October 22, 2010

First Recorded Solar Eclipse – China – 2137 B.C. (?)

According to Shu Chin ("The Book"), Chinese observers recorded a solar eclipse on this date almost four thousand years ago!

Did you notice my question mark in the heading above? I was surprised that we would know the particular day as well as year of something that happened so long ago. Obviously, Ancient Chinese didn't use the same calendar system we used today—so, I figured, someone must have translated an ancient date into a modern one. I wondered if there was any controversy.

Sure enough, I found a reference to the fact that a scholar named Chen came up with the October 22, 2137 BC, date. Another scholar named Liu dated the same item as October 23, 2110 BC. Wikipedia states that the entire claim of the recording of this eclipse is controversial. Maybe that's why many sources state that the first recorded solar eclipse was in Babylonia, miles away and years later.

Perhaps part of the problem is that ancient observers didn't know exactly what was happening. When we see references to sudden darkness or a dragon eating the sun, is this a record of an eclipse?

What is an eclipse, anyway?

You probably know that a solar eclipse occurs when the Moon gets between the Sun and the Earth, blocking the Sun's light from those observers who are in the Moon's shadow. On rare occasions, a total eclipse occurs, and every bit of the Sun is hidden behind the Moon. During a total eclipse, the Sun's disc is entirely covered by the black circle that is the Moon, and suddenly the Sun's much fainter corona shows up all around the black disc. (Normally, we can't see the corona because the Sun's bright light washes it out.)

IMPORTANT: It is not safe to watch a solar eclipse directly, just as it isn't safe to look directly at the Sun at any time. Here is a guide of safe ways to watch an eclipse. 

Note that the moon doesn't cast a very large shadow on the earth, so people living in a swath of land about 155 miles wide (750 km) would be able to see a total eclipse, which lasts about seven minutes.

More?

• Here is a website that shows when and where the next eclipse will happen. Be sure to scroll down to the Earth animation to see the “path of totality” (the tiny black dot inside the large gray shadow, which is the area where people will see the eclipse). Also, just below the Earth animation is the “teach section,” which has an animation that shows the positions of the Moon, Sun and Earth during an eclipse. There is also a gallery of photos and much more.

• A simple experiment can show how a smaller object like the Moon can completely hide a much larger object like the Sun. 

• And this YouTube video shows how eclipses occur. 

For more on eclipses, see this earlier post.