Does the record of a total solar eclipse 1,500 years ago contain the shocking secret of the Earth's rotation?

Ancient eclipse records reveal changes in Earth's rotation

The researchers searched historical documents dating back to the 4th century for records of a total solar eclipse.

(Illustration: This is an ancient record of a total solar eclipse, taken in Casper, Wyoming. Source: ESA/MP Ayucar, CC BY-SA 3.0 IGO)

The records of solar eclipse observations from 1,500 years ago show the history of the Earth's rotation and the changes in the Earth's movement in modern human history.

By searching records from the 4th to 7th centuries of the Eastern Roman Empire, the continuation of the Eastern Roman Empire after the fall of the Western Roman Empire, the researchers confirmed five records of solar eclipses that occurred near the western coast of the Mediterranean Sea, and determined the possible times and locations of these eclipses. Prior to this, there were very few records of solar eclipses during this period.

Because eclipses provide information about the motion of the Earth, these eclipse records are important tools for understanding the variability of Earth's rotation throughout history. However, our ancestors recorded astronomical events without annotating the key information that today's astronomers need, so it is often difficult to find the correct time, place, and range of historical eclipses.

"Although most first-hand witnesses of this period have been lost, quotations and translations of these events provide valuable information," said Akijū Murata, an assistant professor at the University of Tsukuba. "In addition to reliable locations and timely information, we also need to confirm the timing of the total eclipse, which is the time span from daylight to nightfall until the stars appear in the sky."

The team identified five total solar eclipses that occurred in the eastern Mediterranean region, in 346, 418, 484, 601, and 693 A.D. The new findings provide details on the difference between using the Earth's rotation as a time reference and not using the Earth's rotation as a time reference, or ∆t, which represents the length of an Earth day.

As an example of the impact of the new research, records show that on July 19, 418 AD, there was a solar eclipse so complete that the stars were clearly visible in the sky. The eclipse was viewed from Constantinople, the former capital of the Roman Empire, now located in Istanbul, Turkey.

"The earlier ∆t models suggested that Constantinople was not in the path of the total eclipse, but that eclipse was special in that the moon completely covered the sun for observers in the area. Therefore, this ancient record of a total eclipse means that the ∆t in the fifth century must have changed. Models of ∆t for later centuries also need to be adjusted based on other newly discovered records."

"Our new Δt data narrow the range and suggest that the marginal Δt values ​​for the fifth century should be adjusted upward, while those for the sixth and seventh centuries should be adjusted downward," Murata said.

Detailed corrections to Earth's rotation also help scientists understand other global phenomena in history, including changes in sea level and the volume of global ice.

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BY:Robert Lea

FY: Chen Mai Mai

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