Time Travel

[Eldritch]

I got the idea for this thread from something Homuncul said in the Future of Mankind thread.

 

If I'm not mistaken, Homuncul expects a time travel machine to be created sometime within the next 10,000 years.

 

So what do you think about the possibility of time travel?

 

I'm inclined to believe it's not possible. I believe it was Stephen Hawking who said that time travel would never be invented, because we've never met anyone from the future. It also raises serious questions about paradoxes that just makes your head spin. The classic example is the time traveller who goes back to the past to kill his grandfather before his father is born. If he kills his grandfather, his father will never be born, nor will the son - so how could he travel back in time to kill the grandfather?

 

Would some unknown factor keep him from ever killing his grandfather? What would happen if he did? Would he just fade away like Michael J. Fox in Back to the Future?

[Ray Jones]

one problem would be .. if you travel back in time then time has to move backwards, while the travelers time has to "move on normal", otherwise he wouldnt exist "anymore" in the past..

[Acrylic]

Ya know, my belief is that you participate in the past if you go back in time...(Think Futurama)...

 

It makes more sense, because you cannot change what has already been said and/or done.

[Datheus]

Well, first. RayJones, that's true. And that's probably the second hardest thing about time travel. First you've got to figure how to break the bonds of time, THEN you have to figure out how to create a sort of time bubble around the traveller.

 

But I don't think TRUE time travel is possible. However, it's possible that there are billions upon billions of parallel universes out there, each at their own moment and time. By breaking through to these parallel universes, it would almost be like time travel. Kind of. Ish.

 

Think "Sliders".

 

An interesting thing to think about. There was a news item (I don't have a source handy, but this *IS* 100% true.) where some scientists shot light through a test chamber. The way the chamber was controlled, the light would shoot through so fast it actually would EXIT the chamber before it even entered.

[SkinWalker]

As to the light faster than itself test, I can tell you it isn't possible. The speed of light, or "c," always travels at a speed of 299,792,458 meters per second (commonly accepted to be 3 x 10^8 m/sec) in a vacuum. It isn't possible to accelerate the velocity of c, but you can slow it down.

 

This is done by passing light through mediums other than a vacuum, such as atmosphere, lenses, gases, minerals, etc., or by reflecting it.

 

Light also changes it's speed when it moves through vacuum to matter or from one type of matter through another. There is an increase in the velocity of c when it leaves denser matter to less dense matter, but it never exceeds 3 x 10^8 m/sec.

 

-------------------------------------------------

 

On to the idea of time travel... but all of the above is important to this concept.

 

Feynman is where I take my information from, and this image comes from his lecture on Space-Time.

 

 

Assuming that the "right now" (region 1) is at point O, but along the X axis, anything that occurs within region 2 can affect point O. This is the affective past. The things in region 3 can be affected by events at point O and this is the affective future. For instance, you can fire a bullet and it travels less than c, but can move to an event in region 3. Points in region 3, however, cannot affect point O.

 

The interesting area about this diagram, and Feynman made quite a point about it in his Space-Time lecture, is that the areas of region 1 (the highlighted areas), which is all of the "right now" and to which O is a point of, can neither affect us nor can we affect it. Because nothing can exceed c (the speed of light). What happens at, say point R, can affect us later, but it cannot possibly affect us before then.

 

For instance, if the Sun explodes "right now," we would never know it until 8 minutes later. If a probe on Mars encountered a problem that had to be solved in 18 minutes or it would be destroyed (like change course from a cliff), it would be destroyed. We wouldn't learn of the problem for 11 minutes and couldn't affect change for a minimum of 11 more.

 

We look at Alpha Centauri and what we see was Alpha Centauri 4 years ago. We can only see it from the light that has come from our past, 4 years ago. Alpha Centauri "now" is an idea or concept of our mind, but not something that is readily definable physically at the moment.

 

Feynman goes on to joke about how there are fortune tellers who make "prophecies" about the future, but there are not even any fortune tellers who can tell us about the present!

 

Particles only move from region 2 to region 3, but not necessarily in straight lines. Particles can split or be deflected, but always in the direction of region 3. Feynman goes on to describe the mathematics of Four Vectors, which is the "three components of momentum, and the energy as the time component, transformed together."

