This is Scientific American 62nd Science.

I'm Julia Rosen.

Got a minute?

Every two weeks on the full and new moons, the sun, moon, and Earth fall along a nearly

straight line.

The combination of gravitational forces in this arrangement creates large swings in the tides.

But the celestial alignment affects more than the oceans.

It also tugs on Earth's crust, adding to the stress

on faults. This makes it more likely that major earthquakes will strike at these times,

according to a new study. The idea isn't new, but scientists have had a hard time

testing the earthquake tide relationship. For instance, three of the largest earthquakes

in recent years happened when tidal stress was high. But those big ones are rare and the link seems to break down

for smaller events.

So the researchers crunched a bunch of numbers.

By looking at more than 10,000 medium and large earthquakes,

they found that the proportion of large events

increased when tidal stress was high.

The results do not imply that every full or new moon will bring an earthquake, obviously.

What the findings mean is that high tidal stress

during newer full moons may up the chances

that an earthquake will grow bigger than it otherwise

might have been.

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