<p>This is an interesting question and in fact so interesting that folks are working hard to measure the <em>gravitational</em> mass of antiparticles. In  <a href="https://physics.stackexchange.com/q/241060/83380">What is the Current Status of Measurement of the Gravitational Mass of Antimatter?</a> I mention some of the work and answers address the status a few years ago and answers to the earlier <a href="https://physics.stackexchange.com/q/139545/83380">Has the gravitational interaction of antimatter ever been examined experimentally?</a> summarize previous work.</p>
<p>See in CERN News:</p>
<ul>
<li>November 2018: <a href="https://home.cern/news/news/experiments/new-antimatter-gravity-experiments-begin-cern" rel="nofollow noreferrer">New antimatter gravity experiments begin at CERN</a></li>
<li>March 2021: <a href="https://home.cern/news/press-release/experiments/alpha-cools-antimatter-using-laser-light-first-time" rel="nofollow noreferrer">ALPHA cools antimatter using laser light for the first time</a></li>
</ul>
<p>It is generally believed that antimatter will have the same sign and magnitude of gravitational mass as &quot;normal&quot; matter but the last word of <a href="https://physics.stackexchange.com/a/241181/83380">@AnnaV's answer</a> is... &quot;Patience&quot; :-) We have to wait a little longer for careful, precision measurements. Handling antimatter is already hard, and suspending anti-hydrogen for long periods of time requires ultrahigh vacuum, lasers, and patience.</p>

CC BY-SA 4.0
2021-06-14T00:47:14.003Z
2021-06-14T00:47:14.003Z
uhoh
<p>Is the mass of antimatter negative or positive For example, the mass of the electron 9.1×10^(-31), does this mean that the mass of the positron -9.1×10^(-31)?</p>

CC BY-SA 4.0
2021-06-13T18:43:45.790Z
This would be better on Physics where indeed it has been answered several times : https://physics.stackexchange.com/questions/241060/what-is-the-current-status-of-measurement-of-the-gravitational-mass-of-antimatte https://physics.stackexchange.com/questions/394502/is-it-true-that-matter-and-antimatter-must-have-same-mass  https://physics.stackexchange.com/questions/249459/   The answer is matter and antimatter have the same positive mass (inertial and gravitational) although this is not empirically proven for gravitational mass.
James K
CC BY-SA 4.0
2021-06-14T00:38:25.620Z
This is an interesting question and in fact so interesting that folks are working hard to measure the *gravitational* mass of antiparticles. In [What is the Current Status of Measurement of the Gravitational Mass of Antimatter?](https://physics.stackexchange.com/q/241060/83380) I mention some of the work and answers address the status a few years ago and answers to the earlier [Has the gravitational interaction of antimatter ever been examined experimentally?](https://physics.stackexchange.com/q/139545/83380) summarize previous work.
uhoh
CC BY-SA 4.0
2021-06-14T02:33:48.560Z
I’m voting to close this question because it's not about Astronomy but instead about more fundamental aspects of matter. It would be on-topic in Physics, but as comments (and answer(s)) show it's already been addressed there.
uhoh
<observational-astronomy>
Is the mass of antimatter negative or positive?
Red Bel
# Is the mass of antimatter negative or positive?

(Asked by: username_0 on 2021-06-13)

Is the mass of antimatter negative or positive For example, the mass of the electron 9.1×10^(-31), does this mean that the mass of the positron -9.1×10^(-31)?

**Tags:** observational-astronomy
> **Comments:**
> **username_1**: This would be better on Physics where indeed it has been answered several times : https://physics.stackexchange.com/questions/241060/what-is-the-current-status-of-measurement-of-the-gravitational-mass-of-antimatte https://physics.stackexchange.com/questions/394502/is-it-true-that-matter-and-antimatter-must-have-same-mass  https://physics.stackexchange.com/questions/249459/   The answer is matter and antimatter have the same positive mass (inertial and gravitational) although this is not empirically proven for gravitational mass.  
> **username_2**: This is an interesting question and in fact so interesting that folks are working hard to measure the *gravitational* mass of antiparticles. In [What is the Current Status of Measurement of the Gravitational Mass of Antimatter?](https://physics.stackexchange.com/q/241060/83380) I mention some of the work and answers address the status a few years ago and answers to the earlier [Has the gravitational interaction of antimatter ever been examined experimentally?](https://physics.stackexchange.com/q/139545/83380) summarize previous work.  
> **username_2**: I’m voting to close this question because it's not about Astronomy but instead about more fundamental aspects of matter. It would be on-topic in Physics, but as comments (and answer(s)) show it's already been addressed there.  

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## 1 answers

### Answer by username_2 on 2021-06-14. Score: 0

This is an interesting question and in fact so interesting that folks are working hard to measure the *gravitational* mass of antiparticles. In [What is the Current Status of Measurement of the Gravitational Mass of Antimatter?](https://physics.stackexchange.com/q/241060/83380) I mention some of the work and answers address the status a few years ago and answers to the earlier [Has the gravitational interaction of antimatter ever been examined experimentally?](https://physics.stackexchange.com/q/139545/83380) summarize previous work.

See in CERN News:

* November 2018: [New antimatter gravity experiments begin at CERN](https://home.cern/news/news/experiments/new-antimatter-gravity-experiments-begin-cern)
* March 2021: [ALPHA cools antimatter using laser light for the first time](https://home.cern/news/press-release/experiments/alpha-cools-antimatter-using-laser-light-first-time)

It is generally believed that antimatter will have the same sign and magnitude of gravitational mass as "normal" matter but the last word of [@AnnaV's answer](https://physics.stackexchange.com/a/241181/83380) is... "Patience" :-) We have to wait a little longer for careful, precision measurements. Handling antimatter is already hard, and suspending anti-hydrogen for long periods of time requires ultrahigh vacuum, lasers, and patience.


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