Mapping The Heavens: How Cosmology Shaped Our View Of The Universe

The Milky Way
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Mapping The Heavens: How Cosmology Shaped Our View Of The Universe, And The Strange Story Of How The Term "Black Hole" Was Born

“When they gazed at the sky — infinite, remote and existing quite apart from their puny lives — people had a religious experience,” historian Karen Armstrong wrote in examining our earliest myths. “The sky towered above them, inconceivably immense, inaccessible and eternal. It was the very essence of transcendence and otherness.” Our sensemaking instinct pounced on that transcendent otherness and we spent 4,000 years mapping the skies. But where mythology seeks to contain that overwhelming immensity in a set of illusory certitudes, science uses every new piece of knowledge as a key to a door into an even vaster unknown. Trailblazing astronomer Maria Mitchell captured this beautifully in her diary: “We reach forth and strain every nerve, but we seize only a bit of the curtain that hides the infinite from us.”

It was only the last century or so, much thanks to Einstein’s seminal theory of relativity, that we have devised systematic ways of incrementally lifting the curtain. In Mapping the Heavens: The Radical Scientific Ideas That Reveal the Cosmos (public library), Yale theoretical astrophysicistPriyamvada Natarajan explores how the advent of modern cosmology and astrophysics has shaped our understanding of the universe and our place in it. Natarajan uses the inquiries at the center of her research — illuminating how black holes form and mapping dark matter— as a lens through which to chronicle some of the most significant and disorienting discoveries in science. Radiating from the history of these paradigm-shifting breakthroughs is a larger meditation on how groundbreaking ideas are dreamt up, tested against reality, contested by the quintessential human resistance to the fraying of the status quo, and finally woven into the fabric of our accepted understanding.

The Nebra Sky Disc (2000–1600 B.C.), excavated illegally in Germany in 1999, is considered the oldest known visualization of celestial objects. Part of the Bronze Age Únêtice culture, it depicts the sun or the full moon, a lunar crescent, and stars in a hammered copper-and-gold plate.

Natarajan writes:

The journey to acceptance of an idea reveals many other facets of science — the emotional, psychological, personal, and social dimensions that extend beyond the purely intellectual pursuit of knowledge.

[…]

The scientific mind is honed during training to be nimble, and the practice of science tests this agility on a daily basis. This inoculates scientists against disorienting shocks when a preponderance of new data and evidence changes the best current understanding.

As such, science stands as a rare case for the uncomfortable luxury of changing one’s mind amid a culture whose chief social currency is the artificial certitude of fixed opinions. The past century in particular — a mere blink on the cosmological scale of time — is a supreme testament to this accelerating revision of accepted truth. Natarajan writes:

In 1914, our own galaxy, the Milky Way, constituted the entire universe — alone, stagnant, and small. Cosmological research still relied fundamentally on classical conceptions of gravity developed in the seventeenth century. Modern physics and the triumphs of general relativity have shifted humanity’s entire comprehension of space and time. Now we see the universe as a dynamic place, expanding at an accelerating rate, whose principal mysterious constituents, dark matter and dark energy, are unseen. The remainder, all the elements in the periodic table, the matter that constitutes stars and us, contributes a mere 4 percent of the total inventory of the universe.

Art by Bhajju Shyam from Creation, an illustrated cosmogony of ancient Indian myths

Astrophysics, Natarajan notes, enlists the tools of science and reason in investigating the same questions that our ancestors tried to answer through mythology:

Cosmology, perhaps more essentially than any other scientific discipline, has transformed not only our conception of the universe but also our place in it. This need to locate ourselves and explain natural phenomena seems primordial. Ancient creation myths shared striking similarities across cultures and helped humans deal with the uncertainty of violent natural phenomena. These supernatural explanations evoke a belief in an invisible and yet more powerful reality, and besides, they rely deeply on channeling our sense of wonder at the natural world. The complex human imagination enabled ancient civilizations to envision entities that were not immediately present but still felt real. Take for instance Enki, the Sumerian god of water whose wrath unleashed floods, or the Hindu god of rain and thunderstorms, Indra, whose bow was the rainbow stretched across the sky with a lightning bolt as his arrow. The most powerful myths are the ones that force us to take huge leaps of imagination but, at the same time, help us to remain rooted.

Where science differs from mythology is that its findings are rooted into culture through rigorous testing against observable reality rather than through mere assertion. Natarajan writes:

The beauty of science is that while a theory is always provisional, it represents the best evidence and explanation that we have at any moment. Though prone to revision, science is based on replicable evidence, which privileges scientific over all other possible explanations.

[…]

Although science as a human endeavor is not entirely objective, it still offers the best prescription for weighing evidence and making sense of the natural world. Shifting and incomplete as it may be, science is self-correcting. It is the best method we have to navigate and make sense of this wondrous universe of ours. For centuries, science has helped us chart our relationship to the natural world. And like any good map, it also points the way forward.

But although the path to answers is decidedly different, there is a profound parallel in the underlying objects of curiosity. Natarajan considers her own formative bewitchment with the mystery of the cosmos and the invisible thread by which it links her childhood in India, stargazing and trying to map the cosmos by programming a now-antique Commodore 64, to her adult life as an astrophysicist doing cutting-edge research at some of the world’s most renowned academic institutions:

At its heart, my research as a theoretical astrophysicist, mapping dark matter and understanding the formation of black holes, is driven by the same sense of wonder and search for explanation of the universe that the ancients probably felt. I am still engaged in exploring the meanings of maps and how they anchor us, matters that first intrigued me as a girl in Delhi. My work exploits the bending of light from distant galaxies, gravitational lensing, to map the invisible dark matter that causes these deflections. I also investigate the formation and growth of the universe’s most bizarre and enigmatic objects, black holes.

