The LIGO direct-detection of gravitational waves arriving from cosmic sources—now, happily including (as of this meeting!) the merging of two neutron stars—opens a new chapter in our understanding of physics itself: for General Relativity, conceptually so extremely simple, has robustly produced predictions that have invariably been found to be correct when tested. My poster (page 3 of this paper) is intended for high school students who have just learned simple algebra. My derivation of the famous E = mc2 from the Pythagorean Theorem necessarily requires an algebraic expansion that is due to Newton, but apart from that it is simplicity itself: a transparent introduction to what all of physics is today: the construction of mathematics that, miraculously, reproduces our observations of the world—and which also successfully predicts the results of future observations—as so magnificently demonstrated at this glorious Symposium!