Has anybody that about time travel? I was thinking about it and I don't think that time travel should not exsist because just being in a spot, actually, just enter the past and not doing anything will cause a time paradox. Any comments.
Posted by MattP (Member # 10495) on :
OK, kat was right. Sorry Rabbit, you lose this one. Posted by TomDavidson (Member # 124) on :
There are lots of reasons why time travel to the past is pretty much impossible.
Posted by Kwea (Member # 2199) on :
Which is why it's called the Past. Posted by T:man (Member # 11614) on :
What paradox, if you go back in time than you can' change anything. Right now is the past, therefore everything is already set.
Posted by rivka (Member # 4859) on :
quote:Originally posted by MattP: OK, kat was right. Sorry Rabbit, you lose this one.
*snicker*
Posted by TomDavidson (Member # 124) on :
quote:if you go back in time than you can' change anything
Unless you mean that you will have already been back in time, and thus the changes you made by going back were already made, I'm not sure you've thought that through. Merely by breathing and standing in one spot while emitting heat, you are making changes.
Posted by Blayne Bradley (Member # 8565) on :
I think being able to travel back in time while problematic is entirely mathematically speaking within the realm of the possible and paradox's resolvable.
Posted by Darth_Mauve (Member # 4709) on :
Except the speed of light limitation.
The planet we are on is moving quite fast around the sun. The sun is spinning quite fast around the center of the Milky-way galaxy.
The Galaxy is zooming away from the center of the universe at speed that are quite astounding.
Now, if you were to go back in time you would also have to go back in space, or find yourself pretty quickly in vacuum.
Asimov figured that traveling back in time more than a few days, and remaining on earth, will require traveling faster than the speed of light, unless of course it takes you longer, relatively speaking, to travel back in time than the time that you are backtracking. (Say you want to go back 500 years, you will age 500 years in the process).
Posted by rivka (Member # 4859) on :
Paradox, schmaradox. Wormholes!
Posted by Blayne Bradley (Member # 8565) on :
Except Darth were not reversing time simply jumping to earlier (or later) time.
Posted by TomDavidson (Member # 124) on :
That's actually the point. If you were reversing time, you wouldn't have to change your spatial reference. Since you're jumping in time, though, it's important to note that the Earth won't be anywhere near where you last left it, depending on the frame of reference you're using for your position.
Posted by Lyrhawn (Member # 7039) on :
quote:Originally posted by rivka: Paradox, schmaradox. Wormholes!
Yeah but the wormhole has to pass through a solar flare, and even then it's not very specific unless you have that crazy alien technology that scans solar flares ahead of time so you can target where you want to go.
Posted by rivka (Member # 4859) on :
I wasn't actually referencing Stargate, although I imagine they may have taken Kip Thorne's research under advisement when they wrote those episodes.
Posted by Slim (Member # 2334) on :
quote:Originally posted by L_mustang94: Has anybody that[sic] about time travel? I was thinking about it and I don't think that time travel should not exsist[sic] because just being in a spot, actually, just enter the past and not doing anything will cause a time paradox. Any comments.
So, you think that time travel should exist because going into the past and not doing anything will create a paradox? Huh? Or did you not mean to have a double-negative there? ...But isn't not doing anything the way to not make a paradox? I'm just overall confused by your post, sorry.
It all depends on how the universe deals with paradoxes. If I go back and do something, is it something that was just always written in the past? Does an alternate universe open up? Does the written pages end chapter 134 by saying, "Then Slim went back in time," and chapter 135 begins a repetition of what happened in 134 but with another me? Will the universe explode if I kill my grandfather, or will the universe physically prevent me from doing anything that will make it so that I won't make the voyage through time in the first place?
The only way to really know is by thorough testing. Posted by Sean Monahan (Member # 9334) on :
quote:Originally posted by Darth_Mauve: Except the speed of light limitation.
The planet we are on is moving quite fast around the sun. The sun is spinning quite fast around the center of the Milky-way galaxy.
The Galaxy is zooming away from the center of the universe at speed that are quite astounding.
Now, if you were to go back in time you would also have to go back in space, or find yourself pretty quickly in vacuum.
I think what you're suggesting here is that there is an absolute coordinate system in the universe, such that if you are at point P when you travel back in time, then you will appear at point P in the past; but an absolute coordinate system for the universe is not a foregone conclusion.
Posted by Telperion the Silver (Member # 6074) on :
You guys ever see "Millennium"?
Paradox! Time Quake approaching! Course 7!
Posted by anti_maven (Member # 9789) on :
A paradox? A paradox! A most ingenious paradox! We've quips and quibbles heard in flocks, But none to beat this paradox!
Ooh I say, I came over all queer...
Posted by Javert (Member # 3076) on :
quote:Originally posted by TomDavidson: That's actually the point. If you were reversing time, you wouldn't have to change your spatial reference. Since you're jumping in time, though, it's important to note that the Earth won't be anywhere near where you last left it, depending on the frame of reference you're using for your position.
*sigh*
That's what the phonebox is for, Tom. Use your head!
