Weird Life: The Search for Life That Is Very, Very Different from Our Own

by David Toomey

  In 1979, Freeman Dyson, a mathematician and theoretical physicist working at the Institute for Advanced Study in Princeton, New Jersey, published a brief work called “Time without End: Physics and Biology in an Open Universe.” In it, he proposed that the basis of consciousness may be structure, and that structure may require no particular form of matter. If this is true, then it follows, he claimed, that “life is free to evolve into whatever material embodiment best suits its purposes.”5 He went on to propose a means by which life might survive in the future universe that current cosmology predicts, not for a mere billion years (when Earth’s surface will be too hot for familiar life) or even a trillion years (when most Sun-like stars will have burned themselves out), but for a literal eternity.

  Fifty years earlier, most scientists would have considered such a prospect flatly impossible. In the late nineteenth century, astronomers reasoned that since all closed systems eventually reach thermodynamic equilibrium, and since the universe is a closed system, there would come a time when every part of space settled into the same very low temperature—a condition astronomer Arthur Eddington called the “heat death” of the universe. Because life depends on warmer and colder places and the transfer of heat between them, it would mean the death of all life as well. But the premises of the heat death were soon called into question. In the late 1920s, astronomers confirmed that galaxies in all directions were moving away from our own, and that the universe—and space itself—was expanding. As long as the universe continued to expand, it would never reach thermal equilibrium.

  In 1979, Dyson held with evidence that the “observable universe”—that is, the part of the universe we can observe, an imaginary sphere 84 billion light years across and centered on us—was expanding at a faster rate than was the entire universe. Its relatively faster expansion meant that although all galaxies were receding from us, just inside the edge of the observable universe more and more of them were coming into view. Although the universe that Dyson imagined was growing emptier for a given volume of space, its total volume was increasing, and that was good news for life and intelligence. “No matter how far we go into the future,” he wrote, “there will always be new things happening, new information coming in, new worlds to explore, a constantly expanding domain of life, consciousness and memory.”6

  It was this “open” universe that would supply habitats to the sort of weird life that Dyson imagined. Although the heat death was no longer a threat, an ever-diminishing supply of usable energy in an ever-colder universe would require organisms to practice frugality, and Dyson suggested that they might do so by slowing their metabolisms. There would be challenges. Because thought is a product of metabolic processes, intelligent organisms would be obliged to slow their rates of consciousness. More generally, all organisms, even very cold ones, would overheat if they did not generate waste heat away from themselves. And because the efficiency of any such radiator drops off much faster than does its metabolic rate, overheating, ironically enough, would become a real danger. But Dyson conjectured that overheating might be avoided if the organisms lowered their metabolic rate as averaged over time, and that they might do so by spending a large part of their lives in hibernation.

  Although Dyson admitted that he could not imagine such organisms in detail (he could not, for instance, know whether there were functional equivalents of muscles or nerves), he noted that most biologists would be hard-pressed to imagine a cell if they had never seen one. He could, though, conjecture as to their general nature. He imagined a very distant future when most matter would have fallen into black holes, and yet he conceived a way for life to continue. “If it should happen, for example, that matter is ultimately stable against collapse into black holes when it is subdivided into dust grains a few microns in diameter,” Dyson wrote, “then the preferred embodiment for life in the remote future must be . . . a large assemblage of dust grains carrying positive and negative charges, organizing itself and communicating with itself by means of electromagnetic forces.”7 Life, then, would not be in a molecular cloud; rather, it would have become a molecular cloud.

  STARS

  The universe used to be a comfortable place. The idea that it is uncomfortable—that most nonterrestrial locales are barren and inhospitable—gained widespread acceptance only recently, in the early twentieth century. Before then and since ancient times, many astronomers, cosmologists, and philosophers assumed that the universe offered pleasant habitats in abundance. One rationale for a well-populated universe is a long philosophical tradition claiming that celestial bodies would be “wasted,” were it not for observers. Johannes Kepler, for instance, reasoned that since Jupiter’s moons cannot be seen from Earth with the naked eye, they must be meant for Jovians. In 1693, English theologian Richard Bentley enlarged the argument: “As the Earth was principally designed for the Being and Service and Contemplation of Men; why may not all other Planets be created for the like uses, each for their own inhabitants who have life and understanding.”8 Bentley’s idea of an Earth made for us, even carrying the authority of Genesis, may seem faintly risible. But it’s hard not to admire in his words an absence of self-centeredness as well—in the allowance for the possibility, if not probability, of other worlds and other beings.

