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Saturday, March 12, 2016

What is the safest speed a human can be accelerated to in a mile?

What is the safest speed a human can be accelerated to in a mile?

What is the safest speed a human can be accelerated to in a mile?

Posted: 11 Mar 2016 08:08 PM PST

I'm just curious as to what speed a vessel could safely reach within a mile without the g force posing a serious threat to its occupant.

submitted by /u/MacNamedDre
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If you had a big enough magnet orbit the earth would it produce electricity of some sort?

Posted: 12 Mar 2016 02:55 AM PST

I was just wondering if this would happen, and if it did could it maybe be a power source for space stations?

submitted by /u/NotableFire
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Do we know that the speed of light in a vacuum is 3*10^8 m/s, or is that the speed of light in dark matter? Does it make a difference?

Posted: 11 Mar 2016 07:34 PM PST

Why do large airplanes retract their landing gear after taking off?

Posted: 11 Mar 2016 06:43 PM PST

Recently there have been a handful of instances in which a plane had to be landed with landing gear that was stuck retracted. I am curious as to whether the benefits outweigh the risks.

submitted by /u/metkja
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[Physics] Why doesn't a superconducting wire gain infinite current?

Posted: 11 Mar 2016 10:03 PM PST

So thanks to V=Blv, the voltage induced in a wire is equal to the magnetic field the wire is moving through, times the length of the wire, times the velocity of said wire.
But when combined with I=V/R, a superconducting wire (R=0) should have infinite current!
Please explain, thanks in advance!

submitted by /u/shadowz749
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Amazing tool. Really need to know how it works http://www.youtube.com/watch?v=vTDPI4xTetI

Posted: 12 Mar 2016 03:55 AM PST

What kind of amazing tool is this??? https://www.youtube.com/watch?v=vTDPI4xTetI This was posted on metalworking and laserclean sureddits and noone seems to know! Does anyone know the physics behind it? How much can it worth?

submitted by /u/trekkies
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Is there a general strategy to show a number can be divisible by a square?

Posted: 11 Mar 2016 06:32 PM PST

I was intrigued by a number theory question that was broken down to finding squares that can divide 10n + 1 for any n. I could easily show what n makes it divisible by 112 and that was sufficient for solving the question, but it was too fascinating to stop there. As title suggest, are there more k and n such that k2 | 10n +1?

submitted by /u/Sharkunt
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If speed depends of the spacial reference system chosen, wouldn't kinetic energy depends too? If so kinetic energy is defined by the object chosen by the observer?

Posted: 11 Mar 2016 09:03 AM PST

How do acid hydrolases survive in the low pH of the lysosome?

Posted: 11 Mar 2016 08:51 AM PST

What is it structurally that allows them to function at pH 5? Thanks!

submitted by /u/bolgnese
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Billions of years ago when the universe was considerably smaller, was matter smaller too? Was there less space separating the electron from nuclei and was the width of a single proton less?

Posted: 11 Mar 2016 08:17 AM PST

If this was the case, then is it understood what this might have meant for atomic physics?

submitted by /u/Garage_Dragon
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How does "anti-odor" clothing work?

Posted: 11 Mar 2016 07:38 AM PST

For example, Uniqlo HEATTECH and AIRism is marketed with anti-odor properties. Is it a characteristic of the fabric they use, or is it a chemical? I believe many other brands like Under Armor do similar things.

submitted by /u/753UDKM
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If there is a probability of an electron being in an excited state of an atom , and there are an infinite number of excited states, wouldn't the probability of the electron being in the ground state be zero?

Posted: 11 Mar 2016 09:13 PM PST

Obviously we can find atoms with their electrons in the ground state, so I feel like I am missing a piece of information here or understand something incorrectly. It seems like a paradox since if we take a measurement at room temperature we will find some atoms with electrons in the excited state, but obviously very few even through there are infinite excited states (or are there?)

submitted by /u/smallestklein
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What if photons (light) had mass?

Posted: 11 Mar 2016 05:46 AM PST

Where do geese (or other birds) go when the weather bounces (from 25 to 65 degrees) like it has this year?

Posted: 11 Mar 2016 07:36 AM PST

I know they fly south and then back up north. The geese here in Indiana seem to have decided to take the cold days off. Then they return on the warmer days. So, this week they were in the ponds from Monday until Thursday. The heavy rains drove them away and so far today it has been to cold. I've been to Florida by plane and car. They can't be going there for the day and returning. So, where are they going? Where do they hide from prying eyes?

