Time Travel?

[Tufelhunden]

I was just wondering what everyone's thoughts and theories were. I am really not expecting anything viable; I want to hear everything, from the most outrageous theories to the more subtle ones. The reason being is that there has been a steady increase in publications in physics journals which I look at frm time to time, and I have to admit that as far out as this seems I am getting more and more fascinated by this.

The most convincing theory I read was proposed as thus:

A two chambered room with a set of high density parallel metal plates in each chamber, for a total of four plates (two in each chamber). If then possible to harness enough electricity (energy) to be transmitted through this, a rip in the electromagnetic space-time fabric can be achieved. If achieved in both chambers, a worm-hole (I think its technical term is an Einsteinian Bridge) can be achieved and maintained. If one of these chambers can then be taken at speeds approximate to the speed of light, what goes in one wormhole and out the other technically has travelled through time, because as Einstein's relativity states: time travels slower for a body in motion. The limiting technologies here are: harnessing of enough energy to rip into space-time and propogation of high speeds.

Other theories I remember involved the maintenance of black holes: In a black hole there is a point called an "event horizon" where I think that a particle trapped here would be smashed into such oblivion (due something to the effect of infinite gravity) that its density reaches infinity. Some astro-physicists are now coming forward and saying that this "point" (event horizon) is more oriented as a ring (like a donut) and thus if a particle were to pass through, it ends up in another point of the universe.

I know this stuff is way out there, and I'm sure my physics-grammer needs to be maintained, but I was just wondering what some of my fellow geeks thought.

[Tufelhunden]

By the way I think this rambling has something to do with me watching the new Denzel Washington movie and how it reminded me of some of the conversations and readings I had in the past...

[antiquity]

I saw a program about the Philadelphia experiment. Very interesting. http://en.wikipedia.org/wiki/Philadelphia_Experiment

[carl]

We can already look back in time to recognize light waves that were produced by the Big Bang - that's quite a few years ago and a start. Now we need to be able to fine tune the telescopes to see waves produced by occurrences that happened on Earth. It's not time travel, but close - a poor man's time travel. Safer too.
Actually if String Theory does prove that there are infinite parallel occurrences happening along with ours then one must be the same as ours, but just at a different time. No black hole travel necessary, we just need to be able to jump into it (and back?).
Bottom line is to stick to movies and science fiction books.
My opinion,
Carl

[Wise Young]

There is a good discussion about time travel by Carl Sagan, particularly concerning the Hawking's chronological protection conjecture [which holds that the laws of physics disallow time machines].

I personally think that time travel is also very interesting from a psychological or biological point of view. Time passes because we have memory. If a person loses ability to make new memories, the future disappears for that person and the future stops happening for the person. On the other hand, if a person loses memories, the past disappears.

Wise.


http://www.pbs.org/wgbh/nova/time/sagan.html
Sagan: The grandfather paradox is a very simple, science-fiction-based apparent inconsistency at the very heart of the idea of time travel into the past. It's very simply that you travel into the past and murder your own grandfather before he sires your mother or your father, and where does that then leave you? Do you instantly pop out of existence because you were never made? Or are you in a new causality scheme in which, since you are there you are there, and the events in the future leading to your adult life are now very different? The heart of the paradox is the apparent existence of you, the murderer of your own grandfather, when the very act of you murdering your own grandfather eliminates the possibility of you ever coming into existence.

Among the claimed solutions are that you can't murder your grandfather. You shoot him, but at the critical moment he bends over to tie his shoelace, or the gun jams, or somehow nature contrives to prevent the act that interrupts the causality scheme leading to your own existence.

NOVA: Do you find it easy to believe the world might work that way—that is, self-consistently—or do you think it's more likely that that there are parallel universes?

Sagan: It's still somewhat of a heretical ideal to suggest that every interference with an event in the past leads to a fork, a branch in causality. You have two equally valid universes: one, the one that we all know and love, and the other, which is brought about by the act of time travel. I know the idea of the universe having to work out a self-consistent causality is appealing to a great many physicists, but I don't find the argument for it so compelling. I think inconsistencies might very well be consistent with the universe.

