Talk:Moon/Archive 1

message: :'Energy from sunlight splits much of this water into its constituent elements hydrogen and oxygen, both of which usually fly off into space immediately.'
Why would this be ? The moon has Gravity and the molecules have some density that is higher than that of empty space! It should remain in some hight of atmosphere ?! Togo 05:01, 20 May 2004 (UTC)
replies: text: The Moon has gravity, but not nearly as much gravity as a planet like Earth does; this means it has a lower escape velocity. As a result, the thermal motion of lightweight molecules such as oxygen and hydrogen easily reaches velocities higher than the Moon's escape velocity and the molecules never fall back to the surface. Bryan 05:11, 20 May 2004 (UTC)
thread_title: Water Escape

message: Disappointed to find no Wikipedia article on the Gerstenkorn event. Unfortunately, the only info I have is from 1982 and, I suspect, quite out of line with later thinking. Would be nice to see something, or have I missed it? Cutler 12:21, 24 Feb 2004 (UTC)
thread_title: Gerstenkorn event

message: It's a nice animation, but even with the touchup work I did on it a moment ago the image is still over half a megabyte in size. I think it should be moved out of the main article, both for the benefit of those without broadband and for those who wish to print out the article (the animation would be useless to them). Any ideas on where I should send it? I'm thinking Lunar phase.
Tom Ruen- 5/2/04 - I uploaded the phase animation. Thanks for the impressive touchup! I agree it isn't friendly to have big images on general info pages. Free free to move it if you like. Maybe Lunar phase or maybe better Libration ?
:Libration looks good, Lunar phase already has a good image on it. I must say, this animation illustrates libration better than anything I've seen before - I virtually get seasick watching the Moon rocking back and forth. :) Bryan 09:03, 2 May 2004 (UTC)
thread_title: Animated Moon phase gif

message: Just curious, but was there any reason why the caption under the moon image said "Hold mouse over image for description," and the caption only appeared if I do that? I thought that was silly, so I put the proper caption under the image. - Brian Kendig 19:15, 31 Aug 2004 (UTC)
thread_title:  Caption 

message: Within the article, there are a couple of problems with the orbital distances in the tables.
Orbital characteristics
*Semi-major axis 384,400 km (0.0026 AU)
*Orbital circumference 2,413,402 km (0.016 AU)
*Eccentricity 0.0554
*Perigee 363,104 km (0.0024 AU)
*Apogee 405,696 km (0.0027 AU)
Other properties of the Moon's orbit
*Mean distance from Earth ~384 403 km  
*Distance at perigee ~364 397 km  
*Distance at apogee ~406 731 km 
The semi-major axis and mean distance are much the same here, but perigee and apogee differ quite a bit between these two tables. There is no explanation given for these discrepancies.
The figures given for distances in astronomical units (AU) are given to a precision of only two significant figures, even though the distance in kilometres is given to a precision of six figures and the AU is defined elsewhere in Wikipedia with similar precision. If the distance in AU's is to be given, it would be better if these distances were revised to six significant figures to match the precision of the distances in kilometres.
--B.d.mills 12:38, 27 Nov 2004 (UTC)
thread_title: Inconsistent statistics for lunar orbit

message: Under Origin, it is said that "Tidal forces deformed the once molten Moon into an ellipsoid, with the major axis pointed towards Earth".  Can anyone provide a reference that gives the Moon's dimensions (as a triaxial ellipsoid)?  I had a devil of a time just finding one (one!) reference for the biaxial dimensions and hence oblateness...
Urhixidur 23:54, 2005 Jan 18 (UTC)
Our table currently lists:
:Equatorial diameter 3476.2 km 
:Polar diameter 3472.0 km
:Oblateness 0.0012
The current JPL listing is (following the 1977 reference to ):
:Mean diameter 3475.06 ± 0.06 km (formal standard error)
Also note « an offset of the centre of figure of 1.98±0.06 km toward (19±2)°S, (194±1)°E ».
Apparently, Don Dixon's Universe (Houghton Mifflin, 1981), gives:
:Equatorial 3477.8
:Average 3476.7
:Polar 3475.6
:Hence Oblateness 0.00063±0.00003
That's the best we've got so far.
Urhixidur 04:19, 2005 May 3 (UTC)
Addendum:  gives Moon oblateness as 0.002 and diametre of 3475.06 km (notice the match with the 1977 measurement quoted above).
131.136.242.1 19:14, 6 May 2005 (UTC)
thread_title:  Moon axes?