Question why does the moon move around the earth

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Discussion Overview

The discussion revolves around the question of why the Moon orbits the Earth rather than falling into it under the influence of gravity. Participants explore concepts related to orbital mechanics, the nature of gravitational forces, and the historical formation of the Moon.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions why the Moon does not collide with the Earth due to gravity.
  • Another participant explains that the Moon maintains its orbit because it is moving at the correct orbital speed.
  • A claim is made that stable orbits are possible due to gravity following an inverse square law, contrasting it with a hypothetical inverse cube law that would lead to unstable orbits.
  • One participant suggests that the Moon is actually moving away from the Earth at a rate of a millimeter per year.
  • A participant raises further questions about the origin of the Moon's orbital speed and how it maintains this speed over time.
  • A prevailing theory is presented regarding the Moon's formation from debris resulting from a collision between Earth and another body, with different outcomes for the debris based on kinetic energy.
  • It is stated that no energy is required to maintain an orbit once established.

Areas of Agreement / Disagreement

Participants express various viewpoints on the mechanics of the Moon's orbit and its historical formation, indicating that multiple competing views remain without a clear consensus.

Contextual Notes

Some claims depend on assumptions about gravitational laws and the historical context of the Moon's formation, which are not fully resolved in the discussion.

shobat
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question why does the moon move around the Earth why it doesn't hit the Earth under the effect of gravity??
 
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because the moon is moving with a velocity that is the orbital speed, so it stays in orbit
 
stable orbits are possible because gravity follows an inverse square law
if gravity followed an inverse cube law then all orbits would be unstable and would eventually spiral outward to infinity or inward to the planet surface.
 
shobat, do a google search on "Newton's orbital cannon".
 
the moon is actually moving with more velocity then the velocity orbital speed, so it is moving around a millimetre away from the Earth every year
 
seto6 said:
because the moon is moving with a velocity that is the orbital speed, so it stays in orbit
but why did the moon have orbital speed in the first place and how does it have the same energy to continue with same speed (this question about satellite and other planets too).
 
shobat said:
but why did the moon have orbital speed in the first place
The prevailing theory is that the Moon was created when a collision occurred between Earth and another body. This sent much of protoEarth flying in a spray of rubble. The fate of the rubble can be classified into three categories:
- rubble that acquired little kinetic energy simply fell back to what remained of the Earth, becoming part of the current Earth.
- rubble that acquired a lot of kinetic energy was lost from the Earth system
- rubble that had juuuuuuust enough kinetic energy ended up neither falling back to Earth, nor escaping completely. This rubble continues to this day to ride the narrow line between falling back to Earth and escaping completely. We call it the Moon.


shobat said:
and how does it have the same energy to continue with same speed (this question about satellite and other planets too).

It requires no energy to stay in orbit.
 

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