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Cosmos carl sagan english pdf

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Where can i download Cosmos by Carl Sagan totally free ebook pdf kindle urdu, French and English, german born and Australian dialects. Cosmos is a popular science book by astronomer and Pulitzer Prize- winning author Carl . David Whitehouse of the British Broadcasting Corporation went so far as to say . "This View of Science: Stephen Jay Gould as Historian of Science and Scientific Historian, Popular Scientist and Scientific Popularizer" ( PDF). In , Carl Sagan published The Cosmic Connection, a daring view A catalogue record for this publication is available from the British Library. Library of.


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Carl Sagan Cosmos Pdf previous post Calculus Of Variations & Optimal Control Sasane Pdf. next post Carbon Nanotubes Pdf. Back to top. CARL SAGAN Cosmos CONTENTS Introduction 1 The Shores of the Cosmic . Foundation, the British Broadcasting Corporation, and Polytel International. Carl Edward Sagan was a founder of the modern disci- plines of . Sagan's first major trade book, Cosmic Connection: An Extraterrestrial Perspective ().

Paperback —. Carl Sagan. Print Culture. Man excelled in launching Voyager space probes but failed in the nuclear build up of the Cold War which was still in full force while this book was being written. Error rating book.

This was another, and very well-functioning, kind of creature with much more prominent wings and long feathery antennae. Fate had arranged, I concluded, that an example of a major evolutionary change in a single generation, the very thing Muller had said could never happen, should take place in his own laboratory.

It was my unhappy task to explain it to him. With heavy heart I knocked on his office door. I entered to discover the room darkened except for a single small lamp illuminating the stage of the microscope at which he was working. In these gloomy surroundings I stumbled through my explanation. I had found a very different kind of fly.

I was sure it had emerged from one of the pupae in the molasses. Does it have feathery antennae? Muller switched on the overhead light and smiled benignly. It was an old story. There was a kind of moth that had adapted to Drosphila genetics laboratories. It was nothing like a fruit fly and wanted nothing to do with fruit flies.

In the brief time that the laboratory technician took to unstopper and stopper the milk bottle - for example, to add fruit flies - the mother moth made a dive-bombing pass, dropping her eggs on the run into the tasty molasses. I had not discovered a macro-mutation. I had merely stumbled upon another lovely adaptation in nature, itself the product of micromutation and natural selection. The secrets of evolution are death and time - the deaths of enormous numbers of lifeforms that were imperfectly adapted to the environment; and time for a long succession of small mutations that were by accident adaptive, time for the slow accumulation of patterns of favorable mutations.

Part of the resistance to Darwin and Wallace derives from our difficulty in imagining the passage of the millennia, much less the aeons. What does seventy million years mean to beings who live only one-millionth as long?

We are like butterflies who flutter for a day and think it is forever. What happened here on Earth may be more or less typical of the evolution of life on many worlds; but in such details as the chemistry of proteins or the neurology of brains, the story of life on Earth may be unique in all the Milky Way Galaxy.

The Earth condensed out of interstellar gas and dust some 4. We know from the fossil record that the origin of life happened soon after, perhaps around 4. The first living things were not anything so complex as a one-celled organism, already a highly sophisticated form of life.

The first stirrings were much more humble. In those early days, lightning and ultraviolet light from the Sun were breaking apart the simple hydrogen-rich molecules of the primitive atmosphere, the fragments spontaneously recombining into more and more complex molecules. The products of this early chemistry were dissolved in the oceans, forming a kind of organic soup of gradually increasing complexity, until one day, quite by accident, a molecule arose that was able to make crude copies of itself, using as building blocks other molecules in the soup.

We will return to this subject later. This was the earliest ancestor of deoxyribonucleic acid, DNA, the master molecule of life on Earth. It is shaped like a ladder twisted into a helix, the rungs available in four different molecular parts, which constitute the four letters of the genetic code.

These rungs, called nucleotides, spell out the hereditary instructions for making a given organism. Every lifeform on Earth has a different set of instructions, written out in essentially the same language.

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The reason organisms are different is the differences in their nucleic acid instructions. A mutation is a change in a nucleotide, copied in the next generation, which breeds true. Since mutations are random nucleotide changes, most of them are harmful or lethal, coding into existence nonfunctional enzymes. It is a long wait before a mutation makes an organism work better.