NOVA: As a physicist, what do you make of Stephen Hawking's chronological protection conjecture [which holds that the laws of physics disallow time machines]?

Sagan: There have been some toy experiments in which, at just the moment that the time machine is actuated, the universe conspires to blow it up, which has led Hawking and others to conclude that nature will contrive it so that time travel never in fact occurs. But no one actually knows that this is the case, and it cannot be known until we have a full theory of quantum gravity, which we do not seem to be on the verge of yet.

One of Hawking's arguments in the conjecture is that we are not awash in thousands of time travelers from the future, and therefore time travel is impossible. This argument I find very dubious, and it reminds me very much of the argument that there cannot be intelligences elsewhere in space, because otherwise the Earth would be awash in aliens. I can think half a dozen ways in which we could not be awash in time travelers, and still time travel is possible.

NOVA: Such as?

Sagan: First of all, it might be that you can build a time machine to go into the future, but not into the past, and we don't know about it because we haven't yet invented that time machine. Secondly, it might be that time travel into the past is possible, but they haven't gotten to our time yet, they're very far in the future and the further back in time you go, the more expensive it is. Thirdly, maybe backward time travel is possible, but only up to the moment that time travel is invented. We haven't invented it yet, so they can't come to us. They can come to as far back as whatever it would be, say A.D. 2300, but not further back in time.

Then there's the possibility that they're here alright, but we don't see them. They have perfect invisibility cloaks or something. If they have such highly developed technology, then why not? Then there's the possibility that they're here and we do see them, but we call them something else—UFOs or ghosts or hobgoblins or fairies or something like that. Finally, there's the possibility that time travel is perfectly possible, but it requires a great advance in our technology, and human civilization will destroy itself before time travelers invent it.

I'm sure there are other possibilities as well, but if you just think of that range of possibilities, I don't think the fact that we're not obviously being visited by time travelers shows that time travel is impossible.

[Jeff B]

I had a dream that I had traveled back in time and realized that I needed to let my old self know that I (he?) had to avoid getting in the accident that resulted in my SCI. Unfortunately I couldn’t find my old self and was running out of time before I would get pulled back to the future so I tried to leave a note. I couldn’t find a pen either so I cut my finger in desperation and started writing in blood. Unfortunately I always have trouble reading and writing in dreams (which is quite common) so whatever I tried to write kept coming out garbled. It was all very frantic and frustrating.

[Adrian]

If it were possible to travel back in time, say to just before you had your accident, would you travel back with the knowledge that you were about to have an accident or would you arrive at that point in time having the same state of knowledge that you had the first time you were at that point in time, i.e. not knowing that you were about to have an accident? That question raises the question of whether you can travel back through time and arrive at a different point in time at the same age as you were before you set off on your travel and if not are you traveling through time or reversing time and are those the same things?
If you could not travel back in time but you could travel forward, would you travel forward to a point in time when your SCI could be cured even if you arrived at that point in time at the same age you would be if you had not travelled there faster than waiting to get there naturally? This is part o f the question of can you travel through time without getting older at the speed you are travelling at and thus would it ever be possible to travel forward in time beyond your life expectancy?

[Wise Young]

If it were possible to travel back in time, say to just before you had your accident, would you travel back with the knowledge that you were about to have an accident or would you arrive at that point in time having the same state of knowledge that you had the first time you were at that point in time, i.e. not knowing that you were about to have an accident? That question raises the question of whether you can travel back through time and arrive at a different point in time at the same age as you were before you set off on your travel and if not are you traveling through time or reversing time and are those the same things?
If you could not travel back in time but you could travel forward, would you travel forward to a point in time when your SCI could be cured even if you arrived at that point in time at the same age you would be if you had not travelled there faster than waiting to get there naturally? This is part o f the question of can you travel through time without getting older at the speed you are travelling at and thus would it ever be possible to travel forward in time beyond your life expectancy?

There are two ways to travel forward in time. One is to go into deep freeze for 100 years. The other is to travel at close to light speed.

Wise.

[Jeff B]

The worst part about the deep freeze method is that it takes about a month for your testicles to descend again after they thaw you out.

