Talk:Moon/Archive 2

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Conspiracy Theories

There is a large group who do not believe man landed on the moon. They have several anecdotes and some facts. How should this be included in the article. At least a blurb needs to be added. What do you all think?

Wiki page

• Apollo_moon_landing_hoax_accusations

Links:

• [1]
• [2]

24.225.54.44 05:36, 3 January 2006 (UTC)

It is linked to under "See also," which looks good enough to me. Awolf002 14:42, 3 January 2006 (UTC)

Double-planet hypotheses

There are several good arguments in favor of considering the Earth-Moon system to be a double planet, even if this is not the majority opinion currently, so I put in a paragraph that points to the Double planet article so that people interested in the alternative views can look them up.

Agateller 04:15, 11 January 2006 (UTC)

Roman naming?

Why isn't this article named properly? All planets and significant natural satelites have proper roman names. Why would the earth ( Terra ) or the moon ( Luna ) be any different? Just because a thousand people call out natural satelite "the moon" doesn't mean they are right. Give this article it's proper name, Luna.

I disagree with "Luna" being the proper name. This is the "english" dictionary and should reflect the common usage of words. Also, Luna already exists and is a dab page for good reasons. Awolf002 12:37, 16 Feb 2005 (UTC)

Seconded. It should use the name that is most commonly used. And Moon is hands-down the most common. Also, the proper names of natural satellites aren't fixed regardless of language. Moon is the proper name of our natural satellite in English. The page title should reflect that. --Patteroast 13:31, 16 Feb 2005 (UTC)

Absolutely, all "planets and significant natural satelites" may "have proper roman [sic] names" they also have proper English names. The difference about the Sun, Moon and Earth is that the names are different in the two different langauges. Feel free to give them their "proper roman names" in a Latin encyclopædia but this is an English one. Jimp 20Sep05

the moon is square

To the lay person

This article is great. Except - it's too dense with the science. Obviously those writing and contributing are smart and know their stuff but it fails to enlighten the lay reader to basic questions.
For instance: how long is the moons orbit around the earth? "About a month" is the first answer. Scan the article for a more accurate answer and you find a chart with several different "periods" of several different days, with scientific names that don't mean anything to the lay reader. SchmuckyTheCat 16:02, 25 Feb 2005 (UTC)

Is it better now? Here is the second paragraph somewhat expanded:

Several ways to consider a complete orbit are detailed in the table below, but the two most familiar are: the sidereal month being the time it takes to make a complete orbit with respect to the stars, about 27.3 days; and the synodic month being the time it takes to reach the same phase, about 29.5 days. These differ because in the meantime the Earth and Moon have both orbited some distance around the Sun.

-Wikibob | Talk 16:39, 2005 Mar 13 (UTC)

Danger to civilization

The likelihood of it happening "anytime soon" is not a qualifier for it being in the article. If you don't want it in the article, justify why, state your case, not just revert "rv" (I assume you were not calling it "Vandalism"). This is a legitimate topic of discussion, just as the earth could be struck by a meteorite, so could the moon. Stbalbach 21:52, 11 Mar 2005 (UTC)

It is simply not going to happen. Smaller asteroids a few km in diameter or less can threaten life on Earth because of their side effects to the atmosphere or the oceans, but such small asteroids (not to mention mere meteorites) would not break up the Earth or the Moon, they'd just leave a crater. To break up the Moon, an asteroid would have to be several orders of magnitude larger (at least 100 km across, probably more) and there are simply no such large-enough asteroids in Earth-crossing orbits. Those kind of massive collisions occurred in the early days of the solar system, but not now and not in the future... such huge flying debris was cleared away during collisions in the early days of the solar system. All such very large asteroids currently existing are in safe, stable orbits in the asteroid belt.

To summarize, threats to life exist from small asteroids colliding with the Earth, that's well known. But small asteroids colliding with the Moon will just leave a crater, nothing more. -- Curps 22:06, 11 Mar 2005 (UTC)

---

The article you cite [3] correctly points out that the presence of the Moon is important for stabilizing the Earth's axis, and for various reasons the existence of the Moon may have been vital to the evolution of life on Earth. But when they talk about a "super big" asteroid smashing up the Moon, they are doing so in a joking way ("for years we'd have to wear hard hats").

