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 Earth’s). 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.


The motion energy of an object does not depend on its size or the material it is made out of.

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.

    • Energy is defined as the capacity to perform work.
    • Energy comes in many forms, such as mechanical, chemical, heat, etc. and all are interchangeable to some extent.
    • James Joule was instrumental in establishing the concept of interchangeability of different forms of energy and quantitatively measured those changes in certain systems.

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.

    • Though the mechanisms of gravitational force are still a mystery, physicists have been able to effectively describe the influence of gravity on objects.
    • Newton’s mathematical model describing gravitational attraction paved the way for other scientists to build toward an understanding of the relationships between mass, acceleration, and the force of attraction.
    • Using the Law of Universal Gravitation, it is possible to predict the behavior of objects under the influence of gravitational force.
    • According to the Inverse Square Law, as the distance between two objects doubles, the force of gravity between those two objects decreases by a factor of four.

Without heat flow, nothing can move, no chemical reactions can take place, and no machines can run. This module introduces the concepts of heat and thermodynamics. It explains early ideas about heat and how scientists came to understand that heat and work are two different forms of the same thing. The First Law of Thermodynamics is described (simply put, energy cannot be created or destroyed). Other topics include latent heat and the measurement of heat.

    • Thermodynamics is the study of the relationships between heat, mechanical, chemical and other forms of energy and the effects of these forms of energy on or within a system.
    • Heat is a form of energy that moves from areas of high to low, and it can be converted into work energy.
    • The First Law of Thermodynamics, a variant of the Law of Conservation of Energy, states that within a closed system, energy may change form but cannot be created or destroyed.

This module introduces the history of wave theories, basic descriptions of waves and wave motion, and the concepts of wave speed and frequency.