Pages

Sunday, October 16, 2016

If, theoretically, you were in an infinite sized room, and there was complete darkness. If you lit a candle, how far away would you have to be from this candle before you couldn't see it?

If, theoretically, you were in an infinite sized room, and there was complete darkness. If you lit a candle, how far away would you have to be from this candle before you couldn't see it?


If, theoretically, you were in an infinite sized room, and there was complete darkness. If you lit a candle, how far away would you have to be from this candle before you couldn't see it?

Posted: 15 Oct 2016 01:27 PM PDT

How do astronauts perform wet chemistry experiments in the microgravity?

Posted: 15 Oct 2016 10:49 AM PDT

A titration in microgravity sounds very complicated, for example.

submitted by /u/ngc6205
[link] [comments]

Why does it take some medications (such as antidepressants) up to two weeks to take effect, while with OTC stuff like tylenol it takes a few hours?

Posted: 15 Oct 2016 09:16 PM PDT

How does the new 2 trillion upper limit of galaxies affect dark matter and the "missing mass" theory?

Posted: 15 Oct 2016 12:51 PM PDT

This recent article in 'The Astrophysical Journal' presents that the upper limit of galaxies may approach 2 trillion. Being at least an order of magnitude higher than previous estimates, does this now offer an explanation as to the missing mass in the universe? Does it change the impact or amount of dark matter/energy that may exist, or is the observation of dark matter unaffected and simply the estimated total mass of the universe increases?

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

How does file recovery software work?

Posted: 15 Oct 2016 02:25 PM PDT

There's software that can recover deleted files even after emptying the recycle bin. How does this work?

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

Is there a benefit to seeding an RNG with a large prime number?

Posted: 15 Oct 2016 12:01 PM PDT

How do we create artificial elements heavier than uranium but cannot create hydrogen fusion?

Posted: 15 Oct 2016 12:39 PM PDT

Asking off the basis that you would need to fuse or add more protons, neutrons and electrons to an atom to create heavier elements so why can we not do that with hydrogen?

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

Why is there so much rainfall in East Asia, even though most of it is at the same latitudes as the Sahara desert?

Posted: 15 Oct 2016 04:24 PM PDT

Is gravity the same throughout the earth?

Posted: 15 Oct 2016 08:51 AM PDT

Does it differ in places?

submitted by /u/MarcoSolo23
[link] [comments]

Can gyroscopes at the end of an axle or some other "no thrust" alternative be used to control the rate of precession of a big spinning wheel in space?

Posted: 15 Oct 2016 11:57 AM PDT

Elon Musk's recent presentation of SpaceX's proposed Mars architecture has got me wondering if his giant booster could be used to put a practical "wheel in the sky" space habitat in orbit around Earth.

My goal is a fairly self sufficient community of a few thousand people in space: air / water / waste recycling, hydroponics / fish farm, classrooms, sick bay, shops, offices, entertainment, fabrication, labs. 15-17m diameter x 47m long cylindrical modules are joined by 7.5 degree mating adapters to form a 715 m wheel. Each of the modules has 5 decks that are about 2.5m tall.

Artificial gravity is a necessity, long term bone density loss and other issues are killers. Carbon fiber cables join to a central hub like spokes. Other cables hold the hoop in compression (like the hoop around barrel stays) or spanning module-to-module along the inside. All this cabling keeps our wheel intact as it spins at 1 rpm, giving 0.8 g artificial gravity. The wheel is big enough that Coriolis effect won't make inhabitants nauseous.

My ideal scenario is to launch each module, have tugs meet them and shepherd them into position. Solar and cosmic radiation shielding comes from the walls being filled with a fluid. The outer walls have two layers, and initially the walls are hollow and empty. After the wheel is assembled, the ITS tanker delivers a fluid that is pumped into the gap.

