The Copernicus Complex: Our Cosmic Significance in a Universe of Planets and Probabilities - Softcover

Scharf, Caleb

Softcover

ISBN 10: 0374535574 ISBN 13: 9780374535575

Publisher: Scientific American / Farrar, Straus and Giroux, 2015

Synopsis

Longlisted for the 2015 PEN/E.O. Wilson Literary Science Writing Award
Short-listed for Physics World's Book of the Year
The Sunday Times (UK) Best Science Book of 2014
A Publishers Weekly Top 10 Science Book of Fall 2014
An NBC News Top Science and Tech Book of 2014
A Politics & Prose 2014 Staff Pick

In the sixteenth century, Nicolaus Copernicus dared to go against the establishment by proposing that Earth rotates around the Sun. Having demoted Earth from its unique position in the cosmos to one of mediocrity, Copernicus set in motion a revolution in scientific thought. This perspective has influenced our thinking for centuries. However, recent evidence challenges the Copernican Principle, hinting that we do in fact live in a special place, at a special time, as the product of a chain of unlikely events. But can we be significant if the Sun is still just one of a billion trillion stars in the observable universe? And what if our universe is just one of a multitude of others-a single slice of an infinity of parallel realities?

In The Copernicus Complex, the renowned astrophysicist Caleb Scharf takes us on a scientific adventure, from tiny microbes within the Earth to distant exoplanets, probability theory, and beyond, arguing that there is a solution to this contradiction, a third way of viewing our place in the cosmos, if we weigh the evidence properly. As Scharf explains, we do occupy an unusual time in a 14-billion-year-old universe, in a somewhat unusual type of solar system surrounded by an ocean of unimaginable planetary diversity: hot Jupiters with orbits of less than a day, planet-size rocks spinning around dead stars, and a wealth of alien super-Earths. Yet life here is built from the most common chemistry in the universe, and we are a snapshot taken from billions of years of biological evolution. Bringing us to the cutting edge of scientific discovery, Scharf shows how the answers to fundamental questions of existence will come from embracing the peculiarity of our circumstance without denying the Copernican vision.

With characteristic verve, Scharf uses the latest scientific findings to reconsider where we stand in the balance between cosmic significance and mediocrity, order and chaos. Presenting a compelling and bold view of our true status, The Copernicus Complex proposes a way forward in the ultimate quest: determining life's abundance, not just across this universe but across all realities.

About this title

About the Author:

Caleb Scharf is the director of the Columbia Astrobiology Center. He writes for The New Yorker, New Scientist, Science, Scientific American, and Nature, among other publications, and has served as a consultant for the Discovery Channel, the Science Channel, and The New York Times. Scharf has been a keynote speaker for the American Museum of Natural History and the Rubin Museum of Art, and is the author of Gravity's Engines. He lives in New York City with his wife and two daughters.

Excerpt. © Reprinted by permission. All rights reserved.:

1

THE COPERNICUS COMPLEX

 

At a rather pleasant spot in the Aegean Sea in the third century B.C., on the vine-rich island of Samos off the western coast of what is now Turkey, the Greek philosopher Aristarchus had just had a brilliant idea. He proposed that the Earth spun and moved around the Sun, placing this scorching solar orb at the center of the heavens. It was, to say the least, a bold notion—Aristarchus’s idea of “heliocentrism” was as outrageous in his time as Copernicus’s revival would be in the distant future.

Records of Aristarchus’s works are fragmentary, and most concern the clever geometrical analyses that he used to argue that the Sun is significantly larger than the Earth. But it’s clear that from that insight he arrived at the idea that the Sun was central to the known cosmos, and that the stars were extraordinarily distant. This was a huge conceptual leap to ask of people. It also required understanding a phenomenon called parallax.

Parallax is earthbound as well as celestial, and is an easy concept to grasp. Close an eye and hold one hand up, fingers spread and viewed on edge. If you move your head side to side you will see different fingers appear and disappear from behind each other as your vantage point, or your angle of view, changes. This is all that parallax is: the apparent change in where distant objects appear relative to each other, depending on a line of sight. The farther away those objects are, the smaller that apparent change—the smaller the perceived angular displacement between them.

Part of Aristarchus’s bold argument involved the fact that the stars in the night sky didn’t appear to have any parallax; they never moved among themselves. So if the Earth were not stationary at the center of all existence, he reasoned, the stars must be so distant, so enormously far away from us, that we couldn’t measure their parallax as the Earth moved its position.

Not long before Aristarchus made his ideas known, the great philosopher Aristotle had already dismissed the possibility that the stars were any more distant than planets by appealing to this same lack of parallax, among other things. Aristotle’s argument was founded in reason and common sense. It built on even earlier ideas that the Earth was central to existence. The way he put it was simple: if no parallax could be seen in the stars—they did not shift around relative to one another at all—they must be all affixed to some layer of the sky that surrounded us at the unmoving origin.

All of which sounds logical, except that Aristotle’s own preferred cosmology (elaborating on ideas from his mentor, Plato) consisted of approximately fifty-five thick, crystalline, transparent spheres concentrically nested about the stationary Earth and carrying the planets and stars about their business. In this geocentric universe we were at the focus of all natural motions, with the stars and planets simply following perpetual circular paths around us as the crystalline spheres slid and rotated.

