Does negative mass have the same affect on spacetime as "positive?" mass with respect to gravity? Just read a BBC article that says peeps are playing with negative mass fluid...guy says "With negative mass, if you push something, it accelerates toward you," uh what? Also with the "law" that massless things must go c, massive things less than c....I can't help but intuit a negative mass would mean must go ftl. Also, when reading negative mass can I take that to be the same as negative energy?