## Tuesday, September 29, 2015 ... //

### Enrico Fermi: a birthday

Enrico Fermi was born 114 years ago, on September 29th, 1901, in Rome. He died on November 28th, 1954 in Chicago, thanks to the stomach cancer. He was most likely the second most important Italian physicist after Galileo Galilei (check this list). Apologies to Rovelli, Dorigo, and others who would place themselves above Fermi and maybe Galileo.

When he was 17 and he was entering the college in Pisa, he wrote an essay about a Fourier-series analysis of solutions to the partial differential equation describing... waves on a string. The examiner interviewed Fermi and determined that the essay would have been good enough for a PhD in Pisa. That was probably no overstatement because the analysis was largely equivalent to a big part of the first or second chapter of any string theory textbook.

Before he was 20, he learned quantum mechanics so well that he was already hired to lead a seminar on it. He went on to master the tensor calculus and GR later. At some moment, he wanted to study mathematics but switched to physics rather soon.

When he was 20, he resolved a problem – found a refinement of the arguments that were producing $E=(3/4)mc^2$ for charged objects of mass $m$. At that time, he was already doing numerous experiments – in X-ray crystallography. This was the subject of his PhD thesis that he defended when he was just 21. One year later, he already loudly noticed that $E=mc^2$ seems to imply that one may extract a huge amount of energy from a modest mass.

In 1924, he became a free mason. At that time, he began to travel a lot – and met Heisenberg, Jordan, Lorentz, Einstein, and many others. When quantum mechanics was born in 1925, he was already lecturing about it.

The young 25-year-old professor did his most important purely theoretical work in fundamental physics in 1926 when he wrote the paper about the Fermi-Dirac statistics. Fermi's paper came after an exclusion principle paper by Pauli but before an independent (Fermi-like) paper by Dirac. The rest of his research life was dedicated to radioactivity. In 1938, right before the war started, he was wittily given a Nobel prize for "induced radioactivity [plus some new elements]". The term "induced radioactivity" surely sounds more innocent than it should. ;-) But he was just getting started.

(Back to the late 1920s: he had a nice academic job in Rome, married Laura Capon, a Jewish woman, and had two kids. In 1929, Benito Mussolini named him a member of the Royal Academy of Italy – just to make you sure that the duce wasn't doing just bad things. Well, the probably grateful Fermi joined the Fascist Party soon afterwards – and only denounced it sometime in 1938 when some new racial laws were approved. When the SJWs learn about Fermi's membership in the party, the Fermilab will surely be renamed and the fermions will be excluded from all polite universities.)

Did everyone accept Fermi's statements about the beta-decay from the very beginning? You may guess what the answer is with these great minds. When he submitted his famous paper on beta decay to Nature, the editor rejected it because "it contained speculations which were too remote from reality". This is what the lagging, inferior minds say about cutting-edge research in theoretical physics in most cases, even today. (Note that Fermi's earlier work on string theory did not provoke this kind of criticism, however.) The paper using the new term "neutrino" that Fermi invented (but Pauli got the idea in 1931) was therefore published in German and Italian before it appeared in English.

As Wikipedia argues, he never forgot this experience of being ahead of his time. His protégés were therefore told "to never be first; to try to be second". James DNA Watson was preaching pretty much the same thing to his protégés.

Nature eventually published his report on beta decay in January 1939.

Back to the 1930s. Fermi made Italy sort of attractive for foreign scientists. Hans Bethe became a frequent visitor. Fermi and Bethe wrote a paper in 1932.

Once he left Italy for Columbia University in the late 1930s, in order to save his Jewish wife, he reproduced some other people's fission experiments. Fermi moved to Chicago where he built the first nuclear pile, a primitive nuclear reactor that went critical in December 1942 in a "squash court"; Russians translated the location as "pumpkin field" and yes, I had to think for a minute to realize that a "squash court" is relevant for athletes, not farmers. :-) Every step was carefully and brilliantly planned.

This wisdom and experiments were also useful during the Manhattan project in which Fermi, who became a U.S. citizen in 1944, assisted. When you summarize his work on nuclear technology, you will see that Fermi was the most practically talented man among the great 20th century theoretical physicists, the greatest theorist among the 20th century experimenters, and the sometimes (literally) explosive impact of his work makes the comments about his work being detached from reality doubly ludicrous.

He had to think, write, and do a lot to realize all his achievements associated with nuclear physics. But if we measure the impact on public's perception of scientifically loaded questions per word, his most influential results are three words from the 1950s: "Where are they?" The Fermi "paradox" – which is really an empirical argument pretending to be a question – shows that it is rather unlikely for the Universe to be filled with too many very advanced and large civilizations at a given moment.

Some years ago, I have talked to a student of Fermi. She admired him and she was certainly not the only one.

Other science events

By the way, I finally haven't written about several recent science events out there. NASA found evidence of "flowing water on Mars". Some super-salty super-shallow creeks deduced from wet rocks. I have "almost" known that this would be the announcement since Friday. The other option was "life on Mars" which seemed insane. You know, a wet rock on Mars is insanely far from life. Water is just the simplest chemical compound containing oxygen, the Z=8 element. There are some solid and other compounds including oxygen and they end up beneath the surface because they are heavier and gravity operates in this way. Those on the surface are lighter, liquid or gases, and water is in between. The path from this very simple molecule – oxygen atom plus two separate protons etc. – to a complex DNA molecule seems as long as before.

There were also "tests of Bell's inequality done right". Two loopholes were closed, the hype says. Well, it didn't seem to me that those loopholes were closed for the first time. At least in other experiments, the same loophole as a matter of principle was more or less ruled out. Also, these loopholes aren't the reason why so many people continue to feel badly about quantum mechanics. So I just can't get excited about any of these awkward technical improvements in the new experiment.

ATLAS and $2.9\TeV$

In my deep search of the Internet, I found that not only CMS but also ATLAS has seen a nice $2.9\TeV$ event in June 2012. Two muons and a jet. Well, a Z'-boson shouldn't have a jet in the final state. The collision was in this paper, Figure 9.