15. Lesson 15: Special Relativity, 1

Confusion about light.

  What’s Coming:

Arguably one of the most important experiments in the last two centuries, and certainly the most important measurement ever of zero, starts in the Wild West of gold and silver mining – literally, the Wild West – and passes through Stockholm and the Nobel Prize. Let’s talk about one of the more interesting physicists of all. Albert Michelson.

I’ve mentioned the “ether” before. Sound waves travel in air. Water waves travel in water. Material waves travel in…well, the material. What do light waves travel “in”? Everyone from Faraday to just before Einstein agreed: they travel in the “luminferous ether,” or “ether” for short. Some strange substance that allows us to see through outer space and in our regular lives. How fast does the Earth travel through the ether? A technique was suggested by Maxwell, and the subject this chapter set out to measure it.

That led to recognition that there was a problem: the electromagnetism of Maxwell made no sense if you asked what people would see if one observer was stationary and the other moving. The lid blew off in 1905, but let’s work our way up to a slow-motion nervous breakdown in physics in the late 19th century.

  Goals of this lesson:

Understanding, Appreciation, and Familiarity

I’d like you to Understand:

• What “reference frames” are and how they function in mechanics

• What a “Galilean Transformation” is

• What the most famous measurement of zero worked: Michelson’s interferometer

I’d like you to Appreciate:

• How Maxwell’s electromagnetism led to specific contradictions. I’ll show you two.

• How to reconcile motion between two observers’ “reference frames”

I’d like you to become Familiar With:

• The history of Lorentz’ contributions

• Just how odd the accepted notion of the ether really was.