The discoveriesof general relativity and quantum mechanics began a revolution in physics. But the problem remains of completing the revolution with a theory of quantum gravity that joins those two pillars of modern physics. To have a chance to succeed, the new theory must not only make sense, it must make new predictions that can be tested by doable experiments. Physicists have made a great deal of progress in achieving the synthesis and have even proposed new experiments. That progress is the subject of this article.