American Physicists and the Under-rating of Experiments

At Scientific American’s blog network, Ashutosh Jogalekar muses about the “greatest American physicist”, eventually voting for Josiah Willard Gibbs, one of the pioneers of statistical mechanics. As both times I took StatMech (as an undergrad and in grad school), it was at 8:30 in the morning, I retain almost no memory of the subject, and will bow to greater experience in assessing Gibbs’s importance.

I do, however, want to take issue with one thing in the post. When assessing the historical place of American physics, he writes:

Here’s my personal list for the title of greatest American physicist in history, in no particular order: Joseph Henry, J. Willard Gibbs, Albert Michelson, Robert Millikan, Robert Oppenheimer, Richard Feynman, Murray Gell-Mann, Julian Schwinger, Ernest Lawrence, Edward Witten, John Bardeen, John Slater, John Wheeler and Steven Weinberg. I am sure I am leaving someone out but I suspect other lists would be similar in length. It’s pretty obvious that this list pales in comparison with an equivalent list of European physicists which would include names like Einstein, Dirac, Rutherford, Bohr, Pauli and Heisenberg; and this is just if we include twentieth-century physicists. Not only are the European physicists greater in number but their ideas are also more foundational; as brilliant as the American physicists are, almost none of them made a contribution comparable in importance to the exclusion principle or general relativity. […]

More importantly though, the sparse list of great homegrown American physicists makes two things clear. Firstly, that America is truly a land of immigrants; it’s only by including foreign-born physicists like Fermi, Bethe, Einstein, Chandrasekhar, Wigner, Yang and Ulam can the list of American physicists even start to compete with the European list. Secondly and even more importantly, the selection demonstrates that even in 2013, physics in America is a very young science compared to European physics. Consider that even into the 1920s or so, the Physical Review which is now regarded as the top physics journal in the world was considered a backwater publication, if not a joke in Europe (Rhodes, 1987). Until the 1930s American physicists had to go to Cambridge, Gottingen and Copenhagen to study at the frontiers of physics.

I would argue that there’s a word missing near the end of that last sentence, namely “theoretical.” It’s absolutely true that American theorists like Oppenheimer studied in Europe in order to learn from the quantum pioneers, but I would say that even by the 1930’s, American experimental physics was nearly equal to that in Europe. Michelson, Millikan, Lawrence are a trio to put up against anyone Europe has to offer in that same time period (Thomson and Rutherford are the big names on that side of the pond), and you can throw in people like Compton and Davisson and Germer as well. Depending on whether you count cosmology as part of physics, you could probably get Hubble into the mix on the American side, as well.

Now, it’s true that they didn’t contribute “foundational” ideas to physics, which tends to see them pushed somewhat down the list of “greats,” but I think that’s a mistake. Yeah, the exclusion principle and general relativity are great ideas, but big ideas are meaningless unless you can measure them, and Americans were essential to that process. Einstein famously proposed a revolutionary particle theory of light to explain the photoelectric effect, but it was Millikan’s measurements (which grudgingly confirmed the photon model) that forced people to take it seriously, and Compton’s gamma-ray scattering experiments helped seal the deal.

This is, of course, a personal obsession with me, but I think it’s essential to remember that theory and experiment go hand in hand. Revolutionary theories arise because they’re needed to explain experimental results, and they’re ultimately accepted because they’re found to agree with further measurement. Experiments get downplayed because they’re full of fiddly technical details and harder to explain and interpret, but they’re absolutely essential, and the US was pulling its weight in experimental physics even before top theorists started fleeing fascist regimes. (This is prompted in part by a bunch of recent reading on the history of 20th century physics, where even some big European names grudgingly admit that the Americans were good experimenters…)

So, while Europe is still ahead, I think it’s a somewhat closer thing than Jogalekar suggests, when you properly weight the two facets.

As for the general question of who was the greatest American physicist, I’d probably cast my vote for John Bardeen, who is, after all, the only person to share two Nobel Prizes in Physics. He’s the “B” in the “BCS” theory of superconductivity, but more importantly helped invent the transistor. It’s hard to think of anyone whose contributions to physics had a bigger influence on the way we live today, and if that’s not greatness, I’m not sure what is.