My preferred orbit is a sun-synchronous circular orbit about 700 km and 98 degrees inclination and it would continuously track above the day-night terminator. (There are already several satellites that do this.) In that orbit, I would like the big wheel to precess exactly once a year so that one side of the wheel is continuously facing the sun and the other side always stares into cold dark space. This allows the wheel to have solar panels that are always gathering energy and radiators that are always dissipating excess heat. It also avoids issues that arise from cyclic hot-cold cycles, they would make sealing between modules more challenging and cause fatigue that reduces operating life. Last, it allows one side to have extra shielding for solar protons. I understand that galactic cosmic radiation is a huge issue, especially since the orbit goes above the poles.

The issue is how to make the big wheel track the sun by precessing one turn a year. I did some math and came up with 192 newtons of force being applied to each end of a 200 m axle (one end's thrust point up, the other end down). There is no way to do that with thrusters, the mass of chemical fuel would be enormous. We have an awesome amount of continuous sunshine at our disposal, so a lot of electric power could be available.

Is there another way to apply torgue to the big wheel's axle or change center of rotation or otherwise make the wheel precess?

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

How can the masses of the right and left-handed neutrinos be different?

Posted: 15 Oct 2016 07:31 AM PDT

If a left neutrino is emitted and starts travelling at some speed in a given direction, since it has mass surely I can pick a reference frame where it is travelling in the oposite direction. If that boost does not change the orientation of the spin, do I not end up with a right-handed neutrino in the new reference frame? If so, how can the masses be different? Is mass not Pmu .Pmu, which should be Lorentz invariant?

Also, if the above were true, could we detect right handed neutrinos by having the emission source travel extremely fast with respect to the measuring apparatus?

Thanks!

submitted by /u/Paul-Lubanski
[link] [comments]

Could dark matter/energy be explained by countless black holes?

Posted: 15 Oct 2016 07:37 PM PDT

I was thinking about how dark matter and how gravity can bend light as seen in gravitational lensing. Since our only way of detecting things in the universe (other than through gravitiational waves) is by looking at the light waves that come from space, it seemed intuitive that all this unexplained mass and energy that we classify as dark matter could just simply be from the fact that the photons in those areas never reached earth for us to see. My "theory" for this is that super massive black holes, with strong enough gravitational pulls, intercept the photons that would have reached earth. If this is the case, it seems that depending on how close the wandering black hole is to us, it could block out more or less of the photons that would've reached earth. Thanks! :)

submitted by /u/nick9190
[link] [comments]

What is the difference between measurements of cortical thickness, grey matter concentration and grey matter volume?

Posted: 15 Oct 2016 07:20 PM PDT

I am reading some papers on the effects of meditation on the brain and I am curious what these different measures really mean in terms of what they tell us about the effects of meditation on the brain. Thank you!

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

Can you use an electric field to cause targeted opening of voltage-gated channels?

Posted: 15 Oct 2016 08:24 AM PDT

Just to build on the title...

is it possible to create a local electric field which would cause (or sustain) an open state of voltage-gated channels within tissue?

Or alternatively...

Is it possible to depolarize a cell membrane on a tissue-specific basis? Or do membrane potentials of different cell types overlap in such a way that precisely opening one population of cells would be impossible?

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

Saturday, October 15, 2016

What kind of experiments are the astronauts doing on the ISS?

What kind of experiments are the astronauts doing on the ISS?


What kind of experiments are the astronauts doing on the ISS?

Posted: 14 Oct 2016 08:42 PM PDT

Are they doing astronomy, weather science, or just seeing how things act without gravity?

submitted by /u/PastelFlamingo150
[link] [comments]

Why do objects shatter more easily when they are frozen?

Posted: 14 Oct 2016 08:00 PM PDT

How do drugs which act on serotonin receptors treat disorders of the nervous system?

Posted: 15 Oct 2016 06:17 AM PDT

What senses does an ordinary house fly have? And to what extent does it use them to operate?

Posted: 15 Oct 2016 06:11 AM PDT

I'm creating a first person fly simulator game and I'm interested in getting a better understanding of how exactly an ordinary fly moves, avoids obstacles, finds food, evades danger and so forth.

The game will sacrifice authenticity for fun where needed, but I would like it to be scientifically accurate in general.

