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Science Forum

  1. 09 Mar '09 20:40
    I've been wondering this for a while.
    When there is a certain phase of the moon when I look out of the window, does someone who lives at the other side of the world looks at the moon when it's night for him sees the same kind of moon?
  2. 09 Mar '09 21:12
    Originally posted by michiely
    I've been wondering this for a while.
    When there is a certain phase of the moon when I look out of the window, does someone who lives at the other side of the world looks at the moon when it's night for him sees the same kind of moon?
    Yes, they see the same moon with the same phase.
    But perhaps of distance from the equator it is more or less tilted.
  3. Standard member sonhouse
    Fast and Curious
    10 Mar '09 02:03 / 1 edit
    Originally posted by FabianFnas
    Yes, they see the same moon with the same phase.
    But perhaps of distance from the equator it is more or less tilted.
    And that is because the change in perspective from one side of the earth to the other, about 13,000 Km is small considering the distance to the moon, which is about 375,000 Km. If you take that as the radius of a large circle, the diameter of which is two times that, about 750,000 Km and multiply that times PI, you get a circle about 2,300,000 Km and divide by 12,800 (Earth's diameter) you get 184,(1/184th of a circle) which is about 2 degrees of separation, not very far apart, so there won't even be much difference in the visual aspect of whatever phase you are looking at.
  4. 10 Mar '09 08:06 / 1 edit
    Originally posted by sonhouse
    And that is because the change in perspective from one side of the earth to the other, about 13,000 Km is small considering the distance to the moon, which is about 375,000 Km. If you take that as the radius of a large circle, the diameter of which is two times that, about 750,000 Km and multiply that times PI, you get a circle about 2,300,000 Km and divide there won't even be much difference in the visual aspect of whatever phase you are looking at.
    You're right. What I thought about was that far apart from eachother in north/south direction, one is seeing the moon 'correct', the other one 'upside down'.

    I live at 57 degrees north, so I see Orion constellation 'correctly'. I once was in Australia and I didn't recognize Orion at first. It was upside down! At the equator at dusk and dawn, you see Orion as a butterfly - very strange I'd say.

    But the reason is obvious, of course. Your 'up' is the direction from Earth's centre does not correspond to another person's 'up'. When you look at the constellations and the moon, the distance from the equator (or of the poles) is of significance.
  5. 10 Mar '09 08:43
    Originally posted by FabianFnas
    You're right. What I thought about was that far apart from eachother in north/south direction, one is seeing the moon 'correct', the other one 'upside down'.
    That might apply to constellations that never get far above the horizon, and it might apply to constellations you typically only see in the evening.
    However most of us see the moon at any time of day including moon rise or moon set and it will be a different way up depending on whether it is rising or setting. So I might see it rising one way up and someone in China or further east is simultaneously seeing it setting the other way up. Someone in the northern hemisphere should observe almost the same as I do at rising and setting but may see the opposite as 'moon noon'.