Looking for nothing to test gravity

When they look for violations of Einstein's general relativity, physicists deliberately plan experiments to find nothing at all. In 1887, physicists Albert Michelson and Edward Morley performed one of physics' most famous experiments (at Case Western Reserve University, coincidentally, across the street from where this article was written). Unlike other important experiments, they didn't find what they were looking for, but unexpectedly their "null" result prepared the way for the theory of rela...