While I'm asking I have the same question about sugar ants. They are all over the place one day, gone the next, and then back again. I've never heard that ants hibernate, but what happens to them?

edit: I guessed on a category for this. I wanted to go with Biology, but that seemed to focus more on a molecular level.

submitted by /u/SiRyEm
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How does solid matter stay in the together if it is being spun? Shouldn't relativistic effects tear all matter apart?

Posted: 11 Mar 2016 11:18 AM PST

Obviously, matter doesn't get torn apart when it moves. So I know there is some effect keeping it together. But this is the scenario I imagine: An armature of solid metal, with one end mounted on an axle so it can spin, similar to a clock dial. Set the arm in motion, and the center will be travelling at a slower rate than the outer edge. Since the outer edge is travelling faster, isn't the matter at that point feeling (even minuscule) greater time-related relativistic effects than the matter at the center? And as this happens, wouldn't different points of the arm start to lag (in time) behind other parts? And the matter would get torn apart?

A large armature illustrates this better, but I don't understand why this wouldn't happen at all scales also.

submitted by /u/slimeslug
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Do migrating birds always align into air currents with the least air resistance?

Posted: 11 Mar 2016 06:57 AM PST

Is there an experiment to directly measure the one-way speed of light?

Posted: 11 Mar 2016 05:05 PM PST

To my understanding we only have experiments to measure the two-way speed of light because due to relativistic effects as soon as you move two synced clocks with respect to one another to measure the time a light beam takes to travel, they will disagree, but that disagreement depends on the speed of light. So by convention we just take the average of the two way trip, but for all we know light could move faster in one direction than it does in another?

submitted by /u/SuicidalEclair
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What has happened when a fetus fails to develop one of its hands or feet? Where has that part of the "blueprint" the cells should be following gone?

Posted: 11 Mar 2016 03:35 AM PST

Can Flux pinning happen in a B field and an H Field? If not one of them, why not, and what's the difference between the two?

Posted: 11 Mar 2016 02:35 AM PST

I'm only an A2 Physics student, so while I'm pretty fascinated by this phenomenon, I don't know a great deal.

I read that the number flux tubes are proportional to the flux per unit area - is that not just flux density? This is the main reason I ask this question - I'm trying to see if I can link what I've learned from my studies to this phenomenon to better understand it.

Thanks.

submitted by /u/SickleSandwich
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Science behind knowing time of death of a loved one?

Posted: 11 Mar 2016 07:29 PM PST

In an Askreddit thread that I will link later, people talked about waking up at odd hours for seemingly no reason, then later finding a loved one had died at that time. Multiple people had stories about this happening. I like to believe these stories are real and have some significance, but I like basis in fact.

Is there any name for this phenomenon or any science behind it at all? Hypothesise or anything?

submitted by /u/fff8e7cosmic
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Friday, March 11, 2016

How is there no center of the universe?

How is there no center of the universe?

How is there no center of the universe?

Posted: 10 Mar 2016 07:16 AM PST

Okay, I've been trying to research this but my understanding of science is very limited and everything I read makes no sense to me. From what I'm gathering, there is no center of the universe. How is this possible? I always thought that if something can be measured, it would have to have a center. I know the universe is always expanding, but isn't it expanding from a center point? Or am I not even understanding what the Big Bang actual was?

submitted by /u/Johnny_Holiday
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Do the children of women who suffer from fertility problems have a higher chance of being disabled in any way?

Posted: 10 Mar 2016 10:04 PM PST

With a high enough powered telescope and knowing where to look, would a person be able to see the artifacts left behind on the moon by the Apollo astronauts?

Posted: 10 Mar 2016 07:11 AM PST

How do things tie themselves up?

Posted: 11 Mar 2016 05:43 AM PST

Headphones / fibres / myself, how does it all just randomly tie itself up when left alone?

Like this

Edit: I always fuck up the link brackets.

submitted by /u/BradlePhotos
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How is Earth 4.6 billion years old? What would it have looked like in its proverbial first birthday?

Posted: 11 Mar 2016 02:31 AM PST

What are the differences between how IBM's Deep Blue was programmed when it beat Kasparov vs. Google's Deepmind when it beat Lee Se-dol?

Posted: 10 Mar 2016 03:41 PM PST

Did Deep Blue use "learning" methods like Deepmind? What exactly are "genetic algorithms?" Why aren't we using this technology to make CPU's far more complicated but faster than what humans design?

submitted by /u/Stuck_In_the_Matrix
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In the absence of any meaningful gravitational field, can Einstein's theory of special relativity explain all static, dynamic, and kinematic observations?

