from Bernie Hobbs at ABC Science:
Antimatter isn't just a great plot device for sci-fi stories. It's at the heart of one of the great mysteries in modern physics-- why our universe has stuff in it.
Every particle that makes up matter-- the electron, proton, neutron and their more-obscure cousins-- has an almost-identical twin: its antiparticle.
They were both made together from cooling energy in really high-energy environments like the big bang.
Antiparticles are exactly the same as their particle "siblings", except they have the opposite charge.
So there's no way to tell particles and antiparticles apart, except for how they are affected by other charged particles.
An electron (negatively charged) will be attracted to a proton (positive), but an anti-electron (positive charge) will be repelled by it.
Anti-protons, anti-neutrons and anti-electrons can get together to form anti-atoms that act just like regular atoms. And anti-atoms can make anti-molecules that would behave just the same as regular molecules.
The only difference between them and a regular twin would be as soon as you shook anti-you's hand, you'd both be destroyed in a massive flash of light, as your matter and antimatter converted back to the energy that they formed from.
This same thing happens whenever matching matter and antimatter particles get together — they annihilate each other, converting back to the energy they came from.
Which brings us to a fundamental problem with our understanding of the universe: we shouldn't be here.
The entire post can be read here.