Physics is the study of the many forms of matter and energy and the way they interact with themselves and each other. A number of ancient races made observations about certain aspects of physics, such as planetary motion, but were unable to develop theories as to the reasons for these motions. Some of the earliest applications of physics were by the Greek mathematician Archimedes, who applied physics to create such devices as levers and screws. It was not until the 17th century that experimental methods and scientific measuring devices led to a true understanding of many fundamental physical laws. Early scientists such as Johannes Kepler and Sir Isaac Newton began to disprove the theories of the ancient Greek philosophers and scientifically prove their theories concerning the laws of physics. Discoveries in physics rarely have direct applications, however they do provide a basic understanding of the laws governing the universe, thus forming the basis for practical advances in technology.