Speed of light vs time

[nmoushon]

So with the newest claim of the most distance galaxy ever seen popping up again, and my coffee kicking in, I got to thinking. We all know that the light we see (or capture in images) from any celestrial object is actual light that was sent from a mere 8min ago (i.e the sun) to 13.1 billion years ago (i.e. the newest most ditance galaxy). So we are, for lack of a better description, seeing snap shots of the past. So my highly caffinated brain came up with these hypothetical situations:

Man has invented a way to travel faster than light. So if a space ship was moving away from earth, faster than light, and had also invented a way to view a "live" video of earth at a constant scale, would they be watching a video of the earth that is showing it going back in time? So watching the moon orbit the earth in reverse and the earth orbiting the sun in reverse. So then if they recorded the video and then played it backwards they would then be watching a "live" video of the past moving forward?

Is this how it works or have I had a couple too many cups of coffee?

[JulianO]

Yes - moving faster than light means you have time travel. You'll also get a stern note from Einstein and have to stay in over break time.

[ronin]

From what you have specified I would say No.

They would be seeing a live video of the earth, as you stated they have managed to do somehow.

If the time rate altered then it would not be a live video so falls outside your scenario and "laws".

Problem is that the rules and possibilities you give prevent what you want. A live video is live, not yesterday or tomorrow. What you seem to be wanting is a "live video" but not showning "live video".

If you went back in time there comes the question how did the camera send you the video before it was installed?

If you put the camera up today it will have recorded nothing yesterday. it was still in it's box.

[nmoushon]

From what you have specified I would say No.

They would be seeing a live video of the earth, as you stated they have managed to do somehow.

If the time rate altered then it would not be a live video so falls outside your scenario and "laws".

Problem is that the rules and possibilities you give prevent what you want. A live video is live, not yesterday or tomorrow. What you seem to be wanting is a "live video" but not showning "live video".

If you went back in time there comes the question how did the camera send you the video before it was installed?

If you put the camera up today it will have recorded nothing yesterday. it was still in it's box.

I understand the live video wouldnt really be a live video. Tis why I put quotes around my live. But the video camera is on the ship with you moving faster than light so the camera is traveling with you and sending the data to the computer on the ship thats is also moving with you. So it would essentially be a camera on a telescope that  is (with its special new invention) keeping earth at the same scale. So everything (myself, the camers, the data, the ship) are all traveling at the same speed so there wouldn't be any space tearing paradimes lol. Right?

Yes - moving faster than light means you have time travel. You'll also get a stern note from Einstein and have to stay in over break time.

Is it really time traveling or is it just the viewing of the past? Because light is constantly traveling at the same speed and once you slow down out of FTL wouldn't time catch back up to you?

[JulianO]

It is certainly viewing the past. It depends what you mean by time travel somewhat. 

Say you travelled away from the Earth at lots of times the speed of light, and then looked at the Earth through a ultra-powerful telescope, and saw dinosaurs roaming around (this is all a thought experiment). So you're seeing the Earth about 50 million years ago. Can you interact with them? No - because you're 50 million light years away. You can't even poke them with a 50 million light year long stick as it would take at least 50 million years for the "poke" to move from you to them, probably a lot more. You'd need a faster than light poking stick. If you had one of those I suspect you could poke them, and see the action of poking them through your telescope.

The question is, if you zip back in your faster than light ship back to Earth, will there be dinosaurs or not?

This is where relativity comes into play. Does going back to Earth undo what you were seeing, or have you travelled in time.

Tricky question! Not sure I know the answer - as we can't manage step 1 currently!

[JulianO]

Wiki has some useful info on the subject. http://en.wikipedia.org/wiki/Time_travel#Via_faster-than-light_.28FTL.29_travel

I rather like the http://en.wikipedia.org/wiki/Tachyonic_antitelephone

[ScottS]

Having just read this thread, my sense of logic has now put on it's coat and called a taxi.

[jetstream]

Einstein says that spacetime is self adjusting,so the closer you get to the speed of light the more it adjusts itself to keep the speed at or under the SOL.This is why quantum entanglement and photon creation interests me,and the creative ideas posted here hinge on whether there can be exeptions to Prof Einsteins long standing theory.Time adjusting itself to regulate speed....amazing

[George Jones]

Einstein says that spacetime is self adjusting,so the closer you get to the speed of light the more it adjusts itself to keep the speed at or under the SOL.This is why quantum entanglement and photon creation interests me,and the creative ideas posted here hinge on whether there can be exeptions to Prof Einsteins long standing theory.Time adjusting itself to regulate speed....amazing

Standard quantum theory that is taught in university, and that so far works extremely well, is linear. In linear quantum theory, quantum entanglement cannot be used to transmit information faster than the speed of light. Physicists have played around with non-linear extensions of quantum theory, and, in these non-linear versions of quantum theory, quantum entanglement can be used to transmit information faster that the speed of light.

[Knight of Clear Skies]

Man has invented a way to travel faster than light. So if a space ship was moving away from earth, faster than light, and had also invented a way to view a "live" video of earth at a constant scale, would they be watching a video of the earth that is showing it going back in time? So watching the moon orbit the earth in reverse and the earth orbiting the sun in reverse.

