Shrunk and gone: a story about the Moon

Have you ever seen the Moon low in the horizon, when it is just rising? Do you remember how big it looks at that moment and how it seems to have shrunk when it is high in the sky? Well, even if this phenomenon is caused by an optical illuson, our natural satellite is actually shrinking.

 Photograph by Justo Ruiz.

The Lunar Reconnaisance Orbiter (LRO), an artificial satellite launched on June18th, 2009 by the US's National Aeronautics and Space Administration (NASA) to study the Moon discovered what have been called lobated scarfs, a type of cliffs caused by the Moon's shrinkage.

The data obtained by the LRO shows that the Moon has reduced its radius in 100 m during a yet indetermined time span -it may go from one hundred thousand (1 x 10⁵) to one billion (1 x 10⁹) years. Yet, the Moon's shrinkage, caused by the cooling of its is interior, is not affecting its crust as it is already cold, thus causing this one to wrinkle. This is, roughly, how the lobated scarfes are originated.

Graphic showing how lobated scarfs are created, as the Moon's crust is pushed together due to our natural satellite's shrinkage. Image by NASA.

So, the Moon is shrinking, but is still ours, as always, right? Well, not forever, because the Moon is actually moving away from us and will eventually be gone forever.

The gravitational interaction between the Earth and the Moon that is responsible for the tidals of our seas is causing our natural satellite to be 3,8 cm farther away from us and is accelerating its revolution time around our planet to compensate this fact.

So, the Moon will look smaller and smaller each year in the sky and someday, in a very distant future, it won't be there no more. Don't believe me? Just watch:

Now, here's the explanation on why this is happening:

More information on the shrinking Moon can be found here.