Solar vs Lunar Tides: Explaining the Difference

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    Lunar Solar Tides
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Discussion Overview

The discussion revolves around the differences between solar and lunar tides, specifically addressing the comparative effects of gravitational forces exerted by the Sun and the Moon on Earth. Participants explore the mechanics behind tidal forces and the calculations involved in understanding these phenomena.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant states that lunar tides have an effect that is twice that of solar tides, despite the Sun exerting a greater gravitational force on Earth.
  • Another participant explains that the variation in gravitational force from the Sun across the Earth's surface contributes to tidal effects, suggesting that the difference in distance from the Sun to different points on Earth is significant.
  • A participant references a link to a resource that includes equations related to tidal forces, although the appropriateness of the reference is later questioned.
  • One participant challenges the validity of the linked resource, labeling it as promoting a "crackpot theory," but later acknowledges the need to clarify the mechanics of the inverse cube relationship in tidal forces.
  • Another participant notes that the tidal raising force is inversely proportional to the cube of the distance between the bodies and emphasizes that the tidal force is not the same as the gravitational attraction force.

Areas of Agreement / Disagreement

Participants express differing views on the appropriateness of certain references and the mechanics of tidal forces. There is no consensus on the best way to explain the relationship between gravitational forces and tidal effects.

Contextual Notes

Some participants mention the need for further clarification on the mechanics of tidal forces and the calculations involved, indicating that certain assumptions and definitions may need to be addressed for a complete understanding.

The Head
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I have a question about the effects of solar and lunar tides. I know that the effect of lunar tides is twice that of solar. However when I calculated the force of gravity of the Sun on the EArth vs the Moon on Earth using F=GmM/r^2 the force due to the Sun was much greater. Can anyone help me explain this? Thank you!
 
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The Head said:
I have a question about the effects of solar and lunar tides. I know that the effect of lunar tides is twice that of solar. However when I calculated the force of gravity of the Sun on the EArth vs the Moon on Earth using F=GmM/r^2 the force due to the Sun was much greater. Can anyone help me explain this? Thank you!

If you call the radius of the Earth ε, then you can see that the gravitation of the sun actually applies to points on Earth over a distance which varies from r-ε for the nearest point, to r+ε for the furthest point. It's this difference in gravity due to the difference in distance that generates the tides.

Now if you recompute the gravity difference between near and far points, you will see why the lunar tide is so large (hint: it has to do with the ratio ε/r).
 
Found this
http://oceanworld.tamu.edu/resources/ocng_textbook/chapter17/chapter17_04.htm"

Check out equations (17.12), (17.13), & (17.14)
 
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You're kidding me. You linked to a website that promotes a crackpot theory? Please don't tell me you believe that nonsense.

The tide raising force is indeed inversely proportional to the cube of the distance between the bodies.

Looking more closely at the link I agree it was an inappropriate reference as it is about something else entirely, so my apologies.

However I am suprised that no one has come into describe the mechanics of how the inverse cube relationship occurs so I will do that when I have time- It really is quite simple in principle. As oliversmsun says it is because the force due to gravitational attraction is not directly the tide raising force (TRF). The TRF stems from the difference between the forces of gravitational attraction and the forces due to the earth-moon or earth-sun mechanical systems revolving about their respective centres of mass.

Edit, thank you Gannet you posted whilst I was writing the above.
 

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