People all over the world stepped outside for a few moments on the night of July 27th hoping to catch a glimpse of the "Blood Moon," the longest lunar eclipse that will occur in this century. Although it was only visible for 1 hour and 43 minutes, the moon spent a total of 3 hours and 54 minutes in Earth's shadow, giving it a red hue as it moved across the sky.
Similar to its appearance, the cause of this change in color is quite elegant. "It's called a blood moon because the light from the sun goes through the earth's atmosphere on its way to the moon, and the earth's atmosphere turns it red in the same way that when the sun goes down it goes red," says Andrew Fabian, an astronomy professor at the University of Cambridge.
In fact, when the sun's light passes through Earth's atmosphere, every color is emitted from our planet. The sun's projection of white light (light containing fragments of every visible color) is dissipated by Earth on its way to the moon and sent back out into space. However, the long wavelengths of the red light cause it to be "bent" and ultimately directed straight back towards the moon. This is also why the moon may have appeared to have an orange or yellow tint to some, as these colors are close to red on the spectrum.
Although there will be about 230 lunar eclipses (the passing of the moon behind the Earth) throughout the twenty-first century, the one that occurred on July 27th, 2018 will be the longest and most visible. This is because due to the moon's tilted orbit, it will spend the most time in the Umbra (Earth's shadow) on this night.
Even the chemists at NASA can jump for joy when the blood moon comes out of hiding, as the lack of sunlight directed at the moon causes the rocks on the surface to freeze and crack, ultimately releasing gas and providing scientists with new data for further research. As hotspots for modern cosmic exploration, blood moons continue to provide us with new information to help us better understand celestial phenomena.
Despite the fact that we will not get to experience the full blood moon again until the year 2132, the awe-inspiring photos and sense of unity from the night of July 27th are truly a gift.