Season 11 Episode 7

Martha and James voyage through space and time on this week's episode of the Oxford Online Maths Club, with an introduction to Albert Einstein's theory of Special Relativity.

Watch on YouTube

Further Reading

Relativity

I recommend David Tong’s notes on special relativity, part of a course on Dynamics and Relativity.

Martha recommended the book "Special Relativity and Classical Field Theory: the Theoretical Minimum" by Leonard Susskind and Art Friedman.

During the maths club episode, we mentioned the online game Velocity Raptor. You’re a dinosaur, and the speed of light is not very high, so when you move you experience time dilation and length contraction of the world around you. This makes the game (putting it lightly) rather difficult.

Maxwell’s equations for electromagnetism play a role in the development of relativity. You can read an overview of the history here.

Twin paradox

We didn’t quite talk about the twin paradox on the livestream, but we could have! This is the effect that someone moving experiences time at a different rate to someone who stays still. The thought experiment goes like this; one twin goes on an adventure near the speed of light, while the other twin stays at home. On their return, the one who was moving finds that time has passed faster on their home world, and the twin who stayed behind has aged more.

Remarkably, this thought experiment has actually taken place. There is a pair of astronaut twins (Scott and Mark Kelly), and one of them spent a year on the International Space Station (which is moving quite fast; nowhere near the speed of light, but still pretty fast). The theory is that the astronaut who went on the trip has aged 8.6 milliseconds less than his twin. As far as I know, this has not had an observable effect on him! Wikipedia has a photo. Maybe you can see in his eyes that he’s slightly less old than you’d expect...