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1.Can We Know the Universe? - Reflections on a Grain of SaltCarl SaganScience is a way of thinking much more than it is a body of knowledge. Its goal is to find out how the world works, to seek what regularities there may be, to penetrate to the connections of things - from sub-nuclear particles, which may be the constituents of all matter, to living organisms, the human social community, and thence to the cosmos as a whole. Our intuition is by no means an infallible guide. Our perceptions may be distorted by training and prejudice or merely because of the limitations of our sense organs, which, of course, perceive directly but a small fraction of the phenomena of the world.Even so straightforward a question as whether in the absence of friction a pound of lead falls faster than a grain of fluff was answered incorrectly by Aristotle and almost everyone else before the time of Galileo. Science is based on experiment, on a willingness to challenge old dogma, on an openness to see the universe as it really is. Accordingly, science sometimes requires courage-at the very least, the courage to question the conventional wisdom.But to what extent can we really know the universe around us? Sometimes this question is posed by people who hope the answer will be in the negative, who are fearful of a universe in which everything might one day be known. And sometimes we hear pronouncements from scientists who confidently state that everything worth knowing will soon be known - or even is already known.Let us approach a much more modest question: not whether we can know the universe or the Milky Way Galaxy or a star or a world. Can we know ultimately and in detail, a grain of salt? Consider one microgram of table salt, a speck just barely large enough for someone with keen eyesight to make out without a microscope. In that grain of salt there are about 1016 sodium and chlorine atoms. This is a 1 followed by 16 zeros, 10 million billion atoms. If we wish to know a grain of salt, we must know at least the three-dimensional positions of each of these atoms. (In fact, there is much more to be known - for example, the nature of the forces between the atoms - but we are making only a modest calculation.) Now, is this number more or less than the number of things which the brain can know?How much can the brain know? There are perhaps 1011 neurons in the brain, the circuit elements and switches that are responsible in their electrical and chemical activity for the functioning of our minds. A typical brain neuron has perhaps a thousand little wires, called dendrites, which connect it with its fellows. If, as seems likely, every bit of information in the brain corresponds to one of these connections, the total number of things knowable by the brain is no more than 1014, one hundred trillion. But this number is only one percent of the number of atoms in our speck of salt.So in this sense the universe is intractable, astonishingly immune to any human attempt at full knowledge. We cannot on this level understand a grain of salt, much less the universe.But let us look more deeply at our microgram of salt. Salt happens to be a crystal in which, except for defects in the structure of the crystal lattice, the position of every sodium and chlorine atom is predetermined. If we could shrink ourselves into this crystalline world, we could see rank upon rank of atoms in an ordered array, a regularly alternating structure - sodium, chlorine, sodium, chlorine, specifying the sheet of atoms we are standing on and all the sheets above us and below us. An absolutely pure crystal of salt could have the position of every atom specified by something like 10 bits of information. This would not strain the information-carrying capacity of the brain.If the universe had natural laws that governed its behavior to the same degree of regularity that determines a crystal of salt, then, of course, the universe would be knowable.Even if there were many such laws, each of considerable complexity, human beings might have the capacity to understand them all.Even if such knowledge exceeded the information-carrying capacity of the brain, we might store the additional information outside our bodies - in books, for example, or in computer memories - and still, in some sense, know the universe.Human beings are, understandably, highly motivated to find regularities, natural laws. The search for rules, the only possible way to understand such a vast and complex universe, is called science. The universe forces those who live in it to understand it. Those creatures who find everyday experience a muddled jumble of events with no predictability, no regularity, are in grave peril. The universe belongs to those who, at least to some degree, have figured it out.It is an astonishing fact that there are laws of nature, rules that summarize conveniently - not just qualitatively but quantitatively - how the world works. We might imagine a universe in which there are no such laws, in which the 1080 elementary particles that make up a universe like our own behave with utter and uncompromising abandon. To understand such a universe we would need a brain at least as massive as the universe. It seems unlikely that such a universe could have life and intelligence, because beings and brains require some degree of internal stability and order. But even if in a much more random universe there were such beings with an intelligence much greater than our own, there could not be much knowledge, passion or joy.Fortunately for us, we live in a universe that has at least important parts that are knowable. Our common-sense experience and our evolutionary history have prepared us to understand something of the workaday world.When we go into other