Don't expect lunar drama on supermoon Saturday

The full moon on Saturday night will be closer in its earth orbit than it has been in 18 years.

The popular press is calling it the "supermoon."

"I've done amateur astronomy for half a century, and I never heard about supermoon until about a week ago. It's not a commonly used term in astronomy," said Dave Chapman of the Royal Astronomical Society.

There is talk of all the influences that it could have on Earth but scientists say those expecting lunar drama are going to be disappointed.

Chapman said the idea that the supermoon can cause earthquakes, tsunamis or other catastrophes is bunk.

"Its origin is with an astrologer who coined this phrase and is trying to make the case that large appearing moons in the sky are somehow connected with natural disasters. There's no mechanical explanation on why that would be and when you do a rational analysis of all the data of the earthquakes and such and correlate them with moon phase, there's zero correlation."

The occurrences, technically known as lunar perigees, were previously visible in 1955, 1974, 1992, 1993 and 2005. But what makes this one particularly special is that it coincides with a full moon, which hasn't happened since 1993.

He said it will be hard to tell the difference in the size of the moon in the sky because there is nothing with which it can be compared.

"However, if you happen to see the full moon rise at sunset, then the bigger moon, coupled with the usual horizon effect of a full moon will make it look unusually large," said Chapman.

Phil McAulley studies tides and wave action in real time at the Bedford Institute of Oceanography, using sensors put in place by the Canadian Hydrographic Service. He said the new moon will influence tides as the moon always does.

"What you will see is a fairly large tide but it is no larger than the coastline is accustomed to," said McAulley.

If there are clear skies Saturday night people will be able to see the supermoon, but it's not going to be much bigger than a normal full moon. People will be able to see robust tides, but they will only be a couple of centimetres bigger than average high tides.