Does antimatter behave the same way as matter under the influence of gravity, or does antimatter even fall up? One of the keys lies in free-fall experiments to measure the acceleration of gravity, g. These are notoriously difficult with charged particles, but first measurements on neutral antimatter have recently been made and there are plans for dedicated experiments on antihydrogen at CERN with AEgIS and GBAR. There are also schemes to study gravitational effects in positronium and muonium, which are neutral atom-like systems consisting of a particle – an electron or a muon – and its antiparticle.

Read more: "Antigravity matters at WAG 2013" – CERN Courier