realms, however, common sense and ordinary intuition turn out to be highly unreliable guides.For myself, I like a universe that includes much that is unknown and, at the same time, much that is knowable. A universe in which everything is known would be static and dull, as boring as the heaven of some weak-minded theologians. A universe that is unknowable is no fit place for a thinking being. The ideal universe for us is one very much like the universe we inhabit. And I would guess that this is not really much of a coincidence.2.Extraterrestrial LifeA. Bowdoin Van RiperWhether life exists anywhere in the universe besides Earth is an open question, one that Western scholars have debated for over 200 years without coming significantly closer to a solution.Proving that extraterrestrial life does not exist is, by definition, impossible.Our galaxy is too large for us to investigate every corner of it where life might have arisen since we last looked, and it is only one galaxy among many.Proving that extraterrestrial life does exist is easy in principle but difficult in practice.The discovery of an alien organism would provide proof, but searching for one would require interstellar travel-something well beyond humans' technological reach.NONINTELLIGENT LIFE IN OUR GALAXYMost of the planets and moons in our solar system appear inhospitable to life as we know it. Jupiter, Saturn, Uranus, and Neptune lack solid surfaces and receive only limited sunlight. Mercury is baked and irradiated by the sun, while Pluto is perpetually dark and frozen. Venus's dense atmosphere creates crushing pressures, intense heat, and corrosive rain at its surface. Few of the solar system's moons, and none of its asteroids, are large enough to hold even a thin atmosphere. The most likely places to search for life in our solar system appear to be Mars and the larger moons of Jupiter and Saturn. Robot spacecraft have photographed Mars, Europa, and Titan from space. Robot landers have explored small portions of the Martian surface. Finding intelligent life on any of the three worlds now seems unlikely. Finding simpler forms of life, if they exist at all, is likely to require systematic observation at close range.The probability that life exists somewhere else in our galaxy is high, simply because the number of stars in our galaxy is so high. Even if only a tiny fraction of stars have planets, even if only a tiny fraction of those planets are suitable for life, even if life only develops on a fraction of those planets, and even if intelligence only evolves on a fraction of the planets with life, there are still likely to be thousands of life-bearing planets in our galaxy. Finding such life will, however, mean finding the planets. Even if interstellar travel was routine, the job would be daunting. It would mean finding one world among thousands, with no evidence of its special status visible at interstellar distances.INTELLIGENT LIFE IN OUR GALAXYIntelligent life, if it exists elsewhere, is likely to be much rarer than nonintelligent life. It may, however, prove easier actually to find. Our own species beams a steady stream of radio and television signals into space and attaches information-laden metal plates to spacecraft headed out of the solar system. The signals are an accidental by-product of broadcasting; the plates are a conscious attempt at communication. Both announce our existence, our level of technological sophistication, and a tiny bit about our culture.It is also possible that a sufficiently intelligent and technologically adept species might find us before we develop the ability to go looking for it. Believers in the extraterrestrial origin of UFOs argue that such encounters have already happened, either in the past or in the present. Most mainstream scientists are skeptical of such beliefs, explaining purported encounters with aliens in more prosaic terms.EXTRATERRESTRIAL LIFE IN POPULAR CULTUREPopular culture depicts thousands of human encounters with extraterrestrial life. Entire subgenres of science fiction are devoted to such encounters: "first contact" stories, "alien invasion" stories, "aliens among us" stories, and so on. A detailed discussion of popular culture's treatment of aliens could easily fill a book. Nearly all stories about extraterrestrial life, however, follow three well-established conventions.First, most stories featuring imagined extraterrestrial life tend to focus on one or, at most, two species from any given world. Gatherings of intelligent aliens from many worlds are common, but fully imagined alien ecosystems are not. The reason for this is both obvious and understandable. Ecosystems are extraordinarily complex. Describing one on Earth, the building blocks of which are familiar, is a significant challenge; creating a plausible alien ecosystem from scratch, using very different building blocks, is an even greater challenge.Second, the physical form of extraterrestrial species reflects human attitudes toward species on Earth. The sweet-natured title character of Stephen Spielberg's film E.T. has a head that is large in proportion to its body and eyes that are large in proportion to its head. It has, in other words, the basic morphology of a human infant. Alien species that invade or attack the earth often resemble creatures that Western culture deems unpleasant. Powerful and benevolent aliens, on the other hand, recall angels in their lack of permanent physical bodies. Their evolution "beyond the need for physical form" is also suggestive of ideas about the afterlife.Third, the personalities and thought patterns of intelligent aliens closely resemble those of humans. Alien invaders of Earth want what human invaders want: territory, resources, slaves, or mates. Alien benefactors of Earth act out of altruism or paternalism