Sean Carroll | What is Relativity?

According to Einstein's special theory of relativity, there is no such thing as a moment in time spread throughout the universe. Instead, time is one of four dimensions in spacetime. Learn how this "relative" view of time is usefully diagramed with light cones, representing the past and future.

00:00 - Understanding Cosmology, Gravity, and Relativity

01:00 - Taking a Four-Dimensional Viewpoint of Relativity

02:15 - Moving Into a Space-Time View of Reality

03:40 - Differences Between a Newtonian and Einsteinian View of the Universe

04:45 - The Notion of Simultaneity

05:55 - Einstein’s Clocks, Poincaré’s Maps by Peter Galison

06:05 - Recurrence Theorem

08:00 - Einstein's Clock Patents

08:45 - Constructing the Present Moment

10:40 - Why Space-Time Is Relative

14:00 - What is a Muon?

15:00 - Carl Anderson Discovers Muons

15:50 - Why Do the Muons Reach Us Before Decaying?

18:30 - Einstein's Notion of Time as Personal

20:30 - What Are Light Cones?

24:20 - Time Dilation and Length Contraction

27:00 - How Einstein Conceptualizes Space-Time

28:00 - Newtonian Rule for Time Travel

28:45 - Implications of Relativity