This q is in reference to:

http://www.physorg.com/news63371210.html

Let's hypothesize that these experiments / equations work, and time travel is possible. How would one go "backwards" in time? Since the past has already occurred, wouldn't you essentially only be able to go forward in time, and then at most back to your original starting point? e.g. we could go forward as far as we want, but only be able to go back to 2006 (or whenever the machine was created)

Any aspiring physicists on here know the answer?

4/5/2006 12:46:44 PM

Creating an artificial wormhole using the casimir effect, you can theoretically time dilate one end of the wormhole by moving it around at near-light speeds, effectively leaving it in the other opening's "past". Then, you go through the one end and come out in the "past" in the other. You cannot use this to go to a time before the wormhole existed, obviously.

Or maybe that's just out of my ass.

4/5/2006 12:50:44 PM

I thought this was common knowledge? TiVO everything you can about the era in question, then throw the TV (and yourself) into a swimming pool.

4/5/2006 12:59:26 PM

you just need a phone booth and some killer drugs

4/5/2006 1:03:57 PM

^^
it may be, I just didn't know

that whole area of science has always fascinated me, but trying to make $texas to pay bills doesn't leave me much time to catch up on the latest literature

[Edited on April 5, 2006 at 1:07 PM. Reason : ---]

4/5/2006 1:07:08 PM

part of me wants to move this thread

but the rest of me doesn't know where it should go

4/5/2006 1:11:05 PM

its a shit ton more valid than some of the stuff in here

4/5/2006 1:14:34 PM

^^
yeah I couldn't figure out where to put it myself, we don't exactly have a science-related forum

I will cite precedent though, we've had time travel discussion in TSB before

4/5/2006 1:15:19 PM

are we just going to ignore the whole "planet moving through space AND time" thing, where if you jump back 20 years you jump back to where you're standing now, which is obviously not where the planet was then

cause if so

of course you could jump backwards in time
superman did it

4/5/2006 1:23:43 PM

would that be an issue in this case though? going off that article, the area of spacetime being "swirled" would be tied to that physical location on the current Earth, which would itself be moving with the planet. so if you went into the future and roamed around, you would have to come back to that area that would still be tied to the real-life present regardless of where the planet was located

4/5/2006 1:27:26 PM

Quote :

"I thought this was common knowledge? TiVO everything you can about the era in question, then throw the TV (and yourself) into a swimming pool."

ahaha

4/5/2006 1:32:45 PM

just go read a real physist like Richard Gott or Brian Green and save yourself the trouble of reading all the drivel and conjecture that is sure to follow here
http://www.amazon.com/gp/product/0395955637/103-7786519-1942231
http://www.amazon.com/gp/product/0375412883/103-7786519-1942231

or even Hawking should go into enough depth to satisfy you
http://www.amazon.com/gp/product/055380202X/103-7786519-1942231
http://www.amazon.com/gp/product/0553380168/103-7786519-1942231

4/5/2006 1:34:07 PM

well if physics works and particle motion can be determined, then maybe there no free will, the future and past have already happened in a determined way from an objective sense rather than our subjective sense, and if any time travel has happened then the changes are already recorded in history.

4/5/2006 1:38:42 PM

i suppose if you could figure out where the planet was at the time you "land", you could jump accordingly

i'm not reading the article btw

i'm just spouting conjecture

4/5/2006 1:39:35 PM

^^^
yeah I like Greene's stuff, read through Elegant Universe in about 3 days but haven't had the chance to buy Fabric of the Cosmos yet

Hawking is next on my list, his books are hardcore

[Edited on April 5, 2006 at 1:41 PM. Reason : ---]

4/5/2006 1:41:21 PM

theres a philosophy class on time travel called metaphysics. it doesn't actually look at anything philosophers for thousands of years meant by metaphsyics and instead focuses only on time travel movies, but if you are into that sorta thing & clips from the original star trek series, then that class is for you.

4/5/2006 1:46:15 PM

Fabric of the Cosmos goes into a lot more detail and sometimes it makes me fall asleep.

4/5/2006 2:04:15 PM

Ok, before I start ranting, here are my premises.

