Climate Change: What is the Worst that can Happen?

A Brontotherium, a creature similar to modern rhinos that lived up to some 35 million years ago in a world that was about 10 degrees centigrade hotter than ours. In this scene, we see a grassy plain, but Earth was mostly forested at that time. We may be moving toward similar conditions, although it is not obvious that humans could fare as well as Brontotheria did (image from BBC).

 

As it should have been predictable, the IPCC 6th assessment report, sank like a stone to the bottom of the memesphere just a few days after it was presented. Put simply, nobody is interested in sacrificing anything to reverse the warming trend and, most likely, nothing will be done. Renewable energy offers hope to mitigate the pressure on climate, but it may well be too late. We may have passed the point of non-return and be in free fall toward an unknown world. 

A disclaimer: I am not saying that nothing can be done anymore. I think we should keep doing what we can, as long as we can. But, at this stage, we can ask the question of "what is the worst thing that can happen?" Models can't help us too much to answer it. Complex systems -- and Earth's climate is one -- tend to be stable, but when they pass tipping points, they change rapidly and unpredictably. So, the best we can do is to imagine scenarios based on what we know, using the past as a guide.

Let's assume that humans keep burning fossil fuels for a few more decades, maybe slowing down a little, but still bent at burning everything burnable, deforesting what is deforestable, and exterminating what is exterminable. As a result, the atmosphere keeps warming, the ocean does that, too. Then, at some point -- bang! -- the concentrations of greenhouse gases shoot up, the system goes kinetic and undergoes a rapid transition to a much hotter world.

The new state could be similar to what the Earth was some 50 million years ago, during the Eocene. At that time, the concentration of CO2 in the atmosphere was of the order of one thousand parts per million (today it is ca. 400) and average surface temperature was about 10-12 degrees C higher than the current one. Note that this is an average: the high latitudes, North and South, where hotter than the low ones, nowhere life would experience temperatures so high that animals would boil alive. So, it was hot, but life thrived and Earth was a luxuriant, forested planet. In principle, humans could live in an Eocene-like climate. The problem is that getting there could be a rough ride, to say the least.

Nobody can say how fast we could get to a new Eocene, but tipping points are fast, so we don't need millions of years. We are thinking, more likely, of thousands of years and significant changes could occur in centuries or even in decades. So, let's try an exercise in looking at the worst-case hypothesis: assuming a warming of 5-10 degrees occurring over a time span of the order of 100-1000 years, what would we expect? It depends not just on temperatures, but on the interplay of several other factors, including mineral depletion, economic and social collapse, and the like. Let me propose a series of scenarios arranged from not so bad to very bad. Remember, these are possibilities, not predictions.

1. Extreme weather events: hurricanes, and the like. These events are spectacular and often described as the main manifestation of climate change. Nevertheless, it is not obvious that a warmer world will show violent atmospheric phenomena. A hurricane is a thermal engine, it transfers heat from a hot area to a cold area. It is more efficient, and hence more powerful, the higher the temperature difference. From what we know, in a warmer world these differences should be lower than they are now, at least horizontally, although vertically it is another matter. Overall, the power of hurricanes would not be necessarily increased. We may have a lot more rain because a hot atmosphere can contain more water, and this is an already detectable trend. Extreme weather events would be mainly local and hardly an existential threat to human civilization. 

2. Fires. Higher temperatures mean higher chances of fire, but the temperature is not the only parameter that enters into play. The trends over the past decades indicate a weak increase in the number of fires in the temperate zone and, of course, fires wreak havoc for those who didn't think too much before building a wooden house in a forest of eucalyptus trees. Nevertheless, as far as we know, fires were less common in the Eocene than they are now, which is what we would expect for a world of tropical forests. Fires should not be a threat for the future, although we may see a temporary rise in their frequency and intensity during the transition period.

3. Heat Waves. There is no doubt that heat waves kill, and that they are becoming more and more frequent. An Eocene-like climate would mean that the people living in what is today the temperate zone would experience summers in the form of a continuous series of extreme heat waves. Paris, for instance, would have a climate similar to the current one in Dubai. It would not be pleasant, but it is also true that people can stay alive in Dubai in Summer using air conditioning and taking other precautions. As long as we maintain a good supply of electricity and water, heat waves don't represent a major threat. Without electricity and abundant water, instead, disaster looms. Heat waves could force a large fraction of the population in the equatorial and temperate zones to move northward or relocate on higher grounds, or, simply, die where they are. The toll of future heat waves is impossible to estimate, but it could mean the death of millions or tens of millions of people, or even more. It may not destroy civilization, but humans would have to move away from the tropical regions of the planet

4. Sea level rise. Here, we face a potential threat that goes from the easily manageable to the existential, depending on how fast the ice sheets melt. The current 3.6 mm/year rate means 3-4 meters of rise in a thousand years. Over such a time span, it would be reasonably possible to adapt the harbor structures and to move them inland as the sea level rise. But if the rate increases, as it is expected to, things get tough. Having to rebuild the whole maritime commercial infrastructure in a few decades would be impossible, to say nothing about the possibility of catastrophic events involving large masses of ice crashing into the sea. If we lose the harbors, we lose the maritime commercial system. Without it, billions of people would starve to death. In the long run, the ice sheets of Greenland and Antarctica will have to melt completely, causing the sea level to rise by about 70 meters, but nobody can say how long that would take. Sea level rise has the potential for substantial disruption of the human civilization, even for its total collapse, but not to cause the extinction of humankind.

5. Agricultural collapse. In principle, climate change, may have disruptive effects on agriculture. Nevertheless, so far warming has not affected agricultural productivity too much. Assuming no major changes in the weather patterns, agriculture can continue producing at the current rates as long it is supplied with 1) fertilizers, 2) pesticides 3) mechanization, 4) irrigation. Take out any one of these 4 factors and the grain fields turn into a desert (genetically modified organisms (GMOs) may not need pesticides, but they have other problems). Keeping this supply needs a lot of energy and that may be a big problem in the future. Photovoltaic-powered artificial food production could come to the rescue, but it is still an experimental technology and it may arrive too late. Then, of course, technology can do little against the disruption of the weather patterns. Imagine that the Indian yearly monsoon were to disappear: most likely, it would be impossible to replace the monsoon rain with artificial irrigation and the result would be hundreds of millions of people starving to death. The lack of food is one of the main genocidal killers in history, directly or indirectly as the result of the epidemics that take advantage of weakened populations. As recently as a century and a half ago, famine directly killed about 30% of the population of Ireland and the toll would have been larger hadn't some of them been able to emigrate. If we extrapolate these numbers to the world today, where there is no possibility to migrate anywhere (despite Elon Musk's efforts to take people to Mars), we are talking about billions of deaths. Famines are among the greatest threats to humankind in the near future, although climate change would be only a co-factor in generating them. Famines may wreck sufficient damage to cause an economic, social, and cultural collapse. 

