A supermoon occurs when a full moon coincides with the moon's perigree -- the point in the lunar orbit when it's closest to the Earth -- making it appear larger and brighter than normal.
A lunar eclipse, meanwhile, happens when the moon passes into alignment with the Earth and sun and briefly falls into Earth's shadow. During a total lunar eclipse, the moon often turns a reddish color when it's hit by sunlight bent by the Earth's atmosphere, resulting in a phenomenon called a "blood moon."
It's extremely unusual for a supermoon and total lunar eclipse to happen at the same time.
Unlike a solar eclipse, which is dangerous to look at with the naked eye, experts say it's perfectly safe to watch a lunar eclipse.
During a Lunar Eclipse the Earth will slide precisely between the sun and the moon, throwing the satellite into a rusty red shadow.
When a total lunar eclipse coincides with a supermoon, when the moon’s mostly elliptical orbit brings it closest to Earth’s surface—about 220,000 miles away instead of its average 240,000 miles, the moon will appear about 14 percent larger and 30 percent brighter than Earthlings are used to seeing it.
And yes, it’ll also change color. The Earth doesn’t totally shade the moon; some sunlight trickles around the edges of the planet and gets filtered through the atmosphere, which only lets through light with longer wavelengths. That’s red.
A lunar eclipse gives night owls everywhere a reason to look up in wonder, but not everyone thinks a "blood moon" is a harmless celestial event. Some folks see it as a sign of impending doom.
Some doomsayers suggest that the reddish moon could bring about the end of the world — an idea sometimes referred to as the "blood moon prophecy."
If you're shaking your head right now (either in agreement or utter disdain) consider this: The blood moon prophecy has a logical scientific explanation.
Blame evolution
Superstitious beliefs and rare celestial events go hand in hand, said Allen Kerkeslager, an associate professor in the Department of Theology and Religious Studies at Saint Joseph's University in Philadelphia.
"'Why?' is almost irresistible to a brain with an evolutionary history that is simultaneously so similar to all other advanced mammals and yet just enough greater in the complexity of its memory systems to allow us to remember, reflect on and extrapolate meanings and intentions that go beyond what other mammals could conceive," Kerkeslager told Live Science in an email.
In other words, although your dog won't think a supermoon eclipse is happening for any particular reason, it's perfectly natural for you to wonder why it's occurring, and quite logical that some people attribute some kind of meaning to the event.
Humans' tendency to believe that everything has some kind of intention or purpose is one of the reasons humanity didn't die off long ago, according to cognitive scientists, some of whom call this tendency the "hypersensitive agency detecting device," or HADD. Early humans who attributed "agency," or intention, to the things that might help them (a mate or a tasty-looking antelope, for instance) or things that might harm them (perhaps a lion or a guy with a club), were the ones who survived long enough to spread their genes on to the next generation, Kerkeslager explained.
When a rare phenomenon occurs, such as a blood moon total lunar eclipse, it's hard to resist what Kerkeslager calls the "evolutionary tendency to try to explain this as the result of some kind of intentional action by some personal agent."
But there could be another explanation to attribute meaning to the supermoon eclipse. It's what Lorenzo DiTommaso, a professor of religion at Concordia University in Montreal, calls the "apocalyptic worldview."
The apocalyptic worldview has gained popularity in the past 40 to 50 years, DiTommaso told Live Science in 2011. Its rise is linked to the belief that the world's problems are too big for humans to solve, he said.
"Problems have become so big, with no solutions in sight, that we no longer see ourselves able, as human beings, to solve these problems," DiTommaso told Live Science. Some suggest from a biblical point of view, God is going to solve them. How by using a sort of catastrophic event. To solve the world's problems, God will destroy the world.
There will be blood
Just what the big event will be isn't yet known, but it is somehow connected to the so-called "end times," or the end of the world as prophesied in most major world religions. Also unknown is when, exactly, the event that brings about the end of the world will take place.
Nothing special
Knowing what really causes a total lunar eclipse is one way to fight the evolutionary tendency to read too far into what is really just a random event, Kerkeslager said.
"A supermoon simply takes place whenever the full moon is near the perigee of the moon's orbit," said David Morrison, a senior scientist at NASA's Ames Research Center in Moffett Field, California. "Total lunar eclipses take place nearly once a year, on average," he told Live Science in an email.
There's also a scientific explanation for the "blood" part of the blood moon prophecy. When the Earth slides in front of the moon, sunlight will pass through Earth's atmosphere and bend toward the moon. Although most of this light will be blocked and scattered by Earth's atmosphere, red light may pass through, turning the moon crimson.
But other than these scientific explanations, the supermoon total lunar eclipse doesn't have any special meaning, Morrison said. That may come as a disappointment to those who hope an eclipse hints at some supernatural phenomenon. Still, you shouldn't let science deter your sky watching plans. A blood moon is sure to be "a beautiful sight," Morrison said.