Anti-matter atoms to address anti-gravity question (BBC)

[eppur_se_muova]

The question of whether normal matter's shadowy counterpart anti-matter exerts a kind of "anti-gravity" is set to be answered, according to a new report.

Normal matter attracts all other matter in the Universe, but it remains unclear if anti-matter attracts or repels it.

A team reporting in Physics Review Letters says it has prepared stable pairs of electrons and their anti-matter particles, positrons.

A beam of these pairs can be used to finally solve the anti-gravity puzzle.
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more: http://www.bbc.co.uk/news/science-environment-16756457




OK, I don't understand why this can't be done with a beam of positrons or antiprotons alone -- but this is an ingeniously simple experiment, in a way. Just transmit a beam of positronium at low velocity and see if it bends downward (gravity attracts both ?^- and ?⁺) or stays level (gravity attracts ?^-, repels ?⁺). A beam of positrons or antiprotons would either curve upward (antigravity) or downward (gravity), so I would think that would be a more sensitive test.

[dimbear]

1. It's astonishing this question is still open. Many experiments have been tried, and

results have been reported several times, only later to be refuted. Of course the problem is the very short time you're allowed for the falling to take place. Before the kablooie.

[caraher]

2. I think the advantage is positronium is electrically neutral

Because electromagnetic forces are so much stronger than gravitational forces, it's hard to be sure that any effect you might see might not be due to stray electric or magnetic fields in your experiment if you do this with a charged antimatter particle.

That said, I don't think there's much good reason to expect a gravitational repulsion. The main reason to do the experiment is to verify what everyone expects - there's always a window for surprises. But in this case it's a tiny one.

[eppur_se_muova]

3. Of course ! :slaphead:

Exactly the kind of thing I should have thought of, and didn't. Even a stray magetic field could skew results.