6. Ecosystem collapse. The history of Earth has seen several cases of ecosystemic collapses involving mass extinctions: the main ones are referred to as "the big five." The largest one took place at the end of the Permian, about 250 million years ago. In that case, the ecosystem recovered from the catastrophe, but it went close to losing all the vertebrates. Most large extinctions are correlated to volcanic emissions of the type called "large igneous provinces" that generate large amounts of greenhouse gases. The result is a warming sufficiently strong to disrupt the ecosystem. The current human-caused emission rate is larger than anything ever experienced by the ecosystem before, but it is unlikely to arrive to levels that could cause a Permian-like disaster. While volcanoes don't care about the biosphere, humans would be wiped out much before they could pump enough CO2 in the atmosphere to cause the death of the biosphere. Nevertheless, a substantial ecosystemic collapse could be caused by factors as the elimination of keystone species (say, bees), erosion, heavy metal pollution, arrest of the thermohaline oceanic currents, and others. The problem is that we have no idea of the time scale involved. Some people are proposing the "near term human extinction" (NTE) taking place in a few decades at most. It is not possible to prove that they are wrong, although most of the people studying the issue tend to think that the time involved should be much longer. The collapse of the ecosystem is a real threat: if it has happened in the past, it could happen again in the future. It may not be definitive and the ecosystem would probably recover as it has done in the past. But, if it happens, it may well be the end of humans as a species (and of many other species). 

7, The unexpected. Many things could cause an abrupt and unexpected change of the state of the system. The stopping of the thermoaline currents is a threat that could wreck disaster on the biosphere, but we don't know exactly what could happen, despite spectacular movies such as "The day after tomorrow"). Then, concentrations of CO2 of the order of 1,000 ppm could turn out to be poisonous for a biosphere that evolved for much lower concentrations. That would lead to a rapid ecosystem collapse. Then, heavy metal pollution could reduce human fertility so much that humans would go extinct in a couple of generations (we are especially sensitive to pollution because we are top predators). In this case, the human perturbation on climate would quickly disappear, although the past effects would still be felt for a long time. Or, we may think of a large scale nuclear war. It would cause a temporary "nuclear winter" generated by the injection of light-reflecting dust into the atmosphere. The cooling would disrupt agriculture and kill off a large fraction of the human population. After a few years, though, warming would return with a vengeance. How about developing an artificial intelligence so smart that it decides that humans are a nuisance and it exterminates them? Maybe it would keep some specimens in a zoo. Or, a silicon-based life would find that the whole biosphere is a nuisance, and proceed to sterilize the planet. In that case, we might be transferred as virtual creatures in a virtual universe created by the AI itself. And that may be exactly what we are! These extreme scenarios are unlikely, but who knows?

 

So, this is the view from where we stand: the peak of the Seneca Cliff, the curve that describes the rapid phase transitions of complex systems on the basis of the principle that "growth is sluggish, but ruin is rapid." We see a green valley in the distance, but the road down the cliff is so steep and rough that it is hard to say whether we will survive the descent. 

The most worrisome thing is not so much the steep descent in itself, but that most humans not only can't understand it, but they can't even perceive it. Even after the descent has started (and it may well have started already), humans are likely to misunderstand the situation, attribute the change to evil agents (the Greens, the Communists, the Trumpists, or whatever) and react in way that will worsen the situation -- at best with extensive greenwashing, at worst with large scale extermination programs.

So, we may well disappear as a species in a non remote future. But we may also survive the disaster and re-emerge on the other side of the climate transition. For those who make it, the new Eocene might be a good world to live in, warm and luxuriant, with plenty of life. Maybe some of our descendants will use stone-tipped lances to hunt a future equivalent of the ancient Eocene's brontotheria. And, who knows, they might be wiser than we have been. 

Whether humans survive or not, the planetary ecosystem -- Gaia -- will recover nicely from the human perturbation, even though it may take a few million years for it to regain the exquisite complexity of the ecosystem as it was before humans nearly destroyed it. But Gaia is not in a hurry. The Goddess is benevolent and merciful (although sometimes ruthless) and she will live for several hundred million years after that even the existence of humans will have been forgotten.

 

Stereocene: The Future of Earth's Ecosytsem

Here is a post that appeared four years ago on "Cassandra's Legacy" and that I think is worth republishing here, on "The Seneca Effect," after some minor revisions. It is part of a series of rather speculative posts on the future of humankind and of the universe. Here are the links to the series

The Next Ten Billion Years

Star Parasites

The Long-Term Perspectives of Nuclear Energy

The Great Turning Point For Humankind: What if Nuclear Energy had not been Abandoned? 

 

______________________________________________________________________________

Stereocene: The Future of  Earth's Ecosystem

 During the "golden age" of science fiction, a popular theme was that of silicon-based life. Above, you can see a depiction of a silicon creature described by Stanley Weinbaum in his "A Martian Odyssey" of 1934. The creature was endowed with a metabolism that would make it "breathe" metallic silicon, oxidizing it to silicon dioxide, hence it would excrete silica bricks: truly a solid-state creature. It is hard to think of an environment where such a creature could evolve, surely not on Mars as we know it today. But, here, on Earth, some kind of silicon-based metabolism seems to have evolved during the past decades. We call it "photovoltaics." Some reflections of mine on how this metabolism could evolve in the future are reported below, where I argue that this new metabolic system could usher a new geological era which we might call "Stereocene", the era of solid-state devices.

 

What Future for the Anthropocene? A Biophysical Interpretation 

An abridged version of a paper published in 2016 in 
"Biophysical Economics and Resource Quality"

Ugo Bardi
Dipartimento di Chimica - Università di Firenze

The history of the earth system is normally described in terms of a series of time subdivisions defined by discrete (or “punctuated”) stratigraphic changes in the geological record, mainly in terms of biotic composition (Aunger 2007a, b). The most recent of these subdivisions is the proposed “Anthropocene,” a term related to the strong perturbation of the ecosystem created by human activity. The starting date of the Anthropocene is not yet officially established, but it is normally identified with the start of the large-scale combustion of fossil carbon compounds stored in the earth’s crust (“fossil fuels”) on the part of the human industrial system. In this case, it could be located at some moment during the eighteenth century CE (Crutzen 2002; Lewis and Maslin 2015). So, we may ask the question of what the evolution of the Anthropocene could be as a function of the decreasing availability of fossil carbon compounds. Will the Anthropocene decline and the earth system return to conditions similar to the previous geologic subdivision, the Holocene?

