23 - Supergravity

Summary

The gravitational force is surely one of the most remarkable forces acting upon our elementary particles. You may remember that at the beginning of our journey towards the world of the small we observed that gravity is much less important for tiny creatures than it is for large ones. We used the example that, whereas a mouse can climb up a nearly straight wall, an elephant cannot. For atoms and molecules, and all the other particles we have discussed so far, gravity is practically a negligible phenomenon. But when we look at particles considerably smaller than the size of an atomic nucleus, we reach a turning point. Gravity acts upon the mass of the particles, whereas all other forces act on something we call ‘charge’. The difference is that charge depends only very slightly on the degree of magnification of our microscope, whereas mass is connected to energy, and if we try to localize a particle in a smaller volume then, according to the rules of quantum mechanics, there will be more motion; the energy of motion (called ‘kinetic energy’) increases. This is why smaller distances correspond to higher energies, and hence also larger masses. When distances are so small that the movements become relativistic (i.e. close to the speed of light) the effects of the gravitational force gradually begin to increase relative to the other forces; however, they are still incredibly weak, and so they have a long way to go before thay can compete in strength.