Human beings have been using energy from fire for thousands of years. There is evidence that late age stone cave dwellers kept their caves warm with fires which were kept alight for months or even years. These early people relied on fire, even though they did not know where it came from. In fact, they thought it was magic.
Heat energy from fire is used for making things, like glass cups. Glass is helpful for making a variety of items including mirrors, lenses for glasses, and telescopes. As long ago as 4,000 B.C., people would heat mixtures of sand to high temperatures to form glass using large furnaces, heated by fire.
Evidence from caves in China shows that people used fire for cooking as early as 500,000 years ago, just as they do today. Fire makes food healthier by killing the bacteria in food. Furthermore, heat also helps to combine ingredients to make new food substances, or achieve desired flavors.
Beyond cooking, energy from fire has been used to heat houses for many thousands of years. Ancient Greece was the first to use central heating, but the Romans improved it with a sophisticated heating process called hypocaust, which heated homes and baths by forcing hot air under the floors.
Fire can be dangerous, but it is very useful. It keeps us warm; it disinfects; and it creates ambience when used to light a candle or make s’mores around a campfire. As one of the key natural elements with earth and wind, fire helps connect us to nature.
[Source: Eyewitness Science Energy]