Speed of Light question

[jgbrowning]

Light doesn't "stop". If it did, it couldn't be light, it would be something else.

http://www.msnbc.com/news/242698.asp



joe b.

 

[Umbran]

Reasons why I disagree with the theory about the speed of light and black holes pull is that the rules of our understanding change to an unknown bases when our physics is applied to a black hole.

Ah, but you see, until you get inside the event horizon, a black hole is not fundamentally different from any other massive object. A black hole bends light in exactly the same way a star of the same mass does. You are correct that inside, all bets are off. But then, the stuff inside cannot communicate with the rest of the universe anyway, so what happens inside hardly matters.

However when you consider that our perception is what limits our understanding it kinda opens up some new possibilities.

Not really - because if you can't percieve the thing, or the thing's effects, then it isn't really part of your universe. And if you can percieve the thing, or it's effects, you can know about it.

So- say there is something that is faster then the speed of light, something we can't see. How would we detect it it travels/moves faster then anything we can percieve (using our eyes, using advanced machines, etc- light is still the fastest "thing")

We'd detect it the same way we detect everything, by watching it interact with other things. We measure the speed of light by knowing when it left point A, and detecting when it interacts with something at point B. It moves faster than anything else in the Universe, so it isn't like we see it coming to point B, or watch it as it goes along. We wait until it gets there, and figure out how long the trip took after the fact. This hypothetical thing that moves faster than light would be no different.

Believe me, it isn't as if people have not been searching for evidence of things that move faster than light. They've been searching since Einstein posited that C was a constant for all observers. And they haven't found anything yet.

Our knowledge of the speed of light is based on the gravity around us, if we understood that light travels at different speeds in different areas of gravity then maybe we'd be able to understand the physics of a black hole a little better.

If what you said were true, that light increased in speed as it fell inward to a massive body, then we should be able to measure the difference. Experiments to test this have been done. The thing you describe is not observed to occur. Instead, something else occurs - instead of speeding up, the light shifts frequency.

The frequency shifts just enough to cover the energy gain or loss that we expect to occur. So, if the speed were to change as well, where would the extra energy be coming from or going to?

<shrug> thank you for your time and trying to help me get past this theory. I guess I am just not willing to accept that we understand everything absolutely.

Nobody but you has said anything about our understanding being absolute. But new theories do have to be consistent with the observations we already have. And those observations are not consistent with your hypothesis.

 

[Nellisir]

Nothing - not even light, penetrates the "hole" It's slung off the exact opposite side.

Incidently, a black hole's gravity doesn't somehow grow due to it's new status. It's gravitational pull is the same as the star it came from and the event horizon is, usually, near where the surface of the star was in life.

Neither of these sounds quite right. If #1 is true, then a certain number of "black holes" would, to us, look like massive streams of x-rays bursting out of nowhere.

If #2 is true, then what happens when two black holes meet? And where did that monster black hole at the center of the Milky Way (that's the latest thinking, I think) come from?

I haven't done much science reading though, so I might be out of date.
Cheers
Nell.

 

[Umbran]

If a star is bigger than the sun - say - 100x the mass - it will collapse into a neutron star. Here the collapse is so violent that all the atomic nuclei in the star loose their charge and become neutrons (hence the name).

Small corrections - this has nothing to do with the violence of the collapse. The collapse could be nice and slow and quiet and gentle, and you'd still end up with a neutron star.

In addition, it isn't that the atomic nuclei lose their charge. What happens is the pull of gravity is so great that it overcomes the forces that keep the electrons out of the nucleus of the atom. The electrons are inexorably forced into the nucleus, close enough to the protons that they fuse and become neutrons.

Ten times bigger still are the stars which, in theory, spawn black holes. Here Stephen Hawkings (I believe) theorized that all black holes have a single mass - any thing that collides with them (and any excess mass at their creation) is slung off as high energy xrays.

Another correction - this is not true. We have black hole candidates of many masses. From supermassive things that live in the cores of galaxies, down to more run of the mill remnants of supernovae.

