How to Science [Part 3: Experiments]

Marin Mersenne used pendulums as timekeeping references to measure string vibration frequencies by having one person count string vibrations while another counts pendulum swings.

Mersenne solved the counting problem by building scale models—creating longer and longer vibrating strings until vibrations slowed enough to count directly, sometimes exceeding 100 feet.

Modern experimenters can use high-speed cameras to slow down string vibrations for counting, achieving the same effect as Mersenne’s physical scaling through temporal rather than spatial transformation.

Richard Feynman articulated the scientific process for discovering new laws: “First we guess it. Then we compute the consequences of the guess to see what it would imply. Then we compare those computation results to nature, to experiment, to see if it works.”

To make educated guesses about the length-frequency relationship, the video demonstrates collecting observations first—measuring frequencies at different string lengths before proposing mathematical relationships.

Experimental observations reveal that string frequency and length have an inverse relationship: at 40cm the string vibrates at 122 Hz, at 80cm (double length) it vibrates at 65 Hz, and at 20cm (half length) it vibrates at 245 Hz.

Feynman’s method requires guesses to be “specific enough to produce exact predictions”—vague qualitative statements don’t constitute testable hypotheses.

The video establishes an experimental test: using a string at 3,200g tension and 40cm length (174 Hz baseline), predict frequencies at 80cm, 50cm, and 20cm to validate the length-frequency hypothesis.