19 December 2003
Vol 302, Issue 5653

About The Cover

Cover image expansion

COVER Disks represent an aging and expanding universe. Work this year confirmed a bizarre story of how the cosmos was born and what it is made of. Dark energy is the primary ingredient in a universe whose expansion rate and age are now known with unprecedented precision. See the Breakthrough of the Year special section and the accompanying Editorial. 2038. [Image: Cameron Slayden]