Saul Perlmutter shared the 2011 Nobel Prize in physics for his discovery that the universe was expanding at an accelerating rate. Perlmutter explains how supernovae and other astronomical artifacts are used to measure the expansion rate, and explains what physicists are learning about "dark energy" — the mysterious entity thought to be driving the acceleration.
Exploring An Ever-Expanding Universe
By editor • May 10, 2013
Originally published on May 10, 2013 1:23 pm