makes me want to ask:

1) How many times has sexual reproduction evolved?

2) What groups of life share a sexually reproducing ancestor with humans?

3) Of the kinds of creatures listed in 2), is the divide between male/female homologous? A human female is probably homologous with a female bison ... but is it homologous with a female shark or a male shark? A female bee? A female octopus? A female flower?

submitted by /u/TwirlySocrates
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How do organisms survive underwater pressures that humans cannot survive?

Posted: 26 Jul 2016 05:45 PM PDT

Why do organic processes like RNA synthesis make mistakes?

Posted: 26 Jul 2016 10:54 AM PDT

My phrasing probably isn't the best here, apologies. But suppose I'm relating these processes to those of a computer. Without some sort of external factor or human error somewhere down the line, a computer doesn't simply "stop working" or perform a calculation incorrectly. There's always a cause for whatever error occurs.

So I guess what I'm wondering is, what kinds of causes lead to these "errors" in the basic processes of living organisms? I've been taught that mistakes in DNA/RNA coding lead to mutations, which lead to genetic variation. But surely mistakes don't just happen without reason?

submitted by /u/TrashboatJones
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What is the storage capacity of the human brain?

Posted: 26 Jul 2016 05:43 PM PDT

Assuming knowledge, memories, etc all take up space in the brain, I'm led to believe there is a limit.

We all know that nobody, or at least most people, do not remember literally everything that happens in their lifetimes.

Disregarding that, at what point would your brain be .. full?

submitted by /u/LordPadre
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How can I produce a flat and full spectrum light source?

Posted: 26 Jul 2016 02:17 PM PDT

Complementing the title: A light with a precisely known spectral power distribution function also works.

Long story short: I'm trying to precisely profile the spectral response of my camera.

For that I pretend to use raw data from the photograph of a spectrum from a descomposed white light.

But, my white light must be either totally flat or must have a spectral power distribution that follows a precise function, so i can compensate for that in my data later.

One of the problems is that i don't know if a filament lamp has a very precise temperature. How could i properly measure the temperature of the filament, so i can calculate the spectral power distribution function from the black body radiation function?

Thanks!

submitted by /u/guferr
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How do we get the first distance of a celestial object without having an other one?

Posted: 26 Jul 2016 02:22 PM PDT

I'm talking about very distant objects like a star

submitted by /u/Ditoune
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Tuesday, July 26, 2016

How do centipedes/millipedes control all of their legs? Is there some kind of simple pattern they use, or does it take a lot of brainpower?

How do centipedes/millipedes control all of their legs? Is there some kind of simple pattern they use, or does it take a lot of brainpower?


How do centipedes/millipedes control all of their legs? Is there some kind of simple pattern they use, or does it take a lot of brainpower?

Posted: 25 Jul 2016 10:24 PM PDT

I always assumed bugs were simpler organisms, so controlling that many organs at once can't be easy. How do they do it?

EDIT: Typed insects without even thinking.

submitted by /u/CrazyKirby97
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Why are there holes in the ozone layer, as opposed to the ozone redistributing itself around the layer to be equally thin everywhere?

Posted: 25 Jul 2016 03:33 AM PDT

Is it possible for a planet to have mountainous terrain that extends past the troposphere?

Posted: 25 Jul 2016 11:28 PM PDT

The highest terrain on Earth is Mount Everest, at 8.848km and the troposphere ends at about 12km. Could continuing plate action over millions more years cause Everest and the rest of the Himalayas to extend past the troposphere or even further? Has any planet been observed with such characteristics?

submitted by /u/SF1034
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If the earth was a cube, what would crossing over an edge be like? Would we be pulled towards the centre of each face?

Posted: 26 Jul 2016 05:33 AM PDT

how accurate is that thing you used to do as a kid where you count the seconds in between a lightning strike and thunder to see how many miles away the storm is?

Posted: 26 Jul 2016 05:36 AM PDT

How come blood vessels and nerves are not pinched when we bend our elbows/knees and other bend parts?

