6 March 2023
The arch of the Milky Way above the Atacama Desert, Chile. The bright dot near the top of the arch is Jupiter, elongated due to the panoramic projection. The two Magellanic Clouds can be seen to the left. The curved line to the right of the image is the trail of an airplane.
Galaxy is a word that dates to antiquity but one whose primary meaning has shifted over the centuries as our scientific understanding of the universe has grown. Galaxy is from the post-classical, i.e., the fifth century, Latin galaxias, which in turn came from the Hellenistic Greek γαλαξίας (milky circle). Galaxias appears in Anglo-Latin by the twelfth century, and parallel borrowings of the word are found in many present-day European languages.
The Greek γαλαξίας (galaxias), meaning milky circle, is a giveaway to the original meaning. For most of the word’s life, galaxy referred to what we in English call the Milky Way, the band of light that stretches across the night sky (at least where light pollution is minimal). The names come from Greco-Roman myth, a story that is recorded in Pseudo-Erastothenes’s Katasterismoi (Constellations), a text from the first century C.E. but which draws upon earlier sources:
The Galaxy is one of the heavenly circles. It was not possible for the sons of Zeus to share in heavenly honor before one of them had been nursed by Hera. And so, they say that Hermes brought Herakles just after his birth and placed him at Hera’s breast, and that he was nursed by her. When Hera discovered the trick, she pushed Herakles away and the remaining milk was spilled, forming the Galaxy.
(The text was long attributed to the third-century B.C.E. mathematician Erastothenes of Cyrene, but he is no longer thought to be the author, hence the credit to the anonymous Pseudo-Erastothenes.)
Galaxy appears in English by the close of the fourteenth century. John Trevisa’s translation of Bartholomæs Anglicus’s De proprietatibus rerum (On the Properties of Things) uses it, although Trevisa uses the Latin inflections:
De galaxia siue lacceo circulo. Capitulum viii.
Galaxias is a cercle of heuen more faire and briȝt þanne oþir cercles, and passiþ by þe myddel of heuen; and bygynneþ from þe est, and passiþ to þe norþ by þe signes þat hatte Cancer and Capricornus and eft to his owne poynt. And þis cercle hatte “þe milky cercle”, for amonge alle þe cerclis of heuen þat cercle is most briȝt and clere and most notable.
(About the galaxy or milky circle. Chapter 8.
The galaxy is a circle of heaven more fair and bright than other the other circles, and it passes through the middle of heaven; it begins in the east and passes to the north by the signs that are called Cancer and Capricorn and then back to its own point. And this circle is called “the milky circle,” for among all the circles of heaven this circle is the most bright and clear and most notable.)
But at about the same time, Chaucer uses the word in his poem The House of Fame, and there is no doubt that the word had been assimilated into English here:
“Now,” quod he thoo, “cast up thyn yë.
Se yonder, loo, the Galaxie,
Which men clepeth the Milky Wey
For hit is whit (and somme, parfey,
Kallen hyt Watlynge Strete).”(“Now,” he then said, “cast up your eye.
See yonder, lo, the galaxy,
Which men call the Milky Way
For it is white (and some, by my faith,
Call it Watling Street).”)
(Watling Street was a Roman road that ran from Dover to Chester and was a major thoroughfare in medieval England.)
This passage is also one of the earliest known to use the phrase Milky Way. Of course, those in antiquity and the Middle Ages, had no notion that the galaxy was just one of thousands and that the Milky Way was just what an island of stars looked like from our position inside of one. The extension of the word galaxy to encompass other nebulae in the night sky would come by the end of the seventeenth century. From John Fryer’s 1698 A New Account of East-India and Persia:
Steering now by the Crosiers, a South Constellation, taking its Name from the Similitude of that Pastoral Staff; as also supplied by the Magellanian Clouds, in number Two, (averred to be such by those that use this way continually) fixed as the North Star; but to me they seem no other than a Galaxia, caused by the Reflection of the Stars.
We now know, of course, that the Magellanic Clouds are two dwarf, elliptical galaxies that are part of our local group of galaxies, which also includes the spiral galaxies of Andromeda and Triangulum. It wouldn’t be until the twentieth century that astronomers recognized galaxies, including our own Milky Way, for what they are, and galaxy acquired the astronomical meaning that we use today.
Sources:
Chaucer, Geoffrey. “The House of Fame.” The Riverside Chaucer, third edition. Larry D. Benson, ed. Boston: Houghton Mifflin, 1987, 359, lines 935–39.
Condos, Theony. The Katasterismoi of the Pseudo_Eratosthenes. PhD Dissertation. University of Southern California, August 1970, 224–27. ProQuest Dissertations.
Dictionary of Medieval Latin from British Sources, 2013, s.v. galaxias, n. Brepols: Database of Latin Dictionaries.
Fryer, John. A New Account of East-India and Persia. London: R.R. for Ri. Chiswell, 1698, 11. Early English Books Online (EEBO).
Middle English Dictionary, 2019, s.v. galaxie, n.
Oxford English Dictionary, third edition, November 2010, s.v. galaxy, n.; March 2002, s.v. Milky Way, n.
Pseudo-Eratosthenes. Katasterismoi (Constellations), part 2 of 2. Theony Condos, trans. San Francisco: Astronomical Society of the Pacific, Leaflet 467, November 1970, chap. 44, 8. SAO/NASA Astrophysics Data System.
Trevisa, John. On the Properties of Things: John Trevisa’s Translation of Bartholomæs Anglicus De Proprietatibus Rerum, vol. 1 of 3. M.C. Seymour, ed. Oxford: Clarendon Press, 1975, 8.8, 459. London, British Library, MS Additional 27944.
Photo credit: Bruno Gilli, European Southern Observatory (ESO), 2009. Licensed under a Creative Commons Attribution 4.0 International License.