‘Supermoon’

It may not be faster than a speeding bullet, but Saturday the moon made its closest approach to Earth in 18 years - making the so-called supermoon the biggest full moon in years.

Despite Internet rumours, the phenomenon had no influence on the March 11 Japan earthquake and tsunami.

The monthly full moon always looks like a big disk, but because its orbit is egg-shaped, there are times when the moon is at perigee - its shortest distance from Earth in the roughly monthlong lunar cycle - or at apogee, its farthest distance from Earth.

Likewise, because the size of the moon’s orbit varies slightly, each perigee is not always the same distance away from Earth.

Saturday’s supermoon was just 221,566 miles (356,577 kilometres) away from Earth. The last time the full moon approached so close to Earth was in 1993, according to NASA.

Though the supermoon was about 20 percent brighter and 15 percent bigger than a regular full moon, the visual effect may be subtle, added Griffith Observatory in Los Angeles astronomical observer Anthony Cook. “I doubt that most people noticed anything unusual about this full moon,” Cook said.

“Because the total amount of light is a little greater, the biggest effect was on the illumination of the ground - but not enough to be very noticeable to the casual observer.” Such a lunar close encounter can cause slightly higher than normal ocean tides and localized flooding - especially if there is already a storm surge, astronomers say.

A supermoon may even have some impact on seismic activity because of the stronger gravitational interaction between the moon, the sun, and Earth.

Even so, there is no clear evidence that any of these phenomena influenced the Japan earthquake and tsunami.

- National Geographic