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What Causes a Blood Moon?

There is a lot of myth and legend behind a Blood Moon. It is sometimes associated with rituals and witches, but the science behind a Blood Moon is actually quite simple. So, you may ask, what causes a blood moon?

First, you need to identify a Blood Moon, which is very simple. When looking at a blood moon, you can see that the moon has a copper or reddish appearance, hence making it a “blood” moon.

Blood Moons happen during a total lunar eclipse. This occurs when the Earth moves between the Moon and the Sun, casting a large shadow on the Moon, putting the Moon in darkness. Total lunar eclipses occurs when the Moon happens to be in a Full Moon stage. This means the Sun, Earth, and Moon are in an exact, straight line–None of them are slightly off or in a different plane.

Despite the fact that the Earth is casting a shadow on the Moon during the total lunar eclipse that occurs during a Blood Moon, we can still see the Moon. We can see the moon because the Sun is still shining and beams of light bend around the Earth. In fact, our atmosphere bends light so that some of the Sun’s light is being directed towards the Moon’s surface.

While the sunlight passes through the Earth’s atmosphere and gets bent, the light gets filtered and scattered. The shorter light wavelengths get refracted and directed towards the Moon. Unsurprisingly, these shorter wavelengths are primarily orange and red in color. Therefore, as seen from Earth, our pale moon suddenly reddish or copper.

What you may not know is that the same process that causes scattered light to turn the Moon red for the Blood Moon also gives our sunrises and sunsets that same reddish glow as well. The cause of the red coloring is just the way in which light scatters and how we see it as humans.

Blood Moons happen about twice a year. While this may be exciting to most, you may not be able to see the Blood Moon. Depending on the angle and position of your location, the Moon may not appear as red, or you may not be able to see it. For instance, the Blood Moon on July 27, 2018 will not be visible from North America.

Blood Moons are beautiful to see and exciting to watch, but they are not products of superstition and witchcraft. If someone ever wonders what is happening during the Blood Moon, you can simply tell them that a total lunar eclipse is happening. The Blood Moon looks red from light being scattered from the atmosphere and directed towards the surface of the moon. A Blood Moon is a total lunar eclipse that is being lighted by redirected sunlight.