U.S. #5601
2021 55¢ Sun Science – Active Sun
Issue Date: June 18, 2021
First Day City: Greenbelt, MD
Type of Stamp: Commemorative
Printed by: Banknote Corporation of America
Printing Method: Flexographic, Foil Stamping
Format: Pane of 20
Self-Adhesive
Quantity Printed: 18,000,000
Anaxagoras, a philosopher from ancient Greece, was one of the first people in history to offer a scientific explanation of the Sun. He suggested that the Sun wasn't the chariot of a god, but rather a huge ball of flaming metal. Anaxagoras was also the first to suggest that the Moon glows at night because it is reflecting the light from the sun.
After Anaxagoras came Eratosthenes in the 3rd century BC, and then Ptolemy in the 2nd century AD. The latter two began making estimations of how far the Earth was from the Sun. These early astronomers also wondered whether the Sun was the center of the solar system rather than the Earth. However, it wasn't until Nicolaus Copernicus came along in the 16th century that a detailed model was created to support this theory.
Finally, in the 17th century, the telescope was invented. This allowed scientists and philosophers to take the first look at the universe beyond Earth's atmosphere, including the Sun. One of the most famous astronomers to make use of early telescrops were Galileo Galilei. He was the first to theorize that sunspots were located on the surface of the Sun rather than traveling through space as independent objects.
Early astronomers provided the foundation of all solar research. Without them, who knows how many mysteries we would've missed out on solving?