A look at two of the wilder innovations that never really quite caught on were underwater motorcycles and mechanical supermarkets. She explains all the special attention that the handlers must provide to keep these marine mammals healthy in an artificial environment including monitoring water chemistry and diet. Of all the technological innovations to date, one of the most significant was human control of fire. Not only did fire give humans the ability to see at night and cook their food, but it offered artificial warmth which in turn meant that humans could move from tropical environments and literally conquer the world. Scientists argue about how long the use of fire has been in existence, but there is clear evidence that people have been using this energy source for over 500,000 years.
Fire is defined as the rapid burning of material resulting in the net gain of heat.
Many oxidation reactions occur everyday without releasing fire, however. The rusting of iron, the energy released from food in the cells of our bodies and even the bleaching of stained clothes all involve oxidation reactions. In order for fire to be produced you need heat and fuel vapors in addition to oxygen. If you ever watched a candle burning or eaten cherries jubilee, you may have noticed that the actual flame of the fire is burning in the air above the material. This is because the object once heated is producing volatile vapors which then ignite.