or to secure allies in a hostileuniverse. Humans and aliens routinely discover that despite their physical differences, they share many of the same hopes and fears.We know nothing of how extraterrestrial life - if it exists - appears, behaves, or (if intelligent) thinks. Stories about it thus allow for limitless imagination. We tend, nevertheless, to imagine aliens whose appearance reflects our attitudes toward species here on Earth and whose thought and behavior patterns mirror our own. The reason for this is less a failure of imagination than an acknowledgement of dramatic necessity.Stories about human encounters with alien species are, ultimately, stories about us rather than the aliens. The innocent, stranded aliens of films like Escape from the Planet of the Apes and Starman are litmus tests for human society. Good-hearted individuals shelter and aid them, but those in power persecute them; the stories simultaneously reveal the best and worst of human behavior. Stories like these require aliens that are more human than any real alien species is likely to be-aliens that are human enough for human characters to interact with and for human audiences to care about.3.We Are All ScientistsThomas H. HuxleyThe method of scientific investigation is nothing but the expression of the necessary mode of working of the human mind.It is simply the mode at which all phenomena are reasoned about.There is no more difference, between the mental operations of a man of science and those of an ordinary person, than there is between the operations and methods of a baker weighing out his goods in common scales, and the operations of a chemist in performing a difficult and complex analysis by means of his balance and finely graduated weights.It is not that the action of the scales in the one case, and the balance in the other, differ in the principles of their construction or manner of working; but the beam of one is set on an infinitely finer axis than the other, and of course turns by the addition of a much smaller weight.You have all heard it repeated, that men of science work by means of induction and deduction: and that by the help of these operations, they wring from Nature certain other things, which are called natural laws and causes, and that out of these, they build up hypotheses and theories. And it is imagined by many that the operations of the common mind can by no means be compared with these processes, and that they have to be acquired by a sort of special apprenticeship to the craft. To hear all these large words, you would think that the mind of a man of science must be constituted differently from that of his fellow men; but if you will not be frightened by the terms, you will discover that you are quite wrong. Probably there is not one here who has not in the course of the day had occasion to set in motion a complex train of reasoning, of the very same kind, thoughdiffering of course in degree, as that which a scientific man goes through in tracing the causes of natural phenomena.A very trivial circumstance will serve to exemplify this. Suppose you go into a fruiter's shop, wanting an apple--you take up one, and, on biting it, you find it is sour; you look at it, and see that it is hard and green. You take up another one, and that too is hard, green, and sour. The shop man offers you a third; but, before biting it, you find it is hard and green, and you immediately say that you will not have it, as it must be sour.Nothing can be simpler than that, but if you take the trouble to analyze and trace out into its logical elements what has been done by the mind, you will be greatly surprised. You found that, in the two experiences, hardness and greenness in apples went together with sourness. When you are offered another apple which is hard and green, you say: "All hard and green apples are sour; this apple is hard and green, therefore it is sour." You see, you have, in the first place, established a law by induction, and upon that you have founded a deduction, and reasoned out the special conclusion of the particular case. Now, suppose, someday, you are questioned by a friend: "But how do you know that all hard and green apples are sour?" You at once reply, "Oh, because I have tried them over and over again, and have always found them to be so." Well, if we were talking science instead of common sense, we should call that an experimental verification. The more extensive verifications are, the more frequently experiments have been made, and results of the same kind arrived at, and the more varied the conditions under which the same results are attained, the more certain is the ultimate conclusion. And in science, as in common life, our confidence in a law is in exact proportion to the absence of variation in the result of our experimental verifications. We believe gravitation in such an extensive, thorough, and unhesitating manner because the universal experience of mankind verifies it, and we can verify it ourselves at any time; and that is the strongest possible foundation on which any natural law can rest.Let us now take another example.Suppose that on coming down to the parlor of your house, you find that a teapot and some spoons which had been left in the room are gone--the window is open, and you observe the mark of a dirty hand on the window frame, and you notice the impress of a hobnailed shoe on the gravel outside. All these phenomena have struck your attention instantly, and before two seconds have passed you say, "Oh, somebody has broken open the window, entered the room, and run off with the spoons and the teapot!" You mean to say exactly what you know; but in reality you are giving a hypothesis. You do not know it at all; it is nothing but a hypothesis rapidly framed in your own mind. By a train of