It seems scientist Isaac Newton was working on some experiments while at the University of Cambridge. However, as cats are wont to do, his kept scratching at the door, wanting to be in – or out – or in – or out, interrupting his thoughts and progress.
Newton’s solution was to call the campus carpenter to cut two holes in the door to his quarters, one for his mother cat and the other for her kittens. Who would’ve thought the brilliant scientist who realized the existence of gravity would also invent the cat door?
“How Stuff Works” not only mentions the story, but says tourists can see the door and the two holes cut into it for the convenience of Newton’s cats to this day.