In the labs at The Rockefeller University, scientists’ attention is turned to the microscale as they investigate the fundamental mechanisms of life and disease. At the Lewis Thomas Prize Lecture, held at Rockefeller this spring, astronomer Chris Impey asked the audience to turn our attention upward and outward to the vastness of the entire observable universe and the possibility of extraterrestrial life.
The Lewis Thomas Prize for Writing about Science is an international award “honoring the scientist as poet.” Awarded annually since its establishment by Rockefeller’s Board of Trustees in 1993, it recognizes “the rare individual who bridges both worlds” of science and humanities and is named in honor of its first recipient, the influential physician, poet, and writer Dr. Lewis Thomas.
President Rick Lifton introduced this year’s prize winner, Chris Impey, with an anecdote about Impey’s high school physics teacher. As Lifton told it, the teacher seemed determined to turn his students away from the study of physics and astronomy with his dry, monotone explanations of the mathematical laws underlying the way our world works. Appalled by his teacher’s lack of wonder at the expansiveness and elegant order of the physical world, Impey became set on pursuing a career in science with the hope of satisfying his already relentless curiosity.
Today, Impey has had a nearly fifty-year career as an astronomer, professor, and writer that has taken him all over the globe. His contributions to astronomy and science writing have been recognized by many awards for research, teaching, and science writing. In his Lewis Thomas Prize lecture, Impey took us on a vivid journey through space as he discussed the search for exoplanets and extraterrestrial life and the questions this search raises, as well as the methodical and often arduous work required to study and make sense of the cosmos. Further insight into the exhilarating, sometimes highly speculative search for life on other planets can be found in Impey’s book, Worlds without End: Exoplanets, Habitability, and the Future of Humanity, published by MIT Press in 2023.
What became clear throughout the evening, from Impey’s talk to the dinner discussion that followed, is that a sense of wonder is inherent to his work. His and other astronomers’ endless curiosity can only be satisfied by meticulous, painstaking experimentation, a process that may seem far removed from the childlike wonder that initially inspires it. However, this methodical work in turn drives discovery that informs and increases their wonder at the elegant complexity of the natural world.
This interplay between imagination and rigor also shapes Impey’s writing. In his book, Impey provides a comprehensive walk-through of the experimental discovery methods used in the hunt for exoplanets—planets outside our solar system—and their applications and limitations. His writing style is accessible, from comparing the optics systems of massive space telescopes with the optics of the human eye to poetically likening giant, specialized devices called starshades to the petals of a sunflower. Quotes from Epicurus, Shakespeare, and other philosophers and writers are interspersed throughout, along with personifications of planets and whimsical descriptions of their character traits.
Fittingly, Impey quotes Lewis Thomas twice—once on his appreciation for Bach, and once from his lauded work The Lives of a Cell on the singularity of life on Earth within the solar system: “Viewed from the distance of the Moon, the astonishing thing about the earth, catching the breath, is that it is alive . . . Aloft, floating free beneath the moist, gleaming membrane of the bright blue sky, is the rising earth, the only exuberant thing in this part of the cosmos.”
Contrast this vision of Earth with the one made famous by the Pale Blue Dot, an image taken by NASA’s Voyager 1 in 1990 from a distance of six billion kilometers in which Earth is barely a speck on a dark sky. Impey embraces both depictions in his writing, as he balances an appreciation for the individuality of Earth with an awe at the great expanse of the observable universe and the endless possibilities it contains.
To help his readers appreciate this vast expanse, Impey provides a staggering sense of scale. In the 1990s, the Hubble Space Telescope counted 1024, or one million billion billion, stars—and there are many more planets than stars. He estimates that there are four billion Earthlike planets in the Milky Way, and up to 1021—one thousand billion billion—Earthlike planets, or “potential biological experiments,” in the universe. This “exoplanet census” inspires the search for extraterrestrial life.
Looking back down to Earth, Impey notes that “Life is tenacious and has gripped this planet like a fever for four billion years . . . and has radiated into almost every conceivable environmental niche,” which could argue for life’s ability to thrive beyond Earth and throughout the universe. On a more dramatic note, he quotes philosopher Thomas Carlyle on the implications of worlds beyond our own: “If they be inhabited, what a scope for misery and folly; if they be uninhabited, what a waste of space!”
The first exoplanet was not discovered until 1995, but outer space, exoplanets, and their potential to host life have long inhabited the human imagination. In 325 B.C., Epicurus wrote of an “infinite number of worlds” that are host to life. In the late nineteenth and early twentieth centuries, H.G. Wells’ The War of the Worlds and Ray Bradbury’s The Martian Chronicles captured the public imagination, along with popular movies from Le Voyage dans la Lune in 1902 to Alien and E.T. to Project Hail Mary, released in March 2026.
But as alien worlds live on in the public imagination, astronomers are the ones tasked with studying them. In his talk, Impey recounted a day on the beach in Hawaii, where he was reflecting on those worlds beyond our own. He recalled estimating that the volume of sand under his beach towel might be around one cubic meter, which would contain about fifty billion grains of sand. This is approximately equal to the number of potentially habitable worlds in the Milky Way. Looking down the stretch of beach, he estimated that the number of grains of sand on the entire beach is equivalent to the number of potentially habitable worlds in the entire universe. How long would it take to inspect each of them for life?
