"Time Travel"

[Hachi86]

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]

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]

Originally Posted by Hachi86

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.

Originally Posted by dev

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]

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]

Originally Posted by devonin

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).

Originally Posted by slipstrike0159

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.

Originally Posted by slipstrike0159

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.

[Afrobean]

Originally Posted by devonin

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?

Your contention is whether the light would be able to carry the image that far without dilution?

If our telescopes are picking up old light off of stars and giving us a good picture of it, is it really that big of a stretch to imagine that the same process could be used with better technology to a planet from a similar distance?

And yeah, this is all really just a simple question: if it were possible (which it certainly isn't), would the same idea hold true? I submit that it certainly would, but anything you could see in this manner would be essentially useless.

But if we could TRAVEL TO THE ENDS OF THE UNIVERSE faster than the speed of light, could we SEE THE BEGINNING OF TIMEEEEEEEEEEEEEEE?

[ShAiOnEi]

There is no way time travel could be executed unless you could find a way of manipulating space and time. As of seeing our selves in the past due to light travel speeds I find this a very hard task to do.

[devonin]

Your contention is whether the light would be able to carry the image that far without dilution?

My contention is whether the light "carries" the image at all in that kind of meaningful sense.

The impression I'm getting from the way this process is being described is like, "Light hits the planet, is reflected off, and goes out into the depths of space, and we're going to go supre fast past it, turn around and look at it!" I don't really see how that will let us see much of anything except "some light" even assuming we pretend that there's no diffusion at all.

I'm presumably just missing something integral in the process here. Do I assume instead that we're just going really far away and then looking at the actual physical location of the planet, and somehow will be seeing it earlier in its history because we went away faster than light? Even assuming we also corrected for the fact that Earth won't exactly be where we left it either.

[Heartseeker7]

Originally Posted by Afrobean

But if we could TRAVEL TO THE ENDS OF THE UNIVERSE faster than the speed of light, could we SEE THE BEGINNING OF TIMEEEEEEEEEEEEEEE?

This brings in a whole different topic of whether the universe goes on forever, or if it ends at a certain point. I personally would rather see whats on the other side of the "ends of the universe" then the beginning of time.

[John McPain]

Originally Posted by Heartseeker7

This brings in a whole different topic of whether the universe goes on forever, or if it ends at a certain point. I personally would rather see whats on the other side of the "ends of the universe" then the beginning of time.

I would rather keep the discussion on topic please?

Originally Posted by Afrobean

obviously if light travels in a straight line forever

I know it doesen't help my case at all but light does not alwase travel in a straight line. Light can be bent from gravity and magnitism.
Source = http://van.physics.uiuc.edu/qa/listing.php?id=1170

[devonin]

I suppose we also have toa ccount for the whole "Light can act as a particle and as a wave" thing. It seems like light as a wave would be the best source of the clear view you're supposing we might have, if simply because light as particles seems like it would be more susceptible to gravity and magnetism causing problems.

[John McPain]

Originally Posted by devonin

I suppose we also have toa ccount for the whole "Light can act as a particle and as a wave" thing. It seems like light as a wave would be the best source of the clear view you're supposing we might have, if simply because light as particles seems like it would be more susceptible to gravity and magnetism causing problems.

I agree but aren't waves also susceptible to unwanted abberation through differing mediums?

[MDMAngel]

Originally Posted by tsugomaru

The reason why we are able to see light from millions of years ago is because that's how long it took to travel from its source to the Earth.

~Tsugomaru

Note: I didn't read every post, just up until this one.

I agree with that...

The only thing we are looking into the 'past' of is the present of what's up for the future, which makes it seem like the past... but time has not been distorted in any way.

Light doesn't travel through time, I believe. It's just a matter of the length of time it takes something to reach one place to another, in a revealing pattern.

Even if we could see into the past, there's no such thing as altering it...

If you could, altering the past, even just a TINY bit... it could cause devastating results worldwide... or could change for the better, but more likely would not. What is done is done.

[8Shade8]

Here is a theory/question: Would you be able to see different parts of the past based on how you focused your telescope? The fourth dimension is too complex for us to contemplate and play with right now, but under the circumstances that we somehow had the technology to travel faster than the speed of light, and made it light years away from earth and then aimed a telescope at earth, or even our solar system, it would make sense that you could instantly watch hundreds of thousands of years go by, simply by adjusting the focus on your telescope. Zooming in would fast forward time and slowly zooming out would rewind time. Sounds fun right?

