The 12 signs of the zodiac, as mentioned in a horoscope, are inextricably linked to the Earth’s motion through the sky. The constellations that point out the path that the sun appears to take during the year provide us with these indicators. Dates in a horoscope may appear to match to when the sun travels through each constellation. They don’t always agree, though, because astrology and astronomy are two separate systems. Plus, a closer look at the Earth, the sun, and the stars reveals that the zodiac is more complicated than you might think!
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The sun’s motion through the constellations
The sun appears to pass in front of numerous constellations as Earth revolves the sun. The sun’s position in relation to distant background stars drifts in an easterly direction from day to day, much how the moon appears in a little different spot in the sky each night. It’s not as if the sun isn’t moving. Its movement is totally fictitious, owing to Earth’s own rotation around our star.
The sun appears to be in front of, or “in,” different constellations throughout the year. The sun appears in Gemini one month and Cancer the next. The dates in the newspaper’s horoscope indicate when the sun is in a specific astrological sign. For example, the sign Aries is represented by the period between March 21 and April 19. However, your astrological sign does not always indicate which constellation the sun was in when you were born.
Why the zodiac constellations don’t always align with astrological signs
We need to know a little bit more about how the Earth moves to explain why constellations no longer coincide with their respective signs. We must also discuss how we measure time.
Time is a fiendishly difficult concept to grasp, especially if we insist on using the sun and stars as our point of reference. For better or worse, our calendar is based on the seasons. The day the sun appears at its most northerly point in the sky is June 21 – the approximate date of the summer solstice north of the equator and the winter solstice south of the equator. The North Pole is most inclined towards the sun at the June solstice.
The fact that the North Pole does not always point in the same direction as the background stars complicates things. Our world whirls around like a top. The Earth, like a top, wobbles! The North Pole traces a circle on the celestial sphere due to the Earth’s wobble. The wobbling is slow; it takes 26,000 years to complete one rotation. However, as time passes, the effect becomes more pronounced.
The direction of the Earth’s axis drifts somewhat throughout the course of one orbit around the sun. This means that the location of the solstice along our orbit changes by a very modest amount. The solstice occurs around 20 minutes before one full trip in front of the background stars!
Our drifting calendars
Because we base our calendar on the solstices and equinoxes (and astrologers on the signs), the Earth does not complete an orbit in a single year. The tropical or seasonal year is really a fraction of a second shorter than one full orbit (sidereal year). This means that the sun’s position relative to the stars on any given day say, June 21 wanders a very small amount each year.
However, after 2,000 years, the sun will be in a completely other constellation!
The sun was nearly halfway between Gemini and Cancer on the June solstice 2,000 years ago. The sun was between Gemini and Taurus on the June solstice fourteen years ago. In the year 4609, the June solstice point will move from Taurus to Aries, leaving Taurus behind.
When humanity formed the present Western zodiac some 2,000 years ago, the signs were roughly aligned with their respective constellations. However, the steady wobble of the Earth’s axis has led the solstice and equinox locations to shift around 30 degrees westward relative to the constellations in the intervening ages. Signs and constellations are currently around one calendar month off. They’ll be approximately two months away in another two thousand years or so.
Modern constellations and the zodiac
To make matters even more complicated, unlike astrological signs, constellations are not all the same size and shape. For the most part, the stars that make up a constellation are not physically related. They’re simply based on patterns that our forefathers noticed when they looked up at the sky, trying to make sense of it all.
The International Astronomical Union (IAU) established the constellations as sky regions, not only star patterns, in 1930. They established the boundaries we use today as a result of this. These current constellations are based on those introduced in the second century CE by Greek astronomer Ptolemy. He, in turn, took them from Babylonian scriptures dating back thousands of years. Throughout history, several societies have seen patterns in the sky that are unique to them. Some constellations are shared by many cultures (Orion is a good example), but not all.
There are actually 13 constellations that lay along the path of the sun, based on the present borders. Ophiuchus, the Serpent Bearer, sits between Sagittarius and Scorpius and is not mentioned in any horoscope. The signs stay stable in relation to the solstices and equinoxes, while the solstices and equinoxes shift westward in relation to the constellations or backdrop stars.