 

Time travel is possible... but only in the way Feynman described.

 

Now Homuncul will undoubtedly go on about his "beloved multiverses," but I only subscribe to the mathematical probability of there being more than one universe given that space is infinite and flat. The next universe, according to the most accepted theory, is something like 10^28 meters away. (or is it 10^26... I always get it confused...).

[Homuncul]

Feynman's view is not that accepted one and above not explaining multiverse a bit more clearly, it doesn't discribe time travel either. But Feynman did actually helped science in both understanding time travel and multiverse. He may be right from one perspective. Like in his work about intractibility of some events. Again this intractibility has much to do with quantum computation through multiverse.

 

Multiverse is here, not 10^28 away. Or how would anything explain what's it all about in quantum interference or Shor's algorythm for factorizing large numbers (and other phenomena)?

 

I also heard of a testing that now is held to discover whether speed of light is trully a constant. That could also be a flaw in Feynman's view. Although it will not be for me to judge.

 

As for time travel I again can't assume anything without first assuming multiverse. Every concept starts with principle. You can't start building any design for time machine first of all not making certain it is possible in principle. That's where all debate is now. In multiverse understanding it's possible, in classical it's not.

 

As for multiverse theories. I'm not for all of them. I'm now for an interpretation given by David Deutsche. I don't whether I'm gonna change my view later.

 

P.S. I even foretell that time machime could be achieved in the next 1000 years.

 

An interesting thing to think about. There was a news item (I don't have a source handy, but this *IS* 100% true.) where some scientists shot light through a test chamber. The way the chamber was controlled, the light would shoot through so fast it actually would EXIT the chamber before it even entered.

 

I guess this was about parallel photons and teleportation. Another evidence for multiverse

 

In the end consider again what do we see, hear and smell of our reality. I'd say we see some few millions in past (when we see stars), we hear some few kilometers in distance, and we smell only few meters away from us. And what is it so hard to see that multiverse is the only consistent explanation we have for things that trouble us. The thing here is that if the best theory we have did not refer to multiverse it would mean that we needed a better theory, cauze there are so many unexplained things in classical physics

[SkinWalker]

Originally posted by Homuncul

Feynman's view is not that accepted one and above not explaining multiverse a bit more clearly, it doesn't discribe time travel either.

 

See, I've been under the impression that Feynman's view on Space-Time was very accepted... then as well as now.

 

His lecture described the "travel" of a particle through time and set some limitations based on the laws of physics. It seems relevant to the idea of a "person" traveling through time since isn't a person merely a collective of particles?

 

There are obvious paradoxes to time travel, but what about being able to "know" what is happening in the "right now?" Could there be a paradox to knowing that information that is occuring somewhere in space at this moment? Say, on a world orbiting Alpha Centauri?

[Homuncul]

Skinwalker:

There are obvious paradoxes to time travel, but what about being able to "know" what is happening in the "right now?" Could there be a paradox to knowing that information that is occuring somewhere in space at this moment? Say, on a world orbiting Alpha Centauri?

 

You actually refer to the "problem" that some scientists see, which there isn't. All that scream and fright comes from a deep intuitive understanding that time flows. But it isn't, and I thought you were a fan of Carl Sagan (he told about it somewhere I think). The only thing that can be questioned here I think is information locality, which has quite recently been proven to be. That means that information never travels nonlocally (disappears somewhere and just appears somewhere else), it's always local (that it "moves"). Again that could not be proven without multiverse (but that is just a side note)

 

So we are surrounded only by past and we still try to catch a glimpse of the future. So the paradox of knowing is that we can't actually tell for sure what's there cuz it's the past that comes to us and in the very moment Alpha Centauri is consumed by it's own black hole in its center, and when we'll go there (we would actually travel in time by doing it) we might not find it in the right place or we'll be like in Planet of the Apes thrown back into our own planet thousands of years after we started. That's no paradox at all, it's just an intrackable task which of course as I said has nothing to do with unpredictability. Furthermore we can predict with high probability today that Alpha Centauri is in it's place by analyzing it's Doplers shift, its surroundings and all.

