Does antimatter fall up? It turns out, we don't know. Our scientists have too little experience with the stuff, as it tends not to last very long once we produce it. But a series of new experiments being planned at Fermilab and CERN could provide some insights.
The experiments involve testing the effect of gravity on antimatter by producing beams of antihydrogen and measuring how gravity affects the beam. The experiments are highly challenging, as the detectors that we would use to identify the position of the antihydrogen beam are made of normal matter, which tends to react rather violently with antimatter.
Most scientists seem to think that the antimatter beams will behave exactly the same as normal matter beams of the same mass and electrical charge would. But they're hopeful of seeing something that they don't expect. After all, results that do not conform to expectations are where newer, more advanced scientific theories come from.