History of Eclipse Calculations with Some Math

The earliest record of an eclipse in human history may have been from around 3,340 B.C.E. The consistent record of eclipses over the years has allowed astronomers to study Earth’s past. Scribes in Anyang, China, recorded eclipses on animal bones and tortoise shells as early as 1,200 B.C.E. The description provided is, “The Sun has been eaten.” Cultures around the world used that term and had varying animals as the eater. In China, a dragon eating the Sun was a good omen, but a dog eating the Sun was not a good sign. Aside from learning about cultures and beliefs, NASA’s Jet Propulsion Lab is using these records to research changes in Earth’s rotation. JPL researchers determined exact locations when and where the Moon’s shadow crossed the Earth and used math to calculate the rate of Earth’s spin at the time of the eclipse. JPL used eclipses recorded from 1,226 B.C.E., 1,198 B.C.E., 1,172 B.C.E., 1,163 B.C.E., and 1,161 B.C.E. Based on Earth’s current rotational speed these eclipses would have occurred thousands of miles from Anyang, China. Since records show they occurred over Anyang, scientists determined by math that the Earth’s rotation had slowed by 47-thousands (0.047) of a second per day over the last 3,200 years. But eclipse math was not developed recently. The Maya kept exact records of astronomical events, which have been found in numerous Mayan artifacts from hieroglyphs to codices. The Mayan calendar was very precise, and their astronomical calculations can be verified by their prediction of the solar eclipse of July 1991, which was found in their astronomical codices. Please join us for our May General Meeting presentation which will discuss the history of eclipse calculations from the Babylonians to the present day, and how eclipse knowledge has shaped scientific thought. Our presenter for our May General Meeting is veteran eclipse chaser Dan McGlaun. Dan has seen 16 eclipses from all around the world. He has done all of his own eclipse calculations and has a degree in math from Purdue University. Dan ran eclipse2024.org, which was very successful. He comes from the small town of Clayton, Indiana, and he was able to watch the eclipse from his backyard, http://www.eclipse2024.org.