By Aikaterini Niovi Triantafillaki
Why do we see the Moon “blood-red”? From the first explanations to today.
What is a “blood moon,” and how is it different from a total lunar eclipse?
Blood or red moons fueled many myths over the centuries before science explained them.
For the Vikings, two wolves—Sköll and Hati—chase the Sun and the Moon, and an eclipse happens when they catch them. In West African tribes, human anger was projected onto the celestial bodies; the eclipse is the result of their battle. During it, people were to make peace so that harmony would return between Sun and Moon. For the Egyptians, a pig nibbled the Moon for a while; for the Maya it was a jaguar, and in ancient China a three-legged frog—the “red” Moon was seen as blood from that near-meal. To keep the Moon from being eaten, each culture tried to ward off the hunter with rituals and customs—because who knows: if it ate the Moon, the Earth might be next!
From myths we move to ancient Greece, which correctly inferred Earth’s sphericity and the motions of the heavenly bodies, while records of eclipses have been found in ancient China and South American cultures.
And today, as we await September’s upcoming red Moon, let’s first clarify: a “blood moon” is a total lunar eclipse—the scientific definition of the phenomenon!
Lunar eclipses (we’ll talk about solar eclipses later, ( see. 12 August 2026 ) occur when Earth passes between the Sun and the moon and our shadow falls on the Moon.
There are two kinds of “shadow”: the penumbra, the partially shaded outer region, and the umbra, the fully shaded inner region. The first makes the edges look somewhat dimmer, and the second is the darker main part. When the Moon is in Earth’s umbra, we see it turn red.
But why red? It has to do with Earth’s atmosphere! As sunlight enters and is refracted/scattered through the air, the red wavelengths make it through. Bluer light is scattered more strongly by air molecules, whereas red light travels more easily. Also, the warmer the air—or the more dust or clouds there are—the redder the Moon will look, since heated air molecules and particles favor warmer hues (that’s also why sunsets are warmer than dawn—see here).
Sources:
1.https://science.howstuffworks.com/blood-moon.htm
2. https://en.wikipedia.org/wiki/Lunar_eclipse
3.https://nso.edu/for-public/eclipse-map-2026/
6.https://www.britannica.com/list/the-sun-was-eaten-6-ways-cultures-have-explained-eclipses
