# How does gravity react with anti matter?

**URL:** https://boards.straightdope.com/t/how-does-gravity-react-with-anti-matter/778983
**Category:** Factual Questions
**Created:** [February 4, 2017, 3:14pm UTC](https://boards.straightdope.com/t/how-does-gravity-react-with-anti-matter/778983 "2017-02-04T15:14:05Z")
**Posts on this page:** 1
**Showing post:** 80

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### Author: ![Pasta](https://avatars.discourse-cdn.com/v4/letter/p/ecccb3/32.png) [@Pasta](https://boards.straightdope.com/u/Pasta)
#### Post date: [November 7, 2023, 5:13am UTC](https://boards.straightdope.com/t/how-does-gravity-react-with-anti-matter/778983/80 "2023-11-07T05:13:24Z")

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> [@HoneyBadgerDC](#):
>
> Does it theoretically generate more energy than what it took to collide them?

You get all the energy out that you put in, and that includes the rest mass of the particles (times _c_2, because our units are stupid) plus their kinetic energy. So, if you didn’t have to spend any energy to make the bulk masses of those particles and/or get them up to whatever speed they have, then you “win”.

> [@DSeid](#):
>
> Or … if there actually are additional spatial dimensions curled up … really close but traveling differently through those dimensions than regular matter so virtually never the twain be met, or observed … except maybe by gravity I guess, since in that imagining gravity travel through those dimensions?

We’ve been down that road, though. If you want to revisit such speculation, I’m happy to, but as a starting point you might want to revisit the problems we discussed [last time](https://boards.straightdope.com/t/how-do-we-know-that-matter-dominates-our-universe/645364/21). To summarize that discussion (wow, ten years ago): one can’t arbitrarily manipulate language in a story-like fashion and have it make sense as a model of physics. We understand the properties of antimatter extremely well. We make it everyday and study it everyday. It’s not something that acts in any quirky way. It’s acts just like boring ol’ matter, aside from one nuance in the weak force of the Standard Model that means matter and antimatter interaction rates can, in some specific cases, differ.

> [@Chronos](#):
>
> Assuming we’re talking about a low-KE annihilation (where the only source of energy is the rest mass of the protons themselves), wouldn’t pions be the only option, and not more than a handful of them?

Yes, I was referring to low-KE (essentially at rest) annihilation. The proton and antiproton together represent 1.9 GeV of rest mass. A pion has a rest mass around 0.14 GeV. In principle there’s enough oomph in the annihilation to make thirteen pions, though such a crazy final state would be heavily disfavored for phase space reasons. More typical is half a dozen or so, with some energy left over for outgoing pion kinetic energy. But there are loads of others mesons light enough to be produced in the annihilation, though of course without as many at once.

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