Could the Moon's Shape Explain Why We Only See One Side?

  • Context: High School 
  • Thread starter Thread starter richbass
  • Start date Start date
  • Tags Tags
    Moon
Click For Summary

Discussion Overview

The discussion revolves around the reasons why the Moon presents only one face to the Earth, exploring concepts related to tidal locking, the Moon's shape, and mass distribution. Participants engage in theoretical reasoning and technical explanations regarding gravitational effects and the Moon's physical characteristics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that the Moon's center of gravity being offset from its center point could explain why the same side faces Earth, questioning the role of tidal forces.
  • Another participant counters that the Moon is tidally locked to the Earth, emphasizing that this phenomenon is not coincidental and relates to gravitational interactions rather than mass distribution.
  • Some participants argue that the explanation involves the Moon's quadrupole moment and its non-spherical mass distribution, indicating a more complex interaction than simply having a heavier side.
  • A later reply asserts that the Moon's shape is more ellipsoidal and that gravitational forces from Earth cause it to maintain its orientation, while also addressing misconceptions about crust thickness and mass.

Areas of Agreement / Disagreement

Participants express differing views on the mechanisms behind the Moon's tidal locking, with some supporting the tidal forces explanation and others proposing alternative models related to mass distribution and shape. The discussion remains unresolved with multiple competing perspectives.

Contextual Notes

Participants reference concepts such as the quadrupole moment and the implications of the Moon's shape, but there are unresolved assumptions regarding the definitions and implications of these terms. The discussion also touches on the relationship between gravitational forces and physical characteristics without reaching a consensus.

richbass
Messages
12
Reaction score
0
Here's another observation of nature

"I don't think the moon's spin cancels it's orbit (causing the same side to face us) by tidal forces or by accident. That would be one big coincidence. I think that the moon's center of gravity is offset from it's center point along it's diameter. So "The heavy side faces us"

Is this mentioned somewhere? I couldn't find it. If not does anyone agree that this could be possible?" or am I again "out of my mind"?
 
Astronomy news on Phys.org
No, it's not by "accident" nor does it follow that one side must be heavier than the other- the moon is "tidally locked" to the earth. Why do you say you don't think it could be caused by tidal forces? That's certainly not a coincidence!

Do you understand what is meant by "tidally locked"? It has nothing to do with the tides on earth- more to do with "tides" on the moon!

Here is a good explanation:
http://en.wikipedia.org/wiki/Tidal_locking
 
Last edited by a moderator:
It is not just the heavier side facing us.
It's more complicated than that. It has to do with the quadrupole moment of the moon due to non-spherically symmetric distribution of it's mass.
 
Meir Achuz said:
It is not just the heavier side facing us.
It's more complicated than that. It has to do with the quadrupole moment of the moon due to non-spherically symmetric distribution of it's mass.

non-spherically symmetric distribution of it's mass? Doesn't that mean it's center of gravity is offset from it's center of mass?
 
No, the moon is basically football-shaped (an ellipsoid) and since the force of Earth's gravity on the near-side is greater than that on the far-side (because of the distance), it stays in that orientation. The Earth technically has an ellipsoid component as well (same reason - the tides), but it is very small compared to Earth's rotation-induced oblateness.

The link you provided before that mentioned the crust being thicker on the other side doesn't mean that side is heavier - the crust is thin and light.
 
Last edited:

Similar threads

High School Why can we only see one side of the moon?
  • · Replies 13 ·
Replies
13
Views
3K
High School The Sun's Influence on the Moon's Orbit: Is it Negligible?
  • · Replies 4 ·
Replies
4
Views
3K
High School Can a Planet Have a Moon that Never Casts a Shadow?
  • · Replies 19 ·
Replies
19
Views
3K
Undergrad Tidal effects on Earth's rotation and moon's orbit
  • · Replies 10 ·
Replies
10
Views
5K
Undergrad Have you ever wondered why we can't see the other side of the moon?
  • · Replies 10 ·
Replies
10
Views
2K
High School Why are we still limited in our Moon exploration ambitions?
  • · Replies 22 ·
Replies
22
Views
3K
Undergrad How Big of an Object Orbiting Closer to the Sun Than Earth Could Be Overlooked?
  • · Replies 17 ·
Replies
17
Views
4K
High School Miscellaneous Trivia: Planets and Moons
  • · Replies 7 ·
Replies
7
Views
3K
Graduate How Does Lower Moon Mass Affect Its Orbit Distance from Earth?
  • · Replies 9 ·
Replies
9
Views
8K
High School Earth's Hubble velocity and measuring Hubble at large distances
  • · Replies 5 ·
Replies
5
Views
2K