"Time Travel"

[Cavernio]

Re: "Time Travel"

Bah, you posted too fast! I can't edit my other post anymore now. Not all matter would stick to the wall, if it were elastic matter, it might not. If we could call light matter at all, would it not be like 100% elastic matter and also bounce back at light speed + shuttle speed? If this is the case, then again, because we're also moving, to us, the light would just be moving at light speed.

[Shaydow]

Re: "Time Travel"

http://www.youtube.com/view_play_list?p=E8EFE6A7EA479666

I love this show, its one of the few things I personally set our dvr here at home to record ( that and House :P ).

A great walkthrough on Light and its speed, how the Universe can bend to accomedate the speed of light, how the Universe itself actually is expanding FASTER then the speed of light, and other neat stuff.

Enjoy.

[QED Stepfiles]

Re: "Time Travel"

This is somthing I have been pondering for quite some time and I would like imput from a few high-level thinkers.
I know there are a couple impossibilities in this idea but please dont get hung up on them.
When you see a star at night, the light you are seeing is not what is happening right now but what was happening (perhaps) millions of years ago based on the speed of light and the extreme distance betwine the Earth and most stars.
So here is my theory.
Assume (by some freak act of phisics) that we found a way to rocket a shuttle many times faster then the speed of light. If we shot this shuttle very far away from earth and passed light for a long period of time would we be able to eventualy stop and (with a very powerful telescope) look back at the earth as it was thousands or perhaps millions of years ago? Just like we on Earth can see the birth of a star that has most likely already died out in real time, could we look back on Earth and see such things as living dinosaurs, or the Battle of Thermopylae? Or possably see yourself playing outside as a child? I'd like to hear your ideas.

So, on the one hand, as you've put it, then yes, it's perfectly possible. Information cannot travel at past the speed of light, and so if we were somehow able to overtake the "information" of times past, then theoretically it would be possible to see the past. Of course, this is a bit of faulty reasoning, since if we were to go past the speed of light, then we in effect (as information) would be violating this rule...

In other words, it's not really meaningful to say "would this happen if we could travel past the speed of light," because if we could travel past the speed of light, then information can too, and really the entire discussion becomes a bit pointless.

EDIT: Whoops, for some reason I thought that I was responding to the most recent post in this thread, rather than the first post... sorry if I broke the flow...

[Cavernio]

Re: "Time Travel"

http://www.youtube.com/view_play_lis...EFE6A7EA479666

I love this show, its one of the few things I personally set our dvr here at home to record ( that and House :P ).

A great walkthrough on Light and its speed, how the Universe can bend to accomedate the speed of light, how the Universe itself actually is expanding FASTER then the speed of light, and other neat stuff.

Enjoy.

Yeah. Light clearly isn't matter, and your question's answered here gaus.

[Afrobean]

Re: "Time Travel"

note that we don't have any physically plausible methods of achieving superluminal speed

Sure we do. We just don't have any practical applications of these physically plausible methods.



Incidentally, wormhole travel: does this fall under the category of superluminal? Your own speed would not be greater than the speed of light, but you'd still be able to arrive at a destination before light.

[Patashu]

Re: "Time Travel"

Sure we do. We just don't have any practical applications of these physically plausible methods.



Incidentally, wormhole travel: does this fall under the category of superluminal? Your own speed would not be greater than the speed of light, but you'd still be able to arrive at a destination before light.

I think I mentioned that one yeah

it's superluminal with respect to an outside observer but not for the wormhole traveller itself

[legato210]

Re: "Time Travel"

well since this is all speculation, I found a video you might be interested in watching.

this man is a genius.

http://www.youtube.com/watch?v=w-prt5d6m6s

[devonin]

Re: "Time Travel"

Whether you think he's a genius or not, a clip about futurists has nothing really to do with what we're discussing here.

[slipstrike0159]

Re: "Time Travel"

Nobody knows whether this is true or not because our understanding of physics says it is completely impossible to go faster than the speed of light.

