1924:Astronomer Edwin Hubble announces his discovery of the Andromeda Galaxy, indicating that the Milky Way is not the only galaxy in the universe. Hubble used a 100-inch telescope at the Mount Wilson Observatory in Pasadena, Calif., to see Andromeda, located more than 2 million light years away from Earth. Hubble's discovery also proves that the universe is much larger than was previously thought.
1927: The Tokyo Underground Railway opens the first section of subway in Asia, between Ueno and Asakusa (now known as the Ginza Line) in Tokyo. The line became so popular back then that passengers happily waited two hours for a five minutes trip on the train. The Tokyo subway was founded by Japanese businessman Noritsugu Hayakawa after he was inspired by a ride on the London Undergound. The Tokyo subway system is currently the busiest and most extensive underground mass transit system in the world, with 282 stations and a daily ridership of 8.7 million people.
1936: Employees at the General Motors Fisher Body Plant No. 1 in Flint, Mich., begin one of the first sit-down strikes in U.S. history, demanding recognition of the United Auto Workers union and the acceptance of a list of pro-worker reforms. The strike lasts 44 days.