Can operatic sopranos really break glasses with their high notes? What note does the trick? How come they don’t break windows and eyeglasses and whatnot at the same time? Can women do this better than men? Can I learn how? Or have I been the victim of an elaborate hoax? –Vox Clamantis, Chicago

I dunno–you ever buy whole-life insurance? Now there was a hoax. Shattering glasses, on the other hand, is totally legit. Enrico Caruso and Italian opera singer Beniamino Gigli are said to have managed it, and I seem to remember Ella Fitzgerald doing it once in a Memorex commercial.

The technique is simple. First you find somebody with perfect pitch and leather lungs. Then get a crystal glass and tap it with a spoon to determine its natural frequency of vibration (this varies with the glass). Next have the singer let loose with precisely the same note. When he or she is dead-on pitchwise, the glass will commence to resonate, i.e., vibrate. Then turn up the V. Bingo, instant ground glass.

What we have here is a graphic demonstration of forced oscillation resonance. If something has a natural rate of vibration, pump in more energy of the same rate and with luck the thing will vibrate so bad it’ll self-destruct. It’s like giving somebody on a swing a good shove at the top of every arc–soon they’ll reach escape velocity and soon after that they’ll be picking vertebrae out of their their sinuses.

Breaking glasses, however, is strictly light entertainment. For real forced oscillation action you want a suspension bridge. In 1831 troops crossing a suspension bridge near Manchester, England, supposedly marched in time to the bridge’s sway. Boy, did they get a surprise. Ever since soldiers have been told to break step when crossing bridges. The same fate befell the Tacoma Narrows suspension bridge in Washington State on November 7, 1940, only it wasn’t soldiers that caused it to collapse, it was the wind.

But back to the home front. Crystal is more vulnerable than ordinary glass because it has more internal structure, which allows waves to propagate. (Take my word for it.) But you can annihilate damn near anything given enough volume. One physicist–obviously one of your classic Roommates From Hell–claims he inadvertently shattered a glass lamp shade while playing the clarinet.

Think of the possibilities. Most of us don’t have the pipes to break glasses by sheer voice power. But heck, we all have clarinets, don’t we? Unfortunately, none of the standard physics cookbooks gives a detailed glass-bustin’ recipe. Too bad. A fascinating classroom demonstration like this would surely convince many young people to give up MTV and devote their lives to science.

So why don’t I figure out a demonstration? I’d love to, but the president’s on line two and besides, judging from the thunderous response to my little misstep regarding hubcap rotation, a lot of you guys out there need something useful to do with your time. Fine. You come up with the experiment, exercising proper safety precautions of course. We need to know the musical instrument or other sound-generating device, the note played, the object shattered (shoot for a pop bottle; crystal’s pretty steep), room conditions, and what you were supposed to be doing while you were blowing off three hours doing this. Your reward? Why, the satisfaction of doing good, plus a possible mention in the next blockbuster edition of Straight Dope: The Book. See what you can do.


You goofed in your column on surname prefixes [April 6]. Mac is a Scottish prefix, not Irish. The Irish use Mc instead.

–Lisa Files, Chicago

A common belief, but wrong. As Edward MacLysaght writes in A Guide to Irish Surnames, “Reference should again be made to one popular misconception, often held outside Ireland, viz. that all Mac names are Scottish–with such well known Irish names as MacCarthy, Macnamara, MacMahon and MacGuinness prominent all over the world this should not be necessary, yet the illusion seems to persist.”

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

Cecil Adams

Cecil Adams is the world’s most intelligent human being. We know this because: (1) he knows everything, and (2) he is never wrong. For more, see The Straight Dope website and FAQ.