# How could you visit yourself 10 mins ago?

1. Jul 1, 2010

### seanbateman

Hypothetically lets say you were in Kurt Godel’s universe and time travel was possible.
http://img96.imageshack.us/img96/4307/ti [Broken]...
An image that may help explain what I’m saying

Imagine going back in time to visit yourself 10 minutes ago.
Just to made it easier to visualise lets imagine ten minutes ago you were down the shops, you walk back home, remember this bit you push a cup off the table what lands on the floor and then you go into your time machine to travel back in time 10 minutes to when you were still down the shops.
Now on travelling back in time the energy that went from the cup into the floor goes back into the cup and the cup rises and goes back into the table.
But the atoms that made up you ten minutes ago are still in status in the time machine, so they can’t go back down the shop for you to visit them.
The atoms that made up you 10 minutes ago will not just appear this would create more mass in the universe and due to E=MC^2 there is more energy in the universe going again fundamental laws in physics.

Last edited by a moderator: May 4, 2017
2. Jul 1, 2010

### nismaratwork

You can't?

Last edited by a moderator: May 4, 2017
3. Jul 6, 2010

### AJ Bentley

If you're going to postulate an imaginary universe, why not pick one where you get to choose the laws of physics?

4. Jul 6, 2010

### nismaratwork

In my universe, the laws of physics don't cornhole causality, but cows can produce chocolate milk. :)

5. Jul 6, 2010

### AJ Bentley

Ah, All's for the best in the best of all possible worlds!

6. Jul 6, 2010

### bcrowell

Staff Emeritus
This is pretty sad. A newbie posts a good question of PF, and instantly attracts a series of replies that are both (a) incorrect and (b) sarcastic put-downs.

You could, if our spacetime had the Godel metric.

The Godel metric obeys the known laws of physics. It's an exact solution to the Einstein field equations.

@Seanbateman:

Welcome to PF, and thanks for posting an interesting question!

The Godel metric has CTCs through every point in spacetime. Therefore you don't have to start from any special location in spacetime in order to have your world-line be a CTC.

I don't know if it has CTCs that are also geodesics. If so, then all you'd have to do is have the right initial velocity vector, and you'd experience a CTC.

GR doesn't have global conservation of energy, so the fact that CTCs lead to nonconservation doesn't imply a violation of the laws of physics.

There is a good discussion of this in Black Holes and Time Warps. by Kip Thorne.

7. Jul 6, 2010

### nismaratwork

If you were in a Godel universe, then "going back 10 minutes" wouldn't be the issue; you would probably be trapped for an indefinite period of time in one CTC after another. There would be no causality in such a universe, so the question is meaningless, much as the question of what life would be like beyond the event horizon of a black hole. Is there something beyond it, probably, but is it in any way formulated to agree with the question? No. He's new, that doesn't make it a good question, which as you've pointed out, has better discussions occurring elsewhere in the forum.

8. Jul 6, 2010

### AJ Bentley

Cat fight! Cat fight!