Question about the Sun's gravitational influence on the Earth and its moon

Click For Summary

Discussion Overview

The discussion revolves around the gravitational influence of the Sun on the Earth and its moon, specifically questioning why the moon does not appear to revolve around the Sun independently, despite the Sun's significant gravitational force. The scope includes conceptual clarifications and technical explanations regarding orbital mechanics and gravitational interactions.

Discussion Character

  • Conceptual clarification
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants question why the moon does not revolve around the Sun if the Sun's gravitational force is strong enough to influence larger bodies like Jupiter.
  • One participant explains that the Earth and moon orbit a common center of gravity, which itself orbits the Sun, suggesting that initial conditions and Newton's laws of gravity govern their stable orbits.
  • Another participant notes that the Sun's gravitational effect on the Moon is more than twice that of the Earth, leading to a convex trajectory for the Moon as it orbits the Sun.
  • It is mentioned that the Earth-moon system's orbit around the Sun is elliptical, with specific distances provided to illustrate the relative scale of the moon's orbit compared to the Earth-Sun distance.
  • Participants discuss the minimal observable effect of the moon's wobble in its orbit around the Sun, emphasizing that it does not reverse direction in its path.
  • There is a mention of three-body systems where a moon-like body can have a horseshoe orbit around a Sun-like body while following the path of an Earth-like body, which may add complexity to understanding the moon's motion.

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding the moon's orbit and gravitational influences, with some clarifying misconceptions while others remain uncertain about the implications of these gravitational interactions. The discussion does not reach a consensus on the initial question posed.

Contextual Notes

The discussion includes assumptions about gravitational influences and orbital mechanics that may not be fully articulated, and the complexity of three-body systems is noted as potentially confusing.

Evenlander
Messages
3
Reaction score
0
If the sun has a gravitational influence on Earth and on its moon then why isn't the moon revolving around the sun. If the gravitational force of sun is large enough to make planets like Jupiter revolve around it (which has a greater mass than that of the moon.) Why not moon?
 
Astronomy news on Phys.org
Evenlander said:
If the sun has a gravitational influence on Earth and on its moon then why isn't the moon revolving around the sun. If the gravitational force of sun is large enough to make planets like Jupiter revolve around it (which has a greater mass than that of the moon.) Why not moon?

What makes you think the Moon is not orbiting the Sun?
 
  • Like
Likes   Reactions: russ_watters, vanhees71, Vanadium 50 and 2 others
Hello Evenlander, :welcome: !

Earth and moon orbit around a common center of gravity. That center of gravity orbits around the sun. Matter of initial conditions and Newtons law of gravity. Once the orbits are stable there 's a lot of momentum needed to change them.

Jupiter has moons too
 
  • Like
Likes   Reactions: Evenlander
PeroK said:
What makes you think the Moon is not orbiting the Sun?
I never thought about this. Thanks.
 
  • Like
Likes   Reactions: Dale
Evenlander said:
I never thought about this. Thanks.
To be more specific, the Earth-moon system's orbit around the sun is 149.6 +/- 0.5 million km in radius (it's elliptical). The moon is 0.36 million km from Earth, or about 0.2% of that distance. If you animated that and deleted the Earth, you probably wouldn't even notice the wobble in the moon's orbit around the sun.
 
  • Like
Likes   Reactions: Dale
russ_watters said:
you probably wouldn't even notice the wobble in the moon's orbit around the sun.
Around +/- 0.2% of wobble (about 300 thousand km in 150 million km), with about 13 cycles of 'wobble' on the way round. It never 'goes backwards' in its orbit round the Sun.
There are three body systems where the 'moon' body has a horseshoe orbit around the 'sun' body, whilst more or less following the orbital path of the 'earth' body. That link can be initially confusing.
 

Similar threads

  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 3 ·
Replies
3
Views
873
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 19 ·
Replies
19
Views
3K
  • · Replies 16 ·
Replies
16
Views
5K
  • · Replies 4 ·
Replies
4
Views
6K
Replies
17
Views
4K
  • · Replies 11 ·
Replies
11
Views
4K
  • · Replies 6 ·
Replies
6
Views
2K