A Big Event in scientific history must be one that fundamentally changes our world view.
I nominate Galileo's invention of the telescope.
True, people were making lenses in the Netherlands at that time, and the Heliocentric view of the heavens was an idea that was being considered by some philosophers, but when Galileo put 2 lenses together and aimed them at the sky he forever altered our perception of the earth's position in the cosmos.
His discovery and observations of the moons of Jupiter, the phases of Venus, and the mountainous surface of the Moon demonstrated the true structure of the solar system and opened the universe to astronomers. The scientific journey he began still continues.
Last edited by Claybird; 02/14/10 09:14 PM.