"Thirty spokes join at a single hub,
But it is precisely where there is nothing
That the utility of the wheel resides.
Having a thing is beneficial,
But having nothing is useful."
Finding the center of the heavens in 3000 BCE.
The Big Dipper (bottom) is part of Ursa Major, the Little Dipper (Little Bear, top) of Ursa Minor
The character dì: Supreme One; emperor. The one who represents the center of the heavens on earth. At left an old version of the character.
In the time of the Shang there was no star in the center of the rotating heavens. The spot could be found by connecting other stars, and where the lines intersected, was the exact center of the rotation. The character dì seems to be an image of a tool which might have been used for this - and then became the emblem of the emperor. (Pankenier p.103)
Liji: "Now the rites necessarily have their origin in the Supreme One, which divides to become Heaven and Earth, revolves to become yin and yang, and changes to become the four seasons".
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The image shows a person, holding a carpenter's square in his hand.
From Richard Sears: 矩 from person 矢大 holding a 巨工 carpenters square. Meaning carpenters square.
This square is part of the instrument used for finding the center of heaven, the northpole.
Di is the regulator of the time. He governs the law of Heaven, which is also the subject of hexagram 1. The celestial dragon is the clockhand of Heaven's watch, indicating the rise and decline of the light and of the seasons.
The supreme god is the center. Long ago there was a bright star at the northpole but precession moved true north to another point, where 'nothing' is.
"The form of the supreme one is emptiness" <Lie Yukow>.