Posted: 25 Jul 2016 05:56 PM PDT

*Bendy parts. Sorry for title typo.

submitted by /u/Chai_wali
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What is the significance of the successful energy modeling of an H2 molecule by a quantum computer?

Posted: 25 Jul 2016 11:23 AM PDT

This was announced recently by what seems like the gauntlet of universities at the cutting edge of technology, but as someone in chemistry who knows little to nothing about computing I feel as though I'm seriously underestimating the importance of this finding.

What does this mean for quantum computing as a whole? Is this as momentous as it seems to a layman like myself?

submitted by /u/SecretAgentIceBat
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For how long can an annoying fly fly around in my bedroom before it dies of starvation or exhaustion?

Posted: 25 Jul 2016 03:35 PM PDT

Why does Chernobly have to wait 1000 years while Hiroshima was able to rebuild without waiting that long?

Posted: 26 Jul 2016 07:05 AM PDT

Hiroshima had an atomic bomb dropped on them.

submitted by /u/correlatefire
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If twins both have sex with a woman, and she gets pregnant, would a paternity test be able to distinguish which one is the father?

Posted: 25 Jul 2016 07:36 PM PDT

Why do we lose our appetite when we're depressed?

Posted: 25 Jul 2016 04:38 PM PDT

I'm in the middle of a rough break up and have lost about 10 pounds in the last 6 or so weeks due to a complete lack of appetite. I dont really even feel hungry throughout the day. Why does this happen when we become depressed?

submitted by /u/stonewasarollingpapa
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Does Hydrogen meet de Broglie justification for Molecular Dynamics? Is MD of Hydrogen valid for "warm" temperatures?

Posted: 25 Jul 2016 09:07 PM PDT

I have a question regarding the treatment of hydrogen as a classical particle in molecular dynamics, using the de Broglie thermal wavelength justification.

Referencing sections 5.1 and 5.2 of "Modeling Materials" by Tadmor and Miller:

I understand their derivation in 5.1: using the Born-Oppenheimer approximations you can derive a time-dependent Schrodinger equation for the nuclear wave functions which has no explicit dependence on the electrons -- only on nuclear positions and the determination that if you can treat the nuclei as classical particles that this function becomes the classical interatomic model.

I also understand the usage of the de Broglie thermal wavelength as a justification for treating atoms as classical particles, not as quantum mechanical ones.

In essence, this justification says that "if the wavelength is much smaller than the average interatomic spacing then the waves are spatially localized and the atoms can be treated as classical particles." If the wavelength is "on the order of (or greater than) the interatomic distances, then the wave-like behavior of the atoms is relevant."

My concern / question regards the treatment of Hydrogen atoms.

They present a case for aluminum and show that the temperature at which the de Broglie wavelength is equal to the interatomic spacing is ~1.34 K -- the treatment of aluminum as a classical particle at even just a few Kelvin is valid.

I'm interested in CH3 (methyl groups). To do the same exercise as above, I want to see if the assumption is valid for Carbon:

hbar = 1.0545718e-34; % m^2 kg /s k = 1.38064852e-23; % J / K amu2kg = 1.66054e-27; r = 1.09; % C-H bond length in Angstroms A2K = 1e-10; m = 12.0107; % amu T = (2*pi*hbar^2) / ((m * amu2kg) * k * (r*A2K)^2) 

T = 21.36 Kelvin -- This is a valid assumption for carbon, even in really cold CH3 molecules. However, when I do this for the Hydrogen (use m = 1.008; ) then I find the minimum temperature to be ~255 Kelvin. So I guess I have several questions:

Q1: Did I do the math right?

Q2: If yes, does this mean that the assumptions in MD aren't valid for "warm" temperatures (~-20 C)

Q3: How valid would trends at/below this temperature be?

Q4: Is there a better justification I should be applying?

Additional Comments?

submitted by /u/Ferentzfever
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What is the .1% of germs that bleach and sanitizer can't kill?

