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This may be a very basic question, please excuse my lack of knowledge but I don't seem to understand the concept of anti-matter gravity.

Upon research, many sources align with the conclusion that anti-matter reacts to gravity similarly to matter. ie. that it space-time warps around its mass.

If we consider a particle/anti-particle pair we would expect and conclude that there is no gravity (warp in space-time) by this. ie. Just the vaccum of space.

However, if we consider them as separate particles, then their corresponding gravities -pulling spacetime in the same direction, would add together (since gravity is not reversed for anti-matter). We would expect to increase the total gravity as they approach each other (greater density of mass in space-time). However, as we know, a pair would have no gravitational effects.

It's hypothetical but to clarify; consider a plane vacuum with one particle and one antiparticle beginning to collide. Disregarding their electrical attraction, they each warp space-time in the same direction due to their masses. However, after the collision (as a pair) there is no gravity. So, how would their gravitational potentials dissipate and react as they approach each other and collide.

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    $\begingroup$ Why do you think a particle-antiparticle pair would not have gravity? $\endgroup$
    – march
    Commented Nov 1, 2023 at 21:08
  • $\begingroup$ because its space its just a vaccum. If I were in space and assume all planets, stars etc DNE, then I wouldn't be pulled in any direction since there would be no gravity? no warp in space time for me to follow $\endgroup$
    – cav3
    Commented Nov 1, 2023 at 21:36
  • $\begingroup$ I'm sorry; I don't follow at all. Are you asking about what occurs in the case when there are only two particles in the whole universe, and one is matter and one is antimatter? If so, then I'm not sure what the point of asking that is, but if not, then the answer is that it doesn't matter if it's antimatter or matter, they both act as if they had mass and interact gravitationally in the usual awy. Is there any way you can clarify? $\endgroup$
    – march
    Commented Nov 1, 2023 at 21:42
  • $\begingroup$ It's hypothetical but yes consider a plane vacuum with one particle and one antiparticle beginning to collide. Disregarding their electrical attraction, they each warp space-time in the same direction due to their masses. However, after the collision (as a pair) there is no gravity. So, how would their gravitational potentials dissipate and react as they approach each other and collide. $\endgroup$
    – cav3
    Commented Nov 1, 2023 at 22:04

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Take your example of a particle and it's antiparticle moving towards one another. Indeed they both warp spacetime the same way, since they have equal mass. However, it is false that after the collision there is no more gravity.

Probably what caused you to reach this conclusion is the wrong idea that it is mass that warps spacetime and causes a gravitational force. What actually warps spacetime is energy, mass being only a particular form that energy may take. When a particle-antiparticle pair meets, they do not annihilate into nothingness. This would violate conservation of energy, since the energy carried by each one (both due to their masses and their motion, the kinetic energy) would simply vanish.

Instead, what happens is that they become a new, neutral particle (usually photons, or light). These photons exit the collision with extremely high energies, given precisely by the sum of the energies from the masses and the motion of the original pair. Spacetime continues to be warped right after the collision, since all of the energy is still there, only in another form.

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  • $\begingroup$ so if space is filled with (energy of antiparticle)+(energy of particle), then, all of space is warped evenly with this uniform energy distribution. warp in space time is ________ where ----- is 0 energy. Then in theory, wouldn't one anti-particle or one particle have a reverse gravity effect? as (energy of one particle) < energy of antiparticle)+(energy of particle). Also does this mean that the total energy in the universe is non zero?. Thanks by the way, great answer. $\endgroup$
    – cav3
    Commented Nov 2, 2023 at 23:47
  • $\begingroup$ @cav3 those are many questions, and there is not enough space here to go into all of them in detail, but no, neither particles nor antiparticles have a reverse gravity effect. As to vacuum energy, you should not take the whole "particle-antiparticle pairs popping out of the vacuum" picture too seriously. While it helps in building intuition for some phenomena, pushing it too far leads to wrong conclusions. If there were actual (not virtual) particle-antiparticle pairs forming everywhere, they would annihilate into photons and the Universe would be everywhere very bright. $\endgroup$
    – Bairrao
    Commented Nov 3, 2023 at 21:42

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