1) The first successful mass-produced personal computer, the IBM PC, was introduced in 1981 and played a significant role in popularizing the use of computers in homes and offices.

2) In Norse mythology, Ragnarok is a cataclysmic event that signifies the end of the world. It involves a series of apocalyptic battles and natural disasters, leading to the destruction of the gods and the world as it is known. From the ashes, a new world and a new generation of gods emerge.

3) The Civil Rights Act of 1964 in the United States outlawed discrimination based on race, color, religion, sex, or national origin.

4) The musical "Hamilton" has won numerous awards, including 11 Tony Awards and the Pulitzer Prize for Drama.