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) The process of photosynthesis, performed by plants, algae, and some bacteria, is responsible for producing the oxygen we breathe.

3) The coldest known temperature in the universe was achieved in a laboratory in 2019, reaching a fraction of a degree above absolute zero (-273.15 degrees Celsius).

4) The Appalachian Mountains, running along the eastern coast of the United States, are one of the oldest mountain ranges in the world.