Cliff Will Birthday Symposium

Eric Poisson, University of Guelph poisson-at-physics.uoguelph.ca

Clifford Will is 60! announced the webpage dedicated to this Symposium, which was held in Saint Louis on Sunday, November 19th 2006, just a few days after Cliff's birthday (November 13th). The Symposium came at the end of the 16th Midwest Relativity Meeting, an always popular event during which all researchers, junior and senior, contribute talks of 15 minutes. It says something about Cliff's standing in the field that this was probably the best attended Midwest Meeting in history, with over 90 participants. The Midwest Meeting was organized by Wai-Mo Suen, Emanuele Berti, Jian Tao, Han Wang, and Hui-Min Zhang from the Department of Physics at Washington University in Saint Louis. The Symposium was organized by Wai-Mo Suen, Richard Price, Bernard Schutz, Ed Seidel, Sándor Kovács, and Alan Wiseman. The Symposium featured hour-long talks by invited speakers Bernard Schutz, Luc Blanchet, Joseph Taylor, Francis Everitt, and Kip Thorne. There was plenty of time between talks for coffee, discussion, and poking fun at Cliff.

The first talk of the morning was by Bernard Schutz, who gave what he called the ``history talk,'' an overview of Cliff's career. The talk was titled Will and Testament, and it covered Cliff's undergraduate-student days at McMaster University in Hamilton, Canada, his graduate-student days at Caltech (working with Kip, of whom Cliff had never heard before arriving at Caltech -- he only sought him out on the advice of fellow Canadian graduate students), his postdoc-days at the University of Chicago (working with Chandra), his assistant-professor days at Stanford University (where he didn't get tenure -- see below), and his distinguished career at Washington University in Saint Louis, where Cliff is now James S. McDonnell Professor of Physics. At the end of Bernie's talk, a member of the audience asked whether Cliff had ever been known to be wrong on a serious issue. Bernie answered that to his knowledge, this had never happened. At this moment Leslie, Cliff's wife, raised an eager hand and offered to present many examples of Cliff being in error. The offer was declined, but Cliff explained: ``My students are frequently discouraged by the fact that, when we are in the middle of some complicated post-Newtonian calculations and have a disagreement over the coefficient of some term, I am almost always right. So I tell them not to worry: at home, I've been right 67 times, while my wife has been right 2,782,193 times.''

The second talk of the morning was given by Luc Blanchet, who reviewed The Wonders of the Post-Newtonian. This was a fascinating talk during which Luc described the enormous progress that has been accomplished in the last 15 years in the post-Newtonian theory of two-body motion and gravitational-wave generation. This effort has been pursued by a number of people around the world, with Cliff and his collaborators playing an essential role. Among the results obtained by these theorists is this impressive formula that gives the rate at which a two-body system in circular motion loses energy to gravitational radiation:

$$\begin{eqnarray*} \frac{dE}{dt} &=& \frac{32c^5}{5G}\nu^2 x^5 \biggl\{ 1 + \lef... ...ht)\pi x^{7/2} + {\cal O}\left(\frac{1}{c^8}\right) \biggr\}. \end{eqnarray*}$$

Here $x = (GM\omega/c^3)^{2/3}$ is a parameter (defined in terms of the orbital frequency $\omega$ and the system's total mass $M = m_1 + m_2$) that loosely represents $(v/c)^2$, the squared ratio of orbital velocity to the speed of light, $\nu = m_1 m_2/M^2$ is a dimensionless mass ratio, and $C \simeq 0.577$ is Euler's constant. The hope is that the observational consequences of this energy loss, which are manifested in the phasing of the gravitational wave, will be verified by gravitational-wave detectors. This will constitute a powerful test of general relativity, and as Luc pointed out, an alternative way of measuring the mathematical constants $\pi$ and $C$.

The third and final talk of the morning was given by Nobel laureate Joseph Taylor. In his talk, titled Using and Testing Relativity With Pulsars, Joe reviewed the exciting history of binary pulsars, which started in 1974 with his discovery (with then graduate student Russell Hulse) of PSR 1916+13, and which has taken a recent spectacular turn with the December 2003 discovery of the double pulsar PSR J0737-3039. The handful of relativistic binary pulsars that have been discovered to date have allowed sensitive tests of general relativity to be performed, tests that probe strong-field and radiative aspects of the theory. Nature could not have been more kind to relativists! During his talk, Joe displayed the abstract page of the first grant proposal in which he described plans for a systematic search for radio pulsars; on this page appears a throw-away comment to the effect that it would be a wonderful discovery if a pulsar could be found within a binary system...Joe also recalled the stimulating discussions he had at Stanford, with Cliff and Bob Wagoner, on the theoretical implications of his recent discovery.

The Symposium then broke for a group picture and lunch. (I went with Cliff, Larry Kidder, and Patrick Brady to a nice place on Delmar Boulevard. I had the chicken.) It resumed in the afternoon with a talk by Francis Everitt, titled Space, Gravity Probe B, and Clifford Will, in which he reviewed the long history of GPB, as well as the exciting developments that followed its launch in April, 2004. The scientific goal of Gravity Probe B is to measure, for the first time, the precession of test gyroscopes that is produced by the gravity associated with Earth's rotational motion, thereby testing the important relativistic prediction of frame dragging. Francis described the effort that is now underway to analyze the terabyte of experimental data that has been received from the probe to date. He did not report results; for this we will have to wait until the April 2007 meeting of the American Physical Society. Francis also explained Cliff's involvement in the project, mostly in his role as Chair of the NASA Science Advisory Committee for Gravity Probe B.

