Hard Light Productions Forums
Off-Topic Discussion => General Discussion => Topic started by: achtung on October 31, 2007, 04:04:32 pm
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YouTube - Excerpt from documentary (http://www.youtube.com/watch?v=oRWwI61so5Q)
Ronald Mallett's Site (http://www.physics.uconn.edu/~mallett/main/main.htm)
It may be old news but what are your opinions?
I think it's very interesting, if it's possible.
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Light, bending space enough to make it actually swirl around? :wtf:
I don't claim to have the necessary understanding of general theory of relativity when it comes to field equations, but I always thought that relative energy didn't have actual effect on space-time curvature*, and since photons are nothing but relative energy I kinda have my doubts on this interpretation... since the photons have no possible rest stage, they can be considered as pure kinetic energy in the same regard that when objects with a rest mass go faster and faster, they do not collapse into black holes no matter how fast they go.
Although I'm not sure how a continuous beam of light would affect space-time, since it could be viewed as a bar of static energy density... but on the other hand it's still made of photons.
It kinda boils down to the question whether photons just move according to space's curvature along the geodetic straight line, or do they in their part affect the space-time. My intuition would be to say no, they don't affect the curvature of space and time and they just go along, but intuiton is worth nothing in physics. It'd be interesting to see other opinions of that guy's interpretations, but I can't really bother to go and search for them.
The idea about achieving seemingly faster than light movement while moving at sublight speeds in local space-time sounds very plausible - in fact the universe is kinda doing it all the time, that's the reason why the night sky is not as bright as sun - but in that case it's the expansion of the universe which at some point starts making distance between objects and us faster than light can travel, which creates an event horizon of kinds. But interpreting how it would affect time for the object/photon sent into twirling space is a whole another can of worm(hole)s in itself.
For example, if we take an observation point A on geostationary orbit around a black hole, and assume that they send a photon on an interesting trajectory around the black hole, into the swirling space so that it will eventually return to point A, it still won't return to point A before it was sent. It still travels the only path it can at velocity c. The fact that the space around the black hole is so twisted that even catholic priests would be strained by it (into several kilometres long molecular spaghetti threads before being overheated into plasma) doesn't really change the fact that time doesn't go backwards, it only goes forward - although it can stop like it does in event horizon of black holes, from the outside that is.
Even if you take an observation point B opposite to point A and send a photon from A to B so that it travels through swirling time-space close to the event horizon... it will still be the fastest way to contact B from A's location. The fact that the photon's relative velocity in regard to both A and B during it's trip is something else than c due to the fact that the space-time in between moves to some direction doesn't really affect the observers one way or another.
At least that's my interpretation of the matter...
So what gives? I think that probably the only way to time travel is some kind of stasis system which either stops or slows entropia changes in a system, or truly stops or slows the flow of time by stretching time-space. This would cause the effect of traveling to the future, although it would be impossible to get back.
Perhaps the hypothetically most intriguing while physically even remotely plausible time travel method is a combination of a wormhole and a stasis field. The other end of the wormhole would be put into a true stasis field, which would slow the time flow on that end, while the other end would remain put at arbitrary location in normal time flow. This would after some time create a time difference between the ends of the wormhole while being connected to each other, so hypothetically it would then be possible to move from one end to the other.
It would then even be possible to travel from the future into the time when the wormhole was created. But seeing how getting anything of any importance through a wormhole (not to mention making a stable wormhole in the first place) is purely academic question, even this possibility kinda loses it's appeal. :blah:
*actually my vague understanding is that relative energy does affect the energy tensor calculations, but in some point of co-ordinate transformations the relative forms of energy will drop out of the equations when it comes to calculationg mass interactions like gravity, or somesuch smart stuff. Don't ask more, I can't answer... :p
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I must admit, I find the concept of moving around in time very difficult to accept, I can deal with the idea of a difference in progression of Local Time and Perceptive time etc, so the idea that someone who travelled near the speed of light experience less 'time' than someone on a planet-surface, but to get to the point where you are actually going backwards in it? I know it can be done in theory, but personally I have a feeling Time Travel will be one of those things that happens in theory, but takes more energy than the Universe contains to achieve it or something.
It's kind of like Transporter Beams in Star Trek, with people's 'code' being loaded onto a computer and re-assembled on the pad, in theory it's possible, in practice, with current or even forseeable technologies, it'd take millions of years to transmit the complete information on a single human being, since you would have to record the position, speed etc of every single neuron in the brain.
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IMHO, I think it's impossible for once simple reason.
Time & space are connected, right? Moving trough space you are aslo moving trough time...allways forward.
Since there is no negative speed, you can only go forward in time, at a specific pace.
Thus instant "jumps" are not possible, the transitions are gradual.
Traveling BACK in time is flat-out impossible.
At least that's how Isee it. :blah:
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I don't know if it's possible and to be honest i don't want to know it. It would cause too much trouble if you could travel through time.
Possible: Maybe
Good: I don't think so
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I've got to agree with steel on that one >_> However i do not think time travel backwards would be posible as herra stated
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I don't think that backwards time travel is possible, for most of the reasons Herra Tohtori has posted (darn you for taking those ideas straight from my head.... yeah right). Perhaps travel to the future is possible, or the total perspective stopping of time, but the energy required to go back in time doesn't exist in the past. It's like a teleporter. Theoretically, you can't teleport for the simple fact that the required elements/energy does not exist in the area you want to teleport to, it only exists where you are at a certain point in time. Perhaps it is possible to stop time, but that's a different theory altogether.
