Articles

Matter vs Antimatter : Asymmetry in the Universe

In Uncategorized on May 22, 2010 by Sukrit

The fact that I am sitting here writing this article, directly the fact that the Universe exists is due to a lucky chance. Let me explain what i mean here. Chance becoz the probability of this universe existing is about 1 in a billion billion or perhaps even lesser. Lucky because inspite of this miniscule prob. we are still here and we have no clue how. All of the known stuff in this Universe is made up of matter. But a large part of the mass of the universe is actually made up of Antimatter.  Antimatter is like the conjoined twin of matter- joined at the head but distinct elsewhere. A combination of matter with antimatter would result in a tremendous burst of energy. But what has all this got to do with our existence? The answer is- Everything.

In the early universe when most mass existed in the form of energy at high temperatures the densities of the matter and antimatter determined the structure of the Universe. In order for galaxies to form and take shape , the density of the matter should be slightly larger than that of antimatter. Too large and all galaxies would be crushed by their own gravitational attraction.If matter and antimatter had come out even in those first moments, they would have instantly destroyed each other, leaving nothing but energy behind. This slight asymmetry in the density of matter and antimatter has puzzled physicists as there is no reasonable justification for it. Current model of physics cannot account for this asymmetry.

The tevatron particle smasher in Illinois has provided a new clue to this Mystrey. Colliding protons and antiprotons at high energy would result in the formation of neutral mesons which would then be expected to decay and give same amounts of matter and antimatter. For some reason there are more negative muons which are matter than positive muons which are antimatter. The asymmetry observed is close to 1 percent. Particle physicists suspect that this is probably due to an unobserved high energy particle somewhat like the Higgs Boson. Only the LHC can tell.

It may surprise some to know that antimatter was not first detected by billions of dollars worth particle accelerators or telescopes. It was conjectured by a theoretical physicist called Paul Dirac. He was doing some work on Quantum Mechanics. To account for a lack of symmetry in his equations he said that antimatter should exist. These are its properties. Go and look for it. You will find it. He did this sitting in his office ! Imagine being able to talk about the Universe sitting in an office in Cambridge University. To someone like me this is the exiting part of theoretical physics.

I hope the LHC does not disappoint.

Sukrit

PS: I have been mesmerized these days about beauty and symmetry in Physics. I will write more about it soon.

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