Big Bang Theory [http://en.wikipedia.org/wiki/Big_Bang]

The Big Bang Theory is the dominant scientific theory about the origin of the universe. According to the big bang, the universe was created sometime between 10 billion and 20 billion years ago from a cosmic explosion that hurled matter and in all directions.

Big Crunch Theory [http://en.wikipedia.org/wiki/Big_Crunch]

If the gravitational attraction of all the matter within the observable horizon is high enough, it could slow the expansion of the universe, and then reverse it. The universe would then contract, with about the same duration as the expansion. Eventually, all matter and energy would be compressed back into a gravitational singularity. It is meaningless to ask what would happen after this, because time would end in this singularity.

Einstein-Rosen bridge Theory [http://www.earth62.net/whatis/enstienbridge.htm]

The Einstein-Rosen bridge is a geometrical property of a black hole that manifests itself in that on the other side of the black hole another set of dimensions has been attached to the one from our universe. This makes passage through this bridge and hence into another universe a mathematical possibility.

Hyperspace [http://en.wikipedia.org/wiki/Hyperspace]

In science fiction, hyperspace is any region or continuum of space co-existing with our own universe (in some cases displaced in an extra spatial dimension) which may be entered using some sort of energy field or space-altering method. While hyperspace is in some way anchored to the normal universe, its properties are not the same as normal space, so traveling in hyperspace is largely inequivalent to traveling in normal space.

1. First we must discover a way to enter a parellel universe through hyperspace (Einstein-Rosen bridge).
2. Second we must discover a way to persist in this parellel universe during and after the Big Crunch. (E=mc^2) If it is possible to alter space-time in this parellel universe, we can convert 'one second' in Universe B into 'the entire span of the creation of the universe itself' (14 billion years) If this is possible, then we can simply wait for Universe A to recreate itself (Big Crunch) -> (Singularity) -> (Big Bang) and then re-enter Universe A from our 'immune Universe B dimension', without the effects of time or space)
3. Thirdly, assuming that our universe is constant and repeating, we could then visit ourselves in high school, and simply be products of a different dimension. Not unlike the light particles that seemed to be in both places at the exact same time.
4. If you think about this theory too much, it is possible to live forever in hyperspace. Assuming that we have the technology to alter space-time within hyperspace. Although, safety is not guarenteed!

http://timetraveler.ytmnd.com/

4/5/2006 2:08:07 PM

If you could go back in time, it would have already happened. The future people already did it and either gave up or are all around us. Who knows?

4/5/2006 3:29:33 PM

88 mph. Duh.


But seriously, I think if you could move faster than the speed of light you'd break relativity and end up at a location before you left.

4/5/2006 3:30:14 PM

there is no theoretical way (that i'm aware of) of going back in time to a point before your "time machine system" has been created, be it a quantum string rotating, a pair of time dialated wormholes, or other systems such as that.

4/5/2006 3:54:46 PM

The same way I came to the past...you must find a parallel earth that exists in another Gravastar outside this universe's or gravastar's domain...upon exiting, there are countless gravastars to enter or one may choose to exit that gravastar. A wormhole and alien technology from the 01000101 beings are all that is needed. However, it is hard to find the exact parallel earth...however, there are an infinite number of Earth's to choose from...some in the past, some in the future.

4/7/2006 2:18:23 PM

I hear you need one of these:

4/7/2006 2:55:15 PM

Well...to go backwards in time. Normally I place my right foot back about a 2 feet, following that I shift my weight to it and then bring the left foot back 4 feet. then I bring the right foot back 4 feet, and continue the process. Time travels, and I go backwards.

4/7/2006 3:14:27 PM

http://www.arxiv.org/PS_cache/gr-qc/pdf/0109/0109035.pdf

4/10/2006 8:35:31 PM

4/10/2006 10:30:24 PM

Warp 9 around the sun.

You could even do that with a Klingon Bird-of-Prey filled with humpback whales and water



[Edited on April 10, 2006 at 10:33 PM. Reason : .]

4/10/2006 10:32:04 PM

if you read heinlein you would know that going really fast around the sun just makes you go faster, not backwards.

