by When a lunar eclipse occurs and our lone satellite enters Earth’s shadow, the face of the moon turns red.
Although this red hue is most striking during a total lunar eclipse, the moon casts a scarlet light even during partial lunar eclipses. So why does our moon turn red and not black when it’s bathed in Earth’s shadow?
For example, the only Lunar eclipse visible in North America this year occurs on May 15 or 16, depending on your location. For some viewers, they’ll see a total lunar eclipse on May 15, while others will see the moon move toward the edge of Earth’s shadow for a penumbral lunar eclipse. When the moon begins to pass into the central part of Earth’s shadow, called the umbra, that’s when the fiery glow stands out.
“When the moon is inside the umbra, it will turn a reddish hue. Lunar eclipses are sometimes called ‘blood moons’ because of this phenomenon,” NASA said.
Related: How to watch the total lunar eclipse of May 2022 online
As for why the moon looks red, it has to do with the way light is scattered. A phenomenon called Rayleigh scattering causes some wavelengths of light to scatter more than others. Specifically, the wavelengths of light scatter most of the tiny particles that are about a tenth of those wavelength of light or smaller.
During a total lunar eclipse, the sun, land and the moon are perfectly aligned so that our Blue Planet prevents the sun’s rays from hitting the moon. Although the Earth is much larger than the sun, light rays can bend around the edges of our planet before reflecting off the moon. Still, sunlight passes through Earth’s atmosphere first; and during that journey, particles in the atmosphere preferentially scatter the shorter-wavelength blue light. That way, longer wavelength orange and red light bathe the moon’s surface.
Perhaps counterintuitively, this phenomenon also explains why the sky is blue. During the day, light waves from the sun, which are made up of a band of colors corresponding to their individual wavelengths, are filtered through our atmosphere, where tiny molecules of nitrogen and oxygen gas allow wavelengths to pass through. longer, such as reds, oranges and yellows. pass directly to the ground (losing our line of sight). But shorter wavelengths, like violets and blues, are absorbed and then scattered in all directions, giving them a better chance of reaching our eyes.
The moon will change various shades during the different stages of a total lunar eclipse, transforming from an initial gray to orange and amber. Atmospheric conditions can also affect the brightness of colors. For example, extra particles in the atmosphere, such as ash from a large forest fire or a recent volcanic eruption, can make the moon appear a darker shade of red, according to NASA.
The moon doesn’t always hide completely behind Earth’s shadow. During partial lunar eclipses, the sun, Earth, and moon are slightly off in their alignment, so our planet’s shadow envelops only part of the moon.
A novice sky watcher might not even notice the third type of lunar eclipse, the penumbral type, in which the moon is in Earth’s penumbra, or in its faint outer shadow.
The next two total lunar eclipses will occur on May 16, 2022 (visible in the Americas, Europe, and Africa), followed by one on November 8, 2022 (visible in Asia, Australia, the Pacific, and the Americas). according to nasa.
Editor’s Note: This article was first published in 2016 and has been updated for the 2018, 2021, and 2022 Super Blue Blood Moon Lunar Eclipse.
Original article in Living Science.
