National Weather Center.
What is it like to explore the heavens?
With his telescope, Galileo discovered mountains on the Moon, four satellites of Jupiter, the phases of Venus, dark spots tracking across the face of the Sun, the enigmatic “ears” of Saturn, and countless stars that were invisible to the unaided eye. These discoveries created a new era for investigations of the Sun, planets, space and stars.
Galileo inaugurated the era of telescopic solar observation. Galileo’s detailed, full-page copperplate engravings set a new standard for presenting evidence about the Sun. With Galileo, detailed visual representations became essential to space science. Galileo’s study of sunspots is a masterpiece of data visualization. The spots move together. They move slowly, each taking about a month to travel across the solar disk. Their shape is irregular; they form and disappear with irregular timing. The spots foreshorten as they approach the edge of the solar disk. All this proves they lie on or very near the surface, and are not little planets. Sunspots therefore suggest that the Sun and the heavens are corruptible, a tenet contrary to Aristotle but already accepted by some scientists and theologians.
1. Galileo, Istoria e Dimostrazioni Intorno alle Macchie Solari (Rome, 1613), “Letters on Sunspots”
2. Christoph Scheiner, Rosa Ursina (Bracciani, 1630), “The Rose of Orsini”
In the late 20th century, spaceships and planetary probes began to reach the Moon and other bodies of the solar system. Voyagers from Earth include the Galileo mission to Jupiter and the Cassini spacecraft to Saturn, which carried the Huygens planetary probe. These missions bear the names of early space scientists. Galileo, Cassini and Huygens, architects of planetary science, provided the first sketches of the Moon, Mars, Jupiter and Saturn. Others investigated the Earth in relation to the cosmos, discerned additional planetary satellites, and discovered unexpected solar system objects unknown to the ancients.
3. Christiaan Huygens, Systema Saturnium (The Hague, 1659), “The System of Saturn”
4. Christiaan Huygens, The Celestial Worlds Discover’d, or, Conjectures concerning the Inhabitants, Plants and Productions of the Worlds in the Planets (London, 1698)
5. Giovanni Domenico Cassini, Martis circa axem proprium (Bologna, 1666); De aliis Romanis observationibus macularum Martis (Bologna, 1666); De Periodo quotidianae revolutionis Martis (Bologna, 1666), “Observations in Bologna of the rotation of Mars around its axis”
6. Edmond Halley, “Astronomiae cometicae synopsis,” Philosophical Transactions of the Royal Society of London (London, 1705)
7. Louis Agassiz, Études sur les Glaciers (Neuchatel, 1840), “Studies on Glaciers”
8. Joseph Alphonse Adhémar, Revolutions de la Mer (Paris, 1842), “Revolutions of the Sea”
Newton integrated Galileo’s terrestrial physics and Kepler’s laws of the heavens into a universal theory of gravitation, prompting new reflections on the nature of the universe itself.
The example of “nebulae” illustrates these changes. The word “nebulae” meant “clouds” to Latin meteorologists, yet it came to refer to misty clouds in the heavens revealed by telescopes but not easily resolved. Some of these nebulae came to be understood as vast clouds of interstellar gas, sites of the birth and death of stars. Others came to be known as galaxies in deep space, constantly receding in every direction from our own Milky Way.
Developments like these might seem to vindicate Copernicus who exclaimed, “So vast, without any question, is the divine handiwork of the most excellent Almighty,” in one of the sentences of De revolutionibus censored by the Inquisition in 1616.
9. Isaac Newton, Philosophiae naturalis principia mathematica (London, 1713), 2d ed.
10. Isaac Newton, Mathematical Principles of Natural Philosophy (London, 1729)
11. Isaac Newton, A Treatise of the System of the World (London, 1728)
12. Thomas Wright, An Original Theory or New Hypothesis of the Universe (London, 1750)
13. Charles Messier, “Catalogue des Nébuleuses et des Amas d’Étoiles,” Memoires Academie Royale des Sciences pour 1771 (Paris, 1774), pp. 435ff., “Catalogue of Nebulae and Star Clusters”
14. Caroline Herschel, Memoir and Correspondence (London, 1876)
15. Otto Boeddicker, The Milky Way… drawn at the Earl of Rosse’s Observatory at Birr Castle (London, 1892)
16. Edwin Hubble, The Realm of the Nebulae (New Haven, 1936)
Galileo discovered more than 100 unsuspected stars when he turned his telescope toward Orion the Hunter and Taurus the Bull. Ever since, the number of known stars has continued to increase. Ptolemy described 48 constellations in the Almagest; currently there are 88 officially-recognized constellations.
Galileo inscribed the OU copy of the Starry Messenger to a poet. The human experience of the night sky has always combined scientific and imaginative aspects. Albert Einstein recognized the creativity at the heart of major scientific leaps when he wrote, “imagination is more important than knowledge.” Art, music, literature and astronomy merge in a creative and ongoing exploration of the stars and constellations.
17. Hesiod, Opera (Frankfurt, 1559), “Works of Hesiod”
18. Aratus, Phenomena (Basel, 1547), “Appearances of the Skies”
19. Hyginus, Poeticon astronomicon (Venice, 1485), “Astronomical Poem”
20. Abu Ma’shar, Introductorium in astronomiam (Augsburg, 1489), “Introduction to Astronomy”
21. Prose de’ Signori Accademici Gelati (Bologna, 1671), “Essays by the Members of the Academy of Gelati”
22. Vincenzo Coronelli, Epitome Cosmografica (Cologne, 1693), “Representing the Heavens”
23. Edmond Halley, Catalogus stellarum australium (London, 1679), “Catalogue of Southern Stars”
24. Nicolas Lacaille, “Planisphere contenant les Constellations Celestes,” Memoires Academie Royale des Sciences pour 1752 (Paris, 1756)
25. John Flamsteed, Atlas Celeste (Paris, 1776), ed. J. Fortin, “Celestial Atlas”
26. J. E. Bode, Vorstellung der Gestirne (Berlin, 1782), “Atlas of the Stars”
27. Alfred, Lord Tennyson, Poems (London, 1843), 2 vols.; vol 1 and vol 2.
28. Lord Byron, Works (London, 1815-1824), 11 vols., ”Works”
29. Percy Bysshe Shelley, Poetical Works (London, 1876-1877), 4 vols.
30. Robert Frost, “The Star-Splitter,” New Hampshire (New York, 1923)
31. Urania’s Mirror (London 1825), a boxed set of 32 cards; with Jehoshaphat Aspin, A Familiar Treatise on Astronomy (London 1825), 2d ed.
- Dava Sobel, Galileo’s Daughter: A Historical Memoir of Science, Faith, and Love (Walker, 1999)
- Stillman Drake, Galileo: A Very Short Introduction (Oxford, 2001; originally printed 1983 in the Past Masters series), discussion guide.
- John Heilbron, Galileo (Oxford, 2010)
- William B. Ashworth, Jr., Out of This World: The Golden Age of the Celestial Atlas, An Exhibition of Rare Books from the Collection of the Linda Hall Library, with supplement Further Out (printed catalogs; online exhibit)
- Chet Raymo, 365 Starry Nights (Simon & Schuster, 1990)