"Since wormhole solutions are extremely difficult to work with, **Hawking began his argument by analyzing a simplified universe discovered by Charles Misner of the University of Maryland which had all the ingredients of time travel.** **Misner space is an idealized space in which your bedroom, for example, becomes the entire universe.** Let’s say that every point on the left wall of your bedroom is identical to the corresponding point on the right wall. This means that if you walk toward the left wall, you will not get a bloody nose, but will instead walk through the wall and reappear from the right wall. This means that the left and right wall are joined, in some sense, as in a cylinder ...

What is really bizarre is that, **if you look carefully at the left wall, you see that it is actually transparent and there is a carbon copy of your bedroom on the other side of this wall**. In fact, there is an exact clone of yourself standing in the other bedroom, although you can only see your back side, never your front side. **If you look below or above, you also see carbon copies of yourself. In fact, there is an infinite sequence of yourselves standing in front, behind, below, and above you.** Making contact with yourself is quite difficult. Every time you turn your head to catch a glimpse of the clones’ faces, you find that they have also turned away, so you never see their faces. **But if the bedroom is small enough, you might pass your hand through the wall and grab the shoulder of the clone in front of you. **Then you might be shocked to find that the clone behind you has reached out and grabbed your shoulder as well. Also, you can reach out with your left and right hands, grabbing hold of the clones to your side, until there is an infinite sequence of yourselves holding hands. **In effect, you have reached completely around the universe to grab ahold of yourself** ...

**In Misner space, assume that the walls are collapsing around you. Now things become very interesting.** Let’s say the bedroom is being squeezed, with the right wall slowly coming toward you at 2 miles per hour. If you now walk through the left wall, you will return back from the moving right wall, but boosted by an additional 2 miles per hour, so you are now traveling at 4 miles per hour. In fact, each time you make a complete circuit into the left wall, you get an additional boost of 2 miles per hour emerging from the right wall, so you are now traveling at 6 miles per hour. **After repeated trips around the universe, you travel 6, 8, 10 miles per hour, until you gradually approach incredible velocities close to the speed of light.**

At a certain critical point, you are traveling so fast in this Misner universe that you travel back in time. **In fact, you can visit any previous point in space-time.** Hawking analyzed this Misner space carefully. **He found that the left wall and right wall, mathematically speaking, are almost identical to the two mouths of a wormhole.** In other words, your bedroom resembles a wormhole, where the left wall and the right wall are the same, similar to the two mouths of a wormhole, which are also identical."

**–"Parallel Worlds: A Journey Through Creation, Higher Dimensions, and the Future of the Cosmos" by Michio Kaku. **