Random Zodiac Generator

What the random zodiac generator does

You need a sign. Maybe you are assigning one to a character, maybe you are settling an argument, maybe you are running a game and the fortune teller needs something to say.

Press the button and you get one.

What follows is the interesting part. Why the zodiac has twelve slots rather than some other number, why your sign almost certainly does not match the stars behind the sun on your birthday, and why the famous correction to that fact is also wrong.

How to use it

1. Choose how many you want. One for a single sign, more if you are drawing several at once.
2. Press Generate. A fresh draw every time.
3. Press Copy to take the set with you.

Why there are twelve of them

The sun takes a year to go around the sky and come back to where it started. That path is called the ecliptic, and it is a circle. The zodiac is that circle, cut up.

So the question is not really why twelve. The question is why anyone cut it at all, and the answer is that the Babylonians needed a calendar and they were extremely good at arithmetic.

Twelve is a wonderful number if you are dividing things. It goes into halves, thirds, quarters and sixths without leaving anything over. Their number system was built on sixty for the same reason, and we are still using it every time we look at a clock. Twelve months, twelve signs, sixty minutes, three hundred and sixty degrees. That is all one decision, made in Mesopotamia, that nobody has ever managed to undo.

So they took the circle and cut it into twelve equal slices of thirty degrees each. Then they looked at which stars happened to be sitting behind each slice and named the slice after them. The ram, the bull, the twins, the crab.

Read that order again, because everybody gets it backwards. The slices came first. The names came second, and the names were a convenience.

The signs are not the constellations

Here is the thing everybody has heard. The Earth wobbles. Over thousands of years that wobble drags the whole sky sideways, and so the stars behind the sun on your birthday are no longer the stars that were there when all of this was written down. Your sign is a month out of date. You are not really a Leo.

The wobble is real. It is called precession, it takes about twenty-six thousand years to come all the way round, and since Ptolemy set the system down in the second century the drift has come to roughly twenty-four degrees. That is most of a sign. All of that is true and none of it is in dispute.

The conclusion is still wrong.

It is wrong because a sign was never a constellation. A sign is a thirty degree arc, and it is measured from the March equinox, which is the moment the sun crosses the celestial equator going north. That is the anchor. Not the stars. The whole system is pinned to the tilt of the Earth and the position of the sun, and it always has been.

So when the stars drift, the signs do not go out of alignment with anything, because they were never nailed to the stars in the first place. They are nailed to the seasons. Aries starts at the equinox by definition, the way January starts on the first of January. Ask whether the equinox has drifted away from the equinox and the question falls apart.

What actually happened is that two thousand years ago the arcs and the star patterns lined up reasonably well, and for a while you could use either word and be understood. Precession pulled them apart. The correction people make today, that your sign is wrong, is really the observation that the two systems have separated. Which they have. It just does not make either of them wrong, any more than a clock is wrong for saying noon when the sun is not quite overhead.

There are two systems here. One is a calendar anchored to the equinox. The other is a map of where the stars are. They do different jobs, they answer different questions, and they briefly shared a set of names.

The thirteenth sign that is not a sign

Every few years the story goes round again. Astronomers have found a thirteenth sign. Everything you know is wrong. Ophiuchus, the serpent bearer, has been hiding on the ecliptic all along and nobody told you.

Ophiuchus is real, and the sun really does pass in front of it, from roughly 30 November to 18 December each year. That part checks out.

What is not true is that anyone discovered it. Ptolemy knew. He was writing about the ecliptic in the second century, he could see perfectly well that a corner of Ophiuchus poked over the sun's path, and he did not count it, because he was not building a list of constellations. He was dividing a circle into twelve. A star pattern brushing the edge of the arc was not relevant to what he was doing.

The other half of the story is stranger, and it is the part that actually pays off.

Constellations did not have edges. Not vague edges. No edges at all. For most of recorded history a constellation was a picture people agreed on, drawn to taste, and where one ended and the next began was a matter of which atlas you owned. It stayed that way until the International Astronomical Union finally sat down in 1928 and had the Belgian astronomer Eugène Delporte draw formal boundaries, published in 1930, as straight lines along the coordinate grid. That was an administrative act. It was done so that astronomers could say where something was without arguing about it.

And the moment you draw hard borders around star patterns, you find out how unequal they are. The sun spends about forty-four degrees of its journey crossing Virgo. It spends about seven crossing Scorpius. Seven. Then it drops into Ophiuchus for about eighteen, which is more than twice as long as it spent in the scorpion.

So a real Scorpio, in the sense of the sun genuinely being in front of the stars of the scorpion, is about a week's worth of people a year. Virgo would get six weeks. That is what a zodiac built out of constellations would actually look like, and it is a mess, which is precisely why nobody built one that way.

The twelve equal arcs were the point. Ophiuchus is not a thirteenth sign for the same reason a thirteenth month would not appear if you noticed some extra stars. The signs were never a headcount of what is up there.

Where these come from

The twelve are the standard ones, the same twelve the Babylonians settled on and Ptolemy wrote down, curated and checked by hand. Your browser picks from them at random. Nothing you do here leaves your device.

Questions people ask

So is my star sign right or not?

It is right in the system it belongs to. If you were born in early August your sun was in the arc called Leo, and that arc is measured from the March equinox, and that has not changed and will not change. If you are asking which star pattern was actually behind the sun that day, that is a different question with a different answer, and it is a question about maps rather than about signs.

What is the difference between tropical and sidereal astrology?

Tropical is the system described above, anchored to the equinox, and it is what Western horoscopes use. Sidereal keeps the signs pinned to the stars instead and lets them drift along with precession, which is the approach used in Indian astrology. They disagree by around twenty-four degrees today, which is why the same birthday can give you different signs depending on who you ask. Neither is a mistake. They are answering different questions.

If the sun is in Ophiuchus for eighteen days, why is nobody an Ophiuchus?

Because the sign covering those dates is Sagittarius, and it is an arc rather than a star pattern. The sun can be in front of whatever it likes. The arc does not move.

How fast is precession, really?

About one degree every seventy-two years. Slow enough that nobody notices in a lifetime, fast enough that Hipparchus spotted it in the second century BC by comparing his own star positions against records made a century and a half earlier. It takes roughly twenty-six thousand years to complete a full circuit.

Why are the signs grouped into fire, earth, air and water?

Because they are evenly spaced. Take every fourth sign around the circle and you get a set of three, a hundred and twenty degrees apart. Do it starting from a different sign and you get another set. The four groups fall out of the geometry of dividing twelve, which is the same reason twelve was chosen to begin with.

Can the same sign come up twice?

Not within a single draw. Ask for several and you get several different ones. Press again and everything is back in play.

References

1. Sky & Telescope. A Sign of the Times. https://skyandtelescope.org/astronomy-news/observing-news/a-sign-of-the-times/
2. EarthSky. Sun enters Ophiuchus on November 30. https://earthsky.org/astronomy-essentials/sun-in-ophiuchus-november-30-to-december-18/
3. EarthSky. Is Ophiuchus the 13th constellation of the zodiac? https://earthsky.org/constellations/ophiuchus-the-serpent-bearer-13th-constellation-zodiac/
4. Universal Workshop. Sun entering signs and constellations. https://www.universalworkshop.com/sun-entering-signs-and-constellations/