Discovering Gravity
People have always known that things fall. Our ideas of why have changed dramatically.
Galileo's discoveries about falling objects changed our perception of time.
 Galileo expressed his discoveries precisely with equations.
 These discoveries led to the development of accurate pendulum clocks.
 Galileo explained falling and rising with two forces: gravity, and buoyancy.
 This theory replaced the idea that objects move differently because they are made of different elements.
Newton described the dance of the planets, as well as falling objects.
Einstein's equations expanded the Universe.
 Einstein's equations joined space and time together.
 This theory of relativity reconciled Maxwell's equations of light with Newton's laws of motion.
 Joining space and time was half the job. To describe gravity, Einstein had to bend space and time.
 Black Holes and a Big Bang were strange features of Einstein's expanding Universe.


Replica of Galileo's clock
Copernican cosmology
Curved spacetime
