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Sunday, August 28, 2016

Is the earth pulled toward where the sun is now, or where the sun was 8 minutes ago?

Is the earth pulled toward where the sun is now, or where the sun was 8 minutes ago?

Is the earth pulled toward where the sun is now, or where the sun was 8 minutes ago?

Posted: 27 Aug 2016 03:32 PM PDT

Why do magnetic objects create lines of force instead of uniform fields?

Posted: 28 Aug 2016 06:23 AM PDT

Why can we create all visible colors by combining three colors while the aspect of their wavelength is linear?

Posted: 27 Aug 2016 02:34 PM PDT

So we can create all our visible colors by combining (additive or subtractive) a base set of three colors. However, what differenciates these colors is their wavelength which then again lies between the two points of red and blue (or let it be two points with an even shorter/longer wavelength). So why do we need three colors rather than two? And why then exactly three and not four or more?

submitted by /u/Liaro
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Can an element's properties be predicted from the structure of its atom?

Posted: 27 Aug 2016 09:44 PM PDT

I.e., imagine there was no gold on Earth and humans had never encountered the stuff before. Would we be able to guess that "Unknown Element 79" would be yellow in color, very dense, and melt at 1947.52 °F based on the fact that it had 79 electrons, 79 protons, etc?

submitted by /u/ArcaneConjecture
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Why can't we see clearly underwater?

Posted: 27 Aug 2016 11:03 PM PDT

When you rub something to create static electricity, how do the electrons decide which side to stick onto?

Posted: 27 Aug 2016 11:08 PM PDT

Zion Harvey got a double hand transplant at 9 years old. Will his hands continue to grow along with the rest of his anatomy as he ages?

Posted: 27 Aug 2016 09:37 PM PDT

How exactly does the McCollough Effect work, and why does it last so long?

Posted: 27 Aug 2016 09:08 PM PDT

Do animals have wars, like humans do?

Posted: 27 Aug 2016 08:54 PM PDT

What about the other 99% of electrons NOT in the outer shell? Do electrons in complete inner electron shells do anything interesting?

Posted: 27 Aug 2016 04:01 PM PDT

Are solar panels in space an efficient source of energy?

Posted: 27 Aug 2016 02:24 PM PDT

How would the energy be transmitted to the surface? In focused beams?

submitted by /u/xXxXxXxVICTORxXxXxXx
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Why is light speed specifically 300,000km/s?

Posted: 27 Aug 2016 08:37 PM PDT

What affects the rate of growth of cancer?

Posted: 27 Aug 2016 03:05 PM PDT

I know that cancer is an broad term, but I was reading the story of Paul Kalanithi who had his cancer spread incredibly quickly, versus other cancers that are less aggressive. What exactly makes the rate of growth (of the same type of cancer) different?

submitted by /u/optogirl
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How would galactic internet work?

Posted: 27 Aug 2016 10:14 AM PDT

Nothing can beat the speed of light, and we all know that, at least with our current technology. However, since we are eventually going to conquer another planet someday, we would want to figure out how to access the internet from a nearby star system.

Let's say we conquer Proxima b - the closest planet that "supports" life, if we want the internet there, we'd have to start from scratch. If we wanted other websites from Earth, we'd have to wait 4.2 years, maybe even longer if the speed is slow. How would we turn this 4.2 years into seconds?

submitted by /u/MedukaKeyname
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Could Dark Matter form "Dark Black Holes?"

Posted: 27 Aug 2016 04:57 PM PDT

It was an idea that occurred to me today after reading about Dragonfly 44. Could Dark Matter form a Dark Black Hole? If so, and the hole followed the same general laws as normal black holes, would that mean they would release a format of Energy as they evaporate? (Do they evaporate?)

Sorry, this question got me thinking about a lot of different questions regarding Dark Matter.

submitted by /u/Usagi-Nezumi
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Black holes. Could we see an event horizon's silhouette against a bright background?

Posted: 27 Aug 2016 12:08 PM PDT

From the perspective of earth. A black hole is positioned in front of a star. do we see a dimming of the star and possibly even the black disk of the event horizon silhouetted against the star? Or do we see a distortion/flipped image of the star due to gravitational lensing?

submitted by /u/DetroitPirate
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Is the negative energy in the Dirac sea actually negative energy or is it a neat accounting tool?

Posted: 27 Aug 2016 06:39 PM PDT

What is the speed of gravity?

