People have been studying the moon and stars for hundreds of thousands of years. Ancient people noticed the stars appeared to be locked into specific patterns that could be measured and tracked. At the time, people didn't understand that the Earth was a sphere orbiting the sun, or that the stars were other suns many miles away. Their only understanding of the stars was that they were consistent, and the astral bodies became tied to religious superstitions. When comets came into our view, early peoples panicked and predicted danger, disease, and death, because of the fear of disorderly stars. "Disaster" actually comes from the words "bad star." As a result of our regard for the stars, many different ancient peoples would study the constellations present at birth to determine that person's life story and eventual personality. Today, astronomy, or the study of the universe and its contents, has differentiated itself a great deal from astrology, or the study of how the stars affect people on Earth. However, studying constellations, zodiac signs, and the superstitions surrounding them has become a fun pastime for many Americans.
Often, when people ask, "what's your sign?" they're talking about the Greek astrological zodiac, which is based on several of their many constellations. These signs were based on when the sun appeared within certain constellations during your birth. On your birthday, the sun should be within the constellation that your sign is named after. For instance, if you're an Aquarius, the sun should appear within or near the Aquarius constellation during the time of your birthday. There are twelve signs: Sagittarius, Scorpio, Capricorn, Aquarius, Pisces, Leo, Virgo, Cancer, Libra, Taurus, Gemini, and Aries. Recently, there was some news about the inclusion of a new sign: Ophiuchus. Astronomers (not astrologers) determined that, due to the moon's gravitational pull, the alignment of the stars was no longer consistent with the observations of ancient astrologers. The addition of a "new" sign was to make up for that shift.
The Chinese Zodiac differs a great deal from the Greek Zodiac. The Greek Zodiac was based on the sun's position, and the Chinese calendar was based on a 60-year lunar cycle, which included rotations of the well-known 12-year cycle. Each lunar year was based a specific zodiac animal: sheep, dog, pig, monkey, rooster, horse, snake, dragon, rabbit, tiger, ox, and rat. These animals were based on folk stories much less than Chinese constellations. Those signs predicted your personality to some degree, but were considered to be more important for determining marriage compatibility. The best matches included two people born four years apart. Again, though Chinese astrology and astronomy was fascinating, the zodiac we know of is not based on the solar placement within its constellations.
The last element that many astrologers pay attention to is the phase of the moon during your birth. Of course, people know of the full moon (or entirely lit moon) and the new moon (where the moon is not visible). There are also phases in which the moon is partially showing. A crescent moon describes when the moon is less than a quarter full. A gibbous moon describes when it is almost full or more than one half full. Also, the moon can be "waxing" or becoming more lit, or "waning" or becoming less lit. Astrologers talk about your "moon phase," which describes the relationship between the sun and the moon at the time of your birth, which is not the same every birthday. This is yet another element that is believed by some to impact your personality and your life. Zodiacs and moon phases are cool to think about, however, it's important to note how much our understanding of the stars and moons have evolved since the dawn of astrology. The sun doesn't orbit Earth; it's the other way around. The moon is not a goddess; it's a natural satellite orbiting the Earth. The stars are not static; they're constantly moving at incredible speeds very far away.