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Author Topic: What is the moon made of, and why do we only have one?  (Read 3650 times)

Stephanie

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Stephanie asked the Naked Scientists:

I just wanted to say I absolutely love your show.  I listen to it while doing housework, in the car, and while working.  The children that come on the show are very polite.  I am impressed with their manners and wish the children here in the U.S. where as polite. (I am in San Antonio, TX)

I did want to ask what exactly our moon is made of and how is it that we have one moon while other planets have several or none?  

Thanks in advance for considering my question.

What do you think?
« Last Edit: 05/07/2008 13:30:01 by chris »


 

Offline Soul Surfer

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Re: What is the moon made of, and why do we only have one?
« Reply #1 on: 04/07/2008 10:21:40 »
Quick simple answers

1 The moon is made of rock quite similar to a lot of the rocks on the earth  we have samples of it from the moon missions and meteroites

2 we have only one moon because it is a big one and it would disturb any other moons that tried to join our system and throw them back out into space
 

Offline graham.d

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Re: What is the moon made of, and why do we only have one?
« Reply #2 on: 04/07/2008 22:27:20 »
What?? Not cheese after all?
 

Offline RD

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Re: What is the moon made of, and why do we only have one?
« Reply #3 on: 04/07/2008 22:34:45 »
Quote
More Moons Around Earth? Its Not So Loony
 By Robin Lloyd
Senior Science Writer
29 October 1999

Earth has a second moon, of sorts, and could have many others, according to three astronomers who did calculations to describe orbital motions at gravitational balance points in space that temporarily pull asteroids into bizarre orbits near our planet.

The 3-mile-wide (5-km) satellite, which takes 770 years to complete a horseshoe-shaped orbit around Earth, is called Cruithne and will remain in a suspended state around Earth for at least 5,000 years.

Cruithne, discovered in 1986, and then found in 1997 to have a highly eccentric orbit, cannot be seen by the naked eye, but scientists working at Queen Mary and Westfield College in London were intrigued enough with its peregrinations to come up with mathematical models to describe its path.

http://www.space.com/scienceastronomy/solarsystem/second_moon_991029.html
« Last Edit: 04/07/2008 22:36:19 by RD »
 

Offline DoctorBeaver

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Re: What is the moon made of, and why do we only have one?
« Reply #4 on: 05/07/2008 08:21:46 »
There are at least 3. First, there is the one we are all familiar with. And sorry, Graham, it is not made of cheese.

A second, which has been named Cruithne, was discovered in 1986. Cruithne doesn't orbit the Earth in the way the first moon does. It's orbit is highly eccentric.



The 3rd moon to be discovered has the inspiring name J002E3. This one was discovered in 2002. It may be an asteroid that has been captured by the Earth's gravity. Its distance from Earth varies between 840,000km & 300,000km. It circles the Earth every 49.5 days. And it is small. In fact, it is very small; about 50metres across.

However, there is a bit of a twist in the tail of J002E3. It is just possible that it is an old rocket body that has wandered far away from the Earth and gone into orbit there. Scientists need to check it out more thoroughly to find out.
 

Offline Karen W.

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What is the moon made of, and why do we only have one?
« Reply #5 on: 09/07/2008 14:54:05 »
Quick simple answers

1 The moon is made of rock quite similar to a lot of the rocks on the earth  we have samples of it from the moon missions and meteroites

2 we have only one moon because it is a big one and it would disturb any other moons that tried to join our system and throw them back out into space


Do you mean it would push it away by the force of "gravity"??
 

Offline Soul Surfer

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What is the moon made of, and why do we only have one?
« Reply #6 on: 09/07/2008 18:56:58 »
No precisely the opposite it would attract other satellites towards it but the counterintuitive effect is that eventually the object will do a close pass towards the moon and get thrown out of orbit.  of course the object could hit the moon or the earth as it does this but that's not so likely. 

There are these Legrange points (as indicated in the beaver's nice picture)  where small objects can stay in reasonably stable positions in orbit for a limited period of time but the effect of the moon is to eventually distrub them and throw them into unstable orbits.
 

Offline RD

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What is the moon made of, and why do we only have one?
« Reply #7 on: 24/07/2008 18:54:34 »
Qi Re: Cruithne ...
NR=1
 

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What is the moon made of, and why do we only have one?
« Reply #7 on: 24/07/2008 18:54:34 »

 

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