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Comment by ars | Hacker News Reader

I hope they will finally definitely answer if anti-matter also has anti-gravity.

Not a single scientist thinks it does, but it's one of those things you just want confirmed.

Antimatter has opposite charge, not opposite mass. It has the exact same magnitude and sign of gravitational interaction as normal matter. It's never been directly observed, but I'm not aware of any models that predict otherwise. http://en.wikipedia.org/wiki/Gravitational_interaction_of_an...

Maybe you're thinking of exotic matter? http://en.wikipedia.org/wiki/Exotic_matter

Isn't that why we have experiments, to check the predictions of models?

I would have thought this had already been tested on antiprotons, but I'm not seeing any references for it. Just a note that results from testing anti-hydrogen for gravity should be had in the next few years. Maybe containing something so charged overwhelms gravity?

Most antiprotons move too fast to test. Plus the charge is strong enough to overwhelm any signal from gravity.

As has been alluded to, gravity is an extremely weak force, so any gravitational effect is easily masked by electroweak forces until you accumulate a very significant mass. There's no way they can measure this on a single atom.

But easy to test with 2 atoms! Smash them together at a high enough speed where e=mc^2 says they would create a black hole. If they are destroyed in a blip of Hawking radiation, they had gravity!

Doesn't sound like it would work.

I'm not sure it's easy to distinguish the Hawking radiation from the stuff that comes out otherwise. I guess the Hawking radiation should be thermal but for a borderline small black hole there will be few particles.

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