Does the sun or the moon have a greater affect on the tides?

Click For Summary

Homework Help Overview

The discussion revolves around understanding the mathematical basis for tidal forces, specifically comparing the influence of the moon and the sun on tides. The original poster expresses a belief that the moon has a greater effect and seeks clarification on the mathematical transition from gravitational force to tidal force, particularly the significance of the 1/r³ relationship.

Discussion Character

  • Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants explore the mathematical derivation of tidal forces from gravitational force equations, questioning how the relationship changes from 1/r² to 1/r³. There is also a focus on the variation of gravitational force across the Earth due to the moon's proximity.

Discussion Status

Several participants are engaged in clarifying the mathematical concepts involved. Some have suggested looking into existing resources, such as the Wikipedia article on Tidal Force, which may provide a derivation relevant to the discussion. The conversation is ongoing, with multiple perspectives being explored.

Contextual Notes

Participants note the importance of understanding the spatial derivative of gravitational force and how it relates to the phenomenon of tides. There is an acknowledgment of the complexity involved in deriving the tidal force equation, particularly for points on the Earth's surface.

Vitani11
Messages
275
Reaction score
3

Homework Statement



I know the moon does. I know it is because tidal forces fall off as 1/r3. But why? Mathematically, I mean.

Homework Equations


F = GMm/r2

The Attempt at a Solution


None
 
Physics news on Phys.org
Vitani11 said:
I know the moon does. I know it is because tidal forces fall off as 1/r3. But why? Mathematically, I mean.
In what way does this statement not contain both the question and the answer?
 
I should have been more specific. How do you get from F = GMm/r2 to an equation for tides that has a 1/r3 in it?
 
Vitani11 said:
I should have been more specific. How do you get from F = GMm/r2 to an equation for tides that has a 1/r3 in it?
Did you try a search on Tidal Force? Even the Wikipedia article on Tidal Force shows a short derivation (granted it's for the locations lying along the line joining the centers of the two interacting bodies, but it avoids the vector math required for the more general solution for points located anywhere on the surface of the smaller body).
 
Vitani11 said:
I should have been more specific. How do you get from F = GMm/r2 to an equation for tides that has a 1/r3 in it?

Tides result because of the variation of the force of gravity. Points on the side of the Earth near to the moon are more strongly attracted than points on the far side.

In other words, the tides are not caused by the force of gravity which is proportional to 1/r2 but rather by the variation in that force over a distance the size of the earth, that is to say the spatial derivative . And the derivative of 1/r2 is ...
 

Similar threads

  • · Replies 40 ·
2
Replies
40
Views
3K
  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 3 ·
Replies
3
Views
1K
  • · Replies 6 ·
Replies
6
Views
23K
Replies
1
Views
2K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 30 ·
2
Replies
30
Views
5K