In Once Before Time, Martin Bojowald explains how he developed the idea of loop quantum gravity and how it will soon be put to the test. At the moment of the big bang, our universe emerged from a state of infinite density, a point in space and time so small it had no size at all. This, the standard cosmological story tells us, is the singularity, the seed of creation. Singularities can also serve as seeds of destruction, lurking in the centres of black holes, the final endpoints of total gravitational collapse. Many physicists, however, believe singularities do not mark...