Ancient Chinese Texts Reveal New Insights On Solar Eclipse And Earth's Rotation

A team of international researchers has uncovered fresh data on the world's earliest recorded solar eclipse using ancient Chinese texts. These findings could shed light on how the Earth's rotation has changed over centuries. 

The eclipse occurred on July 17, 709 BCE, according to a chronicle called Spring and Autumn Annals. However, this record was compiled about two to three centuries after the actual eclipse, in the court of the Lu Duchy, a vassal state during China's Zhou dynasty.

Lead researcher Hisashi Hayakawa of Nagoya University explained that this record is significant not only because of its antiquity, but also because of a later note added to the Book of Han. 

This note, written approximately seven hundred years after the solar eclipse, describes the sun as "completely yellow above and below." 

Historically, this description has been associated with the solar corona, the outer layer of the sun that appears around the edges of the moon during an eclipse. According to Hayakawa, this may be the earliest written description of the solar corona.

The research team attempted to verify the record by modeling the Earth's rotation at the time. They discovered that the eclipse was not visible from Qufu, the capital of the Lu Duchy, where the chronicle was written. The researchers then studied historical geographical and archaeological reports and found that previous studies used coordinates approximately 8 kilometers away from the ancient capital.

This correction helped them accurately measure the Earth's rotation speed during the eclipse, calculate the Sun's rotation axis, and accurately simulate the view of the corona, Hayakawa explained.

Co-author Mitsuru Soma of the National Astronomical Observatory of Japan said that this revised data set corrects errors in previous studies on the Earth's rotation speed. It also increases the accuracy of dating and reconstructing historical astronomical events. Ancient records were preserved because people believed that celestial events harboured auspicious or ominous omens for political events, which led to the careful documentation of eclipses, aurorae, and other astronomical events.

Dr. Meng Jin of the Lockheed Martin Solar and Astrophysics Laboratory said that by combining these ancient and meticulous observations with modern computational techniques, we can gain new insights into the Earth and Sun thousands of years ago.

The study was published in Astrophysical Journal Letters on December 2.