While the zodiac isn’t a fantastic predictor of love, fortune, or health, it is an excellent tool for better understanding the sun’s, Earth’s, and even the cultures that have come and gone on our small planet. The zodiac signs, which are drawn from constellations that line the path of the sun in the sky, trace Earth’s orbit and wobble and serve as a reminder of astronomy’s humble beginnings.
Bottom line: While you may identify the term zodiac with astrology, it also has a prestigious role in astronomy. The 12 constellations that make up the zodiac are located along the sun’s annual motion across the sky.
How did the Zodiac signs come to be?
Babylonian astronomers split the ecliptic into 12 equal “signs” at the end of the 5th century BC, analogous to 12 schematic months of 30 days each. The first known celestial coordinate system was created when each sign contained 30 degrees of celestial longitude. According to contemporary astronomical estimates, the zodiac was first used between 409 and 398 BC, during Persian dominance, and most likely within a few years of 401 BC. Unlike modern astrologers, who place the beginning of the sign of Aries at the position of the Sun at the Northern Hemisphere’s vernal equinox (March equinox), Babylonian astronomers fixed the zodiac in relation to stars, placing the beginning of Cancer at the “Rear Twin Star” ( Geminorum) and the beginning of Aquarius at the “Rear Star of the Goat-Fish” ( Capricorni).
Since Babylonian times, the time of year when the Sun is in a certain constellation has altered due to equinox precession; the point of March equinox has moved from Aries to Pisces.
They formed an appropriate basis of reference for formulating predictions about a planet’s longitude because the divide was made into equal arcs of 30 each. However, Babylonian observational measurement techniques were still in the early stages of development. They used a group of “normal stars” near the ecliptic (9 degrees latitude) as observational reference points to help place a planet within the ecliptic coordinate system.
A planet’s location in Babylonian astrological journals was usually stated in terms of a zodiac sign alone, rather than particular degrees within a sign. When degrees of longitude were given, they were stated in relation to the 30 of the zodiacal sign, rather than the continuous 360 ecliptic. The positions of prominent astronomical phenomena were estimated in sexagesimal fractions of a degree in astronomical ephemerides (equivalent to minutes and seconds of arc). The daily locations of a planet were less important in daily ephemerides than the astrologically significant times when the planet moved from one zodiac sign to the next.
What is the origin of the zodiac signs?
The 12 zodiac signs Aries (March 21-April 19), Taurus (April 20-May 20), Gemini (May 21-June 20), Cancer (June 21-July 22), Leo (July 23-Aug. 22), Virgo (Aug. 23-Sept. 22), Libra (Sept. 23-Oct. 22), Scorpio (Oct. 23-Nov. 21), Sagittarius (Nov. 22-De These Western, or tropical, zodiac signs were named after constellations and paired with dates based on their apparent relationship to the sun’s position in the sky.
By 1500 BC, the Babylonians had divided the zodiac into 12 equal signs, with constellation names that were similar to those we know today, such as The Great Twins, The Lion, and The Scales, and these were later adopted into Greek divination. These 12 signs were popularized by the astronomer Ptolemy, author of the Tetrabiblos, which became a key work in the history of Western astrology.
“Ptolemy codified the idea that there were 12 signs of the zodiac that were 30 wide and that the sun travelled through these signs on a regular basis throughout the year,” says Odenwald. According to the Oxford English Dictionary, the word “zodiac” is derived from a Greek term meaning “sculpted animal form,” and the sequence in which the signs are normally enumerated is also derived from that period.
Who created the signs of the zodiac?
The constellations that represent the 12 astrological signs each take up a quarter of this belt in principle, although they aren’t properly proportionate in shape or size in reality. They’ve also moved around since the Babylonians initially recorded the zodiac sign system around 450 BCE.
Who developed the 12 signs of the zodiac?
The 12 zodiac signs, one of the earliest notions of astrology, were devised by the Babylonians around 1894 BC. The Babylonians lived at Babylon, which is roughly where modern-day Iraq is located. Babylon was one of the most prominent ancient Mesopotamian towns.