How did the universe begin? How did life begin? Is there intelligent life beyond Earth, or are we alone in the cosmos?
These were some of the questions addressed at a remarkable symposium titled “Origins,” when distinguished scientists from a broad spectrum of disciplines gathered in Phoenix in early April. The event marked the kickoff of the Origins Initiative at Arizona State University, an ambitious inter-disciplinary research and outreach program led by ASU physicist Lawrence Krauss.
His goal was to begin the Origins Initiative “with a bang,” Krauss says. “I wanted to create a symposium that would be heard around the world.”
In terms of scientific star power, he certainly pulled it off. In an atmosphere that might be described as a “Woodstock of Science,” some of the best-known researchers and popular science communicators — familiar names like Brian Greene, Steven Weinberg, Richard Dawkins, Paul Davies, Craig Venter, and Steven Pinker — explored topics from the Big Bang to string theory, from human origins to the roots of consciousness, from evolution to astrobiology.
The four-day event was capped by a full day of public lectures at ASU’s 3,000-seat Gammage Auditorium, filled almost to capacity for every session with thousands more watching live on the internet. (Videos and more videos.)
The final speaker at the public event was to have been physicist Stephen Hawking, but a chest infection kept him in a hospital in California. His daughter, Lucy Hawking, delivered his presentation, showing her father’s slides and playing his pre-recorded narration. In the talk, titled “Why Go Into Space?”, Hawking argued that although robotic space missions have proved incredibly successful, they cannot match “the excitement of manned space flight.” Moreover, he argued, humanity’s long-term survival depends on our colonization of other worlds; Earth is too risky a basket in which to keep all our eggs. "If the human race is to continue for another million years, we’ll have to boldly go where no one has gone before,” Hawking said.
The Chances for Alien Life
First, however, we'd like to know if others are out there already. As several presenters pointed out, a half century of SETI radio searches have turned up nothing. But the searches so far have been so spotty that the non-results mean little.
Whether alien civilizations will turn out to be common or extremely rare hinges on several distinct questions. The first is how likely, or unlikely, it is for life to get started on a suitable planet. Others address how likely it is for primitive life (think bacteria) to evolve into beings that build spaceships, or at least radio transmitters.
As a number of presenters at the symposium stressed, the appearance of thinking, talking, tool-using Homo sapiens resulted from a vast number of evolutionary accidents. These would almost certainly not happen again if we were to rerun our planet’s history. The question is, how likely would it be for any intelligent, technological species to arise? Is a machine-building level of intelligence truly a fluke? Or would "convergent evolution" drive this way by a variety of paths, in the same way that eyes, for instance, have evolved independently many times in Earth's history?
Biologists, who work with creatures here on Earth, tend to be skeptical about the likelihood of alien radio builders. Astronomers, who deal in cosmic immensities, tend to be the bold ones on this question. But not always. “It was Darwin who showed how matter and energy could turn into complexity, and produce a machine which is capable of internalizing the universe,” said evolutionary biologist Richard Dawkins, recently retired from Oxford University. “That’s an astonishing thing.” Given the existence of simple organisms, he said, the eventual rise of complexity seems almost guaranteed.
But the leap from complexity to intelligence may be a cosmic fluke, he and several others argued. Dawkins pointed out that while eyes may have arisen from scratch as many as 40 times in our planet’s history, symbolic language has arisen just once. Moreover, full-blown language seems to have appeared only after Homo sapiens had already lived for tens of thousands of years.
“Human symbolic consciousness, which is the underpinning of our cognitive singularity, is a very recent acquisition in the human lineage,” stressed Ian Tattersall of New York's American Museum of Natural History. “And, even more importantly, it’s not a simple extrapolation of the trends that preceded it.”
Which means that even if life itself is common in the universe, linguistic, symbol-using creatures like ourselves may be quite rare indeed.
