Lee Smolin is a professor of physics in the
Center for Gravitational Physics and Geometry at Pennsylvania State University. He is the author of
The Life of the Cosmos (Oxford University Press and Wiedenfeld and Nickelson, 1997). He provides some further information:
"The first thing to say is that we don't know. So let me put forward some things we do know. There are various pieces of evidence that space is quantized, in the sense that there is a smallest possible unit of the area of a surface, the volume of a region or the distance between two points in space. This limit comes from applying the rules of quantum theory to Einstein's theory of general relativity. The discrete units are about the size of the Planck scale, which is 10 -33 centimeter, or about 20 orders of magnitude smaller than an atomic nucleus.
"There is more than one approach to combining quantum theory with general relativity that gives evidence for the quantization of spatial geometry. One of these approaches is called string theory; there are several different arguments within string theory that lead to the conclusion that space is quantized. Another line of argument derives simply from the application of quantum mechanics to general relativity. This approach was worked out first by
Carlo Rovelli of the University of Pittsburgh and myself, although later many other people have confirmed this result by different methods. "It must be mentioned that none of these predictions has so far been confirmed experimentally. But this is" just a problem of technology. It is hard to believe that there will not come a time when we can make measurements with sufficient accuracy that these predictions can be used to test the theories on which they are founded.