  Among possible habitats, some natural philosophers counted not only planets and their moons, but stars. Two thousand years ago, in his satirical work True History, Assyrian rhetorician and satirist Lucian of Samosata imagined that the Sun itself might be inhabited. As recently as the eighteenth century, no less distinguished a personage than astronomer Sir William Herschel, discoverer of the planet Uranus, supposed that the part of the Sun we see from Earth is something like our aurora borealis, and that beneath it was a layer of dense clouds that shielded denizens of the surface from our sight. Herschel’s son John suspected that the ephemeral formations we call solar flares—and he called (rather more lyrically) solar willow leaves—might themselves be living creatures. No one gives much credence to these ideas now, but there have been more recent speculations of means by which life might survive in stars—or at least, certain kinds of life and certain kinds of stars.9

  WHITE DWARFS AND BLACK HOLES

  The current era in the universe’s history is a relatively active period when stars are forming, living, and dying. It will end when the universe is 1014 years of age and all stars have cooled and faded to stellar remnants—white dwarfs, brown dwarfs, neutron stars, and black holes. This begins a very long and relatively quiet period lasting until the universe is 1028 years of age, its stillness interrupted only when two white dwarfs collide and create a supernova explosion that for a brief moment brightens an otherwise darkened galaxy. The period would seem utterly inhospitable to life, and perhaps it will be. Nonetheless, in 1999 astrophysicists Greg Adams and Fred Laughlin, taking a page from Dyson, imagined life in the atmospheres of white dwarf stars.

  Some background is necessary. A star like the Sun generates energy by slowly fusing the light nuclei of hydrogen to the heavier nuclei of helium, and it does so as long as it has hydrogen left to fuse. During most of its lifetime, such a star is a balance of forces: the superheated gases of its interior pushing outward and the mutual gravitational forces of its parts pulling inward. When the star exhausts its hydrogen fuel and cools, the outward-pushing pressure diminishes, and the inward-pulling force overwhelms it, becoming so strong that the shell of electrons surrounding each atomic nucleus is squeezed, restricting each electron to a “cell” with a volume thousands of times smaller than the volume the electron would otherwise inhabit. The only thing that prevents the star from further collapse is outward pressure of the electrons against the walls of their cells—the electron degeneracy pressure. The star itself has become a white dwarf, a sphere about the size of Earth.

  White dwarf interiors are unimaginably dense—1014 grams per cubic centimeter—but their atmospheres, so Adams and Laughlin think, would allow mobility. Those atmospheres contain oxygen and carbon, and although the
y are quite cold, they are warm enough that they would allow those chemicals to interact in interesting ways. White dwarf atmospheres gain what heat they have by collisions with particles of dark matter, a process that will continue until the dark matter is exhausted, when the universe is 1025 years of age. Over such a span—100 billion times as long as it took for life to appear on Earth—even slow-moving molecules will have time to join in every conceivable pattern, including those necessary for life. The longevity of a stable environment, Adams and Laughlin argue, implies that life in white dwarf atmospheres is more than possible; it is likely. They also note that it would necessarily be a life quite unlike our own. In accordance with Dyson’s notions of energy conservation, metabolisms and rates of consciousness would be very slow. An intelligent creature living in a white dwarf atmosphere might take a thousand years to complete a single thought.

  Still, such beings would not be immortal. When the universe is 1040 years old, even protons will have evaporated into a diffuse radiation, and the only remaining stellar remnants will be black holes. Their radiation will provide all the warmth available anywhere, and it will be precious little. A black hole with a mass a few times that of the Sun would have a temperature of one ten-millionth of a degree above absolute zero. But again, given enough time, matter and energy will arrange themselves into a great many forms, some of them likely to be living. Adams and Laughlin suggest that because the era of black holes is extensive, lasting until the universe is 10100 years old, life near a black hole event horizon (that theoretical boundary around a black hole beyond which no light or other radiation can escape) would have a long time to take hold and a very, very long time to evolve into complex forms—albeit, owing to a deficit in available energy, not intelligent ones.

  This sort of speculation at present is untestable. But even the more modest hypotheses in the previous chapters present difficulties. As should be clear by now, the search for life elsewhere meets with problems because it requires life detection experiments. Whether performed with ground-based or space-based telescopes, unmanned spacecraft in orbit around planets or moons, or rovers and submersible robots, these experiments must be based on designs. Designs in turn must take into account aspects of microbiology, evolution, and planetary science. And because (as we’ve seen) scientists’ knowledge of all these fields is incomplete, they can’t be sure what makes for a good design, and they can’t be sure what to test for to begin with. The same lack of knowledge hampers and vexes even theorizing about life.

  In the late twentieth century, a number of scientists realized that the problems involved in designing instruments and agreeing on what to test for could be leapfrogged, and the search for extraterrestrial life could continue apace—if only all concerned were prepared to make two assumptions: one, that some subset of extraterrestrial life was at least as intelligent as humans; two, that it had the means and the will to communicate across interstellar distances. As it happens, there is a group of scientists who have learned to live and work with both assumptions. These are, of course, the radio astronomers and other researchers involved in the search for extraterrestrial intelligence, or SETI.

  CHAPTER SEVEN

  Intelligent Weird Life

  SETI has been with us since 1959, the year that physicists Giuseppe Cocconi and Philip Morrison published a paper in the journal Nature outlining an in-depth strategy by which radio telescopes might be used to detect the communications of extraterrestrials.1 Even for Nature, a journal known to publish work that approached the scientific fringe, it was audacious, beginning with what, it must be said, was a rather startling supposition:

  We shall assume that long ago [extraterrestrial civilizations] established a channel of communication that would one day become known to us, and that they look forward patiently to the answering signals from the sun which would make known to them that a new society has entered the community of intelligence.