I was going to post the video i saw on the discovery channel a while back called the universe, but i was beaten to the punch. This may now be approaching the realm of not true because according to the video, some scientists now believe that in the big bang theory (for matter of reference) the explosion threw particles out at speeds faster than the speed of light.

One thing i think is important to keep in mind with this whole theory (obvious impossibilities aside) is that you all refer to the analogy of seeing a star that may have already went through a super nova and its 'old light'. When you try to apply this logic towards trying to see 'old light' i think that its important to realize that, unlike a star, the earth does not give off light going at light speed. It is reflected light from our sun. As small of a difference as this may be, you would have to consider the fact that if you try to look at light coming off from the earth it might go less than the speed of light.
As a point of clarification, we can actually slow light through different mediums. So then would it not be possible that the light coming off of the earth would be going at speeds that are less than the speed of light in a vacuum? Of course thinking in terms of it as either going through the atmosphere or at least touching it enough to use the particles it hits letting it slow down.

Also, im a little shaky on the whole subject of 'looking back at the earth' after speeding away from it at faster than the speed of light. To be able to see that specific planet wouldnt you have to have a direct connection of light to it so you can actually 'see' it? To explain, of course you would have light still hitting you from different directions, but i was always under the impression that to see something through a telescope you have to have its specific light hitting you already. If you have breached the light that is reflected off of the earth (of course only considering you got outside the original light reflected off of the earth at its creation) then you wouldnt be able to see the earth at all.

One last thing, simply enough, if you were moving at extremely fast speeds AWAY from the earth, why would it matter if that somehow allowed you to see it in its previous states? I mean, you wouldnt be able to communicate with it (for radio waves and the like travel MUCH slower), and you wouldnt be able to even get back to it without the light catching back up and it making no difference anyway.
To think of it realistically, look at the theory of relativity. Time moves relative to the observer right? So time would seem to move at different rates for someone on the earth as opposed to someone living on, lets just say, jupiter. Outsides the bonds of our earth we would be trying to time everything according to the system we use ON the surface of the earth which simply would not be the universal system of all the bodies in the universe. Our measuring system in accordance with the rest of the universe would feel rather useless for no matter how fast you are traveling through space, time will always feel different. Thus, time travel in essence would be a virtually useless argument outside the bonds of our own time system, or rather outsides the bonds of time relative to wherever you are.

[Strider11o7]

Re: "Time Travel"

Although I'm not saying that the OP's theory is possible, it would be much more efficient to just look at a clear, reflective surface from far away (like a man-made mirror and placed there or otherwise). It wouldn't require a rocket and you could look twice as far into the past, I think.

[Hachi86]

Re: "Time Travel"

i personally can't see any reason why OP's theory wouldn't work, with the proper assumptions. (FTL travel, indestrucible glass, etc).

He's just taking something we know for fact and applying it to something different. We are sure that we can see light from a million years ago, so why couldn't we go multiple times the speed of light and look back at light reflected from Earth from the sun? Same principle.

Again, with the proper assumptions.

[devonin]

Re: "Time Travel"

Why would seeing old light correspond to seeing an image of the Earth as it was when it was as old as the light is?

[Afrobean]

Re: "Time Travel"

He's just taking something we know for fact and applying it to something different. We are sure that we can see light from a million years ago, so why couldn't we go multiple times the speed of light and look back at light reflected from Earth from the sun? Same principle.

Because faster than light travel isn't possible in actual practice ("indestructible glass"... hah).

It also wouldn't be possible to see it with any sort of detail, so the whole point would be lost. You might be able to see THE EARTH as it was a very long time ago, but you wouldn't be able to see any sort of detail of things on the Earth.

In fact, I'd say the only worthwhile thing that could be done using this technique would be to get an image of Pangea as it actually was, but I would think that wouldn't even be possible since the distance required to "outrun" light that "old" would be too great.

Why would seeing old light correspond to seeing an image of the Earth as it was when it was as old as the light is?