Posted: 10 Mar 2016 01:29 PM PST

More specifically, can special relativity model accelerating reference frames? If so, can it make predictions within the frame that is accelerating or can it only make predictions of an accelerating frame while viewing the accelerating frame from a separate inertial frame?

submitted by /u/UniqueWorldline
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Are most advancements in AI from better hardware or more advanced formulae?

Posted: 10 Mar 2016 03:12 PM PST

Theoretically, a computer could brute force a problem to figure out every possible optimal solution, but that is absurdly infeasible in most instances, so systems use tricks such as classifiers and error minimization to get a "best guess."

When new milestones such as Deepmind's recent victories are reached, is this more due to faster processors allowing for deeper/wider searches with existing algorithms, or have the algorithms themselves improved? (I'm sure it's a little of column A and a little of column B, buy I'm asking for a little more specific than that)

submitted by /u/Cranyx
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Does breaking helium into hydrogen absorb energy?

Posted: 11 Mar 2016 04:32 AM PST

If making He from H release energy does it mean that breaking an He atom will absorb energy?

submitted by /u/aimnox
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What does diets, physical and mental exercises affect cognitive functions and, if so, how?

Posted: 10 Mar 2016 05:56 PM PST

What does diets, physical and mental exercises affect cognitive functions and, if so, how?

Thank you, ~Waddlesticks

submitted by /u/waddlesticks
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Had any cultures proposed that stars were other Suns further away before it was scientifically verifiable?

Posted: 10 Mar 2016 02:53 PM PST

Is climate change related to heat capacity of combustion product gases relative to the starting gases?

Posted: 10 Mar 2016 01:52 PM PST

I have generally good knowledge of chemistry, but I am beginning to think that I have understood the mechanism of climate change and greenhouse gases incorrectly from the beginning. I may have just learned the wrong thing early on and never looked back. Here's how I understand greenhouse gases. Let's think about combustion in its simplest form: coal combustion. C (s) + O2 (g) -> CO2 (g). The gas we started with was O2, and we exchanged one O2 mole for one CO2 mole. I always just assumed that CO2 must have a lower heat capacity than O2. Therefore, when the sun's (relatively constant) energy hits a mole of CO2, it is able to warm it up more than it would be able to warm up the mole of O2 that existed before. Hence, the temperature rises. After looking at a heat capacity table, a mole of CO2 has a higher heat capacity than a mole of O2, so this turns my whole understanding upside down. Does a gas' quality of being a greenhouse gas have anything to do with its heat capacity, or are they completely unrelated qualities?

submitted by /u/sorenlarrington
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How can I see the dark part of the moon when it is in its crescent phase?

Posted: 10 Mar 2016 07:16 PM PST

So currently in Arizona and the moon is only partially lit up but I can clearly see the rest of it. It is black but is a different black than the night sky.

submitted by /u/PdanaBaera
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Why isn't the universe's age infinite?

Posted: 10 Mar 2016 12:51 PM PST

I thought I understood this, but on longer thought it seems there's something I need cleared up.

We measure the age of the universe (I believe) by backing out how long ago the universe's expansion would bring the observable universe into a single point, if run in reverse. If we imagine a timeship that somehow moves in the negative time direction, it would take (supposedly) 13.82 billion years to reach this point.

But here's the kicker. We know from general relativity that a high local gravity slows your passage through time. So if we go through a region of space where there is more mass, I expect our passage through time itself to be slowed. As we go further and further back, where the universe was more dense, we move more and more "slowly" through time, never actually reaching the first instant - since this is where the density is infinite and passage through time (I expect) should be zero. So such a timeship would never be capable of reaching the first instant in time; it would instead take forever to reach the beginning.

So where does my reasoning break down? Why do we say the universe has a set age, when as far as I can tell it took "infinitely long" for particles to go from infinitely dense to their current state?

submitted by /u/Dont_Think_So
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Are there any studies that actual show that altering screen colour temperature *actually* avoids sleep disruption?

Posted: 10 Mar 2016 08:17 AM PST

There's a lot of interest in software that alters the colour temperature of screens to avoid disrupting sleep patterns - making it redder in the evening. The new beta of iOS implements it and the f.lux software is popular on Macs.

submitted by /u/HeartyBeast
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Reading recent articles, I get that we recently spotted the most distant/oldest galaxy ever, 13.4 billion light years away. With my understanding of the expansion of the universe, this galaxy was much closer to us than 13.4 bn ly, at the time it looked like what we see of it today. Am I correct ?

