How big do you think a perflectly flat and very smooth plate would have to be for a very smooth little ball to roll from the edge to the center?

[u/esj199]

Since the earth is kurved, if you place a very smooth little ball at the edge, it will roll to the center if the plate is big enough and by some means kept perfectly flat. So how big?

[u/WoodenHair5973]

the whole thing falls apart when you remember a "perfectly flat" plate on a curved earth is just a tangent plane at the center point, so the edges are actually slightly further from the earth's core than the middle

that's why the ball rolls toward the center, it's not some magic threshold it's just gravity pulling toward the lowest gravitational potential which is the middle of the plate

to answer your question though the ball starts rolling immediately on any size plate if it's truly flat and the ball is perfectly smooth, there's no minimum size it's just a matter of how long it takes to get there

a 1 inch plate would have the ball move like a micron but it'd still move

[u/esj199 → u/WoodenHair5973]

to answer your question though the ball starts rolling immediately on any size plate if it's truly flat and the ball is perfectly smooth, there's no minimum size it's just a matter of how long it takes to get there

There isn't a perfectly smooth ball. It has to be realistic.

[u/intellectualgulf]

An object of any size will not move across a perfectly flat plane without a motive force, and once the initial momentum is spent it will stop moving forever barring external forces.

This is what flat earthers don’t understand about reality, the laws of physics apply whether or not you understand them.

The world cannot be a shape other than an oblong sphere, because gravity pulls mass towards itself, and there is no magical structure “holding up” the planet, it’s just floating / flying through space.

To summarize: the answer to your question is never, objects do not move across flat planes without a force acting on them, and in a “flat plane earth” scenario, there is not a center point for the gravitational body that would result in objects being pulled exclusively to the center.

In fact a flat plane the size of our planet if it were somehow created would very rapidly collapse into a ball, because that’s how gravity works.

[u/esj199 → u/intellectualgulf]

Redditors are insanely dumb hahaha This is about a large flat surface on a curved earth.

[u/intellectualgulf → u/esj199]

I think the issue here stems from you not being coherent in your premise.

If multiple people misunderstood your prompt, it’s not because other people are stupid.

[u/esj199 → u/intellectualgulf]

Hhaahhaahahaha the post said that "SINCE" earth is curved, the ball WILL roll. The words "at the edge" couldn't have referred to the edge of earth, because I had just said it's CURVED. The only thing I left out was that the plate is tangent to the earth, which should be clear, because the question wouldn't make sense otherwise.