Don Herbison-Evans , firstname.lastname@example.org ,
Dirac's suggestion that electrons can have negative energy suggests that in these states they may display a negative mass . His suggestions of particles being holes in an infinite sea of of filled states of other particles also suggests that the holes would have negative mass.
There is no evidence yet that anti-particles are repelled gravitationally by the earth. Anti-particles formed in collision experiments in a cloud chamber of size say 3 metres, are typically moving at close to the speed of light and so would be observed for approximately 10-8 second, in which time they would drop a distance of 5 x 10-16 metre, which is beyond the resolution of observation systems in current cloud chambers. Even in an accelerator with a path length of 3 kilometres, the fall would only be 5 x 10-10 metre which is again beyond the resolution of observation in such instruments.
When particles formed early in the condensation from the Big Bang, it is tempting to suggest that equal numbers of particles with positive and negative masses were created. The particles of the same sign mass would attract each other gravitationally, and particles of opposite signs would repel each other gravitationally. Thus the initial cloud of particles would segregate into clumps of positive mass and clumps of negative mass.
Thus there is the possibility that half of the clusters of galaxies that we observe in space are composed of particles of mass opposite in sign to that of which our galaxy is made. The relationship of this to the observations of the Hubble Recession is unclear.
Priciples of Quantum Mechanics (3rd ed.),
Oxford University Press (1947), p. 273.
written 30 June 2016