Someone Explain the Physics to Me

WASHINGTON (AP) — Terrorists may seek to down aircraft by shining powerful lasers into cockpits to blind pilots during landing approaches, U.S. officials warned in a bulletin distributed nationwide.


Uh-huh. Shining a laser into the cockpit of a moving plane precisely enough to not just one target less than the size of a quarter, but four (two pilots, times two retinas apiece). Is it just me, or does this sound just a wee bit implausible?

… the Boston Globe supplies a few more details, including some skepticism other grounds: wouldn’t the cockpit glass refract the beam? I’m actually counter-skeptical: I would have thought that a cockpit window, like most normal windows, would be designed not to cause significant refraction in the visible spectrum. (As for invisible wavelengths, good luck aiming, right?)

The story also has a few more details about reported incidents: it seems as though all the data here comes from pilot reports followed by subsequent medical diagnoses. These are the people, let us remember, who insisted on banning the use of electronic devices during takeoff and landing because they had a hunch those devices were interfering with planes’ controls.

Finally, there is some speculation about laser light shows. Again, I am baffled. The geometic sense that tells me it’s hard to hold a beam on the right part of a moving plane at distance tells me you’re even less likely to point the beam in the pilot’s eyes for long enough by pure accident. I suppose that factor could be compensated for, however, if there were an epidemic of laser light shows randomly shooting up at small angles to the horizon (anything less than about 45 degrees will hit the plane’s nose, rather than cockpit glass, I’d hazard). But the odds would still seem to call for an awful lot of laser lights shows to generate two cases in a few months.

… I then took this question to Nexis. I found a 1995 Times of London story that pilots had forced Las Vegas light shows to stop using lasers because 51 pilotsclaimed to have been blinded by a “bright flash” on approach to McCarran. There was also a more recent small story contemporaneously documenting one of the two incidents to which the Boston Globe referred. I’m guessing that the Globe reporter did exactly what I did and sourced that part of his story to the previous one.

… Holy shit, I know the Globe reporter! Time to fire off an email.

Stephen points out that the laser-in-pilot’s-eyes thing is a plot point in a Tom Clancy novel. I wonder whether the DHS has mixed up its factual terrorists with its fictional ones.

… The reporter put essentially everything he had into the article.

… But here’s a laser safety FAQ and a Metafilter post with some helpful numbers. Long story short, I think my skepticism about power output was at least partly ill-founded. Per the FAQ, a 1 mW laser, from a mile away, may have a beam that’s 4 feet in diameter, with a power level of 35 nW — about the brightness of a 100 wat bulb seen from 88 feet away. But 1 mW is a laser pointer; serious lasers come much much brighter: 500 mW and above. With those numbers, I’m more willing to believe that there’s a genuine danger. Also, did you know that a division of the FDA regulates lasers?