String theory says that the smallest unit of matter is not an atom, electron, quark, or any other particle, but a little loop of string. Everything in the universe is made up of these tiny loops of energy, vibrating in different patterns.
That is if they actually exist. They are so small that there is no way to see them or to experiment with them. String theorists think they exist because mathematical equations point to them.
How small are they? If an atom were the size of the known universe, a string would be the size of a tree. Strings may be the answer to "How small can you go?" They are made up of nothing else and cannot be divided. "It may be the end of the line," says Brian Greene, a math and physics professor at Columbia University and a leading proponent of the theory.
Small, but important. Strings could be the Holy Grail of physics - the answer to how the universe really works. String theory reconciles the contradictions between general relativity (the rules that govern very big and heavy things such as galaxies) and quantum mechanics (which explains what goes on with very tiny things such as subatomic particles). Einstein remained puzzled by this.
"String theory may be the theory that with one idea, one master equation can explain everything in the universe," Professor Greene says.
String theory comes into play when the very huge and heavy meet the very tiny, which is rare but could explain such phenomena as the big-bang theory and black holes. It also says that the fabric of space can rip, an important discovery made by Greene and a colleague a few years ago, and that there are more than three dimensions - perhaps as many as 10.
Since the theory has not been tested, not every physicist is a believer. But even skeptics are keeping tabs on it.
"String theory doesn't say much about the observable world. It doesn't make any predictions that can be verified by experiment," says Sheldon Glashow, a physics professor at Harvard University and a Nobel laureate. "Still, there is a host of questions left wide open that have to be answered by some theory, and the hope is that it'll be string theory, because there's nothing else on the horizon, as far as I can tell."
(c) Copyright 1999. The Christian Science Publishing Society