My primary points of interest are obviously vision, but also the sense of hearing/feeling? Like if something loud happens, a fly will be spooked, but through what means did it sense it? Did it hear it? Sense vibrations in the air through antennae? Is it able to distinguish the direction the sound came from? To what extent does its own flight make it harder to "hear"?

When hunting food, does it capture food particles in the air and follow them to the food?

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

what causes sunrays to form lines in pictures? why not a field or gradient?

Posted: 15 Oct 2016 06:25 AM PDT

Are the same chemical properties that make HFCs good refrigerants the same as the ones that make it a strong greenhouse gas?

Posted: 15 Oct 2016 06:00 AM PDT

I saw that 170 nations just agreed to ban hydrofluorocarbons (HFCs) in the Kigali Amendment since they are apparently about 1000 times as potent greenhouse gas as CO2. I also know that CFCs are a class of refrigerants that were banned earlier, and I was wondering if the same chemical properties that make these molecules good refrigerants were directly related to their destruction of our atmosphere.

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

How can we hear so many different sounds when sound waves are nothing but frequency and amplitude?

Posted: 14 Oct 2016 06:56 PM PDT

Is diesel a necessary by-product of oil refining?

Posted: 15 Oct 2016 02:00 AM PDT

Some governments are thinking about banning new diesel cars in the long term. I heard that diesel is a natural residual product of oil refining, so if diesel cars were to be banned, oil refiners couldn't just produce less diesel, as it naturally arises in the refining process together with gasoline, bitumen, waxes etc. Is that true? If so, is there something that can be done with the produced diesel outside of burning it for energy?

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

What occurs when a monosomic gamete (n-1) and a trisomic gamete (n+1) undergo fertilization assuming the aneuploidy is on the same chromosome? On different chromosomes

Posted: 14 Oct 2016 11:59 PM PDT

Is there any evidence linking the period of heavy nuclear testing (1940s to 1970s?) to increased rates of cancer, either locally, nationally, or globally?

Posted: 14 Oct 2016 10:52 AM PDT

Where does the energy from black holes merging come from?

Posted: 14 Oct 2016 11:17 AM PDT

I was just listening to a podcast (BBC Discovery - Black Holes: A tale of cosmic death and rebirth) and a researcher on there (Prof. Alberto Vecchio) was explaining that in the merging of the 2 black holes that were the first gravitational wave detection, that they "release more energy than is released by all the stars, in all the galaxies, in the entire universe".

Where does all this energy come from?

submitted by /u/mak2120
[link] [comments]

When you get positron/electron annihilation which leads to the production of two photons, Is it a condition that this interaction can only occur at rest mass energy (where there is no kinetic energy of the e+/e-)? As all examples I see are at this condition with two photons released at 511keV.

Posted: 14 Oct 2016 11:45 AM PDT

I know as well PET scanning relies on the detection of these two 511Kev photons. If this is the case why can't the e- or e+ have greater energy surely this would just lead to the two photons having a greater kinetic energy without violating any conservation laws so far as I can tell.

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

Why does basal body temperature increase when a woman begins ovulation?

Posted: 14 Oct 2016 10:45 AM PDT

Why does basal body temperature increase when a woman begins ovulation? I have found sources which claim that it is due to an increase in progesterone production, is this true? Furthermore, if increased progresterone is the cause of bbt increase, how does progesterone cause this increase? What is going on kinetically?

submitted by /u/athies22
[link] [comments]

Why does sublimation occur for some compounds? What's happening on a molecular level?

Posted: 14 Oct 2016 03:03 PM PDT

What causes some compounds to skip the liquid phase?

submitted by /u/l0__0I
[link] [comments]

Friday, October 14, 2016

When the LHC was created there was an expectation that it would lead to the discovery of the Higgs boson. Do we have any similar discoveries we are expecting to make in the near future?

When the LHC was created there was an expectation that it would lead to the discovery of the Higgs boson. Do we have any similar discoveries we are expecting to make in the near future?


When the LHC was created there was an expectation that it would lead to the discovery of the Higgs boson. Do we have any similar discoveries we are expecting to make in the near future?

Posted: 13 Oct 2016 02:07 PM PDT

What chemically happens in the brain when a person is depressed?

