Why Does The Earth Spin?

So, I'm down in West Vancouver, British Columbia, which is where I grew up. At the local beach, there is this 2 and 1/2 ton granite sphere that was made to have a tolerance of 200s of a millimeter. This is an amazing granite sphere, and it’s floated on a thin layer of water. It just presents an amazing opportunity to study inertia.

That's why I'm down here, to have a chat with some of the people going by about why the globe spins. In fact, why does the Earth spin? Why does it turn like that? I think it's the gravity that keeps us down on the ground, is that right? Gravitational pull—how does that cause the Earth to spin? Again, my basic science fails; it fails gravity.

He, he, he guesses, you know, looking at gravity. Yeah, gravity. It's not stopping! Would you agree with me? Yeah. So why is that? Some sort of force? Do you think there's a force down there pushing it? Yeah, I'm going to go because the upthrust from the water is probably angled in such a way that it's because it's a spherical shape. It's probably pushing on it at an angle so it spins constantly.

Yes. What is the centrifugal force that keeps it going? What is that force? Where does that force come from? Is there a force that keeps it going? Is there a force pushing it around within the Earth's core? Is there not something that drives and dictates said centrifugal force?

Guess it's the law of inertia, isn't it? What's the law of inertia? Every action has an equal and opposite reaction. The force of inertia maintains this, but inertia, which is a great idea, is not a force. How would you define it? It's just the tendency of all objects with mass to maintain their state of motion.

Okay, so if they stay still, they want to stay stationary—if we anthropomorphize them, yes. And if they're moving, said anthropomorphized objects want to keep moving. Basically, whatever motion they have, they like to continue in that state of motion. The Earth does that without any forces. This does that without any forces. Yes.