From ``Foucault's Pendulum'', by Umberto Eco.

That was when I saw the Pendulum.

The sphere, hanging from a long wire set into the ceiling of the choir, swayed back and forth with isochronal majesty.

I knew -- but anyone could have sensed it in the magic of that serene breathing -- that the period was governed by the square root of the length of the wire and by pi, that number which, however irrational to sublunar minds, through a higher rationality binds the circumference and diameter of all possible circles. The time it took the sphere to swing from end to end was determined by an arcane conspiracy between the most timeless of measures: the singularity of the point of suspension, the duality of the plane's dimensions, the triadic beginning of pi, the secret quadratic nature of the root, and the unnumbered perfection of the circle itself.

I also knew that a magnetic device centered in the floor beneath issued its command to a cylinder hidden in the heart of the sphere, thus assuring continual motion. This device, far from interfering with the law of the Pendulum, in fact permitted its manifestation, for in vacuum any object hanging from a weightless and unstretchable wire free of air resistance and friction will oscillate for eternity.

The copper sphere gave off pale, shifting glints as it was struck by the last rays of the sun that came through the great stained-glass windows. Were its tip to graze, as it had in the past, a layer of damp sand spread on the floor of the choir, each swing would make a light furrow, and the furrows, changing direction imperceptibly, would widen to form a breach, a groove with radial symmetry -- like the outline of a mandala or penticulum, a star, a mystic rose. No, more a tale recorded on an expanse of desert, in tracks left by countless caravans of nomads, a story of slow, millennial migrations, like those of the people of Atlantis when they left the continent of Mu and roamed, stubbornly, compactly, from Tasmania to Greenland, from Capricorn to Cancer, from Prince Edward Island to the Svalbards. The tip retraced, narrated anew in compressed time what they had done between one ice age and another, and perhaps were doing still, those couriers of the Masters. Perhaps the tip grazed Agarttha, the center of the world, as it journeyed from Samoa to Novaya Zemlya. And I sensed that a single pattern united Avalon, beyond the north wind, to the southern desert where lies the enigma of Ayer's Rock.

At that moment of four in the afternoon of June 23, the Pendulum was slowing at one end of its swing, then falling back lazily toward the center, regaining speed along the way, slashing confidently through the hidden parallelogram of forces that were its destiny.

Had I remained there despite the passage of hours, to stare at that bird's head, that spear's tip, that obverse helmet, as it traced its diagonals in the void, grazing the opposing points of its astigmatic circumference, I would have fallen victim to an illusion: that the Pendulum's plane of oscillation had gone full circle, had returned to its starting point in thirty-two hours, describing an ellipse that rotated around its center at a speed proportional to the sine of its latitude. What would its rotation have been had it hung instead from the dome of Solomon's Temple? Perhaps the Knights had tried it there, too. Perhaps the solution, the final meaning, would have been no different. Perhaps the abbey church of Saint-Martin-des-Champs was the true Temple. In any case, the experiment would work perfectly only at the Pole, the one place where the Pendulum, on the earth's extended axis, would complete its cycle in twenty-four hours.

But this deviation from the Law, which the Law took into account, this violation of the rule did not make the marvel any less marvelous. I knew the earth was rotating, and I with it, and Saint-Martin-des-Champs and all Paris with me, and that together we were rotating beneath the Pendulum, whose own plane never changed direction, because up there, along the infinite extrapolation of its wire beyond the choir ceiling, up toward the most distant galaxies, lay the Only Fixed Point in the universe, eternally unmoving.

So it was not so much the earth to which I addressed my gaze but the heavens, where the mystery of absolute immobility was celebrated. The Pendulum told me that, as everything moved -- earth, solar system, nebulae and black holes, all the children of the great cosmic expansion -- one single point stood still: a pivot, bolt, or hook around which the universe could move. And I was now taking part in that supreme experience. I, too, moved with the all, but I could see the One, the Rock, the Guarantee, the luminous mist that is not body, that has no shape, weight, quantity, or quality, that does not see or hear, that cannot be sensed, that is in no place, in no time, and is not soul, intelligence, imagination, opinion, number, order or measure. Neither darkness nor light, neither error nor truth.

I was roused by a listless exchange between a boy who wore glasses and a girl who unfortunately did not.

``It's Foucault's Pendulum.'' he was saying. ``First tried out in a cellar in 1851, then shown at the Observatoire, and later under the dome of the Pantheon with a wire sixty-seven meters long and a sphere weighing twenty-eight kilos. Since 1855 it's been here, in a smaller version, hanging from that hole in the middle of the rib.''

``What does it do? Just hang there?''

``It proves the rotation of the earth. Since the point of suspension doesn't move...''

``Why doesn't it move?''

``Well, because a point...the central point, I mean, the one right in the middle of all the points you see...it's a geometric point; you can't see it because it has no dimension, and if something has no dimension, it can't move, not right or left, not up or down. So it doesn't rotate with the earth. You understand? It can't even rotate around itself. There is no `itself.' ''

``But the earth turns.''

``The earth turns, but the point doesn't. That's how it is. Just take my word for it.''

``I guess it's the Pendulum's business.''

Idiot. Above her head was the only stable place in the cosmos, the only refuge from the damnation of the panta rei, and she guessed it was the Pendulum's business, not hers. A moment later the couple went off -- he, trained on some textbook that had blunted his capacity for wonder, she, inert and insensitive to the thrill of the infinite, both oblivious of the awsomeness of their encounter -- their first and last encounter -- with the One, the Ein-Sof, the Ineffable. How could you fail to kneel down before this altar of certitude?