# Travelling to the edge of the Universe, 4th Dimensional Time Travel

1. Apr 18, 2014

### GetBent

There is no edge of the Universe. Alright, I kinda realize this, I'm not a layman.

However, nobody addresses what would happen if you traveled far enough. There's only a limited amount of matter out there and going off the theory that the volume of our Universe is finite, there's 'an edge' somewhere. Maybe not one that is reachable in 3D space however..

Say you're an adventurer, and you cataloged every piece of matter in existence after traveling for trillions of light years in one single direction. My question: Would you eventually 'wraparound' back to your original location, like in a video game, like Pac-Man?

Take the balloon model, imagine a 3d Balloon. On there is a 2D Plane. The 2D plane is the universe. We put circles with marker over it to represent galaxies and we inflate it. That's our Universe expanding from Dark Energy and yada yada (We all know this). Now we draw a straight line around the balloon. Though it's not a straight line to us, it is to the 2D inhabitants. In our 3D world, the line 'bends' across our 3D vector, where to the 2D inhabitants however, it's just a line going on and on in one direction.

Now apply that to the 3D Universe. Assuming the Universe is just one big 4D hypersphere: Using the model, as we travel in a straight line journey across the Cosmos in one direction, we'd be 'bending' across this 4th Dimensional vector, which is Time correct? So if we keep traveling, the 4th coordinate vector would increase, than slowly decease back to our original vector location, which would mean our Time is getting distorted. Would we eventually return to our original location, and would it happen because the side effect of Time Travel has made it feasible?

2. Apr 18, 2014

### Chronos

The observable universe is always centered on the observer. No matter how far you travel, you are still at the center of your observable universe.

3. Apr 18, 2014

### Staff: Mentor

We don't know. It may or may not be true. We do know that if the universe does curve back on itself it must take hundreds of billions of light years at least. Otherwise we would see curvature already. Instead, measurements show a universe that is very close to being flat.

No, this curvature would be in a 4th spatial dimension, not in time.

4. Apr 19, 2014

### GetBent

Care to elaborate on what you mean by 4th 'spatial' dimension rather than just the 4th Dimension?

5. Apr 22, 2014

### DHF

Its impossible to ever prove this one way or the other since the observable universe is expanding faster then c. Since its impossible travel faster then c we can never reach the limits of the universe even if we traveled for trillions of years.

6. Apr 22, 2014

### Staff: Mentor

A 4d hypersphere by definition occupies four spatial dimensions. The curvature would be along the surface of the hyperesphere, not the time dimension.

http://en.wikipedia.org/wiki/Hypersphere

7. Apr 29, 2014

### Neumeric

The fourth spatial dimension could for example be orthogonal, at right angles to, to all three of the dimensions we are so familiar with. All three, simultaneously...

8. Apr 30, 2014

### GetBent

..but the fourth 'spatial' dimension doesn't exist in our Universe correct?

9. Apr 30, 2014

### Staff: Mentor

As far as we know, we live in a universe with three spatial dimensions and one time dimension, so no, it does not exist.

10. May 1, 2014

### HallsofIvy

Staff Emeritus
I puzzled by this. You say you are a professional physicists, yet you seem to be unable to answer fairly basic questions about physics.

11. May 1, 2014

Huh?