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Astrology is a practice about 4,000 years old that looks for meaning in the positions of the Sun, Moon and planets. It rests on an old idea, "as above, so below": that patterns in the sky mirror patterns in a life.

Today's Western astrology blends several traditions. Babylonian sky-watching, Greek philosophy from Ptolemy's Tetrabiblos, Egyptian star calendars that split the sky into 36 decans, and Persian and Arabic refinements to the maths.

It uses the ecliptic, the Sun's yearly path across the sky, split into 12 equal 30-degree slices called signs. Your birth chart is a snapshot of where everything sat in that sky at the moment you were born.

Astrology has not been shown to cause anything. A 1978 study by Mayo, White and Eysenck found a link between Sun signs and introversion, but later work suggested it mostly appeared in people who already knew their sign's reputation. Most astrologers today treat it as a language for reflection, not a fixed prediction.

Astronomy is the science of what stars and planets are. Astrology asks what their positions might mean for us. They began together in ancient Mesopotamia, where priests tracked the planets both to keep calendars and to read omens.

They drifted apart during the Scientific Revolution. Johannes Kepler still cast horoscopes for nobles, yet his laws of planetary motion helped make astronomy an empirical science. Both still agree on the sky itself: when the Sun reaches the March equinox, astronomers note the season changing, and astrologers read it as the start of Aries and a new zodiac year.

No. It does not meet the scientific tests of falsifiability and repeatable results. Many people use it more like literature or depth psychology: a set of symbols that helps you think about your life.

Carl Jung studied it seriously and used it in his work on synchronicity and archetypes. Michel Gauquelin's "Mars effect" studies (1955 to 1991) claimed sports champions were more often born with Mars rising, a result that is still argued over and has not been reliably replicated. Its value, if you find any, is in what it helps you notice about yourself.

A birth chart (natal chart) is a map of the sky at the exact moment and place you were born. It shows where the Sun, Moon and planets were, placed in the 12 signs and 12 houses. Nobody else has the same one unless they were born at the same time and place.

You need three things: your date of birth, your time of birth (a birth certificate is best) and where you were born. Time matters because your rising sign changes about every two hours, and the Moon moves 12 to 13 degrees a day. Modern software works out the positions from ephemerides such as the Swiss Ephemeris, which is based on NASA JPL data.

You can make yours in a minute with our free birth chart tool.

Read together, they sketch a person. Someone with a Capricorn Sun, Cancer Moon and Scorpio rising might come across as intense and private, feel deeply protective inside, and be driven to build something that lasts.

There are several ways to divide a chart into houses. The most common:

• Placidus: the most popular in the West. Time-based. Struggles at far northern and southern latitudes.
• Whole sign: the ancient method, back in fashion. Each sign is one house.
• Koch: popular in German-speaking countries. Similar to Placidus with different maths.
• Equal house: each house is exactly 30 degrees from the Ascendant.
• Campanus: a space-based division some traditional astrologers prefer.

There is no single correct system. Pick one, stick with it for a while and see what rings true for you.

Aspects are the angles between planets in a chart. At certain angles their energies are said to work together, and at others they rub against each other. Astrologers allow an "orb" of leeway, usually 6 to 10 degrees for the major aspects.

Modern astrologers see tense aspects as places to grow, not bad luck. A chart full of squares often belongs to a busy, driven life. A chart full of trines can be easy, sometimes too easy.

Transits are where the planets are now, and the angles they make to your birth chart. Many astrologers use them to think about timing: which themes may be louder in your life this week, this year or this decade.

• Fast (Moon, Mercury, Venus, Sun): hours to days. Moods and small things.
• Medium (Mars, Jupiter): weeks to months. Projects, chances, friction.
• Slow (Saturn, Uranus, Neptune, Pluto): months to years. Big chapters of life.

The horoscopes in newspapers and apps are based only on your Sun sign. The format took off in 1930, when R.H. Naylor wrote one for the Sunday Express. Good ones use "solar houses": they put your Sun sign at the start of the chart and read the day's sky from there. They are broad by design.

