It was a bit confusing to walk into the Davenport courtyard on Sunday night to find what seemed like the entire college camped out on the grass. Had I missed an email about some super popular Davenport College Council event? I quickly found out that this was not a student-run activity, but a general viewing of the lunar eclipse that was creating a so-called Super Blood Moon.
It’s not often that phenomena in science get titles as dramatic as “Super Blood Moon,” so it’s worth unpacking the name. The “super” aspect of Sunday’s moon was its size. From our vantage point here on Earth, it looked about 14 percent larger last night than it does normally. This is simply because the moon was closer to us. The moon does not orbit around the earth in a perfect circle. Instead, the moon follows an elliptical path, which means its distance to the earth changes depending on where it is in its orbit. On Sunday, the moon was as close to us as it can get, and therefore earned the right to be called “super.”
The most striking aspect of the sight of Sunday’s lunar eclipse was the moon’s blood-red tint. Why wasn’t the moon a bright white as it appears every other night? And of all colors, why red? The moon wasn’t bright white because it was obscured in shadow. There was a total lunar eclipse, which means that the earth was lined up directly in between the sun and the moon. Because our planet was in the way, the white light from the sun could not reach the moon to be reflected back at us as it usually is.
But why did we see a red moon? While most light from the sun is cut off from reaching the moon because Earth blocks its path, some light just misses hitting the Earth and does eventually make it to the moon. On its way there, the light waves pass through the earth’s gaseous atmosphere. But some components of the white light from the sun are better able to pass through the atmosphere than others. Some light waves are scattered by gas molecules and never reach their lunar destination. The degree to which light is scattered depends strongly on its wavelength. Shorter wavelengths — that is, light on the blue/violet end of the visible spectrum — are quite scattered, whereas light on the red end of the spectrum is barely scattered at all. As white light passes through Earth’s atmosphere, most wavelengths are thrown off track so that predominantly red ones reach the moon. This is why the moon was called not only “super” but “blood,” and why we had a beautiful view of the night sky from the Davenport courtyard last night.
Allie Schechter is a senior in Davenport College. Contact her at firstname.lastname@example.org.
(Featured image by Ken Yanagisawa.)