Matter and matter attract each other. What about matter and antimatter? They repulse? Also attract?
We posed this question to Professor Andy Parker from Cambridge University and Jeffrey Hangst from CERN...
Andy - If you just take a positron and an electron, they attract each other because they've got opposite electrical charges. But a much more interesting question is if you make a matter atom and an antimatter atom, do they then attract each other? Because if they were two atoms, they would have a positive pull together from gravity. So an interesting question which I think Jeffrey might like to comment on is whether there's some anti-gravitational force related to antimatter...
Jeffrey - It’s a very fascinating question and an experimental one that another group here at CERN hopes to answer. The short answer is that nobody knows because physics is fundamentally an experimental science, but people are planning on doing that experiment. Maybe in five to ten years, we’ll have an answer. Most people don't think that there’s antigravity. In other words, that antimatter and matter repel each other, but there may be some slight correction to the attraction. That's what the current thinking is, that’s as far as it goes at any rate.
@monozuky asked the Naked Scientists: Matter and matter attract each other. What about matter and antimatter? They repulse? Also attract? What do you think? @monozuky, Wed, 19th Jan 2011
The relationship between particle and antiparticle is that they have the same mass (and spin, baryon number etc) but opposite charge. So, for instance, a proton and an anti-proton would be of opposite charge +1 and -1 (by definition) thus they would be attracted to each other - they would then annihilate each other to give off energy a/o other particles.
I used to believe there was a chance antimatter could exhibit antigravitational properties. It turns out I was wrong. We have made antihydrogen now, and it exhibited no antigravitational properties. QuantumClue, Sun, 30th Jan 2011
But the CERN experiment write-up that I read only had single anti-hydrogen atoms held at any one time (they got 30ish over a few hundred runs) - there is no mechanism for ascertaining gravitational attraction/repulsion for a single atom. I haven't read any more recent articles on this - but it is clear that it is ongoing; the latest podcast had two anti-matter physcists and one refered to the fact that they can now isolate for 10^3 seconds whereas the article below is in the 10^-3 seconds range
The really interesting question to me is what it say about particles, be they positive or negative. They annihilate each other, don't they?