Negative Mass - Gravitational Interaction of Antimatter

Gravitational Interaction of Antimatter

Virtually every modern physicist suspects that antimatter has positive mass and should be affected by gravity just like normal matter, although it is thought that this view has not yet been conclusively empirically observed. It is difficult to directly observe gravitational forces at the particle level: at such small scales, electric forces tend to overwhelm gravitational interactions, especially since the methods of antimatter production currently in use typically generate very energetic particles. Furthermore, antiparticles must be kept separate from their normal counterparts or they will quickly annihilate. It is hoped that the ATRAP antimatter experiments will be able to make direct measurements.

Bubble chamber experiments are often cited as evidence that antiparticles have the same inertial mass as their normal counterparts, but a reversed electric charge. In these experiments, the chamber is subjected to a constant magnetic field which causes charged particles to travel in helical paths; the radius and direction of which correspond to the ratio of electric charge to inertial mass. Particle–antiparticle pairs are seen to travel in helices with opposite directions but identical radii, implying that the ratios differ only in sign; but this does not indicate whether it is the charge or the inertial mass which is inverted. However, particle–antiparticle pairs are observed to electrically attract one another, often as the prelude to annihilation. This behavior implies that both have positive inertial mass and opposite charges; if the reverse were true, then the particle with positive inertial mass would be repelled from its antiparticle partner.