This past spring an international team of astronomers announced their discovery of the most potentially Earth-like planet yet detected, a relatively small world orbiting a red dwarf star twenty light-years* away. At such a distance and with the rather unfortunate name Gliese 581c, the rocky orb probably won’t be in the running for its own Lonely Planet guide anytime soon. But that hasn’t stopped scientists dedicated to the search for ET from carefully uncorking champagne bottles and stoically expressing their barely contained glee. “Because of its temperature and relative proximity, this planet will most probably be a very important target of the future space missions dedicated to the search for extraterrestrial life,” said one of 581c’s co-discoverers, Xavier Delfosse of Grenoble University in France. “On the treasure map of the universe, one would be tempted to mark this planet with an X.”
With no less than 240 other planets having been discovered outside our solar system at the time of this writing—a number that is rapidly growing as planet-hunting skills and technologies evolve—the chances of finding life elsewhere in the cosmos have never seemed greater. But why is the universe hospitable to life in the first place? Physicists tell us that if any of the fundamental constants of nature—such as the mysteriously low strength of gravity or the precise values of atomic forces—had differed during the universe’s initial conditions to even the tiniest degree, life as we know it would never have formed. They call this the “fine-tuning problem.” According to some cosmological models, if we simply adjusted a decimal place or two, the quantum chaos that exploded from the big bang would still be a seething hot miasma, never having cooled and evolved into atoms. With another subtle tweak, the rate of cosmic expansion would already have spread all particles so far apart from one another that the universe would be a featureless void. Fortunately for us, the laws of physics happen to be fine-tuned exactly as they are, and here we find ourselves, contemplating a cosmos that we now know contains planets—some presumably even lush, living worlds like ours—in numbers far exceeding its trillions of stars.
So how did we get so lucky?
“Since the 1970s, theists have invoked this fine-tuning argument as empirical evidence for a creator by asserting that there are only two explanations: God or chance,” writes Robert Lawrence Kuhn, host of the PBS roundtable discussion series Closer to Truth, in the summer edition of Skeptic magazine. “However,” he adds, “to pose such a stark and simplistic choice is to construct a false and misleading dichotomy.” Instead, Kuhn proposes no less than twenty-seven different explanations for why we happen to find ourselves in such a biologically accommodating place. Grouping his “taxonomy of ultimate reality generators” into four broad categories—“One Universe Models,” “Multiple Universe Models,” “Nonphysical Causes,” and “Illusions”—Kuhn hopes to account for every explanation, or combination of explanations, that scientists, philosophers, and mystics have proposed as possible answers to the perennially perplexing question of why we exist.
Aside from more traditionally theistic notions like Intelligent Design, some of the currently fashionable theories in Kuhn’s cosmological taxonomy are those involving multiple universes or multiple dimensions, espoused in such recent books as Leonard Susskind’s The Cosmic Landscape, Lisa Randall’s Warped Passages, and Victor J. Stenger’s God: The Failed Hypothesis. Exceedingly popular among quantum physicists and string theorists, these “multiverse” ideas attempt to account for our universe’s life-friendliness by proposing that it just happens to be one of billions of other universes that didn’t turn out so well. After all, in a “multiversal” ocean of zillions of infinitely varied soap bubbles, they reason, there would have to be at least one with the precise qualities necessary to give rise to living beings like ourselves, and of course, that’s the one we’re in.
Still other scientists, arguing on behalf of what’s known as the anthropic principle—the general idea that our universe’s life-friendliness is not a random accident—find this kind of speculation absurd. “To be blunt, in my view, it’s just giving up,” cosmologist James N. Gardner, author of Biocosm, told WIE. “It represents a failure to recognize that just as the appearance of a seemingly well-tuned natural world constituted a vital set of clues for Darwin to follow, so, too, does the appearance of a seemingly well-tuned cosmos constitute a vital set of clues that should be pursued.” Arizona State University physicist Paul Davies agrees. In his latest book, Cosmic Jackpot: Why Our Universe Is Just Right for Life, he argues that most theories about a multiverse simply represent a failure of the imagination. He much prefers two alternatives: 1) the idea that there is some kind of implicit life force or evolutionary impulse guiding the emergence of life and consciousness in our universe, or 2) what’s been described as Davies’ “self-creating universe in a teleological backward causation” theory.
Yes, the theory is as strange as it sounds, but Davies believes it’s no more bizarre than any other explanation in Kuhn’s taxonomy. He proposes that the natural laws forged so precisely fourteen billion years ago in the big bang happened to favor the eventual emergence of life because our existence as living beings, here and now, actually fine-tuned them to be that way—retroactively. “Crazy though the idea may seem at first,” Davies explains, “there is in fact no fundamental impediment to a mechanism that allows later events to influence earlier events.” Invoking arcane mysteries of quantum physics such as entanglement, nonlocality, and the idea that conscious observation plays an essential role in “collapsing” quantum potentials into concrete reality, Davies contends that the presence of conscious observers today is no accident. Our existence, he says, is due to the ability of conscious observations to ripple forward and backward in time, influencing even the quantum fluctuations that took place in the initial nanoseconds of the big bang itself—a time when the laws of physics were still susceptible to subtle tweaking. “If the conditions necessary for life are somehow written into the universe at the big bang,” Davies told New Scientist last fall, “there must be some sort of two-way link.” In other words, the universe may be continually pulling itself up by its own bootstraps—from the future to the past—as a self-correcting, self-contained, and very living system.
The concept of events preceding their causes, technically known as retrocausality, has long been theorized among scientists (and science fiction writers), with creative thinkers such as the famed Richard Feynman even offering mathematical proofs of how certain properties of physics work just as well backward as forward in time. Still, there’s never been any experimental evidence to lend real-world validity to the idea. But scientists are nothing if not inventive, and soon University of Washington physicist John Cramer hopes to conduct an elaborate quantum physics experiment (involving, among other household objects, six miles of fiber-optic cable and two photon detectors) that should put retrocausality to the test. If Cramer succeeds, Davies’ retrocausal, closed-loop theory may become the top contender for explaining why the universe seems so intricately suited for life. But Davies remains open-minded, insisting that all scientific explanations for the universe that have been presented so far may be limited not only by an overly materialistic bias but also by the limited cognitive framework in which we’re approaching the problem in the first place, “a mental straitjacket inherited from evolutionary happenstance.” The future, he believes, may yield possibilities that present-day theorists can’t even imagine.
In the end, perhaps we’ll admit that the great Bertrand Russell already came up with the simplest explanation: “The universe is just there,” he once declared, “and that’s all.”
* approximately 120 trillion miles