Those kind of massive collisions occurred billions of years ago... one of them probably created the Moon when a Mars-sized planet smashed into the Earth... but all the objects that big are now in stable orbits where they can't smash into each other anymore.

See Copernicus (Lunar crater): it's 800 million years old, and is considered a relatively young crater (see the article)... and that was far, far, far too small an impact to have any chance of breaking up the Moon (you need a telescope to see that crater from Earth, see the lower image on the Copernicus (Lunar crater) page). -- Curps 22:22, 11 Mar 2005

(UTC)

The article cited is part of a larger work about possible earth ending scenarios, the gallows humour of his writing style doesnt mean the subject matter is a "joke". Wikipedia is not original research, we report on what others say. That you personally don't think this could happen doesnt mean it should not be reported. Your certainly free to edit the text to reflect the highly unlikely probabability. The fact is, we dont know all the objects in earths orbit. We dont know what objects might end up in our orbit, say, from the Kuiper Belt. Also who is to say the moon would be "destroyed" it could be knocked off orbit which would knock earths orbit off. Stbalbach 23:06, 11 Mar 2005 (UTC)

Sorry, but I wonder if you're familiar with astronomy. The article you cite makes a serious point about the importance of the Moon for the evolution of life on Earth but merely jokes about us having to "wear hard hats for years" if some "super big" asteroid ever hit the Moon. The article is not seriously suggesting this possibility at all. You are not reporting on what others say, rather you are taking an intentional lighthearted joke seriously.

Please reread what I wrote above about Copernicus crater. The solar system is believed to be about 4.5 billion years old, and the Moon is completely covered with craters. Yet nearly all of those craters are older than 800 million years old... and even those craters are mere craters, caused by objects much, much too small to cause the Moon to break apart or move out of its orbit. The period of intense bombardment ended billions of years ago, and there is simply nothing left in the inner solar system that has both the right orbit and size to break up the Moon.

The Kuiper belt is not a credible source for Moon-smashing asteroids, please cite a reference if you think it is. There are large objects out there, but not only would collisions be very rare, but even if one did occur it would be very, very close to impossible for such a collision to alter the orbit in such a way that it would cross the Earth's orbit (consider the angular momentum that objects have all the way out there, and what it would take to bring them into the inner solar system... remember, we're not talking about mere comets from the Oort cloud, but an object with the size and mass of Sedna or even Pluto).

In a few billion years the Sun will swell up to become a red giant and engulf the Earth and Moon. Based on the last few billion years, we can pretty confidently predict that the odds of the Moon being smashed into fragments by an object during those next few billion years is less than the odds of you or me being struck by lightning in the next five minutes.

-- Curps 23:56, 11 Mar 2005 (UTC)

Thank you for the explanation.

There are people saying the moon is a danger to civilization. It is notable. If you can think of some way of linking the End of Civilization to this article, that needs to be done in some way. What do you suggest? Stbalbach 00:21, 12 Mar 2005 (UTC)

I suggest removing the line about the Moon from End of Civilization. That's an interesting article, with a lot of potential, its credibility shouldn't be marred... there simply is no credible non-facetious scenario involving the Moon blowing up. -- Curps 03:09, 12 Mar 2005 (UTC)

By the way, I followed the link on the End of Civilization page and created an article on Gliese 710. The latest estimate is that its passage may increase the net cratering rate by 5%, which is not much... but at least that's not completely negligible. The moon-blowing-up probability is, I'm afraid (entirely negligible, that is). -- Curps 03:45, 12 Mar 2005 (UTC)

This calls for a new article: Exploding Moon . Thanks for the Gliese article. Stbalbach 06:43, 12 Mar 2005 (UTC)

No, you have not shown us anybody, that says "the moon is a danger to civilization". The article you refer to says, without the moon life would get tougher, and uses a scenario that his highly unlikely to create the effect of removing the moon for illustrative purposes. This is not a notable discussion of the End of Civilization. Awolf002 01:39, 12 Mar 2005 (UTC)

