In 1985 Freeman Dyson delivered the Gifford Lectures in Aberdeen, Scotland. The lectures were later turned into a book titled “Infinite in All Directions”. The title reflected both a quote from the physicist Emil Wiechert who marveled at the sheer reach of physics in the cosmos as well as Dyson’s own remarkably versatile interests. The lectures covered topics from nuclear winter to the origin of life, from string theory to immortality. They celebrated diversity as the quintessential virtue of humanity and the cosmos.

Thus it was only fitting that the group of scientists and policy makers chosen to speak on Dyson’s 90th birthday themselves covered vastly diverse and fertile ground. The sessions started with three lectures on pure mathematics, notably number theory. They dealt with work inspired by some of Dyson’s early papers on partitions, modular forms and continued fractions. Much of this work was incomprehensible to me but it indicated one characteristic of a genuinely brilliant thinker; even minor work that he may have done inspires months or years-long projects by other scientists.

The session on pure mathematics segued into one on physics and chemistry. Featured was Dyson’s work on the stability of matter and, in a brief introduction by distinguished mathematical physicist Edward Witten, his famed unification of quantum electrodynamics. Perhaps the most interesting talk in this session was by Russell Hemley of the Carnegie Institution. The focus of Hemley’s research is on reactions under pressure, and more generally on physics and chemistry under extreme conditions; John Timmer has a nice summary of the presentation here. Materials with “normal” properties under normal conditions can display a range of wondrous properties under pressure. For example hydrogen, which is a non-conducting gas at room temperature and pressure, becomes conducting and metallic under immense pressures. Metallic hydrogen is thought to exist in the interiors of Jupiter and Saturn and may well be part of the geological makeup of an as yet undiscovered exoplanet. The research that Hemley and others are doing on Earth may well apply in outer space. Hemley’s work provides an excellent illustration of how focusing on a narrow, seemingly mundane, earthly problem can have cosmic implications.

Hemley also talked about observing E. coli bacteria under pressure. The pressure leads to selective evolutionary pressure, causing mutations that enhance the bacteria’s survival. If we were to sequence the genes and proteins responsible for those mutations we would likely understand the factors that allow biomolecules to remain stable under such extreme conditions.

Hemley also talked about a controversial theory, namely the theory proposed by Thomas Gold that hydrocarbons are not produced by the dead bodies of living organisms but instead arise through abiogenic processes. In 2004 Hemley and his colleagues demonstrated strong support for this hypothesis by subjecting calcium carbonate, water and iron oxide to extreme pressure and temperature in a diamond anvil cell. The whole experiment took an afternoon, but the resulting paper published in Proceedings of the National Academy of Sciences not only went a long way toward validating Gold’s theory but also showcased two of Dyson’s favorite themes, the joy of being a heretic and the revolutionary impact of new tools rather than ideas, in this case the diamond anvil cell.

Another heretic in that session was Joseph Kirschvink of Caltech who talked about his work demonstrating that life probably arose first on Mars and was then transported on earth. “We are all Martians”, quipped Kirschvink more than once. Kirschvink is also the scientist who found crystals of magnetic ferrite in our brains. I found three pieces of evidence for our Martian origins to be the most compelling. Firstly, there is good evidence in the way that iron crystals in Martian meteorites are aligned to indicate that Mars once had a strong magnetic field that must have held on to oxygen (oxygen is what we call paramagnetic, sporting an unpaired electron and being attracted by a magnetic field). Secondly, these iron crystals lose their orientation above 40 degrees Celsius, indicating that the core temperature of Martian rocks never rose above that value during their journey to earth, a value that’s quite adequate to support life. Thirdly, Martian soil contains copious quantities of borate minerals, and work by chemist Steven Benner has recently shown that borate can catalyze the formation of ribose, a sugar that we know is essential for the formation of DNA and RNA. Taken together, this and other evidence makes as good a case for life arising on Mars as I have seen.

Speaking of heretics, albeit the more questionable kinds, the next talk was by noted climate ‘skeptic’ William Happer from Princeton University. I have previously talked about Happer’s flawed take on CO2 and I have also explored the differences between ‘skeptics’ and ‘deniers’. I am afraid that to me Happer seemed to handily cross over the boundary into denier territory. What was strange about the talk was that it was divided into two sections. One was the actual talk itself which focused on some pretty technical features of the CO2 absorption spectrum and Happer’s doubts about the ability of CO2 to capture enough heat. There was also some criticism of climate models. If this was all there was to it things would have been fine. As it turned out Happer seemed to take out all the stops when time came for the Q&A sessions. Among the howlers he perpetuated were the following: there is little evidence that CO2 drives temperature, there is little evidence that fossil fuels lead to health problems, there is little evidence that the planet cannot thrive in higher CO2 levels (I was tempted to ask him; sure, the planet can thrive, but what about humans?), there is no evidence of ocean acidification. Happer seemed to discount even the most basic facts of climate change, and the crowd did not know how to respond except with a couple of boos and disbelieving laughter.

