Tuesday 26 September 2000

Pic of the day: Reading Scientific American, which had a good article on this in the August issue.

Parallel worlds

Dimensions are cool. Obviously they are also fairly hard to understand, since most people seem to use the word all wrong when it comes to parallel universes. These are not parallel dimensions (which really doesn't make sense, once you think about it ... can height and width be parallel?) but parallel universes along a fifth dimension.

I've mentioned before that I see the universe as a 4-dimensional hypersphere with time as the radial dimension. The only way to imagine this in 3-D (as if that would be a good idea at all) would be to remove one of the other dimensions and replace it with the time axis. Now if we remove a dimension again, we can reduce the universe to a sheet. Now add a new third dimension (actually the fifth, after time) and tilt the universe. Seeing it from the side, you can see that it is just a thin membrane. And there is room for other universes just beside it. They could be less than a millimeter away and we would be totally oblivious to them - perhaps.

You see, most things are waves. You probably remember from high school physics that photons (light particles) behave like waves. Depending on your teacher and your textbook, there may have been a casual reference to the fact that other elementary particles also do this if allowed to roam around. Now the point is that these waves are confined to the surface that holds them. Like you drop a pebble in a pond - the waves run along the surface of the pond, they don't move equally into the air or down into the ground. In the same way, the waves that constitute matter is confined to our sheet universe.

There is some doubt about gravity. It behaves oddly, compared to the other primary forces. Basically, it seems too weak. This could be because it radiates in the fifth dimension. Now this is a scary thought for several reasons. A sufficiently large black hole in a neighboring universe might wreak havoc here without any warning at all. The basic structure of the universe may even not be decided by anything within our universe at all, but be part of a five-dimensional structure. The origin and composition of this structure, we would have no possibility of ever knowing.

If gravity does not radiate along the fifth dimension (and there is no proof that it does) then basically we will never know whether there are indeed other universes parallel to ours. Except - it is not obvious that all the other universes are like ours, with the same laws of nature and the same waves and particles. Perhaps each has slightly (or very) different laws. Some of the universes could possibly have particles or energies that radiate in the fifth dimension. This would probably be a disaster to them, as they would bleed energy at a furious rate and perhaps eventually dissipate completely. The effect on ordinary "flatland" universes would be much less: The 5D particles would probably interact very weakly with ours, as they would just be passing through an almost infinitely thin sheet giving next to no resistance. Yet, a sufficiently dense rain of particles along the 5th dimension might cause some really surreal effects.

So what about UFOs? Theoretically, glowing masses of plasma could be caused by the trail of a 5D object speeding through, I guess. As for flying saucers, small green men, elves, Elvii, angels, demons, and ghosts ... I don't think so. That is, I don't think any of these have anything to do with the parallel universes. But we cannot be sure. (Anyway, it makes for incredible possibilities to blend science fiction with magic fantasy / mythology. Mmm!)

It is strange indeed to think that quite possibly there are other worlds literally closer to us than our own clothes, entire universes filling the same space that we do. Chances are we will never know anything about these worlds, not even whether they exist. But we'll keep looking.

Though I don't think it justifies creating small black holes on Earth, if you want my opinion.