Tonight, there is going to be a 'supermoon.' What is a supermoon, you ask? Well, contrary to common ignorance, it will not be the bringer of Earthly disasters disasters. Instead, the supermoon is just a Full Moon at/near its closest point to Earth in its orbit, a position called perigee.
So, fiction already addressed, what about the facts?
According to current scientific theory and shown plausible by computer models, our Moon probably originated in a massive impact between Earth and a Mars-sized body. In the crash, the impacting body was shattered and the outer layers if Earth were thrown into space. For a time, Earth was surrounded by a ring of debris, much like Saturn is today. However, unlike with Saturn, the floating bits of rock and metal reconstituted into a new world, our Moon. In time, thanks to its sheer mass, the Moon would start pulling away from Earth, a process that continues even today at a rate of about an inch a year.
As was first discovered in the early 1600s by Johannes Kepler, all orbiting bodies move in elliptical (slightly elongated) orbits, the Moon is no exception. The fact the lunar orbit is elliptical is the root of the whole 'supermoon' event that will happen today. Because of the elliptical orbit, the Moon is not always the same distance from Earth, but a varying distance that can change by as much as about 30,000 miles. Tonight, the Moon will come to a point in its orbit that will bring it very close to Earth, thus increasing its gravitational pull, albeit only slightly. This point is called perigee. In fact, Full Moon will occur only less than an hour after perigee is passed.
For astrologer (not astronomer) Richard Nolle, the fact that a Full Moon coincides with perigee makes it a 'supermoon,' even though there is nothing really unusual about the whole situation.
In practical terms, the fact that the Moon is closer than usual will not amount to much. In a telescope, however, things will be different. As seen in a telescope, the Moon will be noticeably larger than it is when it is full at apogee (the point in its orbit farthest from Earth), especially when put side by side in a composite photograph.
So, now that you know that there is nothing to fear from this tonight's Full Moon, go out and have a look instead of hiding in the basement.
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