by Avi Loeb
Science is not an occupation of the elite in isolated ivory towers but an endeavor that benefits and excites all humans, irrespective of their academic backgrounds. I believe this is especially true when viewed from the vantage point of astrophysicists. The questions the universe presents us with are awesome and galvanizing. They are also humbling. Our job is to stare out at events that occurred long before we arrived and objects that will exist long after we’re gone. Compared to the subjects of our study, we have the briefest of windows available to us, precious little time to study the universe and attempt to tease out the answers to its mysteries and paradoxes.
…
I put my faith and hope in science. Throughout my life, my optimism has provided immediate rewards. Indeed, this experience of getting something for nothing, rich rewards in return for the simple, humble practice of the detective work of science, brings me to a closing thought.
With Paul Chesler, a postdoctoral fellow at Harvard’s Black Hole Initiative, I theorized the fate of matter as it approaches the singularity of a black hole. We decided to address the question by way of a simple theoretical model that combined quantum mechanics and gravity. And as we examined the mathematical implications of the model, we realized that it also applied to the time-reversed problem, in which matter expands rather than contracts. This suggested we needn’t run the risks of a trip into a black hole, which was likely to rip us apart by gravitational tide and certain to preclude Facebook posts, but could, instead, observe at no risk the expanding universe. That is, we could look up and around us at all the matter that started from an initial singularity in time, the Big Bang. The same equations that described a black hole singularity, we realized, could be used to figure out how the universe had obtained its accelerated expansion.
Just like the biblical story of Saul finding his kingdom by chance while searching for his father’s lost donkeys, Paul and I stumbled on an unexpected insight while pursuing a completely different goal. By aiming to better understand black holes, we uncovered a mechanism for explaining our accelerating universe.
Our theoretical model is incomplete. It requires much fine-tuning. Even if the model stands up to theoretical scrutiny, it will need to make new predictions that survive the guillotine of future data. Some or all of that work may prove useful for other theories and in other corners of science. And in the aftermath of ‘Oumuamua’s visit, it leaves me with a thought that never ceases to haunt me. It, too, is a lesson I have taken from our interstellar visitor.
An encounter with another civilization, as I have said, may be humbling. And given all that we might learn from an advanced civilization, in particular, we should even hope to be humbled. Such a civilization will no doubt know the answers to a great many questions we haven’t figured out and perhaps haven’t even asked. But in order for us to gain some intellectual credibility, it would be nice to start the conversation by offering our own scientific wisdom about how the universe was born.
Conclusion
Many scientists argue that we should communicate information to the public only once our collective detective work has produced a nearly unanimous conclusion. These colleagues of mine believe that discretion is necessary to preserve our good image. Otherwise, they reason, the public could come to doubt scientists and the scientific process. Indeed, this occurs even when there is near unanimous conclusion among scientists. Consider, they often point out, the minority of the public who still question climate change. Stepping into controversy that could erode the stature of science, they worry, is too great a risk.
But my view is different. I think that in order to be credible, we need to show that scientific inquiry is a process that is more common and familiar than much of the public presumes. Too often, the approach taken by my colleagues contributes to the populist view of science as an occupation of the elite and fosters a sense of alienation between scientists and the public. But science is not some ivory-tower affair that, through inaccessible means, yields ironclad truths that can be dispensed only by sages. The scientific method is, in fact, closer to the commonsense approach to problem solving that a plumber adopts when trying to fix a leaking pipe.
Indeed, I think researchers and the public would benefit from viewing the practice of science as not so very different from the practices of a wide swath of other professionals. We confront confounding data just like a plumber does a blocked-up pipe, and we draw on our knowledge, experience, and colleagues’ wisdom to proffer hypotheses. And these we test out against the evidence.
The outcome of the scientific process is not up to the practitioners, since reality is determined by nature. Scientists are just trying to figure out what reality is by collecting as much evidence as possible and arguing about various interpretations when the evidence is limited. This reminds me of what Michelangelo said when he was asked how he produced such beautiful sculptures from a block of marble: “The sculpture is already complete within the marble block, before I start my work. It is already there, I just have to chisel away the superfluous material.” Similarly, scientific progress is about collecting evidence that allows us to remove the large number of possible hypotheses that are superfluous.
The experience of having to reject some of our false ideas is humbling. We should not take our mistakes as insults but rather as opportunities to learn something new. After all, our modest island of knowledge is surrounded by a vast ocean of ignorance, and only evidence—not unwarranted convictions—can increase the landmass of this island. Astronomers especially should be inspired to modesty. We are forced to confront our insignificance in the cosmic scheme of the universe, and against the vast expanse of all physical phenomena, how limited is our understanding. We should be humble in our approach, allow ourselves to make public mistakes and take transparent risks as we attempt to learn about the universe. Just like children.
As I watched colleagues close ranks against the serious consideration of the hypothesis that ‘Oumuamua could be extraterrestrial technology, I often wondered: What happened to our childhood curiosity and innocence? Throughout the media storm that descended on me as a result of my most public work (yet) on SETI, I was often animated by a simple thought: If I attract one child somewhere in the world into science as a result of my answering the demands of the media, I will be satisfied. And if I make the public and, perhaps, even my profession more willing to entertain my unusual hypothesis, so much the better.
