Three zodiacs.
One sky.

I · Before there were clocks

Before there were clocks, we told time by the sky.

The Sun, the Moon, and the stars that came back each season were our first instruments. In the 5th century BCE, Babylonian astronomers cut that sky into twelve equal signs, measured against the fixed stars — a star-anchored way of reading it whose principles are still practiced by Vedic sidereal astrologers today. Then around 129 BCE, Hipparchus noticed something inconvenient. The sky was slipping. Earth’s axis wobbles like a slowing top, so the equinox creeps backward against the stars, about one degree every seventy-two years.

The zodiac has no natural beginning.

Ptolemy · Tetrabiblos · c. 150 CE

Knowing that, Greek astronomers made a deliberate choice. Around 150 CE, Ptolemy argued that the signs take their meaning from the seasons — the equinoxes and solstices — and not from the constellations they happen to be named after, anchoring the zodiac to the spring equinox and letting it drift from the stars on purpose. That’s Western tropical astrology. The two systems agreed around the 3rd century CE and have been pulling apart ever since; today they sit about 24° apart, roughly one whole sign. Neither one is the mistake. They’re measuring different things.

II · The tattoo

And then in 2023, I was about to get an Aquarius tattoo.

I decided to fact-check the design first. The stars didn’t line up. Not stylized, not simplified — just not the sky. It was a shape someone drew.

So I went looking, and found that this is normal. Zodiac designs that match nothing overhead are everywhere, including on very expensive things. A squiggle was good enough.

I didn’t get the tattoo.

III · What I built

I have a programming background, not an astronomy one. So I learned the astronomy — enough to do this properly, and not much more than that. This orrery is what came of it. It started as a way to check my own work.

It draws the Sun, the Moon and the planets where they actually are, for any date from 2001 BC to 3000 AD. Computed, not illustrated. Directions are real. Sizes and distances are not, and the panel behind the ⓘ says exactly how.

It also draws three zodiacs over the same sky: Western tropical, Vedic sidereal, and the IAU’s real constellation boundaries. They disagree. Speed time up and you can watch them disagree more — the tropical wheel sliding against the stars, a degree every seventy-two years. Run it back far enough and they line up again.

As far as I’ve found, it’s the first place you can watch that happen.