Question: what is anti-matter

David Pyle answered on 23 Mar 2011:

Anti-matter was created at the same time as matter during the Big Bang. For every particle of matter (e.g. neutron, electron) formed, a particle of antimatter was created (e.g. antineutron, positron). But since antimatter is annihilated (converted back to energy) when it comes in contact with matter, most of the antimatter produced in the Big Bang was promptly destroyed. For some reason there was an asymmetry in the Bg Bang process, so that matter came to dominate our universe. Antimatter particles have been created (in high energy collisions in accelerators like the Large Hadron Collider); and they have also been isolated and assembled to make atoms of antihydrogen – for a few tenths of a second!