The Naked Scientists

The Naked Scientists Forum

Author Topic: How was the moon formed?  (Read 715 times)

Offline RTCPhysics

  • Full Member
  • ***
  • Posts: 63
  • Thanked: 2 times
    • View Profile
How was the moon formed?
« on: 02/08/2015 15:10:51 »
There appears to be some mystery about how the earth's moon was formed. The favoured theory is that it was created by a glancing blow from a massive object the size of Mars. But our current knowledge of the moon's rocks shows that they are identical to the earth's rocks and do not contain any foreign material absorbed from another celestial object.

This fact can be explained by a completely different process, but one which still requires a compact object of some size to pass near to the earth during the early days of its formation. The earth was then a fluid molten mass, which meant that the approach of the 'massive object' would create a strong gravitational attraction between the two bodies of matter. The power of this gravitational attraction changed the shape of the earth from a spherical body into a pear shaped body. As the massive object came to its closest approach to the earth and moved past it, two events happened. The tip of the pear began to split off from the earth to eventually create the moon and the ongoing attraction of the moving massive object as it departed the earth, gave both the earth and the moon the same angular momentum. So when the moon split from the earth, it rotated around the earth at the same speed as the earth rotated on its own axis.

With the departure of the massive object and the removal of its gravitational pull, both the moon and the earth continued to rotate together held by their mutual gravitational attraction, but both changed shape back to a rough sphere, drawn in by their own internal gravitational attraction.

The strength of this process is that it explains why the earth and its moon have similar rock surfaces, simply because the moon was created purely from the earth and why the two bodies rotated initially at the same speed.
   
« Last Edit: 09/09/2015 17:41:38 by RTCPhysics »


 

Offline PmbPhy

  • Neilep Level Member
  • ******
  • Posts: 2762
  • Thanked: 38 times
    • View Profile
Re: How was the moon formed?
« Reply #1 on: 02/08/2015 15:32:34 »
Quote from: RTCPhysics
But our current knowledge of the moon's rocks shows that they are identical to the earth's rocks and do not contain any foreign material absorbed from another celestial object.
No no no!! Where did you get that idea from? That's quite wrong. The moon rocks are very different from Earth rocks.
 

Offline chiralSPO

  • Global Moderator
  • Neilep Level Member
  • *****
  • Posts: 1877
  • Thanked: 143 times
    • View Profile
Re: How was the moon formed?
« Reply #2 on: 02/08/2015 22:05:14 »
While the geology and chemistry of the moon is quite different from Earth's, I understand that the relative abundance of various isotopes indicates that the moon and Earth are very likely to have the same source.
 

Offline chiralSPO

  • Global Moderator
  • Neilep Level Member
  • *****
  • Posts: 1877
  • Thanked: 143 times
    • View Profile
Re: How was the moon formed?
« Reply #3 on: 02/08/2015 22:08:11 »
The tip of the pear began to split off from the earth to eventually create the moon and the ongoing attraction of the moving massive object as it departed the earth, gave both the earth and the moon the same angular momentum. So when the moon split from the earth, it rotated around the earth at the same speed as the earth rotated on its own axis.

With the departure of the massive object and the removal of its gravitational pull, both the moon and the earth continued to rotate together held by their mutual gravitational attraction, but both changed shape back to a rough sphere, drawn in by their own internal gravitational attraction.

The strength of this process is that it explains why the earth and its moon have similar rock surfaces, simply because the moon was created purely from the earth and why the two bodies rotate at the same speed.
   

But the two DON'T rotate at the same speed! And we know that they started out even more different than they are now. Slowly they are getting synced, but it won't happen for billions of years...
 

Offline RTCPhysics

  • Full Member
  • ***
  • Posts: 63
  • Thanked: 2 times
    • View Profile
Re: How was the moon formed?
« Reply #4 on: 05/08/2015 09:17:28 »
An analogy for this process is the athlete in the hammer throwing event of athletics. The spherical ball attached by a chain, slides through the air around the spinning athlete at the same speed of his rotation in the circle. The chain attachment ensures that the same face of the ball is always pointing inwards towards him. In a similar manner, the moon and earth are attached by their mutual gravitational attraction and the moon slides through space around the earth with the same face always pointing inwards. It doesn't spin on an axis like the earth.

There are a couple of further points of clarification to make about this process. The stream of material from the molten earth drawn towards the passing celestial object, reaches its maximum at their nearest distance apart. As the celestial object continues away from the earth, its gravitational pull upon the tip of the material stream is greater than the earthís pull upon it, which causes the tip of the stream to break away, forming the moon.

The earth and its 'new' moon continue to be held together by their mutual gravitational attraction and the moon rotates around the earth at the angular velocity that was imparted by the pull of the departing celestial object. This is akin to the hammer thrower turning on his rotational path in the throwing circle before release. But unlike the hammer thrower where the chain departs with the ball, the earthís gravitational field, being stronger than the moonís, draws the remaining stream of earth material back into itself. This process causes the earthís rotation about its axis to speed up rapidly, the effect being similar to the experience of being spun in a revolving chair with oneís legs outstretched and then drawing them in to create a boost to the rotational rate of the chair.

The earth's spin rate and the moon's orbital velocity are not the same after the moonís formation. The increased spin rate of the earth from this drawing back in of its extruded material, does not affect the strength of its gravitational link to the moon, which continues to slide through space in its orbit around the earth. The earth and the moon take on their eventual spherical shape driven by their internal gravitational attraction and the subsequent hardening of their outer crusts.

This process of extruding material also explains why the earth's rotational axis is tilted with respect to its orbit around the sun. As the celestial object passed by the earth, outside its orbit around the sun but below its horizontal equatorial plane, the extrusion of material shifted the earth's centre of gravity outwards, thereby tipping the earth's rotational axis away from its original vertical plane.

« Last Edit: 07/08/2015 17:48:50 by RTCPhysics »
 

The Naked Scientists Forum

Re: How was the moon formed?
« Reply #4 on: 05/08/2015 09:17:28 »

 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums
 
Login
Login with username, password and session length