"Castles may conjure up a romantic fairy tale world; however, in real life, during the Middle Ages, castles were fortresses, providing shelter and protection for the lord as well as for the peasants who lived on his land. For an army, a lord depended on young soldiers in armor called knights who spent years at the castle learning the skills of warfare"--

Did you know that the same wind that messes up your hair can be used to create energy? How exactly do you harness the wind? And what is the effect on the environment? Read this book to find out all about wind energy.

Did you know people can dig underground and use Earth's heat to make energy? This geothermal energy can power the computer and heat or cool your home. How exactly do we get it, though? And what is the impact on our environment? Read this book to find out all about geothermal energy.

Did you know that most of the energy we use comes from coal, oil, and natural gas? How do workers collect these fossil fuels? And what effects do these fuels have on the environment? Read this book to find out all about coal, oil, and natural gas.

Did you know that tiny atoms that make up all matter hold huge amounts of energy? This energy, called nuclear energy, can power the television and refrigerator in your home. How is nuclear energy produced, though? And what are the drawbacks of this energy source? Read this book to find out all about nuclear energy.