Remember to mount your camera on the front of your spaceship, facing directly away from the Earth. After all, you will be catching up with the photons from behind.

[slickfonzy]

The question becomes moot when you think about what would happen before the traveler even breaks the speed of light.  Relativity tells us that as the traveler accelerates, their experience of time is slowed compared to a stationary observer.  Such time dilation becomes increasingly significant as the traveler's speed approaches the speed of light.  If the traveler could accelerate to just shy of the speed of light (relative to the rest of the universe), time dilation would be approaching infinity and would reach the point where the entire life of the universe would be over in what seems, to the traveler, a blink of an eye.  At least they'd find out whether it ends in a big crunch or not!

[JulianO]

Well the question is moot because you can't exceed the speed of light in any sensible way as far as we know, practically or theoretically. However - if we could...

[Knight of Clear Skies]

Thought experiments often make a useful and fun learning tool, even when they use a dash of magic in the setup.

[slickfonzy]

Well the question is moot because you can't exceed the speed of light in any sensible way as far as we know, practically or theoretically. However - if we could...

...then the only logical extension of the time dilation effect would mean that time for the traveler would be going backwards, so it would represent actual time travel.

[symesie04]

Surely if the camera is mounted on the rear facing earth then as you accelerated past the speed of light it would cease to record anything? Surely if travelling faster than light then none of the photons leaving earth would be able to catch the camera? And cant say "well if they invented a way to get the camera to record it" as that just isnt a reasonable idea. Just a thought

[nmoushon]

Surely if the camera is mounted on the rear facing earth then as you accelerated past the speed of light it would cease to record anything? Surely if travelling faster than light then none of the photons leaving earth would be able to catch the camera? And cant say "well if they invented a way to get the camera to record it" as that just isnt a reasonable idea. Just a thought

Thats actually a very good point. So there is actually no way to record a viewing of the past or even view it with your own eyes.   BUT you forgot that this is a magical camera that can go around the law of physics...so its still recording who really shot JFK.

[Pig]

You would always be travelling faster that the speed of the video link and as a result wouldn't be able to see anything.

[symesie04]

Thats actually a very good point. So there is actually no way to record a viewing of the past or even view it with your own eyes.   BUT you forgot that this is a magical camera that can go around the law of physics...so its still recording who really shot JFK.

Magical indeed. But it would still have to be mounted on the front as to see the past you would need to catch up with the light of an event that has already been and left our earth and heading for deep space (if not absord by some other event). So you would need to hoover it up as you travelled, and given the fact that light photons diverge that really would have to be some magic camera. Also if you wanted to view a partiuclar event in history you would surely have to work out the exact point in which the earth was facing to be able figure out the exact direct in which to chase those photons into space. Now i stand in awe at the achievments of technology over the past few decades as much as the next man, and wonder just what the future will bring. But I think on this you really are into the realm of pure make believe, in which case what would happen is irrelevant as its make believe and couldnt ever possibly come to pass, so just assume whatever outcome you like as your the narrator  

[nmoushon]

Magical indeed. But it would still have to be mounted on the front as to see the past you would need to catch up with the light of an event that has already been and left our earth and heading for deep space (if not absord by some other event). So you would need to hoover it up as you travelled, and given the fact that light photons diverge that really would have to be some magic camera. Also if you wanted to view a partiuclar event in history you would surely have to work out the exact point in which the earth was facing to be able figure out the exact direct in which to chase those photons into space. Now i stand in awe at the achievments of technology over the past few decades as much as the next man, and wonder just what the future will bring. But I think on this you really are into the realm of pure make believe, in which case what would happen is irrelevant as its make believe and couldnt ever possibly come to pass, so just assume whatever outcome you like as your the narrator

Oh I knew this was make believe when I started the thread. But I do love having conversations about the "what if' of pretty much anything. Sometimes the conversation is purely based in reality, sometimes it ventutures into the realm on "maybe in a couple decades technolgy will advance enough to..." but most the time its starts with an idea in reality but quickly takes a turn to "not even close to reality but fun to think about". Which happened here. I think this is how all great inventions or discoveries have come to be. Some idea starts in reality and then follows one of those paths. Plus I just love hypothetical science talk.

[laowho]

Standard quantum theory that is taught in university, and that so far works extremely well, is linear. In linear quantum theory, quantum entanglement cannot be used to transmit information faster than the speed of light. Physicists have played around with non-linear extensions of quantum theory, and, in these non-linear versions of quantum theory, quantum entanglement can be used to transmit information faster that the speed of light.

Well,

Not exactly. John Bell, who devised the inequality equation for the Aspect experiments to carry out the Einstein-Podolsky-Rosen thought experiment which Einstein hoped would prove certain quantum implications wrong, was asked which interpretation he favored according to the experimental results (demonstrating quantum entanglement, aka Einstein's hated "spooky action at a distance")...that of faster-than-light travel or a non-local universe? He preferred the latter.