In the famous twin paradox, one twin travels a great distance at the speed of light and returns, much younger than the other twin. Who is moving, and who isn’t? In this 13-minute video, Don Lincoln explains the perplexing puzzle.

Einstein’s special theory of relativity is notorious for being easy to misuse, with the result that sometimes result in claims of paradoxes. In this 11-minute video, Don Lincoln describes the commonly claimed time dilation paradox and shows how to resolve it.

Welcome to the first in a series by Don Lincoln on relativity. In this 12-minute video, he lays out what relativity is all about — not slow-moving clocks and shrinking objects, but instead on … well, watch and see.

Why E=mc2 is wrong

The most famous equation in all of science is Einstein’s E = mc2, but it is also frequently misunderstood and misused. In this video, Don Lincoln explains the truth about this equation and how people often use it incorrectly.

Central to all of the equations of relativity is the Lorentz factor, also known as gamma. In this 8-minute video, Don Lincoln shows you a simple way to derive gamma and explains its physical significance.

One of the most counterintuitive facts of our universe is that you can’t go faster than the speed of light. Why is this so? Don Lincoln explains in this 8-minute video.

One of the oddest features of special relativity is the inability to go faster than the speed of light. The most common explanation is that the mass of an object increases with speed, but this particular explanation simply isn’t true. Fermilab scientist Don Lincoln explains the truth behind this.