 

See, I've been under the impression that Feynman's view on Space-Time was very accepted... then as well as now.

 

I guess it's all relative. Multiverse is not yet majorily accepted, although it's true. And Newtonian gravity is still accepted worldwide while it's not true. I said it wasn't that accepted cuz I read works of other famous authors who argued Feynman's view.

[SkinWalker]

Originally posted by Homuncul

So we are surrounded only by past and we still try to catch a glimpse of the future. So the paradox of knowing is that we can't actually tell for sure what's there cuz it's the past that comes to us

 

And no matter where you are on the X axis, any information you receive came from the past. Even if you were standing right next to someone on a battlefield who was shot, it happened in the past. Albeit so soon in the past it appeared to be "now," but by the laws of physics the information was nanoseconds or picoseconds ago. That is why the light cones in the drawing branch away from O into regions 2 and 3 (the shaded areas are outside the light cones).

 

Originally posted by Homuncul

and in the very moment Alpha Centauri is consumed by it's own black hole in its center, and when we'll go there (we would actually travel in time by doing it)

 

We would travel in time simply by not going there as well. We are traveling in time now, but at a relatively uniform rate.

 

Originally posted by Homuncul

we might not find it in the right place or we'll be like in Planet of the Apes thrown back into our own planet thousands of years after we started. That's no paradox at all, it's just an intrackable task which of course as I said has nothing to do with unpredictability.

 

I'm not sure what to make of this, as it seems nonsensical. I'm not trying to be a smarta55, but I read it back a couple times and I'm not sure what your analogy is saying at this point.

 

Originally posted by Homuncul

Furthermore we can predict with high probability today that Alpha Centauri is in it's place by analyzing it's Doplers shift, its surroundings and all.

 

Ahh... but it's doppler shift still represents information that was transmitted from Alpha Centauri 4 years ago. If it went supernova 2 years ago, it's doppler shift would remain unchanged for 2 more years (assuming that the event was sudden and without warning).

 

 

Originally posted by Homuncul

I guess it's all relative. Multiverse is not yet majorily accepted, although it's true.

 

Multiverse (and the many theories that surround it) are not proven. There are several mathematical models that seem to hold up and some that seem to need more work. Deutsch's model isn't the only one and some would say isn't the most likely (I haven't finished his book yet... still working on it). Others would say not likely at all....

 

Feynman's work, however (which is based on Einstein and others) represents mathematical models which have been tested, proven reliable, and offered the ability to make predictions of results to other problems.

 

Originally posted by Homuncul

And Newtonian gravity is still accepted worldwide while it's not true.

 

So you're saying that F = G m_{1m2 / r^2 where neither masses are zero doesn't hold up? We cetainly understand gravity better than we did in Newton's day, but the underlying theories that he developed are still true.}

 

_{Originally posted by Homuncul}

_{I said it wasn't that accepted cuz I read works of other famous authors who argued Feynman's view.}

 

_{His views (as I said, often synonomous with Einstein, et al) are widely accepted. More widely than not, I would say. Authors gain notariety by disagree with the mainstream.}

[Datheus]

I have nothing else to add to the topic. But here's the article that backs up what I said about speeding light up

 

http://www.cnn.com/2000/TECH/space/07/20/speed.of.light.ap

 

 

-edit- And I know it wouldn't allow for time travel:p... Not directly, who can say what doors this could all open. I just thought that it was slightly related and just a neat thing to think about

[SkinWalker]

It was an interesting paper that they wrote, I read the July issue of Nature that it appeared in. They did indicate that much of their work was predicted as superluminal particles are expected. As I understood it, the cesium provided an excited medium, just as other mediums have been used to diminish and nearly "freeze" light.

 

It is the individual particles themselves that are reaching the superluminal speed but as a group.

 

The applications for this could be interesting if information could be transferred at superluminal speed. However, the researchers indicated even in the article you cited that these superluminal speeds would not allow for time travel. Physics isn't my strong point, but I suspect it has to do with the fact that the particles themselves have no mass.

