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  • Writer's pictureJason Wang

Summary of "Light of the Stars"



Light of the Stars is a book written by the astronomer and physicist Adam Frank which discusses humanity’s place in the cosmos and was published in 2018. It is a remarkable, realistic, interesting read, for it characterizes humanity in a way that is rarely accomplished, as well as presenting a myriad of facts that informs the reader of the world.


To begin, Light of the Stars characterizes humanity as a teenager. Adam Frank writes that a major reason humanity acts foolishly in a way akin to that of an adolescent is due to the fact that we don’t have any extraterrestrial civilizations to learn from. Like teenagers who do group therapy to banish feelings of alienation and helplessness, humanity could greatly benefit with this hypothetical kind of “group therapy” with other civilizations which may also be confused with themselves, which is sadly impossible at the moment. Adam Frank writes that humanity, like teenagers, are pretty inexperienced when it comes to making wise choices, seeing how modern civilization lasted for only ten thousand years at the end of the last ice age. When the Scientific Revolution occurred, the human population exploded, seeing how “By 2011 CE, just about two centuries after reaching one billion, our numbers had climbed to seven billion. Today, even a modest-sized modern city houses more people than lived on the entire planet before the dawn of agriculture” (5). Frank writes that even though our influence has greatly increased, we also took great risks, seeing how carbon emissions, deforestation, and other man-made catastrophes are threatening the chance of our survival on the planet in the long run. Frank states that he believes that humans are definitely not the first intelligent civilization, considering how the only possible reason we are the only civilization as of yet is if the universe is strongly biased against life. Frank then goes back to teenagers and humanity as a species, writing that warning a teenager with statistics about the dangers of drunk driving will usually be ineffective, seeing how humans need more than numbers and data to truly register information. To be more specific, stories are some of the best mediums to communicate information, for they are supposed to be relatable. In the beginning of human civilization, religion provided stories, while now science, in the form of the Big Bang and evolution, does much of the talking.


Frank then corrects the misanthropic mindset some people have adopted when it comes to humanity, first describing the opinion of the other side: “When it comes to the fate of our civilization in a climate-changed world, however, we don’t have a big story that can convert rising global temperatures and melting Greenland ice sheets into a grand narrative with us in it. The only thing close is a story that goes something along the lines of ‘we suck.’ Human beings are greedy and selfish. We are nothing but a plague on the planet” (9). Frank then corrects that faulty perception, for he writes that the planet is not truly alive, and therefore cannot be wounded. He also states that the planet is perfectly fine - it’s the humans who are endangered. This goes along the lines of what George Carlin once ranted in a stand-up (the link is attached at the bottom). Frank elaborates in detail that being misanthropic and negative doesn’t help, and that, viewed from a bigger angle, is inaccurate: “People often cast the climate crisis in terms of ‘saving the planet.’ But as the biologist Lynn Margulis once put it, the Earth ‘is a tough bitch.’ It’s not the Earth that needs saving. Instead, it’s us and our project of civilization that need a new direction. If we fail to make it across the difficult terrain we face, the planet will just move on without us, generating new species in the novel climate states it evolves. The ‘we suck’ narrative makes us villains in a story that, ultimately, has none. What that story does have are experiments-the ones that failed and the ones that succeeded” (9). Frank then states that those who deny climate change are not pardoned at all from a large vantage point, for they are responsible for the future suffering which will occur due to carbon emissions. In his own words, those who deny climate change do so for egoism and selfishness, for their own personal gain - “They are fully culpable for their folly. From a planetary perspective and its long view, they will become the reason why Earth’s experiment in civilization building fails to reach its higher potential” (10). Before moving on to discuss biology, Frank writes that from this higher perspective, we are not villains but losers, and that no human is exempt from this judgement, for we all belong to the species collectively referred to as Homo Sapiens.


