Episode 1: Explaining Gravity

Greek Theories

The ancient Greeks had unique theories about gravity, primarily proposed by Aristotle and later refined by Ptolemy. Aristotle believed that objects were made of four elements, each with a natural tendency to move in specific directions, and that planets moved in perfect circular orbits around the Earth. Ptolemy expanded on this by introducing the concept of epicycles to explain retrograde motion, maintaining the geocentric model for centuries 1.

Ptolemy adopted the idea that each planet orbited around the Earth on a perfect circle, but also on a smaller circle called epicycles.

--- James Fodor

This model remained dominant until the 16th century when Copernicus proposed a heliocentric system, which still relied on circular orbits but explained retrograde motion more simply 2.

   

Newton's Insights

Sir Isaac Newton revolutionized our understanding of gravity with his universal law of gravitation. He was the first to connect the force that causes an apple to fall with the force that keeps planets in orbit, formulating laws that could predict celestial movements accurately. Newton's laws were so precise that they could derive Kepler's laws and predict eclipses 3.

Newton connected the idea of apples falling from a tree with planets rotating around the sun.

--- James Fodor

He also explained that gravity is always attractive and diminishes by the square of the distance between objects, making it a unique force that governs planetary motion 4.