Also, your grandkids will have blown through all your savings and investments so you will also be poor.

[Buck503]

I was told a long time ago, by my grandfather, that if I ever go
back in time, "don't step on anything; because even the tiniest
change could alter the future in ways you can't imagine".

So, keep that in mind.

[antiquity]

I wouldn't mind knowing the future but I'd prefer to travel back in time, about 3000 years.

[rdf]

Hawking: Humans must colonize other planets (http://www.cnn.com/2006/TECH/space/11/30/space.hawking.reut/index.html)

LONDON, England (Reuters) -- Humans must colonize planets in other solar systems traveling there using "Star Trek"-style propulsion or face extinction, renowned British cosmologist Stephen Hawking said on Thursday.

Referring to complex theories and the speed of light, Hawking, the wheel-chair bound Cambridge University physicist, told BBC radio that theoretical advances could revolutionize the velocity of space travel and make such colonies possible.

"Sooner or later disasters such as an asteroid collision or a nuclear war could wipe us all out," said Professor Hawking, who was crippled by a muscle disease at the age of 21 and who speaks through a computerized voice synthesizer.

"But once we spread out into space and establish independent colonies, our future should be safe," said Hawking, who was due to receive the world's oldest award for scientific achievement, the Copley medal, from Britain's Royal Society on Thursday.

Excerpts:
"Science fiction has developed the idea of warp drive, which takes you instantly to your destination," said.

"Unfortunately, this would violate the scientific law which says that nothing can travel faster than light."

However, by using "matter/antimatter annihilation", velocities just below the speed of light could be reached, making it possible to reach the next star in about six years.

"It wouldn't seem so long for those on board," he said.

More (http://www.cnn.com/2006/TECH/space/11/30/space.hawking.reut/index.html)

---

matter/antimatter annihilation is very interesting. I've read some on it a few years back when it caught my eye, as it played a big part in how the universe began. Antimatter holds the answers to not only future space travel, but in the future hopefully unlimited energy for everybody here on earth.

[Wise Young]

I wouldn't mind knowing the future but I'd prefer to travel back in time, about 3000 years.

Dear Antiquity (maybe better than Seneca), I think that travelling back in time is an unlikely scenario. However, what you can do is to create a time that you would be happy to live in. Isn't that a legitimate and honorable goal, that your forbears would be proud of? They had their problems in the times of Nefertiti, which you remind me of... Source (http://en.wikipedia.org/wiki/Nefertiti)) but of course you are much more beautiful than Nefertiti.

You have the power to change the world.

Wise.

[Mike C]

I´m not at all sure that the light speed barrier cannot be surpassed. Haven´t there already been experiments showing faster than lightspeed?

http://en.wikipedia.org/wiki/Faster-than-light

[Tufelhunden]

I´m not at all sure that the light speed barrier cannot be surpassed. Haven´t there already been experiments showing faster than lightspeed?

http://en.wikipedia.org/wiki/Faster-than-light

That would be like switching off a light and being back in your chair before the lights went off. If we use light as the medium of time (meaning as you see images unfold before your eyes, you perceive time passing) then this would technically constitute going forward in time.

[antiquity]

Dear Antiquity (maybe better than Seneca), I think that travelling back in time is an unlikely scenario. However, what you can do is to create a time that you would be happy to live in. Isn't that a legitimate and honorable goal, that your forbears would be proud of? They had their problems in the times of Nefertiti, which you remind me of... Source (http://en.wikipedia.org/wiki/Nefertiti)) but of course you are much more beautiful than Nefertiti.

You have the power to change the world.

Wise.

LOL thank you Wisey. I know that time travel isn't possible although I'm sure the military has explored it. And yes, I would take ancient egypt over the modern era any day!

[Juke_spin]

LOL thank you Wisey. I know that time travel isn't possible although I'm sure the military has explored it. And yes, I would take ancient egypt over the modern era any day!
Of course you're assuming you'd be amongst the nobility, i.e. one of those having the monuments built for them rather than one of those doing the building.:thinking::rolleyes:

[antiquity]

Of course you're assuming you'd be amongst the nobility, i.e. one of those having the monuments built for them rather than one of those doing the building.:thinking::rolleyes:

Well, you assumed wrong lol. I've studied ancient history so I have a realistic view of their culture and social structure.

