Can Time Travel Really Alter Our Perception of Communication?

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Hi Guys and girls

First have very little knowledge of this stuff, but watched a tv program today that made my head spin a little bit. The threads I have read on this forum make it spin a little more, so I'd like to just post my question and hope there is a simple answer.

The program I watched spoke about someone accelerating at 1G on a trip around the milky way and someone waiting on Earth for them to return. The figures I may have recalled incorrectly but it was something like 150000 years the person would be waiting for them to return but to the person in the spaceship it would only feel like 24 years.

So the person returns 24 years older to find the Earth 150000 years older than they left it.

Now assuming we have the technology for this spaceship and then also the technology to build a continuous communication system with the pilot...

What happens then? For the pilot one second is equivalent to 6250 seconds on earth?!
 
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blake_jl said:
Now assuming we have the technology for this spaceship and then also the technology to build a continuous communication system with the pilot...

What happens then? For the pilot one second is equivalent to 6250 seconds on earth?!
I didn't check the numbers, but essentially yes, at least on average. Since the ship is accelerating the ratio between Earth seconds and ship seconds will vary over the course of the trip, but on average it will be quite large.
 
The point I was trying to make is that if you have constant communications with the pilot, when he returns the times won't align. He will be talking to someone who died thousands of years ago.

After thinking about it more, I think this would be impossible anyway. The communications wouldn't be instantaneous as the waves would have to travel and there would be massive delays.
 
blake_jl said:
The point I was trying to make is that if you have constant communications with the pilot, when he returns the times won't align. He will be talking to someone who died thousands of years ago.
He won't still be talking to someone who died thousands of years ago when he returns, it's just the pilot will (on average) see communications from Earth as running very quickly (like a video in fast-forward mode), so for example if he was receiving continuous video from a room on Earth he might see years of time pass in that room in only hours. So, he can indeed experience 15,000 years of communications from Earth in only 24 years of his own time.
 
OK, so this has bugged me for a while about the equivalence principle and the black hole information paradox. If black holes "evaporate" via Hawking radiation, then they cannot exist forever. So, from my external perspective, watching the person fall in, they slow down, freeze, and redshift to "nothing," but never cross the event horizon. Does the equivalence principle say my perspective is valid? If it does, is it possible that that person really never crossed the event horizon? The...
From $$0 = \delta(g^{\alpha\mu}g_{\mu\nu}) = g^{\alpha\mu} \delta g_{\mu\nu} + g_{\mu\nu} \delta g^{\alpha\mu}$$ we have $$g^{\alpha\mu} \delta g_{\mu\nu} = -g_{\mu\nu} \delta g^{\alpha\mu} \,\, . $$ Multiply both sides by ##g_{\alpha\beta}## to get $$\delta g_{\beta\nu} = -g_{\alpha\beta} g_{\mu\nu} \delta g^{\alpha\mu} \qquad(*)$$ (This is Dirac's eq. (26.9) in "GTR".) On the other hand, the variation ##\delta g^{\alpha\mu} = \bar{g}^{\alpha\mu} - g^{\alpha\mu}## should be a tensor...

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