Transit

The natal chart is a frozen snapshot of the sky at the moment of birth. The planets naturally keep moving afterward — and when a moving planet forms an exact angular relationship (an aspect) to a point in the natal chart, that's called a transit. Example: if transiting Saturn today sits exactly where the Sun stood at birth, that's a Saturn transit over the natal Sun.

Transits are calculated purely geometrically: today's ephemeris positions are compared with the natal positions to check which angles — conjunction, sextile, square, trine, opposition — come within a small tolerance, the orb, of being exact. Fast-moving bodies like the Moon form several transits a day; slow ones like Saturn or Pluto only every few years.

A transit is not a prediction of an event. Astrological tradition reads it as a quality of the moment or a theme to notice; astronomically it's simply a measurable angular relationship between two points in time — no more, but no less.