The Earth system is a nonequilibrium system whose behavior is determined by the flows of energy it receives. This kind of systems tend to act as energy transducers and to dissipate the available energy potentials at the fastest possible rate (Sharma and Annila 2007). Nonequilibrium systems tend to attain the property called “homeostasis” if the potentials they dissipate remain approximately constant (Kleidon 2004). In the case of the Earth system, by far, the largest flow of energy comes from the sun. It is approximately constant (Iqbal 1983), except for very long timescales, since it gradually increases by a factor of about 10 % per billion years (Schroeder and Connon Smith 2008). Therefore, the earth’s ecosystem would be expected to reach and maintain homeostatic conditions over timescales of the order of hundreds of millions of years. However, this does not happen because of geological perturbations that generate the punctuated transitions observed in the stratigraphic record.

The transition that generated the Anthropocene is related to a discontinuity in the energy dissipation rate of the ecosystem. This discontinuity appeared when the ecosystem (more exactly, the “homo sapiens” species) learned how to dissipate the energy potential of the carbon compounds stored in the earth’s crust, mainly in the form of crude oil, natural gas, and coal). These compounds had slowly accumulated as the result of the sedimentation of organic matter mainly over the Phanerozoic era over a timescale of the order of hundreds of millions of years (Raupach and Canadell 2010). The rate of energy dissipation of this fossil potential, at present, can be estimated in terms of the “primary energy” use per unit time at the input of the human economic system. In 2013, this amount corresponded to ca. 18 TW (IEA 2015). Of this power, about 86 % (or ca. 15 TW) were generated by the combustion of fossil carbon compounds.

The thermal energy directly produced by combustion is just a trigger for other, more important effects that have created the Anthropocene. Among these, we may list as the dispersion of large amounts of heavy metals and radioactive isotopes in the ecosphere, the extended paving of large surface areas by inorganic compounds (Schneider et al. 2009), the destruction of a large fraction of the continental shelf surface by the practice known as “bottom trawling” (Zalasiewicz et al. 2011), and more. The most important indirect effect on the ecosystem of the combustion of fossil carbon is the emission of greenhouse gases as combustion products, mainly carbon dioxide, CO2, (Stocker et al. 2013). The thermal forcing generated by CO2 alone can be calculated as approximately 900 TW or about 1 % of the solar radiative effect (Zhang and Caldeira 2015), hence a nonnegligible effect that generates an already detectable greenhouse warming of the atmosphere. This warming, together with other effects such as oceanic acidification, has the potential of deeply changing the ecosystem in the same way as, in ancient times, LIPs have generated mass extinctions (Wignall 2005; Bond and Wignall 2014).

Burning fossil fuels generate the exergy needed to create industrial structures which, in turn, are used to extract more fossil fuels and burn them. In this sense, the human industrial system can be seen as a metabolic system akin to biological ones (Malhi 2014). The structures of this nonbiological metabolic system can be examined in light of concepts such as “net energy” (Odum 1973) defined as the exergy generated by the transduction of an energy stock into another form of energy stock. A similar concept is the “energy return for energy invested” (EROI or EROEI), first defined in 1986 (Hall et al. 1986) [see also (Hall et al. 2014)]. EROEI is defined as the ratio of the exergy obtained by means of a certain dissipation structure to the amount of exergy necessary to create and maintain the structure. If the EROEI associated with a dissipation process is larger than one, the excess can be used to replicate the process in new structures. On a large scale, this process can create the complex system that we call the “industrial society.” The growth of the human civilization as we know it today, and the whole Anthropocene can be seen as the effect of the relatively large EROEI, of the order of 20–30 and perhaps more, associated with the combustion of fossil carbon compounds (Lambert et al. 2014).

A peculiarity of the dissipation of potentials associated with fossil hydrocarbons is that the system cannot attain homeostasis. The progressive depletion of the high-EROEI fossil resources leads to the progressive decline of the EROEI associated with fossil potentials. For instance, Hall et al. (2014) show that the EROEI of oil extraction in the USA peaked at around 30 in the 1960s, to decline to values lower than 20 at present. A further factor to be taken into account is called “pollution,” which accelerates the degradation of the accumulated capital stock and hence reduces the EROEI of the system as it requires more exergy for its maintenance (Meadows et al. 1972).

Only a small fraction of the crustal fossil carbon compounds can provide an EROEI >  1, the consequence is that the active phase of the Anthropocene is destined to last only a relatively short time for a geological time subdivision, a few centuries and no more. Assuming that humans will still exist during the post-Anthropocene tail, they would not have access to fossil fuels. As a consequence, their impact on the ecosystem would be mainly related to agricultural activities and, therefore, small in comparison with the present one, although likely not negligible, as it has been in the past (Ruddiman 2013; Mysak 2008).

However, we should also take into account that fossil carbon is not the only energy potential available to the human industrial system. Fissile and fissionable nuclei (such as uranium and thorium) can also generate potentials that can be dissipated. However, this potential is limited in extent and cannot be reformed by Earth-based processes. Barring radical new developments, depletion of mineral uranium and thorium is expected to prevent this process from playing an important role in the future (Zittel et al. 2013). Nuclear fusion of light nuclei may also be considered but, so far, there is no evidence that the potential associated with the fusion of deuterium nuclei can generate an EROEI sufficient to maintain an industrial civilization, or even to maintain itself. Other potentials exist at the earth’s surface in the form of geothermal energy (Davies and Davies 2010) and tidal energy (Munk and Wunsch 1998); both are, however, limited in extent and unlikely to be able to provide the same flow of exergy generated today by fossil carbon compounds.

There remains the possibility of processing the flow of solar energy at the earth surface that, as mentioned earlier on, is large [89,000 TW (Tsao et al. 2006) or 87,000 TW (Szargut 2003)]. Note also that the atmospheric circulation generated by the sun’s irradiation produces some 1000 TW of kinetic energy (Tsao et al. 2006). These flows are orders of magnitude larger than the flow of primary energy associated with the Anthropocene (ca. 17 TW). Of course, as discussed earlier, the capability of a transduction system to create complex structures depends on the EROEI of the process. This EROEI is difficult to evaluate with certainty, because of the continuous evolution of the technologies. We can say that all the recent studies on photovoltaic systems report EROEIs larger than one for the production of electric power by means of photovoltaic devices (Rydh and Sandén 2005; Richards and Watt 2007; Weißbach et al. 2013; Bekkelund 2013; Carbajales-Dale et al. 2015; Bhandari et al. 2015) even though some studies report smaller values than the average reported ones (Prieto and Hall 2011). In most cases, the EROEI of PV systems seems to be smaller than that of fossil burning systems, but, in some cases, it is reported to be larger (Raugei et al. 2012), with even larger values being reported for CSP (Montgomery 2009; Chu 2011). Overall, values of the EROEI of the order of 5–10 for direct transduction of solar energy can be considered as reasonable estimates (Green and Emery 2010). Even larger values of the EROEI are reported for wind energy plants (Kubiszewski et al. 2010). These values may increase as the result of technological developments but also decline because of the progressive occupation of the best sites for the plants and the increasing energy costs related to the depletion of the minerals needed to build the plants.

