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randor

understanding speed that's faster than light

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i am wondering how to explain the fact that while any particle cannot travel faster than the speed of light when that speed is measured "locally", ie from close to the particle , that same particle can be travelling FASTER than light, when that speed is measured from far away.

i think that perhaps an analogy would be as follows: imagine a piece of chewing gum.

stretch it out and put 2 markers on it: X,Y 1/3rd and 2/3rds of the way along.

Now choose a point "A" in the 1st section, and a point "B" in the 3rd section.

Now, stretch the 2 markers apart.

So the distance between the 2 markers (XY) becomes more and more bigger than the 1st and 3rd distances which are not changing.

And, the speed of B as seen from A could now be greater than light if the distance XY increases fast enough, as measured from A (which is considered "far away" from XY).

How can this be explained in equations? (as the Special Relativity Lorenz equations i have seen relate to "local" velocity i believe...)

also, the question is, what would cause XY to be expanding...

the question boils down to - what is the difference between local speed and "far away" speed , and how is "far away" speed measured ? (and what is the correct terminology for that!)

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i am wondering how to explain the fact that while any particle cannot travel faster than the speed of light when that speed is measured "locally", ie from close to the particle , that same particle can be travelling FASTER than light, when that speed is measured from far away.

i think that perhaps an analogy would be as follows: imagine a piece of chewing gum.

stretch it out and put 2 markers on it: X,Y 1/3rd and 2/3rds of the way along.

Now choose a point "A" in the 1st section, and a point "B" in the 3rd section.

Now, stretch the 2 markers apart.

So the distance between the 2 markers (XY) becomes more and more bigger than the 1st and 3rd distances which are not changing.

And, the speed of B as seen from A could now be greater than light if the distance XY increases fast enough, as measured from A (which is considered "far away" from XY).

How can this be explained in equations? (as the Special Relativity Lorenz equations i have seen relate to "local" velocity i believe...)

also, the question is, what would cause XY to be expanding...

the question boils down to - what is the difference between local speed and "far away" speed , and how is "far away" speed measured ? (and what is the correct terminology for that!)

The only thing I can think of that might explain what I think you mean is that far away space is expanding away from you so all sublight particles will be carried along with that expansion. If that makes any sense. Kind of like a boat carried along on an ocean current.

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I recall hearing another example of this in connection woth black holes. The key point is that in popsci explanations, i never heard of the distinxtion between local speed and nonlocally measured speed so now i want to understand that difference some more...

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Space/time itself expands so that things carried with the space/time expansion are not moving thereby within space/time.

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Posted (edited)

I feel a great disturbance in the FOrce ....

Edited by third_eye
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It takes application of force to move material objects within space/time but the motion of space/time itself appears inherent.

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since there is no frame of reference that is absolutely still ... how do we ever know what is moving and what is not ? Master Merton ?

~

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I don't know if it is motion or not, but it seems so. Objects like galaxies over time get further apart.

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terminology ~ can we also say that it is 'space' that is expanding and the galaxies are just rolling along with the expanding space/time continuum ?

I think so ... no reason why not ...

~

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Go with the flow.

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My apologies ...

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PS, i got started thinking about this from hearing a pod cast with dr karl kruszelnicki , dr roger penrose , dr kip thron , from 2007-02-12.

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Well, our galaxy is rushing away from very distant galaxies faster than the speed of light,as measured in those other galaxies, as those galaxies are rushing away from ours faster than the speed of light as measured in our galaxy. Yet our measurment of the speed of light is exactly the same as measured in those other galaxies.

When you throw a rock in a pond, the farther wave is traveling faster than the next wave closer to the plop, or expanding faster. I would say the universe is expaning in the same way. The farther away a galaxy is from ours, the faster it is recieding from us, but the speed of light is the same as measured from all galaxies, as all galaxies can be considered stationary and all other galaxies considered recieding.

Space itself is expaning, the speed of light within that space is always the same.

What was the question again?

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It's about the conductivity of space. Space can only conduct information inside of a certain speed limit but that doesn't say anything about more space being created between two objects. The object isn't actually using any energy to "move" relative to the other. It is not traversing through space to require an infinite amount of marginal energy to push it to light speeds.

Edited by White Crane Feather
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