Things fall. The direction in which they fall is called ‘down’. A small mass suspended on a string is called a ‘plumb line’. It points down. Things generally fall down.

Things fall down as a result of Gravity. Gravity is the closest thing Science can offer as a proven ‘fact’. It always works. It is considered to be a undisputed law of Nature.

Small children know Gravity. A child cries when a balloon gets away. Not for the loss of the balloon but because it fell ‘up’. Nothing falls up and this is cause for great distress. His paradigm is broken. His world view is shattered. Crying is justified.

Some people will tell you things fall toward the Earth. Some are more specific in saying that they fall toward the center of the Earth. They are both technically wrong.

Everyday things fall toward the Center of Gravity of the Earth. In practice, there maybe an imperceptible difference between the C.G. of the Earth and the actual center of the Earth, but the distinction is important. The C.G. of an object falls toward the C.G. of the Earth.

The weight of every object always acts through its center of gravity. In other words, the C.G. is the balance point of the object. An object with a heavy end will have a C.G. closer to that heavy end than the middle of the object. Here is it more evident that we must insist on the distinction between the center of an object and its C.G.

You may find the C.G. of an object by suspending it by a string from any point. Hang a plumb line from the same point and and mark the path of the line on the object. Repeat the procedure from another point. The C.G. is the point where the two lines intersect. It is the average position of the mass of the object.

The C.G. is the point that falls down and takes the rest of the object with it.