53	PHYSICS
53.1	General and theoretical physics
53.11	Theory of relativity
53.12	Nuclear physics. Atomic physics. Molecular physics
53.13	Quantum theory. Quantum mechanics
53.3	Mechanics
53.4	Acoustics. Mechanical vibrations
53.5	Thermology
53.6	Optics. Radiology
53.66	Chromatics
53.7	Electricity. Magnetism
53.8	Physics as a hobby and pastime