[Juke_spin]

Well, you assumed wrong lol. I've studied ancient history so I have a realistic view of their culture and social structure.
I was very curious how you'd respond to my dig and this is interesting. You studied so you know that the classes basically boiled down to the slaves, artisans, priesthood and aristocracy.

If you weren't assuming/planing on winding up part of the nobility then what class were you planning on being a part of? Or were you projecting yourself into this "alien" culture as a just arrived time traveler, as yourself?:thinking::D

[darkeyed_daisy]

I would be happy just going back to the fifties. But if given the choice to go back farther....I would definately have gone back to the 1800's. Of course, I would still want to be from my same family. I have always felt I was born in the wrong century.

[antiquity]

I was very curious how you'd respond to my dig and this is interesting. You studied so you know that the classes basically boiled down to the slaves, artisans, priesthood and aristocracy.

If you weren't assuming/planing on winding up part of the nobility then what class were you planning on being a part of? Or were you projecting yourself into this "alien" culture as a just arrived time traveler, as yourself?:thinking::D

LOL, well I don't agree with your assessment but I won't comment further since I'm not sure if these are honest questions with the intention of starting a dialogue or just digs intended to rile and mock.

[Juke_spin]

LOL, well I don't agree with your assessment but I won't comment further since I'm not sure if these are honest questions with the intention of starting a dialogue or just digs intended to rile and mock.
LOL, I'm not surprised at the :tape: and, since the nonresponse was somewhat anticipated, will leave the confusion unresolved.;)

Steve

P.S. "rile & mock"! Really!? In the Science and Technology forum?

[antiquity]

LOL, I'm not surprised at the :tape: and, since the nonresponse was somewhat anticipated, will leave the confusion unresolved.;)

Steve

P.S. "rile & mock"! Really!? In the Science and Technology forum?

Tsk, tsk Juke, now why would you ask if "the nonresponse was somewhat anticipated." I'm sure you could devise better ways to use your time or did the possibility that I would respond with fodder for your amusement make it more than worth the effort. :nono::D

[Juke_spin]

Tsk, tsk Juke, now why would you ask if "the nonresponse was somewhat anticipated." I'm sure you could devise better ways to use your time or did the possibility that I would respond with fodder for your amusement make it more than worth the effort. :nono::D
The contrary, I was hoping for a stimulating discussion to take off on just how you imagined yourself in ancient Egypt. That you've often ignored my input led me to anticipate a nonresponse. Can I really be that hard to read or is it, at least in part, you?

Steve

[antiquity]

The contrary, I was hoping for a stimulating discussion to take off on just how you imagined yourself in ancient Egypt. That you've often ignored my input led me to anticipate a nonresponse. Can I really be that hard to read or is it, at least in part, you?

Steve

Oh really, and the way you start stimulating conversations is with "digs?" Your words, not mine. Do I "often ignore your input?" I wasn't aware. As for you being hard to read, I must admit that I haven't invested much time exploring your personality, so perhaps it is me. :)

[Juke_spin]

Oh really, and the way you start stimulating conversations is with "digs?" Your words, not mine. Do I "often ignore your input?" I wasn't aware.
The original question was half sincere and half "dig". And yes, you have often ignored my input, although I did appreciate the openness with which you replied to my recent post to the "Cure" thread. Sadly, it was the exception to a general rule/picture developed in other threads.

Steve

P.M. LOL on the timing your edit and my post.

[antiquity]

The original question was half sincere and half "dig". And yes, you have often ignored my input, although I did appreciate the openness with which you replied to my recent post to the "Cure" thread. Sadly, it was the exception to a general rule/picture developed in other threads.

Steve

P.M. LOL on the timing your edit and my post.

