Related by context. Frequent words. (Click for all words.) 52 Galileo Galilei 48 astronomical observatory 47 observatory 46 sundials 45 telescope 44 astronomy 44 classical antiquity 44 Hubble Telescope 43 interplanetary spacecraft 43 Nicolaus Copernicus 43 lunar landing 43 Edwin Hubble 43 Antikythera Mechanism 42 orbiting telescope 42 Galileo 42 Hubble telescope 42 Exploratorium 42 astronomical observations 41 moon 41 sundial 40 Hubble 40 planetarium 40 Einstein 40 Richard Feynman 40 Cassini Huygens 40 telescopes 40 COROT 40 Gliese #g 40 Higgs particle 40 Observatory 40 Astronomy 39 TIFR 39 Hayden Planetarium 39 Pope Leo XIII 39 cosmology 39 celestial bodies 39 Halley comet 39 Copernicus 39 astronomers 39 orbiting Saturn 39 Palomar Observatory 39 Einstein theory 39 Voyager spacecraft 39 geodesy 38 solstices 38 Wernher von Braun 38 Vatican Observatory 38 Galaxy Evolution 38 Southern Observatory ESO 38 outer planets 38 celestial 38 NASA Mars rover 38 Gravity Probe B 38 Space Telescope 38 Clyde Tombaugh 38 celestial object 38 Adler Planetarium 38 Thirty Meter Telescope 38 International Astronomical 38 camera obscura 38 Observatories 38 Big Bang theory 37 Albert Einstein 37 Mars rover 37 STScI 37 robotic spacecraft 37 relativity 37 particle physicists 37 Astrophysicists 37 Planetary Science 37 Pan STARRS 37 NASAs 37 astrophysical 37 planet orbiting 37 moon landings 37 JWST 37 Horkheimer 37 cosmologists 37 Astronomer Royal 37 Hubble Space Telescope 37 extrasolar planet 37 Niels Bohr 37 moon Charon 36 infrared telescope 36 photometry 36 astronomer 36 Jodrell Bank 36 observatories 36 Von Braun 36 spacecrafts 36 Apollo lunar 36 cosmological 36 cosmos 36 observing 36 Outer Space Treaty 36 planetary 36 Neil deGrasse Tyson 36 distant galaxy 36 Solar System 36 optical telescope 36 scientific