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Robert McNees

@mcnees

21 Dec

Mathematical physicist Cécile DeWitt-Morette, who made foundational contributions to the study of Feynman functional integrals, organized the first American conference on general relativity, and founded the Les Houches Summer School, was born #OTD in 1922.
Images: UT-Austin

Cécile Morette grew up in Normandy, studying math and physics at the University of Caen. Her graduate work, on quantum mechanics, took place at the University of Paris. Much of her education took place during the German occupation of WWII.

While in Paris, she worked with Irène and Frédéric Joliot-Curie. After finishing her doctorate in 1947, she moved to Copenhagen to work with Neils Bohr. Her next stop was the Institute for Advanced Study, where she worked with Robert Oppenheimer.

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Robert McNees

@mcnees

20 Dec

Physicist David Bohm, who developed a non-local formulation of quantum mechanics that he hoped would evade some of the conceptually thorny aspects of the Copenhagen Interpretation, and would later inspire the work of John Bell, was born #OTD in 1917.

Bohm’s quantum mechanics textbook was published in 1951. It was very successful, and is still available from Dover as an inexpensive reprint. Here’s my copy:

(Well, it's $25 now. But that is pretty inexpensive as academic textbooks go. I think my copy was $14 back in the day.)
store.doverpublications.com/0486659690.html

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Robert McNees

@mcnees

14 Dec

Happy #Quantum Day!

Max Planck presented work on blackbody radiation to the German Physical Society #OTD in 1900. His novel “quantum hypothesis” suggested that matter emits and absorbs light with frequency f only in discrete chunks of energy E=hf.
Image: AIP

Planck’s quantum hypothesis would revolutionize physics, but he initially thought it wasn’t real. He suspected that the interaction of matter and radiation was tremendously complicated but still governed by the physics known at the time — what we now call “classical physics.”

Invoking quanta of radiation to derive the blackbody emission spectrum was, it seemed to Planck, just a mathematical trick that somehow encapsulated all that complication.

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Robert McNees

@mcnees

14 Dec

Yes, we know, that’s one of the reasons hospitals in your part of Michigan are on the verge of collapsing under a fourth wave.
theatlantic.com/ideas/archive/…

Ugh, the dripping condescension in that piece.

What a weird flex, to point out that you’re just going about life as if nothing has changed when anything less than a life-threatening trauma gets you turned away from your local ER.

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Robert McNees

@mcnees

5 Nov

Freeman Dyson submitted a lovely little two-page paper to Physical Review #OTD in 1951, demonstrating that perturbation theory in quantum electrodynamics produces a divergent series. It's one of my favorites, an absolute classic of the field.
journals.aps.org/pr/abstract/10…

In QED we calculate physical quantities perturbatively, giving a series with increasing powers of a small number α ~ 1/137. So if we calculate the anomalous magnetic moment of the electron (classically it should be g=2) we get a series like:
g = 2 + (1/π) α + (0.656/π²) α² + …

This tells us that the actual magnetic moment of the electron is a little different than what we'd expect from classical considerations. The series above starts with the classical bit (g=2) and then all the subsequent terms represent various quantum mechanical effects.

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Robert McNees

@mcnees

3 Nov

The very good girl Laika, a scrappy three-year-old stray from Moscow, was sent into space aboard Sputnik II #OTD in 1957. The first animal to orbit Earth, she became a national hero. This was cold comfort, since the mission wasn’t designed to return her to Earth.

The press referred to Laika as "Muttnik." Here she is with Mushka and Albina, who were also trained for the mission. Mushka might have gone to space instead of Laika, but she wasn't eating properly.

The plan was to give Laika a painless, fast-acting poison after about a week in orbit. This was the official Soviet account for several years afterward. But it wasn't true. Apparently, Laika died of overheating and asphyxiation somewhere between 6 hours to 4 days after takeoff

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