Gravitational interaction discussion
My last publication as a physicist was “Measuring the Gravitational Interaction of Elementary Particles,” Physical Review D 1 (1970) 961-78. Its purport is as follows:
Of course you must exert effort to lift something while standing on earth; i.e., you put energy into the object. But this fact can be expressed by saying that the gravitational potential energy of the object is negative (in an amount equal to a certain number characteristic of the earth, multiplied by the object’s mass). To get the object to completely escape the earth, as with a space probe, you must add that entire amount of energy so that its gravitational energy will go from something negative to zero.
Now consider the unstable elementary particles that people began to discover coming to the earth from space during the period between the World Wars, and that have been created artificially at large laboratories beginning in the second half of the 20th century. If such a particle had no gravitational interaction but coupled more or less normally with other particles via the other known interactions (strong, electromagnetic, weak), and if it were traveling fast enough so that the energy of its motion would cancel the (negative) gravitational potential energy of another particle or particles with which it shared one of the other interactions (with enough left over to take care of other matters, depending on details), it would create the other particle or particles. In particular, a sufficiently fast electrically charged particle with no gravitational interaction would spontaneously radiate electromagnetic waves such as visible light, since the particle of electromagnetic waves, the photon, has a normal gravitational interaction. (The latter fact is shown by the bending of starlight that travels near the sun to get to us, among other ways.)
In this article I worked out the theory of such processes and calculated the rates at which they would take place. I noted that in fact no spontaneous emission of electromagnetic rays from certain electrically-charged particles coming to the earth is observed to take place. Therefore such particles have normal gravitational interactions.