Can Light travel faster than Light?

If this side of the Universe was travelling more than half the speed of light in direction A and the other side of the universe the galaxies were travelling as fast but in the opposite in direction B can we use light to ever see them?
I have trouble even thinking this situation through, yet it is going to be the norm in the future if the universe keeps expanding more rapidly.

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In the situation you describe, A and B are over the "horizon" from each other and what happens in one will never be known in the other since the light from one will never reach the other.

 

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Well how much of the Universe is over the Horizon then?

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If the universe came from a singularity driven to expansion, how would any two things reach a point where light would "never" reach the other side?

They have always been connected, the scenario you made is impossible.

Unless something relative to something else is going faster than the speed of light.

 

Likely most of it. More every day. Radius of the visible iuniverse is about 42 billion light years since what was sent from 14 billion years ago is now that far away due to expansion of the universe since the light started traveling.

 

now I did see an explanation for that to, but you would think initially that from the big bang, if it happened 14 bya that the radius would be just twice that, i.e. 14 billion years of light expansion in all directions around that point.

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In what direction is the light travelling that doesn't reach you?

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No, the radius would be 14 billion light years and the diameter 28 billion light years if the universe was not expanding. The "place" the photons we are seeing now which have been traveling for about 14 billlion years is now about 42 billion light years from us. We will never recieve the light that is being emitted from there now. It is for all practicle purposes, no longer a part of our universe.

Actual Univrese age is thought to be 13.7 billion years, more or less.

 

Likely all directions from its point of emission. A sphere, not considreing curvature of space.

 

Correct me if I'm wrong here, but in your example you state that point A & B are moving away from each other at a little over the speed of light?

But neither A or B is moving at the speed of light. So if a photon is emitted from A towards B, your saying it will never get to B.

I think that's wrong. At the very moment the photon is emitted it's traveling at the speed of light towards B (it's no longer connected to the source A which is traveling at a speed a little over half the speed of light in the opposite direction). My point being the photon is moving at the speed of light towards B and B is only moving at a little over half the speed of light.

Please explain to me how that photon won't ever reach point B?

 

Seperation velocity of A and B exceeds c.

 

I'm sorry but light just doesn't work that way. As soon as the photon is emitted, the only thing that matters is the distance it has to travel towards B and as long as B is not moving away at greater than the speed of light, the photon will catch up to it.

I'm sure you've watched the science programs that explained that when light is emitted from a moving body the speed of the moving body neither adds nor detracts from the speed of the light. That would mean that as soon as a photon is emitted from A, A no longer has any effect on that photon and from that exact point in space that photon is now moving at the speed of light towards B. If B is not moving faster than the speed of light the photon will reach it at some future time.

 

This time you are not pulling my leg. I think you are right, but so far you are the only one who thinks like this.

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You mean so far I'm the only one that cared enough to point it out. I can see how it might look like light might not be able to catch up to B, but that's only if you think light acts in a conventional way, which it doesn't.

 

I think it isn't just a case of the light going from the point of emission to point b, it is travelling though expanding space. Spacetime is expanding while it's travelling. Maybe it's like if you were driving on a road toward a destination, but th road kept stretching faster than you can drive. You will never get there.
Jim S.

 

I've got the thread going in two forums, and I have received a variety of answers. Still think your is correct so I am going to take it back over to the other one and look really smart!

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That might be the case if it was expanding faster than light speed but in this case it is going just over half light speed so it will Red shifted but still get there. When Spacetime expands will the speed of light go up to?

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How do you know that the expansion rate out there is about half light speed? I'm pretty sure there are cosmologists who think there are (or will be) objects whose light can never reach is, but I doubt if I could completely follow their explanations. I know darn well I couldn't follow their math!

 

No, Light can't travel faster than Light, because Light travels always as Light.

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To answer this question we first need to determine how light travels.


Do you agree that light travels like this?

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So what you are saying is that new space is being created fast enough to keep points A & B moving away from each other faster than the speed of light. Somehow I really doubt that that is true. But for the sake of arguement lets say that it is. A emitts a photon towards B, that photon is moving at 'c' towards B. But same photon is moving away from A at 'c' plus the amount of new space being created. Anyway if A & B are moving away from each other at just over the speed of light and the light is moving towards B at the speed of light it just doesn't seem reasonable that the light will never reach B. There is one other thing to consider. Every one of the galaxies at the edge of our visible universe is still there. We've never seen any currently visible galaxies disappear beyond the so called cosmic horizon. Does that mean no currently visible galaxies are moving away from us at greater than light speed? Next question, if we see galaxies in all directions moving away from us at the same calculated speed. Which direction are we moving and why can't we see less of a red shift in that direction?