Universes

In set theory space can transformed while preserving distance by translation, rotation, and mirror images. Could our universe have a mirror image?

Why is our universe composed of particles instead of anti-particles? If it were composed of anti-particles we wouldn't know it and would call them particles and call the particles anti-particles.

Maybe after the big bang (or other beginning) there were two separate regions one of which had more particles which destroyed the anti-particles and the other one of which had more anti-particles which destroyed the particles. Call these regions universes.

Imagine the collision of a particle universe with an anti-particle universe. Wouldn't that create a very big bang?

E = mc^2

Calculations have been made based on E = mc^2 of the amount of energy in a drop of water. The trouble is that there is no known way to release that energy. Even in atomic bombs only a small portion of the energy is converted to energy because the atomic number remains the same, doesn't it? The only way I know of to annihilate a proton is with an antiproton and those are hard to come by.

Btw, I've always had trouble identifying the units of that equation which contains no k.