The current photovoltaic technology may use, but do not necessarily need, rare elements that could face near-term exhaustion problems (García-Olivares et al. 2012). Photovoltaic cells are manufactured using mainly silicon and aluminum, both common elements in the earth’s crust. So there do not appear to exist fundamental barriers to “close the cycle” and to use the exergy generated by human-made solar-powered devices (in particular PV systems) to recycle the systems for a very long time.

Various estimates exist on the ultimate limits of energy generation from photovoltaic systems. The “technical potential” in terms of solar energy production in the USA alone is estimated at more than 150 TW (Lopez et al. 2012). According to the data reported in (Liu et al. 2009), about 1/5 of the area of the Sahara desert (2 million square km) could generate around 50 TW at an overall PV panel area conversion efficiency of 10 %. Summing up similar fractions of the areas of major deserts, PV plants (or CSP ones) could generate around 500–1000 TW, possibly more than that, without significantly impacting on agricultural land. The contribution of wind energy has been estimated to be no more than 1 TW (de Castro et al. 2011) in some assumptions that have been criticized in (Garcia-Olivares 2016) Other calculations indicate that wind could generate as much as about 80 TW, (Jacobson and Archer 2012), or somewhat smaller values (Miller et al. 2011). Overall, these values are much larger than those associated with the combustion of fossil fuels, with the added advantage that renewables such as PV and wind produce higher quality energy in the form of electric power.

From these data, we can conclude that the transduction of the solar energy flow by means of inorganic devices could represent a future new metabolic “revolution” of the kind described by (Szathmáry and Smith 1995). (Lenton and Watson 2011) that could bootstrap the ecosphere to a new and higher level of transduction. It is too early to say if such a transition is possible, but, if it were to take place at its maximum potential, its effects could lead to transformations larger than those associated with the Anthropocene as it is currently understood. These effects are hard to predict at present, but they may involve changes in the planetary albedo, in the weather patterns, and in the general management of the land surface. Overall, the effect might be considered as a new geological transition.

As these effects would be mainly associated with solid-state devices (PV cells), perhaps we need a different term than “Anthropocene” to describe this new phase of the earth’s history. The term “Stereocene” (the age of solid-state devices) could be suitable to describe a new stage of the earth system in which humans could have access to truly gigantic amounts of useful energy, without necessarily perturbing the ecosystem in the highly destructive ways that have been the consequence of the use of fossil fuels during the past few centuries.

References (see original article)

 

The Next Ten Billion Years

 

This is a post that I published on "Cassandra's Legacy" in 2012. It was one of the most successful posts ever published on that blog, it was reposted, discussed, and criticized in several places, including a long rebuttal by John Michael Greer, "The ArchDruid." I commented on Greer's comments here. I think it is appropriate to repropose this rather ambitious description of the history of the universe on my new blog, "The Seneca Effect," after I explored some similar arguments in recent posts (The Great Turning Point of Humankind, Long term Perspectives of Nuclear Energy, and "Star Parasites").

So, here it is, just slightly revised and updated with respect to the initial version.

The next ten billion years

Posted by Ugo Bardi  

It is not surprising that we found the future fascinating; after all, we are all going there. But the future is never what it used to be and it is said that predictions are always difficult, especially those dealing with the future. Nevertheless, it is possible to study the future, which is something different from predicting it. It is an exercise called "scenario building". Here, let me try a telescopic sweep of scenario building that starts from the remote past and takes us to the remote future over a total range of 20 billion years. While the past is what it was, our future bifurcates into two scenarios; one "good" and the other "bad", all depending on what we'll be doing in the coming years.

The past 10 billion years

- 10 billion years ago. The universe is young, it has existed for less than four billion years. But it already looks the way it will be for many billion years in the future: galaxies, stars, planets, black holes and much more.

- 1 billion years ago. From the debris of ancient supernovas, the solar system has formed around a second-generation star, the Sun, about 4.5 billion years ago. The planets that form the system are not very different from those we see today. The Earth has blue oceans, white clouds, and dark brown continents. But there are no plants or animals on the continents, nor fish in the water. Life is all unicellular in the oceans, but its activity has already changed a lot of things: the presence of oxygen in the atmosphere is a result of the ongoing photosynthesis activity.

- 100 million years ago. Plenty of things have been happening on planet Earth. Starting about 550 million years ago, perhaps as a result of the ice age known as "snowball Earth," multicellular life forms have appeared. First, only in the oceans; then, about 400 million years ago, life has colonized the surfaces of the continents creating lush forests and large animals that have populated the Earth for hundreds of millions of years. That wasn't uneventful, though. Life nearly went extinct when, 245 million years ago, a giant volcanic eruption in the region we call Siberia today generated the largest known extinction of Earth's history. But the biosphere managed to survive and regrow into the cretaceous period, the age of Dinosaurs.

- 10 million years ago. The age of dinosaurs is over. They have been wiped out by a new mass extinction that took place 65 million years ago, caused perhaps by a giant asteroid hitting the Earth or, more likely, by a giant volcanic eruption in the region that, million years later, will be called "India." Again, the biosphere has survived and now it prospers again, populated with mammals and birds; including primates. We are in the Miocene period and the Earth has been cooling down over a period of several million years, possibly as the result of the Indian subcontinent having hit Asia and created the Himalayas. That has favored CO2 removal from the atmosphere by weathering. Icecaps have formed both at the North and the South poles for the first time in several hundred million years.

- 1 million years ago. The Earth has considerably cooled down during the period that we call "Pleistocene" and is now undergoing a series of ice ages and interglacials. Ice ages last for tens of thousands of years, whereas the interglacials are relatively short hot spells, a few thousands of years long. These climatic oscillations are perhaps the element that stimulated the evolution of some primate species which have developed bipedal locomotion. One million years ago, homo Erectus and homo Abilis can use fire and make simple stone tools.

- 100.000 years ago. The glacial/interglacial cycles continue. The hot spell called the "Eemian" period, about 114,000 years ago, has been short-lived and has given way to one of the harshest known glaciations of the recent Earth's history. But humans survive. In Europe, the Neanderthals rule, while the species that we call "homo sapiens" already exists in Africa.

