Figuring the Mass of the Earth

This morning's commute centered on how scientists were able to compute the mass of the Earth, without ever leaving the planet. One of Newton's laws was that every object exerts a force on every other object, proportionate to it's mass and distance from the other object. Although I'd never know, when I walk into my living room, my cat is drawn towards me and I'm drawn towards my cat by our own tiny gravitational force.

That's pretty cool in it's own right, however, scientist used this knowledge to survey a large mountain to determine it's volume. They were able to figure the gravitational force of the mountain by dropping a plumb line near it and noticing that the line was pulled toward the mountain. After careful measurement and more math than a human should have to endure, the scientists were able to figure the mass of the mountain, extrapolate that to the mass of the Earth, as well as other objects in our solar system.

Now, I'm certain I explained this far too simply and I will probably get flamed by someone, but that's not the point. The point is a non-scientist type person now has a better understanding on these things, even if it is a simple understanding.

Also, Newton was a complete nut case. He once took a large needle, used for sewing leather together, and stuck it into his ocular cavity. He inserted the needed between his eye and eye socket and swirled it around there, just to see what would happen. On another occasion, he stared at the sun until he could no longer stand it, just to see what would happen. And this is the same man who was annoyed at the limits of mathematics while he was a student, so he invented calculus!