Distant Moon

Author
by Wayne
Publish date
20 February 2012
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Comments (2)

Your Question: Is the Moon getting further away?

The short answer is yes, the Moon is getting further away - it is retreating from Earth by 3.8 cm per year.

Close-up of Planet Earth with Moon in background Close-up of Planet Earth with Moon in background
Image: NASA, JPL
Source: NASA, JPL
 
The history of the Moon gives us clues about its future. Over 4.5 billion years ago, a planet-sized body collided with a young Earth. Although most of the impact was absorbed into the still-molten Earth, the collision threw debris into space. A large section of this debris solidified in orbit around Earth and formed our Moon. The Moon has been slowly getting further from Earth since then.

Astronaut Buzz Aldrin on the Moon Astronaut Buzz Aldrin on the Moon
Image: NASA
Source: NASA
 
If we were to fast-forward from the impact event to about 1.2 billion years ago (over 3 billion years after the Moon formed), the Moon was still relatively close to Earth; much more so than it is today. As a result, the Moon’s gravitational effect on Earth was greater, and the tides were 20 per cent stronger than they are today. The Moon would have appeared much larger in the sky, although there was no life on earth equipped to see it.

Earth as seen from the Moon, Apollo 8 Mission Earth as seen from the Moon, Apollo 8 Mission
Image: NASA
Source: NASA
 
If we fast-forward again, this time 600 million years into the future, the moon will have less influence on Earth - ocean tides will be significantly weaker. From Earth the Moon will appear tiny by today’s standards and events like eclipses will no longer be visible.

Got a question? Ask us!

Links:

Moon rocks land at Melbourne Museum

Dynamic Earth: How the Moon formed

Comments (2)

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Pat B 20 February, 2012 16:51
Great, so first New Zealand is getting closer and now the moon is getting further away... Not sure if I'm happy about that.
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Sarah G 22 February, 2012 15:26
How amazing that humankind is around at this point in spacetime to witness eclipses, where the relationships between the distance and size of the sun and moon, play out in such perfect harmony.
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