 

There are many theories that wormholes would allow for time travel, but I still have difficulty accepting that one could travel anywhere below the X axis in my drawing. It may very well be that Feynman was wrong as Homuncul suggests, but until I see the tested hypotheses that demonstrate otherwise, I'll trust his work.

[Ray Jones]

the key to affect the speed of light may be gravitiy. although i am not sure what c has to do with time traveling..

[Eldritch]

Since Skin brought up wormholes, I figured I'd use this thread for another topic - black holes.

 

Crushing anything that enters to a zero singularity, some have suggested that black holes actually rip the fabric of spacetime. If it does in fact rip spacetime (which is pure conjecture at this point), what would it open into? A void where physics and time as we know them don't apply? Perhaps time travel would be possible in such a location.

 

Dr. Smoot in his book, Wrinkles in Time (no relation to the fatasy fiction book of the same name), suggests that what he calls "wrinkles" are actually tears in the fabric of spacetime left over from the Big Bang (he uses the metaphor of a tear down the seam of a shirt) and says they're actually quite large. Again, perhaps this is another candidate for time travel.

 

Your thoughts?

[Homuncul]

SkinWalker:

I'm not sure what to make of this, as it seems nonsensical. I'm not trying to be a smarta55, but I read it back a couple times and I'm not sure what your analogy is saying at this point.

 

It was lyrical addition

 

Ahh... but it's doppler shift still represents information that was transmitted from Alpha Centauri 4 years ago. If it went supernova 2 years ago, it's doppler shift would remain unchanged for 2 more years (assuming that the event was sudden and without warning).

 

Still 2 years approximation for such a distance is quitea certain information. It's all probability and in time we would be able toproduce more and more accurate measurements. This is no problem of time travel at all, and of any "other" travel.

 

Feynman's work, however (which is based on Einstein and others) represents mathematical models which have been tested, proven reliable, and offered the ability to make predictions of results to other problems.

 

I agree, and I also said that he may be right from one perspective. Perhaps this is what he says, but there are still many things unecplained and aybe he's only partly right. Let's wait and watch.

 

So you're saying that F = G m_{1m2 / r^2 where neither masses are zero doesn't hold up?}

 

_{It certainly holds up with our scale, but I would like you to try to measure this accurately and compare with Einstein's relativity theory. Or you should try to measure particles with it. It can not be done with it at all.}

 

_{His views (as I said, often synonomous with Einstein, et al) are widely accepted. More widely than not, I would say. Authors gain notariety by disagree with the mainstream.}

 

_{Einatein also said that "god does not play dice" and argued quantum theory when it appeared. It's all might be fallible. Authors get no notariety at all unless they can defend their view adequately.}

 

_RayJones:

_{the key to affect the speed of light may be gravitiy. although i am not sure what c has to do with time traveling..}

 

_{Light is not effected by gravity, it already has been a work of 70 or more years to uncover quantum gravity. The result is almost at 0.}

 

_{It is also argued whether photon has or has no mass}

 

_{And yes I guess that decoherence in the above experiment is quite a problem (that it's hard to tell whether this is the same light). Still I would mention that this experiment is also considered by some as another evidence for multiverse.}

 

_{Eldritch :}

_{Crushing anything that enters to a zero singularity, some have suggested that black holes actually rip the fabric of spacetime. If it does in fact rip spacetime (which is pure conjecture at this point), what would it open into? A void where physics and time as we know them don't apply? Perhaps time travel would be possible in such a location.}

 

_{Yeah but it's again a matter of new technology to enter this wornhole where you'll be sqeezed kilometers before you actually would enter.}

 

_{I also like this pulp wisp unification theory discribing blackholes, speed of light and big bang}

[SkinWalker]

Originally posted by Homuncul

Or you should try to measure particles with it. It can not be done with it at all.

 

If we're talking about massless particles, such as photons, it wouldn't hold up. That has always been the predictable nature of the equation. Still, I do agree that there is significantly more to gravity than that equation, I was just trying to point out that because gravity is more complex than Newton originally thought, didn't mean that Newton was wrong. The theories he had about gravity were right, just incomplete. This is the nature of any science... revision and all.

