Moonageddon: Apocalypse not - By Carl Holm for ABC Science Online

Updated Fri Mar 18, 2011 8:21pm AEDT

A full moon sets over the European Southern Observatory's Very Large Telescope (ESO: G. Gillet)

Romantics, werewolves and other moon-gazers are in for a treat this weekend as they witness the biggest full moon seen in nearly 20 years.

But experts are discounting predictions of earthquakes associated with the event.
The moon's orbit is elliptical, and as it follows its path one side of the ellipse, known as perigee, passes about 50,000 kilometres closer than the on the other side - apogee.
A perigee full moon appears around 14 per cent bigger and 30 per cent brighter than an apogee full moon.
Geoffrey Wyatt from the Sydney Observatory says the upcoming full moon - which NASA's website says will be of "rare size and beauty" - will rise about 08.00 pm (AEDT) on Saturday.
But it becomes full on Sunday morning at 05.10 am (AEDT), one hour before lunar perigee.
"So, Sunday morning, those people who are up early or getting home super late, look to the west and you'll see the biggest moon for 18 years," Mr Wyatt said.
The last time the full moon was so big and close to Earth was in March 1993.
"You've got two cycles here. You've got 29-and-a-half days between full moons and then you've got 27 and a half days from apogee to apogee," Mr Wyatt said.
"That difference builds up and although you get a perigee every month, to get it at minimum distance takes about 18 years."
Perigee full moons also usually bring extra-high tides, but Daniel Jaksa, co-director of the joint Australian Tsunami Warning Centre, says they will probably be a fraction of one per cent higher than normal.

Earthquake predictions

Meanwhile an Auckland-based mathematician known as the "Moonman", Ken Ring, has warned the perigee moon will cause another major earthquake in Christchurch, New Zealand.
Mr Ring claims he predicted Christchurch's deadly February 22 quake by studying the moon.
But Mr Wyatt says he would like to see some scientific proof to back the Mr Ring's claims.
"For a few weeks now we've been hearing people talk about 'Moonageddon'," he said.
"It's depressing to hear people saying this sort of thing. There is absolutely no evidence for a causal link between the phases of the moon and earthquake activity.
"It's something you might find in 'Tom's Backyard Mechanic's Book of Celestial Tomfoolery', but you're not going to find that in peer-reviewed journals."
Mr Jaksa agrees.
"You only have to look at the major energy source that's driving the tectonic process and it's not the moon," he said.
"It's the convection currents in the mantle as the Earth tries to cool down from its core outwards that drives plate tectonics."
Mr Wyatt says the claims are a symptom of the human condition.
"People blame things on the alignment of the planets because they want an explanation, but it's not the moon's fault," he said.