Why antimatter does not give rise to anti-gravitation

One of the first thing I understood when I became interested with the concept of negative mass in the 1990’s is that it is not possible to consider that perhaps antiparticles have negative masses, in the sense that they would give rise to gravitational repulsion. It amazes me, therefore, that many of the researchers who consider the idea that there may exist negative-mass particles still believe that those particles could actually be the antimatter particles we routinely observe in accelerator experiments. Those researchers suggest that we should try to measure the gravitational acceleration of antimatter particles in the gravitational field of the Earth to find out if indeed antiparticles are gravitationally repelled by our positive-mass planet. But while it is certainly useful to carry out those experiments, even if only to confirm that antimatter actually falls down, it is incorrect to suggest that theory may require or even merely allow those particles to have negative mass.

Our best understanding of antiparticles was that proposed by Richard Feynman in 1949 and it requires assuming that positrons are merely negatively-charged electrons propagating backward in time (which thus appear to have positive charges when observed forward in time). Implicit in Feynman’s approach is the hypothesis that those electrons traveling back in time actually have negative energies. Yet the energy of a positron is always measured to be positive form the forward in time viewpoint, because one only measures energy changes as they appear to take place from the forward in time perspective. Thus, it is still true that positrons have a positive energy from a phenomenological perspective, because when considered from the viewpoint relative to which they appear to propagate forward in time, they do have positive energy and therefore, also, a positive mass. If we consider mass to simply be a measure of the energy of a particle at rest, it would then appear inappropriate to assume that antiparticles, like the positron, have negative masses and could respond anomalously to a given gravitational field, or even produce an anomalous gravitational field.

What I have suggested in my first report from 2006, however, is that it may be possible for certain positive-energy electrons to propagate backward in time, or for some negative-energy electrons to propagate forward in time. But if the energy of interaction fields is to remain well-defined it is necessary to assume that those particles cannot interact with ordinary matter other than through the gravitational interaction, which means that celestial objects composed of such matter would remain dark from our point of view. Those would then be the only electrons that could potentially give rise to anti-gravitation in the sense that those particles would produce gravitational fields that would repel ordinary matter, while they would also be repelled by ordinary, positive-mass matter. If antimatter was abundant enough that there could exist antimatter stars in our universe, it is certainly true that those stars could be observed, but one can only conclude that no such an object could have negative mass.

One of the particularities of the model I developed around the more appropriate concept of negative-energy matter discussed in my first report is that there must be a symmetry under exchange of positive- and negative-mass particles, which requires negative-mass particles to also be submitted to mutual gravitational attraction among themselves, which is contrary to what traditional assumptions regarding the concept of negative energy would require us to believe. What this means is that only a modified, general theory of relativity could accommodate such a negative-mass concept. In a later report I have shown how this can be achieved without rejecting the basic mathematical framework of relativity theory. In fact it appears that the generalized gravitational field equations so obtained are even more elegant and simple than the original theory in the presence of a non-zero density of vacuum energy. But it must be clear that those results do not provide additional weight to the hypothesis that anti-particles give rise to anti-gravity.