A golden age of physics appears to have been delineated for certain periods of progress in the physics sciences, and this includes the previous and current developments of cosmology and astronomy. Each "golden age" introduces significant advancements in theoretical and experimental methods. Discernible time periods marking a "golden age" of advancements are, for example, the development of mechanics under Galileo (1564–1642) and Isaac Newton (1642–1727). Another small epoch seen as a golden age is the unification of electricity, magnetism, and optics because of 19th century notables, including Michael Faraday, James Clerk Maxwell, and others.