Alcubierre drive research

[peadar1987]

Just a thought I had. I wonder will it ever be possible to use an Alcubierre drive* to fly scientific instruments several million light years away, then look back at the solar system and see what was going on, effectively looking into the past?

Could it work? And what sort of thing could/would we look for?

*Yes, this does presuppose that an Alcubierre drive is possible. That's not what I'm trying to discuss!

[Albert VDS]

An Alcubierre Drive would move you from one point in space to an other.

It doesn't go faster than light and thus can't go back in time.

To give an example what it could do:

You send a radio message to Mars.

Travel to Mars with the Alcubierre Drive.

Wait 7-14 minutes to receive your own message.

[ZetaX]

It would in theory work, but there are many things you won't be able to find out. Seeing even large details like Saturn's rings from 1MLj away is somewhere between very hard and impossible.

Albert VDS: you did not understand the original post. Also, the drive does not magically teleport you to your target but actually moves you (and a spacetime "bubble") to the destination, at a pretty high speed.

[xenomorph555]

Actually I think you don't move but the space around you moves, still I find it unlikely it would send you back in time.

[DeepOdyssey]

Unless you had carried with you entangled particles that you could use to communicate in FTL manner, then it would be worthless.

[ZetaX]

Could you all please at least read the OP¿ The answers of DeepOdyssey and Albert VDS have nothing to do with it.

Also, you can't communicate with entangled particles.

[Albert VDS]

It would in theory work, but there are many things you won't be able to find out. Seeing even large details like Saturn's rings from 1MLj away is somewhere between very hard and impossible.

Albert VDS: you did not understand the original post. Also, the drive does not magically teleport you to your target but actually moves you (and a spacetime "bubble") to the destination, at a pretty high speed.

The Alcubierre Drive doesn't make the spacecraft go faster than light. It contracts and expands the space-time in front and in the back of the "bubble" in which the spacecraft resides.

Effectively moving the space-time in the "bubble". No magic teleporting needed, just a theoretical drive.

The space-time in the "bubble" doesn't change and time doesn't pass differently from before or after it activated.

[DeepOdyssey]

-->ZetaX

Of course that you can send information.

[ZetaX]

-->ZetaX

Of course that you can send information.

No you can't. Read up on it, or read the thread on FTL communications from some weeks ago.

[Xannari Ferrows]

This would work in theory. In the context of Kerbal space, however, it wouldn't. Assuming it works up to its' original expectations, this would be entirely possible. The only problem though is the amount of negative energy you must produce (well, more like extract).

[Mazon Del]

Ok, there seem to be some misconceptions going on here.

OP is asking if we could use an FTL drive (on the assumption that an FTL drive, any drive, possibly an Alcubierre drive, possibly unicorn powered magic) to jump away roughly a hundred light years inside the span of say a couple months. Once there, you'd deploy a massive radio receiver system and/or telescope to look at Earth and try to watch events as they happened roughly a hundred years ago.

To answer this question, yes this would work assuming you did have an FTL drive.

You would have outpaced the light containing the radio and light-images that you sought to receive and would now be able to receive it. As far as WHAT you could see, probably not a whole lot. For an imaging telescope to resolve something like a person over the distance of a hundred+ light years you would need a telescope of stupidly large size. And if you were hoping to watch a specific event, you better hope there were no clouds that day. Unfortunately, there is a rather large portion of human history that can never be recovered this way. Sure, you MIGHT be able to do some fancy games with IR telescopes to see people doing stuff through the clouds, but real color images would be basically lost.

[Albert VDS]

Oh over looked the part were you were looking at light from millions of light years ago. Yes, yoy could do that. Collect your data and travel back.

[peadar1987]

Yeah, I'm not talking about going back in time, just going somewhere that light from a long time ago is only just reaching.

The sort of experiments I was thinking about would be more using a spectrometer to look at what the composition of Mars' atmosphere was in the distant past rather than seeing what Alexander the Great ate for breakfast.

[Tery215]

You would definitely need a really powerful telescope to see anything important..

You'd get to see the solar system a million years ago, not that it's much different. And even then all you would get to see is the solar system at that time specifically. And there would be no humans to look at.

[rtxoff]

That would be some huge telescope to see just earth not talking about anything relevant happening on earth.

[Mazon Del]

Given OP's clarification of looking at Mar's atmosphere way back when, yes you could do it, but it WOULD take a rather massive telescope, or a lot of time. Given that you are an FTL ship, you can play some fancy games and provided your positioning system was good enough, you could move the ship everywhere you need to go to make it pick up the light it needs. It would take for freaking ever, but you could have a 10 meter telescope on your ship, then spend a couple years popping around and have collected all the light you needed to make it seem like a 10kilometer telescope. Still probably not big enough, but you get my point.

[-Velocity-]

Yeah, I'm not talking about going back in time, just going somewhere that light from a long time ago is only just reaching.

