Over the past decade, interest in astrology—especially among the millennial generation—has been on the rise. “Astrology is currently enjoying a broad cultural acceptance that hasn’t been seen since the nineteen-seventies,” Christine Smallwood says in a recent article for The New Yorker. “The shift began with the advent of the personal computer, accelerated with the Internet, and has reached new speeds through social media.”

Here nine things you should know about the ancient practice of celestial divination:

1. Astrology is a type of divination that involves the forecasting of earthly and human events through the observation and interpretation of the fixed stars, the Sun, the Moon, and the planets. Several ancient cultures developed some form of astrology, with the oldest originating during the Old Babylonian period (circa 2000 BC) in Mesopotamia (an area that covers much of modern Iraq and Kuwait, as well as parts of Syria and Turkey). Some forms of astrology posit that the stars manifest the divine will of a god or gods while others rely on a totally mechanistic universe.

2. Genethlialogy (“the study that pertains to births”) or “natal astrology” is the application of astrology to the birth of individuals, in order to determine information about the nature and course of a person’s life. The idea is that since the universe is interrelated, astronomical bodies exert an influence on newborn children. The main subdivisions after genethlialogy are general, catarchic, and interrogatory. General or mundane astrology studies the relationship of the significant celestial moments to social groups, nations, or all of humanity. Catarchic or electional astrology determines whether or not a chosen moment is astrologically conducive to the success of a course of action. Interrogatory or horary astrology provides answers to a person’s questions, usually through “chart readings” based on the alignment of the celestial bodies at the moment of their posing the questions.

3. The most popular form of astrology in America is natal astrology, which relies on the zodiac. Within astrology, the zodiac (“circle of little animals”) is an area of the sky divided into 12 signs, each roughly corresponding to when the Sun passes through the constellations: 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), Sagittarius (Nov. 22–Dec. 21), Capricorn (Dec. 22–Jan. 19), Aquarius (Jan. 20–Feb. 18), and Pisces (Feb. 19–March 20). Most modern astrologers calculate charts using the Tropical Zodiac, which is based on seasons and does not actually match up with actual planetary positions.

4. Adherents of astrology believe each of the signs in the zodiac matches up with a psychological type. They also believe a person’s personality can be characterized by the zodiac sign that was ascendant at the exact moment they were born. To account for differences in personality among people born at roughly the same, astrology fans claim that a person can take on the traits of a related zodiac signs (e.g., “born on the Gemini Cancer cusp”). As with other psychological typing methods that rely on self-assessment (such as the Enneagram), those who believe in astrology often pick and choose which zodiac traits they believe fit their actual personality and ignore those that do not.

5. To tell about a person’s character or possible future, horoscopic astrologers rely on a horoscope (“view of the hour”), a chart of astronomical bodies that shows the relative positions of the Sun, the Moon, the planets, and the ascendant and midheaven signs of the zodiac at a specific moment in time. Most horoscopes are represented by a circle divided into 12 intersections, called houses. The most popular horoscopes, such as those found in newspapers, are based on the Solar House or Sun–Sign system. Horoscopes gained popularity after they began being printed in newspapers in the 1930s.

6. Astrology is mentioned in Scripture by several biblical prophets. The first direct mention of astrology in the Bible is in Isaiah 47:13 (NIV):

All the counsel you have received has only worn you out!
Let your astrologers come forward,
those stargazers who make predictions month by month,
let them save you from what is coming upon you.

Astrology is also referenced in Daniel 2:2 (NIV): “So the king summoned the magicians, enchanters, sorcerers and astrologers to tell him what he had dreamed.” Jeremiah 8:2 (NIV) also appears to reference astrologers: “They will be exposed to the sun and the moon and all the stars of the heavens, which they have loved and served and which they have followed and consulted and worshiped.” Because astrology was a form of inductive divination, it appears to be directly forbidden in Leviticus 19:26 (“Do not practice divination or seek omens”).

7. In the New Testament, the only obvious—though disputed—reference to astrologers appears in Matthew 2:1-2 (NIV): “After Jesus was born in Bethlehem in Judea, during the time of King Herod, Magi from the east came to Jerusalem and asked, ‘Where is the one who has been born king of the Jews? We saw his star when it rose and have come to worship him.’” Their description of seeing a celestial body as a portent of a significant event appears to be a type of mundane astrology (i.e., the study of significant celestial moments to social groups, nations, or all of humanity). Even if the magi (a term from which we get the word “magic”) were actual astrologers, this would not a biblical endorsement of astrology. Instead, it would be an example of how even pagans would recognize Jesus as God. As David Mathis says, “These magi are not respected kings but pagan specialists in the supernatural, experts in astrology, magic, and divination, blatant violators of Old Testament law—and they are coming to worship Jesus.”

8. For most of church history, orthodox Christians have uniformly opposed the beliefs and divination practices related to astrology. Augustine, who dabbled in astrology in his youth, spoke against it in both his Confessions and also The City of God. For example, in The City of God, Augustine asks:

Why, in the life of twins—in their actions, the events that befall them, their professions, arts, honors and other things pertaining to human life, as well as in their very deaths—is there often so great a difference that, as far as these things are concerned, many entire strangers are more like them than they are like each other, though separated at birth by the smallest interval of time but at conception generated by the same act and at the same moment?

Similarly, in his Summa Theologica, Thomas Aquinas denied that astrology could predict either the future or define our personality (“[I]t is impossible for heavenly bodies to make a direct impression on the intellect and will. . .”) In general, Christians have rejected astrology for numerous reasons, such as: it conflicts with the biblical prohibition against divination; has no basis in empirical observation; attributes to celestial forces some actions that should be attributed to providence; and seeks to find God’s hidden will in the movement of the stars.

9. A survey by Pew Research published in 2018 found that almost one in three adults (29 percent) in the United States believe in astrology. Despite being incompatible with orthodox Christianity, more than one-in-four Christians (26 percent) also believe in astrology, including 24 percent of Protestants and 33 percent of Catholics. At 18 percent, evangelicals are tied with agnostics as the second-least-likely group to believe in astrology (atheists are the least likely at 3 percent). At 34 percent, Protestants in historically black churches are the second-most-likely group to believe in astrology, following those whose claim their religion is “nothing in particular” (47 percent).