Did you really ask that?

Because the light coming from the Earth that is that "old" would have reflected off of the Earth a very long time ago and thus, it stands to reason that if one saw or recorded that light, what you'd have is an image of the Earth as it was when the light reflected off of it. Assuming, of course, that nothing blocked the path of the light or diffused it or anything.

Speaking of which, how long of a distance would light have to travel before it would become useless for seeing this sort of thing? Obviously the great distances we're referring to would require a tool to see at all, but I mean... obviously if light travels in a straight line forever, it's not going to be "perfect" when it reaches the "end" of its eternal path, even if the light doesn't directly interact with anything. Y'know what I mean?

[devonin]

Re: "Time Travel"

Assuming, of course, that nothing blocked the path of the light or diffused it or anything.

Why does it "stand to reason" that light which reflected off earth a long time ago captured and maintained an image of the earth at the time of reflection? I certainly don't have near enough an understanding of optics to say that with any kind of certainty. Do you?

[QED Stepfiles]

Re: "Time Travel"

Why does it "stand to reason" that light which reflected off earth a long time ago captured and maintained an image of the earth at the time of reflection? I certainly don't have near enough an understanding of optics to say that with any kind of certainty. Do you?

Yes, actually, it's true that unless we're assuming that light is traveling through a perfect vacuum, then there would be quite a considerable amount of scattering of that light as it goes through whatever it's going through. However, at the same time, I do not believe that such a concern is very relevant for the sake of this argument, since we are more or less trying to discuss this theoretically, and such discussion calls for ideal simplifications (such as assuming that the reflected light remains intact).

One thing i think is important to keep in mind with this whole theory (obvious impossibilities aside) is that you all refer to the analogy of seeing a star that may have already went through a super nova and its 'old light'. When you try to apply this logic towards trying to see 'old light' i think that its important to realize that, unlike a star, the earth does not give off light going at light speed. It is reflected light from our sun. As small of a difference as this may be, you would have to consider the fact that if you try to look at light coming off from the earth it might go less than the speed of light.
As a point of clarification, we can actually slow light through different mediums. So then would it not be possible that the light coming off of the earth would be going at speeds that are less than the speed of light in a vacuum? Of course thinking in terms of it as either going through the atmosphere or at least touching it enough to use the particles it hits letting it slow down.

No. You do realize that the index of refraction of air is around 1.0003. This means that light hardly slows down at all in the earth's atmosphere. And, once that light reflects out into space again, where we assume a vacuum exists, it would be going at its "normal" speed once again. Light's particle/wave duality prevents you from analyzing it in such terms as "Oh well it hits a lot of stuff so it must slow down." Once it escapes from a dense medium into a vacuum it will be going at "light speed" once again, regardless of how dense that medium was.

To think of it realistically, look at the theory of relativity. Time moves relative to the observer right? So time would seem to move at different rates for someone on the earth as opposed to someone living on, lets just say, jupiter. Outsides the bonds of our earth we would be trying to time everything according to the system we use ON the surface of the earth which simply would not be the universal system of all the bodies in the universe. Our measuring system in accordance with the rest of the universe would feel rather useless for no matter how fast you are traveling through space, time will always feel different. Thus, time travel in essence would be a virtually useless argument outside the bonds of our own time system, or rather outsides the bonds of time relative to wherever you are.

The earth travels at around 30km/s around the sun. Sure, this seems fast, but relativistically, this is really very, very slow. Time difference of just looking at some object in space is completely negligible, if we were to time such a phenomenon from earth and from jupiter. So yes, you are perhaps right that there is some discrepancy, but scientists don't really care too much about 0.000000000001 seconds. On such a macroscopic scale as watching a macroscopic event in space, such a small time does not matter (if we were talking about particle physics, however, this would be a different matter...).

Sorry I'm picking on you so much, slipstrike, but I'm a bit finicky about scientific detail, and you're way off the mark in presenting these scientific ideas.