Where did zodiac signs come from?
The stars are just one of the many things in the natural world that human beings have turned to for answers over the years.
“We don't really know who came up with the concept of looking at objects in nature and divining influences on humans,” says NASA Space Science Education Consortium director of Citizen Science Sten Odenwald. “There's some evidence that cave art depicts the concept that animals and objects can be imbued with a spirit form that has an effect on you, and that if you appease that spirit form, you'll have a great hunt. That was supplanted by the concept of divination, which involves looking at objects in nature and studying them closely, such as tea-leaf reading.
Some form of astrology shows up in various belief systems in ancient cultures
In ancient China, nobles regarded solar eclipses or sunspots as harbingers of the emperor’s rise and fall, although people believed that these signs had less impact on the emperor’s life (Odenwald pointed out that in the lower classes, people had less time and control over divination. Less seems useless.) The Sumran and Babylonians around the middle of the second millennium BC. There seems to be many divination customs in British Columbia: for example, they observe spots on animal livers and intestines, and his idea of observing planets and stars is a way of tracking the position of gods in the sky. They returned to the Ammisadugh Venus tablet, which dates back to the first millennium BC and traced the movement of Venus. This is the first part of the so-called Babylonian planetary logo. The ancient Egyptians came up with the idea that star patterns form constellations, and the sun seems to “move” through them at certain times of the year..
Both of these theories are believed to have come together when Alexander the Great invaded Egypt in about 330 BC.
“It must have taken a lot of back-and-forth to get the Greeks on board with the concept of using planets for divination,” says Odenwald, “and because they were so deep into mathematics and logic, they figured out a lot of the rules for how this should work.”
Here’s how NASA has described how that logic led to the creation of the familiar zodiac signs known today:
Consider a straight line drawn from Earth to the Sun, then out into space, well beyond our solar system, to the stars. Then imagine Earth traveling around the Sun in its orbit. During one full trip around the Sun — or one year — this imaginary line will rotate, pointing to various stars. The zodiac is made up of all the stars that are close to the imaginary flat disk swept out by this imaginary line. The zodiac constellations are essentially the constellations that this imaginary straight line points to over the course of a year.
What are the 12 signs of the zodiac?
The 12 zodiac signs that many people are familiar with today — Aries (roughly 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), Sagit 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 identical to those we know today, such as The Great Twins, The Lion, and The Scales, and these were later integrated into Greek divination. These 12 signs were popularized by the astronomer Ptolemy, author of the Tetrabiblos, which became a key book in the history of Western astrology.
Odenwald said: "The whole idea is that the zodiac has a width of 30°, and the sun passes through these signs regularly throughout the year. This is Ptolemy's systematization," Odenwald said. Even the word "zodiac" comes from Greek, according to the Oxford English Dictionary the term is "sculptural figures of animals", and the order in which the symbols usually appear can be traced back to that period.
“Back at the time of the Greeks,” Odenwald explains, “the first day of spring started when the sun appeared in the constellation Aries and then everything was marked from that time forward around the circuit of the year.”
However, due to precession, the Earth has rotated on its axis since then, and the dates used to mark the signs no longer refer to the background constellations that give them their names. In reality, the timeline has changed by one sign to the west. That is to say, based on the mathematical division of the year, zodiac sign dates roughly correspond to the presence of the sun in the constellations of the signs preceding them today. (The fixed existence of the signs is also why the Minnesota Planetarium Society's 2011 claim that a 13th zodiac sign, Ophiuchus, should be added now, failed to result in a major astrological shift.)
“Previously, astrologers looked at where the sun was in relation to background constellations in general, and that usually lined up almost exactly with Ptolemy's zodiac signs,” Odenwald says. “Now, astrologers calculate and predict based on where the planets and sun are in relation to the 12 fixed signs, rather than where they are in relation to the constellations. According to astrology, if the sun is in the sign of Sagittarius on your birthday, you are a Sagittarius.”
What’s the difference between astrology and astronomy?
For centuries, astrology (the study of signs based on the passage of celestial bodies) and astronomy were regarded as one and the same (the scientific study of those objects). Johannes Kepler, a pioneering 17th-century astronomer who studied the motion of the planets, was considered an astrologer at the time. That began to change in the late 17th century, around the time of the Enlightenment.
When Sir Isaac Newton basically turned the sky into a calculator, mathematicized the movement of the planets, and realized that gravity controlled everything, says Odenwald, “a whole new scientific approach began to look at the sky and the movement of the planets and the earth consider .
That is when astronomy was recognized as a science and astrology was recognized as a pseudoscience. But its appeal is based on factors that figures can't account for, and the appeal of looking to the stars for answers hasn't faded — in reality, it appears to have grown in recent years. After all, more than half of millennials believe astrology is a science, according to a 2014 National Science Foundation survey.