Fri May 04 2012 22:58
This Saturday evening, take a look at the night sky and you might see something special. The moon will make its largest, most stunning appearance of the year—an event known to scientists as “the perigee-syzygy of the Earth-Moon-Sun system” and to the popular skywatching public simply as the “supermoon.” As one of the most spectacular supermoons in years, the moon will appear 14 percent bigger and 30 percent brighter than when it is on the far side of its orbit.
Apart from providing a sight to behold in the night sky, the moon’s perigee also has a tangible effect on Earth: It causes higher than normal tides. Because tides are driven by the moon’s gravitational effects, a closer moon means that the oceans will be pulled more than usual towards the satellite. In most places, this will mean a tide that is an inch or so higher than usual, but geographical factors can multiply the effect up to around six inches.
There has long been speculation that the moon’s gravitational effect during its perigee could be the cause of natural disasters, including earthquakes and volcanic activity. In particular, many suggested this link following the earthquake and subsequent tsunami off the coast of Japan in March of 2011. However, the devastating quake occurred over a week before the supermoon, and studies have shown no strong evidence for increased frequency of high-intensity seismic activity during the moon’s perigee.