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Via wikipedia
http://en.wikipedia.org/wiki/File:Supermoon_comparison.jpg |
I have been a little tardy in getting to the subject of the "
supermoon".
The United States Naval Observatory (USNO) says that the full moon occurs on May 6, 2012 at 03:35:00 UTC. Since Boston is currently at
UTC minus 4 (Eastern Daylight Time), the full moon happened at 11:35 last night.
Apparent Size Change
The distance change from average orbital radius to perigee (closest approach) is about 6%. The moon is not a point source when viewed from Earth so we see an apparent change in size (about 6% in diameter and 12% in area). (see image on right). If a far away, "point source", like a star, got 6% closer to us, we would not see any size change - only a change in apparent brightness.
Apparent Brightness Change
In addition, light from each location, or point, on the moon spreads out in all directions. Since the light from each point travels a shorter distance to earth, the famous
inverse square law says that detector (eye) would receive about 12% more light, from each point on the moon, due to the change in distance. With an imaging detector like the eye, or a camera. each point on the film or retina receives more light independent of the size of the moon. This change is unlikely to be perceived as a big change brightness of the moon but it may add to the overall effect of a "super moon" , or supermoon.
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