To make sense of the cosmos, astronomers must study it in a systematic, rigorous way. Impey quotes Kepler mission scientist Natalie Batalha, who became a physics major when she “encountered the elegance of applying mathematics to nature” and “was moved that the universe could be described in numbers.”
In Harmonice Mundi (The Harmony of the Worlds), Johannes Kepler—the seventeenth century polymath for whom the Kepler mission was named—discusses the geometry of planetary orbits and revives the classical idea of the musica universalis, the celestial symphony of the harmony of spheres. In the same work, Kepler introduces and proves his third law of planetary motion, which states that the square of a planet’s orbital period is directly proportional to the cube of its distance from its star. Thus, the idea that inspired Batalha—that nature possesses an underlying order and that mathematics can reveal it—has animated astronomers’ work for centuries.
Impey writes that “As first used by Pythagoras, [the word] cosmos conveys a view of the universe as a complex yet orderly system. The creation of the universe establishes order out of the chaos.” Chaos is not merely a description of the universe’s complexity; the behavior of many planetary systems can be described by mathematical chaos theory, in which systems’ behaviors are deterministic but extremely sensitive to initial conditions, with tiny perturbations having effects that amplify over time. This phenomenon is commonly known as the butterfly effect. Despite this infinite chaos, the fundamental laws underlying nature enable the systematic study of the universe at the micro- and macroscale, as we use increasingly advanced experimental tools to find order within it.
Astronomers use a wide range of techniques to study exoplanets, including both direct and indirect measurements. The first exoplanets were detected indirectly, by observing the effect of a planet’s orbit on its star. This was accomplished using Doppler spectroscopy, in which tiny shifts in a star’s spectrum caused by the gravitational pull of an orbiting planet are detected, with these changes repeating predictably with each orbit. This method requires extremely high-precision instruments to detect such signals, which are often masked by noise.
Another method for exoplanet detection is the transit method, in which the shadow cast by a planet on its star is observed by continually measuring a star’s brightness over time. Again, a sense of scale helps us appreciate the high precision required. Our close neighbor Jupiter casts a shadow that would dim the brightness of the sun by about one percent, last for a single day during its twelve-year orbit, and only be observable from a particular orientation. Blink and you might miss it. In another example, a telescope in space must be aligned within one meter of its starshade, a spacecraft placed forty thousand kilometers in front of the telescope that mitigates diffraction from a star’s light to improve observation quality. Exoplanet discoveries require many, many observations taken over a long period of time, in a process Impey compares to “looking for a needle in a haystack.” The search for the first exomoon took NASA’s most powerful supercomputers five million hours of processing time.
Impey himself is no stranger to the grueling demands of the work. “As a graduate student, I had my own experience with looking for a needle in a haystack,” he writes. “Hunting down supermassive black holes is exciting, but comparing millions of images by staring at them with a simple eyepiece felt like a Sisyphean task.” He describes the work in his field as “brutally difficult” and discusses how limitations of the technology in turn limit the planets that can be identified and studied, in terms of distance, size, orbit, and the fundamental limits of the telescopes. Throughout his lecture and his writing, Impey emphasizes the demands of the work, stating that “What is required is patience—and fortitude.”
Beyond the technical challenges of the work itself, another difficulty arises in knowing where to look and what to look for. In the search for potential life on other planets, the common wisdom has been to follow the water. As Nobel laureate Albert Szent-Györgyi stated, “Water is life’s matter and matrix, mother and medium. There is no life without water.” Astrobiologists have therefore focused their search for life on planets in the so-called Goldilocks zone, where water can exist as a liquid at the surface, and used this metric to define the traditional zone of habitability. However, Impey suggests that our perception of uninhabitability on perceived hostile planets could simply be a limit of our imagination.
Are the only essential ingredients for life water, energy, and carbon-rich material? Must all of these be essential? There is no firm consensus among astronomers and astrobiologists about what life might look like on other planets. Carl Sagan even wrote a paper about the potential for life in Jupiter’s atmosphere, which Impey charmingly describes as a “whiff of Hades.” During his lecture, Impey asked the audience to accompany him on a journey from the “weird” to the “really, really weird” as he stretched our imaginations of what the building blocks of life in an alien world might consist of—from noncanonical amino acids (weird) to methane-based life forms (really weird) to life that does not rely on any form of the central dogma of DNA to RNA to protein as we know it (really, really weird).
Since we do not know what any alien life form might look like or be composed of, this creates a fundamental problem: it is difficult to detect something without knowing what it is that you are trying to detect. Or, as one prominent scientist in the audience pointed out in the discussion following Impey’s lecture, the fact that all life on Earth relies on the same underlying biochemistry may suggest that evolution repeatedly converges on a limited set of workable solutions, and that Earth really is the only place in which this experiment has worked. Impey acknowledges these limitations, but insists that in “a field that is limited only by imagination,” meaningful scientific progress remains possible.