And yet it is that improbable event, a small beneficial mutation in a nucleotide a ten-millionth of a centimeter across, that makes evolution go. Four billion years ago, the Earth was a molecular Garden of Eden. There were as yet no predators. Some molecules reproduced themselves inefficiently, competed for building blocks and left crude copies of themselves.

With reproduction, mutation and the selective elimination of the least efficient varieties, evolution was well under way, even at the molecular level. As time went on, they got better at reproducing. Molecules with specialized functions eventually joined together, making a kind of molecular collective - the first cell.

Plant cells today have tiny molecular factories, called chloroplasts, which are in charge of photosynthesis - the conversion of sunlight, water and carbon dioxide into carbohydrates and oxygen. The cells in a drop of blood contain a different sort of molecular factory, the mitochondrion, which combines food with oxygen to extract useful energy.

These factories exist in plant and animal cells today but may once themselves have been free-living cells. By three billion years ago, a number of one-celled plants had joined together, perhaps because a mutation prevented a single cell from separating after splitting in two.

The first multicellular organisms had evolved. Every cell of your body is a kind of commune, with once free-living parts all banded together for the common good. And you are made of a hundred trillion cells. We are, each of us, a multitude.

Sex seems to have been invented around two billion years ago. Before then, new varieties of organisms could arise only from the accumulation of random mutations - the selection of changes, letter by letter, in the genetic instructions. Evolution must have been agonizingly slow. With the invention of sex, two organisms could exchange whole paragraphs, pages and books of their DNA code, producing new varieties ready for the sieve of selection.

Organisms are selected to engage in sex - the ones that find it uninteresting quickly become extinct. And this is true not only of the microbes of two billion years ago.

We humans also have a palpable devotion to exchanging segments of DNA today. By one billion years ago, plants, working cooperatively, had made a stunning change in the environment of the Earth. Green plants generate molecular oxygen. But oxygen tends to make organic molecules fall to pieces. Despite our fondness for it, it is fundamentally a poison for unprotected organic matter. The transition to an oxidizing atmosphere posed a supreme crisis in the history of life, and a great many organisms, unable to cope with oxygen, perished.

A few primitive forms, such as the botulism and tetanus bacilli, manage to survive even today only in oxygen-free environments. But it, too, is biologically sustained. The sky is made by life. For most of the four billion years since the origin of life, the dominant organisms were microscopic blue-green algae, which covered and filled the oceans.

Then some million years ago, the monopolizing grip of the algae was broken and an enormous proliferation of new lifeforms emerged, an event called the Cambrian explosion.

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Life had arisen almost immediately after the origin of the Earth, which suggests that life may be an inevitable chemical process on an Earth-like planet.

But life did not evolve much beyond blue-green algae for three billion years, which suggests that large lifeforms with specialized organs are hard to evolve, harder even than the origin of life. Perhaps there are many other planets that today have abundant microbes but no big beasts and vegetables. Soon after the Cambrian explosion, the oceans teemed with many different forms of life.

By million years ago there were vast herds of trilobites, beautifully constructed animals, a little like large insects; some hunted in packs on the ocean floor. They stored crystals in their eyes to detect polarized light. But there are no trilobites alive today; there have been none for million years. The Earth used to be inhabited by plants and animals of which there is today no living trace.

And of course every species now on the planet once did not exist. There is no hint in the old rocks of animals like us. Species appear, abide more or less briefly and then flicker out. Before the Cambrian explosion species seem to have succeeded one another rather slowly. In part this may be because the richness of our information declines rapidly the farther into the past we peer; in the early history of our planet, few organisms had hard parts and soft beings leave few fossil remains.

But in part the sluggish rate of appearance of dramatically new forms before the Cambrian explosion is real; the painstaking evolution of cell structure and biochemistry is not immediately reflected in the external forms revealed by the fossil record.

