"Classic" Timekeeping, Part I: Introduction
Following the suggestion and subsequent reminder (nothing like a deadline to get the creative juices flowing) from gg at Skulls in the Stars, I’ve got two “old” papers that I’m going to summarize.
I recommend choosing something pre- World War II, as that was the era of hand-crafted, “in your basement”-style science. There’s a lot to learn not only about the ingenuity of researchers in an era when materials were not readily available, but also about the problems and concerns of scientists of that era, often things we take for granted now!
These are from 1931, fulfilling the pre-WWII criterion, when you still had individuals engaging in research that were self-financed or supported by a patron and much of the equipment was self-manufactured. The science in this case was largely self-funded, and as for the “basement,” well, it’s a pretty fancy basement as you’ll see, as one might suspect of someone who can fund his own science. But classic nonetheless. There’s a bit to do, and I’m going to break it up into more manageable chunks.
The papers in question are from the Monthly Notices of the Royal Astronomical Society, Vol. 91, published in 1931, and are “The Precise Measurement of Time” by Alfred L. Loomis (p. 569-575) and “Time, Analysis of records made on the Loomis chronograph by three Shortt clocks and a crystal oscillator” by Brown, E. W. & Brouwer, D. (p.575-591). (I, know, I know. They sound like tabloid headlines, don’t they?) The first paper describes various apparati used, and the second describes a particular measurement that was of interest to me.
The measurement of interest came about from a question on pendulum clocks. Anyone who has taken introductory physics has seen that the frequency of oscillation depends on gravitational acceleration, and might have done a problem calculating the change in frequency or period for an elevation change. But what of another change in gravitational acceleration — what effect does the varying location and thus pull of the moon have on a pendulum clock? And has it been measured? In order to do that measurement, one has to compare a pendulum clock with another that does not depend on the local value of g. The period around 1930 saw a transition from pendulum clocks to quartz oscillators, and that fits the bill, since the quartz crystal, though sensitive to large accelerations, will not have nearly the sensitivity to this kind of change in g. These papers describe the equipment, measurement and the results.
The author of the first paper is Alfred Lee Loomis, a name with which I was not familiar prior to reading these papers, and I’m not sure how that happened. Loomis was a scientist and inventor, and could afford to do these as a hobby, because he was quite rich — he made his fortune in finance in the 1920’s and pretty much exited the stock market before the crash of 1929, so his fortune remained intact and allowed him to buy back on the cheap. He set up a laboratory at his mansion in Tuxedo Park, NY and performed experiments in various fields, including precise time, but also microwave radar. He helped develop that before the defense department was fully behind it, and was appointed to be in charge of the project. The development of radar technology was, of course, a significant factor in winning the war. You can read some more about him here and here.
The devices to be described are the two types of clocks that were used, the crystal oscillator and the Shortt pendulum clocks, and the device used to compare and record timing differences between them, the Loomis Chronograph. I’ll get into the technical aspects next.