>Antimatter has positive mass Specifically we know it has positive inertial mass due to its reaction to electromagnetic fields. The paper and experiments done

>Antimatter has positive mass Specifically we know it has positive inertial mass due to its reaction to electromagnetic fields. The paper and experiments done by the authors deal with its gravitational mass. Due to weak equivalence principle it's assumed those are the same and so far (for regular and now antimatter) experiments agree, but there's no theory unifying them. Hence GP's disappointment isn't entirely unjustified.