Archive for November 22nd, 2011

No, That's Not It

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”

The Devil is in the Details

Breakthrough material is barely more than air

Researchers at HRL Laboratories, the California Institute of Technology, and the University of California at Irvine have created what they say is the lowest-density material, a lattice of hollow tubes of the metal nickel.
Its volume is 99.99 percent air, and its density is 0.9 milligram per cubic centimeter–not including the air in or between its tubes. That density is less than one-thousandth that of water.

… of if this Paper Has One Side, and Whether Pigs Have Wings!

Of Mobius Strips and the Shape of Things

[E]ven though Earth is (roughly) spherical, the directions you travel can be broken down into two directions: North-South (longitude lines) and East-West (latitude lines). However, there are two places where the latitude-longitude coordinate system breaks down: the North and South Poles, where a single latitude corresponds to all the longitudes simultaneously. In fact, no coordinate system can describe the surface of a sphere without a breakdown at at least one point! It’s not for lack of trying, it’s just a mathematical fact. (There are coordinate systems that break down at only one point, but they’re less useful for cartography.)

Arguments about Möbius are always so one-sided.


Chalmers scientists create light from vacuum

“The result was that photons appeared in pairs from the vacuum, which we were able to measure in the form of microwave radiation,” says Per Delsing. “We were also able to establish that the radiation had precisely the same properties that quantum theory says it should have when photons appear in pairs in this way.”

What happens during the experiment is that the “mirror” transfers some of its kinetic energy to virtual photons, which helps them to materialise.

I would like to take this opportunity to caution anyone against taking this result and recasting it as some hocus-pocus, or a magical way to tap the vacuum as an energy source, but it’s already happened. An article in Forbes is the kind of thing that opens up that door.

After rotating the SQUID at those high speeds, the team were able to detect several real photons that were essentially created from nothing.

No, not essentially. The interesting detail here from QM (and specifically quantum electrodynamics) is that the vacuum isn’t “nothing” and Forbes just completely ignores that to create an abracadabra moment.