A Sign of Apocalypse

Throughout mankind’s history we have looked to the sky for inspiration, navigation, and guidance in understanding our world. Astronomical phenomena have influenced our creation myths and religions. The magnificent display of a lunar eclipse has impacted cultures and inspired fear throughout mankind's past. The lunar eclipse is one of the most documented astronomical occurrences in history. For thousands of years, civilizations have been observing its red glow and attributing meaning to the sight. Many feared that the lunar eclipse was an omen of evil or an indication that tragic events were on the horizon. 

The Ancient Mesopotamians, one of the early cultures to study astronomy and track the movements of celestial objects, believed that during the lunar eclipse, the Moon was being attacked by demons. Their astronomical observations and recordings were advanced enough that they could predict when a lunar eclipse would occur. In 1502 Christopher Columbus and his men were stranded in Jamaica and had been surviving with help from the native Taíno people. However, the natives grew increasingly impatient with the European squatters beginning to refuse aid and supplies to Columbus and his men. Columbus used information from an almanac of astronomical tables, which informed him of the occurrence of a total lunar eclipse within a few days. He told the natives that if they did not continue giving him food and supplies his god would inflame the Moon with his wrath as a sign of future punishment. As predicted the lunar eclipse followed. Terrified by the blood-colored Moon they acquiesced to Columbus’ demands. 

Lunar eclipses have also aided in furthering our understanding of our universe. The Greek astronomer and mathematician Aristarchus of Samos, known for proposing the first Helio-Centric (sun-centered) model of the solar system made great strides in the field of astronomy. He famously used the occurrence of a lunar eclipse and his understanding of mathematics to calculate the distance from the Earth to the Moon. By using a known size of the Earth and measuring the duration of the lunar eclipse, he was able to calculate the distance from the Earth to the Moon. While relatively inaccurate, he was the first to ever do this calculation.

While for most people the lunar eclipse no longer signifies the coming of an apocalyptic event, the mystique surrounding the infamous Blood Moon holds to this day. The lunar eclipse is in fact not mystical at all; it is quite simply the Earth passing in between the Sun and the Moon, casting a shadow on the Moon. As the Moon begins to be shadowed from part of the Sun's light, the Moon will appear to dim (see Figure 1). This is when the Moon passes into an area called the penumbra, the part of the shadow where the entirety of the Moon is still illuminated by the Sunlight, however part of the Sunlight is blocked by the Earth causing the drop in brightness. When just this happens it is called a penumbral eclipse and this accounts for most lunar eclipses. On even rarer occasions, the Moon will then begin to disappear into the night sky. This occurs as the Moon passes into the umbra, where all direct sunlight is blocked casting a dark shadow on the Moon. The Moon will fully disappear entering what is called totality. Then the lunar eclipse shows its true colors.

lunar eclipse digram sun and earth and dotted lines Ethan Gevinson
Figure 1. Parts of a lunar eclipse. Image not to scale. 

Even when the Moon is entirely in the umbral shadow, some light manages to reach the Moon by passing around the Earth, through the atmosphere. This causes a change in color due to a principle called Rayleigh scattering, and this is the same principle that gives the sky its blue color. This principle states that when light passes through a medium such as the atmosphere, shorter wavelength of light is scattered more. What we end up seeing is that light towards the blue end of the spectrum is scattered more than red light since blue light has a shorter wavelength (e.g. Figure 2). This gives the effect of different colors of light being refracted at different angles similar to light passing through a prism. 

light waves in space red, yellow, green, blue, violetEthan Gevinson 
Figure 2. Bluer light has a shorter wavelength and redder light has a longer wavelength. 

This is also why sunrises and sunsets appear red. As the Sun appears to set on the horizon, the sunlight passes through the longer path of Earth’s atmosphere to reach your eyes than when it appears high in the sky. The blue light is scattered away while the red light could reach us. Interestingly, when we are looking at a lunar eclipse, the red light projected onto the Moon is the light of sunrises and sunsets that we see on Earth (Figure 3). So if you manage to see a blood Moon, you can consider yourself lucky, as you are seeing the light from all of the sunsets and sunrises from around the world being projected onto the Moon. 

Earth in space surrounded by red green blue yellow violet light Ethan Gevinson
Figure 3. The light from the Sun being scattered by the atmosphere, giving the Moon its red color.

When is the next lunar eclipse? On May 5th, 2023 between 15:15 and 19:32 UTC the Moon will pass into the Penumbra creating a nearly total penumbral eclipse visible from most of Europe, Africa, and Asia (Figure 5). This type of eclipse unfortunately will not result in the iconic Blood Moon, just simply a dimming of the Moon with darker shading on one side. Whether you are able to see the upcoming eclipse or will be holding out until the next total lunar eclipse in March of 2025 it is an impressive sight to behold. People have always looked to the skies for answers and have learned from events like the lunar eclipse. To join them all you need to do is look it up. 

red light surrounded by dotted circles and the moon's path Ethan Gevinson
Figure 4. The Moon’s path through the Penumbra on May 5th 2023, creating a penumbral eclipse. 






About the graphic designer:
Ethan Gevinson is a senior at McLean High School. He has always had a passion for graphic design and has had his work displayed at a variety of art installations. Ethan is a level 9 competitive gymnast and a varsity cheerleader. Additionally, Ethan is a dedicated gymnastics and cheer coach. He plans to major in graphic design and participate in division 1 competitive cheer next year in college. He intends to major in graphic design and ultimately pursue a career in that field. 

About the Author

Alessandro Farruggio

Alessandro Farruggio is a senior at McLean High School and will be attending Embry-Riddle in the fall pursuing degrees in Aerospace Engineering and Astronomy. He has worked for several years in the University of Virginia’s Virginia Cooperative Autonomous Robots Lab where he was apart of a project for the Office of Naval Research designing autonomous vehicles for the inspection and maintenance of Naval ships, designing and programming a drone. Additionally, he is the president of the physics tutoring club at his high school. In his free time, he likes to pursue many hobbies including riding motorcycles, snowboarding, and astrophotography. He intends to work at the forefront of space exploration and if possible become an astronaut.