Posted: 13 Oct 2016 09:42 PM PDT

What is the highest a mountain can be? Is there a limit to it?

Posted: 14 Oct 2016 05:11 AM PDT

how is protium stable without a neutron?

Posted: 13 Oct 2016 06:19 PM PDT

I am in grade 9 so please keep it simple :) but without a neutron, shouldnt the electron and proton result in fusion and release energy since negative and positive charges attract? (Correct me on anything and everything, just looking for knowledge)

submitted by /u/The904thDoctor
[link] [comments]

Are there any theoretical limits on the decay half-life of nuclides?

Posted: 14 Oct 2016 05:20 AM PDT

or how fast or how slow a radionuclide can decay?

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

Can we accurately predict the behaviour of, say, a NaCl molecule by knowing the full properties of Na and Cl separately?

Posted: 13 Oct 2016 09:12 PM PDT

I meant to say: Can we accurately predict the properties of a NaCl molecule by knowing the full properties of Na and Cl separately?

Edit: For those interested in the philosophical implications which basically proved to me that this doesn't violate reductive physicalism: http://individual.utoronto.ca/jmwilson/Wilson-Non-linearity-and-Metaphysical-Emergence.pdf

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

How is the Hubble telescope able to take such high definition pictures at those distances and little light?

Posted: 13 Oct 2016 08:46 PM PDT

Why does my TI84 calculator think that sin(8pi) is -4x10^-13?

Posted: 13 Oct 2016 11:11 PM PDT

Why is my calculator slightly off for even a simple math calculation?

submitted by /u/l0__0I
[link] [comments]

For a spaceship or probe to navigate the asteroid belt, how difficult is it without hitting anything obviously?

Posted: 13 Oct 2016 07:06 PM PDT

Basically is the asteroid field like science fiction showing it very dangerous to pass through or are things spread out enough that it isn't as difficult as pop culture suggests?

submitted by /u/sploom17
[link] [comments]

Why is it that we can "see" and even guess the composition of planets that are hundreds of light years away, yet we are unsure of the existence of other planets in our own solar system?

Posted: 13 Oct 2016 06:31 PM PDT

I've heard lots of talk of other planets that may support life based off of guesses at their composition and atmosphere, and these are often hundreds of light years away. Yet we are still not sure if there are even other planets in our solar system beyond Pluto (Planet nine, for example). Is this due to a difference in how they are detected, or is our knowledge of the potential life-supporting planets heavily exaggerated?

submitted by /u/Tomminator95
[link] [comments]

If all the moons of Jupiter collide with the planet, would it become a star?

Posted: 14 Oct 2016 05:12 AM PDT

What's sticking around when a cast iron pan is being "seasoned"?

Posted: 13 Oct 2016 03:35 PM PDT

Statistics and entropy: How many possible configurations are there in a box with 50 red balls, and 50 blue balls?

Posted: 13 Oct 2016 03:14 PM PDT

Fear not, this is not a homework quetsion, but is something I was thinking about after watching this video about entropy by Steve Mould.

He mentions that if you had a box filled with half red balls and half blue balls (assuming they all lie in a flat configuration) and shook the box up, that you would have a higher entropy in the box due a "statistical phenomena" because there is only one possible outcome that results like this.

However, a commenter mentioned that all of the red balls can be interchanged with one another, and all of the blue ones as well. However, wouldn't this result in a lot more possible combinations than one?

I'm not very good at statistical calculations, but as a quick shot at, I thought that the possible configurations of (50) red balls, as well as the (50) blue balls for each configuration of the red, would amount to a total of 50!2 possible combinations that would all result in having red on one side and blue on the other.

This is smaller than 100! (what I presume to be the total possible configurations of the entire box), however, it is much larger than one.

Any insight as to where I have gone wrong, or a more detailed explanation on how entropy statistics like this are calculated are appreciated and thanked for in advance.

submitted by /u/MythicalBeast42
[link] [comments]

How does the revised galaxy count effect Dark Matter?