Posted: 27 Aug 2016 06:37 PM PDT

I've heard some people say it's the same as the speed of light, but one of my friends says it is instantaneous. He says we could communicate across the universe using gravity kinda like in Interstellar.

submitted by /u/Invisibleman145
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Can d Electrons Ever be Valence?

Posted: 27 Aug 2016 01:06 PM PDT

So I know the traditional view is that elements want to get a complete octet and since the d subshell is considered n-1 when [back]filling, we usually don't consider it valence. What about if we had an element with a full s and d subshell (lets say Zn), which then lost 2+ electrons? The first electrons to be removed would be the 4s electrons by convention, meaning the 4n shell is now empty. How do we consider this new orientation, as 4s0 or 3s2,3p6,3d10?

Thanks in advance for the help!

submitted by /u/BigPoppaE
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What factors determine what direction a quantum of light goes from its source?

Posted: 27 Aug 2016 10:20 AM PDT

How much does cattle feeding contribute to climate change?

Posted: 27 Aug 2016 03:07 PM PDT
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Saturday, August 27, 2016

Is there a formal way of deciding what fraction of a game is chance?

Is there a formal way of deciding what fraction of a game is chance?

Is there a formal way of deciding what fraction of a game is chance?

Posted: 26 Aug 2016 12:16 PM PDT

The card game of "war", in which players flip cards and compare their values without ever making any decisions is clearly entirely probabilistic, (each player will win half the time, as long as the deck is perfectly shuffled before each game.) The game of chess has no probability involved because the game state is entirely dependent on input from the players. These are examples of games at the extreme ends of the scale, but is there a way of assigning a specific value of how much probability plays a part in a game for those that are in between the extremes?

submitted by /u/graciousgroob
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Can an atom be made of only from protons and electrons? Why are neutrons needed?

Posted: 27 Aug 2016 02:45 AM PDT

Hey geologists/historians and other smart people, what is underneath all of the sand in the Sahara desert?

Posted: 26 Aug 2016 10:45 PM PDT

I've just been watching the Wildest Middle East series, and it jogged my memory on a question I've always had. What would be underneath all of the sand in the Sahara desert? What would it look like if one were to remove all of the sand? Side question: where did all of the sand come from?

submitted by /u/Hcapade
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As far as I know we can trace the origin of humans back to Africa. Does the same apply to other animal species?

Posted: 26 Aug 2016 11:28 PM PDT

Not nessecarily Africa, but can each species be traced back to having their origins at specific areas on Earth?

submitted by /u/shadowmoses
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What is the state of an object halfway through the event horizon of a black hole?

Posted: 26 Aug 2016 02:11 PM PDT

In a recent thread, /u/GrandmaBogus asked a very intriguing question, but I feel it got buried a bit too deeply before someone with more knowledge could see it:

Let's assume the simple case of a non-rotating supermassive black hole and a hapless astronaut being exactly halfway through the event horizon. This being a supermassive black hole, let's assume that the tidal forces at the event horizon are not strong enough to rip the astronaut apart.

Now, GR would tell us that all the worldlines beyond the event horizon point towards the singularity. There is no possible way for anything beyond the event horizon to increase it's distance from the singularity, or even to stay put. Everything always moves towards the center.

This would then mean that anything crossing the event horizon gets disintegrated into the most elemental particles as pretty much every form of force that could communicate information would be broken at the "membrane". The lower half of the astronaut would be completely decoupled from the upper half - or put more precisely, every time a bit of the astronaut moves beyond the horizon, it gets decoupled from the remaining part outside.

Put simply, it seems like it is impossible for anything more complex than the most elementary particles to exist beyond the event horizon, because no known form of force can exist between two objects where one of them is beyond the horizon while the other isn't.

This goes against the often repeated notion that with a sufficiently large black hole, one can cross the event horizon unscathed. Or perhaps this notion should be qualified that it won't be tidal forces that cause the demise of the astronaut?

Now I understand that black holes and event horizons are a GR concept and therefore are incompatible with quantum effects, but it would be nice to hear the opinions of experts on the topic.

submitted by /u/short_sells_poo
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What happens when Barium touches Mercury?

Posted: 26 Aug 2016 10:22 PM PDT

What makes the Magnets attractive?

Posted: 27 Aug 2016 12:07 AM PDT

Given an interesting sequence of numbers can we determine the probability that they are random?

