Two Greek goddesses huddle close together in the sky this evening: Selene and Aphrodite – the Moon and Venus. They’re in good view well before night falls, shining through the twilight.

Aphrodite was the goddess of love and beauty. She was identified with the brilliant morning and evening star. We know them today by her Roman name, Venus. Selene was one of several Moon goddesses, but the only one considered to be the human form of the Moon itself.

Selene’s name has been applied to a lot more than just the Moon. Among other things, it’s the name of a mineral – selenite – and an element – selenium.

Selenite is a crystal form of the mineral gypsum. It’s translucent, so it was sometimes used as window panes. There are several possible explanations for the name. One says it might have been bestowed because the light that passed through the windows looked milky white – like the light of a bright Moon.

Selenite doesn’t contain any selenium, though. The only thing the mineral and the element have in common is the name. Selenium was discovered in the early 1800s. It’s rare – usually found mixed in with the ores of various metals. Its appearance and properties were similar to those of another recently discovered element – “tellurium” – a word that means “Earth.” So it made sense to name the new one for our satellite world – the Moon.

Tomorrow: a different seasonal dividing line.

Script by Damond Benningfield