I just received news that Freeman Dyson, one of the giants of twentieth century physics, has passed away at the age of 96. And while I do not usually cover such events here, some people are just too important to the history of science to be overlooked.

I am certain that there will be numerous articles on Dyson's research and career, most of which far more informative and written by individuals who knew him far better (and not written at three o'clock on a Saturday morning by a sleep deprived author).  However I feel that his work was so significant that it is important to note his passing here as well.

Perhaps the most significant work was his contribution to quantum field theory. Most people with even a passing interest in quantum field theory or particle physics are aware of Feynman diagrams. They are the stick figures that physicists use to keep track of interactions and reactions between subatomic particles, and are vital to all high energy physics research. What many people do not realize is that Feynman's work was not taken seriously when it was first published and presented. There is a famous story that at a physics conference attended by the titans of physics, a young physicist named Julian Schwinger spent several hours presenting a detailed calculation of the energy levels of the hydrogen atom, and filled numerous blackboards with his calculations. The audience cheered his work and applauded the effort. Then an equally young physicist name Richard Feynman spent a few minutes drawing stick figures, with no equations, and claimed to get the exact same result. No one took him seriously. 

So what does this story have to do with Freeman Dyson. He was another young physicist who worked with Feynman, and believed in Feynman's methods. And so Dyson spoke with Feynman at length and learned the details of these diagrams and how to use them to perform calculations of observable properties of particles and atoms. Then Dyson carefully read through all of the calculations that Schwinger had published, and learned every detail of Schwinger's methods of performing the exact same calculations. Less than a year after those two pioneers had published their respective methods, Dyson published an academic paper of his own demonstrating how the two methods were identical. He would go on to teach Feynman's methods to the rest of the physics community who were more familiar with equations than diagrams and hand waving. Without Dyson, the ubiquitous Feynman diagrams might have become a footnote in history and the far more complicated Schwinger equations would have become the standard. 

Fourteen years later, Schwinger and Feynman shared the Nobel Prize in Physics for their respective contributions to the development of quantum field theory. (The Japanese physicist Tomonaga also received a share of the prize for developing similar methods to Schwinger's independently). Unfortunately the Nobel Prize has some very odd and strict rules, and one of them is that it can never be awarded to more than three people. And in the judgment of the Nobel Prize committee, Dyson was the fourth most important contributor to this new theory. 

However quantum field theory was not Dyson's only contribution to science. In the 1940s and 1950s he helped to design a new type of nuclear reactor that was significantly safer than the designs previously - only to have politics and networking see his design passed over by the U.S. government in favour of an arguably less efficient and less safe design developed by naval engineers. Dyson then went on to develop the Orion project, which aimed to use surplus nuclear warheads to propel a spacecraft to speeds far greater than anything that has been attained in the six decades since his proposal. Unfortunately the early testing of his ideas had barely begun when the U.S. signed the first non-proliferation treaties that banned and further use of nuclear explosions to fuel space travel. 

On the more speculative side, Dyson also was known to enjoy very speculative discussions about the technology of alien civilizations, with the most famous example being his proposal of a Dyson sphere. The idea was that a sufficiently advanced society could created solar panels that would orbit their sun, and produce enormous amounts of clean energy. He envisioned a civilization so advanced that they completely enclosed their sun, collecting all of its energy for their own use. This device was dubbed the Dyson sphere in his honour, and has since featured in a number of science fiction stories and television programs.

And those are just a few of his research accomplishments. He was also a great mentor to several generations of physics and engineering students at all levels, and inspired many to pursue science and technology careers. 

Not too bad for someone who famously never completed his own PhD program...

He was a great scientist, a great engineer, and a great mentor to many scientists around the world. He will be missed.