Posted by T:man (Member # 11614) on :
quote:Originally posted by TomDavidson:
quote:if you go back in time than you can' change anything
Unless you mean that you will have already been back in time, and thus the changes you made by going back were already made, I'm not sure you've thought that through. Merely by breathing and standing in one spot while emitting heat, you are making changes.
Technically even if you had released heat that would have already happened. So you were just playing it out exactly how it happened.
Posted by mr_porteiro_head (Member # 4644) on :
Unless it's not.
Posted by Epictetus (Member # 6235) on :
The way I figure it, if the future is always unknown and the past is always known, we're just facing the wrong way.
Posted by Dan_raven (Member # 3383) on :
quote:
quote: Originally posted by Darth_Mauve: Except the speed of light limitation.
The planet we are on is moving quite fast around the sun. The sun is spinning quite fast around the center of the Milky-way galaxy.
The Galaxy is zooming away from the center of the universe at speed that are quite astounding.
Now, if you were to go back in time you would also have to go back in space, or find yourself pretty quickly in vacuum.
I think what you're suggesting here is that there is an absolute coordinate system in the universe, such that if you are at point P when you travel back in time, then you will appear at point P in the past; but an absolute coordinate system for the universe is not a foregone conclusion.
Actually the assumption of a absolute coordinate system is made when any time travel discussion is taken seriously. Point P is a point in space with a location on an XYZ axis in 3 dimensional space, but it also has a position in Time--4th dimensional space. Whenever person A moves from point P to point Q in 3 dimensional space, they also move in 4th dimensional space (the time it takes to get from P to Q is there speed).
Time travel theory says that it should be just as easy to go from P to Q in space as it would be to go from Friday to Monday, either backwards or forwards. Just as you could walk from P to Q or Q to P.
So I am standing in a room, and want to walk back one minute, if there is no Absolute Coordinate System, what space will I follow? Will I walk backwards along the path that all of my sub-atomic particles did? If so, then there is no change, no paradox, and no memory of the time travel since my backtracking erased the memories created--they were undone.
Posted by L_mustang94 (Member # 11693) on :
Could you pu that in English please.
Posted by King of Men (Member # 6684) on :
quote:Originally posted by Darth_Mauve: Asimov figured that traveling back in time more than a few days, and remaining on earth, will require traveling faster than the speed of light, unless of course it takes you longer, relatively speaking, to travel back in time than the time that you are backtracking. (Say you want to go back 500 years, you will age 500 years in the process).
Since time travel is equivalent to FTL travel anyway, this is not much of a limitation.
Posted by Blayne Bradley (Member # 8565) on :
special and general relativity from what I have read more or less state that there is no absolute coordinate system and that your location is more or less irrelevant, if your on Earth and travel to the future or to the past then you'll still be on earth no matter how far back you go or far far forwards.
Now can one travel in time? Well aren't there certain subatomic particles that have been shown to be able to do that very thing? I'm nearly certain that it is possible in theory to travel back in time, its just problematic and impractical with our current understanding of the universe.
Posted by neo-dragon (Member # 7168) on :
quote:Originally posted by L_mustang94: Could you pu that in English please.
I think he's saying that traveling backwards in time would be like rewinding a video tape. The people in the video go back to the past in a manner of speaking, but since this occurred by everything in the interim being undone, there's no memory of it happening.
That pretty much fits in with my own reasoning. Have you ever really stopped and thought about what time actually is? It's motion. We measure and perceive time based entirely on things changing position. Time would stop if every single particle in the universe stopped moving. The only difference between now and 10, 100, 1000, or 1 million years ago is that the infinite particles of the universe are in different places. The only way I can think of to travel back in time would be to somehow rearrange every single particle in the universe to a prior configuration (rewind the tape) but somehow put yourself outside the process. Find a way to control every single particle in existence and gain an omniscient knowledge of their paths since the big bang and then you can time travel at will.
quote:Originally posted by Blayne Bradley: special and general relativity from what I have read more or less state that there is no absolute coordinate system and that your location is more or less irrelevant, if your on Earth and travel to the future or to the past then you'll still be on earth no matter how far back you go or far far forwards.
Only if you move through space as well. And I don't know of any subatomic particles that time travel.
Posted by Sean Monahan (Member # 9334) on :
quote:Originally posted by Blayne Bradley: Now can one travel in time? Well aren't there certain subatomic particles that have been shown to be able to do that very thing?
You may be thinking of tachyons, which travel faster than light, so they appear to travel backwards in time. A tachyon traveling from point A to point B would arrive at point B before the light that shows it leaving point A. Although, tachyons remain only theoretical, and I believe the scientific community in general has given up on ever finding them.
Or you may be thinking of antimatter. I believe it was in the book QED that Richard Feynman stated that physics sees no difference between a positron moving forward in time and an electron moving backwards in time - as far as physics is concerned a positron *is* an electron moving backwards in time. This led Feynman to devise his Single Electron Universe theory, in which the universe only contains one electron, which keeps propagating backwards in time as a positron, then reverses direction and shows up as a different electron somewhere else. This theory doesn't hold up to scrutiny though, because it requires an equal number of positrons and electrons in the universe.
Posted by Ecthalion (Member # 8825) on :
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