From Quantum to Cosmos-I

By Mark Trodden | May 22, 2006 10:32 am

I’m blogging from a meeting room at the Airlie Center in Warrenton, Virginia, where I am taking part in a NASA meeting titled From Quantum to Cosmos: Fundamental Physics Research in Space. The ostensible rationale for this meeting is “to demonstrate how fundamental physics research in space can provide the knowledge needed to address outstanding questions at the intersection of physics and astronomy”. However, it is also worth pointing out that this is also a closeout meeting for part of NASA’s fundamental research efforts, which have suffered extreme cuts due to the recent reorientation of NASA’s priorities.

I’m here to deliver a plenary talk on Cosmic Acceleration and Modified Gravity, which I gave during the inaugural session last evening. I’m also chairing an exciting set of plenary talks that occur tomorrow, with a lineup of Gia Dvali, Cedric Deffayet, Eric Adelberger and Ho Jung Paik. Sean is also here and will be delivering a related talk in one of today’s plenary sessions.

As I’ve tried to convey above, there are really two parallel threads running through this meeting, and I hope to post a couple more times with my thoughts on each of them separately. The primary, and most important thread is the physics. This is a meeting with an unusually eclectic and distinguished participant list (plus me). Yesterday evening’s session included fascinating presentations from Nobel laureates Bill Phillips and Doug Osheroff. This morning kicked off with a talk by Jack Marburger, director of the Office of Science and Technology Policy, and I’m currently listening to Nobel laureate Frank Wilczek’s talk. Later, we’ll hear from yet more Nobel laureates – Wolfgang Ketterle and John Hall. You should be impressed by this list, but I should also point out that there is a much longer list of truly tremendous scientists here, who just don’t happen to have Nobel prizes yet. There are probably even other Nobel laureates here, whose names I’ve just missed on the list.

The second thread is that of science and space policy. NASA’s recent budgetary woes are part of a larger crisis in fundamental science funding is the United States. As well as Jack Marburger, various participants from the National Science Foundation, the Department of Energy, and the European Space Agency are present, many of who will deliver talks and then take part in a round table discussion on Wednesday, to conclude the meeting. This promises to be a lively session, given the current climate, and I am interested to see the views of these people, most of whom seem genuinely interested in supporting science through this hard time.

So what scientific issues are all these minds here to discuss? Well, the idea is to explore, understand and frame future opportunities to do fundamental physics experiments in space. This means that, although there will be wonderful talks here about observational cosmology and astrophysics, the main focus is on what we might learn from laboratory experiments in space.

Since the conference just got underway last evening, I’ll need another day at least before I can provide a sensible account of some of the topics, or of the politics. But to whet your appetite, let me just comment on one thing that I learned from Bill Phillips’ talk yesterday. Phillips gave a tremendously energetic and wide-ranging presentation, describing an array of techniques and advances in the physics of cold atoms and their uses, in particular, for performing precision timing measurements. These include applications ranging from exquisite tests of the equivalence principle (by measuring the rates at which clocks constructed from different materials fall under gravity) to using precision detections of variations of gravitational potentials in Homeland Security applications (one could imagine using such techniques to scan large containers without ever opening them).

But it was something very simple that he said, that I felt like I should have known, that really impressed me. When I teach General Relativity, I love to describe gravitational redshift to students and see their reactions when they realize that clocks really do run at different rates at different places in a gravitational field. When I describe this, I usually comment on the tiny size of this effect on Earth, between sea level and high in the atmosphere, for example. What Phillips mentioned, which was new to me, is that the accuracy of atomic clocks has recently improved to the point at which it has become possible to measure the gravitational redshift on Earth over a vertical distance of one foot!

I found this truly astounding and expect I will learn about many other such results and ideas over the next three exhausting days (sessions from 8:30am to 9:00pm). I’ll write again describing more of them in a day or so.


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About Mark Trodden

Mark Trodden holds the Fay R. and Eugene L. Langberg Endowed Chair in Physics and is co-director of the Center for Particle Cosmology at the University of Pennsylvania. He is a theoretical physicist working on particle physics and gravity— in particular on the roles they play in the evolution and structure of the universe. When asked for a short phrase to describe his research area, he says he is a particle cosmologist.


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