{"id":72458,"date":"2022-07-10T14:46:00","date_gmt":"2022-07-10T18:46:00","guid":{"rendered":"https:\/\/www.shortform.com\/blog\/?p=72458"},"modified":"2024-04-15T17:30:03","modified_gmt":"2024-04-15T21:30:03","slug":"cosmos-carl-sagan-book","status":"publish","type":"post","link":"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/","title":{"rendered":"Cosmos by Carl Sagan: Book Overview"},"content":{"rendered":"\n<p>What is Carl Sagan&#8217;s book <em>Cosmos <\/em>about? What\u2019s out there in the vast reaches of space? Are we alone in the universe?<\/p>\n\n\n\n<p>Renowned astronomer Carl Sagan offers some insight into these questions and many more in his widely acclaimed book, <em>Cosmos<\/em>.&nbsp;In this book, he provides a comprehensive description of the science, philosophy, and history of astronomical discovery, from ancient Ionia to the time of the book\u2019s publication in 1980.<\/p>\n\n\n\n<p>Here&#8217;s a brief overview of <em>Cosmos<\/em>.<\/p>\n\n\n\n<!--more-->\n\n\n\n<h2 class=\"wp-block-heading\" id=\"h-cosmos-book-overview\"><strong><em>Cosmos <\/em>Book Overview<\/strong><\/h2>\n\n\n\n<p>The book <em>Cosmos<\/em> by Carl Sagan is an exploration of the universe. In this book, Sagan gives a comprehensive description of the science, philosophy, and history of astronomical discovery, from ancient Ionia to the time of the book\u2019s publication in 1980. He discusses some of the obstacles posed by religious belief and institutions to scientific inquiry throughout history, and he celebrates the victories of the scientific endeavor. Although much research has been done in astronomy since the publication of <em>Cosmos<\/em>, the book remains timeless in the sense of <a href=\"https:\/\/www.shortform.com\/blog\/awe-and-wonder\/\">wonder and awe<\/a> it evokes. Sagan provides us with food for thought on some of the biggest questions pondered by humanity\u2014questions about our place and significance in the vast universe.&nbsp;<\/p>\n\n\n\n<p><a href=\"https:\/\/www.britannica.com\/biography\/Carl-Sagan\">Sagan was an American astronomer<\/a> who spent most of his prolific career in <a href=\"https:\/\/www.britannica.com\/topic\/Cornell-University\">Cornell University<\/a>\u2019s Laboratory for Planetary Studies. His 1977 book <em>The Dragons of Eden,<\/em> about the <a href=\"https:\/\/www.shortform.com\/blog\/evolution-of-human-intelligence\/\">evolution of human intelligence<\/a>, won a Pulitzer Prize. In the 1980s Sagan became a popular science writer and public figure, due largely to the success of <em>Cosmos <\/em>and the accompanying television show of the same name. His popularity continued following the publication of his 1985 science fiction novel <a href=\"https:\/\/www.simonandschuster.com\/books\/Contact\/Carl-Sagan\/9781501197987\"><em>Contact<\/em><\/a>, which was made into a movie. Sagan died in 1996, leaving a vast body of intellectual and literary work as his legacy.&nbsp;<\/p>\n\n\n\n<p>This guide will summarize the key ideas in <em>Cosmos<\/em> in three parts:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>In Part 1, we\u2019ll summarize Sagan\u2019s description of the evolution of life on Earth, and his thoughts about the possibility that a similar evolution could occur elsewhere, based on what we know about the universe.&nbsp;<\/li><li>In Part 2, we\u2019ll look at the history of humanity\u2019s inquiry into the cosmos, outlining the astronomical discoveries made by important scientific figures.&nbsp;<\/li><li>In Part 3, we\u2019ll delve into Sagan\u2019s theories about the possibility for <a href=\"https:\/\/www.shortform.com\/blog\/interstellar-space-travel\/\">interstellar travel<\/a>, and the search for extraterrestrial life.&nbsp;<\/li><\/ul>\n\n\n\n<p>As this book was published in 1980, we\u2019ll update the information with the scientific discoveries made since that time, as well as provide perspectives from other experts in related fields.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-part-1-the-vastness-of-space-and-time\"><strong>Part 1: The Vastness of Space and Time<\/strong><\/h3>\n\n\n\n<p>In this section, we\u2019ll discuss Sagan\u2019s description of the vastness of the cosmos (or universe), and our place in it. We\u2019ll begin by examining how life evolved on Earth to find our place within that timeline. After situating ourselves, we\u2019ll zoom out to look at Sagan\u2019s bigger picture of where Earth fits into the timeline and space of the universe. <strong>Ultimately, when we look at what\u2019s known about the cosmos, we\u2019ll discover that in the grand scheme of things, we\u2019re pretty insignificant.<\/strong>&nbsp;<\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-humanity-s-place-on-earth\"><strong>Humanity\u2019s Place on Earth<\/strong><\/h4>\n\n\n\n<p>Sagan begins the story of humanity\u2019s history by teaching us that <strong>all life is made of carbon-based organic molecules,<\/strong> but there was once a time on Earth without life. How was it possible for life to come from non-life? Let\u2019s look at a timeline of how that process occurred and discuss Sagan\u2019s thoughts on whether the same thing could occur on other planets.<\/p>\n\n\n\n<p><strong>About 4.6 billion years ago, the Earth formed out of condensed gas and dust.