Frank talks about astrobiology, writing that after looking at earth's biological history, people began looking at other stars, and were amazed by what they saw there. Venus was found to be an extremely hot planet while Mars was a frozen wasteland. That is, “On Venus, 220-mile-per-hour winds blow high in the atmosphere. On Mars, icy fog forms each night near its northern pole. There’s even rain (made of gasoline) drifting over forty-mile-wide lakes on Titan, the giant moon of Saturn” (11). Frank writes about the Holocene, which occurred ten thousand years ago, and was characterized with marshlike conditions - the Holocene is “a planetary epoch of warm, wet conditions following the end of the ice ages” (12). He then provides a definition for the Anthropocene, which is mainly characterized by man-made climate change. Frank writes that humanity’s response towards the Anthropocene has been extremely disappointing as of yet, seen in widespread denial for five decades. He writes that every facet of human civilizations as of yet have proved themselves unable to truly tackle such a large issue, including politics, economics, and philosophy. Frank writes that two main questions he will tackle in the book are: (1) “What can the revolutions of astrobiology tell us about life on other worlds, even other intelligences and their civilizations?” and “What can life on other worlds, even other intelligences and their civilizations, tell us about our own fate?” (13). Frank briefly mentions aliens, writing that there needs to be boundaries when discussing them to prevent the discussion from regressing into UFO-conspiracy theories and fantasy stories.


Frank comes to discuss the Fermi Paradox. The Fermi Paradox seeks to answer the essential question: why have we not found aliens yet? It was posed by Enrico Fermi, an Italian who won the Nobel prize. Fermi, as could be expected, was a genius, mainly seen in his scientific creativity. Fermi asked where the aliens were while he was talking with three other scientists during lunch. The scientists eventually came to two conclusions. The first conclusion, labeled the “Great Silence,” is that no alien civilization in our nearby vicinity (the solar system) has evolved to the same level. The second conclusion, deemed the “Great Filter,” states that there is an evolutionary barrier which wipes out most technologically intelligent civilizations, hence the absence of extraterrestrials: “The Fermi Paradox only speaks to the existence of technological civilizations like ours, or ones even more advanced. Microbes or shellfish or even dinosaurs might exist on every world in the cosmos … if we are alone in the cosmos, then some kind of evolutionary wall blocks other planets from reaching our level” (25). Frank discusses the possibilities of the identity for the Great Filter. He states that perhaps the initial generation of life is the Great Filter, seeing that it does seem to be rare. Frank then provides some context for the situation, writing that as Fermi asked his famed question, the Cold War was occurring. Frank writes that it is very possible that the Great Filter involves how members of a civilization interact with each other, seeing how at that point in time (and even now, to some extent) humans were threatening each other with nuclear weapons. Frank writes that although nuclear weapons are a candidate, climate change is also one, for it happens everywhere and is a direct byproduct of our civilization’s use of energy.


Frank comes to discuss humanity’s beliefs in other worlds in history, beginning with the Greek philosopher Epicurus. Epicurus, more than two millennia ago, stated that there are an infinite amount of worlds in space due to it being infinite. Aristotle, on the other hand, wrote that a plurality of worlds was impossible. Aristotle went so far as to say that the Earth was at the center of the universe due to its uniqueness. The Catholic Church, upon its ascension to power, tried to prevent people from imagining other worlds. Thomas Aquinas stated that “God could have created other inhabited planets, but had chosen not to” (29). Copernicus soon wrote On the Revolution of Heavenly Spheres, published in 1543. The book had a large impact on how the earth was viewed, for while it didn't discuss the aforementioned heavenly spheres, it showed earth as being just another planet, not as anything special. The Catholic Church didn't immediately respond with repression, but when a Dominican monk, Giordano Bruno, argued that Copernicus was correct and that there were indeed many worlds, they burnt him at the stake for heresy in 1600. Eighty six years after Bruno’s execution, Bernard de Fontenelle published Conversations on the Plurality of Worlds. It was very optimistic, and included the idea that many of the planets orbiting the sun had inhabitants, including the moon. The Enlightenment saw optimism when it came to foreign worlds, but later on, the expectations were tempered by those who argued against the existence of alien civilizations. For instance, in 1853 William Whewell severely critiqued Of the Plurality of Worlds. In 1904, Alfred Russel Wallace, a major figurehead of the idea of evolution, wrote Man’s Place in the Universe, in which he stated that Earth was the only planet in the solar system which had life. He then argued that very few planets in the universe have conditions similar to that of Earth, which means that life is an exceptionally rare occurrence.


