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When studying ancient history, any information you can get is very helpful, and that applies not just to what was happening here on Earth, but also the movements of celestial bodies.
Today, astronomers are able to very accurately track the position of the Earth, the Moon, and the Sun at any given moment. Over the course of time, however, things can become less and less accurate. This is because the orbital speed, the ‘wobble’ of the Earth on its access, and other factors can all have an impact on the precise position. This is why, for example, there is a need for things like leap seconds to help keep things accurate.
With this in mind, anytime experts can gain a data point from the distant past that is shown to be accurate, it can help them to refine our understanding of celestial movements throughout history, and that is exactly what happened when some Chinese records from 709 BCE were studied closely.
This ancient document reveals information taken down by observers located in Qufu, within the Chinese state of Lu Duchy. The document itself is from several hundred years after the event, but the references to the event can be verified, giving the researchers a great deal of confidence in its accuracy.
The analysis was led by Dr. Hisashi Hayakawa of Nagoya University. They were able to determine that the solar eclipse in question was already known to exist, but its precise path was not known. Interestingly, they could not account for how the original observers could have seen what they did from where they said they were.
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That is, until the researchers realized that Qufu was actually in the wrong place in their records. Once they corrected these errors, the city was located 8 kilometers (5 miles) away, which lined up perfectly with what the observers wrote. In a statement about how this benefits us today, Hayakawa said:
“This correction allowed us to accurately measure the Earth’s rotation during the total eclipse, calculate the orientation of the Sun’s rotation axis, and simulate the corona’s appearance. This new dataset fixes coordinate errors in previous Earth rotation studies. Additionally, it improves the accuracy of dating and reconstructing historical astronomical events.”
Another interesting data point that was found in this document was the description of what the eclipse looked like. He explains:
“What makes this record special isn’t just its age, but also a later addendum in the ‘Hanshu’ (Book of Han) based on a quote written seven centuries after the eclipse. It describes the eclipsed Sun as ‘completely yellow above and below.’ This addendum has been traditionally associated with a record of a solar corona. If this is truly the case, it represents one of the earliest surviving written descriptions of the solar corona.”
This may be the earliest beginning of studying the solar corona, pushing back our understanding by many years. It also has some impact on astronomers understanding of the solar cycles, since the presence of the corona during the eclipse indicates that the sun was in a period of normal to high activity.
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It is not often that astronomers can update their records with new data points that are thousands of years old and gathered by humans of the day. Normally they are just able to make predictions of what happened based on the mathematical understanding of how objects move and behave in space.
This study has been published in The Astrophysical Journal Letters, and offers many helpful insights into the history
What a remarkable update to our ancient understanding of our place in the solar system.
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