You might well ask why it took fifty-five spherical crystalline layers for Aristotle to build his cosmology. Part of the reason is that he had to justify a system of cosmic mechanics, a transfer of forces whereby one shell would rub on another, pushing it around—a great scheme of motions and machinery to keep everything tracking through the sky. This structure was intended to deal with the other most critical issue facing would-be cosmologists of the time; unlike the stars, the planets do move around the skies in a complicated fashion.

These tricky motions were a major piece of the puzzle that Aristarchus, and later Copernicus, tried solving by displacing the Earth. The word “planet” is derived from the Greek phrase for “wandering star,” and our brightly reflective planets most certainly do wander. Not only do they appear to move relative to the stars, noticeably shifting in position as the nights go by; sometimes they reverse course, performing a celestial loop-the-loop over a few months before carrying on. Planets like Venus and Mercury are even more subversive; often they’re nowhere to be seen. And even the speed of planetary paths across the heavens seems to be slower and faster at different times, with the brightness of these miscreants changing as well.

So you might think that when Aristarchus proposed his heliocentric system there would have been a huge sigh of relief, because placing the Earth on its own circular path around the Sun quickly provided a solution for much of the curious backward motion of the planets—what would later be known as “retrograde” movements. In this configuration the simple reason for such odd behavior was that our own vantage point was shifting as the Earth itself moved in a circle. There would naturally be times when our motion relative to a planet was either forward or backward, and our distance from a planet would change—lowering or raising its apparent brightness.

It was a lovely, elegant, and fact-based idea—and many people hated it. If the Earth moved, there should be a noticeable parallax among the stars, which surely couldn’t be that far away. And apart from this lack of observable parallax, displacing the Earth from its vaunted central position was anathema; it was ludicrous to consider that the very hub of our existence was not at the core of everything, and so poor Aristarchus got it in the neck.

The other part of this antipathy toward heliocentricity likely came from distaste for ideas that hinted of pluralism. In opposition to the likes of Plato and Aristotle, who argued for a divine and unique creation of the Earth, Greek thinkers such as Democritus and Epicurus instead advocated a picture of reality rooted in the notion of indivisible pieces and empty void—atoms and space. These atoms weren’t atoms as we now know them, but a philosophical concept of units of matter—too small to be seen, solid and uniform within, varied in size, shape, and weight—that could be used to describe an infinite number of structures. The idea of atoms led these thinkers to consider that the Earth was unlikely to be unique. Far from it—there should be an infinite number of inhabited worlds located within an abstract form of space and time and what, in retrospect, amounted to parallel universes. Not surprisingly, the plurality of worlds did not sit well with anyone following the Platonic or Aristotelian schools of thought.

What happened instead was that a number of natural philosophers in the decades following Aristarchus came up with a geocentric “fix” to account for the annoyingly unconventional motion of the planets across the skies, and to keep Earth rooted as the unique center of existence. Their solution to the dilemma of celestial movements probably first originated almost a century after Aristarchus and Aristotle butted heads, with the astronomer and geometer Apollonius of Perga around the turn of the second century B.C.

Later on, this explanation was subsumed into the works of Claudius Ptolemy. Living some three hundred years after Aristarchus, the Greek-Roman citizen Ptolemy resided in Egypt under the rule of the Roman Empire. He was a prolific thinker, producing significant works on many topics, including astronomy, geography, astrology, and optics. And most important, he produced an astronomical treatise known as the Almagest that laid out a cosmological vision that would stick for the next 1,400 years.

In Ptolemy’s system, the Earth is firmly stationed at the center of the universe. Moving outward are the Moon, Mercury, Venus, then the Sun, and then Mars, Jupiter, Saturn, and the fixed tapestry of stars—all following circular paths. To translate this arrangement into the messy movements seen in our skies, he added a clever set of extra motions along special circular paths called deferents and epicycles. And these were, rather ironically, centered on a location offset from the Earth (a peculiarity that seems to have escaped the scrutiny of zealous geocentrists across the centuries).

In this ingenious arrangement, the planets and the Sun move around the smaller perfect circles of the epicycles, which in turn move along the larger circles of the deferents, which rotate around a point separated from the Earth. The end result matches up with the major features of the looping, back-and-forth pathways of the planets. To do this, Ptolemy’s system had to be very fine-tuned to actual observations of the planets. Each and every deferent and epicycle was meticulously sized and located in order to give the best fit possible to the real meanderings of the known worlds.

Even with such fine engineering, the system couldn’t quite get everything right—there were little deviations here and there from astronomers’ measurements over the years. Planets would arrive a bit early or late to certain positions on the sky—not enough, though, to discourage everyone. Here was a plausible model for the nature and motion of the Sun, Moon, and planets that was geocentric, grounded in the precision and truth of geometry, and in agreement with the thinking of the Great Philosophers. The model comforted mathematicians and theologians alike.