Frank Drake was the creator of Drake’s equation, an equation which attempts to predict the amount of alien civilizations there are in the cosmos. Before coming up with the equation, Drake launched Project Ozma, in which an observatory tried to pick up radio signals from outer space. No aliens were contacted in the project, but it sparked the curiosity of scientists. At the Great Bank Conference, an attempt was made to contact an alien civilization once again, and Drake’s equation was born. Drake’s equation includes the following variables: the birth rate of stars (N sub star), the fraction of stars with planets (fp), the number of planets that are just right for life (np), the fraction of planets with life forms (fi), the fraction of planets with a technological civilization (fc), and the average lifetime of a technological civilization (L). The equation goes as follows: N = (N sub star)(fp)(np)(fl)(fi)(fc)(L). When the equation became famous, Drake, like a true scientist, remained cautious and willing to learn, remarking that he was amazed at how prominent the equation became, since “‘it didn't take any deep intellectual effort or insight on my part. But then as now it expressed a big idea in a form that … even a beginner could assimilate” (51-2). Frank then writes that unlike Einstein’s e = mc2, the Drake equation is not a law of physics. Furthermore, the Drake equation “is really a statement of our lack of understanding. It tells us what we would need to know to get a specific answer to a specific question: How many exo-civilizations are out there?” (52).


Frank then describes the story of Jack James, an engineer from Texas who was given a strict deadline (less than fourteen months) to create and send a probe to Venus. In his first attempt to do so, he was extremely close, for the probe was just six seconds away from success before a safety officer was forced to blow it up due to technical issues. James, upon going back to his rented apartment, remembered the following quote: “‘To be a hero there are ten thousand parts that need to work properly on a spacecraft. To become a bum you just need one of them to fail” (63). Frank then wrote about Carl Sagan, the famed author of Cosmos and the corresponding TV series who attended the University of Chicago. Sagan, when it came to the topic for his own research, focused on how Venus became the way it was - a planet with extremely high temperatures that was a barren desert. Sagan then discovered that the greenhouse effect was to blame. Frank describes that the greenhouse effect is as follows: “Sunlight hitting a planet warms its surface. The warmed ground emits what is called heat radiation, which is just electromagnetic waves generated by the jiggling motions of heated atoms. Any object at any temperature above absolute zero spews heat radiation into its surroundings … For our planet’s temperature to remain steady and unchanging the energy flowing onto it must balance the energy flowing out … That means incoming solar energy and outgoing heat radiation energy must balance if the Earth’s temperature is to stay constant. Scientists call this balance the planetary equilibrium temperature” (68). Frank then states that an earth without the greenhouse effect will have no life, for the temperature will be around zero degrees Fahrenheit. Frank then states that Earth currently has the average temperature of 61 degrees Fahrenheit, and that most of the water is in liquid form. Frank credits the atmosphere for raising the temperature and for protecting life, as the rays of the sun carries a significant dosage of radiation for life forms. Frank writes ironically that in 1896, Swedish Nobel Prize-winning chemist Svante Arrhenius applied the greenhouse effect to Earth. He discovered (by today’s standards, he was very accurate) by analyzing coal “that human beings would eventually raise the planet’s temperature as we continued dumping CO2 into the air. His pencil-and-paper calculation predicted a global increase of about five degrees … In our current era of climate-change denial, it’s startling to recognize how far back the understanding of human-driven climate change begins” (69-70). Sagan applied Arrhenius’s application to Venus, and discovered that Venus was so hot because of a greenhouse effect that has gone haywire, seen in the atmosphere: “With its CO2-rich atmosphere, Venus was trapping enough energy to raise the surface temperature near to the staggering 600-degree level implied by NRL data. The planet was a cauldron because of the greenhouse effect” (70). This is a chilling lesson for all of humanity today, for climate change will soon be out of humanity’s influence, which means that once we’re past a certain level, disastrous side effects will occur regardless of our actions.


