Astrology, explained

Both traditions divide the Sun's yearly path into twelve 30° signs with the same names — Aries is Mesha, Taurus is Vrishabha, and so on. The difference is where they start counting. Western (tropical) astrology starts Aries at the March equinox, so its signs are locked to the seasons. Vedic (sidereal) astrology, or Jyotisha, starts Mesha at a fixed point among the stars.

About 2,000 years ago the two starting points were in the same place. But Earth's axis slowly wobbles like a spinning top — a cycle of about 26,000 years called precession — which drags the equinox backwards through the stars by about 1° every 72 years. The gap, called the ayanamsa, is now about 24.2° by the Lahiri reckoning that India's government calendar uses. That's why a "Leo" in a Western magazine is usually a Karka (Cancer) by Sun sign in Vedic astrology, and why Makar Sankranti falls on 14–15 January rather than at the December solstice.

Two other differences matter more in practice: Vedic astrology centres on the Moon sign (rashi) and the Moon's nakshatra, while Western popular astrology centres on the Sun sign; and Jyotisha is still tied to the calendar — the same positions decide festival dates, muhurats and the panchang you see on our Tamil and Telugu calendar pages.

Indian astronomy also splits the zodiac into 27 lunar mansions of 13°20′ each — roughly the distance the Moon travels in a day. Your birth nakshatra (janma nakshatra) names you in many South Indian families, sets your birthday in the Malayalam and Tamil tradition, and decides the starting point of the Vimshottari dasha planetary periods, whose lords follow the nine-planet cycle in the third column.

A birth chart places the twelve signs in twelve houses, each standing for an area of life — self, money, siblings, home, children, health, partners, transformation, fortune, career, gains and loss. The planets' movement through those houses after birth are transits (gochara). Daily horoscopes simplify this: they treat your sign as the first house and follow the fastest mover, the Moon.

That's exactly how our horoscopes for tomorrow are built — the Moon's real position, the traditional meaning of the house it falls in for each sign, and nothing made up.

The positions in astrology are real astronomy: the Sun, Moon and planets are where the calculations say. Whether they influence personality or events is another matter. Large studies — including tests of astrologers matching charts to personality profiles, and of people born minutes apart — have not found effects beyond chance. The best-known, by physicist Shawn Carlson in Nature (1985), found astrologers did no better than chance at matching charts to personality profiles.

Astrology remains part of the calendar and culture for hundreds of millions of people, and that is how we present it: accurate sky positions, the tradition explained, and no promises.