<p>The Moon is receding from the Earth, at a rate of <a href="http://apps.usd.edu/esci/creation/age/content/failed_scientific_clocks/darwin_moon.html#:%7E:text=The%20recession%20of%20the%20moon,%2Fyear%20(Pogge%202005)." rel="nofollow noreferrer">about 4 cm per year</a>. We can currently see about <a href="https://earthsky.org/astronomy-essentials/how-much-of-the-moon-can-we-see-from-earth-lunar-libration#:%7E:text=Lunar%20libration%20reveals%2059%25%20of%20the%20moon%27s%20surface.,of%20the%20moon%27s%20back%20side." rel="nofollow noreferrer">59% of the Moon's surface</a>, from the Earth's surface.</p>
<p>Will the amount of the Moon's surface we can see from Earth change (significantly) as the Moon recedes?</p>

CC BY-SA 4.0
2020-08-10T15:33:43.507Z
Oh this is a very cool question; in addition to having to check how eccentricity is predicted to evolve, if one wants one can include finite distance effects (we can't see a full hemisphere if too close) and even consider views from opposite sides of the Earth (i.e. full moon near sunset at one place and near sunrise at another)
uhoh
CC BY-SA 4.0
2020-08-10T21:09:26.483Z
"Significantly?" How much of a change would you consider to be significant? Also, over what time span? It's going to be a while before the Earth's own rotation becomes tidally locked to the Moon's orbit.
Solomon Slow
CC BY-SA 4.0
2020-08-11T00:42:23.140Z
@SolomonSlow I don't understand what Earth's rotation becoming locked has to do with this question
uhoh
CC BY-SA 4.0
2020-08-11T03:19:17.610Z
I'd guess, as the Moon moves away from the Earth it's orbit will become more eccentric and we'll see more than 59%. This change is obviously going to be incredibly gradual.  In a billion years, the Moon will be maybe 10% further (based on 3.8 cm per year) and probably less than that due to the effect diminishing with distance. I suspect, the Laplace plane with continue to dominate the Moon's orbit, so greater solar perturbation and higher eccentricity. The math behind this stuff is hard. Loosely related:  https://astronomy.stackexchange.com/questions/36512/why-is-the-moons-orbit-so-complicated
userLTK
CC BY-SA 4.0
2020-08-11T12:12:26.163Z
@uhoh, What do you suppose supplies the energy that lifts the Moon out of Earth's gravity well (i.e., causes it to "recede from the Earth?") The answer is, tides. The tides on Earth gradually slow the Earth's rotation, and transfer kinetic energy to the Moon's orbit. https://en.wikipedia.org/wiki/Moon#Tidal_effects The Moon eventually would stop receding, and the Earth eventually would always present the same face to the Moon if not for the Sun, which is on-track to swallow up both the Earth and the Moon in about five billion years from now.
Solomon Slow
CC BY-SA 4.0
2020-08-11T13:28:27.210Z
@SolomonSlow okay that's much clearer.
uhoh
CC BY-SA 4.0
2020-10-22T12:08:22.373Z
See this: https://math.stackexchange.com/questions/1329130/what-fraction-of-a-sphere-can-an-external-observer-see
Nilay Ghosh
<the-moon><tidal-locking>
How much (more or less) of the moon will be visible as it recedes from the Earth?
costrom
# How much (more or less) of the moon will be visible as it recedes from the Earth?

(Asked by: username_0 on 2020-08-10)

The Moon is receding from the Earth, at a rate of [about 4 cm per year](http://apps.usd.edu/esci/creation/age/content/failed_scientific_clocks/darwin_moon.html#:%7E:text=The%20recession%20of%20the%20moon,%2Fyear%20(Pogge%202005).). We can currently see about [59% of the Moon's surface](https://earthsky.org/astronomy-essentials/how-much-of-the-moon-can-we-see-from-earth-lunar-libration#:%7E:text=Lunar%20libration%20reveals%2059%25%20of%20the%20moon%27s%20surface.,of%20the%20moon%27s%20back%20side.), from the Earth's surface.

Will the amount of the Moon's surface we can see from Earth change (significantly) as the Moon recedes?

**Tags:** the-moon, tidal-locking

> **Comments:**
> **username_1**: Oh this is a very cool question; in addition to having to check how eccentricity is predicted to evolve, if one wants one can include finite distance effects (we can't see a full hemisphere if too close) and even consider views from opposite sides of the Earth (i.e. full moon near sunset at one place and near sunrise at another)  
> **username_2**: "Significantly?" How much of a change would you consider to be significant? Also, over what time span? It's going to be a while before the Earth's own rotation becomes tidally locked to the Moon's orbit.  
> **username_1**: @username_2 I don't understand what Earth's rotation becoming locked has to do with this question  
> **username_3**: I'd guess, as the Moon moves away from the Earth it's orbit will become more eccentric and we'll see more than 59%. This change is obviously going to be incredibly gradual.  In a billion years, the Moon will be maybe 10% further (based on 3.8 cm per year) and probably less than that due to the effect diminishing with distance. I suspect, the Laplace plane with continue to dominate the Moon's orbit, so greater solar perturbation and higher eccentricity. The math behind this stuff is hard. Loosely related:  https://astronomy.stackexchange.com/questions/36512/why-is-the-moons-orbit-so-complicated  
> **username_2**: @username_1, What do you suppose supplies the energy that lifts the Moon out of Earth's gravity well (i.e., causes it to "recede from the Earth?") The answer is, tides. The tides on Earth gradually username_2 the Earth's rotation, and transfer kinetic energy to the Moon's orbit. https://en.wikipedia.org/wiki/Moon#Tidal_effects The Moon eventually would stop receding, and the Earth eventually would always present the same face to the Moon if not for the Sun, which is on-track to swallow up both the Earth and the Moon in about five billion years from now.  
> **username_1**: @username_2 okay that's much clearer.  
> **username_4**: See this: https://math.stackexchange.com/questions/1329130/what-fraction-of-a-sphere-can-an-external-observer-see  

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## 0 answers

