by Avi Loeb
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Scientific progress has been stifled many times over the years because the gatekeepers who established and enforced orthodoxy believed they knew all the answers ahead of time. To state the obvious, putting Galileo under house arrest did not change the fact that the Earth moves around the Sun. Centuries later, the world is unanimous in siding with Galileo. But if that is the only lesson we take from that moment in time, I worry that we will fail to learn another crucial insight. Our debts run to both Galileo and to the authorities who muzzled him. It is not enough to celebrate the first. We must also learn to guard against the second.
Surrounded by the technological comforts of the twenty-first century, scientists imagine ourselves the descendants of Galileo rather than the descendants of the men (it was entirely men) who muzzled him. But that is an error akin to a scientist cherry-picking data. Our civilization is the product of not just our scientific advances but also those moments when for any number of reasons advances were delayed or even stopped in their tracks. We stand where we stand today because of the men and women who looked through the telescope, but also because of the men and women who refused to.
Science is a work in progress, and the pursuit of scientific knowledge is never-ending. But that progress does not follow a straight path, and the obstacles encountered are sometimes of humanity’s own making. Unfortunately, the humility accompanying our never-ending learning experience is, as in the case of ‘Oumuamua, sometimes forgotten out of hubris, whether exercised by ecclesiastical authorities, secular authorities, or, sometimes, scientists who declare victory prematurely and assume a line of inquiry has reached its end. Examples of the last instance are myriad. A brief sampling of such moments can help us decide if we’re too rapidly closing the door to every hypothesis the evidence concerning ‘Oumuamua supports.
Consider that in 1894, the prominent physicist Albert Michelson argued, after surveying the great advances in physics realized during the late nineteenth century: “It seems probable that most of the grand underlying principles have been firmly established. . . . An eminent physicist remarked that the future truths of physical science are to be looked for in the sixth place of decimals.” In contrast, over the subsequent several decades, physicists witnessed the emergence of the theories of special relativity, general relativity, and quantum mechanics, theories that revolutionized our understanding of physical reality and thus disproved Michelson’s forecast.
Similarly, in August 1909, Edward Charles Pickering argued in a Popular Science Monthly article that telescopes had reached their optimal size, fifty to seventy inches, and there was thus little point in building instruments with larger apertures. “Much more depends on other conditions, especially those of climate, the kind of work to be done and, more than all, the man behind the gun,” Pickering wrote. “The case is not unlike that of a battleship. Would a ship a thousand feet long always sink one of five hundred feet? It seems as if we had nearly reached the limit of size of telescopes, and as if we must hope for the next improvement in some other direction.”
Pickering was mistaken, of course; telescopes with larger apertures collect more photons, allowing scientists to see farther out into the cosmos and deeper into the past. Pickering directed the Harvard College Observatory from 1877 to 1919, and his unfortunate words therefore carried a lot of weight, especially on the East Coast. As a result, the West Coast became the center of observational astronomy in the United States for decades to come.
It happened gradually. In December 1908 George Ellery Hale’s sixty-inch telescope at Mount Wilson Observatory in California achieved first light. This was within Pickering’s declared optimum range and even as Hale’s telescope became more productive, Pickering and the East Coast stayed complacent. Hale, charting his own course, did not.
Hale soon built a hundred-inch telescope; it began operations at Mount Wilson in 1917 and was used by Edwin Hubble and Milton Humason shortly thereafter to determine that the universe is expanding—one of the twentieth century’s seminal discoveries. That hundred-incher was the biggest optical telescope in the world until 1948, when one twice as wide came online at California’s Mount Palomar Observatory. During its long career, the two-hundred-inch Palomar telescope helped astronomers discover radio galaxies and the active galactic nuclei known as quasars, which are fueled by gas falling into super-massive black holes, among many additional new sources of light.
And telescopes have just kept getting bigger, all the way up to the present day. Multiple ten-meter instruments are in operation currently, and three extremely large telescopes with apertures of twenty-four and a half meters (partnered with the Harvard College Observatory, reclaiming some of the ground that Pickering lost), thirty meters, and thirty-nine meters, respectively, are scheduled to come online in the next decade. Their large diameters will offer unprecedented angular resolution, and their large collecting areas will make them sensitive to faint, previously undetectable sources. Pickering had erred due to his arrogance. Not personal arrogance, but professional arrogance. He thought what his generation of scientists observed, understood, and determined was of interest was the peak of discovery; he didn’t appreciate that the ascent of science is one false peak after another.
Unfortunately, Pickering was not unique in this particular blunder. Indeed, it is a recurrent mistake throughout the history of science. In 1925, Cecilia Payne (later Cecilia Payne-Gaposchkin) became the first Harvard student to earn a PhD in astronomy (although the degree was officially awarded by Radcliffe, as Harvard did not grant doctorates to women at the time). She concluded that the Sun’s atmosphere was made mostly of hydrogen. When reviewing her dissertation, the highly respected director of the Princeton Observatory, Henry Norris Russell, argued that the Sun’s composition could not be different from that of the Earth and dissuaded Cecilia from including her conclusion in the final version of her thesis. While attempting to prove her wrong in subsequent years through the analysis of new observational data, he realized that she was right.
