Exploding Stars and the Accelerating Cosmos: A Blunder Undone
Robert Kirshner (Harvard)
Recent observations of exploding stars located halfway across the
Universe reveal an astonishing fact: the expansion of the Universe is
speeding up! This suggests that empty space itself is the
source of a mysterious "dark energy" that drives cosmic
acceleration. Curiously, when Albert Einstein first thought
about the role of gravity acting throughout the Universe in 1917, he
imagined a repulsive "cosmological constant" that would balance out
the attractive effects of gravitation. After the expansion of our
Universe was clearly established by astronomers, Einstein regarded
this cosmological term as a mistake. Modern observations show
that we need something that acts very much like Einstein's discarded
cosmological constant to account for an accelerating universe.
And we need a lot of it-- dark energy accounts for 70% of the universe
today. This talk will show how astronomers use
supernova explosions to trace cosmic history and will sketch some of
the plans to learn more about the nature of the dark energy through
observations.
