Antimatter falling upwards because of gravity?

[rollcast]

http://www.physorg.com/news/2011-05-cern-scientists-confine-antihydrogen-atoms.html

One of the big questions in physics is whether antihydrogen atoms occupy the same energy levels as hydrogen; others of course want to know how it reacts to gravity, as some have speculated that antihydrogen might actually fall up, or behave in other unexpected ways. The experiments going on at CERN might just answer both those questions, and more.

Up next for the ALPHA team are plans to cool a small bunch of antihydrogen atoms in such a way as to allow them to watch as it either rises or falls due to gravity, thus answering one of the more exciting questions regarding antimatter, in perhaps just the next few months.

When I read this I couldn't get my head around it, they are try to suggest that something with mass would be repulsed by gravity instead of attracted by it. This would mean the antihydrogen has a mass of a negative quantity, if I'm getting this so far.

However negative quantities as far as I understood would be highly unlikely as that would be like the same as saying that triangle has side of length -10cm?

Have I missed out a large part of the physics of this or am I just stupid

Thanks
AL

 

[KingNothing]

As it said, it's purely speculation, at least for the time being. It doesn't really make any sense to me to be honest. I say that because there's only so far you can take the "it's exactly opposite" thought process.

 

[Ryan_m_b]

I'm not an expert but I'm really not sure why antimatter would ever react to gravity negatively. As all ways wikipedia has a good article http://en.wikipedia.org/wiki/Gravitational_interaction_of_antimatter

 

[pallidin]

I agree with the above comments. That anti-matter has anti-gravity properties has no basis(so far)
An interesting comment from that link said something like "well, why doesn't a lone anti-proton fall up?"
To be sure, I'm not even close to being an expert, so I guess I'll see whatever results come about.

 

[Vanadium 50]

It is all but certain that antimatter falls down. If it fell up, energy conservation would be violated, and we would see composition dependent gravitational forces in Eotvos-type experiments. Would it be nice to see for certain? Sure...but nobody expects anything besides "it falls down at 9.8 m/s²"