# Thread: if and when time travel is possible

1. Originally Posted by Mole
Actually Relativity works in reality. For we have measured the different speed of time on satellites moving fast around the Earth.

And we know that as we approach the speed of light, distance is foreshortened and time in dilated. So it is theoretically possible to travel from one side of the universe to the other in a lifetime, knowing that we leave our home millions or billions of years in the past, forever out of reach.
Yea relativity works, but that double slit experiment where the hypothesis for photons going back in time comes from isnt relativity theory..

What comes to what you said about relativity isnt quite true. Its true that to an outside observer for example a spaceship thats moving away next to you sideways at the speed of light appears to get smaller and that the same spaceship moving closer to you(and passing by) at the speed of light appears to be stretched, also if the spaceship is at in front of you and suddenly starting to move away from you at the speed of light will appear to first stretch and then get smaller. But the whole idea about relativity is that all of this is relative to the observer.

Ill explain it and need this uber artistic picture to illustrate:

Those rings are photons that are emitted from each end. If the ship is stationary, the photons from each end will hit your eyes at the same time and the ship will look normal to you. Now if the ship moves at(or near) the speed of light away from you sideways(as pictured), the photons from the side which is further away from you will take longer to travel to you than the photons which are at the other end. So because the ship is moving away from you and you perceive the other side with a small delay, the spaceship appears to you as if it had changed size. Similarly if the ship is moving towards you, you will perceive the photons that are closer to you sooner than the photons that come further away, so you will perceive photon that is older at the same time than you perceive photons that are coming from the side which is loser to you.

You see this is hat happens:

The first box is where the ship is when you perceive the closest part of it, the middle box is there just because you see it there also(as long as there are photons coming all over the ship, not just the ends) and the box on the right is where the ship is when you perceive the side which is furthest to you. -> the ship will look as if it was longer than it is in reality because it is relativistic how you perceive things due to static speed of light.

If this didnt clear it out, feel free to ask for further explanation.

What comes to traveling long distances in a lifetime, well basically it is true, but there is a twist to it which doesent really go hand in hand with your other claims.

You see if you are moving at the speed of light, you are not aging because none of the atoms can work normally anymore. You see the proton that is spinning around the atom nucleus cant spin anymore, as it would be required for it to move faster than light in order for it to spin around the nucleus -> atom will stop and you will stop perceiving time and nothing changes until you stop and you wil end up in the other side of the universe before you grow any older. Obviously you cant get back and have moved through time, as time is nothing than distance which light travels and when you travel at the speed of time, time will pass around you, but not on you. The time that will pass around you depend on how many light years you travel, so if you move 10 light years, 10 years have passed around you and you have moved the distance which light moves in 10 years.

2. The concept of time is per se pretty much unknown to the physical universe, as it looks from our present standpoint. That means going back in time would mean to rearrange the physical matter that way that you can recreate a previous state. But that wouldnt necessary mean that you'd change the present time. The other problem would be going forward in time, you cant create a physical state from the future you dont know.

With present physics thinking about time travel is very limited. Even spacetime theory is just a theory of space and not time. Time is only in the human mind. Maybe with quantum physics things will change. Following this quantum entaglement theories where particles are physically connected, maybe there is something like time-dilated connections...

3. I don't think it will ever be possible.

I do think however that great advances in spacecraft tech is possible, and that eventually we will slip the surly bonds of our solar system.

4. Originally Posted by INTP
You see if you are moving at the speed of light.
We can't move at the speed of light because mass reaches infinity which is impossible. However theoretically we can approach to near the speed of light where relativity effects are real and not just an illusion seen by an observer.

And although it is theoretically possible to approach the speed of light, it is not technologically possible now or even in the medium future.

5. Originally Posted by 93JC
Assuming time travel to the past is possible, would it be possible to do so without affecting the timeline by virtue of your very presence?
Yes, because magic.

6. Originally Posted by HelenOfTroy
Yes, because magic.
But... but... temporal causality loops!

7. Originally Posted by 93JC
But... but... temporal causality loops!
Oh dear, do i need to draw you a super diagram picture of magic?

8. Originally Posted by HelenOfTroy
Oh dear, do i need to draw you a super diagram picture of magic?
If you think it would help.

9. Originally Posted by Mole
We can't move at the speed of light because mass reaches infinity which is impossible. However theoretically we can approach to near the speed of light where relativity effects are real and not just an illusion seen by an observer.

And although it is theoretically possible to approach the speed of light, it is not technologically possible now or even in the medium future.
The whole point of relativity is that the measurement made is relative to point in spacetime where the measurement is made in. Spacetime will have an effect to the measurement due to its curvature. You could say that the measurement you are making is the real reality(since its the reality which effects you), but in my opinion thats just a retard Te way of looking at things. But if you take more intellectual view of the things(*cough* Ti *cough*), the real reality is what happens where the photons are sent, and the path of the photons arent straight due to the spacetime curvature, so things observed from a distance just seem to be different than what they actually are.

I need to go to work now, so i dont have to write more now about the mass of a photon, so i might come back to you later. What i can say is that E=MC2 and that there is no evidence for photons not having any mass, there is just evidence for that the mass cant be very big.

10. Originally Posted by 93JC
If you think it would help.

magic pic.jpg

I hope this makes things clearer for you.

(I do not pretend to own my mothers artistic talents)

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