reasoning involving many inductions and deductions, you have probably arrived at the general law that the windows do not open by themselves. Something has opened the window. Asecond general law you have arrived at is that teapots and spoons do not go out of a window spontaneously. They have been removed. In the third place, you look at the marks on the windowsill and the shoe-marks outside, and you conclude that they are made by a man. You assume from all these premises that the man who made the marks outside and on the window sill, opened the window, got into the room, and stole your teapot and spoons.Now, in this supposition case, I have taken phenomena of a very common kind, in order that you might see what are the different steps in an ordinary process of reasoning. I say that you are led to your conclusion by exactly the same train of reasoning as that which a man of science pursues when he is endeavoring to discover the origin and laws of the most occult phenomena. The only difference is that the nature of the inquiry being more abstruse, every step has to be most carefully watched, so that there may not be a single crack or flaw in his hypothesis. A flaw or crack in many of the hypotheses of daily life may be of little or no moment; but, in a scientific inquiry, a fallacy, great or small, is always of importance, and is sure to be in the long run constantly productive of mischievous, if not fatal results.puter AddictsDina IngberIt is 3 A.M. Everything on the university campus seems ghostlike in the quiet, misty darkness--everything except the computer center. Here, twenty students sit transfixed at their consoles, tapping away on the terminal keys. For the rest of the world, it might be the middle of the night, but here time does not exist. As in the gambling casinos of Las Vegas, there are no windows or clocks. This is a world unto itself. Like gamblers, these young computer "hackers" are pursuing a kind of compulsion, a drive so consuming it overshadows nearly every other part of their lives and forms the focal point of their existence. They are compulsive computer programmers.What do they do at the computer at all hours of the day or night? They design and play complex games; they delve into the computer's memory bank for obscure tidbits of information; like ham radio operators, they communicate with hackers in other areas who are plugged into the same system. They even do their everyday chores by computer, typing term papers and getting neat printouts. By breaking the code, they can cut into other programs, discovering secrets in computerized systems or making mischievous (and often costly) changes to other people's programs.Computer-science teachers are now more aware of the implications of this hacker phenomenon and are on the lookout for potential hackers and cases of computer addiction that are already severe. They know that the case of the hackers is not just the story of one person's relationship with a machine. It is the story of a society's relationship to the so-called thinking machines, which are becoming almost ubiquitous.Many feel we are now on the verge of a computer revolution that will change our lives as drastically as the invention of the printing press and the Industrial Revolution changed society in the past. By the most conservative estimates, one out of three American homes will have computers or terminals within the next five to ten years. Electronic toys and games, which came on the market in 1976, already comprise a more than half-billion-dollar business. And though 300,000 Americans now work full time programming computers, at least another 1.2 million will be needed by 1990. Many of them are likely to come from today's young hackers.There is a strong camaraderie and sense of belonging among hackers. They have their own subculture, with the usual in jokes and even a whole vocabulary based on computer terminology (there is even a hacker's dictionary). But to outsiders, they are a strange breed. In high schools, the hackers are called nerds or the brain trust. They spend most of their free time in the computer room and don't socialize much. And many have trouble with interpersonal relationships.Joel Bion, a sophomore at Stanford, explains how he got hooked: "I've been working with computers since I was eight. I grew up in Minnesota and I didn't have many friends. I wasn't into sports and couldn't participate in gym class because I had asthma. Then I found a computer terminal at school. I bought some books and taught myself. Pretty soon I was spending a few hours on it every day. Then I was there during vacations. Sure, I lost some friends, but when I first started I was so fascinated. Here was a field I could really feel superior in. I had a giant program, and I kept adding and adding to it. And I could use the computer to talk to people all over the state, I thought that was a great social interaction. But, of course, it wasn't, because I never came into face-to-face contact."Interesting and malleable are the two key words if you want to understand the hacker's addiction and the increasing allure of the computer for all segments of our society.The computer can be almost as interesting as a human being. Like people, it is interactive. When you ask it a question, it gives you an answer. And because it stores great quantities of information, it can often answer more questions, more accurately, than human friends. This interaction has led some to attribute human characteristics to the machine.Hackers are not the only ones interacting with the computer on a personal level. The amazing powers of the machine have enticed even the most sophisticated scientists into wondering just how human it can become. The newly developing science of artificial intelligence aims at programming the computer