  The paper’s conclusion, no less startling, was a call to action: “The presence of interstellar signals is entirely consistent with all we know now, and . . . if signals are present the means of detecting them is now at hand.”

  Cocconi and Morrison did not know that at that same time, the call had already been answered—or at least heard. A young radio astronomer named Frank Drake, then working at the National Radio Astronomy Observatory at Green Bank, West Virginia, suggested that it was possible to use the facility’s 26-meter receiver to detect artificial radio signals—that is, signals sent deliberately by someone. Drake made a case to the observatory’s director. First, such a project would cost next to nothing. He needed only a narrowband receiver and a parametric amplifier, and he could build both for $2,000. Further, the equipment could do double duty because the narrowband receiver could also search for the splitting of spectral lines in a magnetic field—a phenomenon known as the Zeeman effect. To Drake’s great surprise and pleasure, the director agreed. Drake acted quickly, and chose as targets two Sun-like stars: Epsilon Eridani and Tau Ceti. At the moment he turned the system on, he received a very strong signal. It was cause for a few hours of cautious excitement, but a false alarm. Otherwise, the only sound that came from the loudspeaker at Green Bank was static. Nonetheless, Drake had spurred the interest of other astronomers.

  In 1961 an informal meeting was held at Green Bank, its purpose to address questions associated with interstellar communication. There were many such questions, and Drake realized that they could be arranged hierarchically within an equation that, conveniently enough, might provide the meeting with an agenda. Now called the “Drake Equation,” it is a set of seven unknowns ranging from the physical (the rate of star formation) to the social (the longevity in years of a technological civilization).* Replacing the unknowns with numbers yields an estimate of the number of civilizations in the Milky Way galaxy presently capable of interstellar communication.

  By the time the conference ended, its members had estimated that the number of civilizations in the galaxy ranged from fewer than 1,000 to 1 billion, with Drake himself putting it at 10,000. The reason for the rather impressive range is that one factor was the longevity of such civilizations, and how long civilizations might last seemed sheer guesswork. Of course, the discussion—and the guesswork—has continued since. Generally, those advocating SETI projects have made the case for the existence of many extraterrestrial civilizations, and those dismissive of SETI have argued that there are probably few, if any.

  The position of the second group, roughly speaking, is this. Complex, larger cells with nuclei and various internal structures—the kinds of cells that make possible plants and animals—did not appear until 2 billion years after the first life—archaea and bacteria—had established itself. The relatively late arrival of complex life suggests that it does not and perhaps cannot develop easily. In all the 30 billion or so species that have crawled, swum, and fluttered, none have developed intelligence on par with Homo sapiens sapiens—a fact suggesting that the survival value of intelligence is no more or less than the survival value of features like, say, feathers or an exoskeleton or a prehensile trunk. It is true that some animals do manage a rudimentary technology, if technology is defined as toolmaking. But even if a species develops more advanced technology, unless that development is guided by scientific method it will progress slowly and fitfully, and it may never produce radio telescopes. Moreover, this line of thought continues, among all the civilizations in human history, scientific method arose only once, in western Europe in the late sixteenth and early seventeenth centuries. It follows that the chance for its appearance in any civilization (whether terrestrial or extraterrestrial) is slim. For all these reasons, those dismissive of SETI believe that although the universe may be full of life, almost all of it is likely to be microscopic, the equivalent more or less of archaea and bacteria, and looking for extraterrestrial civilizations is a waste of time.

  The position of SETI advocates, again roughly speaking, is this: Since the first life on Earth appeared only a few hundred mill
ion years after the planet’s crust hardened—that is, about as soon as life was possible—it was likely to appear anywhere as soon as it was possible. Intelligence has obvious survival value, and it has appeared on Earth in humans and to some degree in chimpanzees, dolphins, and several other animals. It may appear on many other life-bearing worlds as well. In time, intelligence is likely to develop science, technology, and radio telescopes. In the final analysis, say SETI advocates, we don’t know whether extraterrestrial civilizations exist, and the only way we might discover them is with SETI programs. SETI, its advocates maintain, is a small investment for what could be a very big payoff. What exactly do they think that payoff may be? At the very least, the knowledge that others share the universe with us. And at most, the possibility that they possess the wisdom and experience to show us how to meet and overcome the many challenges our civilization now faces.

  SETI STRATEGIES

  Since 1961, there have been more than sixty separate efforts.2 Most of these have followed Drake’s lead and Cocconi and Morrison’s recommendation that the easiest, cheapest, and most-likely-to-succeed search would be one that listens for radio signals. A few efforts—most notably the one led by Paul Horowitz at Harvard—have fitted an optical telescope with light detectors called photomultiplier tubes that can register a light pulse sent by a powerful laser. The justification for both strategies is straightforward. Both radio waves and lasers travel at the speed of light (that is, as fast as anything can travel), they can carry a great deal of information, they can be readily identified against the universe’s natural background radiation, and they are vastly cheaper than alternatives like robotic probes. These are advantages that any technically minded civilization would notice, and any technically minded civilization wishing to communicate across interstellar distances would put to use—or so SETI thinking goes.