“The vernal equinox — the spring crossing of the celestial equator — gave its name to the standard zero-point of the astronomical coordinate system, even though that point has drifted far from where Hipparchus set it in 150 BCE.”
Latin vernalis (of spring) came from ver (spring), which related to an ancient Indo-European root for green growth and warmth. Vernal entered astronomical vocabulary as 'vernal equinox' — the moment in late March when the Sun crosses the celestial equator going northward, making day and night of equal length. For ancient astronomers this was the year's hinge, the passage from darkness to light, the beginning of planting seasons across the northern world.
Hipparchus of Nicaea, working around 150 BCE, used the vernal equinox to define his astronomical coordinate system. He placed right ascension's zero-point — the 'first point of Aries' — at the vernal equinox position. Every other celestial object was measured east or west, north or south, from this reference. It was a choice of convenience that locked the astronomical coordinate system to a moment in time.
The problem: Earth wobbles like a spinning top, and this wobble (axial precession) causes the vernal equinox to drift westward through the constellations at about 50 arc-seconds per year. Hipparchus himself discovered precession in the 2nd century BCE. In 2,100 years the vernal equinox has moved entirely out of Aries (hence 'first point of Aries') and is now in Pisces, approaching Aquarius. The reference point drifts but the name stays.
The vernal equinox remains the zero-point of the equatorial coordinate system used in astronomy, though astronomers now use a specific epoch (J2000.0) to freeze the precession for calculation purposes. Spring's astronomical marker has become a fixed computational constant. Ver — the green warmth of the Roman spring — now anchors the celestial coordinates of a shifting sky.
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The 'First Point of Aries' has not been in Aries since about 68 BCE. Precession moved it into Pisces around that time, and it is slowly drifting toward Aquarius. When astrologers say the Sun is 'in Aries' in late March, they mean it is in the region of sky where Aries was when the system was invented 2,000 years ago.
Astronomy corrected this: the J2000.0 epoch freezes the coordinate system at 2000 CE positions. But the name vernal equinox, the Latin spring, the 'First Point of Aries' — all persist in documents and software that know the point has moved. Latin spring holds the sky's coordinate origin, even as the sky slowly turns away from it.
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