I’m teaching my son to think like a scientist. He is two years old. We frequently go for walks together through the woods and along the coastlines of British Columbia where I allow his curiosity to run free. His current research project is throwing rocks into the ocean (this is just the exploratory phase mind you, hypothesis testing won’t come until after he’s potty trained). He undertakes this task with great determination and seems confident that he’ll soon complete the project, perhaps after one more throw.

Pulling back his fragile arm, he gathers all of the potential energy he can muster and hurls the small stone with what I estimate can’t be more than half a Newton’s worth of force. Not a strong start for this young ape, considering I’ve come dangerously close to injury from a projectile thrown by a bonobo not much older than he is. But he watches wide-eyed as the rock pulls upwards against gravity and then resigns into a gentle arc.

“Parabola,” I tell him just as the rock reaches its midpoint and heads downwards. “Gravity wins.” This is an imperfect description to be sure. But as Richard Feynman liked to say, "Nobody knows why things fall. It's a deep mystery, and the smartest people in the world don't know the basic reason for it." I figure I'm on safe ground. My son has become used to our little word game and he usually points at me in expectation if I don’t say it. This is followed by a quiet 'plop' as the kinetic energy from the rock is transferred into sound and a few small capillary waves that radiate outwards on the water's surface.

“Splash!” I announce and clap my hands as he watches the tiny ripples undulate. He knows that the parabola is the arc, but the splash is the payoff and I overemphasize the impact of his meager projectile for effect. He quickly looks around for another rock.

For me, science writing and science education are closely related projects. The ultimate goal is to translate what are sometimes highly complicated phenomena into the language of common experience. I've been inspired in this direction by the work of the astronomer and science writer Carl Sagan who combined a brilliant, analytical mind with the rare ability to communicate complex ideas. As I've learned, having fun is an important part of the process; it's what carries us through the technical work that is often necessary for a full understanding. For my son, it's about creating an association between specific words and ideas while making the experience an enjoyable one so that learning takes place "accidentally" through the repetition of a game. For you, my readers, it's about storytelling; my goal is to manipulate you so that you're captured by a certain narrative or intrigued by a perplexing question. If I do my job correctly, you'll read to the end so you can find out what happens. The science will come along for the ride.

I have had a diverse background, but the common thread has always been the joy of discovery and a love for the written word. My scientific background may have been primatology, but my interests have always been expanding outwards to distant shores. During the past four years, whether writing about stressed out monkeys, the genetics of helpful grandmothers, birth control and female sexuality, Haitian environmental policy, Ardipithecus ramidus, the Darwinian controversy over coral reefs, male chauvinist chimps, colonial science in India, Stalin's ape-man superwarriors, the evolution of human sexuality, or nuclear winter, I have always done my best to provide an interdisciplinary perspective and a strong narrative to carry the reader through. This last year in particular while in "exile" I encountered new audiences with every piece of writing and had to learn how to craft a story for an unknown readership. With every new post I imagined them staring at me in expectation from the quiet dark. Likewise, in my current pursuit as a historian of science, good storytelling is of the essence in order to provide the context within which scientific discovery takes place.

But storytelling has always been an important part of the scientific process dating back to its modern origins in the 17th century. The scientific journal article is a relatively recent invention and when Galileo Galilei wrote his Discourses and Mathematical Demonstrations Relating to Two New Sciences in 1638, the book that put forward his theory of uniform acceleration and the parabolic motion of projectiles, it took the form of a dialogue between three characters. The main character, Salviati, is clearly the author’s alter ego who spends most of the book presenting the evidence and theories that Galileo had spent thirty years refining. His chief antagonist is Simplicio who, as the name suggests, is challenged by Salviati's ideas and must be led along by a chain of evidence until he is ultimately persuaded. It was Simplicio's mouthing of statements nearly identical to those of Pope Urban VIII in Galileo's previous book on the “Copernican hypothesis” that was largely responsible for his being hauled before the Inquisition six years earlier.