An artist’s rendering of a black hole named Cygnus X-1, which formed when a large star caved in and began pulling matter from blue star beside it. (Image: NASA/CXC/M.Weiss)

In fact, one of the most fascinating portions of the book explores the history of how the term “black hole” — a term now at the forefront of a new era of gravitational astronomy— came to be, from its dawn as a metaphor for abomination and oblivion to its current use in science. Natarajan maps the winding road of the lexicon:

It was not the peculiar properties of an astronomical object that first inspired the term “black hole” but rather a place — an infamous prison. This was the scene of a gruesome incident on June 20, 1756. Sirajud-Daulah, the nawab, or ruler, of Bengal at that time, captured Calcutta from the East India Company’s troops, commanded by John Holwell, the self-proclaimed governor of Bengal. Upon surrender, the nawab confined Holwell and many other Europeans overnight in the company’s own prison cell, a tiny, dark room, roughly six meters (twenty feet) long and four meters (thirteen feet) wide, with two tiny windows, popularly known as “the Black Hole.” Records of the incident from East India Company officials claim that 146 people were locked up in this minuscule cell, without adequate water and in extreme heat, and that only twenty-three survived. Although scholars such as J. H. Little have called these numbers into question, the Black Hole of Calcutta remains a powerful, macabre reminder of and sordid metaphor for the utter callousness of the nawab. Soon “Black Hole of Calcutta” entered the collective consciousness as a synonym for the most horrific of experiences. When a raging fire destroyed the Opéra comique building in Paris on May 25, 1887, a New York Times correspondent, noting that the seats, boxes, and balcony were gone, described the building as “an immense black hole.”

1807 drawing of The Black Hole of Calcutta by James Cundee

Predating its adoption by physics, the phrase “black hole” has a long literary history of denoting a dark dungeon. As early as 1844, Edgar Allan Poe used it in his short story The Premature Burial and as recently as 1997, Thomas Pynchon referred to the Black Hole of Calcutta in his postmodernist novel Mason & Dixon. Its use in science can be traced back to the influential physicist John Archibald Wheeler, who popularized it but didn’t originate it — the originator, as is often the case with linguistic invention, was an ordinary person whom history has rendered anonymous. In her enchanting book Black Hole Blues, astrophysicist Janna Levin relays the origin story: Weary of using the tedious “completely collapsed gravitational object,” Wheeler hungered for a more concise term; during a lecture he delivered in 1967, an audience member shouted: “How about black hole?” Wheeler took to the phrase and went on to insert it into lectures and papers until it became the dominant vocabulary.

Natarajan notes the inadvertent perfection of this spontaneously generated term:

What is perhaps most surprising is just how well some of these descriptions fit an astrophysical object that had not yet been observed. In astronomy, a black hole is a physical location of no return.

Natarajan traces the route of this astrophysically perfect term from the grim and gritty prisons of Calcutta to the ivory towers of Cambridge, England:

In 1783, when an English country parson, John Michell, first proposed the idea of a “dark star,” he could never have imagined that we would one day detect them. Michell, a polymath born in 1724, studied at Cambridge and later taught Hebrew, Greek, mathematics, and geology there. Although no portraits of him exist, a contemporary described him as “a little short man, of black complexion, and fat.” A man of the cloth, he moved from Cambridge to a parish in Thornhill, near Leeds. Despite his religious commitments and duties, he was very much at the leading edge of science, and his reputation for originality was such that many of the active scientists of the day, the likes of Benjamin Franklin and Henry Cavendish, visited and maintained regular correspondence with him. They had much to discuss; Michell’s scientific contributions include describing the strength of magnetic fields and developing a theory for how earthquakes propagate through faults on the earth’s surface.

[…]

In a letter to Henry Cavendish dated November 27, 1783, Michell anticipated that such “dark stars” would be observable only by the impact they had on bodies revolving around them.

But as Newton’s particle theory of light fell out of favor, Michell’s concept of dark stars no longer made sense. It would be another century and a half until Einstein’s theory of general relativity made room within the canon of scientific understanding for the possibility of such nonluminous astronomical objects.

Natarajan considers the presently indispensable role of black holes in the unfolding cosmic puzzle and puzzlement of our understanding:

Today we know that black holes exist in the centers of most, if not all, galaxies. Our own galaxy, the Milky Way, harbors one such black hole four million times the mass of our sun… Fortunately, our solar system is way too far from the center of the Milky Way for us to feel the presence of or be affected by its central black hole.

Astronomers now believe that black holes, despite their odd behaviors, are an inevitable consequence of the standard physics that describes the evolution of stars. The theory of stellar evolution predicts that stars born fifteen to twenty times more massive than our sun, after exhausting their fuel supply of hydrogen, will end their lives as black holes. Black holes may have exotic properties, but they are important constituents of the universe, playing a significant role in the assembly and evolution of galaxies.

This nonlinear and bumpy path from ideation to acceptance, Natarajan argues, is emblematic of how major scientific discoveries tend to progress and how the grand human sensemaking journey unfolds:

We are living in a disorienting universe, whose expansion is accelerating. And at no other period in human history have we had to contend head on so frequently with the provisionality of our understanding. We have a cosmic map that is eternally in flux. The fact that by their nature scientific truths are subject to refinement and revision is now an inescapable part of our reality. Our world view has shifted sharply in the past hundred years, rewriting the very sense of who we are, where we came from, and where we are headed.

Complement Natarajan’s stimulating Mapping the Heavens with cosmologist Janna Levin’s poetic history of LIGO and gravitational astronomy, physicist Sean Carroll on the universe and our search for meaning, and photographer Michael Benson’s visual history of four millennia of picturing the cosmos.