Amateur astronomers hoping to share their love of the sky sometimes speak of "the friendly stars".  Certainly anyone who comes to really know the sky cannot look upward without seeing old friends visited before, friends to call on again and again, whether with a telescope, binoculars, or just lying in a grassy field on a warm spring evening, taking in the heavens with that venerable instrument, the human eye.

Yet learning more about the universe makes it seem, in many ways, less friendly.  For the stars are not lamps hung in the sky to guide us at night, but raging nuclear furnaces separated by emptiness so immense our minds cannot grasp its extent.  To study astronomy is to encounter violence beyond the human experience: stars which explode, incinerating their planets, or burn out into eternally dark cinders; sources of radiation so intense they outshine whole galaxies, powered by black holes that swallow entire stars; gravity that crushes atoms into subatomic particles or into nothingness; whole galaxies that explode, collide with one another, and devour their neighbours; a universe born in a creation fire still glowing today and destined--we know not which--either to collapse and be crushed from existence or expand into an eternity of darkness and cold.  Awesome it is to contemplate, but awful in its seeming hostility to life.

Awesome because what we discover in the sky seems so alien to our own experience.  Awful because to look at the sky is to ask, in the larger sense, "What is my place in the universe?".  We look upward from a small globe teeming with life and see an endless void: empty, lifeless, and violent.  To learn that not just one's own personal existence, not just all of humanity's experience, but that life itself appears insignificant and irrelevant to the universe is to stand humbled under cold and unfriendly stars.

Look upward to sky; look downward at the Earth.  Upward, blackness punctuated by points of fire, worlds by the dozens in our neighborhood, and all of them lifeless.  Downward, a globe not just home to a multitude of living creatures, but fashioned by life: its life-sustaining atmosphere itself created and maintained by life.  Earth is not merely home to life; in a real sense it is alive, but alone.

But are not the stars home to other forms of life, perhaps other intelligent species already sensing our electromagnetic birth cry and preparing to welcome us into the galactic community?  Almost certainly not: there is every reason to believe we are alone in the galaxy, and perhaps in the universe.

What is the meaning of life?  The meaning of life is to live.  To live is to expand the scope of life itself, by replicating, by adapting, by modifying the environment, and by evolving into other forms of life.  Over three billion years ago, through a fantastically improbable sequence of coincidences, the Earth became alive--we find the traces of primitive organisms in some of the most ancient rocks.  For almost two billion years, these single-celled creatures (prokaryotes), whose modern-day descendants are bacteria and blue-green algae, were the sole representatives of life.  Not until about a billion and half years ago did single celled creatures with a structure resembling the cells in our bodies (eukaryotes--cells with a nucleus) appear.  Only 700 to 800 million years ago did these single cells (protozoa) organise into multicellular life (metazoans).  All the enormous variety of life we observe on Earth has evolved since: in a relative instant compared to the 4.5 billion year history of the Earth.  And now, evolution has produced beings who look upward at the sky, downward at the Earth and ask, insistently, persistently like the children we are on the cosmic scale, "Why?  Why?  Why?".

... We are the inheritors of more than three billion years of ceaseless global molecular experimentation, of competition among individuals and species, of a relentless expansion of life into new environments and emergence of new capabilities.  How can we have the arrogance to believe, so recently evolved ourselves to a stage that we can truly be said to think, that we are unique--that no other intelligent beings see our Sun as a star in their sky and, as arrogantly, consider themselves unique?

It was physicist Enrico Fermi who first remarked, "If they existed, they would be here".  Life expands its own scope.  Life on Earth extends from the mid-oceanic ridges where the Earth's very crust  is born, to the peaks of the highest mountains and the most remote regions of the Antarctic.  In the span of one human lifetime, transcending the limits of our bodies through the cleverness of our minds, our own species has descended to the deepest points in the ocean, visited the most remote places on the planet, learned to fly in the air and then beyond into space, and on July 20, 1969 set foot on another world which had never before been host to life.  Products of billions of years of ever-expanding life, the very molecules of which we are made drive us to spread life ever further.  Already, our robot proxies have visited all the major worlds of our solar system, seeking life and finding none.