I agree with Awolf, there. I just read the article in question and the "Moon gets destroyed by an impact" scenario appears to be solely intended as an intro to lead into a discussion of "what if the Moon wasn't there?" If the Moon were magically blown up somehow the last thing we'd be worried about would be Earth's axis becoming unstable over geologic timescales; we'd have bigger concerns in the form of kajillions of tons of moonrock falling on us. :) Unless there's some other source for concerns about this "threat", I don't think it's worth mentioning here. Bryan 04:00, 12 Mar 2005 (UTC)

The Exit Mundi web site, and article, are explicit about this being a possible End-Of-World scenario. Of course Exit Mundi is not an expert, but, it is a very popular and well known web site, at least in popular culture, it is notable. But just as Exploding whale has not breached the Whale article, my guess is Exploding Moon would likewise be shot down from The Moon. Stbalbach 06:43, 12 Mar 2005 (UTC)

This is intriguing. Obviously, the absence of the Moon is more "unhealthy" to humans than its existence. It would definitely be a mis-classification to call the Moon a "Danger to civilization"! I wonder, if the people at "Exit Mundi" actually think that the piece about the Moon says what Stbalbach thinks it does... As I said, I do not think so. Awolf002 19:53, 12 Mar 2005 (UTC)

I agree that the "Exit Mundi" article is not intended to propose an actual "Moon blows up" scenario, just making the point that "intelligent life wouldn't have evolved without the Moon being there". I don't understand why Stbalbach insists on taking a few clearly facetious remarks at that website seriously. -- Curps 20:12, 12 Mar 2005 (UTC)

The Exit Mundi website is a collection of End of the World Scenarios. Have you looked at it? Stbalbach 03:41, 13 Mar 2005 (UTC)

Yes I have and it's an interesting site, and the authors deal with subjects with an excellent sense of humor. We've argued about this for a while now. The conditions that could result in something smashing the Moon apart existed in the very early days of the solar system. They don't exist now. The South Pole-Aitken basin, mentioned in the exitmundi.nl article, is believed to be 3.9 billion years old [4]; it is literally the oldest observed feature on the Moon. There was a lot of extremely large debris flying around in those early days, but it's just not there anymore, as a result of multiple collisions and objects ejected out of the solar system in those very early days. By contrast, in the last 0.8 billion years there have been no more than a handful of impacts on the Moon that would even create a moderate-sized crater like Copernicus (less than 100 km in diameter). -- Curps 04:17, 13 Mar 2005 (UTC)

We seem to be talking at cross purposes. I am not disputing your position. It would be better said in an article than a talk page. Stbalbach 00:23, 14 Mar 2005 (UTC)

Verifying data

User:B.d.mills pointed out discrepancies between the infobox and other table so I tried to check some against references. Before the long checklist below, does anyone know what references were used for the data in the infobox and tables? I would like to add reference footnotes to the infobox at some time.

JPL's HORIZONS System gives:

Revised: Mar 11, 1998             Moon / (Earth)                            301

PHYSICAL PROPERTIES:
Radius, km            = 1737.53+-0.03   Mass, 10^20 kg        =  734.9
Density, gm cm^-3     =    3.3437       Geometric albedo      =    0.12
V(1,0)                =   +0.21         GM, km^3/s^2          = 4902.798+-.005
Earth/Moon mass ratio = 81.300587       Surface gravity       =    1.62 m s^-2
Nearside crust. thick.= 58+-8 km        Farside crust. thick. = ~80 - 90 km
Heat flow, Apollo 15  = 3.1+-.6 mW/m^2  Heat flow, Apollo 17  = 2.2+-.5 mW/m^2
Mean crustal density  = 2.97+-.07g/cm^3 k2                    = 0.0302+-.0012 
Induced magnetic mom. = 4.23x10^22Gcm^3 Magnetometer moment   = 435+-15

