<!–>
–><!–>
[–><!–>Whether you care about horoscopes or not, you probably know your zodiac sign. You’ve probably known it for most of your life.–><!–>
–><!–>
[–><!–>
–><!–>
[–><!–>
–><!–>
–><!–>
[–><!–>
–><!–>
–>1. Earth’s wobble<!–>
–><!–>
[–><!–>The Earth wobbles like a top. A spinning top starts to wobble soon after it is set into motion. The Earth does the same thing, only more slowly.–><!–>
–><!–>
[–><!–>It takes 26,000 years for the North pole to trace out a complete circle in the sky, pointing at different stars along the way. Scientists call this wobbling motion axial precession.–><!–>
–><!–>
–><!–>
[–><!–>
–><!–>
–><!–>
[–><!–>
–><!–>
[–><!–>Take the spring equinox, usually around March 20, the first day of spring in the Northern hemisphere (and the start of the zodiac calendar in Western astrology).–><!–>
–><!–>
–><!–>
[–><!–>This shift in our view of the stars was discovered by Hipparchus over 2,000 years ago. Since you can’t see stars during the day, he waited for a lunar eclipse — when the moon is directly opposite the sun — and used the moon’s position to work out where the sun was.–><!–>
–><!–>
[–><!–>
–><!–>
[–><!–>Today, Western astrology uses the tropical zodiac system, which is based on the positions of the stars more or less as they would have appeared to Hipparchus, and not as they appear today.–><!–>
–><!–>
[–><!–>
–><!–>
[–><!–>In contrast, the Indian system of astrology uses the sidereal zodiac, which accounts for Earth’s wobble and aligns zodiac signs to the stars.–><!–>
–><!–>
[–><!–>
–><!–>
[–><!–>
–><!–>
–>2. Constellations differ in size<!–>
–><!–>
[–><!–>The zodiac signs were created around 2,500 years ago by the Babylonians.–><!–>
–><!–>
[–><!–>Their star catalogs listed at least 17 zodiac constellations. But they eventually simplified these into the 12 zodiac constellations we know today, each 30 degrees wide, as if slicing the sky into 12 equal slices.–><!–>
–><!–>
[–><!–>But constellations aren’t really the same size. In 1928, astronomers divided the sky into 88 officially recognized constellations, each one shaped like its own puzzle piece.–><!–>
–><!–>
<!–>Official constellations along the sun’s annual path–>
<!–>
–><!–>
[–><!–>“They are not nice equal pieces. They’re like jagged shapes that are not symmetric in any way,” said Stacy Palen, emeritus professor at Weber State University.–><!–>
–><!–>
[–><!–>
–><!–>
[–><!–>
–><!–>
–>3. Ophiuchus<!–>
–><!–>
[–><!–>Ophiuchus is the 13th constellation along the sun’s path, according to astronomers. (It even has its own emoji: ⛎.) Ophiuchus means “serpent bearer” in Ancient Greek, and is usually depicted as a man holding a snake. If you squint, you can kind of see why.–><!–>
–><!–>
–><!–>
[–><!–>
–><!–>
[–><!–>We don’t really know why the Babylonians left out Ophiuchus from their zodiac signs. They may have originally had a different name for it. But historians believe that when Babylonians simplified their zodiac system, they wanted the 12 zodiac signs to match the 12 months of their calendar. Ophiuchus didn’t make the cut.–><!–>
–><!–>
–>A ‘shape-shifter’<!–>
–><!–>
[–><!–>Astronomy and astrology have little in common today, and there’s no scientific basis to the idea that the movements of the stars and planets influence our future or our personalities. But the two disciplines started out as the same thing thousands of years ago.–><!–>
–><!–>
[–><!–>
–><!–>
[–><!–>
–><!–>
[–><!–>Even by the 17th century, many astronomers were also practising astrologers. Johannes Kepler, who discovered how planets move in ellipses, likely learned astrology at university, and created horoscopes for friends and patrons. Galileo practiced astrology and sold horoscopes on the side.–><!–>
–><!–>
[–><!–>“Their side hustle was to cast horoscopes for their rich patrons because that paid the bills,” said Tyler Nordgren, an astronomer and author.–><!–>
–><!–>
[–><!–>
–><!–>
[–><!–>
–><!–>
[–><!–>Today, we understand the laws governing the motions of planets and stars well enough to send spacecraft to distant worlds, detect gravitational waves, and take pictures of a black hole. At the same time, over a quarter of Americans believe that the positions of the stars and planets can affect their lives.–><!–>
–><!–>
[–><!–>So why has belief in astrology endured, while other methods of divination such as ornithomancy (finding omens in the behavior of birds) or tyromancy (fortune-telling with a block of cheese) have drifted into obscurity?–><!–>
–><!–>
[–><!–>
–><!–>
–><!–>
[–><!–>
–>
How we found your sign
<!–>
[–><!–>Though the astrological zodiac calendar is well known, there are small ways ours may differ from other sources. To calculate your astrological zodiac sign, we divided the sun’s annual path across the sky (known as the ecliptic) into 12 equal divisions of 30 degrees, beginning with the March equinox, which marks the beginning of Aries. This is the tropical zodiac system, in which zodiac signs are aligned to the seasons.–><!–>
–><!–>
[–><!–>To calculate the astronomical zodiac constellation behind the sun, we used the Astronomy Engine software library to locate the sun on every day of the year and determine the astronomical constellation behind it.–><!–>
–><!–>
[–><!–>We based our zodiac calculations on the current year, and on the position of the sun at noon UTC every day. A more accurate calculation of your sign would involve knowing the exact time and year of your birth, and as a result our calculations may be off by a day or so. This primarily affects people whose birthdays are on the cusp between two signs, or between two constellations.–><!–>
–><!–>
[–><!–>To create the 3D illustrations of the stars, we used a repository of celestial data for the 88 official constellations, and oriented these constellations based on Earth’s view of the stars on a given date.–><!–>
–><!–>
[–><!–>The astronomical calculations account for precession (the slow wobble in Earth’s axis of rotation), nutation (a slight wiggle in the tilt of Earth’s axis), and the gradual drift of Earth’s elliptical orbit.–><!–>
–><!–>
[–><!–>Our star maps do not account for the movement of individual stars through space, relative to each other, known as proper motion. This movement is typically so slow as to be minimal over centuries, but the positions of some of the stars in the Northern sky during the last ice age may be in slightly different locations than shown.–><!–>
–><!–>
[–><!–>In our visualizations, we used the familiar names Scorpio and Capricorn instead of the official names for those constellations: Scorpius and Capricornus. The seasons we describe are for the Northern hemisphere. The Earth’s orbit around the sun is actually counterclockwise when viewed from above; we show it orbiting clockwise for illustrative purposes. The Earth and the sun are not to scale.–><!–>
–>
<!–>
[!–><!–>
–> <!–>
–>
