Daniel Boorstin, the former U.S. librarian of Congess, wrote in his book The Discoverers: "The most promising words ever written on the maps of human knowledge are terra incognita -- unknown territory."
Those words are stamped on the error-prone charts of the Middle Ages. Later, the great seafaring explorers set out to broaden the world's horizons -- reaching continents unknown to them, circumnavigating the globe.
When Ronald Reagan spoke after the explosion of the space shuttle Challenger on January, 28, 1986, he connected the lives and accomplishments of those seven dead astronauts to the discoverers who had gone before them, dedicated also to "pulling us into the future."
"On this day 390 years ago, the great explorer Sir Francis Drake died aboard ship off the coast of Panama," Mr. Reagan noted. "A historian later said, 'He lived by the sea, died on it and was buried in it.' Well, today, we can say of the Challenger crew: Their dedication was, like Drake's, complete."
And so, too, the seven members of the crew of the space shuttle Columbia.
Before they were launched into space on Jan. 16, each spoke of the risks they knew they faced. No one who enters the space program does so naively; not when every part of your body is mapped, to check for flaws and have information on file to identify body parts in case of disaster. Columbia payload specialist Ilan Ramon, Israel's first astronaut, was particularly laconic about the perils, calling to mind the "Aw, shucks" mindset of the original seven Mercury astronauts, and evoking his background as a colonel in the Israeli air force.
The father of mission specialist David Brown said of his son hours after Saturday's tragedy that he'd died doing what he loved. And David Brown had recently told his family that should he die in space, "The program must continue."
Many of us noted over the weekend, a little ruefully, that we'd paid the Columbia mission no attention until we learned what happened as the shuttle was returning to Earth Saturday morning. But it was the same in 1986. And it was the same during the April, 1970, flight of Apollo 13, until it became known that the mission had turned into a desperate effort to save the lives of three astronauts. An early scene in the movie Apollo 13 shows NASA officials trying without success to get the television networks to cover more closely what was supposed to be, after all, just the third lunar landing. The public had moved on. The public focused once again, though, when something they had come to view as predictable suddenly became the story of accomplished individuals trying to get back to Earth. Such risks have always been part of the space program.
"People have a tendency to look at it as something that is more or less routine. Well, I can assure you, it is not," NASA executive William Readdy said after the latest tragedy.
In the weeks and months to come, we will learn much about the investigation into Columbia's fate. We likely will come to know with some certainty whether it was caused by damage to heat-reflecting tiles during liftoff.
The commission which investigated the Challenger disaster included Neil Armstrong, the first man to walk on the moon. It concluded that a faulty O-ring in the right solid-fuel rocket booster was to blame, something roughly akin to the rubber ring that seals a Mason jar. That an object so seemingly mundane could cause such a catastrophe was striking, even humbling. Such missions are, again, anything but routine.
The expensive efforts to explore the skies -- whether through ever-more sophisticated telescopes or through manned and unmanned missions -- can be defended on the grounds of discovery alone. It is the job of every generation to expand what is known. The unknown, by its nature, is infinite.
But with great risks come great benefits. Consider some of the practical inventions made possible in one way or another by the space program: laser eye surgery, thermal insulation, search-and-rescue technology, computer-enhanced imaging, weather-resistant coatings, fire scanners and smoke detectors. The list goes on.
The Columbia astronauts completed dozens of experiments, many designed by Canadian scientists in areas such as bone density and protein crystals. Accompanying the seven into space were carpenter bees, spiders, fish embryos and much else. Some results were transmitted to Earth during the 16-day mission and, as one NASA official said, will remain "a legacy" of the astronauts. Much work was lost in the explosion.
That work will be reprised one day.
The status of the space-shuttle program is unclear, as is the future of astronauts such as Canadians Steve MacLean and Dave Williams, who were to fly this year. Two disasters in the 113 shuttle missions is unacceptable. There is much to examine about the space program, and likely much to change. But as U.S. President George W. Bush said: "Our journey into space will go on."
Those nervy enough to reach for the stars were punished in ancient mythology and religions. God combated an attempt to build a stepped pyramid to heaven by confusing everyone's tongues -- the biblical Tower of Babel. In Greek myth, Daedalus devised wings of wax and feathers, then warned his son not to fly too close to the Sun or the wax would melt. Icarus didn't listen, and plunged into the ocean.
The modern age is about leaning against limits. Space exploration began less than half a century ago, but NASA is marking a centennial this year -- of two brothers who had the "Wright Stuff," as a NASA website for children puts it.
It took years for Wilbur and Orville Wright to invent powered flight by a craft heavier than air. Orville's first flight on Dec. 17, 1903, lasted 12 seconds and covered 37 meters. There would be three more flights that day; the fourth and longest was flown by Wilbur. It lasted 59 seconds and covered more than a quarter-kilometre.
Just 100 years later, a manned mission to Mars is contemplated seriously, and an unmanned mission to Pluto. What once was science fiction is reality.
Tens of thousands of people are expected to gather at Kitty Hawk, N.C., on Dec. 17 to celebrate the Wright brothers' accomplishments. Many of those people will gather at Cape Canaveral when NASA next returns to space. They know, as did the Wright brothers, that there is no turning back.