Gravity & Round Earth

An understanding of the Earth is flat apparently returned to trust some people. The understanding that the Earth is flat to grow again just like the ancient belief that rebirth. Humans already have the image of the Earth as a blue marble, photographing Earth from Saturn as the "Pale Blue Dot", and sent New Horizon to the edge of the Solar System. How could anyone still believe the Earth flat? Believe it or not, in fact there are people like that.

But of course, the Earth is not flat. The Earth is round. If the Earth is not a ball shaped, but was instead a flat disc with the weight ; density ; and thickness living in the middle of it could feel pretty normal. But as we move toward the edge, gravity on a disk Earth would slightly skew, pushing at a greater and greater angle back toward the center. Anything as massive as the Earth, shaped like a flat disc under it's own gravity would naturally collapse back into a ball shape. This is why in outer space everything more than a few hundred miles in diameter is round.

The Verrazano - Narrow Bridge, connecting Staten Island and Brooklyn, had to be designed with Earth's roundness in mind. It's 2 towers, separated by 1300 meters and perfectly vertical, are nonetheless 41 millimeters further apart at the top than at the bottom because of Earth's curvature.

In the 3rd century BC, Eratosthenes measured the differences between shadows cast by poles in Syene and Alexandria to calculate (more than 2000 years before rockets and space travel) the circumference of the entire globular Earth, with, for the time, impressive accuracy. And word got around that the Earth was a round shape after that.

Eratosthenes method

Flat Earth theories are predominantly ad hoc explanations, excuses made up on the spot that only address one issue and don't fit all the evidence. Science, of course rejects a theory if a better one fits more of our observations, but why the egoistical obsession with our observations?

A cosmic ray particle could use the very same scientific method we use and conclude that in fact the Earth was flat. At speeds near the speeds of light, time slows down and lengths contract. One way we know this is that unstable muons, created in the upper atmosphere by the collision of cosmic rays with the atmosphere, should mostly decay before reaching Earth's surface. But yet, we detect a lot of them down here in Earth, because they're crazy fast speed literally means that, from our perspective, their physics runs according to a slower clock; and to them, the distance they have to cover to the surface during their short lives is much much shorter than it appears to us.

If you're a cosmic ray proton, travelling at 99.9999999999991% the speed of light, Earth would appear to be only 17 meters thick in the direction you travel. So Earth is flat to them, but round to us.

But, WHAT IF GRAVITY ISN'T REAL?

The Earth is spinning and we all are spinning along with it. But what if the Earth suddenly stopped spinning? The spin of our planet is important and literally giving you the time of your life. At the Equator, the surface of Earth and everything on it, is spinning around at 465 meters per second. As move closer to the poles you don't have to move as quickly to complete Earth's daily rotation. We are all spinning with the Earth and that's why slamming on a set of magical planetary breaks that caused everything classically called Earth to stop spinning would be catastrophic.

Immediately everything that wasn't Earth, and wasn't safely at the poles, would continue moving, as it had been, and be flung due east at more than thousand miles an hour. You wouldn't be flung into space because escape velocity is 24.800 mph, but you body would instantly become like a 9.5 inch bullet. And because the atmosphere would more gradually slow down, people in airplanes assuming they could navigate the resulting storms, might have better chance of surviving. People really really near the poles might be okay, but only on first. Gusts of wind, as fast as those near an atomic bomb detonation, would blast pass the surface and up into the sky forming worldwide storms of unprecedented magnitude.

If the Earth is spinning so quickly, why can't we feel it? Why doesn't the Earth's rotation make us dizzy? Well, lucky for us, the change in velocity is just too gradual. The Earth is too huge. But that change in velocity is real and makes us way less, because of inertia. On our spinning planet your velocity is constantly changing but always tangential to the circular path you were being dragged along. Now, because inertia is a property of matter, which includes your body, without a force acting upon us we would slowly leave the surface of Earth. Luckily, the Earth is exerting a force on us.

A center-seeking, centripetal foce, delivered by GRAVITY. The centripetal force required to keep you along a circular path with Earth is subtracted from Earth's total gravitational pull on you. The remaining force simply pushes you down, toward the center of the Earth and it gives you weight. At the Equator, if the Earth didn't spin, and no centripetal force was required to keep you with the Earth, you would weight 0.3% more than you currently do. If Earth spun you around 17 times faster than currently does, all of its gravitational force would go toward centripetal force fighting against your inertia and you would be weightless. [Vsauce]