After the Cambrian explosion, exquisite new adaptations followed one another with comparatively breathtaking speed. In rapid succession, the first fish and the first vertebrates appeared; plants, previously restricted to the oceans, began the colonization of the land; the first insect evolved, and its descendants became the pioneers in the colonization of the land by animals; winged insects arose together with the amphibians, creatures something like the lungfish, able to survive both on land and in the water; the first trees and the first reptiles appeared; the dinosaurs evolved; the mammals emerged, and then the first birds; the first flowers appeared; the dinosaurs became extinct; the earliest cetaceans, ancestors to the dolphins and whales, arose and in the same period the primates - the ancestors of the monkeys, the apes and the humans.

Less than ten million years ago, the first creatures who closely resembled human beings evolved, accompanied by a spectacular increase in brain size.

And then, only a few million years ago, the first true humans emerged. Human beings grew up in forests; we have a natural affinity for them. How lovely a tree is, straining toward the sky. Its leaves harvest sunlight to photosynthesize, so trees compete by shadowing their neighbors. If you look closely you can often see two trees pushing and shoving with languid grace. Trees are great and beautiful machines, powered by sunlight, taking in water from the ground and carbon dioxide from the air, converting these materials into food for their use and ours.

The plant uses the carbohydrates it makes as an energy source to go about its planty business. And we animals, who are ultimately parasites on the plants, steal the carbohydrates so we can go about our business. In eating the plants we combine the carbohydrates with oxygen dissolved in our blood because of our penchant for breathing air, and so extract the energy that makes us go. In the process we exhale carbon dioxide, which the plants then recycle to make more carbohydrates.

There are tens of billions of known kinds of organic molecules. Yet only about fifty of them are used for the essential activities of life. The same patterns are employed over and over again, conservatively, ingeniously for different functions. And at the very heart of life on Earth the proteins that control cell chemistry, and the nucleic acids that carry the hereditary instructions - we find these molecules to be essentially identical in all the plants and animals.

An oak tree and I are made of the same stuff. If you go far enough back, we have a common ancestor. The living cell is a regime as complex and beautiful as the realm of the galaxies and the stars.

The elaborate machinery of the cell has been painstakingly evolved over four billion years. Fragments of food are transmogrified into cellular machinery. How does the cell do it? Inside is a labyrinthine and subtle architecture that maintains its own structure, transforms molecules, stores energy and prepares for self-replication.

If we could enter a cell, many of the molecular specks we would see would be protein molecules, some in frenzied activity, others merely waiting. Enzymes are like assembly-line workers, each specializing in a particular molecular job: Step 4 in the construction of the nucleotide guanosine phosphate, say, or Step 1 1 in the dismantling of a molecule of sugar to extract energy, the currency that pays for getting the other cellular jobs done.

But the enzymes do not run the show. They receive their instructions - and are in fact themselves constructed - on orders sent from those in charge. The boss molecules are the nucleic acids. They live sequestered in a forbidden city in the deep interior, in the nucleus of the cell. If we plunged through a pore into the nucleus of the cell, we would find something that resembles an explosion in a spaghetti factory - a disorderly multitude of coils and strands, which are the two kinds of nucleic acids: These are the best that four billion years of evolution could produce, containing the full complement of information on how to make a cell, a tree or a human work.

The amount of information in human DNA, if written out in ordinary language, would occupy a hundred thick volumes. What is more, the DNA molecules know how to make, with only very rare exceptions, identical copies of themselves. They know extraordinarily much. It is the sequence or ordering of the nucleotides along either of the constituent strands that is the language of life.

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During reproduction, the helices separate, assisted by a special unwinding protein, each synthesizing an identical copy of the other from nucleotide building blocks floating about nearby in the viscous liquid of the cell nucleus. Once the unwinding is underway, a remarkable enzyme called DNA polymerase helps ensure that the copying works almost perfectly.

If a mistake is made, there are enzymes which snip the mistake out and replace the wrong nucleotide by the right one. These enzymes are a molecular machine with awesome powers. In addition to making accurate copies of itself - which is what heredity is about - nuclear DNA directs the activities of the cell - which is what metabolism is about - by synthesizing another nucleic acid called messenger RNA, each of which passes to the extranuclear provinces and there controls the construction, at the right time, in the right place, of one enzyme.

