April 8, 2015
Whenever human understanding of the size of the universe is at a breakthrough point, a new idea about the nature of gravity introduces itself to the world. For thousands and thousands of years, the magnitude of the cosmos was limited to the stars that could be seen in the night sky (not that people knew what they were looking at). Just over 400 years ago, a tremendous breakthrough came. The telescope arrived, and drastically changed our view of the heavens. A mere 60 years later (a drop in the ocean of historical time), gravity was compared to the fall of an apple and Isaac Newton proposed that the moon traces out the curve of its orbit by constantly "falling" towards Earth.