# Dark side of the moon facing earth? **URL:** \ **Category:** Factual Questions\ **Created:** [August 6, 2003, 7:03am UTC](https://boards.straightdope.com/t/dark-side-of-the-moon-facing-earth/193288 "2003-08-06T07:03:34Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![I\_Brian](https://avatars.discourse-cdn.com/v4/letter/i/c89c15/32.png) [@I\_Brian](https://boards.straightdope.com/u/I_Brian)\ **Post date:** [August 6, 2003, 7:03am UTC](https://boards.straightdope.com/t/dark-side-of-the-moon-facing-earth/193288/1 "2003-08-06T07:03:34Z")
I’m under the impression that the same face of the moon always faces the earth. Is this actually correct? Or does the dark side of the moon actually face earth during the New Moon phase? ---
**Author:** ![Joe\_Random](https://avatars.discourse-cdn.com/v4/letter/j/e8c25b/32.png) [@Joe\_Random](https://boards.straightdope.com/u/Joe_Random)\ **Post date:** [August 6, 2003, 7:07am UTC](https://boards.straightdope.com/t/dark-side-of-the-moon-facing-earth/193288/2 "2003-08-06T07:07:30Z")
> [@](#): > > \*Originally posted by I, Brian \* > \*\*I’m under the impression that the same face of the moon always faces the earth. > > Is this actually correct?\*\* Yes. The moon rotates on its axis once for every revolution around the earth, resulting in the same side always facing the earth. > [@](#): > > \*\*Or does the dark side of the moon actually face earth during the New Moon phase? \*\* Yes again. Don’t confuse the “dark side of the moon” with the “far side of the moon”. The dark side of the moon is the side that’s, well, _dark_ (i.e. not illuminated by the sun). The far side of the moon is the side that always faces away from the earth. ---
**Author:** ![Thaumaturge](https://avatars.discourse-cdn.com/v4/letter/t/858c86/32.png) [@Thaumaturge](https://boards.straightdope.com/u/Thaumaturge)\ **Post date:** [August 6, 2003, 7:10am UTC](https://boards.straightdope.com/t/dark-side-of-the-moon-facing-earth/193288/3 "2003-08-06T07:10:20Z")
There is no “dark side of the moon”. However, one side does always face the earth, and that side is indeed dark during a new moon. You can demonstrate for yourself with a flashlight and two balls, one for the earth and moon. ---
**Author:** ![MonkeyMensch](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@MonkeyMensch](https://boards.straightdope.com/u/MonkeyMensch)\ **Post date:** [August 6, 2003, 7:44am UTC](https://boards.straightdope.com/t/dark-side-of-the-moon-facing-earth/193288/4 "2003-08-06T07:44:21Z")
> [@](#): > > \*Originally posted by Thaumaturge \* > \*\*There is no “dark side of the moon”. However, one side does always face the earth, and that side is indeed dark during a new moon. You can demonstrate for yourself with a flashlight and two balls, one for the earth and moon. \*\* OK. I’ve got a flashlight and my two balls. How exactly is this supposed to work? 😉 ---
**Author:** ![sailor](https://avatars.discourse-cdn.com/v4/letter/s/a587f6/32.png) [@sailor](https://boards.straightdope.com/u/sailor)\ **Post date:** [August 6, 2003, 8:14am UTC](https://boards.straightdope.com/t/dark-side-of-the-moon-facing-earth/193288/5 "2003-08-06T08:14:18Z")
There is no such thing as “the dark side of the moon”. An observer located anywhere on the moon would see the sun rise and set. The lunar “day” would be the length of our month. ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [August 6, 2003, 9:45am UTC](https://boards.straightdope.com/t/dark-side-of-the-moon-facing-earth/193288/6 "2003-08-06T09:45:24Z")
> [@](#): > > There is no such thing as “the dark side of the moon”. Pah! Try telling that to Pink Floyd. Anyway, the moon is indeed tidally locked to the Earth, although not totally so - there are small “wobbles” in the angle at which it faces the Earth, a phenomenon known as libration. In fact, at various times we can see 59% of the moon from the Earth (although obviously not all at once!) ([Cite](http://www.astro.ufl.edu/~cohen/ast1002/article_libration.html)) ---
