The next speaker in the Patten Lecture Series is Neta Bahcall, professor of astrophysics at Princeton University. Both lectures will be at 7:30 p.m. in Ballantine Hall, room 109. She’ll speak on
“The Dark Side of the Universe” on Tuesday, October 23, 2007
What is the universe made of? Recent observations suggest surprising new results. Not only most of the matter in the universe is dark and unconventional (non-baryonic) but, more surprisingly, the major component of the universe may be in the form of 'dark energy'—a form of energy that opposes the pull of gravity and causes the expansion of the universe to accelerate. By combining recent observations of clusters of galaxies, distant supernovae, and the cosmic microwave background radiation, we find evidence for an unexpected universe—one that has only 5% 'normal' matter, 20% dark matter, and 75% 'dark energy.' The observations indicate a universe that is lightweight, with sub-critical mass-density, and is dominated by a yet unknown 'dark-energy.' The observations and implications of the dark side of the universe will be discussed.
“Will the Universe Expand Forever?” on Thursday, October 25, 2007
What is the ultimate fate of the universe—will it expand forever or will it eventually collapse in a ‘Big Crunch’? The answer to this fundamental question depends on two critical observations: How much matter or gravity exists in the universe? And, does the universe contain other forms of energy that affect its expansion? Answers to these questions will reveal not only the fate of our universe but will also shed light on the evolution of the universe since the Big-Bang. Combining recent observations of different sources we find evidence that we live in a surprisingly lightweight universe, with mass-density well below the critical density needed to halt the universal expansion. Furthermore, the observations suggest that the expansion rate of the universe is not slowing down as expected if only matter exists in the universe; rather, the expansion appears to be speeding up! This suggests the existence of additional energy that opposes the attractive pull of gravity. The combined observations suggest a universe that will expand forever, growing ever larger, colder, and darker.
