When we last left off, Brian Greene was telling us about the components of the universe, Atoms, made of Protons and Neutrons, which are made of Quarks, which are made of Strings. Setting aside the idea of strings for a moment, and without telling us why, we dive into Relativity, which is probably going to be critical to our understanding of things later on.
One critical component that must be understood is the nature of light. Light is "actually" an electromagnetic wave. It oscillates sinusoidally with an electrical component which is perpendicular to the magnetic component. It also propagates at light speed. And it does not slow down. This is not entirely true, as light in different media travels at different speeds, but what is very important to understand is that the speed in any medium does not attenuate, like a car when you take your foot off the gas. Light just keeps on rolling, rolling, rolling along.
Something that I have mentioned quite a bit in the podcast, probably akin to beating a dead horse, is that reference frames are so critical. You need your coordinate axis. You need to know what you are measuring WITH RESPECT TO. Greene illustrates very well why this is so necessary with a couple of classic relativity examples.
First we get the George and Gracie example. Imagine two astronauts hanging out in space. There is NOTHING else around for zillions of light years. George is hanging out and he sees a flashing light in the distance. This is Miss Gracie. She zooms past and as far as George is concerned he was sitting still and this madam was in motion. Now, if you consider it from Gracie's perspective, it's pretty much the same thing. Gracie is sitting still minding her own business and Mr. George zooms by.
The major takeaway here is that different reference frames will actually measure different events. This was a major change in the way that the universe was thought of.
