Moon and Regulus

A gravitational tug-of-war can really stir things up. A contest between Jupiter and its big moons, for example, has warmed the interiors of the moons. That’s created oceans of liquid water below the surface of some of the moons, and hundreds of volcanoes on another.

A recent study says Earth is being changed by a tug-of-war as well — between the Sun and Moon. Researchers say the back-and-forth could be responsible for the motions of the plates that make up Earth’s crust.

The gravity of the Sun stretches the Moon’s orbit, so it looks like a flattened circle. As a result, the Moon’s distance from Earth varies by almost 30,000 miles.

As the Moon moves back and forth, so does the center of gravity of the Earth-Moon system. Earth and the Moon both orbit that center point. It’s below Earth’s surface, but not at the middle of our planet. And as the Moon’s distance changes, so does the center of gravity.

The researchers say that, combined with other effects, that change is enough to fracture Earth’s crust, forming the plates. It may also contribute heat that helps keep the layers below the crust molten, allowing the plates to move across them.

The idea would fill in some gaps found in other explanations for the crustal plates. But it’s brand new, so it’ll take more work to either confirm it or put it down.

The Moon soars high across the sky tonight, with a prominent star close by: Regulus, the heart of the lion.
 

Script by Damond Benningfield