The supermoon rising over the ancient Greek temple of Poseidon at cape Sounion, some 60 kms south of Athens. Due to an unexplained effect known as the "moon illusion," the Moon always appears larger near the horizon than it does higher up in the sky.
- [Aris Messinis/AFP/Getty Images]

The view of the Moon from Sydney, Australia. Space experts say we're more likely to observe that the Moon looks bigger than usual than we are to notice its extra brightness, since our eyes automatically compensate for the change.
- [Cameron Spencer/Getty Images]

The perigee moon, or supermoon, rises behind wind turbines on May 5, 2012 near Palm Springs, California.
- [David McNew/Getty Images]

This is how the Moon looked from Chevy Chase, Maryland. The view of the supermoon was obscured by cloud in parts of the US.
- [Mandel Ngan/AFP/Getty Images]

The view behind the cross of the Frauenkirche (Church of Our Lady) in Dresden, eastern Germany.
- [Robert Michael/AFP/Getty Images]

The supermoon seen from Mumbai, India.
- [Punit Paranjpe/AFP/Getty Images]

The perigee full moon occurs once a year. This NASA image shows last year's supermoon over the Lincoln Memorial in Washington D.C., on March 19, 2011.
- [NASA/Bill Ingalls/Courtesy]