Physicists have long wondered if the gravitational interaction between antimatter and matter might be different than that between matter and itself. Do atoms made of antimatter, like antihydrogen, fall at a different rate to those made of matter, or might they even fall up — antigravity? There are many arguments that make the case that the interaction must be the same, but no-one has ever observed what an anti-atom does in a gravitational field – until now.
