Popular legend holds that Isaac Newton invented not only calculus, but also the cat door. Unfortunately, this colorful legend is not supported by good evidence. Cats have been domesticated for thousands of years, with the oldest known domestic cat possibly dating back to Cyprus 9,500 years ago. Textual evidence for cat doors can be found Chaucer in The Miller’s Tale, centuries before Newton, and there’s no evidence that the natural philosopher even owned a cat. Nevertheless, the myth has been persistent and varied, initially being used to cut the scholar down to size, and later on used to demonstrate his brilliance.