Revealing Answers from the Edge

Each year, Edge (an outgrowth of a group known as The Reality Club, made up of "some of the most interesting minds in the world") asks its members a single question and publishes their answers. This year, the question is particularly challenging:

"What do you believe is true even though you cannot prove it?"

The positioning of this question is interesting:

"Great minds can sometimes guess the truth before they have either the evidence or arguments for it (Diderot called it having the 'esprit de divination')."

Many of the respondents chose to focus on the issue of intelligent life in the greater universe, revealing a growing interest in and intuitive understanding of the nature of life in the universe. A few are still steadfastly anthropocentric, but most display a remarkable and perhaps new openness to broader perspectives. Here's a sampling:

ALEXANDER VILENKIN, Physicist; Institute of Cosmology, Tufts University

There are good reasons to believe that the universe is infinite.

If so, it contains an infinite number of regions of the same size as our observable region (which is 80 billion light years across). It follows from quantum mechanics that the number of distinct histories that could occur in any of these finite regions in a finite time (since the big bang) is finite. By history I mean not just the history of the civilization, but everything that happens, down to the atomic level. The number of possible histories is fantastically large (it has been estimated as 10 to the power 10 to the power 150), but the important point is that it is finite.

Thus, we have an infinite number of regions like ours and only a finite number of histories that can play out in them. It follows that every possible history will occur in an infinite number of regions. In particular, there should be an infinite number of regions with histories identical to ours. So, if you are not satisfied with the result of the presidential elections, don't despair: you candidate has won on an infinite number of earths.

This picture of the universe robs our civilization of any claim for uniqueness: countless identical civilizations are scattered in the infinite expanse of the cosmos. I find this rather depressing, but it is probably true.

Another thing that I believe to be true, but cannot prove, is that our part of the universe will eventually stop expanding and will recollapse to a big crunch. But this will happen no sooner than 20 billion years from now, and probably much later.

MARTIN REES, Cosmologist, Cambridge University; UK Astronomer Royal; Author, Our Final Hour

I believe that intelligent life may presently be unique to our Earth, but that, even so, it has the potential to spread through the galaxy and beyond—indeed, the emergence of complexity could still be near its beginning. If SETI searches fail, that would not render life a cosmic sideshow Indeed, it would be a boost to our cosmic self-esteem: terrestrial life, and its fate, would become a matter of cosmic significance. Even if intelligence is now unique to Earth, there's enough time lying ahead for it to spread through the entire Galaxy, evolving into a teeming complexity far beyond what we can even conceive.

There's an unthinking tendency to imagine that humans will be around in 6 billion years, watching the Sun flare up and die. But the forms of life and intelligence that have by then emerged would surely be as different from us as we are from a bacterium. That conclusion would follow even if future evolution proceeded at the rate at which new species have emerged over the 3 or 4 billion years of the geological past. But post-human evolution (whether of organic species or of artefacts) will proceed far faster than the changes that led to emergence, because it will be intelligently directed rather than being—like pre-human evolution—the gradual outcome of Darwinian natural selection. Changes will drastically accelerate in the present century—through intentional genetic modifications, targeted drugs, perhaps even silicon implants in to the brain. Humanity may not persist as a single species for more than a few centuries—especially if communities have by then become established away from the earth.

But a few centuries is still just a millionth of the Sun's future lifetime—and the entire universe probably has a longer future still. The remote future is squarely in the realm of science fiction. Advanced intelligences billions of years hence might even create new universes. Perhaps they'll be able to choose what physical laws prevail in their creations. Perhaps these beings could achieve the computational capability to simulate a universe as complex as the one we perceive ourselves to be in.

My belief may remain unprovable for billions of years. It could be falsified sooner—for instance, we (or our immediate post-human descendents) may develop theories that reveal inherent limits to complexity. But it's a substitute for religious belief, and I hope it's true.