to think, reason and react in much the same way that people do. Computers can diagnose a patient's ailments and recommend treatments. They can mimic the dialogue of a psychotherapist or the reasoning of a lawyer.If computers can replace our most admired humans, the professionals, then why shouldn't the hackers feel close to them and invest emotional energy in them? After all, the computer seems to have unlimited potential. Already, with today's technology, tens of thousands of words can be stored on a tiny silicon chip measuring less than a centimeter square and millimeter thick. And any item of information on the chip can be called up and displayed on a TV screen in a fraction of a second. So the computer user has access to worlds of information within reach, literally, of his fingertips. And the computer can rearrange that information and interrelate facts or draw conclusions at the programmer's command. It is extremely malleable.Computer-science teachers say they can usually pick out the prospective hackers in their courses because these students make their homework assignments more complex than they need to be. Rather than using the simplest and most direct method, they take joy in adding extra steps just to prove their ingenuity.But perhaps those hackers know something that we don't about the shape of things to come. "That hacker who had to be literally dragged off his chair at MIT is now a multimillionaire of the computer industry," says MIT professor Michael Dertouzos. "And two former hackers became the founders of the highly successful Apple home-computer company."When seen in this light, the hacker phenomenon may not be so strange after all. If, as many psychiatrists say, play is really the basis for all human activity, then the hacker games are really the preparation for future developments.Computers are not just becoming more and more a part of our world. To a great degree they are our world. It is therefore not unlikely that our relationship with them will become as subjective as that of the hackers. So perhaps hackers are, after all, harbingers of the world to come.5.Why Superstitions?Peter LorieEvery age pays attention to the ancient superstitions according to a certain subtle fashion, very often knowing nothing about the original sources from which they derived. It wasn't so long ago that bibles were fanned in front of sick men's faces and communion wine was prescribed for whooping cough while women bathed their sore eyes with baptismal water. Although modem Westerners would not admit to crossing themselves when faced with potential evil such as a passing magpie, they do cross fingers to prevent bad luck. Some superstitions merely transform from the original, and the original is frequently a relic of still more ancient cultures and long-vanished ways of life. Above all, superstitions remain as outward expressions of the tensions and anxieties that hold sway over humanity as itstruggles down the corridor of life from birth to death, full of change and uncertainty.We can see the superstition, therefore, as a kind of reassurance against fluctuation as though we are part of an impenetrable mystery with incomprehensible rules.And yet - strangely perhaps in this age of reason - it very often turns out that we are more interested in the mysteries of superstitions than in previous centuries when they were taken for granted, and that in fact there is much more to many superstitions than is at first obvious. Mistletoe, for example, was the most holy of plants to the Druids, why so? To hang a sprig of this strange plant in a house at Christmas is to attract young men to kiss young women beneath it, each time plucking one of the berries from the sprig. Why should this be so? Who started it? Why did the hanging of mistletoe keep away the devil? The young woman to whom the man had given the plucked berry would retire to her room, lock the door and swallow the berry. She would then inscribe the initials of the man onto a mistletoe leaf and "stitch it into her corset close to her heart, binding him to her so long as it remain there."Superstitious nonsense! But how do we maintain the best love affairs, the best and most happy relationships? By mutual concern, by bringing the partner close to an open heart, by honesty and warmth, by acknowledging their presence in our lives. How better to represent this than with a mistletoe leaf inscribed and secreted in the most intimate place?All superstition has grown from something; there is no smoke without fire. Who was the first one to decide that opening an umbrella in a house is bad luck? Who was the first to walk under a ladder and suffer the consequences? Who smashed a mirror, and spilled salt to spend a life-sentence at the hands of the fates? Who first branded Friday the 13th as a day on which luck would run out? What was the world like that produced and maintained such extraordinary ideas?The bulk of the population, aside perhaps from the aristocratic classes, was concerned largely with the search for or production of food; therefore the changes of the seasons, the success or failure of the crops and all the influences that nature had upon life. The greater part of the populations of Europe lived in rural areas in small isolated communities. The difference between rich and poor was marked, and 99 percent of the people were very poor. Even as late as seventeenth century England, around two-thirds of the adult male population were unable to read and would sign their names with an "X."Life was extremely hazardous, and the central feature of day-to-day existence was a preoccupation with the explanation for and relief of human misfortune. In seventeenth-century Europe, for example, life-expectancy was influenced by the constant presence of sickness and premature death.。