1) The phenomenon known as "black holes" occurs when matter is crushed into an infinitely small space, creating a gravitational pull so strong that nothing can escape.

2) The first commercially successful video game was "Pong," released in 1972 by Atari.

3) The musical "Les Misérables" is one of the longest-running shows in the West End and Broadway, with over 13,000 performances.

4) The Industrial Revolution led to significant urbanization, as people migrated from rural areas to cities in search of employment in factories.