I'm all for reusable sources or energy because, one day, the world will run out of oil and without preparation for that day there will most likely be an energy crisis. It's one of the biggest tasks I think my generation should be taking on. One example is a reusable energy is wind. Wind is cause by the uneven heating of the Earth. Wind power has been harnessed to do work before. Windmills used to be used to grind grain down into a flour. So, how does a windmill or wind turbine work? Well, the wind will be moving at a certain velocity and hit the surface area of one of the blades on the turbine. Energy can be measured in power multiplied by time. So the amount of energy created depends on how much power is created over a certain amount of time. The amount of power created depends on the area the wind hits and at what velocity. Then, due to conservation of energy, whatever energy created by wind can be transferred into another usable form.