Galileo’s chief question concerning projectile motion was one that had troubled natural philosophers ever since Aristotle’s treatment of the subject in the 4th century BC. What causes a rock to continue moving once you throw it? The question is not as simple as it may sound. We know why a rock moves forward when we push it: the force we exert from our muscles overcomes its mass and the friction from the ground where it sits. But how can a force we exert continue to operate when we’re no longer touching the rock? We’re ultimately discussing action at a distance. For Aristotle, and the natural philosophers who followed him during the subsequent two thousand years, this was a deeply religious question that directly related to how God was thought to operate on Earth. Most followed Aristotle in arguing that it was the air around the thrown rock that continued to push it forward. Action at a distance was reserved for the “prime mover” alone.

But a well-aimed rock can knock God from his heaven and reveal the mysteries of the universe. So it was that in the 1320s a pair of international criminals on the lam were ultimately responsible for God’s downfall (insofar as his representatives on Earth could claim a divine hand in the physical world). William of Ockham and Franciscus of Marchia were Franciscan friars and highly regarded natural philosophers at the University of Paris, the most distinguished center of learning in Europe at the time. They were also vocal critics of the excesses of Pope John XXII and insisted on denouncing him as a heretic. For his part, the Pope ordered their arrest by the Inquisition and declared their entire Franciscan Order guilty of heresy.

Pope John was one of the earliest pontiffs of the Avignon Papacy, a period where the Church made great efforts to centralize their operations and wield power over the religious and the secular realm. To do this required large amounts of money. The sale of indulgences, religious pardons for souls trapped in purgatory, brought healthy returns, as did an increase in taxes. There was a thriving market in priestly appointments, in which noble families could buy distinguished positions in the Church for their children. It was in 1320 that Pope John XXII signed the order that inaugurated the witch trials across Europe, with any property seized being absorbed by the Holy Church. And, even as he was known for his taste in gold cloth and fur, the Pope’s Quia quorundam of 1324 stated that the Franciscan vow of poverty was “absurd and erroneous” since it entailed their living off of “the sustenance of nature.” Because these were items the friars did not own, such behavior was “unjust” and little better than that of thieves.

But while Ockham and Marchia were forced to abandon their work and flee to Bavaria (a region that would later become a hotbed of Protestant revolt), the influence they left behind in Paris achieved more than any papal decree ever could. Two important breaks with Aristotelian tradition launched an idea whose inertia would ultimately challenge the Church’s authority by rendering the deity they served completely powerless. First, Ockham rejected Aristotle’s contention that mathematics must be a separate category and should not be applied to other areas of knowledge (such as physics). Second, Marchia rejected Aristotle’s views on projectile motion and posited a theory remarkably similar to Galileo's three hundred years later.

Marchia's approach was purely theoretical but his argument was that a projectile retained a “leftover force” (virtus derelicta) that provided the impetus needed to resist its fall to Earth temporarily. This force was retained by the projectile and required no force from the surrounding air the way Aristotle conceived it. But Marchia was also a devout Christian and believed that this virtus derelicta could explain the transubstantiation of the sacraments during Communion (in which bread and wine transform into the literal body and blood of Christ). As a result, he was not willing to accept the idea that there was a uniform motion between the terrestrial and the celestial realms. God still reigned over the heavenly spheres, even if natural forces dictated motion on the ground.

The connection between these two realms would ultimately fall to a young graduate student, Nicole Oresme, who was present at the University of Paris during the controversy over his professors' charge of heresy. This young man would later become one of the most influential scholars of the 14th century, and one whose political safety was assured by personal support from King Charles V. The events of the 1320s clearly left their impression on the young man, for he employed and expanded the ideas of Ockham and Marchia where they broke from Aristotle to propose a truly revolutionary concept:

Pythagoras said that through day and night the Earth rotates around the poles of the circle of the equator . . . Others, refuting this opinion, say that if the Earth rotated, the things in the air and the birds and clouds would be left behind by the motion of the Earth. But Pythagoras maintains that not only does the Earth rotate, but so do the air and whatever things are in it. So, whether the Pythagoreans’ opinion is truer, or that of the others who posit that the Earth is immobile, no argument can detect.

