According to the tradition, Galileo Galilei discovered the law of the pendulum oscillations by observing those of the incense lamp that in his time was suspended in the center of the aisle of the cathedral of Pisa, and that we see in the image here on the side. To measure the period of oscillations of this pendulum, Galileo used the most accurate clock available at his time: its own heartbeat.
Certainly, the heartbeat can be a good reference to assess periodic regularity such as pendulum oscillations, but today we know that the heart rate clock is far from accurate. In fact, it is even more inaccurate the more one is in good health.
Let’s see how.