Domestic-cat pupils change area by about 135-fold, and a reflective tapetum sends transmitted light back through the retina. The pupil/ecology link is a comparative correlation; simple multilayer equations illustrate tapetal optics but do not supply cat-specific reflectance or sensitivity values.
A 2023 Current Biology experiment showed that excised cat larynges can produce purr-like low-frequency oscillations under airflow without neural input. Connective-tissue pads are a plausible contributing mechanism, not a settled complete account; frequency overlap does not establish bone healing in cats.
Cats use the dorsal surface of the tongue tip to entrain a liquid column, then close the jaw before gravity and pinch-off remove it. Reis and colleagues modelled the timing with inertia, gravity, a Froude number, and the tongue’s travel geometry. The relevant domestic-cat parameter is a modified Froude number near 0.4—not the simple Froude number near one.
Marc-Antoine Fardin won the 2017 Ig Nobel Prize for a playful application of rheological language to cats. The Deborah number De = τ/T is a standard timescale ratio for materials; assigning a cat a relaxation time is an analogy, not a rigorous material classification.
A cat dropped upside-down rotates 180° and lands on its feet, despite having zero angular momentum throughout. This is not a trick and not a violation of physics. The explanation took physicists from 1894 to 1993 to fully work out, and the answer — a geometric phase arising from the holonomy of a fiber bundle — is the same mathematics that governs the Berry phase in quantum mechanics and the Aharonov-Bohm effect in electrodynamics. We adopted two strays this year. They fall beautifully.