 

Originally posted by Homuncul

Einstein also said that "god does not play dice" and argued quantum theory when it appeared.

 

But he later embraced quantum theory. After he reviewed the evidence.

 

Originally posted by Homuncul

Authors get no notariety at all unless they can defend their view adequately.

 

Not true, though it should be. Van Daniken is a good example. Rampa and Cayce are two others.

 

Originally posted by Homuncul

Light is not effected by gravity, it already has been a work of 70 or more years to uncover quantum gravity. The result is almost at 0.

 

Isn't this another example of quantum mechanics (again, I remind you that this is FAR from my field... I'm strictly a layman when it comes to physics)? Photons, which comprise light have no mass... but a black hole can bend light with its gravity, which is how we can detect them. Wouldn't this be an example of gravity affecting light?

 

By the way... I'm not necessarily arguing at this point... just discussing

[Homuncul]

SkinWalker:

Isn't this another example of quantum mechanics (again, I remind you that this is FAR from my field... I'm strictly a layman when it comes to physics)? Photons, which comprise light have no mass... but a black hole can bend light with its gravity, which is how we can detect them. Wouldn't this be an example of gravity affecting light?

 

I just try to be certain about terminology. There is no gravity today. Relativity deals with curvature of space-time and quantum mechanics with strong and weak nuclear forces. It is understood that the perfect answer to this disconformity between 2 will become quantm gravity interpretation , but unfortunately nothing happened in scientific world yet to provide such an interpretation. Only some ideas.

 

Light is not necessarily a massive particle according to Relativity although it is questioned, so I can't say for sure. It is the era of microcosm now. Much more discoveries today are made with very small objects than with large ones.

 

Not true, though it should be. Van Daniken is a good example. Rampa and Cayce are two others.

 

I thought Von Daniken and Rampa were no scientists at all. At least there books are majorily accepted (if not) by public and not by scientific world.

[SkinWalker]

Originally posted by Homuncul

I thought Von Daniken and Rampa were no scientists at all. At least there books are majorily accepted (if not) by public and not by scientific world.

 

True.... I was thinking of "acceptance" = book sales and realized that these books sold/still sell like they're made of gold. Yet the information contained is pure fiction.... Tom Clancy novels have more facts in them.

[Homuncul]

Yeah, we are slaves of the pop culture. It says to us what to do, what to wear and furthermore we even like it. But these fiction only drive us further from something factually important. It's sad

 

"the things you own end up owning you", Tyler Darden once

[Alegis]

My opinion on time travel:

 

As it's true time is "slower" high in ze mountains or in space, I don't really believe in time travelling, time and life isn't a friggin videoband so I don't believe in going back in time, life, but going in future, if you could create such a place where time is really slow and eventually step out of it after 10 amusing years and in present there would have passed 15 years..Well it's weird but I really dont believe in going back in time

[Homuncul]

You don't believe, but why? Your position is a bit anthropic. (Maybe you'd like to post in Anthropic Principle thread). So you say that time travel is not possible because of bio-friendly properties of our universe and in some other universe where there is no life it is actually possible, just nothing there can feel the neccessity to do so. But this is a bit absurd. What it has to do with fundamental principles of the universe as space (that can itself expand faster than light), or time which can slow down, or life that can replicate knowledge. They don't exclude each other.

[Master_Keralys]

The biggest problem is that human beings are only capable of perceiving three dimensions. We are aware of the fourth, but unable to fully comprehend it. It's like, imagine if you were a two-dimensional creature. You would be able to perceive the third dimension, but unable to understand it, and unable to see/perceive all of it.

 

The possibility of time travel is limited even within the bounds of quantum physics. The biggest problem is still that the part of time that humans are able to deal with only flows one direction. We know that time must be able to move in more than one direction; after all, in the third dimension we can move three directions. Thus, there are FOUR possible directions to move in space-time. We can'te even comprehend it, much less use it. Which way is "backwards". What are the other two directions?

[Homuncul]

The biggest problem is that human beings are only capable of perceiving three dimensions. We are aware of the fourth, but unable to fully comprehend it. It's like, imagine if you were a two-dimensional creature. You would be able to perceive the third dimension, but unable to understand it, and unable to see/perceive all of it.

