IMPLICATIONS OF EXTRA DIMENSIONS
Grand Unified Theories (GUTs) are the framework wherein three of nature's forces---the strong, the weak, and the hypercharge forces (the latter being a better way of describing the electromagnetic force at energies above several hundred GeV---come together as facets of one underlying force. Unfortunately, these theories fully come into play only at the very high energies (10^16 GeV) which prevailed in the very early (and hot) universe. This figure shows what can happen if extra spacetime dimensions exist. Such dimensions are a generic prediction of string theory. A new proposal by three CERN physicists points out that if the extra dimensions have a characteristic size on the order of 10^-19 m or less (corresponding to an energy scale of 1 TeV), then their effect would be to lower the GUT scale to the TeV-scale (10^3 GeV). This in turn would allow GUT physics to be observed directly in the next round of accelerator experiments. The figure shows the inverse strengths of the three forces with and without the extra large dimensions. With the extra dimensions, the forces become unified at an energy scale of roughly 20 TeV rather than 10^16 GeV. (Courtesy of CERN) This research is reported by theorists at CERN.