Cat paraphernalia historians say that Sir Isaac Newton got tired of his cat Spithead interrupting his thoughts with all that “Let me out / Let me in!” caterwauling.
So, no doubt using various advanced principles of gravity and inertia, Newton designed the first cat door.
Although he probably didn’t file a patent for it. Cat doors are also known as cat flaps and are extremely popular in the United Kingdom.
Many types of cat doors are available these days and they even come in electronic versions with electromagnetic keys so other animals don’t enter your house. More recently, RFID cat flaps which read a cat’s microchip implant have been introduced in the cat accessory marketplace.
A few crazy cat owners even have cat doors installed inside the home or apartment so their cats can move from room to room even when doors are closed. One wonders how many have cat flaps on the bathroom door.