# Does the Moon actually rotate? **URL:** \ **Category:** Cecil's Columns/Staff Reports\ **Created:** [December 22, 2010, 7:35pm UTC](https://boards.straightdope.com/t/does-the-moon-actually-rotate/565102 "2010-12-22T19:35:49Z")\ **Posts on this page:** 18\ **Page:** 1
**Author:** ![davekhps](https://avatars.discourse-cdn.com/v4/letter/d/a5b964/32.png) [@davekhps](https://boards.straightdope.com/u/davekhps)\ **Post date:** [December 22, 2010, 7:35pm UTC](https://boards.straightdope.com/t/does-the-moon-actually-rotate/565102/1 "2010-12-22T19:35:49Z")
[In response to this SD classic](http://www.straightdope.com/columns/read/429/why-does-the-same-side-of-the-moon-always-face-the-earth). Given that the Moon is locked with the Earth, is it true to say that the Moon rotates? I’m assuming the point of reference is the Sun. The Earth rotates when compared to the Sun, but does the Moon? It revolves around the Earth like a figure skater, exposing its surface to sunlight over the period of its revolution, but it’s not actually rotating in one place, is it? Note: I love astronomy, lifelong fan, A student… yet this has always been one of those little things that I just never seem to grasp. ---
**Author:** ![Frazzled](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/frazzled/32/3368_2.png) [@Frazzled](https://boards.straightdope.com/u/Frazzled)\ **Post date:** [December 22, 2010, 7:42pm UTC](https://boards.straightdope.com/t/does-the-moon-actually-rotate/565102/2 "2010-12-22T19:42:05Z")
In this article about the same face of the moon facing Earth: [http://www.straightdope.com/columns/read/429/why-does-the-same-side-of-the-moon-always-face-the-earth](http://www.straightdope.com/columns/read/429/why-does-the-same-side-of-the-moon-always-face-the-earth) Cecil states that the moon is moving away from the Earth at a rate of 4 inches per month. At this rate, the moon would only be about 330 million years old! The actual rate the moon is pulling away from the Earth is closer to 4 _centimeters per year_. Still not very fast, but much slower than stated in the article. ---
**Author:** ![Pascal666](https://avatars.discourse-cdn.com/v4/letter/p/eada6e/32.png) [@Pascal666](https://boards.straightdope.com/u/Pascal666)\ **Post date:** [December 22, 2010, 7:44pm UTC](https://boards.straightdope.com/t/does-the-moon-actually-rotate/565102/3 "2010-12-22T19:44:06Z")
[Cecil](http://www.straightdope.com/columns/read/429/why-does-the-same-side-of-the-moon-always-face-the-earth) states “the moon continues to recede from us … at the rate of just four inches per month” (48 inches per year). [NASA](http://eclipse.gsfc.nasa.gov/SEhelp/ApolloLaser.html) claims “the Moon is receding from Earth at a rate of about 3.8 centimeters per year” (1.5 inches per year). Cecil needs to set NASA straight. ---
**Author:** ![rootbeer277](https://avatars.discourse-cdn.com/v4/letter/r/57b2e6/32.png) [@rootbeer277](https://boards.straightdope.com/u/rootbeer277)\ **Post date:** [December 22, 2010, 7:46pm UTC](https://boards.straightdope.com/t/does-the-moon-actually-rotate/565102/4 "2010-12-22T19:46:20Z")
Yes, the moon rotates both with respect to the Earth and with respect to the Sun. A lunar day (the rotation with respect to the sun) lasts about 28 Earth days. There’s an image on this page at [HowStuffWorks.com](http://HowStuffWorks.com) that might help you out. > **[How the Moon Works](https://science.howstuffworks.com/moon4.htm)** > > Moon phases change throughout the month and are regular and highly predictable. Learn about moon phases and tides. If you keep in mind that the same side of the moon is facing the Earth at all times, it should be clear that the moon must be rotating with respect to the Sun. ---
**Author:** ![rootbeer277](https://avatars.discourse-cdn.com/v4/letter/r/57b2e6/32.png) [@rootbeer277](https://boards.straightdope.com/u/rootbeer277)\ **Post date:** [December 22, 2010, 7:52pm UTC](https://boards.straightdope.com/t/does-the-moon-actually-rotate/565102/5 "2010-12-22T19:52:07Z")
However, since I’m replying to this post, I think I should point out that there might be a mistake in the article. “the moon continues to recede from us. Admittedly this occurs at the rate of just four inches per month” The actual rate at which the moon recedes from the Earth is actually 3.8 cm per year, or about 1/8 of an inch per month. > **[NASA - Accuracy of Eclipse Predictions](https://eclipse.gsfc.nasa.gov/SEhelp/ApolloLaser.html)** > > This is NASA's official moon phases page. ---
