occurs when the alignment of the Sun and Moon coincides with the Moon's closest approach to the Earth. According to Space.com
, Richard Nolle, the astronomer who coined the term "supermoon" defines it as "a full Moon that occurrs within 12 hours of lunar perigee." A perigee
is the point in the Moon's elliptical orbit when it comes closest to our planet.
reports that on Saturday, the Moon will reach its perigee distance of 221,802 miles (356,955 kilometers) at 11:34 p.m. Eastern Time, and it will fall in line with Sun just a minute later. The result will be a "supermoon" that will appear larger than that of March 16, 2011, when perigee and full Moon were 50 minutes apart.
According to NASA
, on Saturday night, the Moon will appear 14 percent bigger and 30 percent brighter than normal. When we see the full Moon rising over the horizon from the east, it looks enormous compared to when it is overhead. NASA
says this is only an optical illusion and that the apparent size of the rising Moon is the same as the apparent size when the Moon is overhead. According to NASA
: “For reasons not fully understood by astronomers or psychologists, low-hanging Moons look unnaturally large when they beam through trees, buildings and other foreground objects. On May 5, this ‘Moon illusion’ will amplify a full Moon that's extra-big to begin with.”
NASA: 'No apocalypse on Saturday'
Astronomers reassure that beside the spectacle, Saturday's supermoon incident will pass as it did last year, without any apocalyptic event, namely, earthquakes, volcanic eruptions or other catastrophic events as some doomsday prophets are predicting online. Space.com
reports that seismologists say there is no evidence that supermoons trigger increased seismic activity above the level at a normal full Moon.
explains: It's true that a perigee full Moon brings with it extra-high 'perigean tides,' but according to the National Oceanic and Atmospheric Administration this is nothing to worry about. In most places, lunar gravity at perigee pulls tide waters only a few centimeters (an inch or so) higher than usual. Local geography can amplify the effect to about 15 centimeters (six inches)--not exactly a great flood."
The gravitational pull of the Moon on the Earth causes the ocean tides and even "land tides" or "solid Earth tides." The tides, according to astronomers, are greatest during full and new Moons when the Sun and Moon are aligned either on the same or opposite sides of the Earth.
reports that John Vidale, a seismologist at the University of Washington in Seattle, and director of the Pacific Northwest Seismic Network, explained that relatively dramatic land and ocean tides do occasionally trigger earthquakes. He explained that "both the Moon and Sun do stress the Earth a tiny bit, and when we look hard we can see a very small increase in tectonic activity when they're aligned." He explained that during full and new Moons "you see a less-than-1-percent increase in earthquake activity, and a slightly higher response in volcanoes." He said, however, that the extra gravitational pull at lunar perigee is not significant enough to cause a measurable increase in the likelihood of natural disasters.
According to Space.com
, John Bellinke, geophysicist at the U.S. Geological Survey, said: "A lot of studies have been done on this kind of thing by USGS scientists and others. They haven't found anything significant at all."
explains that last year's magnitude 9.0 earthquake and tsunami in Japan (March 11) had nothing to do with the perigee Moon that occurred on March 19.
Vidale said: "The stresses driving earthquakes are orders of magnitude larger. Decades of earthquake records show at best a minuscule influence of tides on the times of earthquakes. No extra fear of earthquakes is warranted during a 'supermoon', although a healthy respect for their destructive power is appropriate at all times."
It isn't only recently that people have associated full Moons and supermoons with disaster and misfortune. The word "lunacy" comes from the idea of the full Moon as portent. NASA
says folklore holds that "all kinds of wacky things happen under the light of a full Moon. Supposedly, hospital admissions increase, the crime rate ticks upward, and people behave strangely. The idea that the full Moon causes mental disorders was widespread in the Middle Ages. Even the word 'lunacy,' meaning 'insanity,' comes from the Latin word for 'Moon.'"