"Time Travel"

[virus003]

Re: "Time Travel"

You can't make a rocket shuttle go 10000000000000000000000 per second.... Yeah, that's 10 with 21 zeros behind it, AKA the speed of light.

[tsugomaru]

Re: "Time Travel"

You forgot the units. You can make any number seem big if they are measured in units as small or smaller than picometers.

You wouldn't die from the "g-force" unless you went from 0 to light speed within a matter of seconds. The g-force deals with acceleration and one g is 9.8 m/s^2. If you can steadily accelerate to the speed of light, then it shouldn't be a problem. Although you can't feel it, we're traveling through space at well over a hundred kilometers per second, but we don't experience any g's because we're not accelerating much.

~Tsugomaru

[Reach]

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.

Leaping over all of your impossibilities, yes, you could do this.

However, it would never happen, given they are impossibilities. We don't need to get hung up on breaking the speed of light - that's not the real problem (Sure, you can't break the speed of light across the shortest possible distance between two points in flat three-dimensional space, ever, but that doesn't mean it's impossible to find a faster path between those two points and beat light there). The real impossibility is this telescope that will intercept the incredibly old light. There are just too many problems with this, such as the myriad of obstructions in space that would prevent that light from ever getting to your telescope. You'd never be able to get a clear image of the surface of the Earth regardless of the telescope strength.

[Crashfan3]

Re: "Time Travel"

The focus of this confuses me, as I don't have the physics knowledge to give myself a clear explanation.

If we can see bodies of space that existed millions of years before mankind, then given the amazing technology, we should be able to see images of the earth in previous states, but I have no knowledge to back that up. HOWEVER, when the OP spoke of going faster then the speed of light and then stopping to look at the earth. Wouldn't light catch up with you in less than a second once stopped? If so, wouldn't that result in seeing absolutely nothing from the telescope, or images of the earth changing so fast that the human mind couldn't comprehend it happening?

[tsugomaru]

Re: "Time Travel"

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

[Patashu]

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.

yes that's right, and in fact if you can send signals at superluminal speeds back to earth just like you brought your rocket to such a speed you would be able to interact with earth's past - time travel
assuming special relativity holds FTL leads to time travel but it also means you've lost causality, as effect can now precede cause. that's generally not a good thing

[ryanisadouche]

Re: "Time Travel"

Also ponder this. If you were going faster than the speed of light and you looked out a rear window toward the earth that you are speeding away from would you be able to see anything at all while you were moving? Would it be complete darkness because no light is hitting you?

If you looked out the back of your rocket, since you're moving faster then light, the current light wouldn't have reached you yet and you would see what was there in the past. In other words, you'd see your own rocket travelling.

I could be horribly wrong but i think it makes sense given your original theory.

If you focused your super powerful, incredibly accurate telescope back at Earth and looked at it, you'd get -A clear image of Earth right now exactly as you left it- (Or potentially a few seconds after you left it depending I suppose on how long it took you to travel that far away.

I think he meant using the same technology we use today. I wont pretend to know anything about astronomy, but logically it should be common sense. If we look at Star X from Earth, we'll see it as it was in the past n years ago, so if we could hypothetically relocate instantly to Star X, we would see Earth as it was n years ago too.

A telescope could never be made to see Earth as you left it, because in our hypothetic situation we have travelled faster then the light that is present time . A powerful telescope cannot make light speed up and reach its lenses faster, it can only magnify the light that is there at the moment. You would be seeing "old light", as you put it, which could potentially be magnified to see a clear image (given a path of space debris was somehow cleared). It wouldn't be time travel, but just viewing the past.

[Patashu]

Re: "Time Travel"

It wouldn't be time travel, but just viewing the past; you could never interact with anything you saw, since in present time nothing you see exists.

assuming special relativity holds true, if you can travel at superluminal speeds and send a superluminal signal or object you could interact with Earth's past

you need to understand the lorentz transformation for it and why it's a consequence of special relativity but: http://www.theculture.org/rich/sharp...es/000089.html

[gausmaster]

Re: "Time Travel"

assuming special relativity holds true, if you can travel at superluminal speeds and send a superluminal signal or object you could interact with Earth's past

I am by no means an expert at any form of phisics or relativity, but I have a very serious problem with this theory.
I do not belive that any interaction with the past is possible, because I belive that time is stable and consistant. If you were to fire an object at earth at 40X the speed we were traveling it would hit the earth in "real time". If we could comunicate instantaniously with earth then that signal would be going infinity miles an hour, but still you would only be speaking with people on earth in "real time".