**Author:** ![Frylock](https://avatars.discourse-cdn.com/v4/letter/f/ce7236/32.png) [@Frylock](https://boards.straightdope.com/u/Frylock)\ **Post date:** [December 22, 2010, 8:24pm UTC](https://boards.straightdope.com/t/does-the-moon-actually-rotate/565102/6 "2010-12-22T20:24:46Z")
I would have thought that whether a thing rotates or not isn’t relative to any external objects–it’s just the question of whether its parts are accelerating in relation to each other in a certain way, isn’t it? ---
**Author:** ![Rico](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rico/32/3582_2.png) [@Rico](https://boards.straightdope.com/u/Rico)\ **Post date:** [December 22, 2010, 8:29pm UTC](https://boards.straightdope.com/t/does-the-moon-actually-rotate/565102/7 "2010-12-22T20:29:38Z")
\ Merged three threads on one topic into one thread. \ ---
**Author:** ![tnetennba](https://avatars.discourse-cdn.com/v4/letter/t/7993a0/32.png) [@tnetennba](https://boards.straightdope.com/u/tnetennba)\ **Post date:** [December 22, 2010, 10:09pm UTC](https://boards.straightdope.com/t/does-the-moon-actually-rotate/565102/8 "2010-12-22T22:09:28Z")
There is no dark side of the moon, really. As a matter of fact it’s all dark. ---
**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\ **Post date:** [December 22, 2010, 10:52pm UTC](https://boards.straightdope.com/t/does-the-moon-actually-rotate/565102/9 "2010-12-22T22:52:31Z")
> [@cricetus](#): > > There is no dark side of the moon, really. As a matter of fact it’s all dark. I always thought the dark side of the moon was[ol][_] the side away from the sun[_]a Pink Floyd album[/ol] ---
**Author:** ![BigT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bigt/32/12044_2.png) [@BigT](https://boards.straightdope.com/u/BigT)\ **Post date:** [December 23, 2010, 2:47am UTC](https://boards.straightdope.com/t/does-the-moon-actually-rotate/565102/10 "2010-12-23T02:47:31Z")
> [@Rico](#): > > \ > > Merged three threads on one topic into one thread. > > \ It actually seems there are two different subjects in this one thread. 1. Does the moon really rotate? 2. Cecil made a mistake in the article. The answer to #1 is that, yes, the Moon rotates, even from the reference point of the Sun. The only reference point from which you might be able to say it doesn’t rotate is from the Earth. But that’s a rotational reference frame, as the moon is revolving around the Earth. While there is no absolute frame of reference, a rotational frame is usually not used. It would be like saying that the tires on your car don’t rotate because they don’t move relative to the wheel. The response to #2 is that, yes, Cecil was off by a factor of 30. But, remember, all mistakes are Ed’s fault. 😉 ---
**Author:** ![Ed\_Zotti](https://avatars.discourse-cdn.com/v4/letter/e/fbc32d/32.png) [@Ed\_Zotti](https://boards.straightdope.com/u/Ed_Zotti)\ **Post date:** [December 23, 2010, 5:49am UTC](https://boards.straightdope.com/t/does-the-moon-actually-rotate/565102/11 "2010-12-23T05:49:32Z")
> [@Frazzled](#): > > In this article about the same face of the moon facing Earth: > [http://www.straightdope.com/columns/read/429/why-does-the-same-side-of-the-moon-always-face-the-earth](http://www.straightdope.com/columns/read/429/why-does-the-same-side-of-the-moon-always-face-the-earth) > > Cecil states that the moon is moving away from the Earth at a rate of 4 inches per month. At this rate, the moon would only be about 330 million years old! The actual rate the moon is pulling away from the Earth is closer to 4 _centimeters per year_. Still not very fast, but much slower than stated in the article. At some point in the editing process - undoubtedly a point in which I was involved - 4 centimeters per year morphed into 4 inches per month. It has now morphed back. My apologies to the Teeming Millions and to the Master, who assures me the welts will soon go down. ---
**Author:** ![samclem](https://avatars.discourse-cdn.com/v4/letter/s/a9a28c/32.png) [@samclem](https://boards.straightdope.com/u/samclem)\ **Post date:** [December 23, 2010, 6:33am UTC](https://boards.straightdope.com/t/does-the-moon-actually-rotate/565102/12 "2010-12-23T06:33:09Z")
> [@Ed\_Zotti](#): > > My apologies to the Teeming Millions and to the Master, who assures me the welts will soon go down. Cecil’s getting a bit soft in old age. Showing Pity isn’t like him. 😛 ---
**Author:** ![Sparky812](https://avatars.discourse-cdn.com/v4/letter/s/eb9ed0/32.png) [@Sparky812](https://boards.straightdope.com/u/Sparky812)\ **Post date:** [December 23, 2010, 1:04pm UTC](https://boards.straightdope.com/t/does-the-moon-actually-rotate/565102/13 "2010-12-23T13:04:10Z")
This is a cool time lapse of exactly how the moon appears to move and wobble through its cycle as it orbits the Earth. [![](http://dumbscientist.com/blog/wp-content/uploads/2008/12/Lunar_libration_with_phase_Oct_2007_big.gif) ](http://dumbscientist.com/blog/wp-content/uploads/2008/12/Lunar_libration_with_phase_Oct_2007_big.gif) ---