[devonin]

From my understanding of time, objective time is objective time. Your subjective time runs at a different speed as your speed approaches and even though we think it can't be done, surpasses the speed of light.

What would have to happen, it seems to me, is that if you moved away from the earth at almost the speed of light, when you stopped, and "fell back into" objective time, it would be the case that X years had passed for you, and a number >X years would pass for everything else. That would technically be time travel into the future because you spent say 1 year in travel and the earth has gone and "aged" 50 years. If you were to look at the earth, you would see earth as it "is now" but because of the relativistic effects of near-lightspeed travel, you would see it seeming subjectively older.

It would follow, to me, that if faster than light travel -were- possible, that yes, you would technically be going "back" in time, but again, once you "fell into" normal objective timespace again, you'd still only see the earth as it "is now" but because of the relativistic effects of greater than lightspeed travel, you would see it seeming subjectively younger.

I still don't buy the idea that you could look physically at the light which has already reflected off the Earth and gone very far away just by catching up to it super fast, and still see anything at all except "some light, quite diffused, coming from thataway" The only way you could see Earth, it seems to me, would be to look at Earth, and you'd only see it as it was "at the time" you looked. No movie versions of Earth's development, you'd have to travel around more at either more than lightspeed to go backwards, or less than lightspeed to go forwards.

[slipstrike0159]

All of this is, for the most part, just an idea because we wouldnt be able to test it out. However ill pose the question again, why does it matter what would happen? It would not be worth all of this effort to 'fly through space going super fast and look back' only to see earth at an earlier state (assuming it worked) unless you could watch life as it starts and develops. Even getting to this impossible point where we got past the old light to tack on the ability to have a telescope that could see microscopic cells and organisms grow would be too much. Even seeing pangea would give us what, very little information at most? The information that we would be able to learn would be not very usefull especially if you figure that once we get this technology we would have advanced to the point where we could figure it out without such a process anyway. Sorry if it seems like im ranting, but i just realized the pointlessness of it all.

Anyway, 'time travel' in the traditional media sense would suggest being able to do or see something in the past/future we didnt already know. This would then bring the point of if you did/saw something remarkable, would it alter anything or would everything stay the same because it was 'supposed' to happen. The biggest problem i have with time travel in the media sense is that if someone years in the future found out how to achieve something like this and the 'butterfly effect' came into to play then from the moment the technology was discovered until the end of time there would be infinite chances for something to go wrong. The worst of which being a catastrophy that ends the world for which all of us now would see as it unfolds thus making 'our' ability to get this technology unavailable or at the very least useless.

[devonin]

Or we're just already living the reality that is the result of all current and future trips into our past.

[Loverofstories]

Originally Posted by devonin

Or we're just already living the reality that is the result of all current and future trips into our past.

"Reality is an illusion. Albeit a very persistent one."
-opinion from a scientist (albert einstein ). Try non-sense. What currently see: stars AS they have shone millions of years ago (from another place made of many small images - if you have uber powerful telescopes you can see them as they are now).

[Afrobean]

Originally Posted by Loverofstories

"Reality is an illusion. Albeit a very persistent one."
-opinion from a scientist (albert einstein ). Try non-sense. What currently see: stars AS they have shone millions of years ago (from another place made of many small images - if you have uber powerful telescopes you can see them as they are now).

You have a telescope that can increase the speed of light to be superluminal speeds? How does that work? Also, how does it speed up the light that is still many light years away? I might be able to believe in a telescope which can increase the speed of the light within it, but how can a telescope speed up light which is far away from it?

[Sol_Solis]

Originally Posted by Afrobean

You have a telescope that can increase the speed of light to be superluminal speeds? How does that work? Also, how does it speed up the light that is still many light years away? I might be able to believe in a telescope which can increase the speed of the light within it, but how can a telescope speed up light which is far away from it?

Umm, as they appeared* - i think thats the correct tense.
Telescope uses curved mirrors! It does wonders, picture hubble as the most powerful with more mirrors and groovy technical things. If I could remember I could handle a more eloquent explanation, but basically you start with a curved mirror, light, and go from there (the light reaches the curved shape and the image becomes intensified and focuses it into a single one - how seemingly simple, we managed to get one IN OUTER SPACE!!!). It has more advanced operation features however, so now one can't say.
http://science.howstuffworks.com/telescope1.htm