It’s hard being a skeptic sometimes..
Today I saw a particularly silly story in the local Newspaper: “Supermånen Sprer frykt” or “Supermoon spreads fear”.

To sum it up, in 10 days the moon will be closer to the earth than it has been in 19 years.
The newspaper then goes on to list a bunch of conspiracy theory bullshit about several times when the moon has been at its closest to the earth, earthquakes/tsunamies/etc. occurred.

The moons orbit is not a perfect circle, so the distance from the moon to the earth varies between roughly 350’000 km and 400’000 km.

The moon’s effect on the tides is around 60-70% and the sun makes up 40-30%, so of course when the moon gets closer the tides get more extreme, and unless I made an error in the calculations below, the difference in gravitational force between the earth and the moon from when the moon is farthest away and closest should be 13.764%

= 13% difference

Update: It seems the formula I used above is the “shared” gravitational force between the earth and the moon, Phil plait comes up with a maximum 50% increase in the moons gravitational effect on the earth, which is a more useful number. Also he’s an astronomer, so I’d take his word over mine.. On anything but Star Trek trivia

When the moon is at it’s closest and at the same time line up with the sun, we get what’s called the Perigean spring time. In other words, a big ass tide

Earthquakes and statistics!

They also cited a professor in astronomy (they actually referred to him as professor in astrology, but later changed the article and deleted the comments pointing this out).

The paper suggests that earthquakes can be caused by the moon being to close to the earth (sounds like a 50′s sci-fi movie), but what I find quite surprising is the rather strange quote from the professor:
“I would be very surprised, if there was a really strong earthquake at this particular date”. and that while living in California, he witnessed an powerful earthquake on the day before a “supermoon”.

The USGS defines a strong earthquake as anything with a magnitude of 6.0 or above (Christchurch was 6.3). On average there 150 earthquake like this yearly.

So the chance for a strong earthquake to happen on march 19th, is 41%.

If we however include the day before and after, the chance increases to 79%.

If we where to include 2 days before and after, we’re up to 92%.

So it’s pretty certain that a big earthquake will take place on or around march 19th, and it’s pretty certain crazy doomsday nuts will say there is a connection between that statistically predicted earthquake and the evil moon. The chance of the quake hitting a densely populated area however is much smaller, so maybe the nuts won’t notice it

update 11.03.2011: As statistics predicted a large earthquake did occur. It did hit a densely populated area, and caused a huge tsunami that hit the northwestern coast of Japan causing massive damages and deaths

The newspaper actually takes this flawed thinking to a whole new level, posting a picture from a earthquake/tsunami in Indonesia, making the point that it “happened only 2 weeks before a supermoon” (oooouh spooky!!).

This is just moronic.. the chance of a strong earthquake being 2 weeks before or after a certain date is 99.999977369 %

Note: all my calculations are based upon dates of earthquakes being relatively evenly distributed through the year, as confirmed by USGS