<\/strong> The fossil record tells us life arose about 4 billion years ago, meaning that for 600 million years there was no life on Earth. According to Sagan, hydrogen-based molecules that are found throughout space were gradually broken down by the sun\u2019s energy, and they formed into other more complex molecules\u2014from one-celled plants to multicellular organisms. Sagan says that scientists have been able to replicate this on a much smaller scale in the laboratory. Scientists can create <em>organic<\/em> molecules that may have the potential to evolve into more complex life forms by exposing common <em>inorganic<\/em> gas molecules to an energy source, such as ultraviolet light. So, Sagan says, we know it\u2019s possible to create living molecules from simple non-living gasses.&nbsp;<\/p>\n\n\n\n<p><strong>About 1 billion years ago, simple plants had evolved<\/strong>. Sagan tells us that for about 3 of the 4 billion years of life on Earth, the dominant life form was blue-green algae that covered the oceans. Those plants gradually changed the atmosphere by generating oxygen, allowing for many types of organisms to arise and others to die off. The process of <em>evolution by <a href=\"https:\/\/www.shortform.com\/blog\/natural-selection-in-evolution\/\">natural selection<\/a><\/em> gradually shaped these <a href=\"https:\/\/www.shortform.com\/blog\/simple-organisms\/\">simple organisms<\/a> into all of the life forms we know today.<\/p>\n\n\n\n<p><strong>About 10 million years ago, early <a href=\"https:\/\/www.shortform.com\/blog\/history-of-hominids\/\">hominids<\/a> appeared<\/strong>, according to Sagan, with modern humans emerging only about 300,000 years ago. This means humans have existed for approximately .007% of the Earth\u2019s history.&nbsp;<\/p>\n\n\n\n<h5 class=\"wp-block-heading\" id=\"h-evolution-on-other-planets\">Evolution on Other Planets<\/h5>\n\n\n\n<p>Could life have evolved similarly on other planets? Sagan says it\u2019s certainly possible. The gasses from which the first living molecules formed exist everywhere in the universe. However, for <em>3 billion<\/em> years, life on Earth never evolved past blue-green algae, so Sagan points out that evolving large complex life forms is <em>much<\/em> harder than the <a href=\"https:\/\/www.shortform.com\/blog\/what-is-the-origin-of-life-on-earth\/\">origin of life<\/a> itself. Therefore, he says that<strong> if there is <a href=\"https:\/\/www.shortform.com\/blog\/is-there-intelligent-life-on-other-planets\/\">life on other planets<\/a>, it\u2019s more likely to be simple organisms<\/strong>, because the time required to evolve complex intelligent life means that, statistically, the majority of life in the universe would be in some stage of evolution preceding the complex life form stage.&nbsp;<\/p>\n\n\n\n<p>However, it\u2019s certainly possible that there are some planets on which life has been evolving as long as it has been on Earth, or even much longer. Sagan speculates that life forms that have evolved much <em>longer<\/em> than humans may become extinct (for various reasons including self-destruction, which he argues is happening with humans), leaving only a relatively small time window, on the cosmic scale of time, for multiple forms of complex, <em>intelligent <\/em>life to exist simultaneously.&nbsp;&nbsp;<\/p>\n\n\n\n<p>Sagan also points out that life elsewhere in the cosmos is probably nothing like we imagine, because our imaginations are limited by what we know. Given the many possibilities in the way molecules can combine, along with the vast possibilities for how characteristics could evolve, Sagan says that <strong>any life that has evolved elsewhere would most likely be out of our realm of imagination.&nbsp;<\/strong><\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-earth-s-place-in-the-universe\"><strong>Earth\u2019s Place in the Universe<\/strong><\/h4>\n\n\n\n<p>While Earth seems special and central to our perspective, from the cosmic perspective it\u2019s a minuscule piece of rock floating in a vast universe. To begin to understand just how vast the universe is, Sagan explains that distances between the celestial objects are so huge that we measure them in <em>speed of light<\/em> units. Light travels 6 trillion miles (10 trillion km) in one year, and a little over 11 million miles (18 million km) in one minute. Earth is 8 light-minutes away from the sun.<\/p>\n\n\n\n<p>So, to understand our place in the universe as Sagan describes it, we\u2019ll begin with Earth and zoom out. The Earth and our eight planet neighbors all orbit the sun, due to its gravitational pull. This is called our <em>solar system<\/em>. <\/p>\n\n\n\n<p>Zooming out further from our own solar system, Sagan tells us that the sun is a relatively ordinary star that resides toward the outer reaches of the <em>Milky Way galaxy<\/em>. A galaxy is an enormous cluster of stars, all linked together by gravity. <strong>A typical galaxy has an average of about 100 billion stars, Sagan says, and the cosmos includes about 100 billion galaxies.<\/strong> <\/p>\n\n\n\n<p>Our own galaxy, the Milky Way, is relatively large, containing about 400 billion stars. Sagan says that <strong>the majority of those stars <em>could<\/em> potentially have satellites (planets) revolving around them<\/strong>, as does our sun. He says that evidence would suggest that most probably do, which suggests <em>hundreds of billions <\/em>of potential planets in just our galaxy alone, not to mention the other 100 billion known galaxies.