Engineer James was eventually successful in sending a probe to space, seen very well in the Mariner 2. Despite many technical difficulties, the probe was able to reach Venus, taking three months to do so. The findings confirmed Sagan’s findings, as “What emerged from these studies was a picture of a world where the CO2 greenhouse effect had run amok” (72). To be more specific, Frank writes that “At some point, Venus likely had more water. It may even have had oceans and been hospitable to life. But when some of that water evaporated, it made its way high into the atmosphere, where a deadly process began. Close to the edge of space, ultraviolet radiation from the Sun (the same kind that causes skin cancer) zapped the water molecules and broke them apart into hydrogen and oxygen. Hydrogen, being the lightest of all elements, easily escaped into interplanetary space as soon as the water molecules were broken apart. With the hydrogen gone, there was no chance for the broken water molecules to reform. Over time, and high in its atmosphere, Venus was bleeding its precious water into space” (73). This led to a positive feedback loop, for “More water loss meant less rock erosion and less CO2 bound up in rocks. More CO2 in the atmosphere meant a more pronounced greenhouse effect and higher temperatures. But higher temperatures meant more water loss” (73-4). Frank comes to discuss Mars, writing of how some people like Percival Lowell once believed that there was an extraterrestrial civilization on Mars. While they were proven to be inaccurate, it was discovered by spacecraft sent there, such as the Mariner 9, that Mars had channels on its surface, hinting at the existence of water. The Viking landers (worked on by Carl Sagan and other scientists) were sent to Mars, and they discovered that while “Venus had a lot more atmosphere than our planet, Mars has a lot less” (86). The atmospheres of both worlds largely reflected their nature - Venus’s excessive atmosphere reflected a planet carried away with the greenhouse effect, while Mars’s atmosphere is 99% less heavy than that of Earth, reflecting that Mars had no greenhouse effect. Consequently, “Typical nighttime lows go down to -128 degrees Fahrenheit, while daytime highs only get as high as -24 degrees Fahrenheit … It’s also a desert. There’s very little water in Mars’s atmosphere-just 0.01 percent of what’s found in Earth’s. Since the atmospheric pressure is so low, exposed liquid water boils away in seconds” (86-7). Frank then connects this to our biology, writing that if you were on Mars and your spacesuit failed, you would die rapidly either from asphyxiation or hypothermia. Mars, despite all its differences with Earth, is still very similar. For instance, Mars is spinning too, and has predictable wind patterns. It also has a day that lasts for 24.7 hours. Frank writes that physics illustrates the laws of the universe, and this includes climate: “All worlds obey the same rules: Earth, Mars, Venus, even an exoplanet a hundred light-years away. Most importantly, they are rules that we now understand because we’ve seen them working on more than one planet” (88-9).


Frank then writes that Earth, like everything in the universe, changes over time. He writes that earth had many “masks” before, for it resembled many planets in the past. That is, “These other versions of Earth were profoundly different from the cloud-mottled, blue-green world we know today. Each was a consequence of planetary forces shaping and then reshaping our world. Together, they reveal how deeply humans and our project are part of a much longer story. When it comes to life changing the planet, we are neither unique nor unusual” (100). Frank then writes of Greenland, stating that its ice sheets provide a fantastic record of the temperature of the planet, and some of the patterns illustrate rapid climate change. In one instance, it shows climate change that occurred twelve thousand years ago. Frank then writes of Earth’s history, describing how “The planet’s story begins with an unnamed cloud of interstellar gas and dust. Almost five billion years ago, that slowly spinning cloud, close to a light-year across, collapsed under its own weight. The Sun formed at the center of the infalling mass, and a rapidly spinning disk surrounding the young star emerged as well. Within this dense disk, particles of dust began colliding frequently enough to form free-floating pebbles. Those pebbles then collided to form rock-sized objects. The rocks then collided to form boulders, and so on, all the way up to asteroid-sized planetesimals. After between ten million and a hundred million years, gravity drew the planetesimals together and assembled the Earth and other rocky planets (Mercy, Venus, and Mars).” (109). Frank then states that Earth’s first eon, deemed the Hadian, lasted from 4.6 billion to 4 billion years ago (beginning with the formation of the earth). Frank writes that as the name suggests, the Earth was like Hades back then, for it “was covered in a globe-spanning sea of molten rock. Eventually, this magma ocean cooled and hardened, forming a solid surface. But asteroids and comets continued to rain down on the planet, ending in a period called the Late Heavy Bombardment, when our solar system cleared itself of planetary construction debris. Each of these apocalyptic impacts shattered the surface, turning some or all of it back into molten rock. Gases released from the bombardment and the magma oceans it regenerated left the Hadean Earth with an atmosphere composed mostly of nitrogen and carbon dioxide” (109-110). Frank then writes of the Archean time period, which lasted from 4 billion to 2.5 billion years ago. It was in this time period that DNA became a widespread phenomena, spreading across the world. During this time period, life was comprised only of basic, single-celled organisms which lived in water, seeing that at the time the vast majority of the planet was covered by oceans. Frank then writes that during the Archean time period, most of the landmasses have not been formed yet, and that “the continent making was still beginning,” for “Rather than planet-spanning continents, the world hosted just one or two proto-continents called cratons. Each craton was smaller than India is today” (110).