When all is done, a single enzyme molecule has been produced, which then goes about ordering one particular aspect of the chemistry of the cell. Human DNA is a ladder a billion nucleotides long. Most possible combinations of nucleotides are nonsense: Only an extremely limited number of nucleic acid molecules are any good for lifeforms as complicated as we. Even so, the number of useful ways of putting nucleic acids together is stupefyingly large - probably far greater than the total number of electrons and protons in the universe.

Accordingly, the number of possible individual human beings is vastly greater than the number that have ever lived: There must be ways of putting nucleic acids together that will function far better - by any criterion we choose - than any human being who has ever lived. Fortunately, we do not yet know how to assemble alternative sequences of nucleotides to make alternative kinds of human beings.

In the future we may well be able to assemble nucleotides in any desired sequence, to produce whatever characteristics we think desirable - a sobering and disquieting prospect.

Evolution works through mutation and selection. Mutations might occur during replication if the enzyme DNA polymerase makes a mistake. But it rarely makes a mistake. Mutations also occur because of radioactivity or ultraviolet light from the Sun or cosmic rays or chemicals in the environment, all of which can change the nucleotides or tie the nucleic acids up in knots.

If the mutation rate is too high, we lose the inheritance of four billion years of painstaking evolution. If it is too low, new varieties will not be available to adapt to some future change in the environment. The evolution of life requires a more or less precise balance between mutation and selection.

When that balance is achieved, remarkable adaptations occur. The red blood cells of people of European descent look roughly globular.

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The red blood cells of some people of African descent look like sickles or crescent moons. Sickle cells carry less oxygen and consequently transmit a kind of anemia. They also provide major resistance against malaria. There is no question that it is better to be anemic than to be dead. This major influence on the function of the blood - so striking as to be readily apparent in photographs of red blood cells - is the result of a change in a single nucleotide out of the ten billion in the DNA of a typical human cell.

We are still ignorant of the consequences of changes in most of the other nucleotides. We humans look rather different than a tree. Without a doubt we perceive the world differently than a tree does. But down deep, at the molecular heart of life, the trees and we are essentially identical. We both use nucleic acids for heredity; we both use proteins as enzymes to control the chemistry of our cells. Most significantly, we both use precisely the same code book for translating nucleic acid information into protein information, as do virtually all the other creatures on the planet.

How did the critical molecules then arise? At least a few cases are known where the transcription from DNA information into protein information in a mitochondrion employs a different code book from that used by the genes in the nucleus of the very same cell.

This points to a long evolutionary separation of the genetic codes of mitochondria and nuclei, and is consistent with the idea that mitochondria were once free-living organisms incorporated into the cell in a symbiotic relationship billions of years ago.

The development and emerging sophistication of that symbiosis is, incidentally, one answer to the question of what evolution was doing between the origin of the cell and the proliferation of many-celled organisms in the Cambrian explosion. In my laboratory at Cornell University we work on, among other things, prebiological organic chemistry, making some notes of the music of life.

We mix together and spark the gases of the primitive Earth: The sparks correspond to lightning - also present on the ancient Earth and on modern Jupiter. The reaction vessel is initially transparent: But after ten minutes of sparking, we see a strange brown pigment slowly streaking the sides of the vessel. The interior gradually becomes opaque, covered with a thick brown tar. If we had used ultraviolet light - simulating the early Sun - the results would have been more or less the same.

The tar is an extremely rich collection of complex organic molecules, including the constituent parts of proteins and nucleic acids. The stuff of life, it turns out, can be very easily made. Urey had argued compellingly that the early atmosphere of the Earth was hydrogen-rich, as is most of the Cosmos; that the hydrogen has since trickled away to space from Earth, but not from massive Jupiter; and that the origin of life occurred before the hydrogen was lost.

After Urey suggested that such gases be sparked, someone asked him what he expected to make in such an experiment. Using only the most abundant gases that were present on the early Earth and almost any energy source that breaks chemical bonds, we can produce the essential building blocks of life. But in our vessel are only the notes of the music of life - not the music itself. The molecular building blocks must be put together in the correct sequence.

Life is certainly more than the amino acids that make up its proteins and the nucleotides that make up its nucleic acids. But even in ordering these building blocks into long-chain molecules, there has been substantial laboratory progress. Amino acids have been assembled under primitive Earth conditions into molecules resembling proteins. Some of them feebly control useful chemical reactions, as enzymes do.

