Why Can't We See The Far Side Of The Moon?

[zingo1327]

What I know (in an idiots fashion.)
The moon takes 28 days to orbit the Earth and 28 days to do one Moon rotation.
The moon can always be seen somewhere from Earth. weather permitting.
I see how it works if you treat the earths orbit like a clock face, spinning 9 o'clock,3 o'clock,9 o'clock,3 o'clock (East/West and the moons orbit as spinning 12 o'clock,six o'clock,12 o'clock,six o'clock.North/South, but I've been informed we both spin East to West (9 o'clock,3 o'clock,9 o'clock,3 o'clock)
If we run an imaginery line North/South around the moon and then split the face as we see it as A and B then logic says the splits hidden will be C+D.
My tiny brain then says the moon should have completed quarter of a moon rotation and quarter of an Earth orbit after 7 days,half a moon rotation and Earth orbit after 14 days,3/4 a moon rotation and Earth orbit after 21 days and back to where it started after 28 days.
I can't get my brain round, how after 7 days, we're not seeing sectors D and A, and after 14 days we're not seeing sectors C and D, and after 21 days we're not seeing sectors B and C.
After 28 days we're back to seeing sectors A and B.
I've tried looking at simulation sites but it still bamboozles me.
Can someone explain in simple terms or recommend a good simulation website.Sarcastic comments always welcome :-)

[Mojo-Jo-Jo]

Get something flat and round and mark it it some way at one edge so that you have a point you can see.
Place it on a table and with your finger "orbit it around something without turning it. You will see that the mark sometimes faces you and sometimes doesn't. That would be the moon if it didn't rotate.
Now orbit it again, but this time keep the marker always facing the central object. Notice that you have to turn it to do this. That's the moon with it's relationship to us.

[Mojo-Jo-Jo]

*faces the central object, not you.

[New Judge]

I don’t quite see your difficulty grasping this, zingo. A number of the answers have explained it quite clearly, but let’s see if I can help.

The rotation of the Earth on its axis is completely irrelevant to this conundrum. Get a friend to face you and then to “sidestep” along a circular path around you keeping you at the centre but making sure that they always face you. (This is what the moon does. It always presents the same face to the Earth because it takes 28 days to orbit the Earth and 28 days to rotate once on its axis in the same direction). No matter how much you turn round or in what direction you do so you will never see your friend’s back but will always see him facing you.

Does this help???

[naomi24]

Zingo, this might help.

http://www.bbc.co.uk/learningzone/clips/the-moon-and-its-orbit-around-the-earth/1596.html

[Sipowicz]

Hope this helps, watch all of it!

http://www.youtube.com/watch?v=OZIB_leg75Q

[EDDIE51]

If the Moon did not rotate on its axis the side you see would depend on where on Earth you were, but observers who stay in the same place would always see the same side. For example if you were in UK you would see one side but someone in Australia would always the opposite side.

[Ellipsis]

Sipowicz's video link explains it perfectly.

zingo, I think you're problem is that you're trying to consider the Moon's rotation from the point of view of the an observer on Earth. It's easier if you consider yourself watching the whole thing from a spaceship that's outside the Moon/Earth system - which is effectively what Sipowicz's video link shows.

[Ellipsis]

OMG!!!

your* problem

[naomi24]

With all due respect, I think the link I posted gives a good demonstration - and the simplest explanation.

[starone]

So, if you were on the moon would you get a day and night period or is there a definite division between the light and dark side of the moon? Sorry, not an answer, but another question.

[Ellipsis]

Naomi, I think your link shows phases of the Moon perfectly, but it doesn't discuss the rotation of the moon and the fact that the same side of the Moon is always presented to Earth at all. Sipowicz's video is far better for that.

[Ellipsis]

> if you were on the moon would you get a day and night period

Yes, one Moon day is 28 Earth days, so it would be light for 14 days and dark for 14 days if you stood on one spot for 28 days.

> or is there a definite division between the light and dark side of the moon

The dark side of the Moon is a misnomer, because it means the side that faces away from Earth. Sometimes it's dark and at other times it''s light. That's my understanding anyway. According to Wikipedia that's only one of two possible definitions:

http://en.wikipedia.org/wiki/Dark_side_of_the_Moon

[naomi24]

Ellipsis, it seems to me that the rotation of the moon is precisely the problem Zingo is struggling with and I think the BBC video demonstrates very simply how the same side of the moon is presented to us continually - but it's for him to decide. I hope it helps anyway.

[starone]

Thanks ellipsis. Always wondered.

[zingo1327]

After i hour in the pub with betting slips and pencils I finally had the Eureka moment and understood.Thanks for your help guys

[naomi24]

Ha ha! The beer didn't help by any chance, did it? ;o)

[DangerUXD]

Beer can solve almost any problem, for the few it cannot solve there is Vodka!

[naomi24]

I find red wine very helpful. Good for the brain. :o)

[mibn2cweus]

EDDIE51
If the Moon did not rotate on its axis the side you see would depend on where on Earth you were, but observers who stay in the same place would always see the same side. For example if you were in UK you would see one side but someone in Australia would always the opposite side.
21:36 Thu 17th Jan 2013

Now I need a drink! :o/