Before giving a mathematical proof for the formula for the volume of a sphere, Archimedes used physical reasoning to discover the solution (imagining the balancing of bodies on a scale). From the seventeenth century, many of the most important advances in mathematics appeared motivated by the study of physics, and this continued in the following centuries (although in the nineteenth century mathematics started to become increasingly independent from physics). The creation and development of calculus were strongly linked to the needs of physics: There was a need for a new mathematical language to deal with the new dynamics that had arisen from the work of scholars such as Galileo Galilei and Isaac Newton. During this period there was little distinction between physics and mathematics; as an example, Newton regarded geometry as a branch of mechanics. As time progressed, the mathematics used in physics has become increasingly sophisticated, as in the case of superstring theory. Unconventional connections between the two fields are found all the time as in 1975 Wu–Yang dictionary, that related concepts of gauge theory with differential geometry.