Frank then writes of the Proterozoic eon, which lasted from 2.5 billion to 0.5 billion years ago. In this time period some prokaryotes (the earliest cells) began using the sun for its fuel source, causing photosynthesis to come into existence. Eukaryotic cells came into existence once certain cells became refined at using sunlight, and it was also during this time period that the first complex bodies were formed, seeing that “The first multicellular organisms appeared during the Proterozoic, as life began to experiment with the division of labor. Cells specialized into different forms that worked together. Left without the larger organism, however, these specialized cells would die” (111). It was also during this time period that the cratons morphed into the continents, as the movement of tectonic plates caused them to compose a supercontinent named Rodinia. Numerous ice ages also occurred during the Proterozoic eon, seeing how “At least four times during this eon, changes in the concentrations of atmospheric greenhouse gases plunged planetary temperatures into the freezer … the entire planet may have become locked in miles-thick layers of ice. Seen from space, this snowball world would have appeared as a mottled and cracked Ping-Pong ball with no large expanses of open blue water” (112). Frank then writes of the beginning of the Phanerozoic, and how a massive flourishing of diversity occurred largely out of nowhere 540 million years ago: “Across a remarkably short span of geological time, evolution threw itself a party. What began as still-simple multicellular life rapidly diversified into an orgy of new forms and new species. In just fifty million years, evolution produced all the basic structures that mark life on Earth today. Called the Cambrian Explosion (it occurred during the Cambrian geologic era), it was an evolutionary acceleration on a scale never seen before or after” (112). Then there was the Carboniferous era, which occurred three hundred million years ago, and was mainly characterized by swampy forests which later became coal after millions of years of geology. After that came the Jurrasic era, which was mainly characterized by dinosaurs. After that, there was a cycle of ice ages and interglacial periods, which saw the existence of humans. Pangaea split apart fifty-five million years ago, and “The volcanism that accompanies plate tectonics went into overdrive, dumping CO2 into the atmosphere far faster than it could be removed by natural feedbacks … Called the Paleocene-Eocene Thermal Maximum, the result was a planet almost without ice. Temperatures in Greenland … stayed at a balmy 70 degrees Fahrenheit” (113). As illustrated, the planet is a very flexible landmass, for it went through many drastic changes, beginning as a “fire world of molten seas,” becoming “a water world of almost endless ocean,” morphing into “a snowball world of endless ice,” gradually becoming “a sweltering hothouse planet devoid of snow,” and then into the world which we are accustomed to today. This ties back to Frank’s (and George Carlin’s) statement that the planet is fine - it has gone through much worse than us, and it isn’t even “alive” in the traditional sense, seeing how it merely harbors life. To reiterate, humans are the ones in danger, not the planet. We are not trying to save the planet, merely ourselves (and so far, we have failed even in that area, which seriously calls into question our “intelligence”).


