Submitted by Axial-Precession t3_1219zfb in space
HeebieMcJeeberson t1_jdl116l wrote
On a smooth dry sphere it would flow toward the equator.
Loupax t1_jdmm8mt wrote
Also for Earth to be a smooth sphere, we must assume zero tidal forces.
Which doesn’t change the answer, but I thought that was an interesting point.
ventus1b t1_jdli5br wrote
Also if it was a perfectly smooth sphere where there is no friction to accelerate the water?
Wouldn’t the water then just sit as a sphere around the spinning earth?
mfb- t1_jdln32i wrote
If it's placed at rest relative to the ground then it would flow towards the equator.
If it's placed at rest relative to the center of Earth and we could magically avoid any friction (no surface can do that completely with water) then it would just spread out.
ventus1b t1_jdlozis wrote
Yes, thanks for reminding me of that distinction.
I was thinking of water at rest wrt to Earth. Or both at rest and Earth spinning up.
HeebieMcJeeberson t1_jdx0byy wrote
For one thing, perfect smoothness doesn't eliminate friction - there's also electrostatic attraction between molecules. Eventually the planet rotating under the water would coax it to move.
But moreover, the atmosphere would be screaming by overhead since it does rotate with the Earth. The atmosphere is chaotic, with zones of different pressures which press down on bodies of water unevenly, creating irregularities that the sideways wind can act on to create waves. This is how wind stirs up waves on calm, smooth lakes and such.
ferrel_hadley t1_jdlevi1 wrote
>On a smooth dry sphere it would flow toward the equator.
For a start there is no water on a dry sphere. Then there would be a slight centrifugal tug pulling water more towards the equator but Coriolis would be the dominant force.
mfb- t1_jdln9ub wrote
No, the Coriolis force is only a secondary effect from water moving towards the equator. That "slight" centrifugal force makes the equatorial radius of Earth 20 km larger than the polar radius, so if you use a perfect sphere and water equivalent to our oceans then all the water would be in a broad region around the equator and nothing would be at the poles.
wegqg t1_jdmde4w wrote
This is a really smart answer ^
HeebieMcJeeberson t1_jdx1mxl wrote
Mom: "How do you like your new shirt?"
ferrel_hadley: "For a start it's not new if I'm already wearing it."
Mom: "Go to your room."
IronSmithFE t1_jdm4wma wrote
what if the earth wasn't spinning?
Ulfgardleo t1_jdmw59w wrote
water would eventually evenly distribute around the globe and sit still
IronSmithFE t1_jdn7r6y wrote
would the waters surface tension pool the water together?
KyodainaBoru t1_jdti5q2 wrote
Surface tension is irrelevant at such a scale.
HeebieMcJeeberson t1_jdnt69n wrote
If the Earth weren't spinning then the water would spread out in all directions, stopping when the surface tension stopped it from getting any thinner. It would be a thin puddle beaded up on the surface. That is, unless the amount of water was enough to cover the whole planet - in that case it would cover the planet to an even depth.
JesseLaces t1_jdl2blr wrote
Towards instead of away as the earth spins? I feel like the poles would make more sense, no?
HeebieMcJeeberson t1_jdlgk5n wrote
The rotation will try to fling the water away from the Earth's axis, and the farthest place from the axis is the equator. No matter where you place the water, it will flow toward the equator since there's no terrain to stop it. In the real world, where ocean water is free to flow around, sea level at the equator is actually a little higher than near the poles for this reason.
[deleted] t1_jdmluwa wrote
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[deleted] t1_jdnslzu wrote
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You_Yew_Ewe t1_jdnze2x wrote
The magnitude of earth's gravity varies [pretty haphazardly across the globe](https://www.popsci.com/science/article/2010-06/esa-satellite-maps-earths-gravity-3-d/). It's not closely correlated with the equator.
Maybe you mean because of the sum of gravity and centrifugal force makes means the mass has less weight?
Ausmerica t1_jdl5eo6 wrote
I think I understand what you're trying to say, that water would sit at the poles since there will be less inertia there? But that would be missing the entire point of inertia, think about the practical applications that would often be labeled as centrifugal force. The fastest point on a spinning sphere is the equator.
Fleaslayer t1_jdl6z0s wrote
The earth is spinning and the mass wants to move to the outer edge of the spin, which is the equator, which is why the earth bulges a little there. For the same reason, the water would want to move to the equator.
ferrel_hadley t1_jdlkaj9 wrote
>arth is spinning and the mass wants to move to the outer edge of the spin, which is the equator, which is why the earth bulges a little there. For the same reason, the water would want to move to the equator.
capt-obvious-69 t1_jdmuwg8 wrote
It's the same principal behind Saturn's rings if that helps.
Axial-Precession OP t1_jdl2sst wrote
The Nile runs from south to north but I don’t know what the topology is like.
JesseLaces t1_jdl3tkw wrote
All rivers flow from high to low.
Also, the equator is below the Nile. Runs north away from the equator.
WorstMedivhKR t1_jdlyf4c wrote
Egypt is higher than sea level, therefore it runs south to north.
Macktologist t1_jdl329e wrote
You sure about that one?
[deleted] t1_jdl37fq wrote
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