The modern theoretical study of mechanics has a long history dating from the early part of the 17th century. The first major contribution to particle dynamics was made by Galileo with his elementary theory of the motion of a projectile. The fundamental importance of Galileo's approach lay in his attempt to relate theory and experimental evidence; at the time this was a new concept of scientific method. Prior to this breakthrough scientific theories of mechanics were put forward wholly on this basis of reason and the authoritative statement.