- 10.000 years ago. The ice age ends abruptly to give rise to a new interglacial; the period that we call "Holocene." The Neanderthals have disappeared, pushed over the edge of survival by their "Sapiens" competitors. Climate stabilizes enough for humans to start to practice agriculture in the fertile valleys along the tropical region of Africa and Eurasia, from Egypt to China.

- 1000 years ago. The agricultural age has given rise to the age of empires, fighting for domination of large geographical areas. The human population has been rapidly growing, with the start of a series of cycles of growth and collapse that derive from the overexploitation of the fertile soil. 1000 years ago, the Western World is coming back from one of these periodic collapses and is expanding again during the period we call "Middle Ages".

- 100 years ago. The age of coal has started and has been ongoing for at least two centuries. With it, the industrial revolution has come. Coal and crude oil are the fuels that create a tremendous expansion of humankind in numbers and power. 100 years ago, there are already more than a billion humans on the planet and the population is rapidly heading for the two billion marks. Pollution is still a minor problem that goes largely unrecognized. The concentration of carbon dioxide in the atmosphere has been increasing to near 300 ppm over the 270 ppm which has been the level of the pre-industrial age. This fact is noted by some human scientists who predicted that it would cause a warming of the planet, but the long term consequences are not understood.

- 10 years ago. The fossil fuels that created the industrial age are starting to show signs of depletion and the same is true also for most mineral commodities. The attempt to replace fossil fuels with uranium has not been successful because of the difficulties involved in controlling the technology. Energy production is still increasing, but it shows signs of slowing down. The human population has reached 7 billion and keeps growing, but at reduced rates of growth. The Earth's agricultural system is in full overshoot and the population can only be fed by means of an agricultural industrial complex based on fossil fuels. The concentration of CO2 in the atmosphere has been growing fast and is now about 370 ppm. Global temperatures have been rising, too. The problem of global warming has been recognized and some efforts are being made to reduce the emissions of CO2 and of other greenhouse gases, but their concentration keeps increasing.  

Today. The world's industrial system seems to be close to stopping its growth and the financial system has been going through a series of brutal collapses. The production of crude oil has been stable during the past few years, but the overall energy production is still increasing because of the decision to extract expensive and polluting fuels out of "shales." The extraction of such fuels has been claimed to be a great success, but it seems that it has already reached its peak. The political situation is chaotic, with continuously erupting minor wars. The human population is now getting close to eight billion. The climate system seems to be on the verge of collapse, with deforestation, global warming, increased atmospheric humidity, decline of the ice caps and more. The concentration of CO2 in the atmosphere is now over 400 ppm and it keeps increasing.

The future in two scenarios

1.The "bad" scenario.

10 years from now. In 2030, the production of "conventional" crude oil has been in decline for about two decades. The enormous effort made to replace it by liquids produced using non-conventional sources, tar sands, shale oil, and other "heavy" oil sources, as well as biofuels, has been a failure. Uranium, too, has become scarce and several countries which don't have national resources have been forced to close down some of their nuclear plants. These trends are partially compensated by the still increasing production of coal; which is also used to produce liquid fuels and other chemicals that once were obtained from oil. The growth of renewable energy has stalled: there are no more resources to invest in research and development in new technologies and new plants, while a propaganda campaign financed by the oil industry has convinced the public that renewable sources produce no useful energy and are even harmful to the environment. Another propaganda campaign financed by the same lobbies has stopped all attempts of reducing the emissions of greenhouse gases. As a result, agriculture has been devastated by climate change and by the high costs of fertilizers and mechanization. The human population starts an epochal reversal of its growing trend, decimated also in reason of the increasing fraction of fertile land which is dedicated to biofuels.

100 years from now. In 2100, the human economic system has collapsed and the size of the economy is now a small fraction of what it had been at the beginning of the 21st century.  Resource depletion has destroyed most of the industrial system, while climate change and the associated desertification - coupled with the destruction of the fertile soil - have reduced agriculture to a pale shadow of the industrial enterprise it had become. The collapse of agriculture has caused a corresponding population collapse; now around two billion people. Most tropical areas have been abandoned because global warming has made them too hot to be habitable by human beings. The rise in sea level caused by global warming has forced the abandonment of a large number of coastal cities, with incalculable economic damage. The economy of the planet has been further weakened by giant storms and climate disasters hitting about every inhabited place. Crude oil is not extracted anymore in significant amounts and where there still exist gas resources, it is impossible to transport them at long distances because of the decay of the pipeline network and of the flooding of the ports. Only coal is still being extracted and coal-fired plants maintain electric power for reduced industrial activity in several regions of the North of the planet. Labrador, Alaska, Scandinavia, and Northern Siberia still host remnants of the old industrial society. Using coal liquefaction, it is still possible to obtain liquid fuels, mostly used for military purposes. The Earth still sees tanks and planes that exchange gunfire against each other.

1000 years from now. The industrial society is a thing of the past. Human-caused global warming has  generated the release of methane hydrates which have created even more warming. The stopping of the Oceanic thermohaline currents has transformed most of the planet into a hot desert. Almost all large mammals are extinct. Humans survive only in the extreme fringes of land in the North of the planet and in the South, mainly in Patagonia. For the first time in history, small tribes of humans live on the rapidly de-frosting fringes of the Antarctic continent, living mainly on fishing. In some areas, it is still possible to extract coal and use it for simple metallurgy that uses the remains of the metals that the 20th century civilization has left. Human beings are reduced to a few hundred million people who keep battling each other using old muskets and occasional cannons.

10.000 years from now. Human beings are extinct, together with most vertebrates and trees. Planet Earth is still reeling from the wave of global warming that had started thousands of years before. The atmosphere still contains large amounts of greenhouse gases generated by human activity and by the release of methane hydrates. The continents are mostly deserts, and the same is true for oceans, reduced to marine deserts by the lack of oxygenating currents. Greenland is nearly ice-free and that's true also for Antarctica, which has lost most of its ice. Only bushes and small size land vertebrates survive in the remote northern and southern fringes of continents.

100.000 years from now. The planet is showing signs of recovery. Temperatures have stabilized and silicate erosion removed a large fraction of the carbon dioxide accumulated in the atmosphere. Land animals and trees are growing again.

1 million years from now. The planet has partly recovered. The planetary tectonic cycles have re-absorbed most of the CO2 which had created the great burst of warming of long before. Temperature has gone down rapidly and polar ice caps have returned. The return of ice has restarted the thermohaline currents: oceanic waters are oxygenated again. Life - those species that had survived the warming disaster - are thriving again and re-colonizing the tropical deserts - which are fast disappearing.

