Seven balances and six rooms - the Winter Olympics will bring ancient astronomical maps into the public eye

The "Seven Balances and Six Rooms Diagram" comes from a mathematical work of the Han Dynasty, the Zhou Spleen Arithmetic Classic. The book discusses in detail the cosmic model of the Gaitian theory that appeared at the end of the Warring States period, reflecting the understanding of the movement of the sun and the moon, the change of day and night, and the change of seasons.

In the figure, there are seven concentric circles, each circle is a balance, and the two balances are separated into one, and the size of the interval is equivalent to "nineteen thousand eight hundred and thirty-three miles and one hundred steps". Each scale represents the sun 's (apparent) orbit corresponding to different solar terms. For example, the winter solstice sun runs on the outer scale, and the summer solstice sun runs along the inner scale. That is the ancients believed that the summer solstice is the closest, so you can feel the heat, and the winter solstice runs to the farthest end, so it is cold. Of course, this is not true from the current point of view.

Over the course of a full year, the sun will slowly move from the outer balance (winter solstice) to the inner balance (summer solstice), and then from the inner balance to the outer balance, experiencing a total of 12 "balances" and 12 "intervals", which are evenly distributed, and together they are twenty-four solar terms.

The Seven Balances and Six Rooms Diagram establishes a more intuitive spatial model to describe the relationship between the solar annual visual motion and solar terms, and reveals the origins between astronomy and calendar.

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