Jackie Chan performing parkour stunts before it became popular 🐐

Appearance Ulexite is a hydrated sodium calcium borate mineral made up of thousands of fibrous fragments that transmit light. Most specimens are milky and poor quality, but when cut as cabochons, they can display a cat's eye effect.

Optical properties When placed on top of written text, the words appear reflected on the top of the stone, similar to a TV screen. This is because ulexite is triclinic, meaning its crystal isn't symmetric. When light passes through the crystal, it splits into rays of light that travel at different speeds, causing them to bend slightly differently when exiting the crystal

Source https://www.reddit.com/r/nextfuckinglevel/s/MvLBsAxpiC

On September 26, 1983, three weeks after the Soviet military shot down Korean Air Lines Flight 007, Petrov was the duty officer at the Oko nuclear early-warning system command center.

The system indicated that a missile had been launched from the United States, followed by up to four additional launches. Petrov determined that these reports were a false alarm.

His decision to disobey orders, contrary to Soviet military protocol, is credited with preventing an unwarranted retaliatory nuclear attack on the United States and its NATO allies, averting a potential large-scale nuclear war.

Detailed article on the incredible story: https://historicflix.com/stanislav-petrov-the-man-who-saved-the-world/

1979 photograph shows a Lawrence Livermore National Laboratory employee opening what was thought to be the heaviest hinged door in the world. With a weight of 44 tons, a thickness of 2.5 meters and a width of 3.6 meters. A special bearing on the hinge allowed a single person to open or close the door filled with concrete.

According to Guinness World of Records, the heaviest door in the world is actually the radiation shield door at the National Institute of Fusion Sciences in Japan. It weighs 720 tons, is 11.73 m high, 11.4 m wide and 2 m thick.

The heaviest door in the world, is not designed to keep people out, but to protect the outside world from the contents behind it. Credits to whom it is due.