Posted: 10 Mar 2016 09:53 AM PST

What I understand is that in 13.4 bn years (close to the universe age) light travels 13.4 bn ly. But when photons left that galaxy to reach us, their "starting point", at that time, was closer to our today position than 13.4 bn ly. So, now, that galaxy is 13.4 bn ly away from us, but was closer then. What was the actual distance at that time? I am getting confused with articles I have read, mixing both (distance and elapsed time), but I may think I understand the expansion of the universe, while I actually do not. Please enlighten me.

submitted by /u/bouli_
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Are there organisms with only a few cells?

Posted: 10 Mar 2016 10:35 AM PST

I know there are lots of single-celled organisms, but even really small multicellular organisms like c. elegans or something have a lot of cells. Are there any organisms that have, say, more than 1 but fewer than 100 cells?

submitted by /u/TheApiary
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Do macrophages (and other immune defensive cells) vary in strength, size and lifespan?

Posted: 10 Mar 2016 11:40 AM PST

I watched a video from Kurzgesagt (in a nutshell) about how some our of immune system works. And I wondered about this question since in the video they mentioned that macrophages die after some time of fighting against the bacteria and they have to be kept living by other cells. But to the macrophages vary in those aspects?

submitted by /u/Chromiczlul
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Why does old water taste "stale"?

Posted: 10 Mar 2016 11:05 AM PST

If I leave a glass of water out for a day or more it has a distinct "stale" taste. What in the water changes? Or is it psychological?

submitted by /u/rgryffin13
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How does gravity bend space in 3 dimensions? The usual depictions shows only 2. (Related, what "shape" is the universe?)

Posted: 10 Mar 2016 10:45 AM PST

Let's see if this makes any sense:

Another redditor made this comment about the universe being "planar", and it reminded of how most depictions of gravity look something like this, which I assume is quite simplified.

But if everything is 3D, how should this look as opposed to these 2D depictions? How planar really is the universe?

I tend think of the universe as a giant dark room with stars/planets/galaxies etc. floating all over in three-dimensional space. Is that totally incorrect? But then thinking of it as something planar with things "sitting" on top doesn't seem right at all.

submitted by /u/Baumkronendach
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Thursday, March 10, 2016

Is everyone's blood brain barrier equally permeable?

Is everyone's blood brain barrier equally permeable?

Is everyone's blood brain barrier equally permeable?

Posted: 09 Mar 2016 11:13 AM PST

Do anti-photons and anti-gluons exist?

Posted: 09 Mar 2016 12:14 PM PST

If not, why not?

submitted by /u/Nathan_Lawd
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Why are DNA bases and RNA bases so different? How can removing a single hydroxyl group have such a large impact?

Posted: 09 Mar 2016 02:10 PM PST

Considering the other groups in DNA bases I would expect that the hydroxyl group would be rather insignificant, yet DNA bases exhibit different chemical properties as opposed to RNA bases (ex: they're more stable) So why does removing this one hydroxyl have such a big impact on the molecule as a whole?

submitted by /u/tdkreturns
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Lasers and white light?

Posted: 10 Mar 2016 03:46 AM PST

If you have 3 lasers - red, green and blue - and combine them into a single beam with mirrors, additive colour theory says you should then have a beam of white light. If you then split this with a prism, will you have the full spectrum or will it just be red green and blue? I know I'm probably wrong about the white light beam, but it makes sense in my head! Alas, I don't have the kit to try this myself or I would give it a go...

submitted by /u/B0b_Howard
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If you take any colour and made it dark enough, would it eventually just turn black?

Posted: 10 Mar 2016 04:26 AM PST

What about different soaps allows them to form stronger/weaker bubbles?

Posted: 10 Mar 2016 05:20 AM PST

I understand the basic chemistry and physics of bubble formation. The polar/nonpolar ends of the soap molecules form a bilayer with water or gas. The bubble breaks when the top of the bubble layer stretches too thin.

My question is, what in the soap itself might affect its cohesive properties? Is there a difference between the actual soap molecules in different dish soaps?

Please let me know if you need clarification as to what I am asking.

EDIT: To clarify further, I'm asking about the intermolecular properties of different soap types/brands, as opposed to their interaction with other compounds.

submitted by /u/gowronatemybaby7
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Why do spinning hub caps appear to spin in the opposite direction?

Posted: 09 Mar 2016 01:31 PM PST

Why can't we cut off the cirrhotic part of the liver and have it regenerate that way instead of having people die by keeping it in?

Posted: 09 Mar 2016 10:44 AM PST

What is the Banach-Tarski paradox?

