There is a pendulum in the Church of Santa Maria degli Angeli in Rome. It is a science exhibit in a church! That seems like a great way to address people’s “religion vs. science” stereotypes and myths. Fr. Timothy Sauppé has done this with a stone bench at his church in Illinois (click here for a discussion of that).
The pendulum is sort of an “art & science” piece. The bob of the pendulum is made to look like the globe of the Earth, held by two fingers of a hand, somewhat in the manner that people hold bowling balls. The pendulum is accompanied by some discussion panels that talk about Galileo Galilei’s work with pendulums and timekeeping.
Why might there be an exhibit like this in this church? Because Santa Maria degli Angeli is home to another timekeeping device — a meridian line for recording passages of the sun across the meridian; that is, across the half-way point between sunrise and sunset, across the noon point. The line can be seen in the photo below (blue arrows), with the pendulum in the background (green arrow). The meridian line was built at the turn of the eighteenth century by Msgr. Francesco Bianchini under Pope Clement XI. You can read all about it in John Heilbron’s new (2022) book, The Incomparable Monsignor: Francesco Bianchini’s world of science, history, and court intrigue.
The discussion panels are interesting. Here is some of the text from them:
The invention of the pendulum marked a turning point in millennia of efforts to improve on the measurement of time. For centuries… the measurement of large quantities of time had been entrusted to increasingly large quantities of something, for example sand in hourglasses. Yet all that was required was to tie a stone to a length of string, fix one end to a plank of wood and push the stone.
As a boy in Pisa, Galilei had noted that oscillations were incredibly regular. One of his early works was to construct a pendulum. Varying the length of the string, Galilei managed to build a pendulum that beat like his heart. If we tie a stone to a piece of string one meter long and set the pendulum in motion, we will find that the stone takes one second to travel from one extremity to another….
And so, starting from his heartbeat — the heart as measure of time — Galilei opened up new horizons for humanity, which would lead to time being measured to billionths of a second….
This was no mean feat. Since the dawn of civilization rotating movements had been considered to belong to the heavenly spheres. The consequence of the discovery that all movements are manifestations of the same entity, that of motion, was that stones had the same status as Stars.
This is obviously written to be sort of flowery and poetic (stones and stars; the heart as a measure of time; movement as manifestation of motion{?}) so I will not be a nit-picking historian of astronomy (or a punctuation fiend) here.
Note that the period of a pendulum is given by the equation T = 2π√(L/g), where L is the length of the pendulum’s string, g is the gravitational field strength or acceleration due to gravity (9.8 meters per second each second), and T is the period or the time required for the pendulum to go through an entire cycle (from one extremity of its swing to the other and back). Thus for a pendulum with a string 1 meter long, T = 2π√(1/9.8). This yields T = 2.007 seconds, so for a 1-meter pendulum to swing from one extremity to the other takes 1.0035 seconds — a single second, approximately.
Not a bad artsy-science-in-the-church exhibit! Let’s see more such exhibits in more churches. Why should science exhibits just be in museums?