…
In the spirit of the thought experiments with which I opened this book, the ones that I put to my Harvard undergraduates, here’s another:
Imagine that back in, say, 1976, NASA uncovered proof of extraterrestrial life on another planet—say, Mars. NASA had sent a probe to the Red Planet; this probe conducted soil samples that were analyzed and found to contain evidence of life. And the result was that the ultimate question—is terrestrial life the only life in the universe?—had been clearly answered. The data was presented by the scientific community and embraced by the public.
As a result, for the past forty years, humanity has gone about its daily activities and scientific explorations with the understanding that there is nothing unique about terrestrial life, because if evidence of life exists on Mars, it is a near statistical certainty that it exists elsewhere. Guided by that understanding, the committees that evaluate and fund new scientific undertakings and instruments have decided to channel money toward the further search for life beyond Earth. Public funds have flowed to support these new explorations. Textbooks have been rewritten, graduate programs refocused, old presumptions challenged.
And now imagine that forty years after evidence of organic life was found on Mars, a small interstellar object—highly luminous, oddly tumbling, with a 91 percent probability of being disk-shaped—passed through our solar system and, without visible outgassing, smoothly accelerated from a path that deviated from the force of the Sun’s gravity alone, with an extra push that declined inversely with distance squared.
And now imagine that astron
omers gleaned enough data about this object to understand these anomalies and that a few scientists studied the data and declared that one possible explanation for this object’s peculiar features was that it was of extraterrestrial origin.
What, in this alternate reality, do you think would have been the profession’s and the public’s reaction to such a hypothesis?
With forty years to accommodate itself to evidence of extraterrestrial life, the world, I suspect, would have viewed this hypothesis as less exotic among all the unusual scenarios being offered to explain ‘Oumuamua’s peculiarities. Perhaps the world would also have spent the intervening forty years organizing itself in a way so that it was better prepared to detect and study ‘Oumuamua; this could have allowed scientists to detect ‘Oumuamua as early as July 2017, which would have given them sufficient time to launch a spacecraft to meet this peculiar object and photograph its surface from a close distance.
And perhaps, rather than awaiting the date when the Starshot Initiative sends its first lightsail craft out into the universe, as we are now, we would be awaiting the imminent return of the data from those very craft that were launched twenty years ago.
This thought experiment has two purposes. It should remind us that while we cannot control the data that the universe provides, we can control how we go about seeking it, assessing it, and recalibrating our future scientific undertakings. The world of possibilities to which we choose to open ourselves, bounded by the evidence we collect and that we allow our collective intelligence to consider, very much determines the world in which our children and grandchildren will live.
The second purpose of this thought experiment is to highlight an opportunity missed.
In 1975, NASA sent two Viking landers to Mars; these small probes arrived on the Red Planet the following year. They conducted experiments and collected soil samples, which they then analyzed. All of the results were transmitted back to Earth.
In October of 2019, Gilbert V. Levin—principal investigator on one of the experiments conducted by the Viking landers, the “labeled release” experiment—published an article in Scientific American stating the experiment had produced positive results that were proof of life on Mars. Designed to test Martian soil for evidence of life, Levin wrote in the article, “It seemed we had answered that ultimate question.”
The experiment was simple: Introduce nutrients to the Martian soil and see if anything in that soil consumed it as food. The lander was equipped with radioactivity monitors capable of detecting any traces of metabolism such consumption would produce. What is more, the lander could repeat the experiment after heating the soil to a degree that would kill off all known life. If in the first experiment there was evidence of metabolism and in the second experiment there was none, that would suggest biological life at work.
And that, according to Levin, is precisely what the experiment showed.
Other experiments, however, failed to find corroborating evidence of life on Mars. The result of the first was deemed by NASA to have been a false positive. And in the decades since, no subsequent NASA lander to Mars has included instruments to follow up on that experiment.
NASA and other space agencies are planning to land rovers on Mars with equipment designed to search for past signs of life. Appropriately, the device on NASA’s rover is named the Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals instrument—SHERLOC, for short. We can all take a measure of comfort from the fact that, however haltingly, the detective work of science continues.
Afterword
On September 14, 2020, scientists on Earth announced the first report of a possible biosignature in the atmosphere of another planet. This new potential evidence of extraterrestrial life had not been discovered near some far-off star. Rather, much like ‘Oumuamua, it had been found right next to Earth, in our own solar system.
A team led by Jane Greaves from Cardiff University in the UK had tentatively discovered a chemical compound called phosphine (PH₃) in the clouds of our neighboring planet, Venus. Searching for its spectral fingerprint in absorption of light at millimeter wavelengths, they had detected signs of the gas at an elevation of about 35 miles above the planet’s surface. The surface of Venus is currently too hot for liquid water to exist there, and so its rocky terrain is, as far as we know, inhospitable to life. But at such a height, the temperature and pressure resemble the conditions in Earth’s lower atmosphere—raising the distinct possibility that microbes could live inside liquid droplets suspended in the atmosphere of Venus.