Awwww, my intention isn't/wasn't to ignore your input. I'm actually flattered that you care. So the purpose of the "dig" was to ensure a response? With the rate at which discussions deteriorate in these forums and the preferred method of exchange is sarcasm or condenscension, I'll opt to say less rather than more unless, of course, a rapport has already been established. ;)

[Wise Young]

Steve, I have great respect for both you and Antiquity. I have actually met Antiquity, think that she is beautiful, and have never yet beaten her in internet scrabble. She has indicated publicly several times her preference for a more ancient time. While I kid her about Nefertiti, my reference is just fanciful on my part. Wise.


LOL thank you Wisey. I know that time travel isn't possible although I'm sure the military has explored it. And yes, I would take ancient egypt over the modern era any day!

Antiquity, to tell you the truth, I much prefer the modern era. Why? First, in the current age, one can more easily raise oneself from commoner status by the dint of one's ability, as opposed to birth, wealth, or power. Second, there is simply no better time to exist as a scientist. The expansion knowledge in the past decade alone is greater than all the knowledge accumulated in human history. To be able to witness, much less participate in creating, the burgeoning understanding of nature and the universe is an honor and a pleasure. Third, although our current age is by no means perfect or even admirable, the problems of the world give meaning to our existence by allowing us to try to make the world better. Unless there is a break in human history and a failure to hand our knowledge to succeeding generations, the cure for spinal cord injury will happen only once in human history. Finally, it is still an age when one can be still be heroic, noble, and passionate about important causes, where one can make a real difference.

Wise.

[StarLord]

First, with regard to travel at speeds greater than the speed of light.

This is of course based upon the Special Theory of Relativity (STR). STP is defined on a space with curvature (Riemannian and Ricci) = 0. That is to say, flat space-time.

Within the General Theory of Relativity (GTR) technically there is no such restriction. In fact, a metric that demonstrates the ability to travel faster than the speed of light was proposed by Miguel Alcubrierre (arXiv:gr-qc/0009013 (http://sci.rutgers.edu/abs/gr-qc/0009013)) in a paper appropriately entitled "The warp drive: hyper-fast travel within general relativity". In this solution one can indeed travel faster than the speed of light (the speed is arbitrary) however it requires "exotic" matter. This is matter with negative energy (not to be confused with anti-matter). Combining "exotic" matter and regular matter would simply cause both to disappear. (A comment on matter anti-matter propulsion: such a violent explosion would produce great energies but would very likely not induce super-luminal velocities because it would occur within flat space-time and thus be subject to STR.)

Secondly, with regard to time travel. The principal requirement is that time must be a physical dimension. This is normally taken to be true in GTR, but it doesn't appear in quantum mechanics (there is no time operator) so, in a certain sense, time lacks physicality. Indeed, even in GTR, time as a physical reality is uncertain. Time ultimately is a measure of motion, the question is: The motion of what? Usually this is answered by invoking the concept of a clock, that is, a mechanism to measure time. In reality it measures a system moving with a constant speed. Thus, time is a derived concept, much like energy (with which it is dual). Also, the notion of time travel within Quantum Mechanics (QM) is very problematical. If one were actually able to travel back in time qunatum mechanics would conspire to render it impossible. It is virtually impossible to recreate the past within Quantum Mechanics due to the probablistic nature of QM. The probabilty of recreating the precise structure of some past Universe with all of the atoms precisely in place would put a sever strain on the Uncertainty Principle. Therefore, although time travel has a romantic appeal, it's not likely to occur.

[Tufelhunden]

It is virtually impossible to recreate the past within Quantum Mechanics due to the probablistic nature of QM. The probabilty of recreating the precise structure of some past Universe with all of the atoms precisely in place would put a sever strain on the Uncertainty Principle. Therefore, although time travel has a romantic appeal, it's not likely to occur.

What about implementing a Heisenberg Compensator? J/K...Awesome and informative post, StarLord. However, the link you provided to the paper doesn't work...I'm actually interested in browsing it.

[Imight]

www.johntitor.com

=)

[StarLord]

Sorry, the url is:

http://arxiv.org/abs/gr-qc/0009013

This is the Los Alamos ArXiv website

The title of the paper is: "The warp drive: hyper-fast travel within general relativity" by Miguel Alcubierre.

Yeah, I suppose you'd need something like the Heisenberg compensator but you'll have to talk to Gene Roddenberry.