Time and the Speed of Light

[Mudhammam]

Isn't it also said that space is expanding faster than the speed of light? So what does THAT mean in relation to time?

It means that from our perspective, photons emitted from regions of space expanding faster than the speed of light will never reach us.

From the perspective of the photons, they already did.

Put that in your pipe and smoke it.

But that defies all logic! >_<

[Heywood]

Isn't it also said that space is expanding faster than the speed of light? So what does THAT mean in relation to time?

It means that from our perspective, photons emitted from regions of space expanding faster than the speed of light will never reach us.

From the perspective of the photons, they already did.

Put that in your pipe and smoke it.

Negative,

If you traveled at the speed of light toward an object and the space between you and that object was expanding faster than the speed of light, your destination would be reached in an instant from your perspective. However your ultimate destination would not be that object you aimed for because that initial desired destination is simply out of your reach.

[Anomalocaris]

What part does not make sense to you?

Basically that light travels at a definite and finite speed and at that speed time ceases to be.

Time doesn't cease to be. It just stops progressing relative to our frame of reference. In its own frame of reference it goes merrily on the same as normal.

If you actually were to be acclerated from our frame of reference all the way to the frame of reference of the photon, you personally would never detect any change or transition.

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It means that from our perspective, photons emitted from regions of space expanding faster than the speed of light will never reach us.

From the perspective of the photons, they already did.

Put that in your pipe and smoke it.

Negative,

If you traveled at the speed of light toward an object and the space between you and that object was expanding faster than the speed of light, your destination would be reached in an instant from your perspective. However your ultimate destination would not be that object you aimed for because that initial desired destination is simply out of your reach.

You seem to implie there is in theory some some absolute marker that could denote your desired initial destination. There isn't.

This is a conceptual error.

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It means that from our perspective, photons emitted from regions of space expanding faster than the speed of light will never reach us.

From the perspective of the photons, they already did.

Put that in your pipe and smoke it.

But that defies all logic! >_<

No. From the perspective of the photon it will never reach us either.

[pocaracas]

Special relativity defies logic?
Oh.... wait until you hear about relativistic effects in quantum mechanics!

[Jackalope]

Chuck is right - I had a brain fart.

[Mudhammam]

I'm still failing to grasp how, say for example humans who developed the technology to travel at 99.9% light speed, could travel for 5 light years, say from another planet to ours in that distance, and for us it would appear as though their journey took 5 years, for them only a moment or two? Can light never age? For example, light emitted from the oldest observed stars?

[Heywood]

You seem to implie there is in theory some some absolute marker that could denote your desired initial destination. There isn't.

This is a conceptual error.

I know, but I didn't know how else to explain it so that it would be understandable.....so I substituted simplicity for accuracy.

[Anomalocaris]

I'm still failing to grasp how, say for example humans who developed the technology to travel at 99.9% light speed, could travel for 5 light years, say from another planet to ours in that distance, and for us it would appear as though their journey took 5 years, for them only a moment or two? Can light never age? For example, light emitted from the oldest observed stars?

There is no meaning to light aging. The photon experience changes, but not because of time. Let's say a photons is emitted by the surface of a neutron star, travel 1 billion light years, and then hits another neutron star.

To the photon, it would come into being with a certain amount of energy. It would instantly lose a major portion of its energy as it ascends the sides of the gravitational well surrounding the source neutron star, instantly traverse 1 billion light years, and then instantly gain a lot of energy as it descends the the gravitaitonal well surrounding the target neutron star.

[Mudhammam]

Can something independent of time experience changes? Doesn't a sequence of changes preclude cause and effect, which precludes time?

[Anomalocaris]

Can something independent of time experience changes? Doesn't a sequence of changes preclude cause and effect, which precludes time?

I think you are considering photon as a discrete object that travels through time and space, and so it must feel the effects of agents of change acting upon it as a sequential cause and effect. But photon is not like that, and thinking about it this way is bound to lead you to make unsupported conclusions about what is happening.

Think of a photon as a field that is mostly unobserved but spans the entire universe for all time. The interaction of between the field and local conditions give rise to the observed photon. The rule governing the behavior of the field is such that the observed photon appears to be localized and to move at the speed of light. But there are experiments that can tease out the simultaenous presence of the what is underpinning a photon at any location away from where you think the photon actually is at a specific time.

If you tack a clock to the location of the observed photon, that clock would move at the speed of light through space and would appear to stop to a person in a different frame.

But the photon "field" itself does not experience this motion, and is not subjected to this frame. This is no object that is actually following this frame.