DYNAMICAL CHARACTERISTICS:
Mean angular diameter = 31'05.2"        Orbit period          = 27.321582 d
Obliquity to orbit    = 6.67 deg        Eccentricity          = 0.05490
Semi-major axis, a    = 384400 km       Inclination           = 5.145 deg
Mean motion, rad/s    = 2.6616995x10^-6 Nodal period          = 6798.38 d
Apsidal period        = 3231.50 d       Mom. of inertia C/MR^2= 0.3935+-.0011
beta (C-A/B), x10^-4  = 6.31(72+-15)    gamma (B-A/C), x10^-4 = 2.278(8+-2)

infobox comparision

JPL's Radius gives a diameter of 3475 km but no oblateness, while the article gives an equatorial diameter of 3476.2, and a polar diameter of 3472.0, and an oblateness of (3476.2 - 3472.0) / 3476.2 = 0.0012. Close enough I'd guess.

JPL's Density rounds nicely to the infobox figure of 3.344 g/cm3.

Infobox Gravity of 1.622 is more accurate than JPL.

JPL's mass of 7.349x10^22 is different from the article's Infobox Mass of 7.347673x10^22, which however is consistent with a lunar mass calculated from (Earth's mass) 5.9736×10^24 / 81.300587 of 7.3475x10^22, within the error limits.

Orbital period (sidereal I assume) matches to 5 figures.

Semi-major axis matches.

Eccentricity (mean assumed) however is somewhat different with the infobox's 0.0554 compared to JPL's 0.0549. Could this be due to different definitions of mean, or the mean is taken over different time period? It seems the Moon's perigee varies by +/- 2% over the year, with the apogee varying by only around +/- 0.5 % (see http://www.fourmilab.ch/earthview/pacalc.html), so maybe the eccentricity is that of an idealised orbit (a perfect ellipse?) before the Sun's influence is applied (I'm not an expert here).

I see the German de:Mond gives perigee as 356410 km, which looks suspiciously like the nearest the Moon gets to the Earth at any time, and not a typicial perigee, nor a layman's average perigee. Maybe this should be explained?

Other table comparison

Eccentricity of 0.0549 matches JPL's (and the German article) but differs from the infobox.

Mean perigee of ~364397 km and mean apogee of ~406731 km are different from the infobox and are not consistent with the table's eccentricity. Using d_a=apogee, d_p=perigee from :$e={{d_{a}-d_{p}} \over {d_{a}+d_{p}}}$ where $d_{p}\,\!$ is perigee and $d_{a}\,\!$ is apogee, e is (406731 - 364397) / (406731 + 364397) = 0.05489879 (contrast 0.0549003), while the infobox figures give e = (405696 - 363104) / (405696 + 363104)=0.0554006243 (consistent with 0.0554). Rounding errors for the table data don't seem to explain the contrast.

Table's Mean inclination of orbit to ecliptic orbital of 5 degrees 9 minutes appears rounded from the infobox's 5.145396° (5 degrees 8.72376 minutes) which is consistent with JPL's 5.145.

I didn't check anything else, and I may well have made errors myself! -Wikibob | Talk 20:41, 2005 Mar 13 (UTC)

The Moon's semi-major axis revisited

Something smells really rotten with the data. We do have down-to-the-centimetre measurements of the Earth-Moon distance (using laser telemetry), so how come the mean semi-major axis is so poorly documented? Using JPL's data, which works really well for the planets, we have the following situation: using their value for the solar GM product, for the Sun/Earth+Moon mass ratio and the Earth/Moon mass ratio, we can work out that:

• GM (Sun) = 132,712,440,018 km³/s²
• GM (Earth) = 398,600.4 km³/s²
• GM (Moon) = 4,902.80 km³/s²

The Moon's mean sidereal period is well attested: 27.321661 d. If you then work out the semi-major axis from the GM and period values, you get...380,073 km! The Earth-Moon distance (centre to centre) is 384,748 km, using the same data. Whence the oft-quoted 384,400 km, then?

See also Talk:Jupiter#Revising_the_sidereal_period. Urhixidur 21:16, 11 October 2005 (UTC)

Okay, part of the mystery resolved: the semi-major axis used in all astronomical measurements is not the barycentre to orbiting body distance, but the total primary-to-secondary distance. So, in the Moon's case, the JPL data gives a semi-major axis of 384,748 km. We're still off by 348 km (about 1 in 1000), which seems a bit much considering the precision of the numbers involved.