CAROLYN PORCO, Planetary Scientist; Leader, Cassini Imaging Team; Director, CICLOPS, Space Science Institute, Boulder

This is a treacherous question to ask, and a trivial one to answer. Treacherous because the shoals between the written lines can be navigated by some to the conclusion that truth and religious belief develop by the same means and are therefore equivalent. To those unfamiliar with the process by which scientific hunches and hypotheses are advanced to the level of verifiable fact, and the exacting standards applied in that process, the impression may be left that the work of the scientist is no different than that of the prophet or the priest.

Of course, nothing could be further from reality.

The whole scientific method relies on the deliberate, high magnification scrutiny and criticism by other scientists of any mechanisms proposed by any individual to explain the natural world. No matter how fervently a scientist may "believe'" something to be true, and unlike religious dogma, his or her belief is not accepted as a true description or even approximation of reality until it passes every test conceivable, executable and reproducible. Nature is the final arbiter, and great minds are great only in so far as they can intuit the way nature works and are shown by subsequent examination and proof to be right.

With that preamble out of the way, I can say that for me personally, this is a trivial question to answer. Though no one has yet shown that life of any kind, other than Earthly life, exists in the cosmos, I firmly believe that it does. My justification for this belief is a commonly used one, with no strenuous exertion of the intellect or suspension of disbelief required.

Our reconstruction of early solar system history, and the chronology of events that led to the origin of the Earth and moon and the subsequent development of life on our planet, informs us that self-replicating organisms originated from inanimate materials in a very narrow window of time. The tail end of the accretion of the planets—a period known as "the heavy bombardment"—ended about 3.8 billion years ago, approximately 800 million years after the Earth formed. This is the time of formation and solidification of the big flooded impact basins we readily see on the surface of the Moon, and the time when the last large catastrophe-producing impacts also occurred on the Earth. In other words, the terrestrial surface environment didn't settle down and become conducive to the development of fragile living organisms until nearly a billion years had gone by.

However, the first appearance of life forms on the Earth, the oldest fossils we have discovered so far, occurred shortly after that: around 3.5 billion years ago or even earlier. The interval in between—only 300 millions years and less than the time represented by the rock layers in the walls of the Grand Canyon—is the proverbial blink of the cosmic eye. Despite the enormous complexity of even the simplest biological forms and processes, and the undoubtedly lengthy and complicated chain of chemical events that must have occurred to evolve animated molecular structures from inanimate atoms, it seems an inevitable conclusion that Earthly life developed very quickly and as soon as the coast was clear long enough to do so.

Evidence is gathering that the events that created the solar system and the Earth, driven predominantly by gravity, are common and pervasive in our galaxy and, by inductive reasoning, in galaxies throughout the cosmos. The cosmos is very, very big. Consider the overwhelming numbers of galaxies in the visible cosmos alone and all the Sun-like stars in those galaxies and the number of habitable planets likely to be orbiting those stars and the ease with which life developed on our own habitable planet, and it becomes increasingly unavoidable that life is itself a fundamental feature of our universe ... along with dark matter, supernovae, and black holes.

I believe we are not alone. But it doesn't matter what I think because I can't prove it. It is so beguiling a question, though, that humankind is presently and actively seeking the answer. The search for life and so-called "habitable zones" is becoming increasingly the focus of our planetary explorations, and it may in fact transpire one day that we discover life forms under the ice on some moon orbiting Jupiter or Saturn, or decode the intelligible signals of an advanced, unreachably distant, alien organism. That will be a singular day indeed. I only hope I'm still around when it happens.

KENNETH FORD, Physicist; Retired director, American Institute of Physics; Author, The Quantum World

I believe that microbial life exists elsewhere in our galaxy.

I am not even saying "elsewhere in the universe." If the proposition I believe to be true is to be proved true within a generation or two, I had better limit it to our own galaxy. I will bet on its truth there.

