Friday, November 6, 2009
(John Marshall Memorial Lecture)
(view the slides usedˆàonˆàthe lecture)
Dr. Alan H. Guth, Victor F. Weisskopf professorˆàof physics at MIT, will deliver the AAA’s annual John Marshall Memorial Lecture on Friday, November 6, whenˆàhe discusses “Inflationary Cosmology: Is Our Universe Part of a Multiverse?” The free public lectureˆàbegins at 6:15 p.m. at the Kaufmann Theater of the AMNH.
Guth is one of the most eminent authorities on cosmology. Most of his research has centered on the application of theoretical particle physics to the early universe: What can particle physics tell us about the history of the universe, and what cosmology tell us about the fundamental laws of nature?
In 1981, Guth proposed that many features of our universe, including how it came to be so uniform and why it began so close to the critical density, can be explained by a new cosmological model, inflation. Inflation is a modification of the conventional Big Bang theory, proposing that the expansion of the universe was propelled by a repulsive gravitational force generated by an exotic form of matter. Although Guth’s initial proposal was flawed, as he pointed out in his original paper, the flaw was soon overcome by the invention of “new inflation” by others. After more than 20 years of development and scrutiny, evidence for the inflationary universe model now looks better than ever, he says.
One of the intriguing consequences of inflation is that quantum fluctuations in the early universe can be stretched to astronomical proportions, providing the seeds for the large-scale structure of the universe. The predicted spectrum of these fluctuations was calculated by Guth and others in 1982. These fluctuations can be seen today as ripples in the cosmic background radiation, but the amplitude of these faint ripples is only about one part in 100,000. Nonetheless, these ripples were detected by the COBE satellite in 1992, and they have now been measured to much higher precision by the WMAP and other experiments. The properties of the radiation are found to be in excellent agreement with the predictions of the simplest models of inflation.
Guth has explored whether it’s in principle possible to ignite inflation in a hypothetical laboratory, thereby creating a new universe. The answer is a definite maybe. It can’t be done classically, but with quantum tunneling it might be possible. The new universe, if created, wouldn’t endanger our universe. Instead it would slip through a wormhole and rapidly disconnect completely.
Another intriguing feature of inflation is that almost all versions of inflation are eternal; once inflation starts, it never stops completely. Inflation has ended in our part of the universe, but very far away one suspects that inflation is continuing, and will continue forever. Guth belives the inflating region of space-time must have a past boundary, and that some new physics, perhaps a quantum theory of creation, would be needed to understand it.
Much of Guth’s current work also concerns the study of density fluctuations arising from inflation.
Guth, who holds a Ph.D. in physics from MIT, has been on its faculty since 1980.
The AAA’s annual John Marshall Lecture commemorates Marshall, who served the club as president and executive director. He’s considered a key figure in the association’s growth.ˆàMarshall died in 1997.