Social science is a major category of academic disciplines, concerned with society and the relationships among individuals within a society.
Continue reading... Classical and Quantum mechanics are the two main fields of mechanics in physics. Classical mechanics came a few hundred years before Quantum mechanics. Subsequently it is less accurate and less reliable then the more recent mechanic field of Quantum mechanics. Despite being outdated, Classical mechanics can still be used for many everyday problems with bigger and slower moving objects.
Without quantum mechanics, none of solid-state physics makes any sense. It's no surprise that the field only really took off in the 1930's. Using the concepts of quantum mechanics, we can now determine the properties of solid materials, much in the same way we now predict chemical reactions.