A deeper question asks why the universe has conditions that allow life to arise anywhere. As many physicists and cosmologists have pointed out, the laws of physics themselves, and in particular the fundamental physical constants, seem to be remarkably well arranged to allow for the existence of any kind of complex matter whatever. The nature of atoms and molecules, the strengths of the known forces, the properties of stars and galaxies — all of it seems to be “just right.”
If some of the fundamental constants (which seem to be arbitrary) had values just a little different, not even atoms could exist. In other cases the Big Bang would have either quickly recollapsed or dissipated away to practically nothing, rather than producing stars and planets.
This is sometimes referred to as cosmological “fine tuning.” Theories that explain it — without relying on deliberate planning by an outside designer — are often based on “anthropic reasoning” or the “anthropic argument.” This idea is simple. You merely posit that many other regions of spacetime exist — perhaps other universes disconnected from ours — in which the physical constants take on a wide variety of random values. Most of these universes will not be “bio friendly.” We, however, will necessarily find ourselves in one of the rare, special places that are. This will be true no matter how rare and unlikely the bio friendly universes are.
This idea of a wider “multiverse” has been gaining ground for decades (see Sky & Telescope, March 1983, page 211). It has been getting boosts from several branches of modern physics. These include the “inflation” model of the Big Bang, which seems to predict that big bangs indeed happen endlessly in spaces outside ours, and string theory and quantum theory, which also seem to allow for unseen regions of spacetime that could be considered separate universes.
“If there’s a multiverse — regions in which different parts have different values for constants like the strength of the dark energy — then the anthropic argument just becomes common sense,” said physicist Steven Weinberg of the University of Texas (another Nobel laureate).
As an analogy, Weinberg asked why we find the liquid water we need all around us here on Earth — even though liquid water is rare on planets generally.
“If the Earth was the only planet in the universe, then it really would be amazing that it’s just the right distance from the Sun to make water liquid, and hence for life to be possible,” Weinberg said. However, if there are a great many planets located at all possible distances from their host stars — some too hot, some too cold — then “it’s natural that we’re on one of the planets that is at the right distance.”
Yet the idea of a multiverse, and the entire problem of anthropic reasoning, remains controversial. “Some of us chafe at using the words ‘anthropic’ and ‘common sense’ in the same sentence,” said Michael Turner of the University of Chicago. “Some of us feel like we ought to concentrate on our own universe before we imagine a multiverse.”
No End to Physics?
Another cutting-edge topic, string theory, also came up for debate, as organizer Krauss sat down for a one-on-one session with physicist Brian Greene of Columbia University. Greene, a longtime proponent of string theory, is also author of the bestselling book The Elegant Universe, which made string theory something of a household name in 1999.
String theory attempts to unite quantum theory and general relativity (Einstein’s enormously successful theory of gravity) by postulating that all fundamental particles are tiny loops of the same pure energy, rather than pointlike dots of different stuff. Differences in the loops' geometries and vibrations account for all properties of all fundamental particles; at least that's the theory's goal. However, after several decades of investigation, Greene admitted that string theory has yet to make a definitive, falsifiable prediction. That is, no one has figured out how to perform an experiment that would distinguish string theory from competing ideas. For that reason, it should really be called the “string hypothesis,” he said.
“We have not yet gotten to the point where we can start with the equations and come up with a definitive prediction, such that if it is not confirmed it, we would give the theory up,” said Greene. “And that’s not a happy place to be.”
Krauss asked if string theory was “falling on hard times.” No, replied Greene. “We are nowhere near stagnation. We’re in a period where we’re re-evaluating and trying to take all the things that have been discovered, and find how to best organize them so that we can gain the deepest understanding of this theory.” He added, “If string theory is wrong, I’d like to know right now. . . because I’m not in the game to prove one particular theory right or wrong. I’m in the game because I hope that I’m part of the generation that takes us one step further, regardless of what that step happens to be.”
Dan Falk is a science journalist based in Toronto.