“Yes, of course. It was a teaching experiment in physics, demonstrating the validity of certain mathematical predictions.”
“Good, as I expected. What, exactly, was this demonstration?”
“It was the Foucault pendulum. It’s one of the two classic demonstrations of the rotation of the Earth.”
Dr. Comber dropped his hand to the writing table in front of him and stared wide-eyed at Richard for a heartbeat or two.
“A demonstration of the rotation of the Earth? A classic demonstration?”
“Yes, first performed in public by the French physicist Leon Foucault in the other history, in 1851.”
Dr. Comber leaned forward with his hands flat on the table and gave a distinct impression of a bulldog. “ Do I understand you correctly? Is this a tangible demonstration that apparently settles the controversy between the Aristotelian and Copernican world models at one stroke? And you did this without telling me, or any other officer or senior fellow of this college? Which will now circulate by rumor, because we don’t tell students not to talk about their studies? And cause all manner of upset to scholars who’ve spent their lives studying this very question?”
Richard froze.
“Exactly. You didn’t think. You considered only the mathematics and natural philosophy, and how to present it to your students. Not altogether a bad thing. But now you need to think about your colleagues as well. You’ve told me and the fellows of your hopes to bring whole new fields of learning here. You wish others to take up these studies, and make the university greater in consequence? For that, you need not merely the acquiescence of your fellows, you need their wholehearted support. You won’t get it by discourtesy.”
Dr. Comber sat back, thinking furiously.
“What must be done now is to present this in a proper and respectful scholarly manner to the whole university, and quickly. But before any announcement, I need to fully understand it myself. I would like you to explain it to me. Completely. Now, I understand your time tonight is to be taken up preparing a lesson?”
“Yes, Dr. Comber.”
“And I’m heavily occupied for the next two days. Can you come here after Hall on Friday?”
“Yes, certainly.”
“Good. Come then with your notes and whatever else is needful to make this clear. I think I may ask Thorndike to join us; he’s spent a good deal more time on this new mathematics than I’ve been able to.”
Richard’s right hand trembled slightly. He told himself it wasn’t from nervousness; after all, he was a seasoned teacher long since. He sat up straighter and looked around the chapel. Nearly time. The seats were filling rapidly with fellows and undergraduates from all over the university. There were at least three heads of colleges. Well, the pendulum was rigged and secured at the start of its arc ready to release, and it wasn’t as if he’d never presented this material before.
The bell overhead rang the hour. Dr. Comber rose and walked to the lectern.
“Masters and presidents, fellows, and scholars, there has been considerable talk of late concerning the knowledge conveyed here from Grantville, in particular a demonstration that took place in this chapel a few nights ago. I’ve asked Scholar Richard Leamington to repeat that demonstration today as a university lecture. I believe this will be of great interest to many of you. Scholar Leamington, if you will.”
Richard went to the lectern, where his notes already rested. He was glad to grasp the side with one hand and steady himself; this was no time to look shaky, insidious malady or no. He straightened, faced the audience with level gaze, took a full breath, and began.
“Thank you, Dr. Comber. Thank you all for coming. As you’ve heard, this will be a demonstration of the Earth’s rotation, by means of mathematics and modern physics used together. Since many of you are able to stay only for the hour allotted to the lecture, we’ll start the physical demonstration first and let it run. I will explain the reasoning while you observe what occurs.” Richard turned slightly and gestured toward the pendulum. “You see before you a weight, suspended by a cord from as high up as the hall allows. As you can see, it’s free to swing in any direction. Notice the sewing needle attached to the bottom of the iron ball with sealing wax, the degree circle marked on the large sheet of paper lying directly beneath the point of suspension, and the narrow ring of sand on the paper. Each time the needle crosses the ring, it will sweep aside a few grains of sand to mark the place where it crossed. The whole apparatus together is called the Foucault pendulum.
“As you can see, we have a clock already running. This is a very accurate laboratory instrument, made in Grantville. Scholar Crosfield will start the pendulum for us now.”
Thomas Crosfield was awake enough today, and blessed with steady hands as well. He stepped forward shielding a lighted candle behind his hand, and gingerly knelt by the pendulum, taking care not to breathe upon it.
Richard fastened his eye on the clock as it came up to the minute. He called out, “Five. Four. Three. Two. One. Loose.”
On that word, Tom brought up the candle and burned through the thread holding back the pendulum. The ball swung away in a stately arc toward the sand ring, while Tom stepped back and blew out the candle. There was the faintest of sounds as the needle flicked through the sand. He returned to his seat and took up a lead pencil and paper.
“Scholar Crosfield has written down the time the pendulum started, and the angle where it first crossed the degree circle. He will continue to do this periodically. By this we will be able to measure the rate at which the plane of oscillation rotates.
“As the pendulum moves, it’s acted upon by the forces imparted by the motion and gravity of the Earth. Starting with the Newtonian equations for these forces and the resulting acceleration of the moving ball, we can show by mathematical proof that at the latitude of Cambridge the plane in which the ball swings must rotate by two hundred and eighty-four degrees per day relative to the stars, or two hundred and eighty-five relative to the sun, just under twelve degrees per hour.” He turned to the movable blackboard standing near the lectern, already filled with the first part of the accompanying derivation. “We begin with the equation for the force of gravity…”
Today Richard had no lectures to give or attend. John Rant had arranged to call later on, to ask his advice regarding the best way to present a seminar on proof by infinite series. For now, though, it was a perfect time to immerse himself in correcting the latest sheaf of typeset proofs for the English edition of the probability textbook. It wasn’t a large batch today; there should be plenty of time to make progress on the translation work as well. In truth, he was happy to be able to spend most of the day seated. Well, perhaps he’d feel more like visiting one of the taverns tomorrow, or just walking by the river. He glanced out the window at a few students hurrying past the great fountain in the court below-it was just as well to be inside in any case. He took up his pen and set to working steadily through the stack by the watery light from the late autumn sky.
Shortly before the midday meal Richard finished the proofreading and set it aside. He was the picture of an absentminded professor as he hurried across the court toward the dining hall, in spite of being far below that exalted rank. He didn’t seek company at dinner today, being occupied in considering the practicality of constructing the apparatus for the measurement of the universal gravitation constant-without sending to the piano makers in Grantville for a length of fine-gauge music wire. Could it be done with a common lute string? Perhaps some testing might reveal the answer.