Thread: the twin paradox and reletivity

the faster you move thorough space, the slower you move through time.

I think ive got a pretty good handle on this concept. Also I've looked into the Twin paradox althought it wasnt a very in-depth look, seeing as how i dont understand Einstien's math. and thus dont really understand his explanation, but it was explained to me like this...
If a spaceman Bob is going through space at lightspeed, theres no way to tell whos going at the speed of light, Bob, or the rest of the universe. But when bob (accelerates/decelerates) for the U-turn he "shifts worlds" then that makes him the object that is traveling at the speed of light. So it's all about the forces of acceleration.
Someone may have to correct me on my understanding of the twin paradox.

Now, ive wondered if it possible for a spaceman to attain the opposite of lightspeed.
Go through slower through space, and faster through time.

iv' read somewhere, not sure where, that this is impossible. They said it had something to do with the expansion of the universe. But i'm not convinced, not just yet.

I was just wondering if anyone would like to shed some light on this subject for me. Thanks

You might read a post I made here and let me know if it helps.
After reading, consider this: Everything that we're dealing with is already In Motion. We are being carried In Motion.

In order to "slow down" time, you would have to stop the Universe from moving (Or slow the Universe down). Good luck with that... But even if with Divine powers you were to succeed, it would make no difference. Because to everyone's relative position, they would see no change in the rate of how time passes.

Originally Posted by Joe McCarron

the faster you move thorough space, the slower you move through time.

I think ive got a pretty good handle on this concept. Also I've looked into the Twin paradox althought it wasnt a very in-depth look, seeing as how i dont understand Einstien's math. and thus dont really understand his explanation, but it was explained to me like this...
If a spaceman Bob is going through space at lightspeed, theres no way to tell whos going at the speed of light, Bob, or the rest of the universe. But when bob (accelerates/decelerates) for the U-turn he "shifts worlds" then that makes him the object that is traveling at the speed of light. So it's all about the forces of acceleration.
Someone may have to correct me on my understanding of the twin paradox.

That is consistent with my understanding. As long as nobody accelerates, the problem is perfectly symmetric, and anything that can be said about one twin, can also be said about the other twin from a different perspective. Once one accelerates and the other doesn't, different story.

Originally Posted by Joe McCarron

Now, ive wondered if it possible for a spaceman to attain the opposite of lightspeed.
Go through slower through space, and faster through time.

iv' read somewhere, not sure where, that this is impossible. They said it had something to do with the expansion of the universe. But i'm not convinced, not just yet.

I cannot comment on the expansion of the universe aspect of this, as it surpasses my competence. But, even in a static universe full of empty space (the universe of special relativity), it is not possible for the spaceman to achieve light speed. It requires infinitely much energy to do so.

The version of this I have been taught is that, from someone else's perspective, as the spaceman approaches the speed of light, his mass approaches infinity, (formula from memory, I hope I did not make any mistakes). As the mass becomes larger and larger, more and more energy is required to generate any further acceleration. Any finite amount of energy produces a velocity that may be very close to, but still less than, the speed of light.

How expansion of the universe may affect this analysis, I do not know.

Originally Posted by Joe McCarron

I was just wondering if anyone would like to shed some light on this subject for me. Thanks

I have tried; I hope I succeeded I think MisterMe could perhaps shed some light on the universe expansion question.

Originally Posted by Coelacanth

...

I cannot comment on the expansion of the universe aspect of this, as it surpasses my competence. But, even in a static universe full of empty space (the universe of special relativity), it is not possible for the spaceman to achieve light speed. It requires infinitely much energy to do so.

...

How expansion of the universe may affect this analysis, I do not know.

I have tried; I hope I succeeded I think MisterMe could perhaps shed some light on the universe expansion question.

The notion of moving slower through space and faster through time assumes an absolute reference frame. This is not allowed by the Special Theory of Relativity. You have only inertial reference frames. All velocities are measured with respect to an inertial reference frame. General Relativity ended the restriction that reference frames be inertial, but I digress.

We may consider the notion of an object's moving slower through space and faster through time as an object moving slowly with respect to our inertial reference frame. The slowest speed is given by . An object moving at shares the proper time of all clocks in the inertial reference frame.

We may also consider this as a take-off on an old concept of tachyons. Back in the day, tachyons were speculated as faster-than-light particles that were infinitely fast at zero energy and infinitely energetic at light speed. Tachyons are no longer thought to be superluminal particles because their existence would violate causality. They are now thought to be so highly unstable as not to be existent. At any rate, the concept of opposite speed seems like the old tachyon concept shifted and squeezed to subluminal speeds between and .

Originally Posted by MisterMe

The notion of moving slower through space and faster through time assumes an absolute reference frame. This is not allowed by the Special Theory of Relativity. You have only inertial reference frames.

Originally Posted by MisterMe

We may consider the notion of an object's moving slower through space and faster through time as an object moving slowly with respect to our inertial reference frame.

I think this is what the OP means; I don't see any claim of an absolute frame of reference anywhere.

Originally Posted by Coelacanth

I think this is what the OP means; I don't see any claim of an absolute frame of reference anywhere.

The only way that an object can move through space slower than your reference frame and through time faster is if there is some other more fundamental reference frame. Obviously, the slowest object aging the fastest is the one in the absolute reference frame. It doesn't matter whether the OP made the claim or not. His question makes no sense otherwise.

Originally Posted by MisterMe

The only way that an object can move through space slower than your reference frame and through time faster is if there is some other more fundamental reference frame. Obviously, the slowest object aging the fastest is the one in the absolute reference frame. It doesn't matter whether the OP made the claim or not. His question makes no sense otherwise.

OK, I think I missed those two lines in the OP. I saw the beginning, which sounds like a layperson's description of the Lorenz transform (the only part requiring modification is that the spaceman can't move at lightspeed, just very close), and then the bit at the end asking whether this is due to the expansion of space-time (answer, not entirely, these effects exist even in a non-expanding SR universe).

I missed the part about moving slower through space and faster through time. Assuming it means "slower than someone who is stationary in the relevant inertial reference frame", I agree, this is impossible.

Originally Posted by Joe McCarron

So it's all about the forces of acceleration.

Bingo. Let's say you have two twins, one stationary (no acceleration) and the other accelerating away before returning. Each twin has a relative velocity with respect to the other. That doesn't mean the time dilation effects are identical or that there are no time dilation effects upon the accelerating twin's return.

The twin who accelerated away before returning will return with a previously synchronized timepiece that's running behind that held by the stationary twin.

Originally Posted by Coelacanth

I missed the part about moving slower through space and faster through time. Assuming it means "slower than someone who is stationary in the relevant inertial reference frame", I agree, this is impossible.

I apologize, I didnt really understand the complexity of my question. but you pretty much nailed it anyway. I still dont really understand Specail Reletivity. So reguardless of how fast i may be going, im always stationary to my own frame of refrence?

I never really thought about it that way. I always use my distance to other objects to get a sense of speed at any givin point when i'm driving.

Originally Posted by Joe McCarron

So reguardless of how fast i may be going, im always stationary to my own frame of refrence?

Yes, in fact that would be a way to define your frame of reference.

Originally Posted by Joe McCarron

I never really thought about it that way. I always use my distance to other objects to get a sense of speed at any givin point when i'm driving.

No problem there, it just gives you the speed of the trees etc. on the road side in your reference frame, and your speed (in the opposite direction) in their reference frame