We have in these pages chronicled the feats of great explorers of previous eras.  Yet our own era has witnessed what is perhaps the greatest, most awe-inspiring feat of exploration in the history of the man on earth:  the Voyager program that made its way through the outer solar system.  This was to be an exploration much different in kind from the great expeditions of old.  There were no pack mules, native guides, or recalcitrant companions; but there were the same incredible risks of environment and circumstance that have accompanied exploration from the time the Phoenicians first circumnavigated Africa.  The Voyager probes were man’s first tentative steps to walk beyond the confines of his own planet.  Perhaps when the long perspective is finally taken by our remote descendants, the Voyager program will rank among the most the most significant event in the history of our species.

The idea of exploring the outer solar system had long enchanted astronomers.  But it was not until a unique event happened that this dream became a feasible reality.  In the early 1970s, astronomers realized that the orbits of the outer planets (Jupiter, Saturn, Uranus, and Neptune) would coincide in a favorable alignment.  This event happened, we are told, only once every 176 years.  It would be possible for a fast-moving spacecraft to take advantage of this alignment and see in a relatively short time what it might otherwise take decades to see.  In addition, a spacecraft would be able take advantage of the gravitational fields of these planets to “sling-shot” itself from one to the other at high velocities.

NASA knew that the program would be an expensive one, and that resistance to it would be strong.  President Nixon authorized the program on the condition that it only explore two of the outer planets; the scientists, however, shrewdly decided to plan for seeing all of them.  They correctly understood that once the first images of these planets came back, there would be support for extending the program further.  Indeed, to what better use could a NASA budget be put?  So planning began.  There would be two probes:  Voyager 1 and Voyager 2.  Each probe weighted about 780 kg. and was powered by a decaying plutonium isotope.  Through normal system degradation, they would lose about 0.8% of their power per year.

Voyager 2 was launched first, on August 20, 1977.  Its mission was to fly past the immense outer planets Jupiter, Saturn, Uranus, and Neptune.  Voyager 1 was launched soon after, but it was tasked with exploring Saturn and its large moon Titan.  Two probes were needed because one would not be able to provide the kind of “grand tour” that the scientists were looking for.  And so the great epic began.

It is difficult for us to appreciate the immense scale of space.  The average person can relate to waves, storms, jungles, fevers, and starvation brought about by expired provisions.  But space is totally different.  It was not designed for man.  It is terrifying:  dark, empty, silent, and indifferent.  Distances are vast; objects are strange, huge, and intimidating; and the hazards are partly known, and partly unknown.  The scientists who designed and carried out the Voyager missions showed a degree of patience and heroism that was every bit the equal of the Iberian monarchs of Spain and Portugal who patiently funded and supported the explorations of the great 15th century navigators.

Voyager 2 first encountered Jupiter in the summer of 1979.  Images of Jupiter are familiar to us today, but we must remember that no one had ever seen what the planet really looked like.  It is easy for us today to laugh at Pliny the Elder’s repetition of myths and fables of foreign lands in his Historia Naturalis; yet we forget that we were (and in some ways still are) just as ignorant of our own solar system.  We were limited by our inadequate earth-bound telescopes, which could show us little more than hazy clouds.  The first images sent back from this huge gas-ball were thus greeted with amazement and shock.  Active volcanoes were even discovered on the moon Io, the first time vulcanism had been observed anywhere beyond Earth.  If only Galileo and Huygens could have lived to see these photos.

Explorations of Jupiter’s moons followed; then Saturn was reached in 1981.  There was a moment of panic at NASA’s mission control right after the Saturn fly-by, when the probe’s cameras froze in place.  But engineers got it working again by gently rotating it back and forth, just as one might free a car spinning its wheels in snow.  The probe came closest to Uranus in January 1986.  This planet seemed to many to be a let-down; all that could be seen was a turquoise-blue ball.  But the planet did have its own surprises:  it possessed a weird rotation with a corkscrew-like magnetic field, and even had its own rings.  Even stranger was Uranus’s moon Miranda, which had a bizarre surface that looked like it had been gouged with gigantic set of fingers.

Neptune was reached in 1989, and the data relayed proved to be just as fascinating as everything that had come before it.  Once Neptune had been explored, the focus of the probes shifted to penetrating the so-called “heliosphere”; that is, the boundary between our solar system and interstellar space.  No objects in human history have traveled longer or faster than the Voyager probes.  Long after our race will have either expired or left Earth, these lumps of metal will be floating in interstellar space for tens of millions of years, perhaps longer, or perhaps to be picked up by some curious extraterrestrial civilization during this time.  In anticipation of this sublime expectation, the scientists who designed the Voyager probes outfitted it with a “golden record” meant to be an affidavit, so to speak, in testimony of our race and our civilization.  The record contained greetings in dozens of languages and some basic information about Earth.  In the literal sense of the word, it was perhaps one of the most optimistic acts ever taken.