 

I deeply disagree with you. We are able to understand 4, 5, 6 dimentions as good as we understand our 3. And what exactly do you mean by saing:"You would be able to perceive the third dimension, but unable to understand it, and unable to see/perceive all of it". It's our difference from other animals that we have the ability to understand things. For us (if not kids we are talking about) percieving means a process of cognition and as a result understanding. If we try to reason about other dimentions we get a glimpse of understanding of them. So what actually stops us. Nothing, and furthermore these dimentions are pretty understood in principle. Regarding the technology to make some use of them in say time travel is only a matter of future developments, not ultimate inability.

 

And time travel is only interesting as a past travel because future travel is no problem at all.

 

The biggest problem is still that the part of time that humans are able to deal with only flows one direction

 

This pseudoproblems always reappears because of the simple misunderstanding that time flows. Time doesn't flow. When you think about that this problem vanishes.

[Master_Keralys]

True, time doesn't really flow. It simply seems to from our perception.

 

I deeply disagree with you. We are able to understand 4, 5, 6 dimentions as good as we understand our 3.

 

What I meant is that most humans are incapable of truly comprehending the way six dimensions would work. We can understand it intuitively, but it's quite literally impossible to visualize. Since our eyes are only able to perceive three dimensions, at least to the best of our knowledge. The other problem is that most other dimensions are invisible to even our most sensitive instuments. The whole curled up dimension idea (Kaluza and Klein came up with that in the 1920's. hah, for all we know, our own dimensions are curled up, just big.).

 

Finally, as far as understanding goes, well, we understand a lot, but there's a lot more to be understood. But we're kind of off topic here.

 

My guess is that the most probable method of truly bridging time is a wormhole developed in a Calabi-Yau space in such a manner that it affects the time dimension instead of one of the other conventional nine (conventional in string theory, that is). But most representations with Calabi-Yau spaces don't include time.

 

Also, Hawking wrote a paper a few years ago on the improbability of time travel, given the looping of light yielding at best, arrival at the same point in time as one left, not early. An infinit voyage yielding arrival at the same point doesn't seem too promising, at least to me.

[amadeus]

If time travel were possible as in moving back in time and moving forward, then time would have to be structured in a different way then we know it. While now, it seems as if each second is going by like...that, what might actually be happening is that each unmeasureable moment of time is recreated over and over again. That would mean that we were always moving through time, so in essence, the human mind is a time machine. Moving back in time would just be to pinpoint the moment you wanted, and reverse the way you are flowing, so you could find that moment and then continue original direction once again.

 

You could subscribe to the half serious theory in Thief of Time by Terry Pratchett. In his book, Wen the Eternally Surprised believes that the world is destroyed and recreated every single moment, so the only appropriate emotion is surprise. With this realization, he is able to find ways to travel through and manipulate time.

[Homuncul]

amadeus:

If time travel were possible as in moving back in time and moving forward, then time would have to be structured in a different way then we know it. While now, it seems as if each second is going by like...that, what might actually be happening is that each unmeasureable moment of time is recreated over and over again. That would mean that we were always moving through time, so in essence, the human mind is a time machine. Moving back in time would just be to pinpoint the moment you wanted, and reverse the way you are flowing, so you could find that moment and then continue original direction once again.

 

Your theory assumes some kind of an anomaly to the world like god por ejemplo. It brings only unneedingly complicated structure of reality. And again and again it's based on the flow of time which is intuitive mistake.

 

Master_Keralys:

We can understand it intuitively, but it's quite literally impossible to visualize

 

Yeah it's intuitive for us to try to visualize. But we don't neccessarily need to do so. Again it's an intuitive mistake. There are different ways of understanding.

 

Also, Hawking wrote a paper a few years ago on the improbability of time travel, given the looping of light yielding at best, arrival at the same point in time as one left, not early. An infinit voyage

 

There is no one way interpretation of that phenomenon. Hawking discribed his way. Others discribe it differently.... guess how... right, multiverse. Have a cookie. Either way it is all far from being even relatively certain.