Explaining the zodiac in astrology

The zodiac is determined by the position of the Sun in the sky relative to 12 constellations and is closely linked to astrology.

The 12 zodiac signs are associated with the movement of the Earth in the sky. Photo: Wordpress.

The zodiac, or 12 signs listed in horoscopes, are tied to the movement of the Earth across the sky. Because the Earth rotates around the Sun in a flat plane, we see the Sun appear and move in front of different constellations throughout the year, according to Earth Sky.

Just as the Moon appears in a slightly different position in the sky each night, the position of the Sun relative to distant background stars shifts eastward from day to day. For example, if the Sun is in the constellation Gemini one month, next month it will be in the constellation Cancer.

Specific dates are listed in Western horoscopes to indicate when the Sun is in a particular zodiac sign. For example, March 21 to April 19 is Aries. Now, the zodiac sign you were born in does not necessarily match the name of the constellation the Sun is passing through.

To understand why constellations no longer match their corresponding zodiac signs, we need to know more about how the Earth moves.

The Earth spins, and its North Pole doesn’t always point in the same direction. Like a top, the Earth wobbles, causing the North Pole to circle the celestial sphere. This wobble happens slowly, every 26,000 years, so the Earth doesn’t actually complete one orbit in a year. After about 2,000 years, the Sun will be in a completely different constellation for the same amount of time.

On the June solstice 2,000 years ago, the Sun was roughly halfway between Gemini and Cancer. But on the 2016 solstice, the Sun was halfway between Gemini and Taurus. In 4609, the Sun will move out of Taurus and into Aries on the summer solstice.

The signs of the zodiac that correspond to the constellations through which the Sun passes were determined 2,000 years ago. But in the mid-21st century, the slow wobble of the Earth's rotational axis caused the solstices and equinoxes to shift about 30 degrees westward relative to the constellations. Currently, the signs of the zodiac and the constellations are about a month apart. In about 2,000 years, they will be about two months apart.

The constellations of the zodiac are not all the same size and shape. Most of them appear in ancient Babylonian texts and were introduced by Ptolemy, a Greek astronomer who lived in the 2nd century.

In 1930, the International Astronomical Union demarcated the modern constellations with all 13 constellations lying along the path of the Sun. The constellation not listed in Western horoscopes is Ophiuchus, which lies between Sagittarius and Scorpio./.

According to VNE