Wednesday was a big day in the physics department at Penn, as we held the annual Henry Primakoff lecture. Primakoff was the first Donner Professor of Physics at Penn, and served on the faculty from 1960 onwards. He was best known for his eponymous effect, which, among other things, describes the production of neutral pseudoscalar mesons by the interaction of a photon with a virtual photon in the Coulomb field of a heavy nucleus. (Intrigued to know more about Primakoff, I came across this touching memoir by the late Peter Rosen, who had worked with him.)
Since T.D. Lee’s inaugural lecture in 1985, a string of outstanding physicists have delivered the Primakoff lecture. But I was extremely lucky that, in my first year here, the honor fell to a cosmologist – Jim Peebles. Jim was nice enough to give an astrophysics seminar yesterday afternoon (on “The Cosmology of Small-Scale Structure”), and then, after an hour break, to give his Primakoff lecture, titled “Finding the Big Bang”.
Popular-level lectures these days often focus on some of the more recent developments in the field, and the reasons they are so exciting. Certainly quite a few of my own public lectures take this approach. But Jim took a different tack, focusing instead on the sequence of events through which the big bang theory became accepted. He gave a wonderful historical account of the discovery of cosmic expansion, and a more personal description of the most important later discoveries; of the microwave background radiation (CMB) and the abundances of the light elements (Big Bang nucleosynthesis – BBN). Jim himself was around for a great deal of this important history (Indeed, it was Jim’s advisor, Bob Dicke, who set David Wilkinson looking for the CMB, only to be serendipitously scooped by Arno Penzias and Bob Wilson), and his take on how the various discoveries were made, and who played the important roles taught me quite a few details that I hadn’t realized. I don’t think I can do real justice to his account, but fortunately I don’t have to, since all will be described in an upcoming book, edited by Jim, with Bruce Partridge and Lyman Page, coming out at the end of next month. I’m sure we’ll write about it here.
That evening, I turned up for the dinner to celebrate the Primakoff lecture to find out that I was the second person to arrive, the first being Mildred Cohn Primakoff. Being new to Penn, I didn’t know that Mildred was around, and it was a wonderful surprise to meet her. Ms. Primakoff was born in 1913, and became a successful female scientist at a time when that was far less common than today, becoming the Benjamin Rush Professor of Physiological Chemistry at Penn, and receiving the National Medal of Science. They must have made quite a remarkable couple!
March 7th, 2009 at 10:40 pm
The title of the Astro seminar sounds interesting. Does your department make the speaker’s video/slides available?
March 8th, 2009 at 5:20 pm
Interesting quote from that memoir by Peter Rosen
“and the latter [G C Wick] showed that cosmic ray primaries should consist mainly of protons because energetic electrons would undergo too much scattering from photons in intergalactic space (through the inverse Compton effect) to reach the vicinity of the Earth.”
Sean recently mentioned here that physicists considered it unlikely that black holes would have a net charge. But if electrons are scattered more than protons, might there not be more protons reaching the hole and falling into the event horizon? (Unless there are equal numbers of antiprotons of course)