For The Sunday Gazette



     “It is the same in every recognisable respect,” said the pathologist, “as that inflicted on Richard Tindall….What’s that Sloan…do I happen to know anything about what?”

     “Foucault’s Pendulum, said Sloan confidently.

      The pathologist paused. “Foucault’s Pendulum? Isn’t that the one used for demonstrating the rotation of the earth on its own axis?

    “That’s the one,” said Sloan.

    “I say, Sloan, are you onto something?

    “Perhaps,” responded Sloan. “It would explain the match we found.”


    “When demonstrating Foucault’s Pendulum you have to set it off very carefully indeed. That’s the whole secret. Without a jerk. You do it by mooring whatever’s on the end—say a metal ball—to something fixed….What you usually do to set of Foucault’s Pendulum is to burn through the string which anchors it at the start of its swing.”

     “So you do,” agreed Dabbe. “I’d forgotten that bit. But it doesn’t got out of line right away. Is it something like one degree in five minutes?”

     “Yes, Doctor, twelve degrees per hour, in London,” said Sloan, faithfully repeating what the man from the Museum had said.”


                                                                                                                    Catherine Aird, “His Burial Too”


Now that the Schenectady Museum has chosen to build its new science museum in Schenectady with finality [?], it is interesting to speculate on what should be featured in a potentially imposing atrium. It must be something that will fascinate children and adults alike, knocking their socks off and making them want to come back for repeated visits.

Some years ago, when a GE R&D Center expansion included a remodeling of its entrance and addition of an atrium, its facilities manager, Milan Fiske, proposed that no atrium in a scientific institution worth its NaCl should be without a Foucault Pendulum. Milan, a wonderful man who died a few years ago, had been my contact in the ‘70s when Niskayuna acquired the section of abandoned railroad bed that became the first section of our bike path. He also played the same role in conveying a 94-acre nature preserve to the Schenectady Museum, the very plat that the Museum has just sold to form part of our county’s first state park. His pendulum proposal was rejected, but now the community has a second chance.

The most famous of all pendula is named for Jean Bernard Léon Foucault [Foo Koh] (1819-1868) who installed one at the Panthéon in Paris in 1851 by attaching a 28-kg iron ball one foot in diameter  to a 200 ft. wire suspended from its dome. When a pendulum’s swing is started carefully as described in Catherine Aird’s mystery, the ball will seem to oscillate back and forth in a straight line, but if it is watched carefully for some minutes the plane of its swing will seem to rotate. Actually, the plane doesn’t change at all; it is the earth that rotates underneath the pendulum.

The time for the plane of the pendulum to complete a circuit depends on latitude. For a Foucault Pendulum at either the north or south pole, the plane of its swing would be perpendicular to the equatorial plane, so a circuit would take exactly 24 hours. For one anywhere on the equator, its circuit would be infinitely long, meaning that there would be no differential rotation at all. For points at intermediate latitudes, the number of hours for a circuit is 24 divided by the trigonometric sine of the latitude. (Don’t go away, I didn’t write a formula, I just described one.)

At London’s latitude of 51.5 degrees N, the circuit would take 30.7 hours, which is 11.7 degrees per hour—Aird’s research in placing the round number of 12 degrees in Sloan’s mouth was impeccable. At the latitude of New Orleans, 30 degrees, a circuit would take exactly 48 hours, or two days, faster than it took FEMA to arrive. At the latitude of Schenectady, about 42.8 degrees N, a circuit would take just a few minutes less than 36 hours, a day and a half.

There are many Foucault Pendula in the United States, but, because of the lack of Pantheonian structures to house them, they tend to be limited to a more practical height of 60 feet or so. Perhaps the most interesting is the one at the Smithsonian in Washington whose bob, over the course of its 38-hour circuit, gradually knocks down large pins arrayed at regular intervals around the circumference of the circle whose diameter is defined by the extremities of the bob’s swing. Tethered from a height of 60 feet or more, a pendulum’s bob takes just a few seconds to sway from one extreme position to the other, a rhythm that has a mesmerizing effect that tends to quell the initial exuberance of children rushing into the atrium. This is very pleasing to their parents and museum management.     

Umberto Eco’s novel called “Foucault’s Pendulum” was published in 1990, a translation of an earlier Italian version. But it is much less readable than his fascinating “Name of the Rose” of 1983. It is actually a fat 656-page doorstopper that is not about Leon Foucault at all; it is a literary pun that relates to the philosopher Michel Foucault (1926-1984). Some reviewers credit its mystic plot as having set the stage for “The Da Vinci Code,” another literary joke.

The most famous fictional story relevant to today’s topic is, of course, Edgar Allan Poe’s brilliant “The Pit and the Pendulum” (online at ). Set at the time of the Spanish Inquisition, a prisoner awakens in a darkened room which, after much careful exploration, is found to contain a deep circular pit in its center and a slowly descending pendulum whose bob is a razor-sharp scimitar.

After a few days, the prisoner, who failed to fall into the pit, is bound in such a way that the pendulum’s blade swings perpendicular to his midsection, coming closer and closer with each successive cycle. He fears that he is about to become only half the man he used to be. 

But even Poe’s macabre stories sometimes have a happy ending; French militia come storming in to the rescue. The tale has been filmed twice, once in 1961 and then again in 1991. The first starred Vincent Price. The second was Priceless.

Edwin D. Reilly, Jr. lives in Niskayuna and is a regular contributor to the Sunday Gazette opinion pages.