Why is everything round?

Why is everything round? Let's get after it. Why is a manhole cover a circle? Well, for a couple reasons. One of them being it can't fall through the hole. Another one being it seals perfectly every time, no matter how you orient it. Also, structural wise, I'll get into more into that. A square can fall through the hole. Just like that. You have to make sure that you line it up perfectly every time. As well as with a triangle. Triangle falls through the hole. And you have to make sure that you line it up perfectly every time. When force is applied to the square, the stress concentrates in the corners. Here, here, here, and here. Same with the triangle. The stress is on the corners. Here, here, here. But with a circle, the stress is around the whole thing distributed evenly. Same thing with pipes, cylinders, and even large air tanks. Pipes are round because they handle pressure evenly, whether it's air, gas, or water. It handles it evenly and effectively. And there are no corners for stuff to get caught up on. Same thing with air tanks. Air tanks handle the pressure evenly. A circle can handle all this pressure better than something with the corners. That's why you'll see circles everywhere, whether it's manhole covers, pressure vessels and tanks like this one, or piping. Anyways, it's Sunday. I got stuff to do. I'll catch you guys later. Peace.