(via Minute Physics) This video is chapter 2 in my series on special relativity, and it covers spacetime diagrams, rotational and translational symmetry of both time and space, how certain ...

A particle moves back and forth along a line, increasing in speed. Graph. How many equivalence classes in Galilean spacetime are there for a particle that is at rest? A particle that is moving at a ...

What’s the difference between the past and the future? Not a great deal, if you take a purely relativistic view of the universe, say George Ellis from the University of Cape Town in South Africa and ...