&nbsp;<\/p>\n\n\n\n<p>If these numbers convey how vast the <em>matter<\/em> of the universe is, Sagan goes on to point out that <strong>despite the staggering number of stars and other orbiting objects in the universe, it actually consists of far more empty space than matter.<\/strong><\/p>\n\n\n\n<p>All of this considered, Sagan argues that we must conclude that we\u2019re not that significant in the grand scheme of things. Not only is Earth\u2019s place in the universe insignificant, but we humans are only one of innumerable possible forms of life, and even among the diverse life forms on Earth, we\u2019re descended from blue-green algae, just like everything else. Sagan says that <strong>there\u2019s no scientific justification for claiming that our place or position in the world is unique or special<\/strong> relative to anything else.&nbsp;<\/p>\n\n\n\n<p>Despite this, he points out that many scientists have been persecuted and ostracized for making such claims. Next we\u2019ll discuss some examples of those who have challenged the perspective of Earth-centered and human-centered privilege.&nbsp;<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-part-2-history-of-astronomical-thought\"><strong>Part 2: <\/strong><strong>History of Astronomical Thought&nbsp;<\/strong><\/h3>\n\n\n\n<p>Humans in all places and times have been fascinated by the skies. We\u2019ve used the stars to guide us, to mark the passage of seasons, and make sense of our place in the world for as long as we\u2019ve existed. But our understanding of the nature and order of the universe, and our place in it, has evolved substantially over time. Sagan gives a historical picture of how humanity developed its beliefs \u201cfrom chaos to cosmos.\u201d&nbsp;<\/p>\n\n\n\n<p>In this section, we\u2019ll briefly outline the Western history of astronomical discovery, as presented by Sagan, from Thales of Miletus in ancient Ionia, to Isaac Newton in 17th-century England.&nbsp;&nbsp;<\/p>\n\n\n\n<h5 class=\"wp-block-heading\" id=\"h-the-ionian-awakening\">The Ionian Awakening<\/h5>\n\n\n\n<p>Sagan\u2019s history begins between 600 and 400 BC, when a revolution of scientific thought occurred in Ionia, a Greek settlement on the Aegean coast in what is now Turkey. Ionia is often considered the birthplace of science, in the Western tradition. This revolution was sparked by a scientist named <strong>Thales of Miletus<\/strong>, who Sagan says was<strong> the first known scientist bold enough to attempt to explain the world without appealing to the supernatural<\/strong>. He explains that this had far-reaching consequences, as it prompted a shift from a world made by gods to a world made by natural processes.<\/p>\n\n\n\n<p>Sagan details the revolutionary discoveries made during this time, including the idea that the sun was the center of the universe (heliocentric), rather than the Earth (geocentric). Copernicus is often given credit for the <a href=\"https:\/\/www.shortform.com\/blog\/heliocentric-model-of-the-universe\/\">heliocentric model of the universe<\/a>. However, Sagan says that <strong>Aristarchus is the first person known to have proposed that the Earth revolves around the sun, in Ionia, in 280 BC, 1800 years before Copernicus.<\/strong> Therefore, he points out that Galileo described Copernicus as \u201crestorer and confirmer\u201d of this worldview, not the originator of it.&nbsp;<\/p>\n\n\n\n<p>Scientists in this period also proposed that the orbits of the planets were<em> elliptical<\/em> rather than circular, and that gravitational forces were at work in their orbiting of the sun.&nbsp;<\/p>\n\n\n\n<p>According to Sagan, Aristarchus\u2019 \u201cgreat legacy\u201d is the argument that we\u2019re not special. He argued that <strong>humans are not the center of the universe, nor is our planet.<\/strong> This idea can be extended to many aspects of life\u2014Aristarchus challenged the prevailing <em>anthropocentric <\/em>(\u201chuman-centered\u201d) worldview. Sagan explains that this was a bold challenge to the social order, as it conflicted with a religious worldview that asserted that humans are uniquely created by the Gods, as well as with the idea of natural social hierarchies.<\/p>\n\n\n\n<h5 class=\"wp-block-heading\" id=\"h-alexandria\">Alexandria<\/h5>\n\n\n\n<p>By the 3rd century AD Alexandria, Egypt had become the new center of scientific inquiry in the West. <strong>Around 285 BC, the Great Library of Alexandria was established as the world\u2019s greatest repository of scientific knowledge and literature<\/strong>, though Sagan laments that most of the documents were lost when it was destroyed. He says that he has often wondered where we might be today (scientifically) if all of that knowledge hadn\u2019t been lost.&nbsp;<\/p>\n\n\n\n<p>Sagan explains that it was in Alexandria that <strong>Eratosthenes (276-194 BC) made the discovery that the Earth was round.<\/strong> And although this was resisted by many at the time, he points out that it was crucial knowledge for an accurate scientific understanding of how the celestial bodies operate, as well as solidifying a view of Earth as one among other spherical celestial bodies. This also paved the way for explorers who would brave the circumnavigation of the globe centuries later.