<p>This question is handeled pretty throughly in Physics site; 
<a href="https://physics.stackexchange.com/questions/214042/earths-kinetic-energy-change">https://physics.stackexchange.com/questions/214042/earths-kinetic-energy-change</a></p>

<p>Your question; "How big is the difference?"</p>

<p>Body Tides Summarize<br>
0.3 ms for a 14 day period.<br>
0.16 ms for a 28 day period<br>
0.14 ms for 1/2 year period<br>
0.02 ms for a year period.<br>
0.126 ms for Lunar node period; (18.6 years)  </p>

<p>Ocean Tides<br>
Max 0.05 ms for a 14 days period<br>
0.026 ms for a Years period<br>
0.024 ms for lunar node period  </p>

CC BY-SA 3.0
2016-06-23T10:39:32.620Z
2016-06-23T10:39:32.620Z
2017-04-13T12:40:15.470Z
Jokela
<p>Many of us are familiar with an exaggerated picture of the Moon's effect on Earth's tides:<a href="https://i.sstatic.net/WPbGj.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/WPbGj.jpg" alt="enter image description here" /></a></p>
<p>Since the Earth is not uniformly covered with water, however, I imagine that the tidal effect will depend on which part of the Earth is facing the Moon (for simplicity, ignore the Sun's contribution).  I'm sure that the tidal effect still affects the Earth's landmasses, but I'm guessing that it would be to a lesser degree (i.e.: the landmasses would bulge out less than the oceans in the image above).  Now, by conservation of angular momentum, if the landmasses bulge out less, the Earth should rotate more quickly, hence this question's title.</p>
<p>How does the tidal effect of the Moon's gravity affect the Earth's landmasses differently from its oceans?  And how big is this difference?</p>

CC BY-SA 3.0
2016-06-20T13:43:52.893Z
Look up solid earth tides.   The Earth does bulge but not as much as the oceans.  About 20 cm on average, in places and at times over 30 cm but that's probably sun and moon together.  (I'd post the link but it's giving me trouble, not hard to look up).   Also, interesting point on rotation velocity/conservation of angular momentum, and apparently that happens too, brief summary here:  http://bowie.gsfc.nasa.gov/ggfc/tides/intro.html
userLTK
CC BY-SA 3.0
2016-06-21T09:26:42.240Z
The "bulge under the moon" model is probably too simplistic to use here, since the tidal wave is not uninterrupted around the planet. I guess the pertinent question is "Is the change of the planet's angular momentum over a tidal cycle more than a negligible fraction of the total angular momentum of the planet?" - whether that change be from differences in global mean sea surface elevation, or differences in speed or direction or whatever.

I haven't done the maths, hence not a full answer, but my instinct is that the answer is "no".
Semidiurnal Simon
<earth-rotation><moon><tides><gravity>
How much do tides affect earth's rotational velocity?
Ben Sandeen
# How much do tides affect earth's rotational velocity?

(Asked by: username_0 on 2016-06-20)

Many of us are familiar with an exaggerated picture of the Moon's effect on Earth's tides:[![enter image description here](https://i.sstatic.net/WPbGj.jpg)](https://i.sstatic.net/WPbGj.jpg)

Since the Earth is not uniformly covered with water, however, I imagine that the tidal effect will depend on which part of the Earth is facing the Moon (for simplicity, ignore the Sun's contribution). I'm sure that the tidal effect still affects the Earth's landmasses, but I'm guessing that it would be to a lesser degree (i.e.: the landmasses would bulge out less than the oceans in the image above). Now, by conservation of angular momentum, if the landmasses bulge out less, the Earth should rotate more quickly, hence this question's title.

How does the tidal effect of the Moon's gravity affect the Earth's landmasses differently from its oceans? And how big is this difference?

**Tags:** earth-rotation, moon, tides, gravity

> **Comments:**
> **username_1**: Look up solid earth tides.   The Earth does bulge but not as much as the oceans.  About 20 cm on average, in places and at times over 30 cm but that's probably sun and moon together.  (I'd post the link but it's giving me trouble, not hard to look up).   Also, interesting point on rotation velocity/conservation of angular momentum, and apparently that happens too, brief summary here:  http://bowie.gsfc.nasa.gov/ggfc/tides/intro.html  
> **username_2**: The "bulge under the moon" model is probably too simplistic to use here, since the tidal wave is not uninterrupted around the planet. I guess the pertinent question is "Is the change of the planet's angular momentum over a tidal cycle more than a negligible fraction of the total angular momentum of the planet?" - whether that change be from differences in global mean sea surface elevation, or differences in speed or direction or whatever.  I haven't done the maths, hence not a full answer, but my instinct is that the answer is "no".  

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## 1 answers

### Answer by username_3 on 2016-06-23. Score: 1

This question is handeled pretty throughly in Physics site;
<https://physics.stackexchange.com/questions/214042/earths-kinetic-energy-change>

Your question; "How big is the difference?"

Body Tides Summarize  
0.3 ms for a 14 day period.  
0.16 ms for a 28 day period  
0.14 ms for 1/2 year period  
0.02 ms for a year period.  
0.126 ms for Lunar node period; (18.6 years)

Ocean Tides  
Max 0.05 ms for a 14 days period  
0.026 ms for a Years period  
0.024 ms for lunar node period


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