Time travel

[Kingwobbly]

I'd like to preface this by saying I haven't studied physics for more than two years and even back then it wasn't my best subject.
If time travel were possible, how do you think it would be achieved? In theory, travel forward in time is possible as the faster one travels to the speed of light, the slower time passes relative to how we generally measure time. By extension, if one were to travel faster than the speed of light (which is currently believed to be impossible) would our relative time reverse? Or would it be infinitely slow at light speed and above?

If that were not possible, the only other way I could think of would be if the multiverse theory is correct and if every choice creates another universe then there should be infinite universes at different points in time relative to ours and so by traveling between universes you could emulate travel in time (though it wouldn't technically be time travel).

Do you think time travel could be possible? If so do you have any theories as to how it might occur?

 

[Trisarahtops]

Time dilation has been a proven relativistic dynamic. It is used to study atoms of elements that decay too rapidly to study normally. This means they speed them up fast enough that the time in their reference frame slows down. This allow it to live long enough in our frame to be studied. But right now, it is assumed that you can not travel the speed of light because of the gamma factor that is used to relate the speed at which it is traveling to the time or length of the object in the relativistic frame. If the speed of the object were the speed of light, the gamma factor would be undefined because you would divide by a zero. And then if the speed was greater than the speed of light, you would have the square root of a negative and you would end up with an imaginary number and so on and so forth...

Even disregarding the fact that we don't really know if traveling the speed of light is even possible, I still think that time wouldn't reverse. This is because the relativistic time is still related to the non-relativistic reference frame. To try and describe this more, the object traveling relativistically can still be observed by an outside source. For example, our limited testing of the general theory of relativity has been by done by using atomic clocks and accelerating them as fast as we currently are capable of, then comparing them to clocks outside of the accelerated reference frame. It has been seen that time travels slower and the the time of the accelerated clock is behind the time of the observation clock. But what would we observe if the accelerated clock were travelling faster than the speed of light. The time in that frame would run in reverse, but would the event outside of that frame reverse as well? Would they just "disappear" from existence? For myself, it is really hard to imagine time travel by use of relativity, because relativity is a comparison between to different inertial states. If you were to time travel, how would you still have the two reference frames existing in the same comparable universe? Personally, I think the best we can do with relativity is to significantly slow or even stop time in one reference frame. If we are going to time travel, it will have to be using something other than relativity.

 

[Kingwobbly]

Time dilation has been a proven relativistic dynamic. It is used to study atoms of elements that decay too rapidly to study normally. This means they speed them up fast enough that the time in their reference frame slows down. This allow it to live long enough in our frame to be studied. But right now, it is assumed that you can not travel the speed of light because of the gamma factor that is used to relate the speed at which it is traveling to the time or length of the object in the relativistic frame. If the speed of the object were the speed of light, the gamma factor would be undefined because you would divide by a zero. And then if the speed was greater than the speed of light, you would have the square root of a negative and you would end up with an imaginary number and so on and so forth...

Even disregarding the fact that we don't really know if traveling the speed of light is even possible, I still think that time wouldn't reverse. This is because the relativistic time is still related to the non-relativistic reference frame. To try and describe this more, the object traveling relativistically can still be observed by an outside source. For example, our limited testing of the general theory of relativity has been by done by using atomic clocks and accelerating them as fast as we currently are capable of, then comparing them to clocks outside of the accelerated reference frame. It has been seen that time travels slower and the the time of the accelerated clock is behind the time of the observation clock. But what would we observe if the accelerated clock were travelling faster than the speed of light. The time in that frame would run in reverse, but would the event outside of that frame reverse as well? Would they just "disappear" from existence? For myself, it is really hard to imagine time travel by use of relativity, because relativity is a comparison between to different inertial states. If you were to time travel, how would you still have the two reference frames existing in the same comparable universe? Personally, I think the best we can do with relativity is to significantly slow or even stop time in one reference frame. If we are going to time travel, it will have to be using something other than relativity.

I would go with this. I know that time dilation is used for measuring particles, I mean for people it's only theory because we can't make people accelerate that fast without them popping or getting squished and so can't really prove it. Although I suppose it's not a theory since we know that would happen if we could make a person go that fast.
Also I think light speed travel is impossible for something with mass according to current equations involving relativity so unless we discover all we know about the speed of light to be wrong, I agree with you that it would be impossible for an object with mass to travel at the speed of light.
I also agree in that I don't think time would reverse for an object if it were to travel faster, I think it would be in an infinitely slow frame of inertia, but since light doesn't travel instantaneously, time isn't completely still even for light.

 

[Trisarahtops]

We can't really say that time isn't completely still for light. Because in our reference frame sure, it is still moving and time is passing normally, but we have no idea what is happening in lights reference frame. Time could be stopped for light.

