520 aerospacetechnologyandastronautics astronautics astronomy astrophysics astrophysicsandastroparticles astrophysicsandcosmology classicalandquantumgravitation computerapplications computerscience dynamicalsystemsandergodictheory dynamics ergodictheory extraterrestrialphysics gravitation history historyandphilosophicalfoundationsofphysics historyofphysics historyofscience mathematicalmethodsinphysics mathematics mechanics observations observationsandtechniques physics planetology popularscience popularscienceinastronomy popularscienceinmathematics/computerscience/naturalscience/technology popularworks qb460-466 qb980-991 relativity(physics) relativityandcosmology relativitytheory science science(general) spacesciences