morpheus moon thing

[formula86]

Hi. i'm new here and i have a ques. i'm watching this thing on the science channel called What If We Had No Moon. there is a theory that the moon was formed because orpheus hit the earth and the particles/dust that circled the earth eventually collected to make the big moon.
my ques is: how/why would the particles collect to make the moon? wouldn't they hit each other and make more particles? i know that the particles were more that 14,000 miles (i think) and out of a certain sphere and that's why they didn't get sucked back into the earth. but how would they all collect? how was there gravity?

thanks in advance! :)

[Frisbinator]

I don't know.

[Pete]

...but how would they all collect? How was there gravity?

There is gravity between all massive objects. Gravity between the orbiting pieces of debris would pull them together over time.

[Silverback]

Ok, then what about the asteroid belt? Are those objects colliding (seldom, over time) to create more broken bits, or are they pulling together into a single larger object? It would seem the same rules would apply.

[John Connellan]

There was one huge asteroid belt at the start of the solar system where the asteroids were large enough, and close enough to be pulled together to form planetesimals. There is a threshold of size for a planetesial where its gravity is so strong that even when large objects collide with it, it is pulled back together.
Our present day asteroid belt is the remnants or those asteroids which could not form planetesimals because they were too small or too far apart.

[Communist Hamster]

Whats orpheos? is it the name for the mars type object that hit us?

[Vortexx]

wasn't the earth for a large part molten rock at that time ? Wich is why the moon was just a large semi-liquid blob scooped out of the earth, while perhaps the asteroid/debris belts are result of moons colliding that where already cooled to solid state?

[Iris]

http://www.psi.edu/projects/moon/moon.html
http://www.cnn.com/TECH/9707/28/moon.collision/
http://physicsweb.org/article/news/5/8/13
http://news.bbc.co.uk/1/hi/sci/tech/2780399.stm

Dunno where they got "Orpheus" from--the giant-impact object that collided with Earth has been named "Theia".

[Pete]

Ok, then what about the asteroid belt? Are those objects colliding (seldom, over time) to create more broken bits, or are they pulling together into a single larger object? It would seem the same rules would apply.

The asteroid belt contains only about 1/20th the mass, and is spread over a hugely larger area than the debris that made the Moon.