Related by context. Frequent words. (Click for all words.) 76 general relativity 66 quantum theory 62 quantum mechanics 60 relativity 57 cosmology 57 gravitational waves 56 cosmological 56 Big Bang theory 55 cosmologists 54 distant galaxies 54 astrophysicists 54 theorem 54 quantum physics 54 galaxy clusters 53 gravitational 53 quantum mechanical 53 cosmic microwave background 53 particle physics 53 quasar 53 neutron star 52 Higgs boson 52 physicists 52 Saturn rings 52 Einstein 51 quasars 51 cosmic 51 cosmos 50 dynamical 50 physics 50 astronomers 50 theory 50 magnetic fields 50 galaxies 50 computer simulations 50 redshift 49 theoretical physicist 49 neutron stars 49 cosmic rays 49 extrasolar planets 49 comet 49 subatomic particles 49 supernovas 49 supernovae 48 celestial bodies 48 photons 48 Milky Way 48 physicist 48 planets 48 brown dwarfs 48 astrophysics 48 supernova 48 spectroscopic 48 antimatter 48 spectrograph 48 neutrino 48 supermassive black holes 48 NASA Chandra 48 particle accelerators 47 gamma ray bursts 47 pulsar 47 neutrinos 47 atomic particles 47 relativistic 47 hypothesis 46 Solar System 46 particle 46 graphene 46 subatomic 46 experimentally 46 metamaterial 46 exoplanets 46 mathematician 46 equations 46 LCROSS 46 gravitation 46 quark 46 thermodynamics 45 photon 45 Albert Einstein 45 gamma rays 45 quarks 45 ionosphere 45 exoplanet 45 Darwin theory 45 galaxy 45 Physicist 45 rocky planets 45 superconductivity 45 supermassive black hole 45 mathematical calculations 45 atoms 45 spectroscopy 45 Hubble telescope 45 telescope 45 astrophysicist 45 theoretical physics 45 vortices 44 astronomer 44 universe 44 comets 44 pulsars