10 million years from now. Earth is again the lush blue-green planet it used to be, full of life, animals, and forests. From the survivors of the great warming, a new explosion of life has been generated. There are again large herbivores and carnivores, as well as large trees, even though none of them looks like the creatures which had populated the Earth before the catastrophe. In Africa, some creatures start using chipped stones for hunting. In time, they develop the ability to create fire and of building stone structures. They develop agriculture, sea-going ships and ways of recording their thoughts using symbols. But they never develop an industrial civilization for lack of fossil fuels, all burned by humans millions of years before them.

100 million years from now. Planet Earth is again under stress. The gradual increase in solar irradiation is pushing the climate towards a new hot era. The same effect is generated by the gradual formation of a new supercontinent generated by continental drift. Most of the land becomes a desert - all intelligent creatures disappear. There starts a general decline of vertebrates, unable to survive on a progressively hotter planet.

1 billion years from now. The Earth has been sterilized by the increasing solar heat. Only traces of single-celled life still survive underground.

10 billion years from now. The sun has expanded and it has become so large that it has absorbed and destroyed the Earth. Then, it has collapsed in a white dwarf. The galaxy and the whole universe move slowly toward extinction with the running down of the energy generated by the primeval big bang.

_______________________________________________

2.The "good" scenario

Ten years from now. In 2030, fossil fuel depletion has generated a global decline in production. That, in turn, has led to international treaties directed to ease the replacement of fossil fuels with renewable energy. Treaties are also enacted with the purpose of minimizing the use of coal. The production and the use of biofuels for industrial machinery has been forbidden everywhere and treaties force producers to direct all the agricultural production towards food for humans. The existing nuclear plants make full use of the uranium in the warheads that had been accumulated during the cold war. Research on nuclear fusion continues, with the hope that it will provide useful energy in 50 years. Even with these actions, global warming continues and agriculture is badly damaged by droughts and erosion. Population growth stops and widespread famines occur. Governments enact fertility reduction measures in order to contain the population. The economy thrives, stimulated by the demand for renewable plants.

A hundred years from now. The measures taken at the beginning of the 21st century have borne fruit. Now, almost 1% of the surface of the planet is covered by solar panels of the latest generations which produce energy with an efficiency of the order of 50%. In the north, wind energy is used, as well as energy from ocean currents, tides, and waves. The production of renewable electrical energy keeps growing and it has surpassed anything that was done in the past using primitive technologies based on fossil fuels. No such fuels are extracted any longer and doing so is considered a crime punishable with re-education. The industrial economy is undergoing rapid changes, moving to abandon the exploitation of dwindling resources of rare metals, using the energy available to exploit the abundant elements of the Earth's crust. The human society is now completely based on electric energy, also for transportation. Electric vehicles move along roads and rails, electric ships move across the oceans and electric airships navigate the air. The last nuclear fission plants have been closed for lack of uranium fuel around 2050, they were not needed anymore. Research on nuclear fusion continues with the hope that it will provide usable energy in 50 years. Despite the good performance of the economy, the ecosystem is still under heavy stress because of the large amounts of greenhouse gases emitted into the atmosphere during the past centuries. Agriculture is still reeling from the damage done by erosion and climate change. The human population is in rapid, but controlled, decline under the demographic measures enacted by governments. It is now less than 4 billion humans and famines are a thing of the past.  With the returning prosperity, humans are restarting the exploration of space that they were forced to abandon at the start of the 21st century.

1000 years from now. In the year 3000 A.D. the ecosystems of the planet have completely recovered from the damage done by human activities during the second millennium. A sophisticated planetary control system manages solar irradiation by means of space mirrors and the concentration of greenhouse gases by means of CO2 absorbing/desorbing plants. The planet is managed as a giant garden, optimizing its biological productivity. The Sahara desert is now a forest and the thermohaline currents pump oxygen to the northern regions, full of life of all kinds. The solar and wind plants used during the previous millennium have been mostly dismantled, although some are still kept as a memory of the old times. Most of the energy used by humankind is now generated by space stations which capture solar energy and beam it to the ground in forms easily usable by humans. Research in controlled fusion energy continues in the hope that it will produce usable energy in 50 years. Humans are now less than one billion, they have optimized both their numbers and their energy use and they need enormously less than they had needed in the more turbulent ages of one thousand years before. The development of artificial intelligence is in full swing and practically all tasks that once had been in the hands of humans are now in the "hands" of sophisticated robotic systems. These robots have colonized the solar system and humans now live in underground cities on the Moon. The new planetary intelligence starts considering the idea of terraforming Mars and Venus. The first antimatter powered interstellar spaceships have started their travel to faraway stars.

10.000 years from now. There are now less than a billion human beings on Earth who live in splendid cities immersed in the lush forest that the planet has become. Some of them work as a hobby on controlled nuclear fusion which they hope will produce usable energy in about 50 years. The New Intelligence has now started terraforming Mars. It involves similar methods as those used for controlling the Earth's climate: giant mirrors and CO2 producing plants that control the Martian atmosphere, increasing its pressure and temperature. The terraforming of Venus has also started with similar methods: giant screens that lower the planetary temperatures and flying plants that transform CO2 into oxygen and solid carbon. That will take a lot of time, but the New Intelligence is patient. It is also creating new races of solid-state beings living on the asteroids and orbiting around the Sun. The exploration of the galaxy is in progress, with spaceships from the solar system now reaching a "sphere" of about a thousand light-years from the sun.

100.000 years from now. About 500 million humans live on Earth - mostly engaged in art, contemplation, and living fully human lives. Some of them still engage in experiments that are supposed to produce controlled nuclear fusion after 50 years or so. Mars is now colonized by Earth's plants, which are helping to create an atmosphere suitable for life; it is now a green planet, covered with oceans and lush forests. Several million human beings live there, protected from cosmic radiation by the planetary magnetic field artificially generated by giant magnetic coils at the planet's poles. The temperature of Venus has been considerably lowered, although still not enough for life to take hold of its surface. The exploration of the galaxy is in full swing. Other galactic intelligences are encountered and contacted.

A million years from now. Venus, Earth and Mars are now lush and green; all three full of life. Mercury has been dismantled to provide material for transforming the solar system into a single intelligence system that links a series of creatures. There are statites orbiting around the sun, solid-state lifeforms living on asteroids and remote moons, ultra-resistant creatures engineered to live in the thick atmosphere of Jupiter and of the other giant planets. Humans, living on the green planets, have become part of this giant solar network. The other extreme of the Galaxy has been now reached by probes coming from the solar system.

10 million years from now. The New Intelligence is expanding over the Galaxy. The Green planets are now the place of evolution tests and the re-created Neanderthals now live on Mars, whereas dinosaurs have been recreated on a Venus where the planetary control system has recreated conditions similar to those of the Jurassic on Earth.

