October 23

1920 - Meteorologist Ted Fujita is born. He is most well known for his study of severe storms, and invention of the "Fujita scale," which measures tornadoes.
1977 - Paleontologist Elso S. Barghoorn announces the discovery of Pre-Cambian spherical one-celled algae microfossils.

• Estimated to be 3.4 billion years old, they would be Earth's earliest-discovered life forms.
• Being from the Precambrian period, these microfossils help to begin the change of Earth's primoidal, reducing atmosphere to the oxygenated one we have today.
  

1893 - Birth of Estonian astronomer Ernst Öpik, who first posited the existence of the Oort Cloud.