Antimatter, Einstein Modified!

"British physicist Paul A.M. Dirac revised Einstein's famous equation E=mc².

Dirac said that Einstein didn't consider that the "m" in the equation -- mass -- could have negative properties as well as positive. Dirac's equation (E = + or - mc²) allowed for the existence of anti-particles in our universe. Scientists have since proven that several anti-particles exist." : http://science.howstuffworks.com/antimatter1.htm

When matter and anitmatter collide there is an explosive reaction. This will be used to power space shuttles. The only proplem is , there isn't a lot of anti matter around, any that is dissapears when ever it meets matter.
Scientists believe that when the universe or galaxy was born there was significanly more matter then antimatter, there fore in the early stages of the universe, antimatter all but dissapear when it met matter in space.
It is believed the antimatter does exist in space, contained in magnetic clouds or nebulae?
The only wat to keep antimatter from matter is by using a magnetic field to contain it!