Why does it take a million years for a photon moving at the speed of light to reach the sun's surface from its core? | AskScience Blog

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Thursday, January 26, 2017

Why does it take a million years for a photon moving at the speed of light to reach the sun's surface from its core?

Why does it take a million years for a photon moving at the speed of light to reach the sun's surface from its core?


Why does it take a million years for a photon moving at the speed of light to reach the sun's surface from its core?

Posted: 25 Jan 2017 05:00 PM PST

Bonus question...how much of the light reaching earth is million year old light vs. Light that was created close to the surface and is more like 5 minutes old?

submitted by /u/podank99
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What makes nuclear fusion as an energy source difficult to produce?

Posted: 25 Jan 2017 04:51 PM PST

I've read a lot about it and I'm studying mechanical engineering, so I understand the concept generally. But I'm curious/having trouble understanding the constraints on our ability to produce this kind of power.

submitted by /u/AHighFifth
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[astronomy] If the universe expanded at the same rate during the Big Bang why are there areas of high mass density( galaxies) and areas of low mass densities?

Posted: 26 Jan 2017 04:05 AM PST

How does the process of turning protons + electrons into neutrons happen?

Posted: 26 Jan 2017 05:57 AM PST

I'm in first year of high school physics and am currently doing a poster on the life cycle of stars. I was reading a bit in-depth about how the pressures inside neutron stars are so immense that the electrons are "pushed" into the protons, thus creating neutrons. What I don't understand is how this happens? As far as I know a proton consists of 2 up quarks and 1 down quark, and a neutron consists of 1 up quark and 2 down quarks. Wouldn't this proton+electron interaction mean that the proton would need to transform one of it's up quarks into a down quark? How can something like this just happen?

Also, wouldn't you need more than just a proton + electron to make a neutron? When a lone neutron undergoes beta decay it becomes a proton but also releases an electron AND an electron antineutrino. If that is the product of beta decay, why do you not need an antineutrino to turn protons and electrons into neutrons.

Sorry if this set of questions is not clear I tried to make it as understandable as possible!

*EDIT: Fixed one spelling mistake

submitted by /u/TrioXideCS
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If two video projectors play a movie in adjacent walls and their image beams cross each other, would there be any measurable degradation to the quality of the images?

Posted: 25 Jan 2017 12:59 PM PST

Can a black hole lose enough mass to be visible?

Posted: 26 Jan 2017 12:54 AM PST

Considering the effects of Hawking radiation, it is known that black holes slowly lose mass as they take in negative energy from nearby virtual particles and it is possible that they will eventually evaporate completely given enough time.

Would it be possible, at least in principle, for a black hole to lose enough mass that it could no longer sustain an event horizon?

Or does it happen that they are simply too dense? Would it depend on other factors, such as whether or not there is a true singularity at the centre, or an ultra dense arrangement of matter contained in a finite volume of space?

How does our current understanding of physics explain this?

I'm very interested in all your answers and please correct me if my understanding abut any of the above is wrong / incomplete. Thank you.

submitted by /u/Afrotom
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How are we able see the laser in darkness if all the photons are moving in one direction?

Posted: 25 Jan 2017 09:51 PM PST

Obviously in the above scenario laser is pointed in direction other than towards our face...

submitted by /u/troninron
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Does Arrow's impossibility theorem make discussion about the recent elections popular vote a waste of time?

Posted: 25 Jan 2017 10:06 PM PST

I hope it is even possible to ask a question like this here given the political nature of it.

I always thought (perhaps mistakenly) that due to Arrow's impossibility theorem, because we cannot satisfy all the fairness criterion that the majority of these arguments about the popular vote or the electorial college are largely a waste of time because whether we used that system or not, there would still be a hole (from a game theoretic perspective?).

Having said that, I have never read any commentary regarding the US election in my adult life that has ever made mention of this result.

Am I misunderstanding the theorem? Does it not apply in this circumstance?

submitted by /u/jt_lau
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What/how quantum mechanically would one constitute a stable atom/element from an unstable one? I.e how does one determine that neutrons, protons and electrons are stable?

Posted: 25 Jan 2017 08:44 PM PST

Why does small-angle approximation work the way it does in Physics?

Posted: 26 Jan 2017 05:18 AM PST

Why are there no high refractive index materials in the visible region?

Posted: 26 Jan 2017 04:11 AM PST

It seems like the range of refractive indices in the visible region is very restricted. In infrared we have lots of materials like silicon, GaAs and tellurium. And in ultraviolet most refractive indices go up drastically, although not as much as the low bandgap semiconductors. In the visible range, the highest n I know of in a useful material is 2.4 in diamond. Why is that?

submitted by /u/Wiz_Kalita
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Why is routine bloodwork not recommended for children?

Posted: 25 Jan 2017 07:18 PM PST

Why do we not perform or recommend yearly bloodwork screenings in children as we do in adults? Is it simply because being children they are less at risk?

submitted by /u/LadyAithne
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How can we tell if light has been red-shifted?

Posted: 25 Jan 2017 08:06 PM PST

What ever happened to graphene?

Posted: 25 Jan 2017 05:47 PM PST

I remember reading up about it a while ago, the amazing miracle substance. The articles I looked at couldn't shut up about how amazing this stuff is and how it will basically improve everything. I did a little more research today and learned it was invented back in 2004, is it normal for the indoctrination of new materials to take this long? I know that apparently no one really knows how to mass produce it at a reasonable cost, I'm just wondering why it seems like very little progress is being made and how much longer till we start seeing graphene show up in more and more products.

submitted by /u/Giant_Bearded_Face
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What is the fundamental difference between a space dimension and a time dimension?

Posted: 26 Jan 2017 03:23 AM PST

Referring to this SMBC comic. Why would multiple time dimensions make travelling through space easier? http://www.smbc-comics.com/comic/the-dimension-store

submitted by /u/M4rkusD
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Is there any connection between red clay soil types and gold veins?

Posted: 25 Jan 2017 08:48 PM PST

Recently on /r/AskanAmerican, a Georgian commented that there's a lot of red clay out in Georgia. I grew up in the Gold Country of California. There's a lot of red clay out here too.

America's first gold rush was in Georgia and its most famous was here in California. Is there some connection between red clay and gold veins?

submitted by /u/RsonW
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Before it became associated with the period of a 133 Caesium atom, what was the consensus as to how long a second was?

Posted: 25 Jan 2017 03:17 PM PST

Are molecular orbital theory and hybridization compatible?

Posted: 25 Jan 2017 04:59 PM PST

We learned about hybridization (sp, sp2, etc) in class and later we learned about molecular orbital theory. They seemed to give different shaped orbitals so I am a bit confused on if they are competing theories, if they are different sides of the same coin, or if I am misunderstanding. I would really appreciate some help, thank you reddit.

submitted by /u/thebakedpenguin
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Are there stars that are powered by fission?

Posted: 25 Jan 2017 10:41 PM PST

I know that stars are fueled by nuclear fussion. But are there any stars that are powered by fission. And if not is it even possible by our current understanding of physics?

submitted by /u/slayeropolis
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When I shower in the winter, a fan pulls the warm air out of the room while a vent pushes warm air into the room. Does this make the room warmer by venting heat in or colder because of Bernoulli's principle?

Posted: 25 Jan 2017 06:53 PM PST

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