Besides not knowing where to look and what to look for, we have a very certain lack of evidence that there is life out there. While Impey is convinced that probability favors the existence of life elsewhere in the universe—and, he suspects, intelligent life—he points out that Earth has many singular qualities and that our solar system is an “oddball.” He also writes that “Despite the almost certain abundance of habitable real estate in the universe, it’s conceivable that life on Earth was a unique accident.”
Life on Earth may be resilient and fill every niche, but it all relies on the same basic biochemistry and metabolic pathways. Scientist James Lovelock, who studied the Martian atmosphere for signs of life, observed that “The more I looked at our atmosphere, the more astonishing it was. It was weird, weird beyond belief,” and that the chances of the precise combination of elements in Earth’s atmosphere “occurring by ordinary, random chemistry are so remote that no computer will even give you a figure.”
Impey provides another striking example of the precise balance of many factors necessary to achieve life as we know it when he describes two “identical Earths,” with one receiving slightly weaker radiation from its star. This would affect the fundamental mechanisms of life, which would in turn affect the evolutionary clock. “After 4.5 billion years on one, you’d find plants, animals, and us,” he writes. “While after 4.5 billion years on the slightly cooler Earth, you’d [see] barren land and no life in the oceans.” He goes on to say that “long-term habitability of our planet wasn’t inevitable but instead contingent . . . we’re literally lucky to be alive.”
If our solar system is such an “oddball,” this raises the conundrum of what assumptions to make when determining how to define habitability elsewhere. As planetary scientist Edwin Kite put it, researchers face “the inadequacy of working from Earth’s analogy.”
In addition to the technical difficulties required of astronomy research and exoplanet hunting, several other practical difficulties exist. Early Earth’s atmosphere was toxic to life, and for millennia no signs of life would have been detectable from afar. As millions of years are a blink of an eye in geological time, another source of uncertainty in the search for biology on other planets arises from being unable to determine if we are observing a planet at the right moment in its geological history.
Further, for the five thousand exoplanets identified, Impey states that studying their atmospheres to detect traces of life would require five million observations taken over a span of ten years with the assistance of forty high-resolution spectrographs yet to be built, and there is no compelling evidence that any of these five thousand targets would be a hit. As yet, the closest exoplanet to Earth in terms of mass, orbit, star, and chemical composition is a planet called Kepler 452b. Reaching this planet to retrieve samples would take Voyager 1 ten million years. A planned mission to Saturn’s moon Titan—a close neighbor by astronomical standards—will take two decades and billions of dollars.
In the face of these challenges, Impey remains incredibly optimistic. “With persistence along with a few billion dollars here and there, if there’s life in our solar system, we will find it in the coming decades,” he writes. “With billions of habitable worlds in our galaxy, only a pessimist or a killjoy can suppose that all of them are dead.” In his lecture, Impey likewise stated his certainty that there is life out there and emphasized that, while ample challenges remain, this quest is fueled by endless curiosity and zeal.
The dinner following Impey’s talk was full of professors from Rockefeller, Weill Cornell, Princeton, and other peer institutions. It was a distinguished group, with several Nobel laureates in attendance. In this room full of accomplished scientists, the discussions at the dinner tables were dominated by genuine curiosity about Impey’s work and its implications, rather than technical methodologies or conceptual breakthroughs. Questions and speculations were raised about where the field of astronomy might go next. The guests’ excitement at the increasing convergence of astronomy and biology was clear, as was their wonder at the sheer scale of the unanswered questions that still remain.
Biologists at Rockefeller are no strangers to the persistence required to study life at the molecular level. As in astronomy, progress often depends on long stretches of repetitive, fastidious work punctuated by brief moments of discovery. While the fundamental biology questions studied at Rockefeller might not have the same grip on the public imagination as space exploration and alien life, occasionally these worlds do converge in popular culture.
In the recent film adaptation of Project Hail Mary, Earth’s fate depends on the success of experimental biology. The protagonist, a molecular biologist recruited by the government to investigate sun-eating microbes, arrives at his solution through trial and error, improvisation, and relentless observation. This process includes crude experiments—such as the “Venus in a box” improvised using supplies from Home Depot—incremental progress, and rare flashes of insight. Even in science fiction, discovery happens through tedious experimentation rather than cinematic revelation.
Early astronomers mapped the motions of the planets long before the discovery of exoplanets became possible. In biology, similar meticulous work—from classical genetics experiments to sequencing the human genome—has revealed the intricate worlds housed within our cells. In both disciplines, discovery emerges from a feedback loop between curiosity and discipline as wonder motivates hard work, which leads to a greater understanding that deepens our wonder.
Quoting Shakespeare, Impey writes that the planets “observe degree, priority, and place.” Scientists continue to uncover that hidden order, even when nature initially appears chaotic. As NASA scientist Jessie Christiansen stated, “My favorite thing about space is all of the things we don’t know yet.”
Impey shares this sense of optimism. “We won’t know if there is biology anywhere else unless we look . . . Time will tell if this is a quixotic quest,” he writes. While practical and conceptual difficulties are abundant, he points out that “then of course there’s that human instinct for exploration and our natural curiosity, both of which are unstoppable.”