Neil deGrasse Tyson Explains Why Astrology's

I spend most of my professional life watching powerful systems absorb inconvenient evidence and continue operating as though nothing happened. A coastal city floods for the third time in a decade; the infrastructure report notes the anomaly and recommends "further study." An ice sheet collapses ahead of every model projection; the policy response is to update the models. The evidence lands. The system flexes around it. Things proceed.

So when Neil deGrasse Tyson, the Frederick P. Rose Director of the Hayden Planetarium, summarized his entire case against astrology in four words — "it just doesn't matter" — I recognized the mechanism immediately. Not as astronomy's problem. As a pattern I cover every week in a different domain.

In a recent conversation with physicist Brian Keating on the Into the Impossible podcast, Tyson walked through the two cleanest arguments against astrology's internal coherence. The first: there's a 13th zodiac constellation called Ophiuchus, straddling the ecliptic between Scorpius and Sagittarius, through which the sun passes for roughly two weeks each year. If you were born in late November to mid-December, the sun was in Ophiuchus on the day of your birth — not in Sagittarius, where your horoscope app has confidently placed you. Ancient Babylonian astrologers almost certainly knew about it and chose to work with 12 signs anyway, probably because 12 divides more cleanly into a calendar than 13. A tidy system won out over an accurate one.

When astrologers are confronted with Ophiuchus today, Tyson says, the response is revealing: they acknowledge that constellation boundaries are essentially arbitrary. Which is technically true. The International Astronomical Union's constellation borders are a relatively modern convention. But, as Tyson points out, that defense detonates in their hands: "So it's just an arbitrary distinction what constellations the astronomers draw. So why isn't it arbitrary what you astrologers draw from the place of the sun on my mother's day of giving birth to me?"

You cannot invoke the arbitrariness of scientific classification to deflect one challenge and then treat your own classifications as cosmically meaningful. The move is too visible once you see it.

But Tyson thinks the Ophiuchus problem, as damaging as it is, isn't actually the killing blow. The killing blow is precession.

The Earth doesn't spin on a perfectly stable axis. It wobbles — a slow, gyroscopic drift with a period of roughly 26,000 years, driven by the gravitational pull of the sun and moon on the planet's equatorial bulge. This precession of the equinoxes means that the sky, as seen from Earth, shifts gradually against a fixed calendar. Over the two-plus millennia since Babylonian astrologers codified the zodiac, that drift has accumulated to something in the neighborhood of a full month — though the precise figure varies depending on which part of the zodiac you're measuring and whether you're working with the tropical or sidereal system. The practical upshot: the sun's actual position in the sky on your birthday is roughly one full zodiac sign behind where classical astrology puts it. You can verify this on any modern star chart.

The response from practicing astrologers, in Tyson's experience? The same four words: it just doesn't matter.

What astrologers are effectively saying — and this is worth being precise about — is that the system was calibrated against sky positions that no longer correspond to current reality, and that calibration error is not a problem because the system works independently of the sky. The stars are no longer the point. They may never have been the point. Astrology has quietly decoupled from astronomy and simply hasn't told its customers.

I want to be fair to the strongest version of the counterargument here, because I've heard versions of it and it's not nothing: many contemporary astrologers explicitly use the tropical zodiac, which is fixed to the seasons rather than the constellations, and they're aware of the distinction. For them, Tyson's precession argument is attacking a naive form of astrology they don't actually practice. The sun being "in Aries" in their system refers to the spring equinox, not to the Aries constellation. Whether that rescue maneuver saves astrology as a coherent system or simply reveals how far it has drifted from any empirical anchor is, I think, the genuinely interesting question — and one the horoscope apps are not rushing to explain to users who still think the stars are involved.

What Tyson offers as a companion argument is less about astronomy than about cognition. He describes an encounter after a class at the Hayden Planetarium, years before he was a public figure: a professional astrologer, hoping to pick up some useful astronomical knowledge, asked him his sign. Tyson declined to tell her, suggesting that if astrology were as diagnostically powerful as claimed, she ought to be able to determine it from his personality. She guessed wrong eight consecutive times. On the ninth attempt, she was correct — and said, "I knew it."

The mathematics of this are unforgiving. With 12 signs, random guessing produces a correct answer roughly once every 12 attempts. Getting it on the ninth try is, if anything, slightly worse than chance. The astrologer had zero signal. But the one hit, arriving after eight misses, was what her brain encoded as evidence of her ability. The misses dissolved.

Tyson connects this to a broader point about probabilistic thinking: "The human brain doesn't seem to be wired to think statistically or probabilistically about anything, leaving us susceptible to that weakness being exploited by entities such as casinos."

The casino parallel is the one I find myself pushing on, because in my domain it does significant damage at scale. Casinos are a clean case: the house edge is real, consistent, and disclosed in the fine print of the games themselves. The architecture — the deliberate absence of clocks, the engineered lighting, the careful removal of any external reference point — is not hidden. It is simply allowed to work because people cannot feel the cumulative math the way they can feel a single win. The ornate excess of a casino is not a contradiction. It is the margin, made physical. You are, as Tyson puts it, "literally walking into a place that screams out, 'I am going to rob you.'"

The difference between a casino and a horoscope app is that the casino is operating legally within a disclosed system. The astrology industry — variously estimated in the billions of dollars globally by market research firms, though the figures shift widely depending on methodology and what you're counting — is selling something its practitioners increasingly define in ways that cannot be tested. That's not a marginal epistemological concern. That's the product architecture.

I cover industries that do this too. The carbon offset market spent years selling instruments whose underlying accounting was, let's say, creative. Clean coal was a brand campaign. "Net zero by 2050" commitments have launched with more ambition than mechanism. In each case, the system generated enough atmospheric plausibility — enough correct guesses — to sustain belief. The misses got filed somewhere inconvenient.

Tyson closes with a quote he credits to a character named Merlin from one of his books — the transcript doesn't make the attribution fully clear, and I want to flag that I haven't independently verified which book this appears in or in what context — but the line is: "There's nothing logical about things astrological." It's a clean rhetorical finish. The wordplay earns its place.

What I keep returning to, though, is not the wit. It's the phrase that came earlier. It just doesn't matter to astrologers. The evidence is presented. The system acknowledges it. The system continues. This is not unique to astrology and it is not a minor human quirk. It is the load-bearing mechanism in every policy failure I have reported on for the last decade.

The question isn't whether astrology is false. The question is what it tells us about our collective tolerance for frameworks that have quietly decoupled from the evidence used to justify them — and whether we are applying the same scrutiny to the frameworks where the stakes are rather higher than what a Scorpio should be watching out for this month.

Olivia Meng is Buzzrag's climate and environment correspondent.