The Nobel Prize in Physics has been awarded to John Mather and George Smoot, for their discovery using the COBE satellite of temperature anisotropies in the cosmic microwave background. (Update: To be more accurate, Mather won the prize for measuring the blackbody spectrum of photons, announced in 1990; Smoot won it for measuring the anisotropies, announced in 1992. Thanks to Ned Wright for pointing out my sloppiness.) These tiny fluctuations in temperature provide a high-precision snapshot of what the universe was like 380,000 years after the Big Bang. They originate in density fluctuations that grow into large-scale structure today, and subsequent careful examination of the properties has revealed a tremendous amount about our universe. It’s a very well-deserved Nobel, which was top on my list of potential cosmology prizes back in May:
The 1992 observation of CMB anisotropies by NASA’s COBE satellite was the first step in a revolution in how cosmology is done, one that has come to dominate a lot of current research. Subsequent measurements by other experiments have obviously led to great improvements in precision, and most importantly extended our understanding of the anisotropies to smaller length scales, but I think the initial finding deserves the Nobel. So to whom should the prize be awarded? On purely scientific grounds, it seems to me that there was an obvious three-way prize that should have been given a while ago, to David Wilkinson, John Mather, and George Smoot. Wilkinson was the grandfather of the project, and was the leading CMB experimentalist for decades. Mather was the Project Manager for the satellite itself (as well as the Principal Investigator for the FIRAS instrument that measured the blackbody spectrum), while Smoot was the PI for the DMR instrument that actually measured the anisotropies. Unfortunately, Wilkinson passed away in 2002. Another complicating factor is that there were various intra-collaboration squabbles, leading to books by both Smoot and Mather that weren’t always completely complimentary toward each other. Still, background noise like that shouldn’t get in the way of great science, and these guys definitely deserve the Nobel.
When the results were announced in 1992, I was a fourth-year graduate student at the Center for Astrophysics at Harvard. Somehow, despite great attempts at secrecy, Bill Press had received a leak about the upcoming announcement, and had told some of us at CfA. The next day I went to the Physics colloquium and was the first to spread the news to some of the famous physicists chatting in the tea room, like Sidney Coleman and Roman Jackiw. My first feeling of being a cosmology insider.
It was a funny discovery, in the sense that most everyone expected that it would come (COBE was designed to do exactly this), and nevertheless ended up revolutionizing the field. The simplest measure of this was the arrival of an entire generation of smart young theoretical cosmologists who got their Ph.D.’s in the 1990’s working on the implications of the CMB anisotropies. Whenever we learn alot about the universe, of course, we also start ruling out interesting ideas; these days, nobody proposing a new cosmological scenario will be taken seriously unless their model is compatible with the microwave background.
Congratulations to John and George for ushering in the Golden Age of Cosmology!