Well intervals by definition don't point anywhere, they're scalars! Relativity says: E^2 = m^2 - p^2 If we treat antimatter as normal matter moving backwa

Well intervals by definition don't point anywhere, they're scalars! Relativity says: E^2 = m^2 - p^2 If we treat antimatter as normal matter moving backwards in time, with negative energy - then energy reverses sign, so any time we connect back to experiments we get positive energy. Ok, cool. Even in this view nothing moves faster than c. If we permit faster than c, then either E or M has to become imaginary to get a negative sign after squaring. Imaginary energy is even weirder than negative energy and is well above my pay grade; google "John Baez tachyon" for more.