The second talk of the afternoon was given by Kip Thorne. In Will and Waves, Kip went a little deeper into historical matters and recounted Cliff's scientific activities as a graduate student. After Cliff spent some time talking with various researchers at Caltech and JPL, he and Kip concluded that the time had arrived (this was 1970) for a new generation of quantitative tests of general relativity. Cliff started to think about a theoretical framework that would facilitate the interpretation of the data, and would allow many alternative theories to be contained within a unified package. In a rapid burst of intense activity, he generalized the parameterized post-Newtonian (PPN) framework that was introduced a few years earlier by Ken Nordtvedt (building on earlier work by Eddington, Robertson, Schiff, and others), and he proceeded to explore its consequences. Cliff's version of the framework included a larger set of free parameters, and it was based on a hydrodynamical description of the matter instead of Nordtvedt's point-mass description.

In a period that started on August 24, 1970 and ended on May 1, 1972, Cliff published 7 papers on this subject, a total of 105 pages in the Astrophysical Journal. (And Cliff got married to Leslie just two months before! During his talk, Kip asked Cliff to describe his honeymoon, but Cliff refused to comply.) In a first sequence of papers (Theoretical Frameworks for Testing Relativistic Gravity I, II, and III) he fleshed out the theoretical aspects of the PPN formalism. In a second sequence of papers (Relativistic Gravity in the Solar System I and II -- III was submitted when Cliff was a postdoc in Chicago) he compared its predictions with astronomical data and placed bounds on the free parameters. The mature form of the PPN framework, as it is now displayed in Chapter 39 of Misner, Thorne, and Wheeler, was presented in a third sequence of papers (Conservation Laws and Preferred Frames in Relativistic Gravity I and II) co-authored with Nordtvedt. Not bad for a mere graduate student!

Kip went on to describe the reasons why Cliff was not granted tenure at Stanford, a topic that was alluded to by a number of speakers at the Symposium. According to Kip, Stanford's standard for granting tenure was that a candidate had to be one of the top three people working in the field. Kip was asked to comment on Cliff's standing within his peer group. As defined by Stanford, the peer group included Roger Penrose, Stephen Hawking, and Kip Thorne himself...Cliff was not granted tenure, but Stanford's loss was WashU's gain.

The last word of the Symposium was left to the man himself: Clifford Will. During his Parting Shots, Cliff acknowledged the long list of people (colleagues, postdocs, students) with whom he has collaborated and interacted in the course of his career. He remarked that ``what is so great about a career in gravitational physics is the science and the people, rather than the money or the power. I've noticed over almost 40 years in the business that our field seems to have fewer than its share of arrogant, mean-spirited, power-mad individuals, compared with other fields of physics. I attribute this partly to the history of the field. For so long general relativity was thought to be an irrelevant subject, in the backwaters of physics and astronomy, so people who were full of themselves, or out for the glory, would not find it attractive. Now that gravitational physics has re-entered the mainstream of physics, and has even taken on some of the characteristics of `big science,' with things costing hundreds of millions, like Gravity Probe B and gravitational-wave observatories, I hope that this will not change, and that the field will continue to be populated by the kinds of wonderful colleagues and friends I have encountered over my career.'' Well said.

This concludes my description of the scientific component of the Symposium. The event, however, included also a personal component, in the form of a banquet for friends and family that took place on the Saturday evening. (I had the chicken.) Cliff was paid a moving tribute (in song) by the members of his family (daughters, sons-in-law, and grandchildren) and was gently roasted by a group of his Saint-Louis friends, who complained that he spends way too much time in Paris. He was also (more vigorously) roasted by Alan Wiseman, who described Cliff's tough-love approach toward the mentoring of graduate students. (On a draft of an early research article written by Alan, Cliff crossed out his own name, explaining that he did not want to be associated with that piece of shit. I think he was kidding.)

The banquet's keynote act was a performance by Clifford and the Silvertops, a group of illustrious singers (also known as Bernie and the Gravitones) consisting of Bernard Schutz (sporting a fake mustache, singing lead, and playing the role of Clifford), Richard Price, Sándor Kovács, and Kip Thorne (all with white-powdered hair). To the tune of Paul Anka's My Way, they sang

Where there's a Will there's a way

It's been a long time now
I've work'd with Einstein's theory
With work and more work, wow
No wonder why I am so weary

They asked was Einstein wrong
I told them no and I earned high pay
For math so very long
To do it his way [The singers point at a lifesize picture of Einstein.]

New jobs I've had to face
But as to change I now say fooey
I stay, stay in one place
I stay in France, I mean Saint Looey

Geepee bee, and geepee ess
Gee, whiz I guess that we can now say
Nature has passed the test
She did it his way

When I was young, Newton was all
But then came post, and that's not all
After the post, a host more post
Until I thought that I was toast
A billion terms, a can of worms
To do it his way

Up north people are few
We almost never [5 silent beats] spoke
But here to be a jew
They made me learn to tell a bad joke

I've friends, I think I do
And colleagues some who made my hair grey
So long, so long ago
Doing it his way

I ruled the field, and here's the thing
My work, my book, I was a king
I was the star where'er I'd roam
But time to time I would come home
Home to my life, home to my wife
To do it her way [The singers point at Leslie.]

The lyrics to this great song were written by Richard Price, and they are reproduced here with his kind permission. The bold words are emphasized (held longer) to keep beat with the music.

I'll close this report with a personal note. I have a vivid memory of the time when Cliff offered for me to come to Saint Louis and work with him as a postdoc. I was overjoyed! After my time at Caltech this was where I most wanted to be. It has been my great fortune and privilege to work with Cliff, and I am proud to count him as a friend. I am very glad to have been a participant at this Symposium, and I wish Cliff a very happy 60th birthday.

[I thank Richard Price for his permission to reproduce the song's lyrics, and Clifford Will for providing me with the italicized quotes. I thank them both for fact-checking an earlier draft of this report and providing suggestions for improvement.]