Dear Tom,
Why is the Earth’s moon just called “the moon,” but the moons of other planets in the Solar System have specific names?
—Donna Hirsch, Worth, Ill.
Dear Donna,
The Earth’s moon is called “the moon” because it was so named well before the moons of other planets were discovered. That all changed in 1610 when Italian astronomer Galileo Galilei discovered the four largest moons of the planet Jupiter and, later in the 1600s, other European astronomers discovered five moons surrounding Saturn. Since then, many additional moons have been discovered orbiting around Jupiter and Saturn, as well as around other planets of the solar system.
“Moon” is the name of the Earth’s only satellite and it is not just a moon: It is “the moon.”