**Author:** ![Sparky812](https://avatars.discourse-cdn.com/v4/letter/s/eb9ed0/32.png) [@Sparky812](https://boards.straightdope.com/u/Sparky812)\ **Post date:** [December 23, 2010, 1:08pm UTC](https://boards.straightdope.com/t/does-the-moon-actually-rotate/565102/14 "2010-12-23T13:08:37Z")
> [@Musicat](#): > > I always thought the dark side of the moon was[ol] > [li]the side away from the sun[/li][li]a Pink Floyd album[/li][/ol] Hold on… I’ll The Wizard of OZ cued up for this one. 🙂 According to [Wikipedia](http://en.wikipedia.org/wiki/Dark_side_of_the_Moon): > [@](#): > > The **dark side of the Moon** may mean either: > [ul] > [li]the lunar hemisphere that is not currently lit by the sun (which is “dark”)[/li][li]the [far side of the Moon](http://en.wikipedia.org/wiki/Far_side_of_the_Moon), the side that is permanently turned away from the Earth.[/li][/ul] ---
**Author:** ![pravnik](https://avatars.discourse-cdn.com/v4/letter/p/8edcca/32.png) [@pravnik](https://boards.straightdope.com/u/pravnik)\ **Post date:** [December 23, 2010, 3:07pm UTC](https://boards.straightdope.com/t/does-the-moon-actually-rotate/565102/15 "2010-12-23T15:07:35Z")
> [@davekhps](#): > > [In response to this SD classic](http://www.straightdope.com/columns/read/429/why-does-the-same-side-of-the-moon-always-face-the-earth). > > Given that the Moon is locked with the Earth, is it true to say that the Moon rotates? I’m assuming the point of reference is the Sun. The Earth rotates when compared to the Sun, but does the Moon? It revolves around the Earth like a figure skater, exposing its surface to sunlight over the period of its revolution, but it’s not actually rotating in one place, is it? > > Note: I love astronomy, lifelong fan, A student… yet this has always been one of those little things that I just never seem to grasp. [This video](http://www.think-bank.com/iwb/flash/moon%20orbit.html) does a good illustration. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [December 23, 2010, 3:44pm UTC](https://boards.straightdope.com/t/does-the-moon-actually-rotate/565102/16 "2010-12-23T15:44:42Z")
> [@davekhps](#): > > It revolves around the Earth like a figure skater, exposing its surface to sunlight over the period of its revolution, but it’s not actually rotating in one place, is it? Neither is anything else, because that’s a restrictive definition of ‘rotate’ ---
**Author:** ![Irishman](https://avatars.discourse-cdn.com/v4/letter/i/b487fb/32.png) [@Irishman](https://boards.straightdope.com/u/Irishman)\ **Post date:** [December 23, 2010, 6:11pm UTC](https://boards.straightdope.com/t/does-the-moon-actually-rotate/565102/17 "2010-12-23T18:11:42Z")
> [@davekhps](#): > > Given that the Moon is locked with the Earth, is it true to say that the Moon rotates? I’m assuming the point of reference is the Sun. The Earth rotates when compared to the Sun, but does the Moon? It revolves around the Earth like a figure skater, exposing its surface to sunlight over the period of its revolution, but it’s not actually rotating in one place, is it? There are two possible points of confusion. 1. The moon goes around the Earth. As it does so, it maintains the same face toward Earth. Because on one day the side toward Earth is also toward the Sun, and 14 days later that side toward Earth faces away from the Sun, you can tell that the Moon is rotating. 2. Rotation does not require the object to sit still. It can be rotating and moving in a linear direction. Like a top - it spins fast enough to stand up, so clearly it is rotating, but it can also get slightly off balance and wander around. That movement does not negate that the top is rotating about its own axis, just means that the axis of rotation is moving. Same way the Earth rotates once a day, but is also orbiting the Sun, so it is constantly in motion. The Moon also is rotating about its own axis, and the axis of rotation is orbiting the Earth and the Sun. **pravnik** ’s link is an excellent demonstration. ---
**Author:** ![Blakeyrat](https://avatars.discourse-cdn.com/v4/letter/b/ecd19e/32.png) [@Blakeyrat](https://boards.straightdope.com/u/Blakeyrat)\ **Post date:** [December 28, 2010, 10:33pm UTC](https://boards.straightdope.com/t/does-the-moon-actually-rotate/565102/18 "2010-12-28T22:33:23Z")
> [@cricetus](#): > > There is no dark side of the moon, really. As a matter of fact it’s all dark. “When you you think NASA will land on the sun?” “They can’t land on the sun, it’s too hot-- the spaceship would melt!” “Well, they just have to do it at night.”