The sort of experiments I was thinking about would be more using a spectrometer to look at what the composition of Mars' atmosphere was in the distant past rather than seeing what Alexander the Great ate for breakfast.

Which would allow the sending messages backward in time, which is not a whole lot different than time travel, as the same paradoxes are created.

Warp drives are not going to happen, at least, for violating c. I have a strong feeling that something in nature HAS TO stop them to prevent fundamental violations of causality and consistency (all observers observing the same events). Besides the difficulty in generating the necessary space-time geometry, there was a recent paper that suggested any warp drive would be destroyed if it attempted to go faster than c.

Edited October 13, 2014 by |Velocity|

[rtxoff]

Which would allow the sending messages backward in time, which is not a whole lot different than time travel, as the same paradoxes are created.

Nope, you can only send the message into the future not the past. No paradoxes created through this. Even if you travel with an FTL drive into the past you would also travel into another place. Traveling back with FTL just reverses this. There is no way you could create a paradox beside maybe watching yourself depart after you arrive which won't break causality.

[Mr Shifty]

Which would allow the sending messages backward in time, which is not a whole lot different than time travel, as the same paradoxes are created.

Warp drives are not going to happen, at least, for violating c. I have a strong feeling that something in nature HAS TO stop them to prevent fundamental violations of causality and consistency (all observers observing the same events). Besides the difficulty in generating the necessary space-time geometry, there was a recent paper that suggested any warp drive would be destroyed if it attempted to go faster than c.

No, the A-drive wouldn't violate causality because it wouldn't travel relativistically. You can't send messages backward in time because there's no object travelling faster than light speed to intercept them. The A-drive ship would simply disappear from the universe, then reappear at the destination sometime later. It would be like travelling through a wormhole. Causality violations require space-like trajectories through Minkowski space, but the A-drive ship wouldn't have a trajectory.

Note that accelerating at a constant rate would get you to your destination more quickly (i.e. in less subjective time) then a putative A-drive, and probably use a lot less energy. Travelling 1000 light years at 4x light speed with an A-drive would take 250 years ship-time. Doing it by accelerating at a constant 1g would take a little over 13 years ship-time. The A-drive would really only be useful for short-distance (say, in-system) hops; any long distance travel would require time dilation effects.

Edited October 13, 2014 by Mr Shifty

[Superfluous J]

The simple answer is yes.

If we have the technology to see what a terrestrial planet's atmosphere composition is X light years away, and we had an FTL drive that could take that technology X light years, we could see what all our terrestrial planets' atmospheres were like X years ago.

Though the big questions are all about things millions of years ago, and you'd have to go millions of light years away to see that. The Andromeda Galaxy is roughly 2.5 million light years away, so if you wanted to know what Mars' atmosphere was like even a million years ago, you'd have to go halfway there. I don't think we're even close to the technology that could suss out a terrestrial planet's atmosphere in another galaxy!

But who knows. By the time we can fly there, maybe we will.

[-Velocity-]

Nope, you can only send the message into the future not the past. No paradoxes created through this. Even if you travel with an FTL drive into the past you would also travel into another place. Traveling back with FTL just reverses this. There is no way you could create a paradox beside maybe watching yourself depart after you arrive which won't break causality.

No, the A-drive wouldn't violate causality because it wouldn't travel relativistically. You can't send messages backward in time because there's no object travelling faster than light speed to intercept them. The A-drive ship would simply disappear from the universe, then reappear at the destination sometime later. It would be like travelling through a wormhole. Causality violations require space-like trajectories through Minkowski space, but the A-drive ship wouldn't have a trajectory.

Note that accelerating at a constant rate would get you to your destination more quickly (i.e. in less subjective time) then a putative A-drive, and probably use a lot less energy. Travelling 1000 light years at 4x light speed with an A-drive would take 250 years ship-time. Doing it by accelerating at a constant 1g would take a little over 13 years ship-time. The A-drive would really only be useful for short-distance (say, in-system) hops; any long distance travel would require time dilation effects.

Don't believe me. Believe the educated, Ph.D- holding physicists.

ABSTRACT

Alcubierre recently exhibited a spacetime which, within the framework of general relativity, allows travel at superluminal speeds if matter with a negative energy density can exist, and conjectured that it should be possible to use similar techniques to construct a theory containing closed causal loops and, thus, travel backwards in time. We verify this conjecture by exhibiting a simple modification of Alcubierre’s model, requiring no additional assumptions, in which causal loops are possible. We also note that this mechanism for generating causal loops differs in essential ways from that discovered by Gott involving cosmic strings.

