# Folding space

**Question:**

If one could fold space in order to travel vast distances relatively fast, how far could one travel, and in what time frame? What effects would the travel have on our bodies and what would a person see if they looked out the window?

**Answer:**

We live in a universe that has three space dimensions (as far as we know) and one time dimension. But to make my answer to your question easier to understand, let us pretend the space of our universe has only two dimensions, like a piece of paper, but a piece of paper billions of light-years across. Imagine two points (call them A and B) a hundred light-years apart on that huge piece of paper. Something travelling on the surface of the paper at the speed of light would take a hundred years to get from A to B. But suppose we bend or fold the paper over so that the points A and B touch. Then there is a "short cut" from A to B that has zero length --- or at least a very small length. Taking that short cut would not take a hundred years, but maybe only an instant --- or at least a very short time.

Could the space of our universe fold over like that so that points that are far apart on the paper touch? One cannot rule that out. But even if such a thing could happen, there is the question of how to take the "short cut". It would require what is called a "Minkowski wormhole" (a kind of bridge in space) to connect the two points A and B. The laws of gravity, as written down by Einstein, allow Minkowski wormholes to exist, but ONLY if there exists some kind of matter whose energy and momentum is unlike that of any kind of matter ever seen and extremely unlikely to exist in the real world. For this reason, physicists think that travel great distances by "folding space" is highly unlikely to be possible.

But suppose it were possible. There would be no limit to how far one could travel in space in almost an instant. But even stranger, one could also travel backwards in time, because a wormhole (if they such things existed) could connect a point A at one time to a point B that was at an earlier time. That is, one could travel anywhere in space and time. That means you could get somewhere before you even departed! As to what would happen to our bodies in the process, I do not know exactly. It would depend on the size of the wormhole. The gravitational effects inside the wormhole would probably be immense and destroy a human being going through.

Fortunately, such things are almost certainly not allowed by the laws of physics.

-Stephen Barr