Early energy sources were simple; fire was discovered to heat things, and then along came conversion – such as fire under a kettle producing steam. But times have changed, and the impact of using non-renewable sources of energy, or fossil fuels, is one that we can no longer afford to ignore.
早期能源其实很简单，火是用于加热的，不过随后其用途发生了变化，如在水壶下生火产生蒸汽。然而，时代不同了，人类无法忽视使用不可再生能源或化石燃料造成的影响
