RICHMOND, Va. (WTVR) – The “biggest” Full Moon of this year will occur this Saturday, May 5, 2012 at 11:34 p.m. EDT. On Saturday, the Moon will be closest to the Earth in its orbit, which is called the “perigee,” and thus appear ever-so-slightly larger to viewers on Earth. At a distance of 221,802 miles from Earth, this marks the closest approach to us as the Moon orbits around the Earth in an elliptical path, not an exact circle.
Here’s a rough sketch of the shape of that oval orbit (not to scale):
And here’s two images taken in 2007 showing the apparent difference in the size of the Moon from an observer on Earth, comparing perigee versus apogee.
NASA says the Moon will appear as much as 14% bigger at this perigee and also look as much as 30% brighter than other Full Moons of 2012. This slight difference in distance does not lead to any significant impacts on Earth (like extreme tidal events or earthquakes, as some legends claim). In most places, perigean tides on Earth will only be an inch or two higher than usual, which is minimal, according to NASA.
Although the Moon's difference in size may not be noticeable when it is high overhead Saturday night, if you look at the Moon at either its rise (about 7:53 p.m. EDT May 5) or set (about 6:18 a.m. EDT May 6), you'll see an optical illusion making the Moon appear much larger. This optical illusion happens when the moon is viewed low on the horizon along with other ground objects, like buildings and trees. Our human depth perception therefore "sees" the Moon as much larger than life!
Last year's "supermoon" was March 19, 2011.
CREDIT: Tim McCord, March 19, 2011, Entiat, Washington
BONUS: Click here to read our blog entry about last year's supermoon.
In case you're wondering when apogee will occur this year, it is November 18, 2012. The Moon will appear slightly smaller and dimmer to us on Earth.
Meteorologist Carrie Rose
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