Editor's Note: Dan Falk is most recently the author of The Science of Shakespeare: A New Look at the Playwright's Universe, in which Falk travels back to the Scientific Revolution to examine the kind of impact astronomers, philosophers and writers had on Shakespeare's works. Dan discusses five of the era's greatest thinkers -- from Digges to de Montaigne -- and explains how they molded the literary mind of William Shakespeare. From name-dropping atoms, to understanding the infinite scope of space, to questioning God, below are just some of the enlightened findings on Shakespeare's forgotten muses.

1. Lucretius

The Roman philosopher and poet Lucretius (99-55 B.C.) liked to think small. In atoms, that is. Some four centuries earlier, a Greek thinker named Leucippus, and his pupil, Democritus, imagined that the world was made up of tiny chunks of matter that could not be divided into anything smaller. (These chunks are known as "atoms" from the Greek "atomos," meaning indivisible.) Lucretius ran with the idea, creating an epic poem, On The Nature of Things, which touted the virtues of the atomic theory. Confirmation of this bold idea would come only in the 19th century, long after Shakespeare’s time; and yet, this ancient Greek idea was experiencing a bit of a revival in Elizabethan England.

As Stephen Greenblatt of Harvard has noted, the book went through some thirty Latin editions between 1473 and 1600 (and Ben Jonson’s copy can be seen to this day in Harvard’s Houghton Library). Did Shakespeare know about atoms? Yes -- at least, he referred to them poetically on several occasions. In Romeo and Juliet, for example, Mercutio suggests that his friend has been visited by Queen Mab, a fairy-like creature that enters her victims’ brains via their noses, interfering with their dreams. How small is Queen Mab? She comes "in shape no bigger than an agate stone," Mercutio says, sitting in a coach "Drawn with a team of little atomi / Over men’s noses as they lie asleep."

2. Thomas Digges

Copernicus had published his groundbreaking book, On the Revolutions of the Heavenly Spheres, in 1543 -- twenty-one years before Shakespeare’s birth; in it, he places the earth among the planets, and positions the sun at the center of the cosmos. The first English account of this heliocentric (sun-centered) theory came two decades later, with the work of a statesman-scientist named Thomas Digges (c.1546-1595). In 1576, Digges published an updated version of an almanac written by his father. The almanac included a vision of the cosmos even more radical than that of Copernicus: He included a diagram of the cosmos in which the stars are seen to extend outward without limit -- a remarkable vision of a possibly infinite cosmos. Did Shakespeare catch wind of this idea? Perhaps. A handful of scholars have pointed to a possible clue in a remarkable passage in Hamlet, in which the prince envisions himself as "a king of infinite space." Could he be alluding to the new, infinite universe described -- for the first time -- by his countryman Thomas Digges?

3. Tycho Brahe

In November of 1572, a bright new star lit up the night sky, appearing in the constellation of Cassiopeia. (We now recognize such an event as a supernova, the explosive death of a massive star.) Shakespeare was only eight at the time -- but we know that Thomas Digges made detailed observations of the object, as did astronomer Tycho Brahe (1546-1601), observing from Denmark; today we call it "Tycho’s star." Astronomer Donald Olson, of Texas State University, has argued that the star observed by Prince Hamlet shining "westward from the pole" was inspired by Shakespeare’s boyhood memory of Tycho’s star -- reinforced, perhaps, by a reference to it in Holinshed’s Chronicles, published fifteen years later. (At the very least, Shakespeare would have seen the next supernova – "Kepler’s star," which appeared in 1604.) One might also note that Tycho observed the stars from the Danish island of Hven, barely a stone’s throw from the castle of Elsinore, chosen by Shakespeare as the setting for Hamlet. Finally, we might take a close look at Tycho’s extended family: An engraving from the 1590s shows Tycho surrounded by the family crests of a dozen or so relatives; among these names we find a "Rosencrans" and a "Guildensteren."

4. Michel de Montaigne

The French writer Montaigne (1533-1592) was profoundly skeptical: He questioned the authority of religious and political leaders. He questioned the wisdom of the ancient philosophers. He questioned mankind’s privileged status in the cosmic hierarchy. He even questioned the power of reason to make sense of the world. His sprawling Essays -- in which he shares his thoughts on life, the universe, and just about everything else -- were published over a 22-year period, beginning in the 1570s. Scholars have long remarked on the similarities between numerous passages from Shakespeare’s plays and de Montaigne’s Essays. One striking example can be found in The Tempest, where Shakespeare borrows (with only minor tweaks) Montaigne’s description of the natives of Brazil, and their seemingly-idyllic life. But there is more to be found in Montaigne: He mentions atomism, and even Copernicus. More generally, the questioning attitude that threads its way through the Essays may inform some of Shakespeare’s later works, such as the almost nihilistic King Lear.

5. Christopher Marlowe

Until his untimely murder in a bar in Deptford, outside London, Christopher Marlowe (1564-1593) was probably Shakespeare’s toughest competitor. He was also an Elizabethan man of mystery, acting as a government spy while at the same time hounded by accusations of homosexuality and atheism (both of which were criminal offences at the time). The word "atheism" hadn't yet taken on its modern, Richard-Dawkins-like meaning: There had been millennia of debate on the extent of the involvement of God (or the gods) in human affairs -- but the idea of the complete non-existence of God was probably not fully conceived in 16th-century England. In the case of Shakespeare, no one fired any accusations his way -- and so we turn, cautiously, to the published works.

Consider Titus Andronicus, in which we find the only self-avowed non-believer in the canon, the Moorish villain Aaron. When Aaron is taken prisoner, he tries to bargain with his captor, Lucius. But Lucius asks: What good is a vow from a non-believer? Aaron, however, has a snappy comeback: Those who do believe, he says, are often fools and liars, yet we imagine their oaths to be worth something. (Note how quick-witted Shakespeare’s villains are!)

What led Shakespeare in this direction? One possibility is that he was following Marlowe’s lead -- or perhaps trying to one-up his colleague. Consider the plot of Marlowe’s Doctor Faustus: The doctor makes a pact with the devil, and God doesn’t seem to care -- a theme echoed in many of Shakespeare’s plays, especially the later tragedies such as King Lear. In the latter play, as Stephen Greenblatt has noted, the gods "are conspicuously, devastatingly silent." In their absence, justice cannot be guaranteed; indeed, it becomes fragile in the extreme. Lear, in desperation, hopes that events will "show the heavens more just," but it is a lost cause. In one of the play’s most famous -- and darkest -- lines, Gloucester laments: "As flies to wanton boys are we to th’gods / They kill us for their sport." We might also examine Prince Hamlet’s obsessive contemplation of death and decay, with no mention of an afterlife; Helena’s assertion in All’s Well that Ends Well that "Our remedies oft in ourselves do lie / Which we ascribe to heaven"; or Macbeth’s assertion that life is "a tale, told by an idiot, signifying nothing." None of this proves that Shakespeare was an atheist -- but it suggests that he could at least imagine a godless world.