Nucleotides have been put together into strands of nucleic acid a few dozen units long. Under the right circumstances in the test tube, short nucleic acids can synthesize identical copies of themselves. No one has so far mixed together the gases and waters of the primitive Earth and at the end of the experiment had something crawl out of the test tube.

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The smallest living things known, the viroids, are composed of less than 10, atoms. They cause several different diseases in cultivated plants and have probably most recently evolved from more complex organisms rather than from simpler ones. Indeed, it is hard to imagine a still simpler organism that is in any sense alive. Viroids are composed exclusively of nucleic acid, unlike the viruses, which also have a protein coat.

They are no more than a single strand of RNA with either a linear or a closed circular geometry. Viroids can be so small and still thrive because they are thoroughgoing, unremitting parasites.

Like viruses, they simply take over the molecular machinery of a much larger, well-functioning cell and change it from a factory for making more cells into a factory for making more viroids. The smallest known free-living organisms are the PPLO pleuropneumonia-like organisms and similar small beasts. They are composed of about fifty million atoms. Such organisms, having to be more self-reliant, are also more complicated than viroids and viruses. But the environment of the Earth today is not extremely favorable for simple forms of life.

You have to work hard to make a living. You have to be careful about predators. In the early history of our planet, however, when enormous amounts of organic molecules were being produced by sunlight in a hydrogen-rich atmosphere, very simple, nonparasitic organisms had a fighting chance. The first living things may have been something like free-living viroids only a few hundred nucleotides long. Experimental work on making such creatures from scratch may begin by the end of the century.

There is still much to be understood about the origin of life, including the origin of the genetic code. But we have been performing such experiments for only some thirty years. Nature has had a four-billion-year head start. All in all, we have not done badly. Nothing in such experiments is unique to the Earth. The initial gases, and the energy sources, are common throughout the Cosmos. Chemical reactions like those in our laboratory vessels may be responsible for the organic matter in interstellar space and the amino acids found in meteorites.

Some similar chemistry must have occurred on a billion other worlds in the Milky Way Galaxy. The molecules of life fill the Cosmos. But even if life on another planet has the same molecular chemistry as life here, there is no reason to expect it to resemble familiar organisms.

Consider the enormous diversity of living things on Earth, all of which share the same planet and an identical molecular biology.

Those other beasts and vegetables are probably radically different from any organism we know here. There may be some convergent evolution because there may be only one best solution to a certain environmental problem - something like two eyes, for example, for binocular vision at optical frequencies.

But in general the random character of the evolutionary process should create extraterrestrial creatures very different from any that we know. I cannot tell you what an extraterrestrial being would look like. I am terribly limited by the fact that I know only one kind of life, life on Earth. Some people - science fiction writers and artists, for instance - have speculated on what other beings might be like.

I am skeptical about most of those extraterrestrial visions. They seem to me to rely too much on forms of life we already know. Any given organism is the way it is because of a long series of individually unlikely steps. I do not think life anywhere else would look very much like a reptile, or an insect or a human - even with such minor cosmetic adjustments as green skin, pointy ears and antennae.

But if you pressed me, I could try to imagine something rather different. On a giant gas planet like Jupiter, with an atmosphere rich in hydrogen, helium, methane, water and ammonia, there is no accessible solid surface, but rather a dense cloudy atmosphere in which organic molecules may be falling from the skies like manna from heaven, like the products of our laboratory experiments.

However, there is a characteristic impediment to life on such a planet: An organism must be careful that it is not carried down and fried. To show that life is not out of the question in such a very different planet, my Cornell colleague E. Salpeter and I have made some calculations. Of course, we cannot know precisely what life would be like in such a place, but we wanted to see if, within the laws of physics and chemistry, a world of this sort could possibly be inhabited.

One way to make a living under these conditions is to reproduce before you are fried and hope that convection will carry some of your offspring to the higher and cooler layers of the atmosphere.

Such organisms could be very little. We call them sinkers. But you could also be a floater, some vast hydrogen balloon pumping helium and heavier gases out of its interior and leaving only the lightest gas, hydrogen; or a hot-air balloon, staying buoyant by keeping your interior warm, using energy acquired from the food you eat. Like familiar terrestrial balloons, the deeper a floater is carried, the stronger is the buoyant force returning it to the higher, cooler, safer regions of the atmosphere.