Arrogance again retarded a field when, in the mid-1950s, Charlie Townes encountered stiff resistance as he attempted to demonstrate the feasibility of the maser (short for “microwave amplification by stimulated emission of radiation”), which would, once built, amplify radiation at a frequency particular to a given element. Two Nobel laureates, Isidor Isaac Rabi and Polykarp Kusch, visited his laboratory at Columbia University in 1954 and implored him to cease his experiments on ammonia, insisting that the device would never work. Luckily, Townes persevered, and masers became the timekeeping devices in atomic clocks and were widely used in radio telescopes and deep-space spacecraft communication. In collaboration with a number of scientists, Townes did pioneering work with masers that led directly to the development of lasers.
Here’s an even more recent example. I once asked a prominent astronomer who studies objects in the Kuiper Belt—the ring of icy bodies beyond Neptune’s orbit—if he was looking for brightness changes way out there that might indicate artificial light. He scoffed at the very suggestion: “Why? There is nothing to look for.”
The establishment initially regarded Kuiper Belt objects (KBOs) as imaginary constructs. Pluto was the exception, of course; the largest KBO, it was discovered by Clyde Tombaugh in 1930 and thought to be a planet. But more than half a century later, UCLA astronomer David Jewitt couldn’t get telescope time or funding to hunt for KBOs, so he piggybacked his search with other projects. In 1992, he and Jane Luu finally discovered the first non-Pluto KBO using the eighty-eight-inch telescope at the top of Hawaii’s Mauna Kea.
In each instance, a leap forward was forestalled, and it was not because of a lack of available technology or an absence of imaginative curiosity or the unavailability of testable data. The delay stemmed from the arrogance, often well intended, of influential gatekeepers. And as much as we now celebrate the wonders of ever larger, grander telescopes and the world of possibilities they open up, what might have followed had scientists made these discoveries y
ears, generations earlier?
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Many scientists see themselves as a breed apart, members of an elite intelligentsia. Consciously or subconsciously, they want to separate themselves from the rabble. Such thinking motivates, at least in part, an argument made by many scientists I know: that scientists should communicate with the public only after they figure something out to a certainty. If laypeople knew the messy reality of science—that it’s full of starts and stops and dead ends—they’d brand every result as preliminary or questionable, the reasoning goes. Every important scientific consensus—such as the effect of human beings on Earth’s climate and the potentially disastrous consequences for us and all other life on the planet—could, some scientists fear, be summarily dismissed. This withholding strategy has the added benefit of making scientists look smarter than we actually are, and, adding to its appeal, it limits outside criticism.
But this approach is wrong. Keeping the public informed is our duty, and not just because so much scientific research is taxpayer-funded. A public that is deeply informed, engaged, and enthusiastic about scientific advances is a public that directs not just its financial support but the interest and efforts of its children, its brightest minds, toward the most confounding challenges. In that spirit, being more open as to what we know and what we do not will increase scientists’ credibility over the long haul. Shutting the public out until the very end can also lead to mistrust. After all, the anomalies we confront are not for scientists alone. They confront all humanity, and when there are breakthroughs, much like medical advances, it is to the benefit of everyone. We should show the world our work in progress, especially when it is full of uncertainties and buffeted by competing interpretations due to lack of conclusive evidence; we should let everyone see how surprised we often are at what we find.
Also, the general opprobrium with which the academy has met undergraduate interest in SETI has had a chilling effect on graduate-student interest. By one estimate, only eight scholars worldwide have completed doctorates in transparently SETI subjects. But that may be changing a little. As I write, seven graduate students are currently on track to receive PhDs in SETI-related subjects. What sorts of questions and, consequently, what sorts of experiments in pursuit of what kinds of data ought we to encourage in the next generation of astronomers? Here, again, ‘Oumuamua nudges us, if we care to pay attention. The traffic of technological equipment through interstellar space might be startling but it’s not noticeable until we develop instruments that are sensitive enough to detect it.
Indeed, I have sometimes—with a tip of the hat to Yuri Milner—described the search for extraterrestrial life as the ultimate venture-capital investment of scientific research. Any search method is, like investments, risky. With SETI, we have few clues regarding the properties of the needle we are searching for in the haystack of the universe, but if any needle is found, the reward will be tremendous. The return on such an investment would greatly eclipse other, narrower scientific interests. Just knowing that we are not alone would transform humanity itself, to say nothing of the knowledge we might gain from such a discovery.
I know it can be hard, especially for young scientists, to advocate for ideas deemed outré by the establishment. At this point in my life I have considerable career stability as well as an inherent disinclination—one that traces back to at least my first day of first grade—to seek the approval of others. Even so, I might not have been ready to advance the ‘Oumuamua-is-an-alien-lightsail hypothesis—or explore the possibilities it contained—had not the fragility of life and the window of time each of us individually has to advance the common good been brought keenly to my attention. For this, my scientific work on the universe was partly, although not entirely, to blame.
