In Brief
The most famous constellations (other than perhaps Orion and the Big Dipper) are the Zodiac constellations. These are twelve constellations that lie along the ecliptic, which is the apparent path the Sun makes through the “heavens” over the course of a year. Since the Moon and planets follow paths that are within a few degrees […]

The most famous constellations (other than perhaps Orion and the Big Dipper) are the Zodiac constellations. These are twelve constellations that lie along the ecliptic, which is the apparent path the Sun makes through the “heavens” over the course of a year. Since the Moon and planets follow paths that are within a few degrees of the orbital plane of the Earth, they too appear to travel through the constellations of the Zodiac. For this reason, they are not just constellations, but rather astrological signs. According to astrology, the Zodiac constellation that the Sun was in at the time of your birth influences your life, hence the proverbial pick up line “hey, baby, what’s your sign?”

Sidney Hall Uranias Mirror aurus
Ophiuchus the Serpent Bearer. Image Credit: Wikimedia Commons.

Much of early astronomy stems from astrology and its effort to calculate the ways in which the Sun, Moon, and planets are “able to” affect our lives. Since the Sun and Moon can be used to determine the seasons and cycles of nature, it was reasonable to see if planets also play a role. Given the ease with which humans assume a pattern when there is none, astrology rose to importance, and many prominent early astronomers were also astrologers. Astrology is still used by many today, despite the fact numerous studies have shown that the predictions of astrology are no different than random chance, such as the famous experiment by Shawn Carlson published in Nature back in the 1980s.

Difference between astronomical and astrological times.
The difference between astronomical and astrological times.

The Zodiac constellations used today were first established more than 2,000 years ago, and since then the precession of the Earth has shifted the path of the ecliptic. As a result, the time when the Sun passes through each constellation is about a month behind the designated Zodiac times. There are also now 13 Zodiac constellations, as defined by the path of the Sun. After leaving Scorpio (Scorpius to astronomers) and before entering Sagittarius, it passes through a constellation known as Ophiuchus.

So if someone asks you about your sign, try saying Ophiuchus and see how they react.

 

Provided by Brian Koberlein at One Universe at a Time.