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14 May 2009

Angels and Demons : Antimatter (Part I)

Today is the premiere of Dan Brown’s “Angels and Demons”. Ever wonder what exactly antimatter is? In the book, the description of antimatter is a little misleading.

Here, I want to discuss about antimatter.

In the book, the antimatter is used as the primary fuel in the bomb to destroy The Vatican. The fact is, with that amount mentioned in the book, the bomb is capable to do much more damage than it is in the story.

As a matter of fact, antimatter is one of the MOST efficient explosives in the universe. Converting all its mass to pure energy.

So, What IS antimatter?

Antimatter is quite simply, the “opposite” of ordinary matter. A mirror image of it, sort of speak. It’s like matter’s evil twin.

At the early 20th century, physicist knows about atoms. They know atoms are made of protons and electrons. Take Hydrogen for example, they know it is a proton that is the nucleus of the atom and an electron orbiting it.

But in the 1930’s, physicist realised for every particle, there’s an antiparticle for it. They discovered electrons evil twin – the antielectron (a.k.a Positron)

The discovery of positron. Bend the opposite direction as electrons in magnetic field. Sharper bend above the plate indicate that the particle has lose energy, means the particle come from the bottom of the plate.

What’s so special about the positron is, the positron has the SAME mass as the electron, but with the exact opposite charge. For example, electron is negative charged, the positron is well, positively charged.

Interactions between matter and antimatter.

Now, the interaction between ordinary matter and antimatter is crucial. It is explosive. What happens is, when you bring matter and antimatter in contact, they will undergo a very fast process called annihilation.

An example, if you bring in an electron, collide it with an antielectron, BOTH particles will disappear from the face of this universe and because both the conservation of energy and momentum must be obeyed, the resulting missing mass will generate packets of pure energy in a form of gamma rays that travel in perpendicular direction of the collision.

Feynman diagram shows an electron-positron pair annihilation event, turn into gamma ray photon and re-convert back to positron-electron pair.

Keep in mind that, in all atomic bomb detonations, only 1% of the fuel (uranium/plutonium) will be converted into energy.

Antimatter convert 100% of its mass to energy. So, it is vastly more powerful than the atomic bomb. (well, more accurately, >50% of the antimatter will be converted to usable energy. The rest are converted into neutrinos – tiny particles that are very hard to detect due to its inert nature.)

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