Starting with first principles and familiar situations, this book on energy looks at what we know and feel comfortable with before expanding to the further reaches of scientific enquiry. It reveals how our scientific understanding of matter and how energy can change is based on the theories of the Ancient Greek thinkers. It was in the 17th Century that scientists performed experiments that gave a better understanding of the energy changes that take place when an object moves. The book goes on to show how experiments carried out towards the end of the 18th-century encouraged scientists to question the idea that heat is a sort of liquid. it was the new electrical inventions of the 19th century which helped scientists investigate whether electricity, light and magnetism are related forms of energy. The coming of steam power and the industrial revolution led many 19th-century scientists to look for ways to make the new machines even more effective. It was only during the early part of this century that scientists developed a new theory to connect the different forms of energy in the universe. The book leads to a close with the the role of Albert Einstein and the quantum theory of energy which has led to further important discoveries that may help to satisfy the world"s growing energy needs.