Basically, antimatter has it's all "quantum numbers" inverted of it's normal counterpart, but it's energy content is not inverted. Strength of gravity is a meas

Basically, antimatter has it's all "quantum numbers" inverted of it's normal counterpart, but it's energy content is not inverted. Strength of gravity is a measure of the energy content, so antimatter should have normal gravity. If it doesn't that's some exciting news!