The Secret History of Cosmic Buzzwords You Didn’t Know

As the human mind and human senses reach ever-farther out into space, we keep encountering new things that require new objects that require new names. Some of these have ancient origins; some (like “black hole”) have effectively crossed over into modern pop culture. But even those of us who, like myself, use them all the time rarely stop to think about where the terms come from.

An interacting pair of galaxies, called Arp 273. Until a century ago such objects were called nebulas (Latin for "fog" or "mist").

An interacting pair of galaxies, called Arp 273. Until a century ago such objects were called nebulas (Latin for “fog” or “mist”). Credit: NASA/ESA/Hubble.

Today I’m taking a step back, looking at the people and stories behind the cosmic buzzwords. For those of you who enjoy reading about the universe–or those of you who are encountering the buzzwords through the popular Cosmostelevision show–this is a chance to join me in a walk through the history of science.

Astronomy. Let’s start all the way at the beginning. Honestly, I never thought much about the meaning of “astronomy,” assuming it simply means “study of the stars.” Close, but no cigar. It comes from the Greek words astron and nomos, which literally mean “law of the stars” or “custom of the stars.” The distinction is significant. Originally the purpose of astronomy was not to understand the construction of the universe, but to make sense of the ways that the stars affected life here on Earth. Astrology was not recognized as a separate term until the 14th century; until then, astronomy and astrology were one and the same.

Planet. This is another ancient Greek word, meaning “wanderer” (planetes). The obvious reason: The planets wander through the sky, unlike the stars which remain fixed in place (at least on human timescales). Modern astronomers have developed an elaborate set of naming conventions for new asteroids, moon, and features on planets. The system, policed by the International Astronomical Union, weirdly does not have a convention for the naming of new planets.

Galaxy. The name is derived from gala, ancient Greek for milk, because of the milky appearance of the Milky Way in the sky. (Milk sugar is called galactose–same reason.) Tthe first use of the term “Milky Way” came much later, in Chaucer’s 14th-century story The House of Fame: “See yonder, lo, the Galaxyë Which men clepeth the Milky Wey, For hit is whyt.” And the concept that the universe is full of other galaxies was not well accepted until 1929!

Nova. The word just means “new” in Latin, and derives from the book De Stella Nova (The New Star), written by the pioneering astronomer Johannes Kepler, in which he described a star that suddenly appeared in 1572 (now understood not as a new star but as a dying, exploding one, called Tycho’s Supernova).

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