# Physics

fact: A force is a push or a pull between two objects.

When Buzz Aldrin joined Neil Armstrong on the moon in 1969, one of the first things he did was to try one-footed kangaroo hops. Why? To test out methods for moving around in lunar gravity (which is 1/6th that of Earths). Aldrin was experimenting with physics a discipline that involves the study of matter and forces and how they interact in space and time. The modules contained in our Physics Library explore the properties of light, electromagnetism, gravity, and more.

For centuries, controversy over whether light is made of particles or waves abounded. This module traces the controversy over time, from Isaac Newton's "corpuscle" (particle) theory, which prevailed for centuries, to Thomas Young's groundbreaking *double slit* experiment, which provided evidence that light traveled in waves.

The study of electricity and magnetism were artfully united in John Clerk Maxwell’s theory of electromagnetism. This module explores the experimental connection between electricity and magnetism, beginning with the work of Oersted, Ampere, and Faraday. The module gives an overview of the electromagnetic nature of light and its properties, as predicted by Maxwell’s mathematical model.

The concept of energy has fascinated scientists and philosophers for thousands of years. This module describes early ideas about energy and traces the development of our modern understanding of energy through the work of Joule and Faraday. Potential and kinetic energy are distinguished, and the six main forms of energy are described. The module highlights energy conversion and discusses how energy is measured.

Isaac Newton's description of gravity was not the first explanation of this phenomenon, nor was it the last. This module explores how Newton built on the work of early astronomers and how his theory was confirmed and built upon by others. Mathematical equations are presented for (1) the Law of Universal Gravitation, (2) the Gravitational Constant, (3) Earth's mass, and (4) the gravitational attraction between two people.