Eugene F. Mallove and Gregory L. Matloff, The Starflight Handbook (New York: John Wiley and Sons, 1989).
Carl Sagan and Ann Druyan, Comet (New York: Random House, 1985).
FOOTNOTES
1 "As to the fable that there are Antipodes," wrote St. Augustine in the fifth century, "that is to say, men on the opposite side of the earth, where the sun rises when it sets to us, men who walk with their feet opposite ours, that is on I'll ground credible." Even if some unknown landmass is there, and not just ocean, "there was only one pair of original ancestors, and it is inconceivable that such distant regions should have been peopled by Adam's descendants.''
1 Copernicus' famous book was first published with an introduction by the theologian Andrew Osiander, inserted without the knowledge of the dying astronomer. Osiander's well-meaning attempt to reconcile religion and Copernican astronomy ended with these words: "[L]et no one expect anything in the way of certainty of astronomy, since astronomy can offer us nothing certain, lest, if anyone take as true that which has been constructed for .mother use, he go away from this discipline a bigger fool than w hen he cane to it." Certainty could be found only in religion.
1 St. Augustine, in The City of God, says, "As it is not yet six thousand years since the first man . . . are not those to be ridiculed rather than refuted who try to persuade us of anything regarding a space of time so different from, and contrary to, the ascertained truth? . . . We, being sustained by divine authority in the history of our religion, have no doubt that whatever is opposed to it is most false." He excoriates the ancient Egyptian tradition that the world is at much as a hundred thousand years old as "abominable lies." St. Thomas Aquinas, in the Summa Theologica, flatly states that "the newness of the world cannot be demonstrated from the world itself." They were so sure.
1 Our universe is almost incompatible with life—or at least what we understand as necessary for life: Even if every star in a hundred billion galaxies had an Earthlike planet, without heroic technological measures life could prosper in only about 10-37 the volume of the Universe. For clarity, let's write it out: only 0.000 000 000 000 000 000 000 000 000 000 000 000 1 of our universe is hospitable to life. Thirty-six zeroes before the one. The rest is cold, radiation-riddled black vacuum.
1 For such ideas, words tend to fail us. A German locution for Universe is [dad 911which makes the inclusiveness quite unmistakable. We might say that our universe is but one in a "Multiverse," but I prefer to use "Cosmos" for everything and "Universe" for the only one we can know about.
1 One of the few quasi-Copernican expressions in English is "The Universe doesn't revolve around you"-an astronomical truth intended to bring fledgling narcissists down to Earth.
1 Since women astronauts and cosmonauts of several nations have flown in space, "manned" is just flat-out incorrect. I've attempted to find an alternative to this widely used term, coined in a more unselfconsciously sexist age. I tried "crewed" for a while, but in spoken language it lends itself to misunderstanding. "Piloted" doesn't work, because even commercial airplanes have robot pilots. "Manned and womanned" is just, but unwieldy. Perhaps the best compromise is "human," which permits us to distinguish crisply between human and robotic missions. But every now and then, 1 find "human" not quite working, and to my dismay "manned" slips back in.
1 There could have been none. We're very lucky that there is such a world study. The others ill have too much hydrogen, or not enough, or no atmosphere at all.
1 Not because he thought it remarkably large. but because in Greek mythology members of the generation preceding the Olympian gods—Saturn, his siblings, and his cousins—were called Titans.
2 Titan's atmosphere has no detectable oxygen, so methane is not wildly out of chemical equilibrium—as it is on Earth—and its presence is in no way a sign of life
1 There was one moment in the last 4,000 years when all seven of these celestial bodies were clustered tightly together. Just before dawn on March 4, 1953 B.C., the crescent Moon was at the horizon. Venus, Mercury, Mars, Saturn, and Jupiter were strung out like jewels on a necklace near the great square in the constellation Pegasus—near the spot from which in our time the Perseid meteor shower emanates. Even casual watchers of the sky must have been transfixed by the event. What was it—a communion of the gods? According to the astronomer David Pankenier of Lehigh University and later Kevin Pang of JPL, this event was the starting point for the planetary cycles of the ancient Chinese astronomers. There is no other time in the last 4,000 years (or in the next) when the dance of the planets around the Sun brings them so close together from the vantage point of Earth. But on May 5, 2000, all seven will be visible in the same part of the sky—although some at dawn and some at dusk and about ten times more spread out than on that late winter morning in 1953 B.C. Still, it's Probably a good night for a party.
1 After whom the European-American mission to the Saturn system is named.
1 He so named it because of the words spoken by Miranda, the heroine of The Tempest: "O brave new world, That has such people in't." (To Which Prospero replies, "'Tis new to thee." Just so. Like all the other worlds in the Solar System, Miranda is about 4.5 billion years old.)
