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After watching a campy mid-1950s science fiction movie recently, I was left wondering: how radioactive must something be to begin glowing? And could a living creature become that radioactive and still survive, even briefly? --Ranchoth, via AOL

Silly creature. You evidently share the common belief that radioactive things glow. I'm here to tell you, bub: they don't. High-energy radioactive particles sometimes cause other stuff to glow, but that's the exception, not the rule. For example:

Cerenkov radiation. Perhaps you've seen depictions of the eerie blue glow emanating from spent nuclear fuel that's stored underwater. That's Cerenkov radiation. It occurs when beta particles (electrons) travel faster than the speed of light.

You reply: Say what? I thought nothing could travel faster than the speed of light.

Not exactly--nothing can travel faster than the speed of light in a vacuum, c. However, in translucent media, notably water, light travels much slower, at maybe 75 percent of c. A beta particle traveling through air, say, moves considerably faster than light traveling through water.

But suppose a beta particle enters the water. What happens? It throws up a shock wave of photons, much as a boat plowing through water creates a bow wave or a jet creates a sonic boom. I could give you a more elaborate explanation about constructive interference between wave fronts, but it gets too complicated--let's just stick with that bow wave. Note that the radioactive stuff isn't what glows, nor does the water glow once the radioactive stuff is removed.

Fluorescence. When certain compounds are struck by radiation, they glow. For instance, glow-in-the-dark watch dials used to be painted with a mixture of radium and zinc sulfide. Radiation from the former caused the latter to fluoresce. There's nothing magical or dangerous about fluorescence; it can be caused by lots of things, including ordinary sunlight. Again, the radioactive material itself emits no visible light. Madame Curie, who discovered radium, talked about watching the stuff glow in the dark, but the light was emitted by minerals mixed up with the radium, not the radium itself.

Bremsstrahlung. When a charged particle speeds up, slows down, or changes direction, it emits bremsstrahlung radiation. Typically bremsstrahlung consists of invisible X rays, but knowledgeable parties inform me that under certain circumstances it can be visible. I haven't witnessed this personally, but if it occurs as advertised it's perhaps the closest thing to a glow arising from radioactivity itself. Even so,an intervening medium is generally required to speed/slow/divert the charged particle.

None of these phenomena is going to make you or any living creature glow. If you were to tarry near a spent fuel canister bathed in Cerenkov radiation, you'd receive a lethal dose in seconds. You still wouldn't glow, though; you'd just be dead. But at least we'd put this foolish misconception to rest.

Almost every bell tower I've heard chime the time precedes its hourly announcement with a musical preamble--a simple, beautiful tune we all know. It has four measures, each four notes long and then a rest before the next measure begins. What is this thing? Who penned it, and is he pulling in residuals? --Quas, via the Internet

Fat lot of good it would do him--the guy's been cold for a couple hundred years. But at least we know who he is.

What you're referring to is the best-known of all clock chimes, the Westminster Quarters. According to tradition, the words to the tune are, "Oh, Lord our God / Be thou our guide / That by thy help / No foot may slide." The melody was written by one William Crotch in 1794. According to the New Grove Dictionary of Music and Musicians, it consists of four variations on the fifth and sixth bars of "I Know That My Redeemer Liveth," one of the pieces in Handel's Messiah. Crotch persuaded the powers that be to use the tune for the chimes of the new Cambridge University clock in Saint Mary the Great Church. The tune was later copied by the proprietors of other clock towers, most notably in the Houses of Parliament at Westminster, from which its fame spread round the world.

Art accompanying story in printed newspaper (not available in this archive): illustration/Slug Signorino.

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