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.
What are the zodiac signs and how do they work?
Early astronomers witnessed the Sun passing through the Zodiac signs in a year’s time, spending roughly a month in each. As a result, they determined that each constellation covers 30 degrees of the ecliptic.
However, due to a phenomenon known as precession, the positions of the constellations we see now have changed.
The zero point of the Zodiac used to designate the beginning day of spring in the Northern Hemisphere. The vernal equinox happens when the ecliptic and celestial equator collide, according to astronomers.
The zero point existed in Aries around 600 BCE, and it was known as the “first point of Aries.” (See Figure 1). The constellation Aries covered the first 30 degrees of the ecliptic; Taurus covered the next 30 degrees; Gemini covered the next 60 degrees; and so on for all twelve constellations of the Zodiac.
The Earth wobbles around its axis in a 25,800-year cycle, which ancient astrologers were unaware of. The gravitational attraction of the Moon on Earth’s equatorial bulge causes this wobble, which is known as precession.
This wobble has led the junction point between the celestial equator and the ecliptic to migrate west along the ecliptic by 36 degrees, or nearly one-tenth of the way around, over the past two and a half millennia. This indicates that, in relation to the stars beyond, the signs have moved a tenth of the way across the sky to the west, or about a month.
For example, persons born between March 21 and April 19 are considered Aries. During much of that time, the Sun was no longer in the constellation of Aries. The Sun is actually in the constellation of Pisces from March 11 to April 18! (See Illustration 2) See also Figure 3, which depicts the equinox precession from 600 BCE to 2600 CE.
The dates when the Sun is truly within the astronomical constellations of the Zodiac, as defined by contemporary constellation borders and corrected for precession, are listed in the table below (these dates can vary a day from year to year).
When precession is taken into consideration, your zodiac sign will most likely be different. And if you were born between November 29 and December 17, your zodiac sign is one you’ve never heard of before: Ophiuchus! After Scorpius, the eliptic crosses across the constellation of Ophiuchus.
Check out your “actual” zodiac sign below, and visit the Birthday Sky program to see what the sky looked like on your birthday.
Is it true that horoscopes are based on science?
Is astrology accurate? Reading horoscopes is a popular pastime, but is there any scientific evidence that they are accurate?
When you’re enticed by a familiar interruption and your willpower weakens, problems can occur.
Every day, up to 70 million Americans consult their horoscopes. At least, that’s what the American Federation of Astrologers claims. According to a Pew Forum on Religion & Public Life poll conducted twenty years ago, 25% of Americans believe that the positions of the stars and planets have an impact on our daily life. In 2012, the General Social Survey indicated that 34% of Americans think astrology is “extremely” or “kind of scientific,” and that the percentage of individuals who think astrology is “not at all scientific” has decreased from two-thirds to about half.
Astrology is the concept that astronomical phenomena, such as the stars over your head when you were born or the fact that Mercury is retrograde, have the potential to influence our daily lives and personality traits. Of course, this is distinct from astronomy, which is the scientific study of celestial objects, space, and the physics of the cosmos.
A particular branch of astrologyforecasting a person’s future or providing advice on everyday activities through horoscopesis gaining in popularity. The Cut, for example, recorded a 150 percent rise in horoscope page views in 2017 compared to 2016.
Clearly, a lot of people are trying to figure out how to read the stars for guidance. Understanding the positions of the stars is the foundation of astrology, which appears to be a scientific discipline in and of itself. Is there any scientific evidence that astrology has an impact on our personalities and lives?
But, since I still have five minutes of this six-minute podcast to fill, let’s take a look at how astrology has been put to the test.
How did they come up with the zodiac signs?
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.
