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TIL Rubbing your eyes increases the pressure within the eyeball and this pressure activates ganglion cells in the retina in the same way as light does. Your brain doesn’t know the difference and so interprets the activation as though you were seeing light from the world outside.

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8aD7P TIL a soldier in Napoleon's army invented "night writing" in the early 1800s so soldiers could communicate safely in the dark. It was then adapted and perfected by Louis Braille to give us the tactile writing system known as "Braille", which is used by vision impaired persons worldwide.
OLnL TIL St. Jude Children’s Research Hospital was founded in 1962 by comedian Danny Thomas. He promised St. Jude that if he made him successful, he would one day build him a shrine. The hospital has since become a leader in the study and treatment of children’s cancer. St. Jude got his shrine.
1alO7 TIL A scientist embedded LEDs in a prop prosthetic arm to demonstrate an electric eel attack. Each flash in the video represents the firing of the nerves in a potential predator. In each of the volleys at 600 volts, there are 200 pulses per second, a very good rate for causing pain.
gMEKy TIL of Cher Ami, a World War I homing pigeon who saved the lives of 194 soldiers by delivering a plea for help despite being shot through the breast, blinded in one eye, and having a leg hanging only by a tendon. She was awarded the Croix de Guerre Medal and a small wooden leg for her service.
kJd6d TIL that the current solicitor general of the U.S., which represents the federal govt. before the Supreme Court, was Miss Idaho before her legal career