What would happen if you had a ball of antimatter?

[Physt]

If you had a ball of matter and anti-matter in a vacuum and threw them at each other - would they just blow apart and go largely unreacted?

What about in atmosphere - would the ball of anti-matter blow up or form a shell of exploding material around it insulating it like the boiling of liquid nitrogen on your hand keeps it from freezing you? How long would such a reaction take to complete for a baseball of anti-matter at 1 atmosphere?

 

[ChrisVer]

If you hit a ball of antimatter with a ball of matter, then they will "explode"= they will give photons of the same energy as the two balls' masses...

What do you mean blow up or form a shell of exploding matterial? The "reaction" (annihilation) will happen really fast (in macroscopic world) if the matter meets its antimatter...

 

[mfb]

If you had a ball of matter and anti-matter in a vacuum and threw them at each other - would they just blow apart and go largely unreacted?

That depends on the speed and size. If you do it slow enough, initial annihilation reactions will quickly push both balls away from each other. If they survive without getting blown apart from the released energy, they might escape without a large reaction. The same can happen with fission weapons, by the way, if they reach criticality too slowly.

In the atmosphere, the ball of antimatter would quickly evaporate from initial annihilations on its surface. With a reasonable size (e.g. similar to a nuclear bomb, a baseball-sized ball fits here), most of the annihilation energy escapes the annihilation region and your reaction gets very violent until all the antimatter annihilated.

If you hit a ball of antimatter with a ball of matter, then they will "explode"= they will give photons of the same energy as the two balls' masses...

Muons and neutrinos (from charged pion decays) get a significant fraction of the energy in baryon annihilations.

 

[ChrisVer]

pion decays?

 

[mfb]

What is the question?
Nucleon/antinucleon annihilations mainly produce pions (strong interaction >> electromagnetic interaction). Neutral pions decay to two high-energetic photons, charged pions mainly decay to a muon and a neutrino.

 

[ChrisVer]

oh ok then,,, I didn't think of Nucleons

 

[mfb]

Over 99.95% of the energy is in the nucleons. The electron/positron contribution is very small.

 

[nikkkom]

How long would such a reaction take to complete for a baseball of anti-matter at 1 atmosphere?

Initial reaction on the surface would quickly (microseconds or even less) turn the ball and surrounding air into an expanding fireball of hot plasma, quite similar to a nuclear bomb detonation. The annihilation inside the fireball will continue until all antimatter is consumed, within some milliseconds.