Because an engineer tested this and found the correct water pressure to lift the sphere just a little bit on the water. And the craftsmanship needs to be spot on. No dents or big imperfections on the sphere, a perfect fit with equal water dispersal on the pedestal.

It can happen to cars too when rain water accumulates on the road. If they go fast enough the tires lose contact with the ground and the car will become unsteerable.

If the water pressure was high enough to spray out, the ball would simply fly off. It's the perfect equalization of the weight if the ball and the pressure of the water. You can do this yourself at home. Try this:

Find a marble that fits the opening of your garden hose perfectly. The hold you garden hose upright, place the marble on top (do NOT hold it in place), and begin turning the the valve until you reach the correct pressure. You'll notice that without enough pressure, nothing happens at all, and with too much pressure, the marble will fly off the top of the hose.

It's a balancing act

My advice: (not to OP.) Block this guy. I don't think he understands that he's not on Reddit and karma doesn't matter. He's trolling and wasting your time. He asked, people answered, and now he's just arguing. Troll behavior. I'm blocking him, and my Lemmy experience will be better for it.

https://en.wikipedia.org/wiki/Kugel_fountain Is it this kind of thing you're asking about?

I know this is No Stupid Questions, but has something happened to Lemmy?

Is someone inflitrating lemmy with a load of troll accounts designed to rile up outrage?

If it were concentrated to one small hole, it would. The same way putting your thumb over the end of a water hose will make the water spray farther. The wide base around the bottom of the sphere gives enough space for the water to come out without squirting far.

Here's one that does squirt out more than most: https://youtu.be/yEeEU-WRbP0

Maybe they have the water pressure too high, maybe the tolerances are too low, the sphere doesn't fit the cup quite right, so they need higher pressure for it to spin. Considering the shape of the base, I think they designed it this way, though. I like the water splashing out of the bottom, that makes it more interesting.

Why should it squirt out? Who would want that? Think about basics:

Pressure is force divided by area.

The weight of the ball (downward force) equals the upward force from the water pressure, then it can float.

You want the water pressure to be about 1 bar (equal the air), so it does not squirt out.

From that you get: weight of the ball divided by the partial area of the ball that is in the water equals 1 bar.

That's how big and how heavy your ball must be, then it works.

To oversimplify the answer, if you put a strong enough 'garden hose' beneath the floating sphere, you would still get that 'spraying effect' like you do with a garden hose. However, the sphere would no longer 'float' in place in thst case.

Keep in mind that the floating sphere 'uses the energy of the spray to stay aloft', balanced against the weight of the sphere. As a result, there is not enough energy left to make the water spray outward like the garden hose does.

There are many different factors at work to keep the sphere afloat, such as the curved base below it, matching the sphere's curvature. Again this is an oversimplified explanation, to help explaon the basic concept.

GMU’s Manassas campus has something like this; I think it has something to do with the pressure of the water within the basin resulting in an ultra-thin, low-friction “cushion” for the ball to rotate on.

Must be magic, like you're thinking.

because that force is translated into making the ball spin

S Q U A R T

Surface tension?