When it comes to antimatter, physicists have an embarrassing problem. Ask them whether a lump of the stuff would fall to Earth or be repelled by it, they’ll shuffle their feet and stare at their shoes.
The truth is that nobody knows; and not for lack of trying. Various attempts to drop antimatter and see where it goes have all been inconclusive.
But the mystery could now be solved by a latecomer to the field of antimatter research. Today, Dragan Hajdukovic, a physicist at CERN near Geneva, says that the current generation observatories designed to see neutrinos could answer this question.
And he takes an unconventional view of things. He points out that particle-antiparticle pairs are constantly leaping in and out of existence in any field sufficiently strong to allow this phenomenon.
Normally, gravity is too weak to support this process. However, he says that all changes inside a black hole where field strengths reach extraordinary values. Here, Hajdukovic calculates that the field ought to be strong enough to generate a regular stream of neutrino-antineutrino pairs.
If gravity attracts both matter and antimatter, then we’ll be none the wiser since matter can never escape from a black hole and we’d never see either of these particles.
But if gravity repels antimatter, the antineutrinos would be hurled out of the black hole with great energy. “While neutrinos must stay confined inside the horizon, the antineutrinos should be violently ejected,” says Hajdukovic,
That would make black holes powerful antineutrino sources. Hajdukovic calculates that the supermassive black holes at the centre of the Milky Way and Andromeda galaxies should be bright enough to be seen by the generation of the neutrino telescopes currently being built.
The biggest and most sensitive of these is IceCube, a detector currently being assembled in the ice beneath the South Pole. It should be complete next year.
Hajdukovic gives one caveat, however. He says that the discovery of antineutrinos streaming from black holes would not automatically settle the question of which way antimatter falls. The reason is that another previously unknown force may have generated the neutrino antineutrino pairs inside the balck hole. That’ll require further investigation.
Either way, that’d be a mighty interesting discovery. Let’s hope the guys at IceCube have their hi-tech lens cloths at the the ready.
Ref: arxiv.org/abs/0710.4316: Can The New Neutrino Telescopes Reveal The Gravitational Properties Of Antimatter?