Physicists find charge separation in a molecule consisting of two identical atoms

Physicists from the University of Stuttgart show the first experimental proof of a molecule consisting of two identical atoms that exhibits a permanent electric dipole moment. This observation contradicts the classical opinion described in many physics and chemistry textbooks.

This statement bugs me for two reasons. One is the “contradicts classical opinion” statement, because statements like this usually are a matter of context, and the contradiction occurs when you strip the context. In physics, most equations come with caveats. There are few that apply universally; most are derived under a set of assumptions or meant to apply under specific conditions. However, there are some who try to apply the equations under conditions that violate the assumptions and should not be surprised when the equation fails. And I think this is one of those cases. The “no permanent electric dipole moment” argument is one of symmetry. As long as the symmetry is maintained, there is no EDM, and electrons distributions a these cases should ensure that symmetry. But what happened in this research is a way was found to violate that symmetry — by putting one of the pair of atoms into a Rydberg state (high energy level, maximum angular momentum for the state, which makes the atom physically large). The electron is far from the nucleus and the other electrons can’t compensate. That’s pretty neat, and I think we should celebrate that, rather than the sensationalistic “They said it couldn’t be done!” half-truth.

The other part is the use of “permanent”. This is an excited state. It’s not permanent, though Rydberg states tend to be long-lived. Though that may also be a terminology issue, with permanent simply meaning lives long enough to be measured.

Here’s a better (IMO) write-up on the phenomenon.

Electrons out of balance

How Does Faster-Than-Light Quantum Communication Work?

Every so often, I ask readers to submit their sci/tech questions, so that I can go pester people until I have some answers that I can share with the rest of the class. One recent question was: “How does faster-than-light quantum communication work?” Short answer: it doesn’t. But of course there’s more to it than that.

Bonus: entanglement explained correctly, for which I am thankful

A number of stories have come out about how OPERA has “confirmed” the faster-than-light finding that was reported recently. Well, not really — they used shorter pulses to address one of the concerns: that the very wide (~10,000 nanosecond) pulses might have given a misleading result when the curve-fitting took place. So they shortened the pulse width, and got the same 60-nanosecond offset. But this doesn’t address other systematics that might be responsible, so it doesn’t really count as a confirmation. Validation will only come when different setups, with different systematics, agree. (The Bad Astronomer has made a similar observation)

There are also reports about how the FTL result has been refuted: Study rejects “faster than light” particle finding

That’s not quite right, either. The model says that FTL neutrinos should lose energy, in a process analogous to Cerenkov radiation that is emitted by charged particles. But since we’re talking about new physics, theory is no proof of anything. Proof (scientific proof, that is) comes from experimental confirmation. Nature has the final say. So this model is no more a refutation of the FTL neutrinos than relativity is — they are both good reason to suspect the result and demand a very high standard of evidence, but they do not constitute a true rejection of the phenomenon.

Similarly, I could (and would) dismiss idle claims of perpetual motion based on the laws of thermodynamics, but if someone were to build an actual perpetual motion device, there would be ways to test it, and very stringent testing would be demanded. And nobody would be surprised when the device ultimately failed. But if the device somehow worked, all the fingers in the world pointing to a thermodynamics textbook wouldn’t change that. Another example (from my field of work) would be laser cooling, when experiment contradicted the prevailing theory, which is a strong parallel to what is happening with the neutrino saga.

There’s also this bit that I noticed:

The September announcement of the finding, backed up last week after new studies, caused a furor in the scientific world as it seemed to suggest Albert Einstein’s ideas on relativity, and much of modern physics, were based on a mistaken premise.

The test was not backed up, as I have already written, and I wouldn’t characterize this as a furor. I haven’t seen any protests about this (the Nobel riots notwithstanding); there don’t seem to be any moves to “occupy CERN” of which I am aware.

Here’s a similar take on the “refutation”