An amusing exchange took place at the end of the talk when Edward Witten pointed out a recent article by Richard Muller of Berkeley in the NYT titled "A Pause, not an End, to Warming" in which Muller rationalized the pause in global warming as a temporary slowdown, and one which he had predicted using very simple models. These simple models did not have the limitations of the complex models that Happer discussed. To everyone’s amazement, Happer’s only response when Witten questioned him about Muller’s work was, “It’s junk”. That's it, no further explanation necessary. Nonplussed, all Witten could do was repeat the question. Witten closed the session right after Happer’s comment that fossil fuels do not cause health problems, signaling the end of an almost surreal experience. Let me recapitulate the difference between skeptics and deniers that I pointed out in that post; Dyson is a reasoned and healthy skeptic whose criticism exemplifies the best traditions of science, Happer is a denier. What do I make of people like him? I have decided that every field of science and public policy needs a critical mass of people who challenge the status quo. Some of these people are reasonable, others are not. But all of them at the very least get the conversation started and force everyone else to look at the other side of the argument. The problem starts when these challengers of the status quo grow to such large numbers that reasoned dialogue becomes impossible.

The second day of the symposium was devoted to astronomy and public policy. Dyson started working in astronomy quite late but made some important contributions. Perhaps his most publicly well-known contribution is his speculation on communicating with extraterrestrials using infrared radiation from what came to be called “Dyson spheres”. There were other ideas too, including work on adaptive optics that was initially done as a part of the JASON panel of government advisors. Dyson is also popular as a “futurist”, although he himself dislikes the term, and has often written about human expansion into space. He has proposed all kinds of outlandish sounding but scientifically plausible ideas, like looking for frozen fish in the orbit of Jupiter and growing plants on comets that can grow their own greenhouses. Dyson is a perfect example of someone whose scientific speculations make every effort to be as rigorous as his published scientific work. A highlight of the astronomy session was a talk by Sara Seager of MIT. Seager is an expert on exoplanet atmospheres and talked about the exciting missions planned in the next few decades for looking at the existence and composition of the atmospheres of earth-like exoplanets. This is undoubtedly one of the most exciting areas of science. It certainly tracks with Dyson's interests, and this year Thomson Reuters has nominated Geoffrey Marcy – the grandfather of exoplanetary astronomy – for the Nobel Prize.

The last part of Dysonfest dealt with public policy. The session was kicked off by the grand old man of arms control, Sidney Drell, who a few years ago created a stir when he published an impassioned plea for the abolition of nuclear weapons along with seasoned and influential policy veterans like George Schulz and Henry Kissinger. More than almost anyone else Drell knows about the safety issues and political instability inherent in a world with thousands of nuclear weapons. He has served with Dyson on JASON and has contributed to many aspects of the issue, from “small” nuclear weapons to ballistic missile defense. It was inspiring to watch this 93 year old with a cane talk about his concerns for a nuclear-free world in a strong and purposeful voice. I had a chance to talk to him alone for some time, and his words made it clear that it is up to young people to bring into fruition the work that he and his colleagues started. The last two talks were by William Press of The University of Texas and Amory Lovins of the Rocky Mountain Institute. Lovins’s talk about alternative energy was sensible but marred by an overly slick PowerPoint presentation whose dazzle - combined with Lovins's fondness for tossing out numbers with the regularity of a zealous accountant - obscured his main arguments.

Press talked about applying ideas from game theory to ethical and more efficient clinical trials in which one could decide when to withdraw or continue administering an experimental drug in a control group. He has become involved with Dyson in a novel and controversial interpretation of the Prisoner’s Dilemma. The foray into game theory exemplifies Dyson’s strength; the ability to apply elegant mathematics to fields in which he is far from being an expert. Few living thinkers can beat him at that game.

The end of Dysonfest felt like a walk through the entire universe of science and technology. From number theory to Martian life, from exoplanets to the stability of matter, from nuclear abolition to clinical trials, this was probably the most unusual scientific symposium that I have attended in terms of diversity. Overall it was a most enjoyable experience, and one more feather in the cap of an extraordinary intellect and beloved individual. His accomplishments as a loving family man and grandfather were also on full display in the form of his entire family - six children and sixteen grandchildren - attending the event. I felt truly reenergized by his energy, spirit and enthusiasm. May Freeman live long and continue to praise and contribute to diversity in all its forms.