Is astrology a science?

The distinction that matters

Astrology contains genuine science and isn't one. Both halves are true and people usually drop one.

The astronomy is real. Planetary positions in a modern chart come from numerical models good enough to navigate spacecraft. There's nothing pseudoscientific about calculating where Mars was on your birthday; that's just arithmetic applied to an ephemeris.

The interpretation is where the claim to science fails. 'Mars was at 14° Leo' is a measurement. 'Which means you assert yourself dramatically' is a claim of an entirely different type, and it's that second step that has never been supported.

Popper and falsifiability

Karl Popper's problem was demarcation: what separates science from everything else that sounds like it? His answer was falsifiability. A scientific theory must forbid something. It must be possible to state in advance an observation that, if it occurred, would show the theory false.

Astrology was one of his central examples, alongside Freudian psychoanalysis and Marxist historical theory. His objection wasn't that astrologers were stupid or dishonest. It was that their theories could absorb any outcome. Whatever happened, an explanation was available afterwards, and a theory compatible with every possible result tells you nothing about which result to expect.

This is the sharpest thing that can be said against astrology, and it's sharper than 'the stars are too far away'. A theory does not have to have a known mechanism to be scientific. It has to be capable of being wrong.

Popper was right about astrology and I'd rather the trade admitted it than kept arguing about mechanisms.

What happened when it was tested

Shawn Carlson's study, published in Nature in 1985, is the most-cited attempt. Astrologers, working with birth charts, were asked to match each to one of three personality profiles. The design was double-blind and agreed with participating astrologers in advance. They performed at chance.

Other work has looked for correlations between birth data and occupation, personality measures and life outcomes. The pattern is consistent: where claims are specific enough to check, effects don't appear.

The best-known apparent exception is the 'Mars effect': Michel Gauquelin's finding of an association between Mars placement and eminent athletes. It generated decades of dispute over sampling and replication and isn't accepted as established.

What 'not a science' does not mean

It doesn't mean astrology is worthless, and this is where both sides usually overreach.

Literature isn't a science. Neither is history's interpretive side, nor most of philosophy, nor any framework people use to think about their own lives. 'Not science' places astrology in an enormous category that contains a great deal of genuine value. What it does mean is that astrology can't borrow science's authority. It can't claim to have shown anything.

So the fair position is narrow. Astrology as a symbolic vocabulary for reflection: available, harmless, sometimes helpful. Astrology as a source of factual claims about your future, your health or another person: not supported, and marketed that way constantly.

Where that leaves a chart

It leaves the computed parts intact and the interpretive parts labelled. That's exactly how AsterNym is built: positions from real ephemeris data, the zodiac and house system stated, uncertainty flagged when a birth time is missing, and a published list of things we refuse to tell you.

If you want the fuller version of the accuracy question instead of the demarcation question, that is how accurate is Western astrology.

Why is astrology considered a pseudoscience?

Because its interpretive claims aren't falsifiable. They don't specify in advance what observation would prove them wrong, so any outcome can be explained afterwards. Karl Popper used astrology as his central example when formulating this criterion.

Has astrology ever been tested scientifically?

Yes. The best-known test is Shawn Carlson's double-blind study published in Nature in 1985, in which astrologers attempted to match birth charts to personality profiles and performed at chance. Other studies looking for correlations with occupation and personality have found no reliable effects.

Is the astronomy in a birth chart accurate?

Yes. Planetary positions are computed from the same numerical models used for spacecraft navigation and are accurate to a fraction of a degree. It's the step from position to meaning that has no scientific support.

What was the Mars effect?

Michel Gauquelin reported a statistical association between the position of Mars and eminent athletes. It prompted decades of dispute over sampling methods and replication attempts and isn't accepted as an established finding.