   The dark side of the moon
  A long time ago, my teacher geology told us that we can''t see the dark side of the moon, because the moon rotates around it''s own axis with exactly the same speed as that it rotates around the earth, so that it''s dark side is always rotated away from it.This makes sense to me, except for one thing: how is it possible that the moon rotates around the earth with EXACTLY the same speed as that it rotates around it''s own axis?  Those two rotation speeds aren''t related to each other in any way (for example the earth rotates around it''s own axis in 1 day and around the sun in around 365 days).Is it really exact?  Or is there a little difference so that in thousands of years a slightly different side is visible, so that it would be just a coincidence? 
quote:Original post by Boops  This makes sense to me, except for one thing: how is it possible that the moon rotates around the earth with EXACTLY the same speed as that it rotates around it''s own axis?  Those two rotation speeds aren''t related to each other in any way (for example the earth rotates around it''s own axis in 1 day and around the sun in around 365 days).This is due to tidal friction. On the earth, the oceans are pulled about by the moon''s gravitional field and so this causes the tides, and gradually slows the earth''s rotation. Since the earth is much more massive than the moon, it exerts a greater effect on the moon (and in fact causes "moonquakes") and this is what caused the moon to gradually slow so that only one side can be seen from the earth. ;  I like to imagine swinging a yoyo around my head.  ;  What's mean "dark side"? Back side is lit when we can't see the moon(i.e.,when,looking from earth, moon is close to the sun)Also,your teacher are only parially right. We can see more than 50% of moon surface,because moon still oscilating. Moon stay rotated to earth by one side exactly for same reason why ISS axis mostly  points to center of earth:   m1  |  flyes --- >  m2  O earth  (m1 and m2 are masses)here m2 are under bigger gravitational force and m1 have bigger  inertial "force" and lower gravitational force than m2. So , that position are stable , because if line m1m2 aren't vertical,there's resulting force that turns it to be vertical./    || F1  <-m1   /  m2->  || F2  \/ then    /    || F1    m1->\    <-m2    || F2    \/  Same for moon,moon is not a sphere but something like egg.google:http://www.moonphasecalendar.com/same_side.htm   [edited by - Dmytry on February 13, 2004 9:24:17 AM];  There is no dark side of the moon, really...matter of fact, it''s all dark. ;  Run krikkit, you missed the starting gun. ;  *this is all me thinks*Relative to the earth the moon does not spin, you know this, but should you remove the earth and make the moon stant in one place, it would appear to turn. Right now, its kinda like a person(the earth) holding a string(gravity of earth) in one hand with a rock(the moon) tied to the end. When you spin it, the same side of the rock always faces you. You may not think the rock is rotating on its axis, but if you were to place a camera directly over the rock as it orbits you always facing north, the rock would appear to rotate.This is what i understood, or im lying.... ;quote:Original post by krikkit   There is no dark side of the moon, really...matter of fact, it's all dark.   hehe, if anyone doesnt know where that quote is from you should be shot twice.BTW: doesnt the pink floyd song 'echos' on the album 'meddle' go with some movie as well?   [edited by - Mulligan on February 13, 2004 11:18:09 AM];quote:Original post by krikkit  There is no dark side of the moon, really...matter of fact, it''s all dark.   Bugger, beat me to it  I was gonna post that! ;quote:Original post by capn_midnight  I like to imagine swinging a yoyo around my head.    i like to imagine i''m swimming in cream... 