We’ve all looked up into the night sky and pondered the vast expanse beyond, been humbled in the presence of the ocean or mountains or the stars, and wondered about our place in this universe. Carl Sagan’s classic book Cosmos looks at some of history’s seminal scientists who have changed the way we see our world. Their discoveries have fueled exploration, at first intercontinental, now interplanetary, and, perhaps, someday, interstellar. Sagan’s book stands as an enthusiastic acknowledgement of the most curious and adventuresome species on the planet, and a warning about their growing carelessness.

Humankind has long marveled at the immensity and majesty of the world and the expanse beyond its horizons. To contemplate the Cosmos is to dwell on one of life’s oldest, most compelling mysteries.

Evolution has wired us to explore, to brave the unknown, to discover and learn. And so we have. We now know, for example, that light travels at a speed of 186,000 miles per second—that’s seven times around the earth in just one second! We now know that it takes eight minutes for light from the sun to reach earth, making the sun eight light minutes away. In all the Cosmos, there are about ten billion trillion stars, and probably as many planets. We know the chances of a star being at just the right distance from a water-filled planet to foster and sustain life are infinitesimally small.

These are facts that we take for granted in our modern world, but there were far more knowledge gaps in the ancient world. Despite these gaps and a dearth of technology, some ancient speculations are shockingly accurate. Our planet’s relatively small size was discovered about 2,200 years ago in Alexandria, Egypt, by the director of the Library of Alexandria, Eratosthenes.

In a papyrus document that Eratosthenes found in the library’s archives, he read that if you placed a stick exactly upright on June 21, it would cast no shadow at high noon. Eratosthenes found that in Alexandria, 800 kilometers from Syene, a vertical stick would cast a considerable shadow on that same day and time. Why the discrepancy? Eratosthenes hypothesized that the earth’s surface must be curved. What is more, the dramatic difference between the absent shadow in Syene and the long shadow in Alexandria would make the curve significant. By observing how the shadows fell at various times of the day and year in Alexandria and Syene, he concluded that if you traced the sticks from their locations to the center of the earth, they would form a seven-degree angle. This was about a fiftieth of the world’s 360-degree circumference. So Eratosthenes multiplied the 800-kilometer distance between the towns by fifty to arrive at the figure of 40,000 kilometers. This matches modern estimates of the earth’s circumference within just a few percentage points.

Eratosthones’ scientific discovery gave the intrepid courage to venture beyond the Mediterranean shores. The voyages became more and more ambitious. Over a millennia later, the tradition continued. It can be argued that Eratosthones began the exploration of new worlds by showing earth’s finite dimensions. A query had begun that would culminate in the exploration of not just other continents but other planets. As the blank edges of the map have been filled in, the human drive to explore has pushed us to look beyond planet earth.

Of all that has emerged since the Big Bang fifteen to twenty billion years ago, human beings are currently the most remarkable emergence—a species that, heretofore, is the most intelligent, capable and driven to understand its place in the Cosmos, to understand the universe itself and even to shape it.

We live in a universe that toes a line between stagnancy and chaos. The world is not so rigid that it’s free from anomalies and change, nor so random that common patterns can’t be discerned. Objects will always gravitate toward earth’s center when dropped. The sun rises and sets in the east and west, respectively.

This is the kind of world in which science is possible, and what we learn through scientific inquiry gives us tools for humanity’s betterment. There’s clearly a harmony between the sun, moon, stars and planets. People have had this intuition for millennia, and do their best to make sense of it. Throughout our history, humans have barked up the wrong tree, pursuing astrological signs instead of scientific explanations.

Astrology refers to the practice of looking at the positions of stars, moons, and planets to gain predictive power. While this might strike the modern sensibilities as superstition from the hinterlands, the modern developed world is hardly free from the influence of astrology. For example, we still find a daily horoscope in major U.S. newspapers, which many consult religiously. Even in countries where the latest scientific findings are readily available, this trend is common. For every astronomer doing good science, there are ten astrologers perpetuating nonsense.

The legacy of astrology is even embedded in everyday language. The etymology of many familiar words and phrases relate to astrology. The word “disaster,” for example, comes from the Greek word for “bad star.”

We are grasping for a meaningful connection with the universe. We deeply desire to feel that what happens to us on earth reverberates out into the cosmos and vice-versa.

As it turns out, we are connected, not via superstitions, but by concrete cause-and-effect occurrences in space and time, involving matter and energy. We are here not because of mystical forces but because of evolutionary ones. 

As a young man, Kepler was a seminarian, but he realized that he found greater joy in exploring Creation than the Creator himself. A top-tier theorist, he relied on Tycho Brahe’s observations of planetary movement—the most detailed and accurate in Kepler’s day—received only when Tycho was on his deathbed.

