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.

• Newton wrote equations that described the whole Universe.
• Newton's law of gravity explained Galileo's description of falling objects.
• Newton's law of gravity also explained the elliptical orbits described by Kepler.
• Kepler continued the revolution in the way we picture the Universe that had started with Copernicus.

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.