I believe in the existence of life elsewhere because chemistry seems to be so life-striving and because life, once created, propagates itself in every possible direction. Earth's history suggests that chemicals get busy and create life given any old mix of substances that includes a bit of water, and given practically any old source of energy; further, that life, once created, spreads into every nook and cranny over a wide range of temperature, acidity, pressure, light level, and so on.

Believing in the existence of intelligent life elsewhere in the galaxy is another matter. Good luck to the SETI people and applause for their efforts, but consider that microbes have inhabited Earth for at least 75 percent of its history, whereas intelligent life has been around for but the blink of an eye, perhaps 0.02 percent of Earth's history (and for nearly all of that time without the ability to communicate into space). Perhaps intelligent life will have staying power. We don't know. But we do know that microbial life has staying power.

Now to a supposition: that Mars will be found to have harbored life and harbors life no more. If this proves to be the case, it will be an extraordinarily sobering discovery for humankind, even more so than the view of our fragile blue ball from the Moon, even more so than our removal from the center of the universe by Copernicus, Galileo, and Newton—perhaps even more so than the discovery of life elsewhere in the galaxy.

J. CRAIG VENTER, Genomics Researcher; Founder & President, J. Craig Venter Science Foundation

Life is ubiquitous throughout the universe. Life on our planet earth most likely is the result of a panspermic event (a notion popularized by the late Francis Crick).

DNA, RNA and carbon based life will be found wherever we find water and look with the right tools. Whether we can prove life happens, depends on our ability to improve remote sensing and to visit faraway systems. This will also depend on whether we survive as a species for a sufficient period of time. As we have seen recently in the shotgun sequencing of the Sargasso Sea, when we look for life here on Earth with new tools of DNA sequencing we find life in abundance in the microbial world. In sequencing the genetic code of organisms that survive in the extremes of zero degrees C to well over boiling water temperatures we begin to understand the breadth of life, including life that can thrive in extremes of caustic conditions of strong acids to basic pH's that would rapidly dissolve human skin. Possible indicators of panspermia are the organisms such as Deinococcus radiodurans, which can survive millions of RADs of ionizing radiation and complete desiccation for years or perhaps millennia. These microbes can repair any DNA damage within hours of being reintroduced into an aqueous environment.

Our human centric view of life is clearly unwarranted. From the millions of genes that we have just discovered in environmental organisms over the past months we learn that a finite number of themes are used over and over again and could have easily evolved from a few microbes arriving on a meteor or on intergalactic dust. Panspermia is how life is spreads throughout the universe and we are contributing to it from earth by launching billions of microbes into space.

STEPHEN PETRANEK, Editor-in-Chief, Discover Magazine

I believe that life is common throughout the universe and that we will find another Earth-like planet within a decade.

The mathematics alone ought to be proof to most people (billions of galaxies with billions of stars in each galaxy and around most of those stars are planets). The numbers suggest that for life not to exist elsewhere in the universe is the unlikely scenario. But there is more to this idea than a good chance. We've now found more than 130 planets just looking at nearby stars in our tiny little corner of the Milky Way. The results suggest there are uncountable numbers of planets in our galaxy alone. Some of them are likely to be earthlike, or at least earth-sized, although the vast majority that we've found so far are huge gas giants like Jupiter and Saturn which are unlikely to harbor life. Furthermore, there were four news events this year that made the discovery of life elsewhere extraordinarily more likely.

First, the NASA Mars Rover called Opportunity found incontrovertible evidence that a briny--salty-sea once covered the area where it landed, called Meridiani Planum. The only question about life on Mars now is whether that sea—which was there twice in Martian history—existed long enough for life to form. The Phoenix mission in 2008 may answer that question.

Second, a team of astrophysicists reported in July that radio emissions from Sagittarius B2, a nebula near the center of the Milky Way, indicate the presence of aldehyde molecules, the prebiotic stuff of life. Aldehydes help form amino acids, the fundamental components of proteins. The same scientists previously reported clouds of other organic molecules in space, including glycolaldehyde, a simple sugar. Outer space is thus full of complex molecules—not just atoms—necessary for life. Comets in other solar systems could easily deposit such molecules on planets, as they may have done in our solar system with earth.