1 It takes so long to circuit the Sun because its orbit is so vast, 23 billion miles around, and because the force of the Sun's gravity—which keeps it from flying out into interstellar space—is at that distant comparatively feeble, less than a thousandth what it is in the Earth's vicinity.
2 Robert Goddard, the inventor of the modern liquid-fueled rocket, envisioned a time when expeditions to the stars would be outfitted on and launched from Triton. This was in a 1927 afterthought to a 1918 handwritten manuscript called "The Last Migration." Considered much too daring for publication, it was deposited in a friend's safe. The cover page bears a warning: "The[se] notes should be read thoroughly only by an optimist."
1 The Earth, by definition, is 1 AU from its star, the Sun.
1 Radio signals that both Voyagers detected in 1992 are thought to arise from the collision of powerful gusts of solar wind with the thin gas that lies between the stars. From the immense .power of the signal (over 10 trillion watts), the distance to the heliopause can be estimated: about 100 times the Earth's distance from the Sun. At the speed it's leaving the Solar System, Voyager 1 might pierce the heliopause and enter interstellar space around the year 2010. If its radioactive power source is still working, news of the crossing will be radioed back to the stay-at-homes on Earth. The energy released by the collision of this shock wave with the heliopause makes it the most powerful source of radio emission in the Solar System. It makes you wonder whether even stronger shocks in other planetary systems might he detectable by our radio telescope.
1 Like "gosh-darned" and "geez," this phrase was originally a euphemism for those who considered Sacre-Dieu!, "Sacred God!," too strong an oath, the Second Commandment duly considered, to be uttered aloud.
1 For Titan, imaging revealed a succession of detached hazes above the main layer of aerosols. So Venus works out to be the only world in the Solar System for which spacecraft cameras working in ordinary visible light haven't discovered something important. Happily, we've now returned pictures from almost every world we've visited. (NASA's International Cometary Explorer, which raced through the tail of Comet Giacobini-Zimmer in 1985, flew blind, be devoted to charged particles and magnetic fields.)
2 Today many telescopic images are obtained with such electronic contrivances as charge-coupled devices and diode arrays, and processed by computer—all technologies unavailable to astronomers in 1970.
1 James B. Pollack made important contributions to every area of planetary science. He was my first graduate student and a colleague ever since. He converted NASA's Ames Research Center into a world leader in planetary research and the post-doctoral training of planetary scien
tists. His gentleness was as extraordinary as his scientific abilities. He died in 1994 at the height of his powers.
1 The eruption of a nearby submarine volcano and the rapid construction Of' new island in 197 B.C. are described by Strabo in the epigraph to this chapter.
1 Even with its mountains and submarine trenches, our planet is astonishingly smooth. If the Earth were the size of a billiard ball, the largest protuberances would be less than a tenth of a millimeter in size—on the threshold of being too small to see or feel.
1 The age of the Venus surface, as determined by Magellan radar imagery, puts an additional nail in the coffin of the thesis of Immanuel Velikovsky—who around 1950 proposed, to surprising media acclaim, that 3,500 years ago Jupiter spat out a giant "comet" which made several grazing collisions with the Earth, causing various events chronicled in the ancient books of many peoples (such as the Sun standing still on Joshua's command), and then transformed itself into the planet Venus. There ire still people N% ho take these notions seriously.
1 Io's volcanos are also the copious source of electrically charged atoms such as oxygen and sulfur that populate a ghostly, doughnut-shaped tube of matter that surrounds Jupiter.
1 Although in a few places, such as the slopes of the elevation called Alba Patera, there are multibranched valley networks that by comparison are very young. Somehow, even in the most recent billion years, liquid water seems to have flowed here and there, from time to time, through the deserts of Mars.
2 Short for Shergotty-Nakhla-Chassigny. You can see why the acronym is used.
1 Even then it wasn't easy. The Portuguese chronicler Gomes Eanes de Zurara reported this assessment by Prince Henry the Navigator: "It seemed to the Lord Infante that if he or some other lord did not endeavor to gain that knowledge, no mariners nor merchants would ever dare to attempt it, for it is clear that none of them ever trouble themselves to sail to a place where there is not a sure and certain hope of profit."
1 Russell's phrase is noteworthy: "adventurous and hazardous glory." Even if we could make human spaceflight risk-free-and of course we cannot-it might be counterproductive. The hazard is an inseparable component of the glory.
1 If it had not, perhaps there would today be another planet, a little nearer to or farther from the Sun, on which other, quite different beings would be trying to reconstruct their origins.
