time travel to the past

[Imparcticle]

Is it true that theoretically, you can use a wormhole to travel into the past?
How so? Does this whole idea not violate the 1st law of thermodynamics?
Could the past already somehow exist??? (i don't think so, but just for the record, I'd like your opinion.)

[turin]

According to what theory; can you name this theory for us? According to GR, as far as I know, you cannot start on a positive timelike trajectory, enter a wormhole, and escape the singularity.

[billy_boy_999]

i think you're right in saying it's basically a thermodynamics issue...i don't think there is really a 'past' to travel to, you can't undue the entropy inherent in time and motion...traveling into the future happens every time you move a muscle...

[Imparcticle]

And why does entropy only "move" (can't think of the right word at the moment) in one [temporal] direction? Is it because something can only increase in disorder, never decrease and not do both simoltaneosly?

[DrChinese]

Great questions. Although some strange variations on General Relatvity seem to support wormholes or warp bubbles, i believe they also require more energy to implement than is present in the universe. By my standards, that makes it impossible.

As to the thermodynamic arrow of time: that is one of the great mysteries. All known laws are time-symmetric. So where does the arrow come from?

Lastly, it is not clear that the 2nd law actually prevents time travel. The question essentially becomes: is the 2nd law more fundamental than GR? Over vice versa? Or neither?