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Author Topic: Does the moon alter its position relative to the Earth?  (Read 2875 times)

John Harmon

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John Harmon  asked the Naked Scientists:

Folks, my question:

Observers from earth watching the sun see it go through the equator to the tropic of cancer and then back through the equator to the tropic of Capricorn. All of this happens once a year.

Does the moon do the same sort of thing? How far North and South does it travel and what is its period? If not exactly once per year, why not?

John O. Harmon
Clarksville,

What do you think?


 

lyner

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Does the moon alter its position relative to the Earth?
« Reply #1 on: 28/07/2008 10:53:18 »
The Moon's orbit around the Earth is tilted by about 5o relative the the Ecliptic (the plane passing through the mean orbit of the Earth around the Sun). The Equator is about 23% away from the Ecliptic . Because of this, the Moon appears in the sky, at different 'heights' at different times of the Month and the year. There is not a 'whole number' relationship between day length and month length, so its apparent path across the sky is constantly changing. It is not helped by the fact that the Moon's orbit is elliptical - so its apparent size keeps varying  and its orbit speeds up and slows down, too.
Its Phases (apparent shape) are caused by the relative position of the Sun in the sky, so, to a casual observer, there seems to be no pattern. However, the position and appearance can be predicted to a high degree of accuracy for years and years in advance.
It is very satisfying, once you have sussed out the approximate geometry of the arrangement, to look up at 'nearby' objects, such as the Moon and Planets and to explain their positions in the sky and their appearances. It's not rocket science and it all makes sense.

I saw the Moon from Brazil, during a brief visit. Very disturbing, for one who was used to the UK view.
« Last Edit: 28/07/2008 10:54:52 by sophiecentaur »
 

Offline chris

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Does the moon alter its position relative to the Earth?
« Reply #2 on: 29/07/2008 00:28:20 »
I saw the Moon from Brazil, during a brief visit. Very disturbing, for one who was used to the UK view.

Yes, I recall seeing the moon in Zimbabwe  (southern hemisphere) and could only describe it as "upside down" - it looked very odd to me!
 

Online syhprum

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Does the moon alter its position relative to the Earth?
« Reply #3 on: 29/07/2008 10:30:47 »
Chris

Of course one is upside down relative to the elliptic that is why celestial objects look strange and appear to go around the 'wrong' way
 

lyner

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Does the moon alter its position relative to the Earth?
« Reply #4 on: 29/07/2008 10:48:55 »
And, being almost overhead doesn't help it to look 'natural', either.
 

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Does the moon alter its position relative to the Earth?
« Reply #4 on: 29/07/2008 10:48:55 »

 

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