The Roman Philario and four guests welcome the Englishman Posthumus to Rome, where he has been exiled. There is only one named guest, an Italian named Giacomo, who with a Frenchman are the only guests with speaking parts, whereas unaccountably silent are a Dutchman and a Spaniard. This hitherto unexplained oddity may be understood by the lack of application of the Dutch telescope to astronomy by the Spanish and by the Dutch themselves, who were busy with war on Earth and had no time to explore the Heavens. By contrast, in Sidereus Nuncius, the Italian Galileo Galilei (who is pictured on the left and was born in a year 1564 that is familiar to Shakespearean scholars) gives thanks to the French nobleman Jacques Badovere for bringing the Dutch telescopic device to his attention. He trained it on celestial objects and reported results in his book, which many claim to be the world's first astronomical scientific publication. Thus in Cymbeline, the Italian Giacomo and the Frenchman are rewarded with speaking parts, whereas the Spaniard and the Dutchman are mute.
Doubt about this interpretation is lessened by the fact that Jacques Badovere's parents, who were Italians from Venice with the surname Badoer, christened their son Giacomo.
Giacomo stands in for Galileo, and Shakespeare details Galileo's findings via Giacomo's antics.
In 1609, Galileo Galilei learned of a telescope that had been made in Holland, and he immediately set about building one of his own. One night after midnight, he trained his spyglass on celestial objects and was astounded by what he saw: nebulosities in the Milky Way gave way to a multitude of faint stars so close together that they appeared nebulous to the naked eye; the Moon cratered; and planet Jupiter with four specks of light revolving about it, which Galileo correctly identified as moons. He made sketches of what he observed and of Jupiter's moons as they revolved and published the results in March, 1610 in a booklet known as The Starry Messenger. Shakespeare wrote Cymbeline before the end of that year.
In the play, Giacomo emerges from a trunk after midnight and observes Immogen's bedroom, its stars and Jupiter's moons, and in Shakespeare's day, another word for "telescope" was "trunk."
Giacomo happens to be the given name of the Frenchman who transmitted to Galileo news of the Dutch telescope invention. Giacomo wagers that he can compromise the virtue of Posthumus's beloved Immogen. He travels to England, but she spurns his advances and he resorts to deceit to access her bedchamber. He tells her that he has purchased jewels and has stored them in a trunk, which he persuades her to keep safe for him. He hides in the trunk, has it delivered, and soon after Immogen falls asleep at midnight, he emerges. Auditors presume that he intends to win his bet forcefully, but instead he makes sketches and takes notes on the contents of her bedroom. Of interest to him are "ten thousand meaner movables" that are "above," and in Hamlet, 10,000 represents the number of stars in the sky visible to the naked eye. i.e. Galileo estimated that there were 10,000 or more stars beyond the reach of the naked eye. Furthermore, Giacomo identifies four moons whose periods are less than the Earth's Moon, as are all four of Jupiter's moons.
Posthumus masquerades as a soldier in the Roman army that had invaded Britain, and the troops of the British King Cymbeline capture him. He is incarcerated awaiting trial when he falls asleep and dreams of the four ghosts of his deceased parents and two brothers who dance around in imitation of celestial orbits. They beseech the god Jupiter to intervene on his behalf, and with spectacular theatricality, Jupiter descends from the heavens seated on the back of an eagle, the Bird of Jove.
He brings with him a tablet that morphs linguistically into a book, and lays it on Posthumus's breast. In 2001 and again in The Shakespeare Newsletter in 2003, I suggested that the godly gift is Galileo's book Sidereus Nuncius (The Starry Messenger) in which he announced observations of the four ghostly satellites of Jupiter. Thus the deity Jupiter is a "starry messenger." The Diggeses were telescopists long before 1610, and we wonder on the next page whether the bard refers to the Jovian satellites in an earlier play.