Abstract
Galileo completed his first series of lunar observations – those recorded in the ink wash drawings – on December 18. By then he had also worked out the correct explanation of the phenomenon of earthshine – the dull-red glowing of the dark side of the young Moon.1 He saw at once that earthshine was an illumination of the night-side of the Moon by sunlight reflected from the Earth. “The earth,” he wrote, “in fair and grateful exchange, pays back to the moon an illumination similar to that which it receives from her throughout nearly all the darkest gloom of night.” Having previously shown that the Moon – with its mountains and valleys – was another Earth, he could now demonstrate that the Earth was another planet, reflecting the sunlight from its continents and oceans onto the surface of the Moon.
This is a preview of subscription content, log in via an institution.
Notes
- 1.
He was not, however, the first to do so. Leonardo had anticipated him, though his notes on the subject remained unknown. Kepler’s teacher, Michael Mästlin, had discussed the same idea in a work on eclipses (1596), while Kepler had also made this identification in his treatise on optics (1604).
- 2.
Galileo, The Starry Messenger, p. 49.
- 3.
Montgomery, The Moon and the Western Imagination, pp. 116–117.
- 4.
Quoted in I. Bernard Cohen, The Birth of the New Physics, pp. 75–76.
- 5.
Galileo, The Starry Messenger, p. 25.
- 6.
Bredekamp, “Blazing Hands and Blind Spots,” p. 156.
- 7.
Ibid., p. 170.
- 8.
Opere xi, 170–172. Translated by Drake, Discoveries and Opinions, pp. 66–68.
- 9.
The passage is from Paradise Lost, V, 287–291:
… the moon, whose orb
Through optic glass the Tuscan artist views
At evening from the top of Fiesole,
Or in Valdarno to descry new lands,
Rivers or mountains in her spotty globe.
There is no record of Galileo’s having observed the Moon from the lofty heights of the ancient city of Fiesole, which is located north of Florence. Florence itself is, of course, situated in Valdarno – the Valley of the River of the Arno – but Galileo’s discoveries about the Moon were made in Padua, not Florence.
- 10.
Sobel, Galileo’s Daughter, pp. 38–39.
- 11.
Santillana, The Crime of Galileo, pp. 7–8.
- 12.
Quoted in Terrie F. Bloom, “Borrowed Perceptions: Harriot’s Maps of the Moon.” Journal for the History of Astronomy 9 (1978):117–122:121.
- 13.
The superiority of Galileo’s instruments is attested to by the case of Peiresc, who used a telescope by Jacob Metius, who had been one of the original claimants to invention of the telescope. Peiresc admitted to Galileo in 1634 that though Metius’ instrument allowed him to just glimpse the four satellites of Jupiter, it was not powerful enough to allow him to carry out the study he had hoped to make with it, the precise determination of the satellites’ orbital periods. He asked whether Galileo would be able to produce and send him a good telescope.
- 14.
Santillana, The Crime of Galileo, p. 124.
- 15.
Jacob Bronowski, The Ascent of Man (Boston: Little, Brown & Co., 1973), p. 205.
- 16.
Camille Flammarion, La Planète Mars. Paris: Gauthier-Villars, 1892, vol. 1, p. 5.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
Copyright information
© 2010 Springer Science+Business Media, LLC
About this chapter
Cite this chapter
Sheehan, W. (2010). Figures of Cynthia. In: A Passion for the Planets. Springer, New York, NY. https://doi.org/10.1007/978-1-4419-5971-3_9
Download citation
DOI: https://doi.org/10.1007/978-1-4419-5971-3_9
Published:
Publisher Name: Springer, New York, NY
Print ISBN: 978-1-4419-5970-6
Online ISBN: 978-1-4419-5971-3
eBook Packages: Physics and AstronomyPhysics and Astronomy (R0)