He went on to reject the standard argument against this hypothesis, that an arrow shot straight upwards returns to its original place, because he said that the arrow would continue to move with the Earth since it already shared the planet's motion. It would be like dropping a coin on a moving ship, it would fall straight down relative to the ship but not to the sea. However, Oresme remained agnostic on the Earth's motion because he had no means to verify it.

But this connection between simple projectile motion and the movement of the planets would become the basis for Galileo’s empirical tests. By simply measuring the distance that an object traveled (in his case, a large brass ball) after it was rolled down an inclined plane at different angles he demonstrated the concept of uniform acceleration. This insight led directly to his discussion of uniform motion in which all matter, on Earth as it is in heaven, operated according to the laws of physics. The deity who had previously pushed the planets in their orbit around a fixed Earth would eventually be reduced to a spectator (or vanish entirely). Today, the physical laws that developed as a direct result of Galileo's experiments, standing as they did on the shoulders of Ockham, Marchia and Oresme, makes such a divine hypothesis completely unnecessary. “Because there is a law such as gravity, the Universe can and will create itself from nothing," Stephen Hawking wrote in his latest book. “It is not necessary to invoke God."

From the simple parabola as a rock is thrown outwards to the movement of the heavenly spheres: such is the impact that small ideas can have when combined with an inventive mind and careful empirical tests. Science is the creative examination of our ideas against the natural world. It is the best means yet devised to fact check our collective reality, and is the culmination of the human spirit.

It was Carl Sagan who best summed up the wonder and power of the scientific process in his book and PBS series Cosmos that was released when I was just a little older than my son is now.

We embarked on our journey to the stars with a question first framed in the childhood of our species and in each generation asked anew with undiminished wonder: What are the stars? Exploration is in our nature. We began as wanderers, and we are wanderers still. We have lingered long enough on the shores of the cosmic ocean. We are ready at last to set sail for the stars.

More recently I've taken my son to the public swimming pool in Vancouver where I've found him to be obsessed with jets of water that shoot upwards for children to play in. Their arc outlines five perfectly formed parabolas. I carry him in my arms to the midpoint just beneath one of the jets and point upwards. "This is where gravity wins," I tell him. I don't think he understands what I mean just yet, but there are still many rocks to be thrown into the cosmic ocean of his imagination and over time I expect the idea will take hold. There are many more concepts still to come and then the real fun begins, we embark on our voyage and test our ideas against the world around us.

In these pages that follow it is my goal, to the best of my ability, to process the examinations of creative discovery in science but also to examine the process itself. In so doing I will be throwing my own rocks into the ocean and will never quite be finished. I hope to one day show these pages to my son. Perhaps he'll be inspired the way I was when first invited on my journey into the cosmic ocean. And maybe he'll understand why we chose to name him Sagan.


Elazar, M. (2011). Projectile Motion and the Rejection of Superposition, Boston Studies in the Philosophy of Science, 288, 169-187.

Courtenay, W.J. (2000). The Early Career of Nicole Oresme, Isis 91 (3), 542-548.

Goddu, A. (2001). The Impact of Ockham's Reading of the "Physics" on the Mertonians and Parisian Terminists, Early Science and Medicine 6 (3), 204-237.

Leff, G. (1961). Heresy and the Decline of the Medieval Church, Past and Present 20 (1), 36-51.

Schabel, C. (2006). Francis of Marchia's Virtus derelicta and the Context of Its Development, Vivarium 44 (1), 41-80.

Toulmin, S.E. and Goodfield, J. (1999). The Fabric of the Heavens: The Development of Astronomy and Dynamics, University of Chicago Press, p. 220.

Zanin, F. (2006). Francis of Marchia, Virtus derelicta, and Modifications of the Basic Principles of Aristotelian Physics, Vivarium 44 (1), 81-95.