In 100 million years from now. Controlling temperatures over the three green planets of the Solar System has become a complex task because of the increasing solar radiation. Mirrors are not enough anymore and it has been necessary to move the planets farther away from the sun. The statites that form the main part of the solar intelligence now surround the sun almost completely in a series of concentric spheres.

In a billion years from now. The solar radiation has increased so much that it has been necessary to move the green planets very far away. One year lasts now as 50 of the "natural" Earth years as they were long before. But these are no problems for the Solar Intelligence, now just part of the Galactic intelligence. The three green planets. Venus, Earth, and Mars are three jewels of the Solar System.

In ten billion years from now. The sun has collapsed in a weak white dwarf and all the planets that orbit around it are frozen solid. The Galaxy has lost most of its suns and the universe is entering its last stage of expansion which will lead it to become a frozen darkness. The Galactic Intelligence looks at a galaxy that is by now a pale shade of its old glory. The Intelligence says, "Let there be light" And there is light.




(this text was inspired by Isaac Asimov's story "The Last Question")

 

Star Parasites: Carbon-Based Life and the Future of the Universe

  The universe is enormous, and yet it seems to follow certain patterns. What we are seeing today is the result of the dissipation of the enormous energy burst that came with the big bang, some 14 billion years ago. The dissipation occurs in steps, as it is typical of dissipative systems, forming a trophic chain of energy stocks that has some parallels with the kind we know in Earth's ecosphere. In this giant chain of beings, our role seems to be of "star parasites," growing on the light emitted by a star which, from the viewpoint of the star, is waste. Above: an image obtained by the Chandra X-ray telescope. This region shows hundreds of supermassive black holes, each one in a galaxy far beyond our own. (source: Ethan Siegel).

 

Nowadays, we are obsessed with the idea that we need to "produce energy." That is, of course, a wrong way to express the concept. Energy can't be produced: the first principle of thermodynamics tells us that. Energy can only be transformed from a kind of energy to another. And even that is not correct. You can only transform energy going in a specific direction, it is dictated by the second principle of thermodynamics. All you can do, and you can do no more, is to transform high energy potentials into low energy potentials. This is called "potential dissipation." 

An example: what we do when we claim that we "produce energy" is, mostly, to combine atmospheric oxygen with those long-chain carbon and hydrogen molecules that we call "fossil fuels," stored inside Earth's crust. The dissipation process starts with the chemical energy potential stored in crude oil (or gas, or coal), then it goes on in steps, always downhill, until we are left with low-temperature heat, plus water and carbon dioxide. What we covet from this transformation is heat that we then use to run engines and do more things. These intermediate steps we can call "dissipative structures," a term proposed for the first time by Ilya Prigogine.

Can we go back? It is possible, but we can't trick nature and go against the second principle. It is a steep uphill road that of recombining water and carbon dioxide to form again long-chain carbon molecules. We can only achieve that by dissipating an even higher potential, solar light. It is done all the time by plants, it is called "photosynthesis." It is the process that, long ago, created the carbon compounds we are so busy burning nowadays.

This is what makes us "star parasites." We, like the whole Earth's ecosystem, live by dissipating the potential of our star, the sun, and using the energy flow to build dissipative structures: plants, animals, and everything human-made. More correctly, we should say that we are "commensals," a technical term for those parasites that do not compete with their host for resources. From the viewpoint of the star, light is just waste discarded into space. We just intersect a minimal fraction of it and we re-emit it in a slightly lower potential form, infrared light. 

But how about the Sun? Is it a parasite of anything? Not in the same way, but the second principle of thermodynamics holds for the Sun, too. The potential that the Sun is dissipating originated long ago, with the big bang. At that time, an enormous energy potential was accumulated in a very small space. When the big bang came, this energy started being dissipated, a process that has been lasting for 14 billion years and is continuing now. As the universe expands, it cools down. Far from the enormous temperatures of its early life, the universe is now down to just 2.725 degrees Kelvin -- close to the absolute zero. In terms of radiative potential, it is by now dead. Too cold to create new dissipative structures.

But the universe can still create dissipative structures because matter can accumulate into gravity pits. These accumulations concentrate gravitational energy, creating new forms of potential dissipation. Stars are formed by accumulating a vast mass of interstellar dust in a relatively small space. Eventually, a star reaches conditions of temperature and pressure so high that it can start another process of dissipation, turning matter into energy. It is the fusion of hydrogen nuclei into helium ones, a process that, as far as we know, can happen only inside the depth of star cores. It is what makes us star parasites. There are surely other carbon-based lifeforms that do the same around other stars of our galaxy and other galaxies. (image from ESA)

Hydrogen fusion is not the only large-scale energy dissipation process in the universe. There is a sort of "trophic chain" out there, with entities that can be seen as existing at higher trophic levels. Black holes are predators that can devour anything that comes close to them, including stars, and turn it into more internal matter. Neutron stars can be eaten by black holes, but they can eat stars, too. 

Stars themselves have a life of their own. Most of them tend to become brighter and larger as they get older and consume their hydrogen stock. If they are very large, they end their life with the spectacular explosions called "supernovae." The remnant may be a neutron star or a black hole. The debris ejected into space will eventually coalesce to form a new star -- an "offspring" of the old one. So, stars reproduce but, as far as we know, all the information stored in the old star disappears in the cloud of gas that forms as a result. So, there is no transmission of information from a generation of stars to another and no evolution in the Darwinian sense (*). 

The same would seem to be valid for neutron stars, whose destiny is normally to become black holes. Then, black holes are supposed to evaporate over extremely long times by the slow emission of Hawking radiation, again losing all the information that may have been contained inside. (image below from NASA)

That's not the end of the great trophic chain. There is another energy dissipation mechanism: the decay of heavy radioactive nuclides, uranium and thorium. It generates energy that plays a fundamental role in keeping hot, at about 6000 K, the molten core of our planet. It probably does the same for billions of Earth-like planets of our galaxy. This heat is nearly impossible to detect at interstellar distances because it appears as very low temperatures at the surface, probably around a few tens of degrees K. Nevertheless, compared with the background temperature of the universe, Earth-like planets shine.

The decay of heavy nuclides is slow and not very spectacular, but it is fundamental for carbon-based life. A geologically active nucleus generates enough heat to keep the inner layers of Earth hot enough to create the structures we call "hydrothermal vents" at mid-ocean ridges. It is believed that life started at these undersea vents exploiting geothermal energy much before it ventured to the surface and learned how to exploit solar light. Then, life needs a constant supply of carbon dioxide, which is provided by outgassing from the hot mantle. A cold, solid nucleus would not be able to outgas anything and, in such case, the carbon dioxide in the atmosphere would be consumed by reacting with surface silicates and disappear in a few million years at most. A hot inner Earth doesn't just provide CO2 by outgassing. It actively controls its atmospheric concentration by removing carbon by silicate erosion and transporting it to the mantle by the subduction process that takes place at the edges of the crustal plates. And subduction can happen only because of the presence of convective currents in the semi-molten mantle.

