What problems did the ancients find in the process of studying the position change of the vertical pole sun shadow?

The ancients found the following problems in the process of studying the position change of vertical pole sun shadow:

According to the understanding of the law of the sun shadow, human beings have long noticed the sun shadow of the vertical pole, pointing to the north every noon. However, at the same time on different days (outside noon), the sun shadow of the vertical pole will be biased. The more days apart, the greater the deviation.

So the answer is: human beings have noticed the sun shadow of the vertical pole very early, pointing to true north at noon every day. However, at the same time on different days (outside noon), the sun shadow of the vertical pole will be biased. The more days apart, the greater the deviation.

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In the 7th century BC, when we didn't know what the solar system, planets and stars were, our ancestors used earth gauge (an ancient tool to measure the shadow length of the sun, and observed and recorded the change of its shadow length at noon with a rod standing perpendicular to the ground to determine the seasonal change) to observe the shadow and established the summer solstice.

"The day is north, the day is long and the shadow is short, so it is called the summer solstice. At best, it is excellent. " Zunxian Manuscript records the origin of the name of the summer solstice, and it is also the earliest solar term among the 24 solar terms.

Summer solstice was also called "Summer solstice festival" in ancient times. At this time, it was the harvest season of wheat. The ancestors sang and danced to celebrate the harvest and offered sacrifices to their ancestors. Britain, Australia, Denmark and other European countries also have the tradition of celebrating the summer solstice, which is called "Midsummer Festival". In Britain, every summer to Sunday, thousands of people spontaneously gather around Stonehenge to watch the sunrise, revel and pray.

People will celebrate midsummer night the next night. According to legend, people may see elves and enter the magical world on this night. Shakespeare's A Midsummer Night's Dream was written on this basis.