Third, astronomers in 2004 found much smaller planets around other stars for the first time. Barbara McArthur at the University of Texas at Austin found a planet 18 times the mass of Earth around 55 Cancri, a star with three other known planets. A team in Portugal announced finding a 14-mass planet. These smaller planets are likely to be rock, not gas. McArthur says, "We're on our way to finding an extrasolar earth."

Fourth, astronomers are not only getting good at finding new planets around other stars, they're getting the resolution of the newest telescopes so good that they can see the dim light from some newly found planets. Meanwhile, even better telescopes are being built, like the large binocular scope on Mt. Graham in Arizona that will see more planets. With light we can analyze the spectrum a new planet reflects and determine what's on that planet—like water. Water, we also discovered recently is abundant in space in large clouds between and near stars.

So everything life needs is out there. For it not to come together somewhere else as it did on earth is remarkably unlikely. In fact, although there are Goldilocks zones in galaxies where life as we know it is most likely to survive (there's too much radiation towards the center of the Milky Way, for example), there are almost countless galaxies out there where conditions could be ripe for life to evolve. This is a golden age of astrophysics and we're going to find life elsewhere.

KARL SABBAGH,   Writer and Television Producer; Author, The Riemann Hypothesis

I believe it is true that if there is intelligent life elsewhere in the universe, of whatever form, it will be familiar with the same concept of counting numbers.

Some philosophers believe that pure mathematics is human-specific and that it is possible for an entirely different type of mathematics to emerge from a different type of intelligence, a type of mathematics that has nothing in common with ours and may even contradict it. But it is difficult to think of what sort of life-form would not need the counting numbers. The stars in the sky are discrete points and cry out to be counted by beings throughout the universe, but alien life-forms may not have vision.

Intelligent objects with boundaries between being and non-being surely want to be measured— "I'm bigger that you", "I need a size 312 overcoat"—but perhaps there are life-forms which don't have boundaries but are continuously varying density changes in some Jovian sea. Intelligent life might be disembodied or at least lack a discrete body and merely be transmitted between various points in a solid material matrix, so that it was impossible to distinguish one intelligent being from another.

But sooner or later, whether it is to measure the passing of time, the magnitude of distance, the density of one Jovian being compared with another, numbers will have to be used. And if numbers are used, 2 + 2 must always equal 4, the number of stars in the Pleiades brighter than magnitude 5.7 will always be 11 which will always be a prime number, and two measurements of the speed of light in any units in identical conditions will always be identical. Of course, the fact that I find it difficult to think of beings which won't need our sort of mathematics doesn't mean they don't exist, but that's what I believe without proof.

PAUL DAVIES, Physicist, Macquarie University, Sydney; Author, How to Build a Time Machine

One of the biggest of the Big Questions of existence is, Are we alone in the universe? Science has provided no convincing evidence one way or the other. It is certainly possible that life began with a bizarre quirk of chemistry, an accident so improbable that it happened only once in the entire observable universe—and we are it. On the other hand, maybe life gets going wherever there are earthlike planets. We just don't know, because we have a sample of only one. However, no known scientific principle suggests an inbuilt drive from matter to life. No known law of physics or chemistry favors the emergence of the living state over other states. Physics and chemistry are, as far as we can tell, "life blind."

Yet I don't believe that life is a freak event. I think the universe is teeming with it. I can't prove it; indeed, it could be that mankind will never know the answer for sure. If we find life in our solar system, it most likely got there from Earth (or vice versa) in rocks kicked off planets by comet impacts. And to go beyond the solar system is the stuff of dreams. The best hope is that we develop instruments sensitive enough to detect life on extra-solar planets from Earth orbit. But, whilst not impossible, this is a formidable technical challenge.

