When were alternative energy sources invented?
Impossible to say, a man who discovered that if he drifted with the current in his dugout instead of paddling could be said to have used alternative energy, also rolling a log downhill. Waterwheels powered lathes thousands of years ago. The Romans diverted whole rivers to “sluice-wash” mineral deposits. A sail on a boat could be called an alternative energy source, alternative to paddling. I suppose using animal power could as well.
That depends on the particular kind of energy. Wind power was invented during the 1600’s when the Dutch used the windmills for farms. Hydroelectricity started back in the 1930’s when the Hoover Dam and Erie Canal were built. Later, scientists discovered solar power when NASA started space exploration. Tidal energy came to fruition in 1966 when France built the world’s first tidal barrage.