**Author:** ![Zeldar](https://avatars.discourse-cdn.com/v4/letter/z/b77776/32.png) [@Zeldar](https://boards.straightdope.com/u/Zeldar)\ **Post date:** [August 6, 2003, 9:52am UTC](https://boards.straightdope.com/t/dark-side-of-the-moon-facing-earth/193288/7 "2003-08-06T09:52:45Z")
Let the flashlight represent the sun. Use the two balls as Earth and Moon. Set the two balls on a table (or the floor) some distance away from the flashlight, but fairly close to each other. Just for example, put the two balls about 6" apart but about 3’ from the flashlight. Now, leaving one ball still, (the Earth) move the other ball in a circle around the staionary one in such a way that the same “side” of the moving ball always faces the stationary one. Observe the way the light from the flashlight falls on both balls. When both balls are in line with each other and the flashlight, they are in position for the eclipses. When the moving ball is between the stationary one and the flashlight, that’s “new moon” or a solar eclipse. On the other side of the stationary ball is “full moon” or lunar eclipse. The reason we don’t have eclipses every month is that the orbit of the moon about the earth is tilted to the orbit of the Earth-Moon system about the sun. The tilt is such that twice a year the two orbits cross and it’s then possible to have up to five eclipses during the same 12-month period. But the main thing to watch for is how the lighted portions of the two balls relate to each other, as seen from the viewpoint of the stationary ball. ---
**Author:** ![Colophon](https://avatars.discourse-cdn.com/v4/letter/c/f05b48/32.png) [@Colophon](https://boards.straightdope.com/u/Colophon)\ **Post date:** [August 6, 2003, 9:56am UTC](https://boards.straightdope.com/t/dark-side-of-the-moon-facing-earth/193288/8 "2003-08-06T09:56:39Z")
Oh, and **MonkeyMensch** - this is how the flashlight/balls thing works. Actually, it’s probably easiest just to use a lightbulb hanging from the ceiling. Take one ball in each hand (insert your own joke here) and hold them side on to the bulb (“sun”) at arm’s width. Ideally you’ll have a small one to represent the moon and a big one for the Earth. You’ll see that the “moon” is half illuminated. Now, keeping the balls at the same orientation relative to each other, turn sideways so the moon is in line between the sun and the Earth. The side facing the Earth is dark, right? This is a new moon. Now turn round through 180 degrees so that the moon is on the opposite side of the Earth from the sun, but still keeping the same side of the moon facing the Earth. Now, provided that the moon is not in the shadow of the Earth (it helps if the bulb is above the plane of the two balls), you will see that the side of the moon facing the Earth is fully lit. This is a full moon. If the moon happens to fall in the shadow of the Earth as it passes throught the “full moon” phase, you get a lunar eclipse. ---
**Author:** ![GuanoLad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/guanolad/32/42_2.png) [@GuanoLad](https://boards.straightdope.com/u/GuanoLad)\ **Post date:** [August 6, 2003, 10:37am UTC](https://boards.straightdope.com/t/dark-side-of-the-moon-facing-earth/193288/9 "2003-08-06T10:37:29Z")
Yes, but what about the dark side of the sun? ---
**Author:** ![Zeldar](https://avatars.discourse-cdn.com/v4/letter/z/b77776/32.png) [@Zeldar](https://boards.straightdope.com/u/Zeldar)\ **Post date:** [August 6, 2003, 10:43am UTC](https://boards.straightdope.com/t/dark-side-of-the-moon-facing-earth/193288/10 "2003-08-06T10:43:02Z")
You don’t really want to see the dark side of the sun. That’s when it’s all over. It’s like the dark side of a bonfire. ---
**Author:** ![BwanaBob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bwanabob/32/2985_2.png) [@BwanaBob](https://boards.straightdope.com/u/BwanaBob)\ **Post date:** [August 6, 2003, 11:53am UTC](https://boards.straightdope.com/t/dark-side-of-the-moon-facing-earth/193288/11 "2003-08-06T11:53:33Z")
> [@](#): > > \*Originally posted by Zeldar \* > \*\* > The tilt is such that twice a year the two orbits cross and it’s then possible to have up to five eclipses during the same 12-month period. > \*\* Actually, there can be up to seven eclipses in a year. [Cite](http://home.t-online.de/home/Dr.Strickling/saros.htm) ---
**Author:** ![Zeldar](https://avatars.discourse-cdn.com/v4/letter/z/b77776/32.png) [@Zeldar](https://boards.straightdope.com/u/Zeldar)\ **Post date:** [August 6, 2003, 12:00pm UTC](https://boards.straightdope.com/t/dark-side-of-the-moon-facing-earth/193288/12 "2003-08-06T12:00:40Z")
> [@](#): > > \*Originally posted by BwanaBob \* > \*\*Actually, there can be up to seven eclipses in a year. [Cite](http://home.t-online.de/home/Dr.Strickling/saros.htm) \*\* Thanks for that correction, **BwanaBob**. I should have checked my astronomy book first. Nice link, by the way. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [August 6, 2003, 12:30pm UTC](https://boards.straightdope.com/t/dark-side-of-the-moon-facing-earth/193288/13 "2003-08-06T12:30:24Z")