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This man is proposing travel to the future, not back.
He's proposing travel forward until the machine is deactivated in the future, or back, to when it was first activated.
Not before it was activated, or after it's deactivated.
He's not proposing sending people either, only communications or small particles.
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This man is proposing travel to the future, not back.
Wrong. Listen to it again. This physicist says that time travel backwards is only possible while the portal is open
He's proposing travel forward until the machine is deactivated in the future, or back, to when it was first activated.
Not before it was activated, or after it's deactivated.
Wrong again. See above argument.
He's not proposing sending people either, only communications or small particles.
Wrong yet again. He said information could be sent to the past. Which form of passing information is conjecture.
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This man is proposing travel to the future, not back.
Wrong. Listen to it again. This physicist says that time travel backwards is only possible while the portal is open
He's proposing travel forward until the machine is deactivated in the future, or back, to when it was first activated.
Not before it was activated, or after it's deactivated.
Wrong again. See above argument.
He's not proposing sending people either, only communications or small particles.
Wrong yet again. He said information could be sent to the past. Which form of passing information is conjecture.
The second quote explains the first in those terms. You can only travel within the time period in which the machine is active. You can go back to the instant it is activated, or the moment before it's deactivated. You can not go to any other period. When I say the machine is activated, I mean the portal is open, when I say it's deactivated, I mean the portal is closed.
He mentions something about receiving particles of future experiments in the YouTube video.
I don't think you took the time to read what I said very well.
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i'm pretty sure anything that makes its debut on YouTube.........
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I know it can be done in theory, but personally I have a feeling Time Travel will be one of those things that happens in theory, but takes more energy than the Universe contains to achieve it or something.
bit more than a delorean can muster then ? :p
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:lol: I have to agree with Steel. What if you went back in time, and accidentally killed your parents?
I read somewhere that if you could take to ends of a black hole, twist the thing around, and go in one end, you'd come out the other end either forward or back in time.
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Well one thing that we learned from Douglas Adams is that you can't mess time up or change the course of actions. No matter what you do, including but not limited to killing important political figures or becoming your own grandfather, everything that happened, happens or is going to happen, was going to do that in any case. If you traveld back in time, it just means that further ahead in the time-line your future self has already done it so you're just repeating that. Everything will get right eventually, so don't worry.
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^^ The real trouble with time travel is the grammar. :D
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Just no.
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:lol: I have to agree with Steel. What if you went back in time, and accidentally killed your parents?
I read somewhere that if you could take to ends of a black hole, twist the thing around, and go in one end, you'd come out the other end either forward or back in time.
Now just thinking if you could do that. That is only the linear way of looking at it. If you go back in time and kill your parents, you never were.
But if you think about it, if you went back in time and killed your parents by something you did, you'd never be, but then you never being will mean you never went back in time to kill them in the first place, so they'd still be alive and so would you. :p
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In my opinion, I don't think you would be capable of creating a Grandfather Paradox. Maybe you'd spontaneously combust if you did something like that :lol:
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Nah....the universe would implode. :lol:
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1. Poul Anderson's version: the equations that describe something can have infinite breaks in it. In other words, you travel back you kill your grandparents. Your future self is never born it never exists, but the guy sent back in time without any whatsoever origin still exists.
2. There's a galactic cenzorship law that prevents paradoxons from forming.
3. Multiverse - each time the timeline is altered, the universe branches off with different result on different branches.
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If there EVER was an time machine, we would have known it.
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Not necessarily. It could be that people could start going back in time after the first time machine was made. That's what the documentary snippet in the first post of the topic said.
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This topic is an HLP anomaly in that people who aren't sure what they're talking about discuss physics without getting pounced on and devoured whole by the resident HLP physicists.
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Maybe Swantz is a time traveler and he came back in time and started this thread just for kicks.
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Maybe Swantz is a time traveler and he came back in time and started this thread just for kicks.
:nervous:
At risk of breaking some kind of space-time continuum thing, in the future, this happens:
(http://www.nukelol.com/lolwut/1186146632048.jpg)
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Thor, you two-timing sonofa*****!!
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Quote
This topic is an HLP anomaly in that people who aren't sure what they're talking about discuss physics without getting pounced on and devoured whole by the resident HLP physicists.
This raises an interesting question, how many actual Physicists (as in Natural Sciences faculty, Department of Physics) are there in here in addition for me? And no, Herra Tohtori is not one even though he is good at disguising himself. So at the moment I'll take the full responsibility of not ruining the thread. But I plan to change that status with this post.
That being said, I find another comment said earlier by Flipside quite essential:
I have a feeling Time Travel will be one of those things that happens in theory, but takes more energy than the Universe contains to achieve it or something.
That pretty much sums my thoughts about it.
As a general note, the discussion about time machine will inevitably lead to a question, which, according to my understanding, has been thought about thousands of years:
"Is time a straight line or a closed loop?"
We still cannot answer that question. Note that this thing was also thought about in movies like Terminator I and Terminator II, each representing a different view of it. Even more so, it is again all related to the nature of time itself. When you get the bottom of the things, what the hell is it?
And, I find the topic relatively humorous since researchers are again talking about worm holes in Black Holes yet there is no known way to determine whether one exists inside a Black Hole or not. Besides human kind has not stepped on a extraterrestial planet yet, and vast areas of the ocean crust is still uncharted and it's almost 30 years since human last trotted on the moon - there's some basic research for you. I suggest we concentrate our efforts on that and think about Time Travel later on.
But man can always dream though. Man can dream.
Mika