You Are Not a Leo

Five rules astrology breaks

Skip the question of evidence. Astrology fails on its own terms, because its rules contradict the sky it claims to read.

The sky moved. The horoscope did not.

Astrology's ruleYour sign is the constellation the sun stood in when you were born.

The Earth's axis wobbles like a spinning top, tracing one slow circle about every 26,000 years. This is called axial precession, and it drags the whole backdrop of stars along the calendar.

The horoscope dates were fixed in Ptolemy's era. Since then the stars have slipped about 26 degrees, close to a full month. If your horoscope says Sagittarius, the sun was almost certainly in Scorpius or Ophiuchus. Western astrology quietly solved this by cutting its signs loose from the stars they are named after and pinning them to the seasons instead.

Drift rate: 50.3 arcseconds per year, about 1 day every 72 years.

Constellations are not things.

Astrology's ruleEach sign's stars act together and send out one kind of energy.

A constellation is a pattern seen from one spot: here. Its stars share no gravity, chemistry or history. They only line up from Earth's point of view, and they sit at wildly different depths.

Calling that a single force is like circling a fly on your window and an airplane in the sky and declaring them one machine.

Leo: Denebola (the tail) is about 36 light-years away. Regulus (the heart) about 79. Adhafera (the mane) about 270.

Thirteen, not twelve.

Astrology's ruleThe sun moves through 12 signs, one per month.

Under the official constellation boundaries astronomers adopted in 1930, the sun's path crosses 13 constellations. The thirteenth, Ophiuchus the serpent bearer, sits between Scorpius and Sagittarius and never got a horoscope.

The real constellations are also wildly unequal. Astrology ignores that and carves the sky into 12 identical 30-degree slices.

Sun in Virgo: about 45 days. Sun in Scorpius: about 7.

What counts as a planet?

Astrology's ruleThe planets shape who you are.

Classical astrology stopped at Saturn, the last planet known to naked-eye astronomers in AD 150. When Uranus, Neptune and Pluto turned up, astrologers gave them personalities and folded them in.

Then the logic stops. If Pluto matters, why not Eris, a dwarf planet more massive than Pluto? Why not Ganymede or Titan, moons bigger than the planet Mercury? The list follows human naming habits, not mass, distance or anything physical.

Eris: about 27% more massive than Pluto. Ignored.

Why the first breath?

Astrology's ruleYour chart is set at the exact moment you are born.

Biologically, birth is an arbitrary milestone. A baby has been growing, and building a nervous system, for months before delivery.

If planets exert a gravitational or electromagnetic pull on living tissue, nothing explains why the womb blocks it for nine months and it switches on the second the cord is cut.

At arm's length, the doctor delivering you pulls on you harder than Mars does, even at its closest.