Try reading your rising sign as well. Many astrologers find it fits outer events better, while the Sun sign fits how you feel inside.

A personal forecast uses your whole birth chart and looks at how today's planets touch your own. It is far more specific than "Capricorns may feel serious this month". Saturn crossing your natal Moon, which happens about once every 29 years, is often read as a time of emotional growing up and taking on more at home.

Popular compatibility looks at Sun signs and their elements. As a rough guide:

• Same element: an easy understanding (Fire with Fire, Earth with Earth)
• Fire with Air, Earth with Water: they tend to feed each other
• Fire with Water, Earth with Air: friction, and often attraction too

Sun signs alone say very little. Two people with "clashing" Sun signs can have Moon or Venus signs that fit beautifully.

Synastry lays one chart over another and looks at how the two sets of planets meet.

A composite chart takes the midpoint of each pair of planets to make one chart for the relationship itself. Synastry shows how two people affect each other. The composite shows what the two of you make together.

Astrology grew up in Mesopotamia, where Babylonian priests read the sky for omens about kings and kingdoms. The Enuma Anu Enlil, a collection of around 7,000 sky omens, dates to roughly 1000 BCE. At first astrology was about nations, not individuals.

After Alexander's conquests, Greek thinkers met Babylonian astronomy and created horoscopes for individual people. Ptolemy's Tetrabiblos (2nd century CE) set out the system and stayed the main textbook for about 1,500 years. Separate traditions grew in India (Jyotish, which uses the sidereal zodiac), in China (built around the 12-year cycle of Jupiter) and in Mesoamerica.

Scholars in the Islamic world kept Greek astrology alive and pushed it forward. Abu Ma'shar's Great Introduction (9th century) shaped European astrology for centuries.

In Renaissance Europe astrology was everywhere. Universities taught it beside medicine, and Marsilio Ficino, John Dee and Tycho Brahe all practised it. The Scientific Revolution slowly split astronomy away. There is a famous story that Newton told a sceptical Edmond Halley "I have studied the matter, you have not", though historians think it is probably made up.

Alan Leo made Sun sign astrology popular in early 20th-century Britain. Dane Rudhyar then mixed it with Jungian psychology, focusing on growth rather than prediction. The 1960s counterculture embraced it, and psychological astrology led through the 1980s and 1990s with writers like Liz Greene and Howard Sasportas.

Since the mid-2010s astrology has had a big revival, led largely by millennials and Gen Z. Apps put a birth chart on your phone, and social media turned "that is such a Scorpio thing to say" into everyday language. For many people it is less about prediction and more about having words for how they feel.

At the same time, old techniques came back. Project Hindsight translated Greek astrological texts, and teachers such as Chris Brennan, Demetra George and Austin Coppock brought back whole sign houses, sect (day and night charts) and ancient dignities. Many astrologers now mix these timing methods with a psychological reading.

Evolutionary astrology, developed by Jeffrey Wolf Green and Steven Forrest, reads the chart as a story of the soul's growth, with special weight on Pluto and the lunar nodes. Psychological astrology, rooted in Jung, treats the chart as a map of the psyche and a tool for becoming more yourself.

Casting a chart used to take hours with tables and arithmetic. Now software does it in a second. Many astrologers still feel that the reading itself, putting the pieces together into something that speaks to a real person, is where the craft lives.

Find your birth time, date and place, then make your chart with our free birth chart tool or a site like Astro.com. Start with your big three: Sun, Moon and rising.

Get to know the 12 signs, their elements and modalities, what each planet stands for and what each house covers. There is no rush.

Your own chart is your best teacher. Notice which houses are busy and which are empty. Keep a simple journal of how the sky lines up with your weeks, and see what you notice.

• The Inner Sky by Steven Forrest: a warm beginner's book
• Hellenistic Astrology by Chris Brennan: the traditional techniques
• The Twelve Houses by Howard Sasportas: the psychological approach
• Planets in Transit by Robert Hand: a classic on transits
• The Astrology Podcast: free episodes on almost every topic

Look at charts with friends and family. Astrology is a lifelong study, and it is more fun with other people.