How do we Know That Half of the Galaxies are not Anti-matter?

Most recent answer: 07/07/2016

Hi - How do we know that half of the Galaxies are not Anti-matter? Cheers,Joe
- Joe Lozowski (age 55)
South Lake Tahoe, CA USA

Hello Joe,

Good question.  Astronomers now search the skies for all kinds of signals, microwaves, x-rays, light, at all kinds of different wavelengths and frequencies.   Now if there were an anti-galaxy it would very likely have an ordinary-matter galaxy neighbor.   At the boundary between these two there should be annihilation radiation which results from matter -- anti-matter collisions.   No particular radiation of this type has been seen. 

The reason why there seems to be only matter and not much anti-matter in the observable universe is a complete mystery.   The laws of physics as we know them look almost completely symmetric between the two.  Maybe we will figure it out some day.


(published on 07/07/2016)