You probably know your zodiac sign, based on your birthday. If you were born on March 1, you're a Pisces, the Fish. But what's up with that? Where did the 12, seemingly arbitrary signs of the Western zodiac come from, anyway? Turns out, there's not a simple answer. There's astrology, which deals with your horoscope, which might tell you that as a Pisces, you're dreamy and sensitive. And then there's astronomy, for which the zodiac means something else entirely. Or rather, two something elses.
Early Babylonian astronomers seem to have been the first to divide the sky into 12 30-degree sections along the apparent path of the sun through the sky for the course of one year.
This circular progression correlates with a solar year that starts on the spring equinox, and which the Greeks and Romans later translated into the familiar sequence of 12 zodiac signs for which we still use the Latin names: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius, and Pisces.
The word "zodiac" derives from a Greek phrase that meant "circle of animals," though not all the signs represent animals; twin boys, a young woman, a set of scales, a centaur archer, and a water-bearer also show up in the sequence.
Aries the Ram is considered the first sign of the zodiac. When the sun passes into the Aries section of the zodiac, that's the official first day of spring, on or around March 21.
It takes about a month for the sun to pass through Aries. At 31 degrees, the sun officially enters the next sign, Taurus, and so on, coming full-circle to wind up in Pisces at the end of the solar year. At its most basic, then, the zodiac is a coordinate system, helping us track celestial bodies in space and time relative to this path of the sun.
Here in the northern hemisphere each of these 12 signs can also be found as constellations in our night sky, though not all at the same time.
Leo the Lion is easily located this time of year by tracing an imaginary line downward from the bottom of the cup of the Big Dipper to a bright, C-shaped set of stars, including the alpha star Regulus, which makes up the lion's head.
Taurus and Gemini are also very visible right now in the vicinity of Orion. Other sign constellations are less easy to pick out. I'm not sure I've ever actually found my own sign, Pisces, which is so faint it's not even depicted on some star charts.
But here's where it gets tricky: Although they both denote something in the celestial sphere, a zodiac sign is not the same as the constellation that shares its name.
When this zodiac thing was first worked out, the constellations did line up, roughly, with the associated 30-degree segments of the same name.
The sun entered Aries on the first day of spring, and the constellation Aries was the stellar backdrop. But it no longer works this way, thanks to precession, by which rotational shifts in the earth's axis very slowly change our orientation relative to the stars we look out upon.
Over several millennia, the constellations have thus "shifted" with respect to where they were first aligned by the Greeks. Now on the spring equinox the zodiac sign Aries is actually a coordinate in the neighborhood of the constellation Pisces.
The 2,160-year period of time in which the sun starts the solar year in the constellation Pisces is referred to as the Age of Pisces. (I take this to heart. Fellow Pisceans, this is our time to shine!)
Counter-culture types from the 1960s and 70s lauded the "dawning of the Age of Aquarius," but that age won't technically begin until the year 2,597, according to calculations made in accordance with the International Astronomical Union (IAU).
Other calculations differ wildly, all being relative, of course, to when the Age of Pisces began — a disputed date in itself. And New Agers might say that it's all a matter of attitude anyway, not astronomy.
Aries is a tiny constellation made up of three stars, for example. Virgo is a sprawling constellation that takes up way more than 30 degrees of space. The IAU has set official boundaries for each one, but it's still a challenge trying to make sense of the two associated — but no longer correlative — systems: one marking celestial coordinates and the other labeling sets of stars.
Despite these complications, I encourage you to learn to pick out the constellation of your zodiac sign, so that at the very least the next time someone asks, "Hey baby, what's your sign?" you can actually show them. It's a good party trick. (Unless you're a Pisces like me, in which case, good luck with that and let me know if you find it.)
Making a personal connection with the stars overhead is a simple and easy way to extend your relationship with the natural world, as well as with your ancestors who, thousands of years ago, looked up into a night sky swarming with stars and out of that chaos created a parade led by animals that still marches round us today.
Kristen Lindquist is an amateur naturalist and published poet who lives in her hometown of Camden.