MNN - Mother Nature Network

The supermoon is coming! The supermoon is coming! But what exactly does that mean? Are the Internet rumors of doom and gloom to be believed? Will the moon steal my children? And why the fuss? Read below as I dissect the semi-rare celestial event known as the supermoon — and why this weekend's nighttime event is one worth catching.

 

Since its 27.3-day orbit is elliptical, the moon alternates between its farthest point (254,000 miles) and closest point (220,000 miles) roughly every two weeks. What makes the moon a supermoon is when at its closest approach, it also happens to be a new moon or full moon.

 

As Fast Company notes, the March 19 moon will be a supermoon because "the crest of the moon’s full phase comes within an hour of the moon’s closest point to Earth."

 

Steve Owens at Dark Sky Diary adds that the moon will be about 8 percent closer to Earth than usual, and about 2 percent closer to Earth than the average lunar perigee. In fact, it'll be the closest positioning since 1992.

 

According to scientists, not much. Anytime there is a full moon — when the Sun, Earth and Moon are near a straight line in space — the gravitational effects on the ocean tides is greater. When a supermoon is in play, these forces are exaggerated. That being said, the force at this maximum is considered too weak to be of great consequence.

 

Said John Vidale, a seismologist at the University of Washington in Seattle, "Practically speaking, you'll never see any effect of lunar perigee," he told Life's Little Mysteries. "It's somewhere between 'It has no effect' and 'It's so small you don't see any effect.' "

 

The only concern should be for those near the coast looking to take advantage of lower-than-normal seas. As an example, the Irish Water Safety body has issued a warning urging people to avoid "becoming stranded whilst walking or picking shellfish on our beaches over the weekend." Should a storm also roll along a coastline during a supermoon, there's the possibility of increased flooding because of the tides. It's worth taking precautions during an event like this should such a combo of factors hit.

 

Some studies have shown a weak correlation between increased lunar activity and shallow, low-intensity earthquakes — but nothing on the scale that Japan experienced last week.

 

It's also worth noting that when the earthquake struck on March 11, the moon was actually closer to its farthest point (called apogee) than its closest (perigee). The same holds true for the Indian Ocean tsunami in 2004, which some have also blamed on the supermoon.

 

Yes and no. The moon is actually being "pushed" away from the Earth at a rate of 1.6 inches annually. Several billion years from now, astronomers predict that the moon's orbit around the Earth will take 47 days, rather than the current 27.3.

 

However, another more dramatic event could take place that would position the moon within a sky-filling 11,470 miles above the planet, termed the Roche limit. This would only happen if the sun mutated into a red giant, causing the moon's orbit to decay. Of course, life would cease to exist on the planet in this stage, so this "Mother of all Supermoons" would not be much of a concern.

 

Hopefully you've got clear skies — but that's never a good bet for March. To find out exactly when the supermoon will come into view for you, check out this handy chart over on 40-Below.com. You can also grab the latitude/longitude data for your city to get more accurate info here.

 

The next supermoon will occur on Nov. 14, 2016.