1 Asteroid 1991JW has an orbit very much like the Earth's and is even easier to get to than 4660 Nereus. But its orbit seems too similar to the Earth's for it to be a natural object. Perhaps it's some lost upper stage of the Saturn V Apollo Moon rocket.
1 The Outer Space Treaty, adhered to both by the United States and Russia, prohibits weapons of mass destruction in "outer space." Asteroid deflection technology constitutes just such a weapon—indeed, the most powerful weapon of mass destruction ever devised. Those interested in developing asteroid deflection technology will want to have the treaty revised. But even with no revision, were a large asteroid to be discovered on impact trajectory with the Earth, presumably no one's hand would be stayed by the niceties of international diplomacy. There is a danger, though, that relaxing prohibitions on such weapons in space might make us less attentive .bout the positioning of warheads for offensive purposes in space.
1 What should we call this world? Naming it after the Greek Fates or Furies or Nemesis seems inappropriate, because whether it misses or hits the Earth is entirely in our hands. If we leave it alone, it misses. If we push it cleverly and precisely, it hits. Maybe we should call it "Eight Ball."
1 There is of course a wide range of other problems brought on by the devastatingly powerful technology we've recently invented. But in most cases they're not Camarinan disasters-damned if you do and damned if you don't. Instead they're dilemmas of wisdom or timing-for example, the wrong refrigerant or refrigeration physics out of many possible alternatives.
1 In the real world, Chinese space officials are proposing to send a two-person astronaut capsule into orbit by the turn of the century. It would be propelled by a modified Long March 2E rocket and be launched from the Gobi Desert. If the Chinese economy exhibits even moderate continuing growth—much less the exponential growth that marked it in the early to mid-1990s—China may be one of the world's leading space powers by the middle of the twenty-first century. Or earlier.
1 If it had been the other way, then we and everything else in this part of the Universe would be made of anti-matter. We would, of course, call it matter—and the idea of worlds and life made of that other kind of material. the stuff with the electrical charges reversed, we'd consider wildly speculative.
1 Williamson, Professor Emeritus of English at Eastern New Mexico University at age 85 wrote to me that he was "amazed to see how far actual science has come" since he first suggested terraforming other worlds. We are accumulating the technology that will one day permit terraforming, but at present all 'V-a have are suggestions by and large less ground breaking than Williamson's original ideas.
1 Surprisingly many people, including New York Times editorialists, are concerned that once extraterrestrials know where we are, they will come here and eat us. Put aside the profound biological differences that must exist between the hypothetical aliens and ourselves; imagine that we constitute an interstellar gastronomic delicacy. Why transport large numbers of us to alien restaurants? The freightage is enormous. Wouldn't it be better just to steal a few humans, sequence our amino acids or whatever else is the source of our delectability, and then just synthesize the identical food product from scratch?
1 Might a planetary civilization which has survived its adolescence wish to encourage others struggling with their emerging technologies? Perhaps they would make special efforts to broadcast news of their existence, the triumphant announcement that it's possible to avoid self-annihilation. Or would they at first be very cautious? Having avoided catastrophes of their own making, perhaps they would fear giving away knowledge of their existence, lest some other, unknown, aggrandizing civilization out there in the dark is looking for Lebensraum or slavering to put down the potential competition. That might be a reason for us to explore neighboring star systems, but discreetly.
Maybe they would be silent for another reason: because broadcasting the existence of an advanced civilization might encourage emerging civilizations to do less than their best efforts to safeguard their future— hoping instead that someone will come out of the dark and save them from themselves.
1 Cf. Shadows of Forgotten Ancestors: A Search for Who We Are, by Carl Sagan and Ann Druyan (New York: Random House, 1992).
1 Even if we are not in any particular hurry, we may be able by then to make small worlds move faster than we can make spacecraft move today. If so, our descendants will eventually overtake the two Voyager spacecraft—launched in the remote twentieth century—before they leave the Oort Cloud, before they make for interstellar space. Perhaps they will retrieve these derelict ships of long ago. Or perhaps they will permit them to sail on.
1 A value that nicely approximates modern estimates of the number of planets orbiting stars in the Milky Way Galaxy.
2 Most of it may be in "nonbaryonic" matter, not made of our familiar protons and neutrons, and not anti-matter either. Over 90 percent of the mass of the Universe seems to be in this dark, quintessential, deeply mysterious stuff wholly unknown on Earth. Perhaps we will one day not only understand it, but also find a use for it.
Carl Sagan, Pale Blue Dot
(Series: # )
Thank you for reading books on BookFrom.Net Share this book with friends