>Negative masses are a hypothetical form of matter that would have a type of negative gravity – repelling all other material around them. Unlike familiar positi

>Negative masses are a hypothetical form of matter that would have a type of negative gravity – repelling all other material around them. Unlike familiar positive mass matter, if a negative mass was pushed, it would accelerate towards you rather than away from you. Pretty sure the author means both. A continuously accelerating system seems "unphysical", but we have an example already: the accelerating expansion of the universe.