This was delayed a day by yesterday’s ranting, but I wanted to explain the significance of the people in Monday’s lesser-known quantum mechanic smackdown. I’m happy to see that, as of this morning, three candidates have rallied past the “unique flower” option.
In reverse order of popularity:
Hendrik Kramers was a Dutch physicist who spent a long time working as a student and assistant to Bohr, and thus was involved in a lot of the early attempts to make a working quantum theory. He’s best known for work in condensed matter physics, and for being the “K” in the WKB approximation.
Arnold Sommerfeld was another physicist who did a great deal of work with the early quantum models, trying to extend Bohr’s original model of hydrogen. He also contributed significantly to early solid state physics, and has a few equations named after him. His greatest contribution was probably in the area of education, though, as he was the Ph.D. advisor to an impressive list of people.
Paul Ehrenfest was an Austrian physicist who is best known for Ehrenfest’s theorem, which shows that while quantum particles may individually do weird things, the average of a property over a large number of quantum measurements (the “expectation value”) will obey classical rules. That is, if you subject a bunch of electrons to a known force, and measure their position, some of them will be well ahead of or well behind the place you would predict using classical rules. The average position of all the electrons together, though, will be consistent with what you would get using Newtonian physics.
Ehrenfest is a sort of tragic figure, who made valuable contributions to quantum theory, and was close friends with many of the great physicists of the day. He struggled with depression for many years, and eventually killed himself and his youngest son.
I’m a little surprised to see George Gamow tied for second, as he was a late addition to the list. Gamow’s main contribution to quantum physics was the idea of nuclear decay as a tunneling process, though he’s better known for the α-β-γ paper on nucleosynthesis (which was work done by his student, Ralph Alpher, with Hans Bethe added as a joke without the knowledge of Alpher or Bethe).
Gamow probably rates as highly as he does because of his work as a popularizer of science, through the whimsical Mr. Tompkins stories about a bank clerk who daydreams about relativity and quantum mechanics, and 1, 2, 3… Infinity. He also has one of the best personal stories of any physicist, as his Wikipedia entry includes:
Gamow then worked at a number of Soviet establishments before deciding to flee Russia because of increased oppression. His first two attempts to defect with his wife, Lyubov Vokhminzeva, were in 1932 and involved attempting to kayak: first a 250 kilometer paddle over the Black Sea to Turkey and then from Murmansk to Norway. Poor weather foiled both attempts. In 1933, the two tried a less dramatic approach–Gamow managed to obtain permission for himself and his wife (who was also a physicist) to attend the Solvay Conference for physicists in Brussels. The two attended and promptly defected.
That’s right, his first plan involved kayaking 150 miles over the Black Sea. This was not your typical physics nerd.
Tied with Gamow in the #2 spot is Eugene Wigner, a Hungarian physicist who did a lot of work establishing the role of symmetry in quantum mechanics. There are a whole host of equations and theorems bearing his name, the most important of which, for me, is the Wigner-Eckart theorem. It’s important because it comes up frequently in atomic physics, and I can never remember what the hell it says, despite having been asked about it about a thousand times while preparing for my thesis defense.
He’s also famous for thinking deep thoughts about the nature of reality, as exemplified by the famous essay The Unreasonable Effectiveness of Mathematics in the Natural Sciences. He also extended the Schrödinger cat thought experiment, adding what’s known as “Wigner’s friend:” you imagine that the usual cat experiment was performed by somebody else, who then reports the result to you. The question is, at what point is the cat’s fate determined: when the box was opened, or when you were told about the result? Try that one on your local stoners…
The overall winner of the poll was Max Born, another German physicist who is famous for figuring out the connection between wavefunctions and probability. The relation used to calculate probablilities from wavefunctions is properly known as the “Born rule,” but the name is frequently left out. Born thus also serves as an example of the way that a problem in physics can shift overnight from “impossible” to “trivial.”
Born arguably should have shared the 1932 Nobel Prize with Heisenberg, because he was instrumental in helping Heisenberg develop the matrix formulation of quantum mechanics (with Pascual Jordan), but he didn’t get his Nobel until 1954. He was reportedly a little bitter about this for those twenty years.
Born is also well known to molecular physicists and chemists, for the Born-Oppenheimer approximation, one of the most important tricks for making molecular physics tractable. Any time you see a professor drawing an interaction potential for atoms in a molecule, they’re probably implicitly using the Born-Oppenheimer approximation.
So those are the most important lesser-known quantum pioneers, or at least the ones I could think of Monday morning when I wrote that poll…