Is it reasonable to expect that life will cease to expand at the very moment it becomes capable of spreading further, outward, onward?  That after billions of years and countless quadrillions of organisms, life will remain huddled on one small planet, awaiting the day when the Sun dies and ends it all?  No.  Already we have taken our first steps outward.  Once the expansion begins in earnest, it will spread exponentially.  It took three billion years of evolution before life managed to assemble individual cells into complex creatures, then only a quarter as long to evolve beings capable of carrying life to other worlds.  Using only technologies we currently possess, and traveling no faster than the Voyager probes already bound starward, we could begin to explore the galaxy.  Even at so slow a speed--requiring between ten and a hundred thousand years to travel between stars, if each new outpost launched its own emissaries of life onward, life would spread everywhere in the galaxy in only 300 million years--less than half the time it took the first multicellular creatures to evolve into beings audacious enough to think such thoughts.  Using technologies likely to be developed in the next century, founded on scientific knowledge already in hand, life could populate the galaxy in just 4 million years--comparable to the time it took the first hominids to radiate from the Home Continent to the farthest corners of the Home Planet.

Four million or even three hundred million years is an eyeblink of time compared to the 10 billion years elapsed since the galaxy reached the stage where beings like us could develop.  If intelligent life is common then why, over the billions of years that preceded our appearance, has no species evolved earlier already filled the galaxy?

"If they existed, they would be here", says Fermi.  So where are they?  Nowhere in evidence.  Intelligent beings with technologies millions of years beyond our own, spread to the far ends of the galaxy, should not be difficult to detect.  We already possess the means to detect even primitive technological civilisations like our own at a distance of hundreds of light years.

If they existed, they--the first intelligent species to expand outward among the stars--would be here.  And since we look around and see nobody but ourselves, then it is only reasonable to conclude, "We are here, so we are them."  We evolved here and we have not yet begun to sow the seeds of life among the stars, but surely we will.  Three billion years ago, one planet, the Home Planet, came to life.  Slowly life spread across the Home Planet, gaining complexity and diversity until it could think of going yet further.

In a short time on the cosmic scale, beings throughout the galaxy will gaze at the friendly stars in their skies.  They will look upward and see, not a hostile and lifeless galaxy, but one teeming with life--the legacy of the planet that came to life and then brought life to a galaxy.  They will not be human, no more than we are australopithecus or fish or bacteria, yet they, in their number and diversity trillions of times beyond the scope of life on Earth, will be our children, heritors of our coming to understand the meaning of life and the role humans are to play in its grand pageant.

And surely, some residents of the Home Galaxy will then look inward upon its friendly stars, and then outward.  Contemplating the endless universe not yet alive and the eternity ahead, they will ask themselves, "What is the meaning of life?".  And discovering it, they will go onward.

And finally there is the reasonable certainty that this sun of ours must some day radiate itself toward extinction; that at least must happen, until some day this earth of ours, tideless and slow moving, will be dead and frozen, and all that has lived upon it will be frozen out and done with.  There surely man must end.  That of all such nightmares is the most insistently convincing. And yet one doesn't believe it.  At least I do not. And I do not believe in these things because I have come to believe in certain other things---in the coherencey and purpose in the world and in the greatness of human destiny.  Worlds may freeze and suns may perish, but there stirs something within us now that can never die again.

We are in the beginning of the greatest change that humanity has ever undergone.  There is no shock, no epoch-making incident, but then there is no shock at a cloudy daybreak.  At no point can we say, here it commences, now, last minute was night and this is morning.  But insensibly we are in the day.  What we can see and imagine gives us a measure and gives us faith for what surpasses the imagination.

--- H. G. Wells, "The Discovery of the Future," Nature, 65: 326-331 (1902).


Rood, Robert T. and James S. Trefil.  Are We Alone?  New York:  Charles Scribner's Sons, 1983.
Barrow, John D. and Frank J. Tipler.  The Anthropic Cosmological Principle.  Oxford:  Oxford University Press, 1988.