Links for 2009-10-29


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Scientists and Kool-Aid § Unqualified Offerings "In my department weâll often produce documents that have lots of buzzwords, but nobody really takes it seriously. You can always get appreciative chuckles in a department meeting if you poke fun at your own handiwork. Higher on the food chain,…
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I wanted to comment on the New York Times article. While the experimental work, measuring the arrival times of gamma-rays from a distant gamma-ray burst is quite impressive, the article is extremely misleading about its implications. They quote someone bemoaning the lack of any laboratory experiments to test for quantum gravity effects and make it sound like this is the first time astrophysical data has been used to place strong constraints on Lorentz violation. In fact, there are already other, substantially better constraints coming from both laboratory and astrophysical data.

I think the current work is being hyped for being a "cleaner" test of Lorentz violation. There's relatively little interpretation involved in getting from timing data to constraints on possible violation. The existing astrophysical constraints are terrific, but there's a little bit more work involved.

That's my guess, anyway, as somebody well outside that field.

I took exception to two things:

1) There was no mention at all of photon mass. An alternative explanation of arrival time differences would be a tiny photon mass. I should go see how the current constraints on the photon mass and charge fit with these data, but that should have been mentioned. Ditto for the index of refraction of space, which is not entirely empty. After all, we are talking about 1 part in 10^17.

2) "Quantum theory ... reduces life on subatomic scales to a game of chance in which elementary particles can be here or there but not in between." Not so, with the very limited exception of a bound state where there is a node in the wavefunction. And even in that case, a particle does not have to magically appear somewhere else when transitioning between two states. The author is describing Bohr's bogus "quantum jump" version of pre-quantum (semi-classical) mechanics that had orbits rather than orbitals.

What's unusual about the effects considered in this instance was that they become more pronounced at higher photon energies. Most ordinary changes to the photon dispersion relation (and even a mass term is ordinary by these standards) have less effect on photon travel times at higher energies. There are bounds on the photon mass coming from measuring arrival time differences for lower-energy photons, but even the best of these are not competitive with bounds based derived from measurements of static fields.