some basic background covering how mathematical models of space and time
have evolved since ancient times, from the Pythagorean Rule to Newtonian
mechanics, Special Relativity and General Relativity.
What is spacetime?
Why was Einstein's Special Theory of Relativity needed?
How does Einstein's Special Theory of Relativity work?
What is "causality" and what does it have to do with time travel?
What is gravity?
What is Einstein's General Theory of Relativity?
Observations of spacetime bending light
Go back to Time Travel in Flatland.