 

[Michael Morris]

Ok..

Anyway, If I understand correctly black holes are also a big hole in our physics model. They are example of things which are both (potentially) insanely massive and small. The science of really big things (relativity) and really small things (Quantum Mechanics) start to fray and fall apart when they both have to apply at the same time. Figure out what's going on in a black hole and win the Nobel prize, right?

 

[trancejeremy]

Incidently, a black hole's gravity doesn't somehow grow due to it's new status. It's gravitational pull is the same as the star it came from and the event horizon is, usually, near where the surface of the star was in life.

(Disclaimer - I am not a scientist. Astronomy is one of my favorite hobbies but don't quote me as an expert).

I am not a scientist, but I was a space science major in college. That is not quite true The event horizon (the part where light cannot escape from) is much, much, much smaller than the star that collapsed.

Just do a search on "Schwarzschild radius" (If I spelled his name right, it's been a while) and you can see the equation. It's pretty simple.

If our sun were to somehow magically turn into a black hole and keep the same mass, it would only be a few kilometers big. The event horizon. The actual mass is concentrated into a single point, though.

(But stars have to be 5 times the mass of the sun to turn into one via a supernova.)

Anyway, black holes actually do make sense according to relativity and quantum mechanics. They do cause problems with Newtonian physics, but observating black holes has helped to prove a lot of things predicted by relativity.

It's just that relativity and quantum physics don't make much sense. Well, they do, but it's not common sense, since it's not something we observe on an everyday basis in life. But mathematically they do.

 

[Thotas]

Yes, Spoony; figure out what's inside the event horizon, get the Nobel and a huge place in history. But as Umbran points out, we've got things on this side very thoroughly investigated. That whole speed of light thing has been analyzed to whatever degree has been technically possible since Einstein, and the results always come out the same. The speed of light in a vacuum is the speed of light in a vacuum equals c which is a constant as per what Einstein called his invariance theory.

As far as the force that bends light being able to slow it down, that's gravity. It might seem obvious to some that this is what happens with a black hole, right? Can't escape 'cause it's slowed down too much, right? No again. Gravity accelerates things, but acceleration isn't always a change in over all speed; change in direction is acceleration, also. A photon trapped in a black hole is now orbitting the singularity ... at the speed of guess what.

In fact, if you really want to get technical about it, light isn't the only thing that always moves at the speed light. That other thing would be ... everything. Again, "time and space" as separate entities is an inaccurate assumption that leads to a whole mess of inaccurate deductions. Through space-time, everything has a space-component-velocity and a time-component-velocity. A beam of light has a much higher space-velocity than most things we encounter day to day, but all of those things have a much higher time-velocity than the light. But for any object/particle/signal, if you add the two components together, you get that same universal speed all the time.

 

[der_kluge]

www.pbs.org has a lot of good articles on black holes. You can do a search for "black hole" to find all kinds of stuff.

Once upon a time I found episodes of, I though NOVA, regarding black holes and physics topics like quantum physics, but I can't find them now. It might not have been NOVA, but I thought it was.

 

[glass]

The science of really big things (relativity) and really small things (Quantum Mechanics) start to fray and fall apart when they both have to apply at the same time. Figure out what's going on in a black hole and win the Nobel prize, right?

I thought M Theory was supposed to have smoothed over the disconnect between Relativity and Quantum Mechanics?


also non-physicist glass.

 

[glass]

In fact, if you really want to get technical about it, light isn't the only thing that always moves at the speed light. That other thing would be ... everything. Again, "time and space" as separate entities is an inaccurate assumption that leads to a whole mess of inaccurate deductions. Through space-time, everything has a space-component-velocity and a time-component-velocity. A beam of light has a much higher space-velocity than most things we encounter day to day, but all of those things have a much higher time-velocity than the light. But for any object/particle/signal, if you add the two components together, you get that same universal speed all the time.

That would mean that light has no time component velocity right? So from a photons point of view, it exists for zero time? Freaky.


glass.