"HOW TO MAKE GRAVITY JOIN THE OTHER FORCES OF NATURE
AT A REASONABLE ENERGY: LOCALIZING GRAVITONS IN AN EXTRA DIMENSION"
Over three centuries after Newton proposed the universal
law of gravitation, we are still unable to answer a simple question: why
is gravity so weak compared to all the other forces in nature? In the last
two years, a new approach to this problem has been suggested, where gravity
is not taken to be intrinsically weak. Instead, gravity only appears weak
because it dilutes itself into a number of large extra dimensions, while
the other forces are confined to living on a three-dimensional membrane
floating in the higher-dimensional space. These extra dimensions could
be very large, perhaps as large as millimeter, without being in conflict
with any known experimental bounds. If this scenario is correct, the ultimate
unification of gravity with the other forces should manifest itself at
future accelerators, through processes such as the emission of gravitons
into the extra dimensions, the production of the strings of string theory,
and the creation of black holes. Also, in many versions of the theory,
deviations from Newton's law are predicted at sub-millimeter distances,
and can be detected with a new generation of table-top experiments.