The pulley.

I think that the pulley is the best invention of the history, the pulley and the wheel are esential to do every building, and without buildings we're not humans.

The first mention of the pulley was in 100 a.C. , when Plutarch (46/50 a.C.- 120 a.C.) ( in Parallel lives wrote that one day Archimedes (287 b.C.-212 b.C.) said to the king Hieron of Syracuse that he can move the Earth without effort, and he moves a ship of the king's army with pulleys, and obviously, without effort.

The pulley is composed of a wheel on a shaft with a groove, and a rope runs over the wheel and inside the groove. Pulleys are used to change the direction of a force, and also to reduce the effort done to move a weight, when in a pulley sistem you put a pulley, the effort is the result of divide the weigth by the number of pulleys, for example, if you put 1 pulley, you will do the same effort as the weight, but in other direction, but if you put 2 pulley, the effort will be 1/2 of the weight, and you can put any number of pulleys. With arround 1000 pulleys, you can carry a car with one hand!

But I think that the pulley wasn't invented by Archimedes, the Egypcians maybe used it 3000 years before to do the pyramids, carry 5t stone blocks isn't very easy.

For this and other things I think that the pulley is the vest invention of the humans.