Posted: 27 Aug 2016 03:16 AM PDT

I was reminded of this problem by a recent post.

Let's say we have a random number generator RNG which generates numbers uniformly in the range [1, 1000].

You are given an envelope and you are told that it contains 5 numbers in the range [1, 1000]. You are also told there are two possibilities.

  1. This envelope was filled with the first five numbers which came out of the RNG.
  2. The numbers were determined using some other process, for example they were picked by hand.

You have to determine the probability of the RNG having been used.

You open the envelope. The numbers are: {111, 111, 111, 111, 111}.

If the RNG was used, the probability of this exact outcome is 1 in 1015.

Intuition says no, the RNG was not used. Is there a rational basis for this intuition? Remember there are (1015 )-1 other outcomes which did not occur, for example {1, 20, 400, 20, 1}. Is there anything special about {111, 111, 111, 111, 111} and {1, 20, 400, 20, 1} which we can use to solve the problem?

I don't know why this is so difficult.

submitted by /u/rryderr
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What is it about being in a moving elevator that cuts off your cell service?

Posted: 27 Aug 2016 06:27 AM PDT

I don't know if this is specific to where I live but I find that whenever I'm in an elevator and it's moving I don't get a cell signal.

submitted by /u/ASexualZebra
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Does people that have lost limbs have higher blood pressure?

Posted: 26 Aug 2016 11:38 AM PDT

Why is increasing your heart rate through exercise beneficial for your health, but increasing it via stress, fear, or shock detrimental to your health?

Posted: 26 Aug 2016 01:03 PM PDT

Could be a ridiculous question, but how is it that one method for working out your heart is good for you and other bad for you? It seems like the end result is the same, an increase in heart rate and stronger heart muscles. Am I missing something here?

submitted by /u/thevidyy
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How do autopilot cars know when it's safe to make turns?

Posted: 26 Aug 2016 07:05 PM PDT

I'm not quite sure how to describe what it is that I'm asking but let me try to put it into perspective. Imagine you're in an intersection and you want to make a left turn. There are 2 oncoming lanes and one of them is also making a left turn, and there are still cars going past its blind spot in the next lane. Every now and then you'll see an opportunity to make a turn but very quickly you realize you actually don't as the gap gets filled by another oncoming vehicle in the blind spot of the car turning left. So then because of that blind spot, we tend to be more hesitant and slower in making left turns because we're never quite sure if it's safe to go. I find this to be especially true if you're trying to make a left turn at an intersection on a hill.

So how does say... Google's or Tesla's autopilot make these decisions? I live in Vancouver, and I'd say during a busy hour I'm usually only able to ever clear that left turn safely until it's near the end of a yellow light. Because for people here, they tend to treat the yellow light as a "speed up and beat the red".

submitted by /u/sKyLineCA
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What is the difference between a single loop railgun and a series augmented railgun, and how does the latter work?

Posted: 26 Aug 2016 04:26 PM PDT

Since storage on computers isnt "actual" sound, could we replicate a famous persons voice?

Posted: 26 Aug 2016 05:31 PM PDT

I saw this question on a askreddit comment thread but never saw an actual answer. But since sound pictures etc etc is stored as binary digits, could we modify or do something to them to replicate a famous persons voice or something similiar to that?

submitted by /u/Topdogedon
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Question about being surrounded by a large mass?

Posted: 27 Aug 2016 01:51 AM PDT

Hello,

Imagine the setup in this image.

I wonder what would happen gravitationally if we placed a small spherical object (blue), inside a spherical but very massive object that is empty/hollow on the inside, with just a thin surface (gray).

Would there be movement between objects or would they stay in the same position? Would the result change if the object on the inside was heavier?

submitted by /u/PhysicsQuestion02
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Sinclair method claims 78% success rate in treating alcoholism, why is it not used universally or at least more often if this is the case?

Posted: 26 Aug 2016 04:16 PM PDT

I just read that cold cannot be created, only heat can. This makes no sense to me, as air conditioners pump out cold air. Can someone please explain?

Posted: 27 Aug 2016 12:21 AM PDT

I read in an article that cold cannot be created and it's apparently a law of thermodynamics. The article said this: "It's a general thermodynamic fact (a law even!) that generating cold is impossible. You can generate heat, and you can move it around by taking advantage of the fact that heat always tries to "even out""

So refrigerators work by "sucking" the heat out, making it cold. But air conditioners, you can actually feel air blowing at you, not air being sucked out. I don't understand how this works. How is an air conditioner not generating cold air when I can feel cold air blowing at me every time I use one?

submitted by /u/rkerr97
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When light is reflected off a surface, is that same photon being bounced back or is that photon absorbed and then another one emitted?

