Scientists Studying Ancient Eclipse to Learn the History of Earth's Rotation

Ancient records of solar eclipses show how the Earth's rotation has altered. To find total solar eclipses, historians combed through texts from the fourth century.

Studying the History of Earth's Rotation

The history of the Earth's rotation and how its motion has evolved throughout recent human history have been revealed by records of eclipses seen roughly 1,500 years ago.

Records from the Byzantine Empire, which existed from the fourth to the seventh century A.D. and was the eastern part of the Roman Empire that persisted after the fall of the Western Roman Empire, were examined by researchers. - and pinpointed the probable timing and locations of five total solar eclipses witnessed in the Eastern Mediterranean. There were few reports of this solar eclipse in the past.

Understanding the Rotation

These data can help understand the variations of Earth's rotation through time since eclipses can provide information about our planet's motion. However, because our forebears did not record crucial details that modern astronomers need to know, it can be challenging to determine the precise dates, places, and sizes of previous eclipses.

Koji Murata, an associate professor at the University of Tsukuba in Japan, says, "actual eyewitness testimonies from this period have essentially been lost, but quotes, translations, etc. preserved by following generations give vital information" (opens in new tab). We also required proof that the eclipse totality - complete darkness during the day to the point where stars could be seen in the sky - had occurred.

The group found five complete solar eclipses that were seen in A.D. from the Eastern Mediterranean. 346, 418, 484, 601, and 693. The discoveries light the duration of an Earth day, or delta T, the difference between time measured with Earth's rotation and time recorded independently.

The significance of this discovery may be seen in the fact that a reported eclipse that took place on July 19, 418, was so thorough that stars could be seen in the sky. This solar eclipse observation location was Constantinople, which is now Istanbul in contemporary Turkey and was formerly the capital of the Roman Empire.

According to the earlier delta model, Constantinople was supposed to be beyond the path of totality, or the region where viewers may see the moon blocking the sun, during that specific eclipse. The delta T for the fifth century must thus be modified in light of this ancient report of a total eclipse. Delta T models for the following centuries must also be adjusted for other recently uncovered stories.

Comparing Models

According to Murata's new delta ΔT margin data, the margin for the fifth century should be changed upward, while those for the sixth and seventh centuries should be revised downward, which "fill a significant gap."

The updated information on the Earth's rotation may also aid researchers in their studies of other historical global phenomena, such as variations in sea level and the amount of ice on the globe.