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What time of the year is the moon closest to the Earth??



 
 
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  #1  
Old January 3rd 07, 06:22 PM posted to sci.astro
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Default What time of the year is the moon closest to the Earth??

Now that the distance between the earth and the moon has been measured
with great precision. Could anyone tell me what time of the year is
the moon closest to the Earth??

Thank you. Don Hamilton

  #2  
Old January 3rd 07, 06:43 PM posted to sci.astro
dlzc
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Default What time of the year is the moon closest to the Earth??

Dear dlham:

wrote:
Now that the distance between the earth and the moon has
been measured with great precision. Could anyone tell me
what time of the year is the moon closest to the Earth??


http://www.fourmilab.ch/earthview/moon_ap_per.html
QUOTE
The combined effects of orbital eccentricity and the Sun's tides result
in a substantial difference in the apparent size and brightness of the
Moon at perigee and apogee. Extreme values for perigee and apogee
distance occur when perigee or apogee passage occurs close to new or
full Moon, and long-term extremes are in the months near to Earth's
perihelion passage (closest approach to the Sun, when the Sun's tidal
effects are strongest) in the first few days of January.
END QUOTE

David A. Smith

  #3  
Old January 4th 07, 03:37 AM posted to sci.astro
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Default What time of the year is the moon closest to the Earth??

dlzc wrote:
Dear dlham:

wrote:
Now that the distance between the earth and the moon has
been measured with great precision. Could anyone tell me
what time of the year is the moon closest to the Earth??


http://www.fourmilab.ch/earthview/moon_ap_per.html
QUOTE
The combined effects of orbital eccentricity and the Sun's tides result
in a substantial difference in the apparent size and brightness of the
Moon at perigee and apogee. Extreme values for perigee and apogee
distance occur when perigee or apogee passage occurs close to new or
full Moon, and long-term extremes are in the months near to Earth's
perihelion passage (closest approach to the Sun, when the Sun's tidal
effects are strongest) in the first few days of January.
END QUOTE


David A. Smith


Thanks Dave

http://www.fourmilab.ch/images/peri_apo/

This article states that "the moon is at perigee relative to the earth
when earth is at apogee relative to the sun and the moon is at apogee
relative to the earth when the earth is at perigee relative to the
sun."

Can anyone tell me if there is a logical explanation why this
"coincidence" occurs?? Why the moon is closest to the earth when the
earth is farthest from the sun and visa versa??

Don Hamilton

  #4  
Old January 4th 07, 03:45 PM posted to sci.astro
dlzc
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Posts: 1,426
Default What time of the year is the moon closest to the Earth??

Dear dlham:

wrote:
....
Thanks Dave


You are welcome. I was surprised I could find the answer that easily.

http://www.fourmilab.ch/images/peri_apo/

This article states that "the moon is at perigee relative
to the earth when earth is at apogee relative to the sun
and the moon is at apogee relative to the earth when
the earth is at perigee relative to the sun."

Can anyone tell me if there is a logical explanation
why this "coincidence" occurs?? Why the moon is
closest to the earth when the earth is farthest from the
sun and visa versa??


Conservation of angular momentum. The *system* of Earth (E) and the
Moon (M) is not isolated from the Sun (S). The SEM system angular
momentum is constant (ignoring all the other bodies in the solar
system). So you can think of M picking up (or holding) some momentum
(however briefly) from the SE system.

Three-body problems are always thorny. Hopefully you will get a better
/ clearer answer from others here.

David A. Smith

 




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