The Antikythera Mechanism:

Be very careful in your assumptions about the extent of our knowledge in this century compared to what has been known in the past. Society’s knowledge of gears, gear ratios, and mechanical devices goes back considerably longer in time than a few hundred years. The Greek scientists had built a bronze mechanical device similar to a clock in that it had gears using complicated ratios, sizes and combinations of gears. This device was built around 80 BC and was discovered in a shipwreck near Greece in 1900. For a long time the scientific community of the time refused to admit that the Greeks could have built anything like this mechanism, yet recently it has been shown to be authentic and has significantly altered established ideas of what the ancient people were capable of. The existence of this device, which was used to compute the seasons and positions of stars and possibly the passage of time in lunar units shows us that the art of brass and bronze gear making goes back thousands of years. . . but don’t take my word for it; here are some links to information about this fantastic discovery:

http://antwrp.gsfc.nasa.gov/apod/ap061205.html 

http://commons.wikimedia.org/wiki/Image:NAMA_Machine_d%27Anticyth%C3%A8re_1.jpg 

http://en.wikipedia.org/wiki/Antikythera_Mechanism 

http://www.nature.com/nature/journal/v444/n7119/abs/nature05357.html

http://ccat.sas.upenn.edu/rrice/apagadgt.html