On Earth, phosphine is a product of life. And as of this writing, no alternative chemical pathways have been identified for producing phosphine at the detected levels in the Venusian atmosphere.
This potential discovery galvanized the astronomy community much as did the sighting of ‘Oumuamua almost exactly three years earlier. As then, a flurry of calculations was inspired in my research group by the initial announcement. For instance, with Manasvi Lingam I calculated that the minimal density of microbes required to produce the phosphine found in the Venusian cloud deck is not excessive but rather many orders of magnitude lower than that found in air on Earth. In other words, there did not need to be very much life on Venus at all in order for signs of it to be detectable from Earth. In addition, Amir Siraj and I showed that planet-grazing asteroids could have shared microbes between the atmospheres of Earth and Venus—suggesting the testable possibility that their life had a common ancestry, if indeed life exists on Venus at all.
As with ‘Oumuamua, Venus’s phosphine marks the beginning, rather than the end, of a new journey of discovery. Next, scientists will get more data to test the reality of the reported detection and will also check if the only natural pathway for making phosphine is with living organisms. Conclusive evidence for life will have to await a probe that will physically visit Venus, scoop the material from its clouds, and search for microbes in those samples. The detective work, in short, goes on.
Acknowledgments
My deepest gratitude goes to my parents, Sara and David, who wisely encouraged my curiosity and wonder throughout my never-ending childhood, and to my remarkable wife, Ofrit, and our stunning daughters, Klil and Lotem, whose unconditional support and love make my life worth living.
Throughout my scientific career, I benefited greatly from collaborations with dozens of brilliant students and postdocs, a small fraction of whom are mentioned by name throughout the book and whose full scope of work can be found on my website, https://www.cfa.harvard.edu/~loeb/. As Rabbi Hanina remarked in the Talmud: “I have learned much from my teachers, more from my colleagues, and the most from my students.”
This book would never have been written without key team members. In particular, I am grateful to my literary agents, Leslie Meredith and Mary Evans, for convincing me to write this book in the midst of a hectic research schedule; to editors Alex Littlefield and Georgina Laycock for their generous support and advice on this writing project; and to Thomas LeBien and Amanda Moon for their extraordinarily professional and brilliant insights in assembling and organizing the materials of this book. I also thank Michael Lemonick, the editor of the Scientific American blog Observations, for providing me with an invaluable platform for developing my opinions and arguments.
This assembly of helpful collaborators taught me what I know about myself and hence about the world. After all, the horizons of the universe we discover are set by what we imagine exists out there.
Notes
1. SCOUT
page
3 “a messenger from afar”: International Astronomical Union, “The IAU Approves New Type of Designation for Interstellar Objects,” November 14, 2017, https://www.iau.org/news/announcements/detail/ann17045/.
3. ANOMALIES
33 its trajectory deviated from what was expected: Marco Micheli et al., “Non-Gravitational Acceleration in the Trajectory of 1I/2017 U1 (‘Oumuamua),” Nature 559 (2018): 223-26, https://www.ifa.hawaii.edu/~meech/papers/2018/
Micheli2018-Nature.pdf.
37 changed the tumbling period of ‘Oumuamua: Roman Rafikov, “Spin Evolution and Cometary Interpretation of the Interstellar Minor Object 1I/2017 ‘Oumuamua,” Astrophysical Journal (2018), https://arxiv.org/pdf/1809.06389.pdf.
38 “did not detect the object”: David E. Trilling et al., “Spitzer Observations of Interstellar Object 1I/‘Oumuamua,” Astronomical Journal (2018), https://arxiv.org/pdf/1811.08072.pdf.
39 astronomers reviewed images: Man-To Hui and Mathew M. Knight, “New Insights into Interstellar Object 1I/2017 U1 (‘Oumuamua) from SOHO/STEREO Nondetections,” Astronomical Journal (2019), https://arxiv.org/pdf/1910.10303.pdf.
39 “the greatest comet-finder”: NASA, “Nearing 3,000 Comets: SOHO Solar Observatory Greatest Comet Hunter of All Time,” July 30, 2015, https://www.nasa.gov/feature/goddard/soho/solar-observatory-greatest-comet-hunter-of-all-time.
39 ‘Oumuamua’s ice was entirely made of hydrogen: Darryl Seligman and Gregory Laughlin, “Evidence That 1I/2017 U1 (‘Oumuamua) Was Composed of Molecular Hydrogen Ice,” Astrophysical Journal Letters (2020), https://arxiv.org/pdf/2005.12932.pdf.
43 “a devolatilized aggregate”: Zdenek Sekanina, “1I/‘Oumuamua As Debris of Dwarf Interstellar Comet That Disintegrated Before Perihelion,” arXiv.org (2019), https://arxiv.org/pdf/1901.08704.pdf.
43 A similar concept: Amaya Moro-Martin, “Could 1I/‘Oumuamua Be an Icy Fractal Aggregate,” Astrophysical Journal (2019), https://arxiv.org/pdf/1902.04100.pdf.