Why is the moon red during a total eclipse?

Written By رنا السيلاوي on 2021/05/28

This article was written originally in Arabic and is translated using a 3rd party automated service. ArabiaWeather is not responsible for any grammatical errors whatsoever.

Arab weather - the moon is an opaque planet that does not radiate light like stars, but we see it illuminate the sky of the earth because its surface reflects the light of the sun, and when the phenomenon of the total eclipse of the moon occurs, the planet is on one straight line between the sun and the moon, so the earth blocks the light of the sun from the moon, but during the eclipse Total Moon The surface of the moon glows a reddish or orange color instead of becoming completely dark. Why does this happen?

(Video of the phenomenon of the total eclipse of the moon and its transformation into red using time-lapse technology)

Why does the moon appear red during a total eclipse?

The red color in which the moon appears during a total eclipse has led many people in recent years to refer to a total lunar eclipse as a " blood moon . " The mechanism responsible for causing the colors to appear in the sky at sunrise and sunset, and to make the sky appear blue.

We will explain this phenomenon gradually, beginning with the nature of sunlight, then how it interacts with the Earth's atmosphere and produces colors.

colorful sunlight

Although sunlight may appear white to the human eye, it is actually made up of different colors called the colors of the visible spectrum. These colors can be seen through a prism or a rainbow. The visible spectrum consists of several colors, each with a specific wavelength and frequency. Colors towards the red part of the spectrum have longer wavelengths and lower frequencies compared to colors in the violet part of the spectrum that have shorter wavelengths and higher frequencies.

Earth's atmosphere

The next piece of the puzzle that causes the moon to turn red during a total eclipse is Earth's atmosphere. The air layer surrounding our planet consists of various gases, water droplets and dust particles, and when sunlight entering the Earth's atmosphere hits the small particles, it is scattered and scattered in different directions.

However, not all colors in the light spectrum are scattered equally. Colors with shorter wavelengths (especially violet and blue) are scattered more strongly than colors with longer wavelengths (such as red and orange).

What happens in a total eclipse is that when the earth is between the sun and the moon and blocks the sunlight from it, some of the sun’s rays pass and bend at the edges of the earth due to refraction through the layers of the atmosphere. Colors with longer wavelengths (red and orange) pass through the atmosphere, and reach the surface of the moon after they curve around the Earth, giving the moon the reddish-orange glow that a total lunar eclipse is famous for.

There is some blue light during a total eclipse

Seasoned eclipse watchers will tell you that if you look seriously at the beginning and before the end of the total phase of the eclipse, you might spot a bright blue or turquoise band on the moon's face (see image). This happens because the ozone layer on Earth dissipates red light and lets through some of the blue light that is otherwise filtered by other layers of the atmosphere.

(Light blue bar visible on the moon's surface)

The red gradations that appear on the face of the moon during the eclipse

The moon can take on various shades of red, orange, or gold during a total eclipse, depending on the conditions of Earth's atmosphere at the time of the eclipse. The amount of dust particles, water droplets, clouds and fog can have an effect on the red color, and the presence of volcanic ash and dust in the atmosphere can darken the color of the moon during an eclipse.

Brightness meter

Scientists measure the appearance and brightness of a total lunar eclipse using a five-point scale - from 0 to 4 - called the Danjon Scale (see image). Lunar eclipses are classified and assigned a value on the scale. The following is an illustration of the color gradations of the moon during the eclipse, according to the Danjon scale, which was created by the French astronomer André-Louis Danjon

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Watch the video | This is the difference between a solar eclipse and a lunar eclipse