Thursday, March 17, 2011

3-17-11 Super Moon is coming!


By Dave Cocchiarella, Meteorologist 
Last Updated: Thursday, March 17, 2011 9:06 PM
It’s not Super Bowl Sunday, but Super Moon Sunday. Actually the big event will really happen on Saturday, but you can enjoy the lunar illusion all weekend long. 
The super moon event is said to occur between March 16 and March 22 with the full moon being closest to Earth than any time in the past 18 years on March 19. 
Celestial bodies do not orbit in perfect circles as the earliest scientist thought. Johannes Kepler showed us in 1609 that planets and moons sweep out their orbits in ellipses. This means that at some points in their orbits they are closer to the body they orbit than other points. Whenever a celestial satellite is at its closest point, it is known to be at perigee and when it is at its furthest point from the body it orbits, it is at apogee. 
Even though this Saturday’s full moon occurs within an hour of the perigee (an event that only happens every 18 years), the satellite is still 356,577 kilometers away from Earth, only about 8% closer than its average distance from Earth. This full moon at perigee is a super moon and will appear about 14% bigger and 30% brighter than lesser moons that occur on the apogee side of the moon's orbit.
The best time to look is when the moon is near the horizon at moon rise in the east and moon set in the west. When the moon is near the horizon, illusion mixes with reality to produce an amazingly large view of the moon. For reasons not completely understood by scientist, moons hanging just above the horizon look unnaturally large when they are seen between trees, buildings and other foreground objects.  
Check out Saturday morning’s moon set, but do it before it hits the horizon at 7:04 a.m., the actual full moon will occur during the daylight hours on Saturday, so the next best time will be right around 8 p.m. on Saturday after the moon rise. Sunday morning before daybreak will also afford a quality view, but by Sunday evening the moon will be starting its trip back toward apogee.
A perigee full moon brings with it extra-high "perigean tides," but this is nothing like the natural disasters predicted by internet doomsayers.  The only impact of a slightly closer moon, will be slightly higher tides. In most places, lunar gravity at perigee pulls tide waters only about an inch or so higher than usual. Local geography can amplify the effect to about six inches, but East Central Florida’s beaches will barely notice the difference.


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