Energy

History of energy consumption• 原 始 时 期 :food is the No. 1 energy• 狩 猎 时 期 :wood is the first consumable energy forliving because human learned how to use fire• 原 始 农 业 时 期 :human use animals in farmingactivities• 先 进 农 业 时 期 :human learned to use coal, producedmachines to obtain wind energy and hydropower• 工 业 时 期 :invention of steam engine; wood wasreplaced by coal and oil• 现 代 技 术 时 期 :development of gas energy ( 内 燃 机 )and use of electricity