C3 - The macrocosm: new heavens, new earth

The invention of the telescope represents the most dramatic rupture in the entire history of observational astronomy. Galileo did not invent the instrument, but after increasing its power and directing it from the earth to the heavens, he published in 1610 a brief work which provided for the first time startling empirical evidence which undermined the traditional geocentric cosmology and bolstered central features of heliocentric alternative. After a brief account of the origins of the telescope, this cluster outlines the chief features of the work and its startling revelations regarding the pockmarked surface of the moon, the innumerable stars invisible to the naked eye and, most significantly, the existence of four satellites orbiting around the planet Jupiter.
 

Galileo’s Sidereus nuncius of 1610 inaugurated a frantic and fertile period of telescopic observation, accelerated both by the significance of his discoveries and by constant technological innovation. Each of the main findings of his revolutionary little work became the starting point for further investigations.  His first sketches of the face of the moon give rise to selenographia, which rapidly produced increasingly detailed and precise representations of the Earth’s satellite. The presence of irregularities on the Moon’s surface stimulated a debate over the apparent spots discovered on the face of the Sun as well.  Telescopic observation spread from Jupiter to other planets, revealing the phases of Venus and the curious appearance of Saturn, which baffled astronomers for a generation. Galileo, eager to exploit the practical as well as theoretical implications of his discoveries, also devoted considerable energy to harnessing the potential of Jupiter’s satellite to provide the reliable clockwork needed to solve the vexed problem of determining longitude at sea.