Later, as Ptolemy’s ideas were subsumed and integrated into the religious and philosophical doctrines of the Western world in the Middle Ages, they became intricately attached to a unified conceptual framework. Like arterial conduits helping to keep the blood flowing, the geocentric spheres and their epicycles were a key part of the machinery of the perceived universe. If you challenged geocentric cosmology you effectively challenged the whole body of scientific, philosophical, and religious thought—including its powerful institutions of rule and administration.

*   *   *

Despite geocentrism’s importance, in the fourteen centuries between Ptolemy and Copernicus there was in fact no single generally accepted picture of the detailed specifics of the arrangement of the universe. This disconnect is one of the most interesting aspects of the development of “cosmology”—or at the very least the development of a model of our solar system. During this entire time span, bits and pieces of ideas and worldviews were typically cobbled together for convenience, as and when needed—a cosmic mix-and-match. It depended on whether you wanted a mathematically driven universe, or a more abstract philosophical one. And all of these ideas in turn reached back to the varied hypotheses and proposals of a multitude of long-departed Greek thinkers.

Equally important for this cosmological history was that so much of its character hinged on the available precision of measurement. Aristotle and Aristarchus were no slouches when it came to making careful astronomical observations, but they were severely limited with only human eyes and basic tools for assessing angles and distances. This limitation meant that they actually had no idea what something like the true parallax motion of the stars really was; they just assumed it was zero.

The data on the motion of the planets themselves was also of limited precision, and it left gaps in knowledge that would let Aristotle and Ptolemy squeeze geocentric models, with their increasingly elaborate geometric arrangements, into the picture. The models may not have been perfect, but humanity’s observations of the heavens weren’t good enough to disprove them.

So by the late 1400s there had been little real progress in formulating a better model for the motions of the Earth, the planets, and the stars—especially given the accepted need to be consistent with the religious and philosophical doctrines of the Western world. In fact, I think it’s fair to say that to our modern scientific eyes, medieval cosmological models were in a thoroughly messy and inconsistent state. The time was certainly ripe for some drastic improvements to be made. All that was needed was the right person.

*   *   *

Nicolaus Copernicus was born on February 19, 1473. Growing up in a part of Prussia that had recently been ceded to Poland, Copernicus had the good fortune to be part of a sophisticated and well-off family. He got an excellent education that included a thorough grounding in philosophy (which by default was the intensive study of the works of the ancient Greeks), mathematics, and the natural sciences—including astronomy. He was also genuinely voracious in his appetite for knowledge, and doesn’t seem to have shied away from hard work during his entire lifetime, even producing manuscripts on poetry and politics in addition to his scientific investigations.

His early schooling led him on to further studies in Italy, where he began to get more and more interested in astronomical observations, especially those that related to the measurable deviations of lunar and planetary behavior from the Ptolemaic system. Other investigators of the time were also well aware of these deviations, but the industrious Copernicus was particularly moved to step outside the usual bounds in looking for answers, and was eager to find a more accurate solution than the one that Ptolemy had devised so long before.

In the early 1500s Copernicus drafted what would later become the basis for his full heliocentric model of the solar system—a forty-page work known as his Commentariolus, or “little commentary.” It was never officially published during his lifetime, but instead a few copies circulated in a limited fashion, garnering interest and respect from his contemporaries and no doubt some stern glares from the prevailing establishment. While it may have been little, the commentary contains seven critical and visionary axioms.

Paraphrasing these in more modern terms, this is what Copernicus had to say about the cosmos:

• There is no single center to the universe.

• The Earth’s center is not the center of the universe.

• The center of the universe is near the Sun.*

• The distance from the Earth to the Sun is imperceptible compared with the distance to the stars, and so no parallax is seen in the stars.

• The rotation of the Earth accounts for the apparent daily rotation across the sky of the Sun and of the stars, which are immovable.

• The annual variations of the Sun’s movements across the sky are actually caused by the Earth revolving around the Sun.

• The looping (retrograde) motion that we see for the planets is actually caused by the movement of the Earth.

After this last idea Copernicus was sufficiently excited to add in his brief commentary: “The motion of the earth alone, therefore, suffices to explain so many irregularities in the heavens.”

Here in these sentences was the genesis of a colossal revolution in human thought. Through the power of little more than deductive reasoning, Copernicus had set the cherished Earth spinning and traveling through the universe. But although the circulation of the Commentariolus helped him gain a considerable reputation, it wasn’t until decades later that he finally took these writings and more thoroughly worked out the mathematical pieces of his theory in order to have them published—effectively posthumously—in the great De revolutionibus orbium coelestium, “On the Revolutions of the Celestial Spheres,” in 1543.†

As much as this model shook the heavens into shape, it was also still very far from perfect. Despite, as we now know, correctly arranging the Earth, the Sun, planets, and stars in their respective places, Copernicus still assumed certain properties that made fitting his model to astronomical observations awkward. In fact, rather than doing away with all of ...

About this edition

• Publisher: Scientific American / Farrar, Straus and Giroux
• Publication date: 2015
• ISBN 10: 0374535574
• ISBN 13: 9780374535575
• Binding: Paperback
• Number of pages: 288