<\/p>\n\n\n\n<p>However, Sagan explains that much of the astronomical theory coming out of this time period was rejected in favor of the more-accepted <em>Ptolemaic<\/em> worldview. <strong>Ptolemy (100-170 AD), maintained that the Earth was the center of the universe<\/strong>, and the sun, moon, other planets, and stars moved around it, attached to invisible spheres. This model, Sagan says, was ultimately supported by the Church in the coming centuries, and because of that institution&#8217;s powerful reach,<strong> the Ptolemaic model lingered through the Middle Ages<\/strong>.&nbsp;<\/p>\n\n\n\n<h5 class=\"wp-block-heading\" id=\"h-european-renaissance\">European Renaissance<\/h5>\n\n\n\n<p>When Europe began to emerge from what is known as the Dark Ages, the astronomical models we know to be correct today were developed. Here we\u2019ll look at a brief timeline of discovery, as presented by Sagan, during the 16th and 17th centuries in Europe.<\/p>\n\n\n\n<p><strong>In 1543, Polish mathematician and astronomer Nicolaus Copernicus proposed his heliocentric model.<\/strong> In 1616 the Catholic Church placed Copernicus\u2019 work on their <a href=\"https:\/\/www.shortform.com\/blog\/banning-books-in-the-us\/\">banned books<\/a> list, where it remained until 1835.&nbsp;<\/p>\n\n\n\n<p><strong>In 1571, German astronomer Johannes Kepler also came out in support of the Copernican heliocentric model.<\/strong> According to Sagan, Kepler was a religious man, but he thought a heliocentric model was more in line with religious beliefs. In his view, the sun was a metaphor for God, around which everything revolves. Sagan says that Kepler also calculated the elliptical orbits of the planets to explain their previously unexplainable movements. Because of these theories, Kepler was excommunicated by the Lutheran Church.<\/p>\n\n\n\n<p><strong>In the late 1500s, Italian astronomer Galileo Galilei made advancements to the existing telescope technology.<\/strong> Due to his more powerful designs, he was able to discover the four largest moons of Jupiter, and the craters of the moon. Galileo also adhered to the heliocentric model.&nbsp;<\/p>\n\n\n\n<p><strong>In the 1600s, Isaac Newton discovered the law of gravity<\/strong>, which Sagan tells us was able to solidify the explanation of how the planets revolve around the sun, and the moons around the planets. Sagan says that Newton\u2019s discoveries and the laws of nature derived from them, laid the foundation for our current understanding of the universe.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\" id=\"h-part-3-exploration-of-space\"><strong>Part 3: <\/strong><strong>Exploration of Space<\/strong><\/h3>\n\n\n\n<p>Now that we have a solid working model of the universe, and have been able to directly observe much of it via telescopes, we move into the age of physical exploration. We\u2019ll begin with discussing what modern astronomers have discovered about the celestial bodies in our own solar system, then look at the potential that lies beyond our solar system. Sagan offers some insightful views on the potential for interstellar travel and for discovery of life on other worlds.&nbsp;<\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-our-solar-system\"><strong>Our Solar System<\/strong><\/h4>\n\n\n\n<p>On July 20th, 1969, humans made the first trip to a destination off the planet Earth and set foot on the moon. The moon is the nearest celestial body to us, and it remains the only one humans have ever traveled to. However, Sagan explains that we\u2019ve been able to create vehicles that can travel much further, enduring the inhospitable climates elsewhere in the solar system, and send information to us.&nbsp;<\/p>\n\n\n\n<p>At present, Sagan says that <strong>none of the atmospheres and climates of the other bodies in our own solar system are inhabitable by anything like the kind of life we have here on Earth. <\/strong>But he reminds us that life could take any number of forms, and because it would have evolved in a different atmosphere than ours, it could take forms that we might not expect.&nbsp;&nbsp;<\/p>\n\n\n\n<h5 class=\"wp-block-heading\" id=\"h-looking-for-life-on-mars\">Looking for Life on Mars<\/h5>\n\n\n\n<p>So far, Sagan explains, we\u2019ve been able to fairly extensively study the Moon, Mars, Venus, Jupiter and its moons, and Saturn and its moons. Sagan says that Mars has been the primary focus of study because its polar caps are covered with ice\u2014which means there\u2019s the possibility that it was once liquid water, which in turn denotes the possibility for life.<\/p>\n\n\n\n<p>As of the writing of this book, Sagan says that <strong>no compelling evidence for life has been found on Mars.<\/strong> However, he says we\u2019ve been able to map the entire planet with orbiting satellites, and the US\u2019s Viking lander has successfully landed on its surface and collected and tested soil samples. While some of the microbiology tests showed promise of chemical reaction, Sagan says there was no definitive evidence of the kind of life we know.