Talk:Lunar Laser Ranging Experiment

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Contents

[edit] Science results?

Can this article include a section on the science results? What was found? is it significant? What interesting things have been found out? e.g. tidal forces? magnetic dragging? earthquakes? solar wind effects? General relativity results? ??? linas 00:47, 30 October 2005 (UTC)

I whole heartedly agree. Behold, and marvel in the splendor of Wiki! -Mr.Logic 03:21, 15 January 2006 (UTC)

The statement

- Einstein's theory of gravity and the general theory of relativity predict the moon's orbit to within the accuracy of the laser ranging measurements.

leads to a followup-question: Do Newtonian mechanics not? I mean, that fact is an interesting piece of support for relativity theory only if it's not only due to relativity theory yielding almost the same answer as Newtonian mechanics.

- Theoretically, no. Much in the same way that the perihelion of Mercury precesses about the Sun due to General Relativity, you'd expect the Moon to do the same about the Earth. I don't know whether this effect would really be measurable in the Earth-Moon system using LRRR. Anyone have a calculator?  :-)

On a different note, I found the phrase "The moon is spiraling away from Earth at a rate of 3.8 cm per year, due to the Earth's ocean tides" very interesting. This makes it sound like the moon is moving away because of the tides, which is kind of accurate and kind of not accurate. It's not really the tides themselves that create this effect, but rather the recoil effect of the ocean tides on the land masses that cause the problem. If the Earth had no continents and the ocean depth was uniform then this wouldn't be an issue. So you can't really blame the tides directly.

Toddbu 10:06, 8 April 2006 (UTC)toddbu

Please add this to the article if you can explain it concisely and what exactly is the cause - as a layman I don't understand your reference to the recoil effect. Tempshill 15:54, 29 August 2007 (UTC)

[edit] distance

this article says the moon moves away from earth at 3.8cm per year. The Moon article says it's 38mm. which is correct? - 01:33, March 14, 2006 by user 68.7.188.123

Try this link for an answer: http://www.google.com/search?hl=en&q=3.8cm+in+mm -Mr.Logic 16:10, 14 March 2006 (UTC)

[edit] Lunokhod in NSSDC

The article previous contained the following:

(Note that NASA's NSSDC catalog confuses Lunokhod 1 and Lunokhod 2 on this issue: [1], while more accurate references can be found at [2] and [3]).

As of today, NSSDC looks correct. Their Lunokhod 2 page says "The Lunokhod laser retroreflector is still used by Earth-based stations for laser ranging", and their Lunokhod 1 page says nothing. gparker 04:11, 13 July 2006 (UTC)

[edit] So what is the precise distance (within experimental error) ?

The article begins with outlining the (initial) purpose of the LLRE, namely to measure the (average ?) distance to the Moon. But the article doesn't say what this value is ! Surely this value (whatever it is) should be mentioned. MP (talk) 12:00, 27 September 2006 (UTC)

[edit] question

the article says: "The moon is spiraling away from Earth at a rate of 3.8 cm per year, due to the Earth's ocean tides."

I see how tidal friction stopped the moon from rotating, but how can the tides (or continental drift or whatever) affect the moon's orbit? the mass of the earth is always the same (except for meteor dust-- which *increases* it, pulling the moon closer). even if all the water were piled up on the other side of the planet somehow, the center of mass of the earth would be in the exact same place. Sys Hax 10:15, 12 October 2006 (UTC)

Perhaps you should ask on the Science Help Desk, but I think the reason is that the tides cause the Earth's rotation to slow, thus losing angular momentum. The Earth/Moon system has to conserve angular momentum, so the Moon has to move farther away. Bubba73 (talk), 01:19, 30 May 2007 (UTC)

I'm with Sys Hax on this: I think you have to put energy into the earth - moon system in order to get the moon to move further out. I'd expect the moon to be drifting closer as tidal friction bleeds energy from the system. Gbr1918 12:12, 14 September 2007 (UTC)

Think in terms of the conservation of angular momentum, "The conservation of angular momentum in Earth-Moon system results in the transfer of angular momentum from Earth to Moon (due to tidal torque Moon exerts of Earth). This in turn results in the slowing down of the rotation rate of Earth (at about 42 nsec/day), and in gradual increase of the radius of Moon's orbit (at ~4.5 cm/year rate)." Bubba73 (talk), 21:26, 30 November 2007 (UTC)

[edit] Accuracy

The article references future improvements in accuracy, and agreement with special relativity to with current accuracy -- does anyone know what current the accuracy of measurement is? —The preceding unsigned comment was added by 190.40.130.44 (talk) 17:27, 16 April 2007 (UTC).

I think it is on the order of 3cm, but don't rely on that. Bubba73 (talk), 01:21, 30 May 2007 (UTC)

[edit] OWNED!

SUCK IT, conspiracy theorists! You're wrong. Will you finally admit it now? —Preceding unsigned comment added by 63.245.164.227 (talk) 21:25, 29 February 2008 (UTC)