A. E. Everett, “Warp drive and causality,†Phys. Rev. D, vol. 53, no. 12, pp. 7365–7368, Jun. 1996.

Available (for me) at:

http://arxiv.org/abs/0904.0141

Or this one-

ABSTRACT

The General Theory of Relativity has been an extremely successful theory, with a well established experimental footing, at least for weak gravitational fields. Its predictions range from the existence of black holes, gravitational radiation to the cosmological models, predicting a primordial beginning, namely the big-bang. All these solutions have been obtained by first considering a plausible distribution of matter, and through the Einstein field equation, the spacetime metric of the geometry is determined. However, one may solve the Einstein field equation in the reverse direction, namely, one first considers an interesting and exotic spacetime metric, then finds the matter source responsible for the respective geometry. In this manner, it was found that some of these solutions possess a peculiar property, namely 'exotic matter,' involving a stress-energy tensor that violates the null energy condition. These geometries also allow closed timelike curves, with the respective causality violations. These solutions are primarily useful as 'gedanken-experiments' and as a theoretician's probe of the foundations of general relativity, and include traversable wormholes and superluminal 'warp drive' spacetimes. Thus, one may be tempted to denote these geometries as 'exotic' solutions of the Einstein field equation, as they violate the energy conditions and generate closed timelike curves. In this article, in addition to extensively exploring interesting features, in particular, the physical properties and characteristics of these 'exotic spacetimes,' we also analyze other non-trivial general relativistic geometries which generate closed timelike curves.

F. Lobo, "Exotic solutions in General Relativity: Tranversable wormholes and ‘warp drive’ spacetimes.†Classical and Quantum Gravity Research, 1-78, (2008), Nova Sci. Pub. ISBN 978-1-60456-366-5

Available here:

http://arxiv.org/pdf/0710.4474v1.pdf

Or,

We have just reported another episode in the search for failures of the light postulate. Once more the postulate

came out of this trial triumphant. So a strong formulation of it seems somehow encoded in natural laws. Can this

have a deeper meaning? Is it just a limitation to our possibility to travel and communicate or is it required by

consistency in the spacetime fabric? As a matter of fact, any mechanism for superluminal travel can be easily turned

into a time machine and hence lead to the typical causality paradoxes associated with these mind-boggling solutions

of GR. For instance, in [30] it was shown that two warp-drive bubbles traveling in opposite directions can be used to

generate closed timelike curves (see also [5, 10] for causality problems with the existence of two Krasnikov tubes and

a two-wormhole system, respectively).

C. Barceló, S. Finazzi, S. Liberati "On the impossibility of superluminal travel: the warp drive lesson" Second prize entry of the 2009 FQXi essay contest "What is Ultimately Possible in Physics?"

Read here:

http://arxiv.org/pdf/1001.4960v1.pdf

I could find many more references but I tire of doing what you guys should do yourself. Warp drives are a fun fantasy, but a fantasy is all they are.

Edited October 13, 2014 by |Velocity|

[ZetaX]

The discussion continues¿ :-p

Even if you travel with an FTL drive into the past you would also travel into another place. Traveling back with FTL just reverses this.

All physical laws are symmetric in spacetime, i.e. invariant under rotation and translation. Thus if traveling one way moves you back in time, so does traveling in the other direction.

[rtxoff]

The discussion continues¿ :-p

All physical laws are symmetric in spacetime, i.e. invariant under rotation and translation. Thus if traveling one way moves you back in time, so does traveling in the other direction.

And this my friend is not true (it, is but not in this case, cause you are not moving with an FTL drive in a conventional way), it's all relative, travelling with FTL towards Earth will bring you into the future of it, travelling away from it with FTL will bring you into the past of it. Remeber you are not really moving with an FTL drive, you just change your location without really moving fast.

This is something even most Ph.D. don't understand because they lack the ability to imagine it. We can talk about near light speed traveling with an conventional drive to be different but with an hypothetical FTL drive it would be like this.

I am not going to further discuss this because FTL drives are highly hypothetical and further debate about it is just senseless. What cannot be settled by experiment is not worth debating.

The vulcan science directorate has determined that time travel is impossible.

[Mr Shifty]

Warp drives are a fun fantasy, but a fantasy is all they are.

No doubt this is true. It's worth noting, however, that all of the sources you provide state that closed time-like loops can be constructed using the same framework Alcubierre used or that the ability to create them would be a byproduct of the technology. None of them say the drive itself would violate causality. Also note that closed time-like loops do not, in general, require super-luminal travel. (They appear as exact, non-controversial solutions of Einstein's field equations.)

[N_las]

This is something even most Ph.D. don't understand because they lack the ability to imagine it.

We already discussed to death in another thread: FTL communication makes time travel possible. ANY FTL drive allows automatically for FTL communication, so ANY FTL drive will enable time travel.

Your remark about Ph.D.s lacking the ability to imagine the consequences of FTL travel is offensive in the highest degree, considering that you don't have one iota of understanding about relativity and physics in general.

And your remark about a sensless discussion, because there wouldn't be any experiments possible: The idea that FTL travel results in time travel can be easily derived with the axioms of special relativity. And we have unlimited experimental evidence confirming those axioms.

Edited October 14, 2014 by N_las