Posted: 26 Aug 2016 03:07 PM PDT

If air and water are both considered "fluids" in Physics sense, why are their applications labeled pneumatic/hydraulic, respectfully, and not just hydraulic?

Posted: 26 Aug 2016 11:34 PM PDT

How old are the oldest bat colonies still living?

Posted: 26 Aug 2016 12:43 PM PDT

Does a material exist that becomes more malleable the colder it becomes?

Posted: 26 Aug 2016 05:04 PM PDT
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Friday, August 26, 2016

Wouldn't GR prevent anything from ever falling in a black hole?

Wouldn't GR prevent anything from ever falling in a black hole?

Wouldn't GR prevent anything from ever falling in a black hole?

Posted: 25 Aug 2016 05:34 PM PDT

My lay understanding is that to an outside observer, an object falling into a black hole would appear to slow down due to general relativity such that it essentially appears to freeze in place as it nears the event horizon. So from our point of view, it would seem that nothing actually ever falls in (it would take infinite time) and thus information is not lost? What am I missing here?

submitted by /u/andrebis
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What form of numeric differentiation is this?

Posted: 25 Aug 2016 05:52 PM PDT

I needed to code up a quick check of a routine that returned the derivative of some function so I found myself doing (f(x+e)-f(x))/e as e got tiny. So far so good. Then a coworker said that in his experience (f(x+e)-f(x-e))/2e was more accurate for e > 0 because it was symmetric. I checked that in the limit e-->0 they returned the same derivative for simple functions. What form of numeric differentiation is this? Is it more accurate? Thanks!

submitted by /u/DrunkenPhysicist
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[Computer Science] Why do torrents slow down as you're reaching the very end?

Posted: 25 Aug 2016 04:16 PM PDT

What is the most effective form of sterilization of bacteria used in hospitals? Do hospitals in other countries use the same methods?

Posted: 25 Aug 2016 04:38 PM PDT

Hello Reddit, in the near future I plan on creating and designing my own experiment for my IB Biology IA. Currently, I am thinking on testing the effectiveness of different type of sterilization methods, presumably on tools in a hospital setting.

I've heard of different methods: Sanitizing Solutions, Boiling water/Steam, and even UV Lighting. But the real question I have is do other counties follow the same procedures and methods? Is there no "best" method of killing bacteria or do all kill with the same effectiveness? An answer would be very much appreciated as this will provide more depth and expand my experiment from just the United States, but the rest of the world. Thank you.

Also, if you have any tips or methods for measuring bacteria, that would also be appreciated.

submitted by /u/RelentlessRetort
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Why do we use Half-Life for elements and not Quarter-Life or any other fraction?

Posted: 25 Aug 2016 04:33 PM PDT

Why does fat distribution seem to change as people get older?

Posted: 25 Aug 2016 04:08 PM PDT

this is purely anecdotal as far as I know, but I know a ton of people who used to be chubby all around as teenagers and young adults, their body would put a lot of the fat in their thighs and in general spread pretty evenly around their body. As they get older it seems that they have totally fit looking legs and arms, but fat starts getting distributed straight to their gut (men and women alike.)

Is it known why this happens?

submitted by /u/timothybugjunior
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Silver or copper? Which is the better antimicrobial metal?

Posted: 25 Aug 2016 08:50 AM PDT

Hello!

I was recently researching about the antimicrobial properties of silver compared to copper, more precisely if theoretically Ag+ or Cu2+ (two active ions) would inhibit gram-negative bacteria to a greater extent under the same set of optimum conditions.

I wanted to find out which one would have a higher biocidal activity/ inhibition of a bacterium but found split opinions. Two sites for example suggest copper as the better substance. [1] [2]

Yet there is the much wider medical use of silver.

Secondly if the Cu or Ag would be in the compound for of AgNO3 and CuSO4 would the nitrate and sulphate group matter or would only the copper and silver cation inhibit?

submitted by /u/Dan0r
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Does extreme sleep deprivation cause hallucinations, and if yes, how/why?

Posted: 26 Aug 2016 05:10 AM PDT

Can there be current without voltage or voltage without current?

