WOTD - Cat flap
Cat flap - Wikipedia, the free encyclopedia
A cat flap (British English) or kitty door (American English) is a hinged flap set into a door, wall or window to allow cats to enter and exit a house on their own without needing a human to open the door. Doggie doors similarly exist for dogs.
Cat flaps are popular in some countries, particularly the United Kingdom where it is believed that about 90% of cats have access to the outdoors.
The cat flap was invented by Sir Isaac Newton when he was conducting experiments on light and prisms in his attic. His carefully controlled lighting conditions could be maintained and allow access for his cat. The pendulum effect of the cat flap also demonstrates Newton’s Third law of motion. [..read more.. ]
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