Prime mover

By Marcus Chown EARLY next century, we may be able to witness the single force that acted in the early Universe. A particle accelerator under construction at CERN, the European Laboratory for Particle Physics near Geneva, may have just enough energy to re-create the force, say physicists. In the earliest moments after the big bang, particles whizzed around with enormous energies. According to the so-called Grand Unified Theory, the three non-gravitational forces of nature—electromagnetic, weak and strong—acted as one at this time. But as the Universe cooled they split into the distinct forces we know today. Physicists believed the forces split when the particles’ energies dropped to about 1016 gigaelectronvolts (GeV)—100 trillion times higher than is achievable in today’s particle accelerators. This happened a mere 10-38 seconds after the Universe formed. But now physicists Keith Dienes, Emilian Dudas and Tony Gherghetta of CERN have calculated that the forces could have remained unified longer, down to energies of 1000 GeV. That energy is within the reach of the CERN’s Large Hadron Collider, due to be completed in 2005. The physicists came to this conclusion after making calculations about the extra dimensions that the Universe may contain. Theorists believe we do not see these extra dimensions because they are tightly “rolled up” to around 10-35 metres, a size that allows their effects to be felt only at the high energies that existed around the time of the big bang. If they were any bigger, there could be serious problems for the unified theory. It has been shown before that a host of new particles would rattle around in the extra dimensions, and bring with them more forces. “People thought the extra particles would make the forces too strong at the unification energy to be handled by current mathematical techniques,” says Dienes. But Dienes and his team have calculated that a larger fifth dimension of about 10-19 metres would not cause this problem. The calculations also suggest that although the three non-gravitational forces would strengthen quickly as the energy rises, they would also converge at a lower energy than expected, long before the mathematics becomes too difficult to handle. Dienes’s team has submitted papers on the work to Physics Letters B and Nuclear Physics B. The consequences of a much lower unification energy would be enormous. “All physics assumes unification occurs at an energy so high that it has no direct effect on the familiar world,” says Gherghetta. “If it occurs at a lower energy, it would change everything,
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