Between 10 and 20 billion years ago, a sudden and intense explosion gave birth to the universe as we know it, an event famously known as the big bang. In 2007 the Center for European Nuclear Research (CERN) in Switzerland will attempt to simulate the big bang by smashing particles together at high speed in an effort called the Atlas experiment.
In collaboration with more than 150 research institutes around the world, including seven in Canada, U of T has installed a network composed of 448 processors for the experiment, capable of holding 28 trillion bytes of information, the equivalent of about 35,000 CDs. This network will process data generated by the Atlas experiment.
“In a way the Atlas experiment is almost like a big computer,” explains Professor Robert Orr of U of T’s Department of Physics, the principal Canadian investigator for Atlas. “There’s many many millions of events that occur in the space of minutes [when particles collide] so first of all we have to decide which are good events and which are bad [uninteresting] events.”
In order to test theories of what happened moments after the big bang, one needs to actually create the particles that existed then. “The problem is that the energy density just after the big bang was so great that many of the particles that were interacting then don’t exist nowadays,” says Orr. This makes it necessary to use the highest-energy particle accelerators possible. When the particles collide, their energy can spontaneously create new, short-lived, high-mass particles.
One major focus of the experiment will be to produce the long sought Higgs boson, which acts like a messenger, carrying forces between regular matter particles. “The inflation of the universe [during the big bang] was driven almost certainly by some particle like the Higgs…we need to know what the mass of the Higgs is if we want to calculate what happened very early in the big bang,” says Orr.
The field of Higgs bosons is thought to be what gives particles the mass that they have. In this completely new way of viewing the concept of mass, the universe is permeated everywhere by Higgs boson particles. When a particle, such as an electron, moves about, its interaction with this Higgs field gives rise to what we call mass. The Atlas experiment may confirm this speculation by finally producing the Higgs particle.
There are thought to be four simple forces that govern the movement of matter in the universe: electromagnetism, gravity, strong nuclear force, and weak nuclear force. The holy grail that physicists are searching for is a Theory of Everything, which would unite the four forces of nature, as they were during the early moments of the universe. “We think just after the universe came into existence, all these forces were [combined as] some primordial force; but as the universe cooled down these [separate] forces appeared,” explains Orr.
By inducing collisions of high enough energy, the conditions of the early universe can be recreated up to the point where some of the forces re-unite, generating a whole new class of particles. These particles would not interact with light, but only with gravity, which would account for the missing dark matter. Physicists have been looking for what they call “dark matter,” which may account for 25 per cent of the matter in the universe. It cannot be seen, but its gravitational effects can been measured. Scientists have measured more gravity in the universe than can be accounted for by visible matter alone.
As scientists probe back to the beginning of time itself, it is hoped the Atlas experiment will confirm what is suspected and help solve some of the most fundamental questions of physics.