Voyager 1 left the heliosphere in 2012; Voyager 2 is expected to enter interstellar space in 2019 or 2020.  Carl Sagan was involved with the Voyager program.  His unique genius was his ability to convey the awe and wonder of these fantastic scientific achievements to the general public in a way that tied them to history and philosophy.  It was typical of Sagan’s visionary ability to think of doing things no one else would think of doing.  As the probes were leaving the solar system, everyone thought that the time for photography had ended.  Not Sagan.  He petitioned strongly for mission control to turn the probe’s cameras around to look back on Earth.  This turned out to be surprisingly difficult to do, as no one could see the point.

But Sagan wanted to make a sublime point about man and the universe.  When the photo was actually taken, it showed the Earth as a minuscule blue dot set against a field of eternity.  No other image could quite convey the awesome preciousness of our planet and of life on Earth, when set against the immensity of the eternal void.  At a television conference, Sagan said these words:

Consider again that dot. That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every “superstar”, every “supreme leader”, every saint and sinner in the history of our species lived there – on a mote of dust suspended in a sunbeam…

The Earth is a very small stage in a vast cosmic arena. Think of the rivers of blood spilled by all those generals and emperors so that in glory and in triumph they could become the momentary masters of a fraction of a dot. Think of the endless cruelties visited by the inhabitants of one corner of the dot on scarcely distinguishable inhabitants of some other corner of the dot. How frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds. Our posturings, our imagined self-importance, the delusion that we have some privileged position in the universe, are challenged by this point of pale light.

When I first read these words, I found them very much evocative of Cicero’s Dream of Scipio (an essay I translated in my book Stoic Paradoxes).  In the Dream, Cicero imagines a scene of astral projection, where the characters in the essay are suspended in space, looking down on the Earth:

When I had looked on all of this, shocked, and had finished processing everything, I said, “What is this sweet sound that is filling my ears?”  “That is,” he said, “the sound produced by the acceleration and motion of these celestial spheres, separated in unequal intervals, but occupying distinct, measured proportions, and making high and low sounds with a varying and equal unity.  They cannot undertake such motions in silence.  And nature makes things such that heavy tones come from one extreme, and high tones come from the other…

Then Africanus said, “I see that you are still looking at the home and place of origin of mankind.  If it appears to be small, as it is, then just look at the heavenly bodies, and disregard the petty affairs of man.  What fame can you achieve from the words of men, or what desired glory?  You can see that the earth is really only inhabited in a few sparse and narrow spots; and between the places where people live are vast empty regions, so that no real communication is possible between these groups.  They are located in places sometimes oblique, sometimes transverse, and sometimes adverse to you: from this fact you can certainly expect no glory…

“All of that land, which is occupied by you, is narrow from pole to pole, and broad from east to west.  Can you see that it actually is only a small island surrounded by that body of water which you call on Earth the Atlantic, or the Great Expanse, or the Ocean?  Despite its name, can you see that it is tiny?  From these same settled and known lands, which you can see from here, can your name (or anyone else’s name) ever spill over beyond the Caucasus Mountains, or swim the immense Ganges River?  Who in the eastern regions of the rising sun, or in the farthest regions of the north or south, will ever hear the sound of your name?  Taking away these regions for the moment, it is clear that your mortal glory wants to spread over a pathetically narrow area.  Will those who talk about us now, continue to talk about us in the future?

“Even if the descendants of future generations might want to hand down to posterity the plaudits of each one of us which they heard from their elders, nevertheless, because of the floods and fires of the earth, which always come from time to time, we can hardly expect a glory that is long-lasting, much less one that is eternal.  Why does it matter when those who were born after you may talk about you, when you gained nothing from those who lived before you?…” [Stoic Paradoxes, p. 94-97]

Who would have thought that a two thousand-year old treatise of Cicero would be so prescient, and so relevant, to today’s seekers of truth?  Sagan’s ability to convey the awe and wonder of the universe and our place in it is one of the things that make his seminal television series Cosmos still very much worth watching today.  I watched this series as a boy growing up, and I would have to credit Sagan as a tremendous influence on my own outlook and pedagogical style.  I loved how he blended history, philosophy, and modern science in a way that fired the imagination of the reader or viewer.  He was a man of true vision and learning.

The Voyager probes are still functioning, and still moving farther and farther away from their planet of origin.  Their mission was an unqualified success, a success that exceeded the wildest hopes and expectations of their original planners in the early 1970s.  It was not just a fantastic achievement in exploration and science:  it was a defining moment in human biology.  Who, upon learning of the scope of the Voyager program’s achievements, can fail to be overcome with awe?

Read more about the “Dream of Scipio” in my Stoic Paradoxes.