Posted: 26 Aug 2016 06:39 AM PDT

The following is an incorrect proof, but I cannot determine why. Help me with my physics, please! (I think the explanation lies with alternating current.)

Let us consider a circuit of a household located in the United States. This circuit begins at the electrical panel, connects to a receptacle, and then leads back to the panel. The receptacle has nothing plugged in, and so there is no load on the circuit. Therefore, no energy is being used, either; i.e., P=0. We also know that V=120, because this is an American household. Now, by definition of power, P=IV, which implies P=120I by our assumption about voltage. Furthermore, P=0 implies 0=120I, or that I=0. However, using Ohm's law, V=IR, we see that 120=0*R implying that 120=0, which is a contradiction. ///

submitted by /u/saint_sipes
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If a new country was formed and wanted to make it's own fiat currency, and the international community recognized it, how would the value be determined?

Posted: 25 Aug 2016 02:25 PM PDT

Is there an equivalent to a nucleation site in phase transitions other than liquid to solid?

Posted: 25 Aug 2016 11:45 PM PDT

How does the Blockchain work?

Posted: 26 Aug 2016 04:58 AM PDT

How does a Blockchain work mathematically. What is a Block and what do I need to calculate a Hash?

submitted by /u/traendy
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Why is the atmosphere of Earth primarily Nitrogen and Oxygen while our nearest neighbors, Venus and Mars, both have atmospheres of mainly CO2?

Posted: 25 Aug 2016 02:52 PM PDT

What would happen if the speed of light suddenly increased by 1%?

Posted: 25 Aug 2016 10:37 AM PDT

Obviously, I assume it would experimentally be quite easy to find out that the universal speed limit of the universe is now 303,000km/s, but what effects would be visible to the human eye, if any?

What if we up that number to say 350,000km/s?

submitted by /u/Zaldebaran
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If a collision in the large hadron collider created dark matter, would it detect it?

Posted: 25 Aug 2016 03:21 PM PDT

As fat as i've understood it, dark matter does not react with regular matter, so could it be detected in high caliber experiments like the Large Hadron Collider. If not, how would you detect it on earth?

submitted by /u/Penetrator_Gator
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How does encryption actually work?

Posted: 25 Aug 2016 11:02 AM PDT

I understand that 2 primes are easy to multiply together, but hard to find the combination of primes that makes a number, making it an almost irreversible calculation (except looping through every possible combination), however I have never come across an explanation as to how this is actually used to encrypt something - what do these two (or more?) numbers have to do with what I want to encrypt?

For example, if I want to encrypt the character "b", ASCII 98, how does this work? Would it be 98 multiplied by a random prime?

Also, is this the same as "hashing"? I understand the salt, but not the process of the original hashing... (Descriptions I have been given of hashing go along the lines of "calculations that are only 'one way'")

Thanks, Matthew

submitted by /u/-TheMightyMat-
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Why are new elements made in more or less numerical order?

Posted: 25 Aug 2016 02:31 PM PDT

The artificial elements created in particle accelerators, most recently #118 i believe, have been created in more or less numerical order. As far as i know, they are created by smashing nuclei of two different lighter elements, who's atomic numbers add up to the number of the desired element. So why don't physicists 'jump ahead', for example to the theorized islands of stability?

submitted by /u/baldman1
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what are the p-adic properties of the partition function and how does the proof work?

Posted: 25 Aug 2016 11:58 AM PDT

I'm a high school student doing advanced maths, and came across an old news story about Ken Ono's advancement of partition theory. i understood the basic concept, but i couldn't understand the paper link to paper: http://aimath.org/news/partition/folsom-kent-ono.pdf

submitted by /u/WJTDroid
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Why do electric fields and current density tend to concentrate at areas of high curvature and in narrow channels?

Posted: 25 Aug 2016 08:49 AM PDT

I am working on a Comsol model for my research, and I've noticed that I have some pretty non-uniform fields, and I can't seem to explain why I have such high gradients. Any help would be appreciated!

submitted by /u/bme_phd_hste
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How can different oil products be transported through the same pipeline without mixing?

Posted: 25 Aug 2016 04:36 AM PDT

I've listen to the planet money episodes about oil and they mentioned that oil and oil products can be transported via pipelines without mixing.

How is that possible? Is there no mixing at all or only very little that it can be ignored?

submitted by /u/H4kor
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