Frank then writes of the Great Oxidation Event. In this massive event, the entire workings of biology were completely altered, making it extremely important. What happened in this phenomenon was the creation of cyanobacteria, which utilized oxygen to survive. They appeared as blue-green algae: “By the middle of the Archean, however, at least some single-celled organisms had figured out how to tap a new and abundant energy source: sunlight. The first emergence of photosynthetic organisms in the form of what scientists call anoxygenic phototrophs (non-oxygen-producing sunlight eaters) was a major innovation in the history of life. Through the remarkable trial and error of evolution (and lots of time), some bacteria developed molecular light receptors” (116). After a billion years of non-oxygen-producing photosynthesis, “evolution produced a new version of photosynthesis won out over the older forms-called cyanobacteria … did more than just multiply. Sucking in water, CO2, and sunlight, they also started spitting out molecules of oxygen as a kind of waste product of their activity … Over time, the activity of the cyanobacteria dumped so much oxygen into the ocean and atmosphere that the entire planet was forced to respond … Across just a few hundred million years, the concentration of atmospheric oxygen increased by a factor of a million” (116). Frank then writes that at the time, oxygen was toxic for most living organisms, which caused the vast majority to die. However, oxygen was better for complex organisms, seeing that oxygen’s chemistry is compatible with higher life forms, seen in metabolism. By the end of the Great Oxidation Event, “the anoxygenic phototrophs, once the planet’s masters, had been forced into oxygen-free warrens … In this way, the new oxygen-breathing forms of life inherited the open sea and open sky” (117). The Great Oxidation Event clearly shows the effect organisms can have on the entire planet, a relevant message.


Frank then writes of the Gaia theory, created by James Lovelock and Lynn Marguilis. In this theory, they described the earth in a scientific narrative as being akin to that of a living organism, as when various life forms do various activities, the planet reacts. The idea was harshly criticized by scientists, as most didn't view earth as behaving like a living organism, but the impact was there, for it showed the interconnectedness of various factors of Earth, seen in the term “coevolution.” Frank then writes of Thomas Jefferson Jackson Sea, an astronomer. Although he was a scientist, he lacked skepticism, effectively ruining his career. The idea which ruined his career was his claiming that planets orbited stars. When he was ridiculed by his colleagues, he refused to admit his fallibility, instead choosing to further support his ideas. The main reason why scientists felt the whole idea was ridiculous was that planets were extremely small compared to stars (compare the Earth to the sun, for instance), and that to make such an observation requires a powerful telescope. Frank then writes of pessimistic estimates for the probability of life, stating that he and a colleague, Woody Sullivan, found that the chance that humanity is the only civilization as of yet is 10-22, or one in ten billion trillion. The first pessimist introduced in the book includes Ernst Mayr, “a brilliant scholar who was instrumental in linking classical ideas from Darwin to the revolution in genetics that occurred after the discovery of DNA” who “never bought Carl Sagan’s optimism about SETI or the existence of other intelligent forms of life” (160). He says that he thinks that the probability of a civilization evolving on any given planet is one in a thousand trillion. If that is to be taken as accurate, that would mean humanity is the only civilization in our galaxy. However, then there’s the universe - “To be exact, even if Mayr is correct, there will still have been ten million high-tech civilizations appearing across space and time” (161). Frank puts that number into perspective, writing that “If you tried to imagine the history of each of these civilizations, giving each one an hour of your time, it would take 1,140 years to get through them all. That’s how many exo-civilizations would have existed in what Mayr thought to be a pessimistic universe” (162). Frank then writes of Brandon Carter, who is known for mentioning the fact that many intelligent civilizations (like humanity) may come into existence near the end of the habitability of their planets. He puts the probability of alien life as 10-20, which still means one hundred exo-civilizations exist. As Frank writes, “Carter intended his calculation to be hyper-pessimistic, but it turns out to be optimistic instead … It should also be noted that researchers who have followed Carter’s line of reasoning now believe only five hard steps exist, if any exist at all. This consideration, combined with the other values in Carter’s original paper, implies a biotechnical probability of 10-10. Compare that with our pessimism line, and you end up with a trillion exo-civilizations across cosmic history” (163).


