Pendulum period is only approximately amplitude-independent for small swings

Evidence

Galileo remarks that the period of the pendulum does not depend on the mass of the bob nor the amplitude of its swing, unless it exceeds 90 degrees. In fact, the period of the pendulum is very nearly but not exactly independent of the amplitude for small amplitudes, but by 90 degrees and more it starts to increase significantly. — Eric J. Heller, Why You Hear What You Hear- An…, 291

Categorization

• QUESTION: Where does the amplitude dependence of the pendulum period become practically measurable, and does it set any limit on real pendulum clock accuracy?
• corroborated: 2 independent passages support this claim — Eric J. Heller, Why You Hear What You Hear- An…, 291
• XREF: connects to: Amplitude does not affect the period of a sinusoidally vibrating object; Nonlinear vibration generates new frequencies absent from the original stimulus; Non-linear and time-variant systems generate frequency components absent from the input — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 358

Broader Connections

• Nonlinear vibration generates new frequencies absent from the original stimulus #expands (0.75)
• Non-linear and time-variant systems generate frequency components absent from the input #expands (0.72) — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 358