Scientists have found errors in one of the oldest existing records of total solar eclipses. With this error resolved, the door is opened to a better understanding of the era in which it occurred, both historically and astronomically. In addition, something we already knew is supported again: the Earth is slowing down and its rotation is happening more slowly.
July 17, 709 BC. On that day, those who were in the city of Qufu in China saw how night suddenly fell and when it was not night. The event was recorded in a chronicle known as the “History of Spring and Autumn”, where it was noted that the sun was completely eclipsed. This text becomes one of the oldest existing records of a total solar eclipse.
By knowing everything at the exact place and time, you can estimate how much the Earth’s rotation has changed since then. Unfortunately, when this operation is performed with this eclipse, the results do not fit with the knowledge we already have about our planet’s rotation at that time. This may result in cancellation of registration. But a team of scientists at Nagoya University found the source of the error.
Coordination error. After analyzing various reports from archaeological excavations and historical geographical evidence, these scientists found that the calculation problem was caused by an error of 8 kilometers in the coordinates of the city. With the information known about the Earth’s rotation during that period, it was impossible to see a total solar eclipse in the original coordinates. However, when they move 8 km, everything falls into place again.
Why it is useful. This finding is very useful because it suggests that we have enough information to better study both the geography and astronomy of this period and, through calibration, to know what happened in other periods. For example, it can be used as a basis for study HangzhouA text published eight centuries later describes another eclipse. In this case, the eclipsed Sun is said to be “totally yellow above and below”. Traditionally, this has been interpreted as describing the solar corona during times of great magnetic activity. Perhaps the peak of your cycle.
At that time reconstructions of solar activity were made using radiocarbon techniques, but it is useful to have other supporting evidence. Now, thanks to these base statistics that help us better understand the historical records, the coherence of the available information is strengthened.
The world is slowing down. It is well established by the eclipse history that Earth’s delta T (ΔT) in that year was between 20,264 and 21,204 seconds. It is a measure that distinguishes between Earth time (uniform) and Universal time (based on rotation), which tells us that, in fact, the Earth does not rotate at the current speed, but rather faster. This is mainly due to tidal effects, but also to other phenomena, such as mantle and Earth core processes. As for statistics, they have traditionally been calculated from eclipse records.
Omenology. Astronomy was given great importance in ancient China. But like other parts of the world they associated them with superstitions. Certain celestial phenomena, such as eclipses or auroras, worried them so much that the ruling dynasties employed experts to monitor them. This was a practice known as omenology and had political implications, as these events were often interpreted as a response to some misbehavior on the part of the ruler.
Thanks to these records, we have an increasingly accurate picture of both the sky and the behavior of our planet at that time. The good thing is, knowing this, we can also study other less documented periods and add evidence to what has already been studied using other techniques.
Picture | Edited with Luc Viatour, AI
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