Sunday, September 22, 2002

Antimatter on my father's knee

Albert Einstein, in 1905, set up the famous equation E=mc2, which states that mass is a very concentrated form of energy. Since then, much of speculative physics (and metallurgy) has been concerned with the attempt to explain what properties allow particles to bind more or less closely, which might allow us to break down particles in such a way as to produce greater volumes of energy. This, in turn, might allow scientists to use the density property to pin down that Holy Grail called "antimatter".

So what is this stuff called "antimatter", besides a potential oxymoron to the novice and a breatlessly-murmured seduction to those in-the-know? As my father tried to explain to me long, long ago, when my friends were enjoying bedtime stories about princes and goblins, antimatter is matter with its electrical charge reversed. Rather than dream about castles, I dreamt about anti-electrons, or "positrons," which resemble electrons except that they have a positive charge. The other characters of my childhood dreams? Antiprotons, which are like protons with a negative charge.

Positrons, antiprotons and other antiparticles can be routinely created at particle accelerator labs, such as CERN in Europe, and can even be trapped and stored for days or weeks at a time. Thanks to my father, any man who could talk to me about "particle accelerators" recieved the automatic benefit of a white-horse-and-shining-armour equivalent in my book of masculine valiance.

And now the nitty-gritty, the sexiest part of all-- antimatter is not antigravity. Although it has not been experimentally confirmed, existing theory predicts that antimatter behaves the same to gravity as does normal matter. Does this mean that when matter and antimatter combine, they should annihilate each other, given their different charges? And if antimatter is also subject to the force of gravity, why are we still breathing? Why does the universe persist? And what might prevent another Big Bang from occurring?

On a more practical note (i.e. the reason why such study still recieves government funding), scientists have been interested in the properties of antimatter in combination with fusion to find more efficient means of propelling spacecraft. For more practical uses of antimatter, as explored by the NASA laboratory in Huntsville, Alabama, an article from CNN does a fairly good job of explaining them (as does my father, though he might not appreciate the telephone call).

David Whitehouse noted in July of this year that the mystery of antimatter was being narrowed in an attempt to answer the question of why matter is the dominant form in this universe. New measurements at the Stanford Linear Accelerator Center (Slac) in California, US, refined measurements of sub-atomic particles that explain why there is a dominance of matter over antimatter in the Universe. matter and antimatter.

Assuming that the world began according to the Big Bang theory,at that point, equal quantities of matter and antimatter should have been created - which then subsequently annihilated each other leaving nothing behind but energy. Why, then, does the universe suggest the victory of matter over antimatter? In a quest for answers, physicists have looked at an effect called Charge Parity (CP) violation.Looking at CP violation involves studying particles, called B mesons and anti-B mesons, which have very short lives - a trillionth of a second. Any difference in the behaviour of these otherwise exactly opposite particles indicates a difference between matter and antimatter - and explains why one won out over the other. The degree of CP violation now confirmed is not enough on its own to explain the matter-antimatter imbalance in the Universe. Scientists have been seeking more to explain this difference.

In an article for The New York Times, Dennis Overbye reveals the latest discoveries in the field of antimatter studies, which are so beautiful I won't bother to paraphrase:

"Scientists see the creation of antihydrogen atoms as the first step toward testing some physicists' deepest notions about nature, which hold that antimatter should look and behave identically to ordinary matter. For example, any violation of the expected symmetry between hydrogen and antihydrogen, like a slight difference in the wavelengths of the light they emit, would rock physics to its core. The new research was conducted by physicists at CERN, the particle physics laboratory outside Geneva, solidifying CERN's dominance in antimatter research. By corraling clouds of antimatter particles in a cylindrical chamber laced with detectors and electric and magnetic fields, the physicists assembled antihydrogen atoms, the looking-glass equivalent of hydrogen, the most simple atom in nature. Whereas hydrogen consists of a positively charged proton circled by negatively charged electrons, in antihydrogen the proton's evil twin, a positively charged antiproton, is circled by an antielectron, otherwise known as a positron. They then observed the flashes of energy when the new antihydrogen atoms annihilated themselves in collisions with ordinary matter in the walls of the chamber."

"According to the standard theories of physics, anti-hydrogen and hydrogen atoms should have the same properties, emitting the exact same frequencies of light, for example. But some theorists have speculated that the symmetry between matter and antimatter might be violated in some versions of theories that seek to unite Einstein's theories on gravity with the weird rules of quantum mechanics. The most ambitious such "theory of everything," which portrays particles as strings wriggling in 10-dimensional space-time, seems to preserve the matter-antimatter symmetry, but theorists do not really understand why. "It's hard to imagine anything more interesting for string theory than an observation of a violation of the symmetry between matter and antimatter," said Andrew Strominger, a Harvard physicist."

Gentlemen, keep the wine and roses. If you really want to shake my world to its foundations, show me your antihydrogen. Or take me to your particle accelerator.