Light is a small part of the electromagnetic spectrum and radiation given off by stars like the sun. Animals can also see light. Light exists in tiny packets called photons. It shows properties of both waves and particles. The study of light, known as optics, is an important research area in modern physics.

In this video named “How Fast Is It” Mr. David Butler talks about the speed of light. He starts with the slow moving snail and work up through people, animals, birds, cars, aircraft and spaceships.

Along the way we graph speeds on a space-time diagram. Following the history of land speed records, he covers the speed of sound and include its nature as a longitudinal wave and its speed in dry air.

The lecturer then discusses the Galilean transformations for converting speeds from one reference frame to another. He increases the velocities to the point where we see light traveling at different speeds as far as the Galilean transformations are concerned. He then shows how Galileo tried and failed to measure the speed of light.

Then Butler shows how Antonio Louis Fizeau did measure the speed of light. He then covers wave interference and the Michelson Interferometer. And using the interferometer, he informs about the Michelson-Morley experiment that showed that the speed of light was a constant.