Sunday, June 23, 2019

Comparing Bohm to a medieval astrologer

Some scientists like to think that they are fighting the good fight of finding truth against modern inquisitors. It is usually nonsense. I don't know of any examples of good science being suppressed.

A Nautilus essay:
The Spirit of the Inquisition Lives in Science
What a 16th-century scientist can tell us about the fate of a physicist like David Bohm. ...

I’ve been schooled in quantum physics and trained to think rationally, dissecting facts and ideas dispassionately. And here I am constantly carrying on imaginary conversations with a 16th-century astrologer. ...

Those communist associations, coupled with the national security implications of his Ph.D. work, made him a target for Senator Joe McCarthy’s crusade against un-American activities.

Bohm refused to answer questions, and refused to name anyone that the McCarthyists should investigate. He was arrested. By the time he was acquitted, he had been suspended from Princeton. In 1951, unemployable in the United States, Bohm took a job in Brazil. ...

Bohm’s idea of an invisible, undetectable pilot wave was roundly criticized, but a man who had survived the McCarthy witch hunts was not easily put off. Having overcome the most heinous character assassination of the era, he could take a little heat. ...

But there are two problems. The first is that, in order to get the predictions right about the interference effect and the ultimate distribution of the photons at the detector, you have to work backward from the final result.

The second problem is that Bohm’s pilot wave is odd—in a way that physicists call “nonlocal.” This means that the properties and future state of our photon are not determined solely by the conditions and actions in its immediate vicinity. ...

The de Broglie-Bohm interpretation of quantum physics, as it is now known, is not popular. Only one venerated physicist has ever really championed it: John Bell, the Irishman who came up with the first definitive test for the existence of entanglement. ...

In the end, we can be reasonably confident that none of our current interpretations of quantum theory are right.
This is ridiculous. Bohm was a Communist who refused to testify about his Communist activities. That is not the behavior of a truth-seeker, or of a loyal American.

His physics work was junk. It did inspire Bell, and Bell inspired a generation of crackpots, but his interpretation of quantum mechanics is very much inferior to Copenhagen.

Say you want to understand light going thru a double-slit and creating an interference pattern. If you think of light as a wave, then all waves cause interference patterns, and it is obvious. Or you can think of light as photons with wave-like properties. Some like to think of light as photons, but funny particles that can be in two places at once and go thru both slits.

Bohm says the photons really are particles, and a photon only goes thru one slit. That is supposed to make his interpretation intuitive. But the photon is guided by some distant ghostly pilot wave that tells it what to do. You could trap the photon in a box, but you cannot predict the photon's behavior based on what is in the box, because it is controlled by a pilot wave that is not even in the box.

Why would any prefer that explanation?

It is somewhat interesting to see what can be done with a goofy interpretation of quantum mechanics, but that's all. As far as I know, Bohm's interpretation only works in contrived test cases, and it is not useful for anything.

After writing this, I see that Lubos Motl posted a rant against the same article:
Meanwhile, Brooks is fighting for "progress". Which means to ban the uncertainty principle and return us to classical physics where the position and momentum existed simultaneously and without any measurement. And his progress involves the talking to the ultimate authorities – the ghosts of astrologers. ...

And it's completely wrong to arbitrarily identify 20th century scientists such as Niels Bohr with the Inquisition etc. Bohr has had clearly nothing to do whatsoever with the Inquisition. Also, it's absolutely wrong to defend scientific theories according to the subjective likability of their political views. Whether David Bohm was a commie – while Pascual Jordan was a staunch believer in the ideas of NSDAP – is completely irrelevant for the evaluation of the validity of their scientific propositions. I would have trouble with the political views of both of these men but their physics must clearly be considered as an entity that is independent from the men's politics.
I don't know whether there is a relation between being a Commie and pushing a spooky action-at-a-distance theory, or in believing that Bohr led an inquisition against Einstein.

Wanting to give a precise position for the electron at all times is an attempt to ban the uncertainty principle, and deny the basic wave theory of matter that was established a century ago.

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