In honor of Albert Einstein’s birthday on March 14, we’re re-publishing this podcast primer on his theories of General and Special Relativity—ideas that most people have heard of but few truly understand. Astrophysicist and educator Jeffrey Bennett breaks down the basic tenets of Einstein’s theories and underscores their importance to our modern understanding of the universe. This Frontiers Lecture took place on September 21, 2015. Subscribe to the Science@AMNH podcast on iTunes, Soundcloud, or wherever you get your podcasts. Support for Hayden Planetarium Programs is provided by the Schaffner Family and the Horace W. Goldsmith Endowment Fund.