&nbsp;<\/p>\n\n\n\n<p>Sagan speculates on what we should do if we did discover any form of life on Mars. He strongly feels that if we discover even the smallest microbial life we should leave Mars alone entirely, and do nothing more to interfere with it. However, he says <strong>if we conclude that there is no life on Mars, he can imagine possibilities for humans to colonize and settle there, after altering the atmosphere<\/strong>.<\/p>\n\n\n\n<h5 class=\"wp-block-heading\" id=\"h-the-space-probes\">The Space Probes&nbsp;<\/h5>\n\n\n\n<p>Spacecraft called Voyager I and II were designed to explore beyond our immediate neighbors. Launched in 1977, their mission was to fly beyond Mars, travel among the moons of Jupiter and Saturn, and then ultimately drift off into interstellar space forever.&nbsp;<\/p>\n\n\n\n<p>Sagan tells us that Voyager I took pictures of three of Jupiter\u2019s four largest moons, and Voyager II was able to capture photos of the fourth one, Europa. <strong>Europa is unique<\/strong>, he says,<strong> in that there are visible geometric lines on its surface that look like nothing else we know of, other than man-made canals.<\/strong> <\/p>\n\n\n\n<p>Another one of Jupiter\u2019s moons, Io, is unique in that the Voyager images show active volcanoes over much of its colorful surface. Sagan says this appears to be a newer planet still actively forming, with a rapidly changing landscape. (Shortform note: See a photo and more in-depth description of Io <a href=\"https:\/\/solarsystem.nasa.gov\/resources\/809\/high-resolution-global-view-of-io\/?category=moons\/jupiter-moons_io\">here<\/a>.)<\/p>\n\n\n\n<h4 class=\"wp-block-heading\" id=\"h-beyond-our-solar-system\"><strong>Beyond Our Solar System<\/strong><\/h4>\n\n\n\n<p>Even with the ability for travel <em>within<\/em> our solar system being limited, Sagan points out that humans still dream of going further, and he thinks we always will. Since we haven\u2019t found any evidence of a habitable environment within our solar system, might there be some in other solar systems?<\/p>\n\n\n\n<p>We don\u2019t know how many planetary systems might exist in the cosmos. Sagan says the evidence suggests that <strong>almost all single stars like the sun should have satellite planets<\/strong>, but we can\u2019t see them because the light of the stars is too bright. He says scientists are working on telescope technology that could dim the light so they might be able to see the much smaller objects orbiting the stars. Also, he says that in addition to \u201cplanets\u201d orbiting stars, Jupiter, Saturn, and Uranus all have satellite \u201cmoons\u201d that are planet-like, so many other planets could have such satellites as well. So <strong>there are innumerable possibilities for other worlds that could sustain life.<\/strong><\/p>\n\n\n\n<h5 class=\"wp-block-heading\" id=\"h-interstellar-travel\">Interstellar Travel<\/h5>\n\n\n\n<p>Alpha Centauri is the closest \u201cstar\u201d to us, being 4.3 light-years away, but Sagan explains that it\u2019s actually a triple star system. Considering the vast distance, <strong>will it ever be possible to travel to other solar systems?<\/strong> Sagan suggests that <strong>nuclear fusion technology might make it possible<\/strong> to power spacecraft fast enough<strong>.<\/strong> However, he explains that such technology would require the spacecraft to be launched from Earth\u2019s orbit, rather than from land, because of the dangers involved with the nuclear fusion reaction.&nbsp;<\/p>\n\n\n\n<p>Sagan says <strong>the technology to build a ship that can travel anywhere close to light-speed is probably thousands of years away<\/strong>, but a ship using nuclear fusion technology may be able to travel about 10% the speed of light. With Alpha Centauri being 4.3 light-years away, a voyage there would take 43 years, meaning it would be feasible for humans to travel there within a lifetime. But he proposes that to travel any further, we might need \u201cmultigenerational\u201d spacecraft, where generations of humans would be born and live their lives, so that subsequent generations might reach other solar systems.&nbsp;<\/p>\n\n\n\n<p>Considering the scientific discoveries being made in Ionia over 2,000 years ago, Sagan believes that we might be there right now if that scientific inquiry had not been suppressed by religious forces for centuries.<\/p>\n\n\n\n<h5 class=\"wp-block-heading\" id=\"h-the-search-for-extraterrestrial-life\">The Search for Extraterrestrial Life<\/h5>\n\n\n\n<p>The idea of intelligent life existing on other planets is probably the most powerful driving force of humanity\u2019s exploration of the cosmos. It\u2019s the theme of countless works of human imagination, from books and poetry to movies and television. Sagan believes <strong>the evidence would suggest it\u2019s far more likely than not that there\u2019s <\/strong><strong><em>some<\/em><\/strong><strong> kind of life out there in the universe<\/strong>; he says there could realistically be a hundred billion planetary systems in the galaxy, and each and every one of them would be unique.&nbsp;<\/p>\n\n\n\n<p>According to Sagan, <strong>the same kind of evolutionary process that happened on Earth should logically operate everywhere in the universe.