Another concise, clear, but not sufficiently mathematical science tale told by Asimov. High points covered are: Copernican view of solar system, discovery of Uranus by Herschel, use of mathematics to discover the likely location of Neptune, eventual discovery of Neptune, the moons, orbits, and rings of the gas giants, and the Voyager II probe. Cool characters are: Galileo (the moons of Jupiter), Christian Huygens (a moon of Saturn), Giovanni Domenico Cassini (planetary orbits), William Herschel (Georgium Sidus), John Couch Adams and John Joseph Leverrier (prediction of Neptune's orbit), Johann Gottfried Galle and Heinrich Ludwig d'Arrest (discovery of Neptune),

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2023: It is striking how half the moons of the outer planets were unknown until Voyager 2 passed the various planets in the 80s and was somehow able to observe these smaller moons. This basically doubled the number of these moons known to astronomers. ( )