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PoppersOfCorn t1_jdl1cos wrote

I think it spread out until level. Remember, down is towards the centre of mass

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zakabog t1_jdl27g0 wrote

Depends, is the earth still rotating? If so, pretty much the same way as the winds. You'd have some local variations due to the weather, but more or less it would behave like the wind.

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PoppersOfCorn t1_jdl47ko wrote

Replying to Ausmerica (#2,348,352)

Because the volume of water wasn't mentioned, I just thought of a small amount.

If it was oceans of water, it would certainly bulge at the equator like it already does, but it would still have to spread out to find a level.

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Representative_Pop_8 t1_jdl49gr wrote

to the equator due to earth spinning , it would try to form a ( smooth version of) shape like that of earth which is larger at the equator due to spinning

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Ausmerica t1_jdl5eo6 wrote

Replying to JesseLaces (#2,348,359)

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.

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Fleaslayer t1_jdl6z0s wrote

Replying to JesseLaces (#2,348,359)

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.

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kompootor t1_jdl73qj wrote

[Edit: It seems like lots of commenters are interpreting this question quite differently. I interpreted OP as imagining an initial condition of an effectively 2-dimensional single-molecule-thick free surface of the Earth. I think I did this because otherwise I wasn't sure how the "smooth sphere" assumption would have been particularly necessary.]

Water drifts toward the equator. If there is already stuff there, like the surface has a bunch of water, or it's smooth and in moving the water has to climb up to move over from its initial position (since the Earth begins as perfectly smooth), then you have a complication where once the water gains altitude it is moving "too slowly" compared to the linear speed at that larger distance from the Earth's center. Thus the water appears to drift backwards (West) until friction with the surface below brings it to the "correct" speed that is locked with the rotation of Earth. The Westward drift from gaining altitude is of course the coriolis effect. If it's just a single drop of water that has to climb up once over the hard surface, then that's all there is to it, and it can continue onward [Edit: I'm dumb -- as the drop moves toward the equator, its distance from the axis of rotation of the Earth of course increases (i.e. that is the "horizontal" component of the radius), so the drop continually finds itself moving too slow for the Earth underneath -- thus still appearing to drift Westward.] -- unless the surface is frictionless I suppose?

If in this scenario the Earth is an entire (2D) ocean of water, then it gets especially interesting, as the water will try to bunch up at the equator and reach an equilibrium height with a bell-shaped curve outward. The formation process will keep the water moving East-West currents parallel to the equator until it reaches equilibrium, at which point it all has to come to rest.

If you add our Moon in there, with tides, then you'll definitely have continuous currents from the coriolis effect, since the water will be moving both vertically and in whatever off-axis (or even on-axis) direction the Moon is orbiting in this scenario.

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SFFcase t1_jdl7fod wrote

Wouldn’t the rotation of the earth bring the water to the equator? Bulge and all that…

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ferrel_hadley t1_jdlevi1 wrote

Replying to HeebieMcJeeberson (#2,348,237)

>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.

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ferrel_hadley t1_jdlf63q wrote

oceans flow east to west
https://en.wikipedia.org/wiki/Ocean_current#/media/File:Corrientes-oceanicas.png
On Earth this flow is interrupted by continents that form the great ocean gyres. There would be a flow induced by thermohaline pressure differences, that is in the poles water would cool and freeze out making it cold and salty, this would pull currents into the deep that would imitate the Great Conveyer
https://en.wikipedia.org/wiki/Thermohaline_circulation
But without the land masses messing it up.

The planet would also be circled by belts of winds, closer to the abstract 3 cell circulation models.

https://en.wikipedia.org/wiki/Atmospheric_circulation#/media/File:Earth_Global_Circulation_-_en.svg

These would affects surface current directions and thermohaline by evaporating some places and making water salty and raining other places and making its salt concentration drop.

So sort of how they work today without continents.

BUT the great huge steaming elephant in the room would be lack of CO2 sequestration from rock weathering. Spin up an Earth with a few exta kilometers of water to make it Water World and you wuold get huge build ups of CO2 over millions of years.

But here we go from a model running for a month to a model running for a couple of million years.

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HeebieMcJeeberson t1_jdlgk5n wrote

Replying to JesseLaces (#2,348,359)

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.

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RoughSalad t1_jdliqy0 wrote

Towards and away from the moon, like on the bumpy sphere.

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mfb- t1_jdln32i wrote

Replying to ventus1b (#2,349,739)

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.

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mfb- t1_jdln9ub wrote

Replying to ferrel_hadley (#2,349,511)

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.

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-technocrates- t1_jdlnioc wrote

towards center of gravity.

if perfectly smooth, then all "surface" directions. adjusted for momentum and spin.

edit: added "surface"

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lezboyd t1_jdlr4ss wrote

If I remember it right, the motion of water on earth, at least the oceans, is dictated by the tidal forces of the moon and the spinning of the earth, and sometimes also due to sub-ocean earthquakes. Regardless of the earth's shape, these forces would still be active.

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NotAHamsterAtAll t1_jdlzpn9 wrote

Depends a bit on things not mentioned.

If earth was floating alone in the universe, it would spread out evenly and freeze to ice.

If earth was rotating, it would cause more water to be around equator (this is the case today).

If earth was orbiting the sun and had a moon, the gravity from these two bodies would also affect the water (tides).

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PelosiGalore t1_jdlzqvp wrote

Depends on which direction the solar winds were blowing 😀

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alphagusta t1_jdmixrp wrote

Replying to SFFcase (#2,348,876)

Correct but that also brings in a sort of fun paradox

The earth cannot be a perfectly smooth exact sphere if the rotational energy is enough to bring the water to the equator first

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PhilsTinyToes t1_jdmjd98 wrote

Can’t magically avoid friction. That’s kinda the whole question here I think. Where would the remaining friction/earth forces move the water if it was rounded off like a cue ball.

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SiriusX151 t1_jdmnwan wrote

Like water flying off a wet ball in motion. that slightly bulges at what would be the "equator" but stay due to gravity. To dumb it down.

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Mumblesandtumbles t1_jdndni5 wrote

It is weird to think that if a regulation billiards ball were to be upsized to that of earth, it would have more drastic topographic features.

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HeebieMcJeeberson t1_jdnt69n wrote

Replying to IronSmithFE (#2,351,765)

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.

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HeebieMcJeeberson t1_jdx0byy wrote

Replying to ventus1b (#2,349,739)

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.

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