Urhixidur 11:56, 13 October 2005 (UTC)

Indeed, the JPL stated error bars yield a lunar semi-major axis of 384,747.957±0.008. Inverting the calculation, the period obtained from the semi-major axis of 384,400 km is 27.284606 d, an error of at least 0.04 d. A similar discrepancy occurs when those same GM values are used to compute the Earth's sidereal period: we get 365.25641 but JPL states it is 365.25636 d —the error is much smaller, although still larger than the JPL error bars.

Urhixidur 18:44, 13 October 2005 (UTC)

buying land on the moon?

I've been bought a plot of land on the moon as a birthday present. A certain Mr Dennis M Hope claims to own the moon, and his pal Francis P Williams (Lunar Ambassador to the united Kingdom)from MoonEstates.com claim to be the only authorised reseller of lunar land. They also claim they own the other planets too. Is this worth the paper its written on? Can someone really own an astronomical object just because the law on earth about ownership pretty much allows anything? Has my friend been conned?Soloist 14:07, 24 Mar 2005 (UTC)

See Outer Space Treaty. — Monedula 14:20, 24 Mar 2005 (UTC)

Hopefully not terribly much so. These guys end up on the news every now and again for the laugh effect. For now, the moon and other celestial bodies remain under the common property of all mankind, like the oceans. In historical practice land ownership has come from incumbency of some kind on the land in question. If you're ready to stake your claim and put up a homestead on the moon, then by all means, go for it. Otherwise, enjoy the worthless piece of paper. --Alexwcovington (talk) 17:16, 24 Mar 2005 (UTC)

Online moon maps and photo resources

Are there any other online moon map and photo resources that support direct links with URLs indicating latitude and longitude? If there is, then I thought it would be cool to extend the concept of Wikipedia:WikiProject_Geographical_coordinates to also including the moon, and perhaps also planets and starmaps. For your enjoyment, I have made some experiments on Amundsen (crater) and Aristoteles (crater) sattelite craters. The map sources currently know about the Clementine images, the LPI moon atlas plus NASA World Wind with the moon add-on. -- Egil 10:42, 25 Mar 2005 (UTC)

The reaction was one of skepticism. Ive been told there is little value in the online images, and that the perspective one might reach by navigation of this kind on the moon is probably without value (I personally found travelling, starting from one of the craters, exploring the neighborhood using NASA World Wind moon overlay quite fascinating. But then I am only a total novice on this subject.) I have thus reverted the changes to navigatable coordinates, and left them as pure unstructured text. If someone wants to pursue at a later date, that is of course possible. Just use the ideas from Wikipedia:WikiProject_Geographical_coordinates, adding the attribute globe:Moon. -- Egil 08:02, 26 Mar 2005 (UTC)

No, my reaction at least was that it was a very interesting idea that worked very poorly in practice, because of the marginal quality of the available online image sources. As I mentioned on your talk page, lookup by latitude/longitude (as opposed to lookup by feature name) works very poorly with the Orbiter images website (a limitation or bug of that site's lookup feature), and the online Clementine images website also leave a lot to be desired (mediocre resolution and detail, no labels, not really useful except for the largest craters). As for World Wind, I haven't tried it but it requires installing special software on each user's PC, requires a high-speed Internet connection, really needs a 3D accelerator graphics card (ie, user's PC must be less than two years old), so it won't be available to most users. If someone ever implements an online map of the Moon that works something like Mapquest.com, this idea could definitely be revived. -- Curps 13:28, 26 Mar 2005 (UTC)

The moon images of World Wind are in fact part of the installation, so an Internet connection is not required for the Moon layer. Except for initial downloading of the layer, of course (the hi-res is 40 megabytes of compressed data, the low-res 3-something). That said, I've been told an Internet connection is required to enjoy Wikipedia properly, also. -- Egil 15:53, 26 Mar 2005 (UTC)