<\/strong> But with the number of possibilities of how that would unfold in a hundred billion unique environments, he thinks any life that may have evolved would probably be nothing like humans, or any kind of life we know.&nbsp;<\/p>\n\n\n\n<p>Scientists have been intentionally trying to communicate with other potential life in the universe since the 1970s. Sagan says that <strong>we have the technology to communicate over interstellar distances; it\u2019s called radio astronomy<\/strong>. Radio waves travel at the speed of light. The Arecibo Observatory in Puerto Rico has been searching continuously for any radio waves coming from outer space, and Sagan says that it once broadcast a message into space, directed toward a distant star cluster called M13.<\/p>\n\n\n\n<p>Humans have created many imagined scenarios in film and literature depicting the arrival of alien life on Earth. In pondering this possibility, Sagan says that one thing is clear:<strong> There\u2019s no cause to worry about what we would <\/strong><strong><em>do<\/em><\/strong><strong> if extraterrestrial beings arrived here on Earth. Because if that happened, they\u2019d be so technologically beyond us that there would be nothing we <\/strong><strong><em>could<\/em><\/strong><strong> do.<\/strong> He also hypothesizes that any species that has survived long enough to develop such technology has probably learned how to live effectively and peacefully with themselves and others, or they would have destroyed themselves already, as humans may be in danger of doing.&nbsp;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>What is Carl Sagan&#8217;s book Cosmos about? What\u2019s out there in the vast reaches of space? Are we alone in the universe? Renowned astronomer Carl Sagan offers some insight into these questions and many more in his widely acclaimed book, Cosmos.&nbsp;In this book, he provides a comprehensive description of the science, philosophy, and history of astronomical discovery, from ancient Ionia to the time of the book\u2019s publication in 1980. Here&#8217;s a brief overview of Cosmos.<\/p>\n","protected":false},"author":8,"featured_media":72511,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[40,39,160],"tags":[686],"class_list":["post-72458","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-books","category-history","category-science","tag-cosmos","","tg-column-two"],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v24.3 (Yoast SEO v24.3) - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Cosmos by Carl Sagan: Book Overview - Shortform Books<\/title>\n<meta name=\"description\" content=\"Carl Sagan&#039;s Cosmos is a comprehensive description of the science, philosophy, and history of astronomical discovery. Here&#039;s a book overview.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Cosmos by Carl Sagan: Book Overview\" \/>\n<meta property=\"og:description\" content=\"Carl Sagan&#039;s Cosmos is a comprehensive description of the science, philosophy, and history of astronomical discovery. Here&#039;s a book overview.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/\" \/>\n<meta property=\"og:site_name\" content=\"Shortform Books\" \/>\n<meta property=\"article:published_time\" content=\"2022-07-10T18:46:00+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2024-04-15T21:30:03+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/s3.amazonaws.com\/wordpress.shortform.com\/blog\/wp-content\/uploads\/2022\/07\/reading-outside-stars.jpg\" \/>\n\t<meta property=\"og:image:width\" content=\"1069\" \/>\n\t<meta property=\"og:image:height\" content=\"649\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/jpeg\" \/>\n<meta name=\"author\" content=\"Hannah Aster\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"Hannah Aster\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"17 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/#article\",\"isPartOf\":{\"@id\":\"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/\"},\"author\":{\"name\":\"Hannah Aster\",\"@id\":\"https:\/\/www.shortform.com\/blog\/#\/schema\/person\/f39f52830e4f7039a16e45d12354542f\"},\"headline\":\"Cosmos by Carl Sagan: Book Overview\",\"datePublished\":\"2022-07-10T18:46:00+00:00\",\"dateModified\":\"2024-04-15T21:30:03+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/\"},\"wordCount\":3777,\"commentCount\":0,\"publisher\":{\"@id\":\"https:\/\/www.shortform.com\/blog\/#organization\"},\"image\":{\"@id\":\"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/#primaryimage\"},\"thumbnailUrl\":\"https:\/\/www.shortform.com\/blog\/wp-content\/uploads\/2022\/07\/reading-outside-stars.jpg\",\"keywords\":[\"Cosmos\"],\"articleSection\":[\"Books\",\"History\",\"Science\"],\"inLanguage\":\"en-US\",\"potentialAction\":[{\"@type\":\"CommentAction\",\"name\":\"Comment\",\"target\":[\"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/#respond\"]}]},{\"@type\":\"WebPage\",\"@id\":\"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/\",\"url\":\"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/\",\"name\":\"Cosmos by Carl Sagan: Book Overview - Shortform Books\",\"isPartOf\":{\"@id\":\"https:\/\/www.shortform.com\/blog\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/#primaryimage\"},\"image\":{\"@id\":\"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/#primaryimage\"},\"thumbnailUrl\":\"https:\/\/www.shortform.com\/blog\/wp-content\/uploads\/2022\/07\/reading-outside-stars.jpg\",\"datePublished\":\"2022-07-10T18:46:00+00:00\",\"dateModified\":\"2024-04-15T21:30:03+00:00\",\"description\":\"Carl Sagan's Cosmos is a comprehensive description of the science, philosophy, and history of astronomical discovery. Here's a book overview.