Posted: 25 Jul 2016 03:52 PM PDT

Why do wisdom teeth come in so late, and for so many people need to be removed?

Posted: 25 Jul 2016 05:19 PM PDT

What biological advantage does it serve that wisdom teeth come in so much later than the rest of the adult teeth? What signals the teeth to be ready to come in? What causes the need for wisdom teeth to be removed?

Thanks in advance

submitted by /u/The_stud_in_student
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A falling ball and a ray of light are both moving in straight lines through curved space, and both are accelerated by gravity wells, but why does light "accelerate" so much less than the ball?

Posted: 25 Jul 2016 11:52 PM PDT

A falling body in curved space time is an inertial reference frame: i.e. it is moving in a straight line, but it accelerates because it is in curved space time. Both the ball and a photon are moving in a straight line, and are moving through the same curvature - so why is the photon seemingly curved less than the ball?

For example when you throw a ball forward it moves towards the ground at 9.81 m/s2, as do all objects in earth's gravity, but it is moving in a straight line. So is light so why doesn't a flashlight's rays fall towards the earth's surface at the same rate?

submitted by /u/FatalPaperCut
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Just saw this picture of Moon passing between Earth and NASA's Deep Space Climate Observatory. Why does the boundary of moon (particularly to the right) appear to be green?

Posted: 25 Jul 2016 04:29 PM PDT

If humans have an average core temp. of 98.6 F, why are we so uncomfortable when our environment is this temperature?

Posted: 26 Jul 2016 07:49 AM PDT

I was thinking about this during this summer's heatwave. I know certain parts of the human body (e.g., testes of males) can't be kept at this temperature for extended periods of time, but why is this so hot for us, when internally we are right around this same temperature?

submitted by /u/sergeantbiggles
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How and why does a spinning ball reverse its rotational direction after every bounce?

Posted: 25 Jul 2016 09:49 PM PDT

Is the ocean calm further out?

Posted: 25 Jul 2016 03:47 PM PDT

Likely a hollywood thing but I've noticed in movies when people are stranded out in the sea, likely hundreds of miles from shore, the ocean is very calm.

I'm struggling to google this. Have tried "is the ocean calm further out" "are waves more violent further out" etc.

Thanks

submitted by /u/drohorror
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If the four fundamental forces of nature unify at extremely high energies, would they further diverge at extremely low energies?

Posted: 26 Jul 2016 07:12 AM PDT

For example, would electricity and magnetism diverge at a few fractions of a degree above absolute zero?

submitted by /u/InternetJuice
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I know that computers use base 2, we use base 10 and base 12 would be more useful. But are there other (non-primitive) ways to count things other than "base x"?

Posted: 25 Jul 2016 03:23 PM PDT

Does our galaxy as a whole exert a gravitational force?

Posted: 25 Jul 2016 09:39 PM PDT

How does buoyancy work in microgravity?

Posted: 25 Jul 2016 01:20 PM PDT

If a swimming pool were installed on the ISS, and an astronaut were to immerse him or herself in the water, would they float to one side or the other of the liquid?

Obviously buoyancy on earth counteracts the force of gravity. How do things behave when floating in a liquid when the force of gravity is removed?

submitted by /u/w_spark
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What is a Bloch Sphere?

Posted: 26 Jul 2016 05:17 AM PDT

I'm right now studying for an exam in a course called Light-Matter interactions, and I'm just going over the basics. One of the core concepts in this course is the Bloch vector and Bloch sphere. I've been reading an atomic physics book (CJ Foot, Atomic Physics, chapter 7) where they go through it but it is very confusing. They just throw definition upon definition upon more definitions just so they can end up with a neat set of equations at the end, but they lose me along the way and I have no idea what I'm looking at.

I understand that the Bloch sphere can be used to represent a state in a two state system, including superpositions of states, but how that comes about or why, I have a hard time understanding.

Can someone explain to me in a relatively easy way what it actually does and how it works? Thanks.

submitted by /u/AlmightyThorian
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