Originally posted by mlprior
Yes, in fact antimatter is unstable in a world made up of matter because it immediately combines and anhililates. I did not say that it does not exist and it does for a very small time. I said that it is unstable.

http://conferences.fnal.gov/lp2003/forthepublic/matter/

The word 'unstable' usually means that something if left alone will decay into smaller parts. This is not the case for anti-matter.

I also believe that in space where there is not much matter of any kind, anti-matter probably has fairly long life times.

Originally posted by mlprior
Yes, in fact antimatter is unstable in a world made up of matter because it immediately combines and anhililates.

Is matter unstable too?

Originally posted by mlprior
Yes, in fact antimatter is unstable in a world made up of matter because it immediately combines and anhililates. I did not say that it does not exist and it does for a very small time. I said that it is unstable.

http://conferences.fnal.gov/lp2003/forthepublic/matter/

Not all antimatter "immediately combines and annihilates". If there is no matter to interact with, it's just as stable as the matter equivalent of the particle you're considering. Also, antineutrinos have little problem flying straight through the Earth.