\",\"breadcrumb\":{\"@id\":\"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/#breadcrumb\"},\"inLanguage\":\"en-US\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/\"]}]},{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/#primaryimage\",\"url\":\"https:\/\/www.shortform.com\/blog\/wp-content\/uploads\/2022\/07\/reading-outside-stars.jpg\",\"contentUrl\":\"https:\/\/www.shortform.com\/blog\/wp-content\/uploads\/2022\/07\/reading-outside-stars.jpg\",\"width\":1069,\"height\":649},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\/\/www.shortform.com\/blog\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Cosmos by Carl Sagan: Book Overview\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\/\/www.shortform.com\/blog\/#website\",\"url\":\"https:\/\/www.shortform.com\/blog\/\",\"name\":\"Shortform Books\",\"description\":\"The World&#039;s Best Book Summaries\",\"publisher\":{\"@id\":\"https:\/\/www.shortform.com\/blog\/#organization\"},\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\/\/www.shortform.com\/blog\/?s={search_term_string}\"},\"query-input\":{\"@type\":\"PropertyValueSpecification\",\"valueRequired\":true,\"valueName\":\"search_term_string\"}}],\"inLanguage\":\"en-US\"},{\"@type\":\"Organization\",\"@id\":\"https:\/\/www.shortform.com\/blog\/#organization\",\"name\":\"Shortform Books\",\"url\":\"https:\/\/www.shortform.com\/blog\/\",\"logo\":{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\/\/www.shortform.com\/blog\/#\/schema\/logo\/image\/\",\"url\":\"https:\/\/www.shortform.com\/blog\/wp-content\/uploads\/2019\/06\/logo-equilateral-with-text-no-bg.png\",\"contentUrl\":\"https:\/\/www.shortform.com\/blog\/wp-content\/uploads\/2019\/06\/logo-equilateral-with-text-no-bg.png\",\"width\":500,\"height\":74,\"caption\":\"Shortform Books\"},\"image\":{\"@id\":\"https:\/\/www.shortform.com\/blog\/#\/schema\/logo\/image\/\"}},{\"@type\":\"Person\",\"@id\":\"https:\/\/www.shortform.com\/blog\/#\/schema\/person\/f39f52830e4f7039a16e45d12354542f\",\"name\":\"Hannah Aster\",\"image\":{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\/\/www.shortform.com\/blog\/#\/schema\/person\/image\/\",\"url\":\"https:\/\/secure.gravatar.com\/avatar\/0302cb2690b70a21639bc6873e587f42d39d02385b7e59d8efd0d3e000ae7681?s=96&d=mm&r=g\",\"contentUrl\":\"https:\/\/secure.gravatar.com\/avatar\/0302cb2690b70a21639bc6873e587f42d39d02385b7e59d8efd0d3e000ae7681?s=96&d=mm&r=g\",\"caption\":\"Hannah Aster\"},\"description\":\"Hannah is a seasoned writer and editor who started her journey with Shortform nearly five years ago. She grew up reading mostly fiction books but transitioned to non-fiction writing when she started her travel website in 2018. When she's not writing or traveling, you can find Hannah working on home reno projects, crafting, or taking care of plants.\",\"knowsAbout\":[\"Graduated summa cum laude with a bachelor's degree in English and minors in professional and creative writing\"],\"jobTitle\":\"SEO Team Lead\",\"worksFor\":\"Shortform\",\"url\":\"https:\/\/www.shortform.com\/blog\/author\/hannah\/\"}]}<\/script>\n<!-- \/ Yoast SEO Premium plugin. -->","yoast_head_json":{"title":"Cosmos by Carl Sagan: Book Overview - Shortform Books","description":"Carl Sagan's Cosmos is a comprehensive description of the science, philosophy, and history of astronomical discovery. Here's a book overview.","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/","og_locale":"en_US","og_type":"article","og_title":"Cosmos by Carl Sagan: Book Overview","og_description":"Carl Sagan's Cosmos is a comprehensive description of the science, philosophy, and history of astronomical discovery. Here's a book overview.","og_url":"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/","og_site_name":"Shortform Books","article_published_time":"2022-07-10T18:46:00+00:00","article_modified_time":"2024-04-15T21:30:03+00:00","og_image":[{"width":1069,"height":649,"url":"https:\/\/s3.amazonaws.com\/wordpress.shortform.com\/blog\/wp-content\/uploads\/2022\/07\/reading-outside-stars.jpg","type":"image\/jpeg"}],"author":"Hannah Aster","twitter_card":"summary_large_image","twitter_misc":{"Written by":"Hannah Aster","Est. reading time":"17 minutes"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"Article","@id":"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/#article","isPartOf":{"@id":"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/"},"author":{"name":"Hannah Aster","@id":"https:\/\/www.shortform.com\/blog\/#\/schema\/person\/f39f52830e4f7039a16e45d12354542f"},"headline":"Cosmos by Carl Sagan: Book Overview","datePublished":"2022-07-10T18:46:00+00:00","dateModified":"2024-04-15T21:30:03+00:00","mainEntityOfPage":{"@id":"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/"},"wordCount":3777,"commentCount":0,"publisher":{"@id":"https:\/\/www.shortform.com\/blog\/#organization"},"image":{"@id":"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/#primaryimage"},"thumbnailUrl":"https:\/\/www.shortform.com\/blog\/wp-content\/uploads\/2022\/07\/reading-outside-stars.jpg","keywords":["Cosmos"],"articleSection":["Books","History","Science"],"inLanguage":"en-US","potentialAction":[{"@type":"CommentAction","name":"Comment","target":["https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/#respond"]}]},{"@type":"WebPage","@id":"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/","url":"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/","name":"Cosmos