A floater might eat preformed organic molecules, or make its own from sunlight and air, somewhat as plants do on Earth. Up to a point, the bigger a floater is, the more efficient it will be. Salpeter and I imagined floaters kilometers across, enormously larger than the greatest whale that ever was, beings the size of cities. The floaters may propel themselves through the planetary atmosphere with gusts of gas, like a ramjet or a rocket. We imagine them arranged in great lazy herds for as far as the eye can see, with patterns on their skin, an adaptive camouflage implying that they have problems, too.

Because there is at least one other ecological niche in such an environment: Hunters are fast and maneuverable. They eat the floaters both for their organic molecules and for their store of pure hydrogen. Hollow sinkers could have evolved into the first floaters, and self-propelled floaters into the first hunters. There cannot be very many hunters, because if they consume all the floaters, the hunters themselves will perish.

Physics and chemistry permit such lifeforms. Art endows them with a certain charm. Nature, however, is not obliged to follow our speculations. But if there are billions of inhabited worlds in the Milky Way Galaxy, perhaps there will be a few populated by the sinkers, floaters and hunters which our imaginations, tempered by the laws of physics and chemistry, have generated.

Biology is more like history than it is like physics. You have to know the past to understand the present. And you have to know it in exquisite detail.

There is as yet no predictive theory of biology, just as there is not yet a predictive theory of history. The reasons are the same: But we can know ourselves better by understanding other cases.

The study of a single instance of extraterrestrial life, no matter how humble, will deprovincialize biology. For the first time, the biologists will know what other kinds of life are possible. When we say the search for life elsewhere is important, we are not guaranteeing that it will be easy to find - only that it is very much worth seeking.

We have heard so far the voice of life on one small world only. But we have at last begun to listen for other voices in the cosmic fugue. Can you establish their rule on Earth? Twelve Signs of the Zodiac, as the Religion says, are the twelve commanders on the side of light; and the seven planets are said to be the seven commanders on the side of darkness.

And the seven planets oppress all creation and deliver it over to death and all manner of evil: Similarly, we ought not to ask why the human mind troubles to fathom the secrets of the heavens.

The diversity of the phenomena of Nature is so great, and the treasures hidden in the heavens so rich, precisely in order that the human mind shall never be lacking in fresh nourishment. There would be nothing to figure out. There would be no impetus for science. And if we lived in an unpredictable world, where things changed in random or very complex ways, we would not be able to figure things out. Again, there would be no such thing as science.

But we live in an in-between universe, where things change, but according to patterns, rules, or, as we call them, laws of nature. If I throw a stick up in the air, it always falls down. If the sun sets in the west, it always rises again the next morning in the east. And so it becomes possible to figure things out. We can do science, and with it we can improve our lives. Human beings are good at understanding the world. We always have been.

We were able to hunt game or build fires only because we had figured something out. There was a time before television, before motion pictures, before radio, before books. The greatest part of human existence was spent in such a time. Over the dying embers of the campfire, on a moonless night, we watched the stars. The night sky is interesting. There are patterns there. Without even trying, you can imagine pictures. In the northern sky, for example, there is a pattern, or constellation, that looks a little ursine.

Some cultures call it the Great Bear. Others see quite different images. These pictures are not, of course, really in the night sky; we put them there ourselves.

We were hunter folk, and we saw hunters and dogs, bears and young women, all manner of things of interest to us. When seventeenth-century European sailors first saw the southern skies they put objects of seventeenth century interest in the heavens - toucans and peacocks, telescopes and microscopes, compasses and the sterns of ships.

Occasionally our ancestors would see a very bright star with a tail, glimpsed for just a moment, hurtling across the sky. They called it a falling star, but it is not a good name: In some seasons there are many falling stars; in others very few. There is a kind of regularity here as well. Like the Sun and the Moon, stars always rise in the east and set in the west, taking the whole night to cross the sky if they pass overhead.