8
Vastness
When you are in the middle of reading a Sherlock Holmes story, it is easy to forget the vantage point of Holmes. For him, any individual case is, well, just one among many. And Holmes’s observation “Eliminate all other factors, and the one which remains must be the truth” applies to his habits of deduction whether he says it in The Sign of Four, “The Adventure of the Beryl Coronet,” “The Adventure of the Priory School,” or “The Adventure of the Blanched Soldier.”
In this way, productive astrophysicists are not unlike fictional detectives—while not all anomalies are the same, the process of trying to unravel them is.
“Eliminate all other factors,” orders Holmes. And there is, as it happens, another factor that bears on the question of ‘Oumuamua’s origins and purpose. It has to do not with ‘Oumuamua itself but with the universe that it is touring—a universe that is older and vaster than anything else we know. Its very ancientness and vastness, indeed, may hold the key to unlocking another one of ‘Oumuamua’s mysteries.
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During a family vacation to Cradle Mountain in the highlands of central Tasmania a decade before Oumuamua was discovered, I stepped outside after dinner and looked up. Because we were so far removed from the hubs of civilization, there was none of the usual light pollution that spoils the view from so many of the world’s backyards. I stared into a clear night sky.
It was overwhelming. Arrayed overhead were the countess stars of our galaxy, the Milky Way, stretching across the sky. Off to the side, I could see the Large Magellanic Clouds and our nearest galactic neighbor, Andromeda, a twinkling, iridescent patch that appears roughly the size of the moon. Some of my joy in the sight was in appreciating the fact that it was not timeless. It is anyone’s guess if humanity will be around to witness it, but it is a certainty that what we look up and see tonight is no more eternal than we are.
At the time, I was especially sensitive to the universe’s impermanence. Just a few years earlier, I had had the original idea of simulating the future collision between the Milky Way and Andromeda. I was particularly fascinated with our distant cosmic future, following on earlier papers where I showed that the accelerated expansion of the universe will leave our home galaxy in a void of empty space. Once the universe ages by a factor of ten, all distant galaxies will be pulled away from us faster than the speed of light, and humanity will be able to observe only the stars in our own galaxy. What would this galaxy look like? Aside from transforming the appearance of the night sky, the gigantic collision with Andromeda could kick the Sun to the outskirts of the merged galaxy and establish our new cosmic neighborhood for ten trillion years to come, until the light from all stars, including the faintest and most abundant dwarf stars, like Proxima Centauri, is extinguished. I convinced my postdoc T. J. Cox to simulate this future collision, and we reported in 2008 that within a few billion years, long before the Sun dies, our night sky will change and the stars from the two sister galaxies will mix to make a new, football-shaped galaxy, which we named Milkomeda.
It was remarkable to recognize, that night in Tasmania, the objects of my studies. The Milky Way and Andromeda galaxies were splashed across the sky in a brilliant cascade of light. Perhaps as a result of seeing them so clearly, I felt my place among them more keenly than I usually did. This is a pleasure of astronomy. By contrast, particle physicists do not have the privilege of seeing the Higgs boson with the unaided eye.
But my thoughts that evening were not occupied only with the transformation of our galaxy in the distant future. Uppermost in my mind was the question of how the first generation of stars and galaxies lit up in the very beginning of our universe, the scientific details of the story of the universe’s genesis.
The cosmic dawn was my first fascination as an astrophysicist. My interest began during my time at Princeton and sharpened with the passage of years. Eventually, my investigation of this mystery would influence my pursuit of another, shaping my thinking not just about the history of our universe but also about any civilizations with which we may have shared it.
When you gaze up on a clear night, as I did all those years ago in Tasmania, the numerous sun-like stars of the Milky Way look like the lights in the main cabin of
a giant spaceship streaming through the universe with passengers next to some of these lights. What can we learn about these passengers based on our brief encounter with ‘Oumuamua? What, for that matter, can we learn about ourselves?
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We date the birth of the universe, the Big Bang, to some 13.8 billion years ago. Fascinating, revelatory work has been done that has produced theory, data, and confirmed predictions concerning the universe’s earliest origins, including the common agreement that after the first hundred million years, everything was cloaked in darkness. Until, that is, the first star was born.
How did the earliest stars come into existence? After my arrival at Harvard in 1993, with Zoltan Haiman, my graduate student, and Anne Thoul, my postdoc, I worked out a theory to explain their formation.
Following the Big Bang, matter was spread more or less evenly across the rapidly expanding universe. That it was spread almost uniformly is crucial, for in some places, we theorized, the cosmos started out slightly denser than average. “Slightly” in the sense of one one-hundred-thousandth more dense. But those slight perturbations were sufficient. That was enough for gravity to start to pull matter into these increasingly dense regions and for clouds of gas, composed mostly of hydrogen atoms, to begin to assemble.
Timeline of the history of the universe. The solar system formed relatively late, only 4.6 billion years ago. Modern technology appeared on Earth only over the past century, 0.0000001 billion years ago. Many civilizations could have appeared and disappeared before we developed our modern telescope technologies to detect them.