Zero - Charles Seife [74]
Just as zero punches a hole in the smooth sheet of general relativity, zero smooths and spreads out the sharp point charge of the electron, covering it in a fog. However, since quantum mechanics deals with zero-dimensional particle-points such as the electron, technically all particle-particle interactions in quantum theory deal with infinities: they are singularities. When two particles merge, for instance, they meet at a point: a zero-dimensional singularity. This singularity makes no sense in quantum mechanics or in general relativity. Zero is the wrench in the works of both great theories. So physicists simply got rid of it.
It is not obvious how to get rid of zero, as zero appears and reappears throughout time and space. Black holes are zero-dimensional, as are particles such as the electron. Electrons and black holes are real things; physicists can’t simply will them away. But scientists can give black holes and electrons an extra dimension.
This is the reason for string theory, which was created in the 1970s when physicists began to see the advantages of treating every particle as a vibrating string rather than as a dot. If electrons (and black holes) are treated as one-dimensional, like a loop of string, instead of as zero-dimensional, like a point, the infinities in general relativity and quantum mechanics miraculously disappear. For instance, the renormalization trouble—the infinite mass and charge of the electron—vanishes. A zero-dimensional electron has an infinite mass and charge because it is a singularity; as you get closer and closer to it, your measurements zoom off to infinity. However, if the electron is a loop of string, the particle is no longer a singularity. This means that the mass and charge don’t go off to infinity, because you are no longer passing an infinite cloud of particles as you approach the electron. Furthermore, as two particles merge, no longerdo they meet at a point-like singularity; they form a nice, smooth, continuous surface in space-time (Figures 54,55).
Figure 54: Point particles create a singularity…
Figure 55:…string particles don’t.
In string theory different particles are really the same type of string, just wiggling in different ways. Everything in the universe is made up of these strings, which are about 10-33 centimeters across; comparing the size of a string to the size of a neutron is like comparing the size of a neutron to the size of our solar system. From the perspective of beings as large as we are, the loops look like points because they are so tiny. Distances (and times) smaller than the size of the loops no longer matter; they don’t make any physical sense. In string theory, zero has been banished from the universe; there is no such thing as zero distance or zero time. This solves all the infinity problems of quantum mechanics.
Banishing zero also solves the infinity problems in general relativity. If you imagine a black hole as a string, no longer do objects fall through a rip in the fabric of space-time. Instead, a particle loop approaching a black-hole loop stretches out and touches the black hole. The two loops tremble, tear, and form one loop: a slightly more massive black hole. (Some theorists believe that the act of merging a particle to a black hole creates bizarre particles such as tachyons: particles with imaginary mass that travel backward in time and move faster than light. Such particles might be admissible in certain versions of string theory.)
Removing zero from the universe might seem like a drastic step, but strings are much more tractable than dots; by eliminating zero, string theory smooths out the discontinuous, particle-like