4/10/2006 10:45:34 PM

1. Call John Titor.
2.
3. Profit

4/10/2006 10:50:53 PM

daylight savings time travel. duh

4/10/2006 11:12:19 PM

goo backs.

4/10/2006 11:12:54 PM

Quote :

"well if physics works and particle motion can be determined, then maybe there no free will, the future and past have already happened in a determined way from an objective sense rather than our subjective sense, and if any time travel has happened then the changes are already recorded in history."

Or maybe everything is fixed in place and there is still free will. Wrap your mind around that one.

Anyway, arguments I don't want to bother with in here aside, if you really want to know about time-travel then you should plan on taking Dr. Kheyfets' course in General Relativity next fall,

MA 795R 2 ARRANGED HA 144 A KHEYFETS

All you need is calculus III and some time on your hands. Dr. Kheyfets is actually pretty interested in hyperfast travel and knows a fair amount about it's current status ( it's an active branch of physics research with many open questions ).

Personally, I tend to think that time travel may be possible. But, only in a way such that the past is not changed. For example, 12 Monkeys.

4/11/2006 12:14:28 AM

I can travel forward in time.

4/11/2006 1:04:26 AM

^ But sir, can you travel sideways?

4/11/2006 1:15:38 AM

There is a good non-technical blog entry from a Texas string theorist on the modern work on time travel here:
http://aleph.blogspot.com/2002_07_01_aleph_archive.html#79623016

Kheyfets had a grad student working on classical wormhole solutions in GR a few years ago. I don't know what his status is but I thought the project sounded a bit nutty.

Quote :

"well if physics works and particle motion can be determined, then maybe there no free will,...."

My thinking is that modern physics provides evidence against free will and all we have is the illusion of free will. To me it seems neuroscience points towards the brain being described by classical physics. Even if there is some quantum coherence, or random noise, in the brain it doesn't necessarily help you. One can build a deterministic robot in the presence of sometype of stochastic noise.

4/11/2006 1:22:49 AM

Quantum physics/string theory continually points to a "probabilistic" model of the universe, bolstering the uncertainty principle at every turn, which would more lean towards free will.

I'm not up on by neuroscience, but considering how chemically active our biology is, I can see it being very dependent on the lowest level on quantum physics, supporting the idea of "free will."

For the record, I don't think time travel to the past is possible at all. There's too many complications, and Occam's Razor wins out, which would be that it's just not possible. Time travel to the future may be possible, but there wouldn't be much point if you can't send anything back.

[Edited on April 11, 2006 at 1:32 AM. Reason : ]

4/11/2006 1:30:22 AM

^i'm not attacking or anything as i'm not familiar with your posts but are you saying that probabilistic effects are the medium through which the soul interacts with the body leading to free will or that probabilistic effects themselves give rise to free will? or something else entirely?

kinda a related question to any athiests out there, what are your opinions on the existance of free will?

personally, i believe the fact that consciousness and free will are illusions is pretty well established. the exact mechanisms are still unclear, but there is a huge amount of preliminary data and theories. i have yet to meet a neuroscientist that does believe in free will.

4/11/2006 3:41:38 AM

Wait, I forgot to put in the crystals.

4/11/2006 7:13:53 AM

4/11/2006 3:20:55 PM

Quote :

"i'm not attacking or anything as i'm not familiar with your posts but are you saying that probabilistic effects are the medium through which the soul interacts with the body leading to free will or that probabilistic effects themselves give rise to free will? or something else entirely?"

I'm not saying they are, i'm saying they could be. I personally don't even believe in a "soul" and I wouldn't be able to define it. But, if there is free will, there are still mechanisms in our universe that would allow for that.

About the probability thing...

If a particle has a 99.99999999999999999999% chance of moving a certain direction due to gravity, and a .000000000000000000001% chance of moving the opposite direction just because, then if "god" or whoever wanted to make something unlikely, they could take advantage of the probability that something can exist in that unlikely state.

4/11/2006 3:33:54 PM

Quantum branching probably creates the illusion of free will (in this Universe)

4/11/2006 7:51:19 PM