I have questions: would two clumps of antimatter repel each other? Does antimatter have negative mass going forward in time? Does matter attract or repel antimatter?
Didn't you claim, at one point, to be studying physics? Read this and then ask any questions that remain: https://en.wikipedia.org/wiki/Antimatter
Gravitationally, no. Electrically, maybe; they would repel if both clumps had the same (non-zero) electrical charge. No. It has regular, ordinary mass, just like "normal" matter. Gravitationally, matter and antimatter attract. Electrically, it depends on the net charges on the matter and the antimatter.
You may be thinking of negative matter, a hypothetical form of matter proposed by Robert Forward. It has the opposite gravitational, inertial and rest mass properties as normal matter. It is not antimatter. It has never been observed. https://arc.aiaa.org/doi/abs/10.2514/3.23219?journalCode=jpp
That's postulating the existence of, for example, a "negative energy" electron, but this is not the same as a positron, which is the antimatter version of the electron. In this model, the positron is the "hole" left behind in the "Dirac energy sea" if a negative energy electron absorbs enough energy to be converted to a positive energy electron. This would be an example of "pair production" where an electron and positron are created from two high energy photons. In other words, the "hole" left behind is not the same as the object that vacated the area to make the "hole".
I agree with exchemist I normally don't say there are stupid questions but this is a stupid question, it doesn't have imaginary time nor negative mass, Antimatter just has opposite charges and Anti-colors at specific states such as the positron versus electron or Proton versus Anti-proton, the only difference is their Anti-color and charge not other things. The Properties of the matter never change just the properties of their state.
Wheeler and Feynman hypothesized back in the 1940's that antiparticles might be ordinary particles moving backwards in time. It 'explained' opposite charge, opposite spin, and such, but logically implied anti-gravity too i.e. antiparticles would fall up not down in a gravity field. But that had a big hitch. Universality of the equivalence principle would be strongly violated since cloud chamber or bubble chamber tracks of charged antiparticles curving in magnetic fields e.g. positrons are consistent with their having positive inertial mass. There are still adherents to the notion antiparticles anti-gravitate, and expensive experiments set to use anti-atoms to confirm either way have iirc been approved but afaik not yet performed. Update. Found this link: https://www.forbes.com/sites/starts...al-science-is-about-to-find-out/#656303e49a79 I rate the chances of an 'earthshaking upset' as about the same as the sun not rising tomorrow.
In general, negative energy isn't a problem. Energy isn't stuff; it's just a number. For example, the gravitational potential energy of two masses separated by distance r is $U=-GMm/r$. (See the minus sign?)
I concur as well! I think the hypothetical Alcubierre drive requires negative mass. If ever found, perhaps that warp bubble travel idea could be pursued in practice. Interstellar travel, at desirable speeds, could result.
