In 1915, as part of his General Theory of Relativity, physicist Albert Einstein predicted that gravity would behave as a warping of spacetime, and predicted that gravitational waves — "ripples" — would emerge in the interaction of extremely massive objects in space.
Einstein explicitly stated that we would never be able to measure this behavior, but he underestimated advancements in measurement technology.
On February 11th, 2016, researchers from LIGO (the Laser Interferometer Gravity-Wave Observatory, which the California Institute of Technology was key to organizing) announced the observations of these waves — predicted one hundred years previously in that seminal paper by Albert Einstein — when two black holes were observed colliding.
These six covers by Joshua McGee, cancelled at the post office most convenient to Caltech on the day of the announcement, commemorate this historic discovery and achievement. They feature a screen capture of LIGO's animation of the collision of the two black holes, with the LIGO logo masked against a computer visualization of gravitational waves, and the text "LIGO Announces Discovery of