**Cecil** : [Why does the same side of the moon always face the earth?](http://www.straightdope.com/classics/a2_112.html) **Chronos** : [Why does the same side of the moon always face the earth?](http://www.straightdope.com/mailbag/mlunarrotate.html) Comments on **Chronos’** staff report: [lunar rotation](http://boards.straightdope.com/sdmb/showthread.php?s=&threadid=159592&highlight=libration) ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [August 6, 2003, 12:53pm UTC](https://boards.straightdope.com/t/dark-side-of-the-moon-facing-earth/193288/14 "2003-08-06T12:53:03Z")
Sorry to rain on the parade, but when you want to know about the dark side of the moon, you have to consult the real experts. And they have [incontravertible proof](http://www.lyricsfreak.com/p/pink-floyd/108800.html): > [@](#): > > The evidence before the court is incontravertible. > There’s no need for the jury to retire. There’s no [no dark side](http://www.theage.com.au/articles/2003/06/23/1056220536301.html): > [@](#): > > There is no dark side of the moon, really… Matter of fact, it’s all dark. 😉 ---
**Author:** ![godzillatemple](https://avatars.discourse-cdn.com/v4/letter/g/49beb7/32.png) [@godzillatemple](https://boards.straightdope.com/u/godzillatemple)\ **Post date:** [August 6, 2003, 12:55pm UTC](https://boards.straightdope.com/t/dark-side-of-the-moon-facing-earth/193288/15 "2003-08-06T12:55:59Z")
All right, but is it really safe to send a space ship to visit the sun as long as one does so at night? 😉 Barry ---
**Author:** ![I\_Brian](https://avatars.discourse-cdn.com/v4/letter/i/c89c15/32.png) [@I\_Brian](https://boards.straightdope.com/u/I_Brian)\ **Post date:** [August 6, 2003, 6:05pm UTC](https://boards.straightdope.com/t/dark-side-of-the-moon-facing-earth/193288/16 "2003-08-06T18:05:48Z")
Thanks for the first replies. I’ll leave you to play with your balls in the dark now. 🙂 ---
**Author:** ![Faldage](https://avatars.discourse-cdn.com/v4/letter/f/f4b2a3/32.png) [@Faldage](https://boards.straightdope.com/u/Faldage)\ **Post date:** [August 6, 2003, 6:29pm UTC](https://boards.straightdope.com/t/dark-side-of-the-moon-facing-earth/193288/17 "2003-08-06T18:29:39Z")
The phrase “the dark side of the moon” dates from a time when the word “dark” could mean “unknown” as well as the now more commonly used definition “unlit”. There is now no “dark side of the moon” in this sense, but before the Soviets orbited it there was. ---
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [August 6, 2003, 8:31pm UTC](https://boards.straightdope.com/t/dark-side-of-the-moon-facing-earth/193288/18 "2003-08-06T20:31:20Z")
There is \*\*always \*\*a dark side of the moon, just as there is always a dark side of the earth. To deny this is to imply that it’s lit all over, at the same time. Of course, during a total lunar eclipse, the moon is (relatively) dark on all sides. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [August 10, 2003, 1:51pm UTC](https://boards.straightdope.com/t/dark-side-of-the-moon-facing-earth/193288/19 "2003-08-10T13:51:33Z")
Today’s APOD has an excellent gif animation of [the moon](http://antwrp.gsfc.nasa.gov/apod/ap030810.html) over the course of a month. The changing face is clearly visible as maria on the right edge rotate in and out of view. ---
**Author:** ![wolf\_meister](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolf_meister/32/15202_2.png) [@wolf\_meister](https://boards.straightdope.com/u/wolf_meister)\ **Post date:** [August 10, 2003, 8:14pm UTC](https://boards.straightdope.com/t/dark-side-of-the-moon-facing-earth/193288/20 "2003-08-10T20:14:06Z")
I agree with **panache** that there **is** a dark side of the Moon which is constantly changing. To me it is analagous to saying “the other side of the street” or the “opposite sex”. Nit-picking alert - I always thought the words Moon and Sun should be capitalized in discussions or publications involving astronomy. This avoids confusing “The Moon” and “The Sun” with other moons and suns that might be found in the Universe. Hmmm should Universe be capitalized?