After years of toiling and begging for research grants and the latest observational data on planetary movement, Kepler discovered that the lack of perfect harmony in the calculations of the orbits was because Copernicus and others had assumed that planets moved on a circular course. When he tested the figures using an ovular model, the numbers aligned better, but not perfectly. Then, in an experience that Kepler described as truth disguised and sneaking in the backdoor, he was surprised and elated to find that the observations aligned perfectly with the elliptic model. This meant that there was a harmonious pattern to the planets after all. From this monumental discovery came the formulation of precise laws of planetary motion as well as theories about a force akin to magnetism that would explain why the planets moved at different speeds at different points on the ellipse.

Isaac Newton picked up on Kepler’s hunch several decades later, mapping out formulated mathematical laws behind the force called gravity.

Newton built on Kepler’s mathematical work and theories to give an even fuller account of the music of the spheres. He used the same observations Tycho Brahe documented and Kepler used to generate more general mathematical principles, giving a framework for planetary systems.

Newton proved his genius on another occasion when Swiss scholar Johan Bernoulli posed a challenge to his fellow mathematicians known as the Brachistochrone Problem. Leading minds of that era, including Leibniz, asked for a-year-and-a-half in place of the six-month deadline originally proposed. Within twenty-four hours of receiving the challenge, Newton had derived a solution and, in the process, developed an entirely new branch of mathematical study known as calculus of variations. He published the paper anonymously, but Bernoulli immediately recognized it to be Newton’s work. “We recognize a lion by his claw,” Bernoulli is said to have remarked.

It is possible that no greater scientific mind has ever graced this pale blue dot than Newton.

Kepler and Newton gave posterity invaluable mathematical tools with which to work and refine. Their work marked an important turning point in scientific inquiry. It showed that there were mathematically expressible patterns to Nature that applied both to earth and the planets beyond.  

If you were to pick up a fistful of sand, you would find about 10,000 grains in your hand. In a clear night sky away from the city, you’d see about as many stars. What is amazing is that this glittering expanse is the tiniest proportion of what is out there. In this universe of ours there are far more stars than there are grains of sand in the world’s beaches and deserts.

The stars have been a source of wonder throughout history.  We’ve been trying to decipher images in the sky. The images that we see have been pretty consistent from any point on the earth because the stars are equidistant to anywhere we would choose to look up into the night sky. So the Southern Cross will look like the Southern Cross in Sydney or Sao Paolo, and the Big Dipper will look like a dipper in Boston or Bucharest. We see the constellations in 2-D, and we would need an entirely different vantage point before we could see it in 3-D.

Stars are far from static entities, however. They have shifted into the positions we have come to recognize and they will eventually shift away from them. Even 500,000 years ago, the Big Dipper didn’t look like a dipper at all. The zodiac symbols that many people have come to trust implicitly will be obsolete in a million years when the Leo constellation no longer looks like a lion at all, and drifts far from the sun’s trajectory.

Many stars shift. All are born, and then eventually go out in a massive blaze of glory.

Our hunger for exploration takes us beyond the solar system and its planets  to the exploration of stars and systems beyond. The Voyager ships are currently hurtling through space, but at the rate they’re going, it would take forty millennia to reach the star closest to the Sun.

Until we design interstellar crafts that can move faster than a ten-thousandth the speed of light, it’s a long shot. Various societies have proposed designs that would, in theory, enable a craft to travel at a tenth of the speed of light. At that speed, it would arrive at Alpha Centauri (the star system nearest to our solar system, only 4.3 light years away) in about forty years. It’s unlikely that this would be attained before the middle of the twenty-first century. A machine approaching the speed of light would not be possible for millennia.

For tens of millions of years, whales have engaged in a beautiful song that can carry across the oceans and be heard on the other side of the world. The baleen whale, for example, produces a song at 20 Hertz that another baleen whale can hear over 10,000 kilometers away.

Since the 1800s, however, one species has developed technologies sophisticated enough to disrupt these love songs. We humans are that species. With the invention of the steam engine came ships that create substantial noise pollution. Such vessels and even noisier progeny disrupt these subtle, sub-aquatic utterances. What is more, people are harvesting the organs of whales for makeup and other commodities. Their murderous obliteration of the whales over the last several centuries is inhumane and disruptive of primordial mammalian rhythms.  

Some hope for a day when we make contact with extraterrestrial life. But how are we doing with terrestrial life? Animals are going extinct and differing religious and political ideologies are tearing our own species to pieces.

Like the baleen whale that sends its love song out into the oceans beyond in hope of establishing contact, so we humans have put some signs of our existence out into space. On the Voyager, there are phonographs and info about genetic sequences, our planet and civilizations in the hopes that extraterrestrials could pick up and learn about us. It’s worth a try. Writing has only been around for several thousand years, but genetic sequences that we hold in common with our common ancestor have been around for billions of years; so DNA is perhaps the most apt expression of who we are.

If we happen to find other intelligent life, let us hope that they will look upon us with greater kindness than we have for one another. Many of us seem bent on beliefs that will bring about the destruction of this small blue planet we call home.