Thinking - Flat Earth gravity

I had someone cancel an appointment today so found myself browsing youtube with no particular direction and found something interesting.

A while ago I talked about what I thought gravity might be like with a flat thing on a spherical Earth, but today I discovered on Vsauce what it might be like to live on a flat earth.

As long as it was thick enough to have some gravity, as you approach the edge, the amount of Earth behind you would add a stack of gravity. The closer you get to the edge, the more it would be pulling you back to the centre. So a bit like the billiard table I described, a ball dropped anywhere on the surface would roll back into the centre. The closer you get to the edge, the more gravity you would feel, and the more it would be attracting you toward the centre of the disk. So it would feel like you were walking uphill, AND there would be more gravity.

But my new favourite bit is what would happen when you actually managed to climb up to the edge of this flat Earth.

Nothing special.

You could just keep walking to the other side. You would step over the rim and just keep strolling along the thickness of it. The gravity would be strong, but at least you wouldn't be walking uphill any more. Once you got to the edge of the other side, you could step over it onto a downwards slope and walk to the centre.

In fact other than the centres of each side, the thickness bit (the bit that looks like the surface of a tire that touches the road) would be the best place to live and ride bikes because it would be so nice and flat.

I feel slightly safer.


120 Things in 20 years would dig a hole through at the centre so everyone could enjoy zero gravity.

Thinking - Gravity

Space is a funny thing.

I keep thinking I don't have enough of it on my desk, but that doesn't really tell the entire story.

The world really is an unlikely place.

Take this for example....

If you put something really, really flat, and I mean flat, not earth flat... so say an imaginary flat billiard table...put an imaginary flat billiard table on earth. A really really big imaginary flat billiard table.

Now throw a ball on it.

It will roll around and around like something going down a drain until it settles in the middle.

At the lowest point.

The lowest point of a flat thing.

See. That's just silly.

But that's what would happen. When seen in 2D like my expert drawing, a flat thing would actually make a valley on earth. The sides of the flat thing would be the top of mountains.

If we strike out at 90 degrees from my 2D drawing, and consider it in 3D, it would form a crater with the centre being the lowest point.

So when you throw a ball into the picture, a ball... a ball on earth, would experience a perfectly smooth crater with the centre forming the lowest point, and the edges of the billiard table forming the rim. I was going to say "a perfectly smooth rectangular crater", but I'm not sure it would still be a rectangle.

I'm not sure of anything any more.

Similarly silly is what would happen if you drilled a perfectly straight hole through the earth's crust.

If you drilled an imaginary perfectly straight hole through the Earth's crust and threw a ball into it, it would eventually settle out somewhere around point C.

At the lowest point.

An imaginary straight tunnel, is really (whatever "really" means) an arc shaped tunnel.

Or at least it is as far as a ball is concerned.

Or a person.

If you entered the tunnel at point A, you would be entering a tunnel cut into the earth at say 35 degrees.

A steep decent.

But point C is the lowest point, so after passing point C, you would be climbing again. I think that means that points B and D would be a gentle slope compared with points A and E.

Personally I think this example makes a lot more sense than the previous one, but that might be simply because I'm getting the hang of it, or it could be because I used some letters of the alphabet.

There's nothing like the familiar to sooth the nerves.

But turn your back on the universe for even a second, and space gets all curved and confusing.




120 Things in 20 years - Thinking gravity? Think perfectly flat billiard valleys.