So, no radioactive elements, no life. Or, at least, the lifetime of the ecosphere would be much shorter than it is, probably too short to generate complex, multicellular lifeforms.

There is more about radioactive elements: they have a trick that makes them go off in a burst of rapid energy dissipation. It is the neutron-catalyzed reaction that occurs for a sufficiently high concentration of a "fissile" nuclide. In the whole universe, only one fissile nuclide exists in significant amounts: the 235 isotope of uranium: most uranium and the other long-lived radioactive element, thorium, are not fissile, but "fissionable." They can undergo fission, but cannot sustain a chain reaction. 

Even though U(235) is rare, with its half-life of about 700 million years, in very ancient times it was less rare than it is nowadays. So, geological phenomena could accumulate a sufficiently large amount of it to generate a natural chain reaction. It happened at least once in Earth's history, some 2 billion years ago in Oklo, in the area we call today "Gabon," in Africa. Nothing spectacular happened at that time: the chain reaction went on and off several times, generating some heat over a few hundred thousand years. Probably, the place was rich of hot springs at the time, but there were no people who could have enjoyed them. Not even animals existed, they were to appear only one billion and a half years later. So this natural uranium reactor had little or no effect on the ecosystem. 

We don't know if other Oklo-like reactors existed on Earth but, if they existed, they must have been marginal phenomena (even though some people propose the rather improbable theory that the Moon was created in a nuclear explosion). What we know is that, in recent times, the creatures called "humans" managed to process minerals from Earth's crust in such a way to concentrate heavy nuclei at levels where chain fission could be maintained for a certain time. They even managed to "breed" fissile nuclei out of fissionable ones. The flow of energy created in this way is small, a few percent of the energy that humans are generating from fossil fuels, infinitesimal in comparison to the output of a star. But it is there. Could it become much larger in the future and became a significant mechanisms of energy dissipation in the universe? 

It is an especially interesting point because, as far as we know, the only way to run a nuclear chain reaction on a large scale is by having intelligent beings actively control it. We can say that since there is at least one such civilization in the universe (us) and there is no reason to think we are alone. The consequence is that carbon-based sentient beings might use the energy created by fission chain reaction to engage in major feats of planetary engineering and interstellar travel.

 

Of course, we are not seeing anything like that in the universe. This is the essence of the so-called "Fermi Paradox," often understood as meaning that humans are the only technological civilization existing in the universe. In a previous post, I argued that the explanation is the result of two conditions. One is that energy production by controlled nuclear fusion is not possible outside stars, so it is not available to planetary civilizations. The other is that the amounts of radioactive elements available in the solar system are too small to provide sufficient energy to sustain a civilization for a long time. Not even fissionable elements are sufficiently abundant to create more that a transient "flare" of energy dissipation that then would rapidly decline before a civilization could engage in a sustained effort of interstellar exploration.

With the fissile/fissionable resources available, humans, or their extrasolar colleagues, could at most engage in a limited, local interstellar exploration program before running out of energy. More than that, we lack the capability to control what we are doing and it is likely that we'll soon be destroyed by the pollution we ourselves are generating, while at the same time doomed by the depletion of the mineral resources needed to keep civilization going. Or that we'll blow out ourselves using those chain fission reactions we are so proud of. Fortunately, it seems that some 50 years ago we missed the chance we had to embark in a dangerous and ultimately futile nuclear energy program. Now, it is probably too late to gather the resources that would be necessary. Given the current situation, dreams of galactic empires seem to be a little premature.

If we are lucky, we'll just fall back to our normal role of star parasites, after having run out of other forms of potentials to dissipate. That might not be such a bad destiny, considering that the flow of solar energy arriving on our planet is several thousand times larger than the flow of primary energy produced nowadays. But solar energy, although abundant, may not be easy to convert into forms that can power a starship.

So, are carbon-based civilizations destined to remain forever stuck to their home planets? Not necessarily. The universe is not static, it keeps changing albeit at a very slow pace and the availability of fissile materials may be different in the future. We saw that all that is happening in the universe nowadays is the result of the dissipation of the original energy of the big bang. Nuclear fission is no exception. The existence of radioactive nuclei is the result of processes believed to take place mainly in supernova explosions, although it seems that large amounts can also be created in the processes called "kilonovae," the fusion of two neutron stars that generates a black hole. Fissionable nuclei have a half-life of the order of billions of years, so that the universe (14 billion years old) is being progressively enriched with them. 

So, maybe there is a threshold at some moment in the future in which Earth-like planets will be normally endowed with sufficiently large resources of radioactive materials that carbon-based lifeforms might be able to engage in the exploration, and maybe even the colonization, of the galaxy. They might even be able to overcome the limitations of planetary resources by scooping heavy nuclides from the dust around neutron stars or black holes. Maybe we need to wait a few billion years but, from the viewpoint of the universe, a few billions of years are nothing.

This kind of reasoning is, of course, very tentative, but surely fascinating. The universe as a dissipation system appears as a thermodynamic machine. And when you deal with a machine, you can't avoid wondering what is its purpose. Why the universe is the way it is? Why do radioactive elements exist? Why is carbon-based life so dependent on their existence? Why do they exist in the small amounts that we see nowadays? Is the future accumulation of radioactive nuclei planned for some purpose? Are carbon-based civilizations destined to use this energy, someday? Are they supposed to be "filtered" by the danger of the power of nuclear fission? It is a theme that Isaac Asimov already explored in his 1957 short story "The Gentle Vultures." 

Surely, we need to avoid the mistake of the fleas that think that the dog was created for them. But, who knows? The flea God may be more powerful than what we can imagine.

 _____________________________

(*) It has been hypothesized that DNA-like structures could exist inside stars, formed by the combination of "cosmic strings" and "magnetic monopoles." But, for what we can say, these lifeforms cannot move out of their stars and maybe they can't even perceive the existence of the universe outside. Something similar holds for neutron stars, despite the attempt by Robert Forward in his novel "Dragon's Egg" (1980) to imagine living beings composed of neutronium. Black holes, then, tend to destroy information and have an extremely long life. Of course, there may exist things we can't even remotely imagine in the universe but for the time being that seems to be a safe assumption. Incidentally, I went back to read Forward's novel and I found it incredibly boring. Times are changing and the novel is by now an obsolete art form.