There are different constellations in different seasons. The same constellations always rise at the beginning of autumn, say. It never happens that a new constellation suddenly rises out of the east. There is an order, a predictability, a permanence about the stars. In a way, they are almost comforting. Certain stars rise just before or set just after the Sun - and at times and positions that vary with the seasons.

If you made careful observations of the stars and recorded them over many years, you could predict the seasons. You could also measure the time of year by noting where on the horizon the Sun rose each day. In the skies was a great calendar, available to anyone with dedication and ability and the means to keep records. Our ancestors built devices to measure the passing of the seasons. In Chaco Canyon, in New Mexico, there is a great roofless ceremonial kiva or temple, dating from the eleventh century.

On June 21, the longest day of the year, a shaft of sunlight enters a window at dawn and slowly moves so that it covers a special niche.

But this happens only around June They also monitored the apparent motion of the Moon: These people paid close attention to the Sun and the Moon and the stars. Some alleged calendrical devices may just possibly be due to chance - an accidental alignment of window and niche on June 21, say. But there are other devices wonderfully different. At one locale in the American Southwest is a set of three upright slabs which were moved from their original position about 1, years ago.

A spiral a little like a galaxy has been carved in the rock. On June 21, the first day of summer, a dagger of sunlight pouring through an opening between the slabs bisects the spiral; and on December 21, the first day of winter, there are two daggers of sunlight that flank the spiral, a unique application of the midday sun to read the calendar in the sky.

Why did people all over the world make such an effort to learn astronomy? We hunted gazelles and antelope and buffalo whose migrations ebbed and flowed with the seasons. Fruits and nuts were ready to be picked in some times but not in others. When we invented agriculture, we had to take care to plant and harvest our crops in the right season. Annual meetings of far-flung nomadic tribes were set for prescribed times. The ability to read the calendar in the skies was literally a matter of life and death.

The reappearance of the crescent moon after the new moon; the return of the Sun after a total eclipse; the rising of the Sun in the morning after its troublesome absence at night were noted by people around the world: Up there in the skies was also a metaphor of immortality. The wind whips through the canyons in the American Southwest, and there is no one to hear it but us - a reminder of the 40, generations of thinking men and women who preceded us, about whom we know almost nothing, upon whom our civilization is based.

He appeared on many television programs, wrote a regular column for Parade , and worked to continually advance the popularity of the science genre. Lewenstein also noted the power of the book as a recruitment tool. Along with Microbe Hunters and The Double Helix , he described Cosmos as one of the "books that people cite as 'Hey, the reason I'm a scientist is because I read that book'.

The popularity of Sagan's Cosmos has been referenced in arguments supporting increased space exploration spending. Reception for Sagan's work was generally positive. His style is iridescent, with lights flashing upon unexpected juxtapositions of thought. If we send just one book to grace the libraries of distant worlds The U. Library of Congress designated Cosmos one of eighty-eight books "that shaped America.

From Wikipedia, the free encyclopedia. For other books, see Cosmos disambiguation. This article is about the Carl Sagan book. A Personal Voyage. A Spacetime Odyssey. Dewey Decimal. Powell's Books. Retrieved 3 January New York: Ballantine Books. Bibliographical Data". Book Depository. The Book Depository International Ltd. The New York Times. Retrieved 21 May Full Description".

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About this Edition". Borders, Inc. The Ideological Rhetoric of Carl Sagan". Quarterly Journal of Speech. Columbia Journalism Review. Stanford News Service. Stanford University. Retrieved 7 January The Planetary Society. Washington Post. The Washington Post Company. The Ideological Rhetoric of Carl Sagan". Quarterly Journal of Speech. Columbia Journalism Review. Stanford News Service.

Stanford University. Retrieved 7 January The Planetary Society.

Washington Post. The Washington Post Company. Carl Sagan". The Science Channel. Archived from the original on Retrieved Public Attitudes and Understanding". National Science Foundation. Archived from the original on 14 January National Institute for Standards and Technology. Cornell News. Cornell University. A History of the Book in America: Volume 5: The Enduring Book: Print Culture.

Michael Schudson. UNC Press. Journal of the American Academy of Religion. Oxford Journals. LXIV 2: Journal of Science Communication. International School for Advanced Studies. Skeptical Inquirer. Retrieved July 11, Perspectives on Political Science. American Enterprise. E New York Times.