Related by context. Frequent words. (Click for all words.) 55 astronomer Carl Sagan 52 Carl Sagan 51 Richard Feynman 51 Clyde Tombaugh 51 planet Uranus 50 Halley comet 50 physicist Albert Einstein 50 Charles Babbage 50 Gregor Mendel 49 Professor Stephen Hawking 49 Phaethon 49 Astrophysicist 49 Gautama Buddha 49 Nicolaus Copernicus 49 Edwin Hubble 49 Feynman 49 Nibiru 49 Voyager spacecraft 48 astronomer 48 Lao Tzu 48 Epicurus 48 Thomas Malthus 48 Vikram Sarabhai 48 classical antiquity 48 HG Wells 47 astronomical observations 47 interplanetary spacecraft 47 Galileo Galilei 47 Owen Garriott 47 Linnaeus 47 stargazer 47 Pasachoff 47 Lunine 47 Venusian 47 WASP #b 47 double helix structure 47 Horkheimer 47 Percy Bysshe Shelley 46 Neil deGrasse Tyson 46 Cassini imaging 46 philologist 46 Ferdinand Magellan 46 quantum physicist 46 Lowell Observatory 46 celestial 46 Romantic poet 46 Francis Crick 46 Einstein theories 46 Johannes Kepler 46 Heraclitus 46 Earthlike 46 Siddhartha Gautama 45 Mandelbrot 45 ancients 45 Brahe 45 psychic phenomena 45 alien civilizations 45 Galileo spacecraft 45 Prof Hawking 45 Thor Heyerdahl 45 NASA Cassini 45 astrobiologists 45 STScI 45 Amerigo Vespucci 45 Astronomer 45 Cassini Huygens 45 HMS Beagle 45 Charles Darwin 45 outer planets 45 Saturn rings 44 Saturn moons 44 Paul Dirac 44 Oort Cloud 44 Theodore Herzl 44 Samuel FB 44 Strachey 44 Buckminster Fuller 44 Frank Borman 44 Schrödinger 44 James Lovelock 44 Petrarch 44 Einstein 44 Blaise Pascal 44 Saturn moon 44 celestial bodies 44 ESA Mars 44 Greek philosophers 44 Kuiper belt 44 cosmologist 44 discoverer 44 Consolmagno 44 God Particle 44 Haumea 44 Halley Comet 44 Claude Levi Strauss 44 mathematician 44 diviner 44 Friedrich Engels 44 cosmologists 44 A. Heinlein 43 Vespucci