If the weather is good where you are, please, go out Tuesday night and gawk for yourself: A supermoon will be dominating the sky. It's the last of this summer's impressive run of three supermoons, and the final one of the year.
As the moon wheels around Earth every 28 days and shows us a progressively greater and then stingier slice of its sun-lightened face, the distance between the moon and Earth changes, too. At the nearest point along its egg-shaped orbit, its perigee, the moon may be 26,000 miles closer to us than it is at its far point.
And should the moon happen to hit its ever-shifting orbital perigee at the same time that it lies athwart from the sun, we are treated to a so-called supermoon, a full moon that can seem embraceably close — as much as 12 percent bigger and 30 percent brighter than the average full moon.
Some astronomers dislike the whole supermoon hoopla. They point out that the term originated with astrology, not astronomy; that perigee full moons are not all that rare, coming an average of every 13½ months; and that their apparently swollen dimensions are often as much a matter of optical illusion and wishful blinking as of relative lunar nearness.
New York Times