[MrRubix]

Re: "Time Travel"

Assuming we could "get ahead of light" and somehow wind up on the other side of old light from years past, I don't think we'd be able to see anything meaningful. I think such light would have been dispersed and manipulated to the point where, even with a powerful telescope, we'd be unable to make out anything at the level of detail required.

We can see the light from things occurring years and years ago -- including things that could have already gone nova by now, but I can't think of an example where we have seen light from the past from an object comparable in size to the earth with the same level of detail. Normally when we look at "old light," they're for large-scale things where any small-scale high-level detail loss via light dispersion is made up for by the sheer AMOUNT of light coming in that makes up the larger image which, from our planet, makes up for a detailed picture. I would assume that for high-level detail, the light from something as tiny as our earth would simply become too dispersed/mangled to see. I'd think of it as trying to view crappy pixel art at high resolution. It's still going to be crappy pixel art.

[Patashu]

Re: "Time Travel"

I am by no means an expert at any form of phisics or relativity, but I have a very serious problem with this theory.

the fact is that if
-special relativity holds true
and
-we can travel at superluminal speeds
then
-we can send signals back in time (time travel)

it is a consequence of the theory deal w/ it

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

[Cavernio]

Re: "Time Travel"

About what you would see if you were moving faster than light, I agree with gausmaster in that you would simply not see the light you're moving away from. Even a beam of light that is 0.0000001mm away from your eye will never be able to reach your eye.
You wouldn't totally see nothing though, because what our eyes pick up is more than the 180 degrees in front of us. We actually see about 10 degrees behind us on either side, http://en.wikipedia.org/wiki/Visual_field , so in those 10 degrees, we'd see light. As a side note, the light we would see if we looked forward would be at least twice as 'bright' because we'd be seeing at least twice as much of it in the same amount of time.

I got into a discussion about this last night, and the other person said that we would be seeing light all distorted, and they gave an example which this morning I realized was incorrect. See, I've been thinking about this problem like light has individual particles. He was thinking about the light simply surrounding us, like, say, water in a stream. If we sit in a stream, we're surrounded by the water, just like if we sit in light, we're surrounded by light. Then he said, pretend we're moving in the stream, swimming downstream with it. At this point, if we're actively swimming in it, we're moving faster than the water is. Yet we're still surrounded by water, there's water touching us behind us. This stumped me for awhile, but there's one serious problem with this: the water changes speeds depending on where it can go. The moment we'd move in the water, the water comes flowing in behind us at a much much faster speed than it flows downstream. Light, however, doesn't do that, because we're saying we'd be travelling faster than its maximum speed.

[John McPain]

Re: "Time Travel"

This is Gausmaster's new account.

Even a beam of light that is 0.0000001mm away from your eye will never be able to reach your eye.
You wouldn't totally see nothing though, because what our eyes pick up is more than the 180 degrees in front of us. We actually see about 10 degrees behind us on either side, http://en.wikipedia.org/wiki/Visual_field , so in those 10 degrees, we'd see light. As a side note, the light we would see if we looked forward would be at least twice as 'bright' because we'd be seeing at least twice as much of it in the same amount of time.

I agree 100%, but what (in your opinion) happens to the light inside of the shuttle?

[Cavernio]

Re: "Time Travel"

The light sources inside the shuttle would still be emitting light that would bounce of the walls and other objects inside it, so there'd still be light 'trapped' inside and moving with you. My very first thought on this is that it would look the same as if we weren't moving, at least once we reached our travelling speed. I don't think we'd get any doppler effect or anything, because relative to the light, our movement hasn't changed at all.
As for light that enters in the shuttle, and then would say, touch the wall...uhhh...I dunno! I don't know enough about the properties of light to answer that really. It light were matter, then it'd get 'stuck' to the wall. But light's not matter, so I dunno. I suppose if it were still to get 'stuck' to the wall, then there'd be a serious problem, wouldn't there be? The shuttle would melt from the heat from all the trapped energy or something.

This seems similar to another problem I was given in my grade 7 science class actually, one which I still don't think was answered properly at the time. (I'm not sure how it's similar, but it made me think of it.)
You have an airtight jar on a scale with a fly sitting on the bottom. Does the scale pick up the weight difference if the fly takes up and is now hovering in the air? Now, I *think* I was told at the time that yes, it did pick up the weight difference, but I have no idea who actually tested this or not. If the jar isn't airtight, than I think it would notice the difference for sure. Also, there's the extra pressure of the air being beat down by the fly onto the scale which you'd have to take into account, right?

[John McPain]

Re: "Time Travel"

Mythbusters did this. They concluded that there is an aberation picked up by the scale but that was caused by momentum differences.
source = http://kwc.org/mythbusters/2007/04/e..._truck_bi.html