Do two specks of antimatter experience antigravity between each other?

Question

Do two specks of antimatter experience antigravity between them? If no is the answer then what 2 specks may ever be the cause of that?

Possible duplicates: https://physics.stackexchange.com/q/139545/2451 , https://physics.stackexchange.com/q/83307/2451 and links therein. — Qmechanic, Oct 15 '20 at 16:28
Antineutron repelled by gravity?, Anti-matter repelled by gravity - is it a serious hypothesis? — mmesser314, Oct 15 '20 at 18:08

score 2 · Answer 1 · answered Oct 15 '20 at 16:20

Antimatter (to the best of our knowledge) does not behave differently than normal matter in regards to gravitation. Particles and their respective antiparticles have equal mass (there is no concept of 'antimass', unlike how we can invert electric charge).

So, if we had two balls of matter of mass $M$ and $m$ set some distance $r$ apart, they would have a gravitational potential (at a Newtonian level) of $U = -\frac{G M m}{r}$.

If we were to replace the balls with their antimatter equivalents, nothing would change.

Even more, if we were to replace one of the balls with their antimatter equivalent (so we have one matter ball and one antimatter ball), the gravitational potential would be the same $U = -\frac{G M m}{r}$.

@ThusharGR Maybe we could interpret it as a dual symmetry with the existence: positive mass exists, negative mass does not :-) — peterh, Oct 29 '20 at 09:54

score 1 · Answer 2 · answered Oct 15 '20 at 16:16

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The short answer is no. Gravity as far as we know it is attractive. The attraction depends on the masses of the bodies involved (or energy densities, more generally). However antiparticles have opposite quantum numbers but same mass as particles. To a very good precision they are equal, however whether they are exactly equal is currently being investigated, nevertheless they remain positive masses and thus suffer gravitational attraction not repulsion. Here there is a nice easy read about anti-matter (https://www.scientificamerican.com/article/what-is-antimatter-2002-01-24/) if you want to know more.

answered Oct 15 '20 at 16:16

ohneVal

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So its just anti-matter but not anti-mass? – Thushar G R Oct 15 '20 at 16:19
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Correct, the "anti" part corresponds to quantum numbers, such as electric charge, spin and other such charges – ohneVal Oct 15 '20 at 17:12
So I understand the number referring to mass cant be quantum, right? – Thushar G R Oct 15 '20 at 17:15
if by quantum you mean discrete, no – ohneVal Oct 16 '20 at 07:18

Do two specks of antimatter experience antigravity between each other?

2 Answers2