You may have heard that the Moon is slowly moving away from the Earth.  Following up on last week’s episode of Sciency Words, does this mean the Moon will one day become a ploonet: a moon that’s escaped its original orbit and become a planet in its own right?

Currently, the Moon is receding from the Earth at a rate of approximately 4 centimeters per year.  Simultaneously, and not by coincidence, Earth’s rotation rate is slowing down.  The exact reasons for this are, I admit, too math-heavy for my artistic/writerly brain to comprehend, but it has something to do with tidal forces and the exchange of angular momentum.

As explained in this article from Universe Today:

The same tidal forces that cause tides on Earth are slowing down Earth’s rotation bit by bit.  And the Moon is continuing to drift away a few centimeters a year to compensate.

And as further explained in this article from Futurism:

As is true of many rocky relationships, the Earth and Moon only need a bit of time and space to work things out.  Ultimately, we just need to be patient.  In about 50 billion years, the Moon will stop moving away from us and settle into a nice, stable orbit.

So in the very, very, very distant future, assuming the expansion of the Sun doesn’t destroy us first, Earth and the Moon will achieve a new balance.  Earth’s day will be considerably longer, and the Moon will be considerably farther away.  Also, just as the same side of the Moon always faces the Earth, the same side of Earth will always face the Moon.

But the Moon will still be a moon.  It will not become a ploonet.

8 responses »

  1. That’s a relief.

    Now if we can only do something about those red giant and white dwarf phases…

    Liked by 2 people

  2. Spacer Guy says:

    tidal forces and the exchange of angular momentum…….duh duh duh what? thinking about this makes me believe its about time I got my brain amputated 🙂

    Liked by 1 person

  3. Fran says:

    I think I see why it’s slowing down. You know how ballerinas pull their arms in when spinning? They do that to keep spinning and it also makes them spin faster. I think it’s basically the same, but in reverse. Don’t quote me though, I’m not a physicist (yet)!

    Liked by 2 people

  4. Ggreybeard says:

    Some might argue that we actually live in a double planet system – but I expect the IAU would find a definition to refute it.

    Liked by 1 person

    • J.S. Pailly says:

      If memory serves, the IAU did consider adopting binary planet as an official term. It would have applied to the Pluto/Charon system and also the Earth/Moon system. But they rejected that proposal and adopted the whole dwarf planet thing instead.

      Like

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