 

[RedLink]

Time dilation has been a proven relativistic dynamic. It is used to study atoms of elements that decay too rapidly to study normally. This means they speed them up fast enough that the time in their reference frame slows down. This allow it to live long enough in our frame to be studied. But right now, it is assumed that you can not travel the speed of light because of the gamma factor that is used to relate the speed at which it is traveling to the time or length of the object in the relativistic frame. If the speed of the object were the speed of light, the gamma factor would be undefined because you would divide by a zero. And then if the speed was greater than the speed of light, you would have the square root of a negative and you would end up with an imaginary number and so on and so forth...

Even disregarding the fact that we don't really know if traveling the speed of light is even possible, I still think that time wouldn't reverse.

What about for particles that are already traveling at the speed of light? I'm talking no acceleration.

Also I think light speed travel is impossible for something with mass according to current equations involving relativity so unless we discover all we know about the speed of light to be wrong, I agree with you that it would be impossible for an object with mass to travel at the speed of light.

But don't all particles gain infinite mass when traveling at light speed? How does having pre-existing mass affect your ability to hit light speed?

 

[Trisarahtops]

What about for particles that are already traveling at the speed of light? I'm talking no acceleration.

It had to be accelerated at some point. I guess when I say accelerating, jumlst means it had accelerated to be at the speed it is at.​

 

[RedLink]

It had to be accelerated at some point. I guess when I say accelerating, jumlst means it had accelerated to be at the speed it is at.​

But light photons don't accelerate. Their energy and momentum just come from other particles and fields.

 

[Jamie]

Travelling faster than light would indeed allow us to go backward in time, but that can affect causation and so it's not possible. If we had working time travel, I think it would involve us creating a new universe of sorts, so we wouldn't be travelling in our own "dimension".

 

[Trisarahtops]

But light photons don't accelerate. Their energy and momentum just come from other particles and fields.

Okay sure, that is true. But that is completely unrelated to the point I was trying to make. All taking about acceleration in modern physics is used for is the determine what the relativistic frame is and what the base frame is. The relativistic frame is the one who had to be "accelerated" to get to the speed it was going. Besides the speed of like is the speed of light, no matter what frame you are in so apply the theory of special relativity to a photon is nonsensical.

 

[RedLink]

Okay sure, that is true. But that is completely unrelated to the point I was trying to make. All taking about acceleration in modern physics is used for is the determine what the relativistic frame is and what the base frame is. The relativistic frame is the one who had to be "accelerated" to get to the speed it was going. Besides the speed of like is the speed of light, no matter what frame you are in so apply the theory of special relativity to a photon is nonsensical.

Fair enough.

 

[Kylo Ken]

If anyone here discovers time-travel, post under the name "Himura Kenshin is awesome" at exactly noon on April 4th.

 

[Kingwobbly]

If anyone here discovers time-travel, post under the name "Himura Kenshin is awesome" at exactly noon on April 4th.

Sorry, I will be too busy riding a T-Rex.

 

[Spiritual Mask Salesman]

Time travel is such a tricky subject. Traveling the speed of light could allow one to travel into the future, that much we know, but it will always only be a theory until it is actually proven. Traveling into the past seems impossible unless we were to find a way to travel into a different dimension that is an alternate version of our own that is in a different era than ours. Again it's all only theory, a tad far fetched in ways. I have heard though that scientists are trying to study Black Holes because they believe they might allow us to possibly time travel, travel to different dimensions, or maybe even travel our own universe faster (it is believed the intense gravity of black holes could be “folding” space, once crossed it could take us millions of light years away in the matter of seconds).

 

[Kingwobbly]

Time travel is such a tricky subject. Traveling the speed of light could allow one to travel into the future, that much we know, but it will always only be a theory until it is actually proven. Traveling into the past seems impossible unless we were to find a way to travel into a different dimension that is an alternate version of our own that is in a different era than ours. Again it's all only theory, a tad far fetched in ways. I have heard though that scientists are trying to study Black Holes because they believe they might allow us to possibly time travel, travel to different dimensions, or maybe even travel our own universe faster (it is believed the intense gravity of black holes could be “folding” space, once crossed it could take us millions of light years away in the matter of seconds).

Time dilation has been proven by accelerating particles. You don't have to actually get to light speed to travel forward in time, just travel very quickly. The faster you go, the slower time goes for you. The problem with people doing this is that it would take a lot of resources to make a craft capable of carrying a human at a speed that would make a note able difference without the acceleration squishing them into pulp.
Haha, yeah a black hole could transport us to another point in the universe, or just squish everyone and everything into a nice little lump of matter. It seems like a big risk, I'm not that desperate to travel through time and space XD

 

[Spiritual Mask Salesman]

Time dilation has been proven by accelerating particles. You don't have to actually get to light speed to travel forward in time, just travel very quickly. The faster you go, the slower time goes for you. The problem with people doing this is that it would take a lot of resources to make a craft capable of carrying a human at a speed that would make a note able difference without the acceleration squishing them into pulp.
Haha, yeah a black hole could transport us to another point in the universe, or just squish everyone and everything into a nice little lump of matter. It seems like a big risk, I'm not that desperate to travel through time and space XD

Yeah me either! Although I've heard somewere in the UK there is a giant machine being made that can replicate a black hole. It may be too late to save us, if it starts up we all might get sucked inside and die!