Moon's gravity

[wurf]

Why does our moon's gravitational attaction cause movement of large amounts of earth's liquid seas, but no movement of lighter solid matter, such as dust or grains of sand?

 

[MeteorWayne]

Actually it moves the whole crust of the earth, as well as the oceans. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[wurf]

I was referring to things unattached to and resting upon the crust. If something as massive as the earth's crust is affected, why not less massive bits of matter?

 

[MeteorWayne]

Well they are affected as well, but are not going to float above the surface because the gravity of the earth is far more powerful at that distance. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[agnau]

It probably affects them the same way, but you are looking at a liquid compared to a friction surface of rocky particles. Water is a very simple liquid with a simple construction while these rocky particles we call sand can be made up of several layers of longer molecules at the very least (likely thousands layered in all three dimensions). Each grain of sand therefore experiences a lot more friction to stay in place... but as the tides affect the wind, and gas is much more fluid than the ocean, you could say that each and every wind on the beach is in some way influenced by the moon and therefore every grain of beach sand blown by the wind is affected by the moon... this is of course, if you don't like the real explanation given -- each grain ways more and is subject to the friction and gravity of the earth on which it rests.

 

[3488]

The lunar tides are about 1 in 3 billionth the strength of Earth's 'surface gravity'.<br /><br />In short, enough to cause tides in the oceans & to a lesser extent the Earth's crust<br />but not enough to lift things off the surface.<br /><br />Just as well really.<br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[MeteorWayne]

If you jump up when the moon is overhead, and say woooooo, you actually get lighter for a few milliseconds <img src="/images/icons/laugh.gif" /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[3488]

Same here <img src="/images/icons/laugh.gif" /> <img src="/images/icons/laugh.gif" /> <img src="/images/icons/laugh.gif" /><br /><br />Perhaps I'll try MeteorWayne's weight loss plan. <img src="/images/icons/laugh.gif" /><br /><br />Andrew Brown. <div class="Discussion_UserSignature"> <p><font color="#000080">"I suddenly noticed an anomaly to the left of Io, just off the rim of that world. It was extremely large with respect to the overall size of Io and crescent shaped. It seemed unbelievable that something that big had not been visible before".</font> <em><strong><font color="#000000">Linda Morabito </font></strong><font color="#800000">on discovering that the Jupiter moon Io was volcanically active. Friday 9th March 1979.</font></em></p><p><font size="1" color="#000080">http://www.launchphotography.com/</font><br /><br /><font size="1" color="#000080">http://anthmartian.googlepages.com/thisislandearth</font></p><p><font size="1" color="#000080">http://web.me.com/meridianijournal</font></p> </div>

 

[wurf]

Thanks all for the answers and comments.

 

[agnau]

The trick is, since the moon's mass is so much smaller, you will have to make this jump from a significant point on the earth to have a noticeable effect. Try jumping up from Everest.... just don't miss your landing.

 

[willpittenger]

Well, you could cheat.<br /><br />1. Put a 100 pound weight on your scale.<br />2. Zero it out.<br />3. Remove the weight.<br />4. Next time you weigh yourself, you will be 100 pounds lighter. <div class="Discussion_UserSignature"> <hr style="margin-top:0.5em;margin-bottom:0.5em" />Will Pittenger<hr style="margin-top:0.5em;margin-bottom:0.5em" />Add this user box to your Wikipedia User Page to show your support for the SDC forums: <div style="margin-left:1em">{{User:Will Pittenger/User Boxes/Space.com Account}}</div> </div>

 

[kelvinzero]

Something just occured to me. Could having a large ocean reduce the tidal bulge of the crust and thus slow the process of becoming tidally locked to the moon?<br /><br />My point is when the tide rises by meters, eg when moon is overhead, those extra meters of water sitting on the rock reduces the amount the rock would move. Moving water to create the bulge causes far less friction than moving rock, and friction is a force, so less work has been applied, so less change in (angular)momentum.

 

[nexium]

I think you are correct. If Earth did not have large oceans, our day might get a whole second longer each year, instead of the typical part of one second longer. Neil

 

[tony873004]

What surprises me is that the Moon doesn't have much effect on our weather. The atmosphere, like the oceans, should experience tides, causing a higher atmosheric pressure where there is a high atmospheric tide. It seems that this high pressure coming and going twice a day should have some influence on weather. Perhaps it does, but it is insignificant.

 

[Saiph]

The earth's crust does rise and fall by ~2 feet due to lunar tides. The reason we don't see sand shifting in giant tides is because the solid particulates and the crust itself can be seen as very, very viscous liquid.<br /><br />As such it doesn't shift laterally much at all. <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>