So why do I think we are not alone, when we have no evidence for life beyond Earth? Not for the fallacious popular reason: "the universe is so big there must be life out there somewhere." Simple statistics shows this argument to be bogus. If life is in fact a freak chemical event, it would be so unlikely to occur that it wouldn't happen twice among a trillion trillion trillion planets. Rather, I believe we are not alone because life seems to be a fundamental, and not merely an incidental, property of nature. It is built into the great cosmic scheme at the deepest level, and therefore likely to be pervasive. I make this sweeping claim because life has produced mind, and through mind, beings who do not merely observe the universe, but have come to understand it through science, mathematics and reasoning. This is hardly an insignificant embellishment on the cosmic drama, but a stunning and unexpected bonus. Somehow life is able to link up with the basic workings of the cosmos, resonating with the hidden mathematical order that makes it tick. And that's a quirk too far for me.

LAWRENCE KRAUSS,  Physicist, Case Western Reserve University; Author, Atom

I believe our universe is not unique. As science has evolved, our place within the universe has continued to diminish in significance.

First it was felt that the Earth was the center of the universe, then that our Sun was the center, and so on. Ultimately we now realize that we are located at the edge of a random galaxy that is itself located nowhere special in a large, potentially infinite universe full of other galaxies. Moreover, we now know that even the stars and visible galaxies themselves are but an insignificant bit of visible pollution in a universe that is otherwise dominated by 'stuff' that doesn't shine.

Dark matter dominates the masses of galaxies and clusters by a factor of 10 compared to normal matter. And now we have discovered that even matter itself is almost insignificant. Instead empty space itself contains more than twice as much energy as that associated with all matter, including dark matter, in the universe. Further, as we ponder the origin of our universe, and the nature of the strange dark energy that dominates it, every plausible theory that I know of suggests that the Big Bang that created our visible universe was not unique. There are likely to be a large, and possibly infinite number of other universes out there, some of which may be experiencing Big Bangs at the current moment, and some of which may have already collapsed inward into Big Crunches. From a philosophical perspective this may be satisfying to some, who find a universe with a definite beginning but no definite end dissatisfying. In this case, in the 'metaverse', or 'multiverse' things may seem much more uniform in time.

At every instant there may be many universes being born, and others dying. But philosophy aside, the existence of many different causally disconnected universes—regions with which we will never ever be able to have direct communication, and thus which will forever be out of reach of direct empirical verification—may have significant impacts on our understanding of our own universe. Their existence may help explain why our own universe has certain otherwise unexpected features, because in a metaverse with a possibly infinite number of different universes, which may themselves vary in their fundamental features, it could be that life like our own would evolve in only universes with a special set of characteristics.

Whether or not this anthropic type of argument is necessary to understand our universe—and I personally hope it isn't—I nevertheless find it satisfying to think that it is likely that not only are we not located in a particularly special place in our universe, but that our universe itself may be relatively insignificant on a larger cosmic scale. It represents perhaps the ultimate Copernican Revolution.

MARC D. HAUSER, Psychologist, Harvard University: Author, Wild Minds

What makes humans uniquely smart?

Here's my best guess: we alone evolved a simple computational trick with far reaching implications for every aspect of our life, from language and mathematics to art, music and morality. The trick: the capacity to take as input any set of discrete entities and recombine them into an infinite variety of meaningful expressions.

Thus, we take meaningless phonemes and combine them into words, words into phrases, and phrases into Shakespeare. We take meaningless strokes of paint and combine them into shapes, shapes into flowers, and flowers into Matisse's water lilies. And we take meaningless actions and combine them into action sequences, sequences into events, and events into homicide and heroic rescues.

I'll go one step further: I bet that when we discover life on other planets, that although the materials may be different for running the computation, that they will create open ended systems of expression by means of the same trick, thereby giving birth to the process of universal computation.