by Carl Sagan: Book Overview - Shortform Books","isPartOf":{"@id":"https:\/\/www.shortform.com\/blog\/#website"},"primaryImageOfPage":{"@id":"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/#primaryimage"},"image":{"@id":"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/#primaryimage"},"thumbnailUrl":"https:\/\/www.shortform.com\/blog\/wp-content\/uploads\/2022\/07\/reading-outside-stars.jpg","datePublished":"2022-07-10T18:46:00+00:00","dateModified":"2024-04-15T21:30:03+00:00","description":"Carl Sagan's Cosmos is a comprehensive description of the science, philosophy, and history of astronomical discovery. Here's a book overview.","breadcrumb":{"@id":"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/#breadcrumb"},"inLanguage":"en-US","potentialAction":[{"@type":"ReadAction","target":["https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/"]}]},{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/#primaryimage","url":"https:\/\/www.shortform.com\/blog\/wp-content\/uploads\/2022\/07\/reading-outside-stars.jpg","contentUrl":"https:\/\/www.shortform.com\/blog\/wp-content\/uploads\/2022\/07\/reading-outside-stars.jpg","width":1069,"height":649},{"@type":"BreadcrumbList","@id":"https:\/\/www.shortform.com\/blog\/cosmos-carl-sagan-book\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/www.shortform.com\/blog\/"},{"@type":"ListItem","position":2,"name":"Cosmos by Carl Sagan: Book Overview"}]},{"@type":"WebSite","@id":"https:\/\/www.shortform.com\/blog\/#website","url":"https:\/\/www.shortform.com\/blog\/","name":"Shortform Books","description":"The World&#039;s Best Book Summaries","publisher":{"@id":"https:\/\/www.shortform.com\/blog\/#organization"},"potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/www.shortform.com\/blog\/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"en-US"},{"@type":"Organization","@id":"https:\/\/www.shortform.com\/blog\/#organization","name":"Shortform Books","url":"https:\/\/www.shortform.com\/blog\/","logo":{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/www.shortform.com\/blog\/#\/schema\/logo\/image\/","url":"https:\/\/www.shortform.com\/blog\/wp-content\/uploads\/2019\/06\/logo-equilateral-with-text-no-bg.png","contentUrl":"https:\/\/www.shortform.com\/blog\/wp-content\/uploads\/2019\/06\/logo-equilateral-with-text-no-bg.png","width":500,"height":74,"caption":"Shortform Books"},"image":{"@id":"https:\/\/www.shortform.com\/blog\/#\/schema\/logo\/image\/"}},{"@type":"Person","@id":"https:\/\/www.shortform.com\/blog\/#\/schema\/person\/f39f52830e4f7039a16e45d12354542f","name":"Hannah Aster","image":{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/www.shortform.com\/blog\/#\/schema\/person\/image\/","url":"https:\/\/secure.gravatar.com\/avatar\/0302cb2690b70a21639bc6873e587f42d39d02385b7e59d8efd0d3e000ae7681?s=96&d=mm&r=g","contentUrl":"https:\/\/secure.gravatar.com\/avatar\/0302cb2690b70a21639bc6873e587f42d39d02385b7e59d8efd0d3e000ae7681?s=96&d=mm&r=g","caption":"Hannah Aster"},"description":"Hannah is a seasoned writer and editor who started her journey with Shortform nearly five years ago. She grew up reading mostly fiction books but transitioned to non-fiction writing when she started her travel website in 2018. When she's not writing or traveling, you can find Hannah working on home reno projects, crafting, or taking care of plants.","knowsAbout":["Graduated summa cum laude with a bachelor's degree in English and minors in professional and creative writing"],"jobTitle":"SEO Team Lead","worksFor":"Shortform","url":"https:\/\/www.shortform.com\/blog\/author\/hannah\/"}]}},"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"https:\/\/www.shortform.com\/blog\/wp-content\/uploads\/2022\/07\/reading-outside-stars.jpg","_links":{"self":[{"href":"https:\/\/www.shortform.com\/blog\/wp-json\/wp\/v2\/posts\/72458","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.shortform.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.shortform.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.shortform.com\/blog\/wp-json\/wp\/v2\/users\/8"}],"replies":[{"embeddable":true,"href":"https:\/\/www.shortform.com\/blog\/wp-json\/wp\/v2\/comments?post=72458"}],"version-history":[{"count":3,"href":"https:\/\/www.shortform.com\/blog\/wp-json\/wp\/v2\/posts\/72458\/revisions"}],"predecessor-version":[{"id":125524,"href":"https:\/\/www.shortform.com\/blog\/wp-json\/wp\/v2\/posts\/72458\/revisions\/125524"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.shortform.com\/blog\/wp-json\/wp\/v2\/media\/72511"}],"wp:attachment":[{"href":"https:\/\/www.shortform.com\/blog\/wp-json\/wp\/v2\/media?parent=72458"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.shortform.com\/blog\/wp-json\/wp\/v2\/categories?post=72458"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.shortform.com\/blog\/wp-json\/wp\/v2\/tags?post=72458"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}