Frank then writes of an extreme pessimist, Hubert Yockey. Yockey, a physicist and information theorist, writes that the possibility of life developing is 10-65. If that is accurate, then humanity will indeed probably be the only time a civilization has come into existence. Frank then writes that Yockey’s position does have potential flaws, as “biologist Wentao Ma and collaborators used computer simulations to show that the first replicating molecules could heaven short strands of RNA (a molecule closely related to DNA and an integral part of cellular machinery). These are much easier to form than what Yockey was thinking about … Yockey’s hyper-hyper-pessimism seems to be an outlier in the debate about alien life” (164). Frank writes that one does not have to believe in alien civilizations to see their thought processes as being scientific, since science encourages doubt and agnosticism. He writes once more that we have to view our planet as not being an isolated phenomenon, but as an area affected by the same laws that apply to other planets. Frank then writes of the rise and fall of human civilizations, and he draws from research involving populations, clearly illustrating that the vast majority of species on earth (including Homo Sapiens) have no accurate idea when to stop reproducing, even when levels become absurd. As a result, the population is then decreased through the widespread deaths of many individuals in the species due to things like massive starvation. Frank gives the example of Easter Island to illustrate this instance. Eastern Island, famous for its large statues, once had a vibrant, powerful civilization. Their downfall, for all their resources, consisted of overpopulation and resource depletion. Frank describes it best: “As the population grew, the resources could not keep up. Overharvesting pulled resources down, and eventually, the island’s inhabitants went with them. Peaking sometime around 1200 CE, the human population of Easter Island then experienced a gradual die-off, ending with just a few thousand inhabitants left by the time the Dutch arrived. The mathematical model got the general trend in the history right” (183). Frank then gives a brilliant analogy: Easter Island is to Earth as Earth is to space - Easter Island and Earth are indeed islands, just in different ways. While Easter Island is geographically an island (making resource sustainability extremely important), Earth is a mere speck in space, isolated from other planets. We, as a species, are lost in the sea of space and time.


Frank then discusses how to conduct theoretical archeology of exo-civilizations, providing the following factors to take into account: (1) other civilizations, other histories (we’re probably not the first intelligent civilization), (2) it’s all about the averages (ex. Drake’s final factor - how long does a civilization last?), (3) there is no free lunch (carbon emissions escaping the atmosphere, seen in the Second Law of Thermodynamics, which states that all energy can’t be converted efficiently, directly leading to waste products), (4) “Planets come with a Limited Number of Energy Sources” (different types of energy resources include combustion, hydro/wind/tides - anything that involves the movements of fluids or gases of the planet, geothermal energy - heat, solar energy - high-tech type is seen in electric current and low-tech type is seen in heat, nuclear energy), knowing the impact of the various modes of energy, and creating various models in the form of equations. Frank writes that he and some other scientists created models using mathematics, and that all of them involve a population peak and climate change. There are four kinds of outcomes. The first is the die-off, in which the population increases dramatically with initial energy use, but then plummets due to the planetary temperature changing. The second option is a more sustainable one, in which population size is managed, thereby controlling the planetary temperature. The population then remains stable. In the third option, collapse without resource change, the population increases, but when planetary temperature becomes unmanageable, the species becomes extinct (or close to extinct, anyhow). In the fourth option, collapse with resource change, the population increases and eventually adopts change in energy management. However, the said species suffers the same fate as those in the third option, seeing how sometimes planetary temperature can’t be controlled (once a certain level is reached), causing the species to go extinct. Frank writes about the last option that “Once the ball got rolling, the planet’s own internal machinery took over. It wasn’t going back to the original climate state, and it took the civilization down with it as it ran away into a new state. In these cases, the planetary environment’s own dynamics were the culprit. Push a planet too hard, and it won’t return to where it began” (198). This is seen particularly well with the current period, the Anthropocene, as human climate change is already irreversible in some regards (we can still mitigate the damage, though, but don’t count on it anytime soon). Frank illustrates in a sobering graph on page 199 that CO2 concentrations, the global population, and world energy consumption has only increased since the Industrial Revolution, with massive growth occurring in the last few decades as humans reproduced in ever-greater numbers (which illustrates what Frank said about species being unable to act in their own long-term self-interest, as the sheer strength of sexual urges are never to be underestimated, even when compared to our potential rationality).


