h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

That's ok - I was working it out myself as I wrote it. Interestingly, the Moon is apparently moving away from us, which means that it is gaining in energy as the years go by. Don't know why this is the case, but it might be some residual of the initial impact that separated the Moon from the Earth in the first place.

Woodpigeon

That would make sense. I can't think of anything else that could be causing it.

Well yes, but the moon is also being pulled away from us by the sun to some extent. Give it time and you won;t get total eclipses of the sun as the only reason we get them now is because of a fluke whereby the distance of the moon and sun from us coincides exactly with the size difference factor. A factor of 400 somewhere along the line. Any way, as the earth gets closer to the sun, the moon moves away from the earth and the sun grows eventually that coincidence will be gone.

It's a pity because solar eclipses are beautiful, especially when you get the 'diamond ring' effect

No solar eclipses isn't an issue, the Moon is being slowed down by tidal forces and so it's dropping in energy and its orbit is slowly degrading. Give it enough time and there will be one hell of a collision between the Earth and the Moon

Hang on, why have two other people said it's moving away from us then?

Because that is what should be happening, with every other planet in the solar system (with the possible exception of Pluto, but that's a freak anyway) the satellites are either plunging relatively faster or getting flung out. The only reason the Moon is coming down is because of the large amounts of water on Earth, which is slowing it down

The moon *is* moving away by a rate of 2 inches a year - the Earth is imparting tidal energy to the moon apparently, which at the same time is slowing the Earth's rotation down. All in all, it balances out.

If you don't believe me, type "Moon moving away Earth" into Google.

Woodpigeon

I'm just going on what my Physics A Level teacher said, he always did have a flair for the dramatic. I'm quite happy to bow to a more learned authority

Here's a link for that more learned authority: http://www.faqs.org/faqs/astronomy/faq/part5/section-21.html *starts eating humble pie*

Now this may be complicating the situation a little bit , but what effect do you reckon the other two naturally occurring satellites around the Earth (including the second "moon" Cruithne) have?

On the moons movement?
Theoretically the satellites will move closer together, however I feel the practical effect will be very little.
Just out of interest, how big is cruinthe and can it be seen by the naked eye? Whats the other satellite?

Have you seen a depiction of cruinthe's orbit? Talk about complex. i mean the Moon's orbit is bad enough, but cruithne's! There's a thread round here somewhere all about cruithne and stuff where I posted a link to a pretty web page with applets in it showing the orbit.

Apparently, according to at least one site I went to, the earth is moving away ffrom the sun by about 3cm a year due to similar effects between it and the sun as those between the earth and the moon.

I heard that too.
An the theme of astrology is Pluto a planet?
I have heard evidence that says both yea and neigh!

The body that governs these things said in 1999 that pluto is officially a planet. As Bill Bryson puts it: 'We need all the neighbours we can get'

Cruinthe isn't very big (probably only tens of kilometres across) and doesn't come particularly close to the Earth (40 times the distance between the Earth and the Moon is the closest it reaches) - it probably isn't visible to the naked eye, as it was only discovered in 1986 by using telescopes. Although its horseshoe-shaped orbit around the Earth is also quite interesting ... more info can be found here: -

http://www.space.com/scienceastronomy/solarsystem/second_moon_991029.html

The other satellite is called J002E3 - although this is more likely to be a former booster rocket from an Apollo lunar mission ... again more info can be found here: -

http://ali.opi.arizona.edu/cgi-bin/WebObjects/UANews.woa/2/wa/SRStoryDetails?ArticleID=6102

Considering how big these objects are and close to the Earth they are compared to the Moon, I also doubt that they will have any significant effect on the Moon's moving away from the Earth. (But then, I'm no astrophysicist!)

Me neither, but thanks for the info!

'tis here :- F19585?thread=318828&post=4099765#p4099765
i think ;-0

Pluto is only a planet because of when it was found. There's bigger stuff out there but we now have limits on what size a planet must be.

Check out the links. Oh, and the pluto is a planet is still not finally decided but many now consider it to not be one.

Pluto is a planet until or unless scientists start to discover other Pluto-sized objects further out in a region of space known as the Kuiper Belt. They are pretty confident they will find objects the size of Pluto, and possibly even bigger. Last year an object half of Pluto's size (Quaoar) was found.

And by the way the discussion is on Astronomy, not Astrology!

Woodpigeon

aye, and Quaoar is a planet if you use the modern 700km definition.
Or should it be 'new I Can;t Believe It's Not a Planet'

And as for the re-classification of pluto then there will be those who want it to maintain its distinction for historical reasons. After all, rules is not rules unless you have an exception!