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Subject: waves in a lake ?? rss

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Jon
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Explain waves to me, if you can.


Here's my question...

If you go to a lake, there are waves coming in to the shore. If you go to the other side of the lake, there are waves coming in to the shore. No matter what side of the lake you go to, there are waves coming in to the shore.

It seems like if on one side of the lake, waves are coming in, maybe over on the other side, waves should be moving away from the shore?? But they never do.
 
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Clinton Smith
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Quote:
No matter what side of the lake you go to, there are waves coming in to the shore.


So the waves also move in the direction the wind is coming from?
 
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Paul DeStefano
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jwandke wrote:
But they never do.


They always do.

Look again.

Each wave recedes.

It's a circular motion, under the surface of the lake.
 
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Paul DeStefano
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Koldfoot wrote:
Aren't waves technically vertical motion, not horizontal motion?


That's kind of what I meant with the circular motion, but yours is clearer.
 
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JessA
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I always thought of waves as ripples on a pond, moving outwards until they reach shore.
 
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Jon
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Koldfoot wrote:
Aren't waves technically vertical motion, not horizontal motion?


i don't know.

I'm on shore. i see a wave 20 feet away. it's a ridge of raised water. the ridge of raised water is going to appear to get closer to me, never farther.

?
 
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Jr
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It's really just the water moving up and down in the right tempo to produce the illusion that it's coming towards you. If you put a little rubber ducky on the water, it will just stay in the same place, bobbing up and down with the waves, unless there is some wind to move it along.
 
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Flannel Golem
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Here is my take, based upon some no doubt mis-remembered facts from some long-ago natural sciences class I was in:
Wind is generally the most obvious force responsible for causing waves; but as you state, even without wind little ripples of waves can still be seen to come in all around a lakeshore. As others have pointed out, this is an optical illusion created by vertical motion only -- not representative of horizontal water-movement. But it does appear as if the waves are created by some perceived "circular" force somewhere in the center of the lake. This subtle effect is in fact due to the spinning of the earth, making water in all largish planetary basins (lakes, seas, oceans etc.) weakly slosh around their basins like you might spin coffee around in your styrofoam coffee-cup.

Not unlike my caveat for rules in the games I teach: further 'scientific facts' shall be made up as needed as we go along wow
 
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Jeph Stahl
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Also, shores are usually shallower, which causes a wave to increase in height. So waves are easier to see near the shore.
 
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Michael Pennisi
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Well I guess this is my chance to be an "expert" for a change. The waves you see in a lake are the result fo a number of factors but first some general properties:

1. A wave is caused by a disturbance to a medium which, in this case, is the lake. This disturbance could be caused by anything: wind, rain, boats, currents in the water, otters, dead bodies being dumped etc... These waves then spread out (the technical term is "propagate") in all directions. So even if a eastward blowing wind is causing the disturbance some waves will still travel north, south, and west.

2. Waves that reach the shoreline do not necessarily end, they actually reflect back out into the lake. They do eventually stop due to friction between water molecules and because of (repeated) collisions with the shoreline. You may not notice this because another property of waves is that they can pass through each other. The outgoing waves tend to be smaller than the incoming waves so they aren't as noticeable.

3. To adress some previous comments: Waves on the surface of a body of water cause the water to move both up-and-down (transverse motion) AND side-to-side (longitudinal moton). If you could look at a side view of leaf bobbing on the surface of a lake, the motion of the leaf would be in a small circle. Waves also slow down as they approach shallow water.

Finally the rotation of the earth would not cause water in a lake to "slosh about" this would require changes to the earth's rotation rate. I could demonstrate this with a Greek waiters serving tray but you'd have to be here.

 
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chris schott
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while water may appear to be a single mass, it is of course an aggregation of a large number of very small particles or molecules. these particles are in constant motion, even when the body of water may appear to be perfectly still. in the case of waves, water molecules are moving both longitudinally and transversely. wave hieght is determined by wave length, shore slope and lake monster activity. these elusive creatures, refered to as "Natiaka" by native americans, are in fact living descendants of the plesiosaur and are directly responsible for anomalies in water oscillation.
 
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shumyum
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OK, if Natiaka is causing lake waves, what causes The Wave (often seen in sports stadiums around the world)???

I am NOT a molecule!!!!
 
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Jorge Montero
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shumyum wrote:
OK, if Natiaka is causing lake waves, what causes The Wave (often seen in sports stadiums around the world)???

I am NOT a molecule!!!!


Unlike normal waves, that are created by preturbations in a medium, The Wave is created by the lack of movement in a soccer field. The duller the game, bigger the waves. It's a pretty unique effect.
 
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Jon
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natiaka?

darn it, i think i now know less than i did before i asked the waves question.



by the way, has the question been answered yet? the high ridge of water moves toward the shore. why toward the shore?

i think it also might move toward the shore on all sides of an island? again, why toward?
 
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Michael Pennisi
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Waves made on water spread out in all directions "towards the shore" is a direction but it's not the only direction.

Oh and if you are thinking about waves made by a moving boat, those are called "bow waves" and they behave a bit differently (v-shaped trail) because the boat is usually moving faster than the waves it makes. Bow waves don't spread out in all directions.
 
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I'm free-basing midichloriens and the force is, like, an energy that connects and penetrates us all, man.
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Okay. Think about this. In a standard swimming pool, the waves are "stationary" - that is, the water is still moving (if there is any wind), but there are no "waves" approaching a "shore" - because there is no shore: Instead the water's waves are evenly disbursed over the entire medium, and entirely non-circular in appearance.

Now, if a swimming pool were built with very sloping sides, the water would approach and recede onto your artificial "beach", just as it does in a lake.

If you have a cereal bowl with shallow sloping sides, you can test this: fill the bowl, and blow into the water. The water displaced by your "wind" laps up the sides, falls back down, and generates oscilating "waves".

it is therefore obvious: your breath contains microscopic plesiosaurs.
 
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