If you could take an apple and break it into smaller and smaller parts, you would find molecules, then atoms, followed by subatomic particles like protons and the quarks and gluons that make them up.

At a 1990 conference on cosmology, I asked attendees, who included folks like Stephen Hawking, Michael Turner, James Peebles, Alan Guth and Andrei Linde, to nominate the smartest living physicist.

The apparent inability of physics' string theory to be proved right or wrong is one of the stickiest – and argument-generating – problems in modern science. But now researchers at the University of ...