Why does the moon orbit the sun?

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Discussion Overview

The discussion revolves around the dynamics of the Moon's orbit in relation to the Sun, exploring concepts of momentum and angular momentum, as well as the conceptualization of the Earth-Moon system as a single entity in orbit around the Sun.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant asserts that the Earth orbits the Sun due to its initial momentum and questions whether the Moon also possesses initial momentum.
  • Another participant expresses uncertainty about the term 'initial momentum' but suggests that both the Earth and the Moon have angular momentum, which would need to be dissipated for them to fall into the Sun.
  • Several participants propose the idea of visualizing the Earth and Moon as a single entity orbiting the Sun, with one noting that this perspective is common despite potential inaccuracies.
  • A participant introduces the concept of 'horse shoe' orbits, where small satellites can have complex paths near the Earth's orbit, questioning whether such satellites should be classified as orbiting the Earth or the Sun.

Areas of Agreement / Disagreement

Participants express differing views on the nature of the Moon's orbit and the concepts of momentum involved. There is no consensus on the definitions or implications of these concepts.

Contextual Notes

Participants have not fully defined terms such as 'initial momentum' and 'angular momentum,' leading to potential misunderstandings. The discussion also touches on the complexities of classifying orbits, which may depend on specific definitions and contexts.

avito009
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I know that Earth orbits the sun because it has initial momentum and that prevents it from falling into the sun. But does moon that orbits the Earth also have initial momentum?
 
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I don't know what 'initial momentum' is. As far as I understand, both the Earth and the Moon have angular momentum which they would need to get rid of in order to fall into the Sun.
 
I aways imagine the Earth and moon as a single item orbiting the sun
 
dean barry said:
I aways imagine the Earth and moon as a single item orbiting the sun

That is indeed one way you can imagine it if you aren't worried too much about accuracy.
 
dean barry said:
I aways imagine the Earth and moon as a single item orbiting the sun
That's how we mostly think of it. However, the situation can arise where you get a so called 'horse shoe' orbit where the orbit of a small satellite follows a horse shoe shaped path which lies near to the Earth's orbit. There are a number of asteroids that actually do this. See this Wiki link. It is a moot point whether you would consider the satellite as orbiting around the Earth or the Sun. This could be another example of where insisting on classifying the orbit as one or the other is more trouble than it's worth.:smile:
 

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