Outside Online Archives

Outside magazine, July 1996

By Patrick Clinton

Double rainbows are fairly common. But has anyone ever noted a triple rainbow?
Baxter Menzies, El Paso, Texas

There are credible reports of all kinds of permutations on the rainbow theme: Fogbows. Sandbows. Moonbows. Infrared rainbows. But there's never been a verified sighting of a true triple rainbow. As you may know, a rainbow appears when the sun is behind you, shining on a patch of rain or mist that's in front of you. Says Wisconsin physicist and rainbow ace Robert Greenler, "The primary rainbow is created when light rays shine into the droplets, reflect once, and come out. Rays that reflect twice create the secondary rainbow." But what about rays that reflect three times? They ought to create a third rainbow, right? Theoretically, but the question is, Where do you look for it? "The assumption was that it must be near the primary and secondary rainbows, only fainter," says Greenler. "Yet when you do the physics, it turns out the tertiary rainbow would be on the other side of the sky, seen as a circle around the sun."

In 1914 the Journal of the Royal Meteorological Society reported an incident in which parts of six bows were observed simultaneously. However, this sighting did not count as an official sextuple; most likely it was just a double rainbow accompanied by supernumeraries, little fragments of the primary rainbow that crop up under certain conditions. So, alas, if you see what appears to be a triple or triple-plus rainbow, it's probably not the real McCoy.

Why don't cows cross cattle guards, even cattle guards that are merely painted on the pavement?
Diane Bristol, Bozeman, Montana

An ordinary cattle guard looks like the business end of a barbecue grill-loosely spaced pipes arranged over a hole. If you've got feet like a cow, there's no way to get secure footing on it, and if you've got the psyche of a cow, that's enough to send you back to the barn. Because cows don't have good depth perception, they can't readily distinguish between a real guard and a painted one. "Any sharp edge between light and dark can throw them off," explains Penn State agricultural engineer Bob Graves. "When a hose is lying across the ground, they'll look at it and wonder if it's a hole they could fall in." All the same, Graves doesn't put much faith in painted guards. He says there's a good chance you'll run into the occasional cow who "hasn't read the book that says they won't cross them." And, as he rightly points out, chasing cows is a drag.

My boyfriend always sneezes when he emerges from a theater on a sunny day. Why is this?
Nanci Kulig, Philadelphia

Your guy has photic sneeze reflex, an untreatable hereditary condition that affects up to 20 percent of Americans. Its cause is unknown, although some researchers think it involves a neurological short-circuit linking the retina and the nose. For people with PSR, any sudden exposure to bright light can trigger a fit of as many as 15 sneezes.

The occasional nasal eruption is, for most of us, a mere inconvenience. But for certain people, like fighter pilots, it can be lethal. "If you're landing a plane or you're in a dogfight and you turn into the sun and have to sneeze, that could be dangerous," says Lieutenant Colonel Ray Breitenbach, an Air Force Reserve doctor and PSR sufferer who has studied the phenomenon. Breitenbach tested whether high-tech goggles help stop the sneezing. (They don't.) He plans to conduct a study in which he'll treat Air Force cadets to a movie and then wait outside the theater as they emerge. Instead of calling out "gesundheit," he'll be scribbling notes, trying to spot any aviation disasters in the making.

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