Black Holes, Tides, and Curved Spacetime: Understanding Gravity

Exploring gravity with Isaac Newton and the famous story of the apple; a breakthrough to connect a falling apple with the faraway moon; the essential characteristics of gravity; why small asteroids and large planets have such different shapes.

Three discoveries by the grandfather of gravity research, Galileo Galilei; his principle of inertia, law of free fall and principle of relativity are the basis for everything that comes later in the science of gravity; key breakthroughs by Einstein.

Drawing on the ideas of Nicolaus Copernicus and Tycho Brahe, Johannes Kepler achieves insight into gravity; three laws of planetary motion, relating to the mathematics of orbits; he states that the cause of planetary motion must lie in the sun.

Newton finishes Kepler's revolution by formulating the law of universal gravitation; it says that every object exerts an attractive force on every other object; Newton's related discovery of the three laws of motion underlie the science of mechanics.

How distances in the solar system are first determined; Henry Cavendish's experiment that finds the value of Newton's gravitational constant; Cavendish's work allows almost everything to be weighed; a confirmation of the equivalence principle.

Digging deeper into Newton's laws than Newton himself can go; applying the key concepts of energy and angular momentum to study how gravity affects motion; as an example, using simple algebra to calculate the escape velocity from Earth.