Posted: 13 Oct 2016 10:59 PM PDT

Hi All

I was just wondering how the revised galaxy count effects the issue of dark matter. As I understand it dark matter makes up a large proportion of the universe we cannot see, do the extra galaxies go any way towards removing the need for dark matter?

submitted by /u/hk135
[link] [comments]

[Geology] What effect do earthquakes have on the relative chronology of layers of dirt/rock?

Posted: 13 Oct 2016 06:12 PM PDT

Suppose an earthquake a long time ago caused layers of ancient dirt, rock and sediment to become exposed on the surface. Today, what might that look like? What clues might exist to indicate that an earthquake took place? If new sediment began to accumulate on it, could the mixup of old dirt and new, make it difficult to figure out the relative ages of different depths of dirt?

If an area suffers from a lot of tectonic activity, like the Caribbean or California or the Himalayan mountains, is the area tougher and/or easier to analyze? What sort of patterns deep in the ground might exist to indicate what's going on? For example, without knowing the Indian plateau is moving towards/into Asia, could a geologist in the Himalayan mountains deduce the plateau is moving, based on soil samples from various depths in the ground? Ignoring the fact that there's giant mountains all around, could the tectonic movement be figured out from underground?

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

If something with a very low statistical probability happens to me, why is it statistically less likely to happen a second time?

Posted: 13 Oct 2016 03:06 PM PDT

Google tells me that "Your odds of being struck by lightning this year are 1 in 960,000". If I get struck by lightning, and I'm not in a profession or position that makes being struck by lightning more statistically probable than anyone else, why does the probability of me getting struck again lower?

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

Does Taylor's Theorem imply Fourier's Theorem?

Posted: 13 Oct 2016 01:03 PM PDT

If all continuous functions can be represented by polynomials, and sin/cos are continuous, that implies every form of sin or cos has their own Taylor series. Does this mean that every function that has a Taylor series can be translated to a series of equivalent sines and cosines?

submitted by /u/joev714
[link] [comments]

Why do peak flood waters occur days after the raining/hurricane has stopped?

Posted: 13 Oct 2016 09:57 AM PDT

I live in North Carolina and have a lot of friends in the eastern part of the state who are experiencing heavy flooding as a result of Hurricane Matthew. I keep seeing reports saying that peak flooding levels will occur on Friday, but it stopped raining on Saturday/Sunday. What gives?

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

How is the probability of a nuclear reaction occurring calculated?

Posted: 13 Oct 2016 11:58 AM PDT

I noticed that when you fire an alpha particle, neutron, or other particle at certain elements, there can be a variety of different reactions: For example, deuterium fusion can results in three different outputs (Helium, Tritium, or another I can't remember) with a fixed probability for each. With the exception of neutrons it seems that it is quite rare for the new nucleus to simply be the old nucleus plus the amount of neutrons and protons in whatever you shot at it (alpha, proton, etc) when I look in a table of reactions.

How is this probability calculated? Is it just observed and recorded as what it is, or is there some sort of mathematical way to figure out these probabilities?

submitted by /u/USI-9080
[link] [comments]

TIL abdominal muscles are a vestigial feature in humans. What did they used to be? And how long ago did we last use them?

Posted: 13 Oct 2016 07:26 PM PDT

I think vestigial features are one of the coolest aspects of Evolutionary Biology and today I found out that abs also fall under the vestigial category. Unfortunately, a Google search into what purpose they served and when didn't yield me many relevant/reliable sources. Thanks in advance!

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

Quantaum teleportation and how it works?

Posted: 13 Oct 2016 06:51 AM PDT

I have read a couple things about it and the most recent was from a chapter in "Beyond our Future in Space" by Chris Impey. He probably did a great job explaining it but the only I got out of it is that an object from one place can be broken down to particles and teleport to another place where the particles will be put back together. It seemed very weird.

submitted by /u/captaincrunch003
[link] [comments]

What is the main difference between organic PVs and inorganic PVs?

Posted: 13 Oct 2016 10:32 AM PDT

Aside from the material, what are the main differences between organic solar cells using fullerene derivatives and inorganic, silicon based cells? I guess I should also add CdTe cells and all thin films. Are there differences between the mechanisms to convert energy? Sources would be great if possible. Thanks!

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