# Gravitational force of antimatter

1. Apr 1, 2012

### murongqingcao

Hi,

I have been confused about whether there is any gravitational force between antimatter as what have between matter....and also whether there is gravitational force between antimatter and matter?

Thanks
Ron

2. Apr 1, 2012

### Mark M

Hi Ron,

Remember, anti-matter is the same thing as matter, except with opposite characteristic (e.g. charge) , so that when they collide, they annihilate into a photon. So yes, they do have a gravitational pull.

3. Apr 1, 2012

### murongqingcao

Hi Mark:

Thanks for the help...then how about between matter and antimatter......is there any gravitational interaction between them which follows the 1/r^3 law before they collide with each other?

Thanks
Ron

4. Apr 1, 2012

Staff Emeritus
There is no 1/r^3 law. It follows the same 1/r^2 as matter does.

5. Apr 1, 2012

### DaveC426913

Yes, as far as we know, gravitationally, matter and antimatter are interchangeable.

6. Apr 1, 2012

### K^2

Has anybody actually tried to verify this experimentally?

7. Apr 2, 2012

### alexg

Antimatter has been created and stored for as long as 16 minutes. If it did not react normally in a gravitational field, it would have showed up in the containment unit.

8. Apr 2, 2012

### K^2

That's a few ions in a magnetic trap. I'm not sure the magnetic trap is designed to measure weight of the ions at all, and if it is, how precise can it be? Got any refs that actually cite measured gravitational mass?

9. Apr 2, 2012

### alexg

I'm trying to find something on Cern's website, but so far all I've got is the press piece.

http://www.livescience.com/15270-physicists-weigh-antimatter-amazing-accuracy.html

Ah, here's the Cern piece.

http://press.web.cern.ch/press/PressReleases/Releases2011/PR10.11E.html [Broken]

Last edited by a moderator: May 5, 2017
10. Apr 2, 2012

### K^2

That's inertial mass, not gravitational.

P.S. I don't want to sound like a crazy person who thinks they are not equivalent. But it would be really neat to see an experiment showing that anyhow.

Last edited: Apr 2, 2012
11. Apr 2, 2012

### DaveC426913

That's why I said 'as far as we know'. We haven't really made enough to easily do the experiment.

12. Apr 2, 2012

### murongqingcao

Hi Guys:

Thanks for all the kind response....sorry for that r^3 mistake...it has been long since I touched the formula in school......

I am not a physics professional....my interest on the issue is from philosophical perspective.........now based upon your responses I could assume that when a huge mass of matter and a huge mass of antimatter are near by, they would be pulled towards each other by the gravitional force like the one to pull matter into the black hole.......and the force would follow the relation GmM/r^2........so an antimatter black hole could indeed merge with a matter black hole (that would be brilliant, right), since they don't push each other away but instead pull each other closer.........that solves my confusion.

Thanks

13. Apr 2, 2012

### DaveC426913

No. The moment any matter came into contact with antimatter they would annihilate in a burst of gamma rays. Depending on what masses we're talking about (maybe asteroids, maybe stars) the bodies might not even be solid, they might be gaseous. Which means they have an envelope of matter around them. The annihilation and gamma ray bursting might begin while the bodies are still some distance apart.

You would not get a black hole; they would not co-exist in the same place.

14. Apr 2, 2012

### murongqingcao

Dave:

Thanks for the clarification about "The annihilation and gamma ray bursting might begin while the bodies are still some distance apart."....

By the way, I was not meaning that the matter and antimatter form a black hole together.....I was saying that if there is an ANTIMATTER BLACK HOLE, and there is another MATTER BLACK HOLE.....they might not be very close to each other.....however, since black holes are of huge mass, so that there might be great pulling force between them because of the gravitation........based on your response, I guess we should say that when two such black holes are moving towards each other because of gravitational pull, the annihilation might happen before they are even physically close to each other (say, a few hundred lightyears away), right?

Thanks again

15. Apr 2, 2012

### Staff: Mentor

Black holes are easy to describe, you just need their mass (or energy), their charge and their angular momentum. There are no "matter black holes" or "antimatter black holes". Both are identical.
What they carry around outside their Schwarzschild radius may be different and depends on their origin, but that is a different story.

16. Apr 2, 2012

### K^2

Well, the matter and anti-matter black hole would carry a whole bunch of opposite quantum numbers, but yes, they don't make any difference to the outside, and once the black holes merge, it's not like radiation has any better chance of escaping than matter. You really shouldn't see a difference.

17. Apr 2, 2012

### murongqingcao

mfb/K^2:

Thanks for the response....as I understand that both of you are saying that no matter what are within the black hole, there is no longer any difference between antimatter or matter......anything pulled into a black hole become part of the mass and contribute to the charge and angular momentum.....thanks for the clarification....

but this causes me another confusion......I have heard people questioning why our universe only has matter and no antimatter is observed.........but based uopn your response, it seems that the answer could be as simple as that the missing antimatter are all in some black holes, right?

Thanks

18. Apr 2, 2012

### niklaus

There is an experiment in the works at CERN that attempts to measure the effect of earth's gravity on a antihydrogen beam. I don't think there are any results yet, but here is the website: http://aegis.web.cern.ch/aegis/home.html

19. Apr 2, 2012

### murongqingcao

niklaus:

Thanks for the link.....it seems that they are trying to confirm that the gravity between matter and antimatter would be the same as the gravity between matter and matter....let's wait and see what they would tell us.......

however, based upon the response in this thread I feel that theoretically people believe that the gravity between matter and antimatter should be the same as what is between matter and matter, right?

Thanks

20. Apr 2, 2012

### niklaus

Yes, it would be a big surprise if it wasn't the same, but we don't know for sure until we measured it.