Frank then writes of the Kardashev Scale, which was invented by Nikolai Kardashev, a Russian scientist, to describe how advanced a civilization is. The scale itself is very influential in theoretical science, and is engrossing to examine. According to the scale, there are three types of civilizations. Type 1 civilizations have the capability of utilizing all the energy resources of the home planet. Although that may not sound like much to some, it should be remembered that “In practice, this means capturing all the light energy that falls on the world from its host star, since stellar energy will likely be the largest source available on a habitable-zone planet. The Earth receives the equivalent of thousands of atomic bombs’ worth of energy from the Sun every second” (209). To put this into perspective, human civilization isn’t even Type 1, as we are far from using all our local energy efficiently. Type 2 civilizations are capable of utilizing the energy of their home stars. That is, “The total output of the Sun every second is a billion times larger than the sunlight that falls just on Earth. The physicist Freeman Dyson anticipated some of Kardashev’s thinking in a paper written in 1960, in which he imagined an advanced civilization constructing a vast sphere around its star” (209). Type 3 civilizations are extremely advanced, for they could use all the energy in their galaxy. Frank writes that the Kardashev scale is so influential because it combines science and optimism, and that “In 1976, Carl Sagan suggested a way of calculating ‘fractional’ values of Kardashev status based on world energy production. In Sagan’s calculation, we end up at about Type 0.7. Freeman Dyson went further, suggesting that human civilization will reach full Type 1 status in approximately two hundred years (with Type 2 requiring another hundred thousand to one million years).” (211).


Frank then writes of thermodynamics, describing that he and his colleagues grouped planets into five categories. Class 1 is made of airless worlds (ex. Mercury - “truly dead worlds”), Class 2 involves planets with an atmosphere but no biology (ex. Mars and Venus - “The flow of gases and liquids driven by sunlight represent work being done within the planetary systems”), Class 3 has planets which have thin biospheres, where life has just begun, Class 4 worlds are dominated by life (“They have ‘thick’ biospheres that are deep networks of animal, plants, and microbes, all feeding on each other and all feeding back onto the other planetary systems”), and Class 5 worlds have civilizations which try to survive by using energy wisely (“The civilization makes choices with goals in mind. Thus, Class 5 planets have agency-dominated biospheres. The civilization is now deliberately working with the rest of the natural systems to increase the flourishing and productivity of both itself and the biosphere as a whole”) (217-9). Frank writes that the Earth is leaving the Class 4 category due to human activity and may never be a Class 5 planet, making it a hybrid planet. Frank writes tellingly of what a Class 5 planet should look like, describing that the civilizations should try to survive on their planet through wise methods: “To truly come into a cooperative coevolution with a biosphere, a technological civilization must make technology-the fruit of its collective mind-serve as a web of awareness for the flourishing of both itself and the planet as a whole” (221).


Frank ends his book by writing that science has shown humanity its place in the cosmos, and that humanity has probably been dwarfed by previous civilizations. He then writes that if humans continue to commit our current follies by using nonrenewable energy and living an overly extravagant and consumerist lifestyle, “we’ll push the planet into domains that prove difficult for our kind of complex global civilization,” and that the planet, being utterly indifferent to our needs, would “happily move on without us” (223). Frank again states that environmentalists and like-minded individuals should change their wording, for they are not attempting to save the planet, but themselves. Frank finally states that people should stop wrangling about whether or not humans created civilization; instead, they should focus on how to improve the civilization - “creating climate change wasn’t done with malevolence. We are not a plague on the planet. Instead, we are the planet. We are, at least, what the planet is doing right now. But that is no guarantee that we’ll still be what the planet is doing one thousand or ten thousand years from now” (225). Frank ends his book with the following paragraph, which, in my opinion, is as inspiring as Sagan’s speeches, for it puts our civilization into perspective: “As children of the Earth, we are also children of the stars … Through the light of the stars, through what they can teach us about other worlds and the possibilities of other civilizations, we can learn what path through adolescence we must take. And in that way, we can reach our maturity. We can reach our full promise and possibility. We can make the Anthropocene into a new era for both our civilization and the Earth. In the end, our story is not yet written. We stand at a crossroads under the light of the stars, ready to join them or ready to fail. The choice will be our own” (225).


Personal thoughts:

Light of the Stars, like Cosmos, is a great book. Not only does it show humanity in the big picture, but it also seeks to inspire people to hope for the future. I appreciate that Frank takes time to explore humanity’s relationship with the rest of the planet, seen in how he dispels two common myths: the belief that humans are like a plague and that the planet warrants saving. The examples, studies, and scientists which Frank outlines help show the topic in all its detail, which is much appreciated. The lessons which this book and similar ones have for our civilization is of the essence, as humanity is already well into the Sixth Extinction, and by the end of this century, climate change would most likely be ravaging the human race, putting our survival in jeopardy. I highly recommend Light of the Stars to anyone interested in space, humanity’s place in the cosmos, science, and scientists.


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