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

2) The Sydney Opera House, situated in Sydney, Australia, is an iconic architectural masterpiece and a UNESCO World Heritage site. Its unique design, resembling sailboats or shells, has made it one of the most recognized and photographed landmarks in the world.

3) George Clooney is an American actor, filmmaker, and activist. He gained fame for his role in the television series "ER" and has since starred in successful films such as the "Ocean's" trilogy, "Syriana," and "Up in the Air," winning several awards for his performances.

4) The abolition of slavery in the United States was officially proclaimed with the ratification of the 13th Amendment to the Constitution in 1865.