Posted: 09 Mar 2016 08:14 PM PST

Re: https://youtu.be/s86-Z-CbaHA

I don't understand the paradox here. Uncountable infinity divided by two equals uncountable infinity, that seems pretty obvious on the face of it. What makes this special?

submitted by /u/darkbyrd
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What is the difference between chirality and spin?

Posted: 09 Mar 2016 08:28 PM PST

can a particle be in a superposition of left-hand and right-hand just like they're in a position of up and down?

submitted by /u/chunkylubber54
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With the Banach-Tarski paradox, isn't right up left the same as just up?

Posted: 10 Mar 2016 12:05 AM PST

In this video around 13:40 https://www.youtube.com/watch?v=s86-Z-CbaHA Vsauce is talking about points on a circle. He puts a dot at right up left and up but shouldn't those be the same position? He says nothing about the distance of each direction and I'm so confused. If the distance is not fixed, then there should be up, up, up, etc forever since up up would be redundant. Just one up could stand for all of them.

submitted by /u/LockManipulator
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Are all the space debris are likely to reenter the atmosphere due to orbital decay ?

Posted: 09 Mar 2016 10:23 PM PST

Relative to what point is the speed of light the "velocity limit"?

Posted: 10 Mar 2016 01:59 AM PST

I have always been told you cannot exceed c. To what"stationary" point is the relative velocity c the maximum?

I am not sure I have clarified the question sufficiently so I will explain what I was trying to think about in the first place.

Consider launching a ship from earth. If it reaches a speed of c (or as close as we can achieve) away from earth in the direction away from the sun. We then launch another ship parallel to the first but after a quarter of a year (so the earth has completed quarter rotation and now has max relative speed in the opposite direction to the original ship route) is the maximum speed of the ship going to be the same as the first? When it gains max velocity would it keep a constant displacement from the first? Or would we have to say that it needs to "brake" first and then gain positive velocity due to the original negative caused by the earths rotation? If so then where is the zero point of movement as we are moving round the sun, the sun around the galaxy etc.

I really do appolagise for the convolution of this question and am very keen to hear your answers! Many thanks to anyone who gives their time to deal with me!!!

submitted by /u/whiterabbi
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Why do mutations in BRCA1 and BRCA2 predispose to ovarian and breast cancer only?

Posted: 09 Mar 2016 11:33 AM PST

I cant find any information on this and was wondering why mutations in the BRCA genes are (seemingly) only strongly linked to ovarian and breast cancer, given that these mutations are in a DNA repair pathway. Shouldnt they also be found in other cancers too?

submitted by /u/UsernamesBeAwkward
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Does light exerts a force?

Posted: 10 Mar 2016 12:12 AM PST

We know that any object that has a mass, can exert a force, but does light has a mass and it exerts a force too?

submitted by /u/rav22
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Which gases are we using for Joule-Thomson Effect?

Posted: 09 Mar 2016 12:25 PM PST

What are the gases used in Joule-Thomson Effect and why are we using them? What is the difference between the gases we can use and we cannot?

submitted by /u/baybarsa
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How can H-1 or H-2 go through radioactive decay if they only have 2 neutrons?

Posted: 10 Mar 2016 02:37 AM PST

So I get that it's unstable because it has too many neutrons, but this here (Uni material) says the atom has 1 proton and either 1 or 2 neutrons, so how can it remove neutrons and the nucleus rearrange itself to try and find a more stable form (radioactive decay), if it is only comprised of 3 things?

submitted by /u/friendlyfitnessguy
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Can we use the speed of light to establish a universal rest frame?

Posted: 09 Mar 2016 05:32 PM PST

Since the energy required to accelerate is based on the current velocity could that be used to establish a universal rest frame?

My thought process in case I am missing something:

I am rotating around the earth, which is orbiting the sun, etc...

Since I already have a velocity would it not be easier to accelerate in one direction and harder in another?

I understand that assuming the cosmic microwave background is close to this, the earth's velocity is only about 371km/s which is paltry compared to the speed of light but would this be theoretically possible?

submitted by /u/daed1ne
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Does acetic acid expand when frozen?

Posted: 09 Mar 2016 06:43 PM PST

Wikipedia's article on properties of water includes acetic acid in its list of "other substances that expand on freezing", but when I looked at wikipedia's acetic acid page it quotes the density of acetic acid as a liquid is 1.049 g/cm3 and as a solid is 1.266 g/cm3 which suggests it is denser as a solid so must contract. Clarification?

submitted by /u/bobchuckx
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