Imagine that our civilization has collapsed. You are one of the few survivors. How can you rebuild an advanced industrial civilization out of the rubble of the old one?
This is the question that Lewis Dartnell sets out to answer in his book The Knowledge: How to Rebuild Our World from Scratch. This book is amazing, and everyone ought to read it.
A disclaimer: I am a biologist with vague memories of undergrad chemistry, and I have zero experience with disaster prep or mechanical engineering. Therefore, I am completely unqualified to assess the information presented in large parts of this book. I still chose to write this review because, as Dartnell points out in the introduction, there isn’t any human alive today who knows how all parts of our complex civilization work. His whole point in writing this book was to present a general overview of how to reboot our civilization to readers who are intelligent and curious but are not experts in every single domain of knowledge present herein. My goal is to evaluate how well he has succeeded in addressing readers like me.
The book was written in 2014, a.k.a. The Before Times, and given COVID-19 and the war in Ukraine, some of the potential disaster scenarios strike extremely close to home in a way they would not have when the author wrote them. Consider this passage from the introduction:
“A particularly virulent strain of avian flu [reviewer: or bat coronavirus] finally breached the species barrier and hopped successfully to human hosts… The contagion spread devastatingly quickly in the modern age of high-density cities and intercontinental air travel…” (p. 1)
Ouch.
If you have a sensitive conscience or vivid imagination, some of the passages, especially in the first two chapters, are best not read at bedtime. In Chapter 1, which describes different forms the collapse could take, the author concludes that, from the standpoint of rebuilding an advanced civilization, the “best” kind of apocalypse would be “a sudden and extreme depopulation that leaves the material infrastructure of our technological civilization untouched” (p. 23). This way, survivors could rely on plentiful supplies (stores of canned food, etc.) for a “grace period” in which to reboot civilization without falling all the way to the level of hunting-gathering, which is extremely hard to break out of. In contrast, the worst-case scenario would be one that leaves most humans alive while wiping out their stuff: a coronal mass ejection from the Sun that destroys all our power grids, or a nuclear war that causes nuclear winter and prevents us from growing enough crops (of course, a nuclear war would also kill plenty of people directly). If our infrastructure were destroyed while most people were left alive and in need of sustenance, Dartnell writes,
“[T]he roving crowds would rapidly consume the remnant supplies and so precipitate a subsequent mass depopulation. At the end, survivors would still encounter a world without people, but one that has now also been stripped bare of any resources that would have offered them a grace period of recovery” (p. 22).
That said, Dartnell acknowledges that too few survivors would be bad, too, because you need enough humans to achieve the degree of specialization and division of labor necessary for rebooting civilization, as well as to avoid excessive inbreeding in the next generation. With a bit of handwaving, he settles at 10,000 people in one location as “the ideal starting point.”
While I understand Dartnell’s logic here, the dispassionate calculus of “it’s better for most people to die while their stuff is left intact, not the other way around” still gives me chills. For the purposes of this book, Dartnell focuses on the best-case (i.e., pandemic) scenario rather than the worst-case (coronal ejection or nuclear war) scenario, presumably because a book that simply said, “You and all of humankind are doomed no matter what you do” would be too depressing to sell. Let us assume, then, the, uh, best-case scenario (calling a deadly pandemic a best-case scenario while COVID-19 keeps roaming around feels supremely ironic, but let’s move on).
The book covers, or at least mentions, all the basics of civilization that the survivors of the apocalypse will have to recreate. The amount of research that went into this book is truly remarkable, and I salute Dartnell for having learned it all and presented it in a more or less accessible fashion (albeit the degree of “more” vs. “less” varies among the chapters, as I will discuss later). There is a chapter for each of the following:
Chapter 2 is a standard survivalist’s guide to making it in the immediate aftermath of the “best-case” apocalypse, in which plentiful resources are available for the few survivors. Dartnell advises the readers to raid defunct grocery stores and pharmacies for non-perishable food and medicine, siphon drinking water out of swimming pools, and get out of cities, which will rapidly become dangerous – the “rot and decomposition” of the victims of the apocalypse will “pose a severe health hazard” (p. 44). Instructions on how to reboot an advanced civilization begin in chapter 3, on agriculture.
Agriculture is straightforward in concept, if not in practice. Dartnell gently points out that those of us accustomed to picking up our food at the supermarket likely underestimate the effort it takes to produce a plentiful harvest; modern farming is “grossly artificial” (p. 56), a process of getting the most crop for the least amount of effort while protecting the crop from competitive weeds and destructive pests. The author then describes the basic tools used in agriculture – hoe, sickle, scythe, plow, etc. – and different types of soil, distinguished by the proportion of three components: sand, silt, and clay. Different crops prefer different kinds of soil: wheat, beans, and potatoes grow well in clay-rich soils; rye and sugar beets do well in sandy ones. For a high-yield harvest, the crops must be fertilized with nitrogen, phosphorus, and potassium, which, in the absence of synthetic fertilizer, can be obtained from excrement, crushed bones, and wood ash, respectively. I wish the author had devoted at least some space to growing fruits and vegetables, and animal husbandry.
The most important idea in this chapter is the Norfolk four-course rotation, responsible for a great increase in agricultural productivity in 18th-century Britain. The idea behind crop rotation is that growing different crops in succession on the same plot of land makes it more difficult for pests and diseases to get established, and it also replenishes nutrients in the soil. In the Norfolk four-course rotation, you start by planting the field with legumes in year 1. Legumes house symbiotic nitrogen-fixing bacteria in nodules in their roots, thereby replenishing bioavailable nitrogen in the soil that is depleted by other crops. Starting the crop rotation with legumes (clover, alfalfa, beans, lentils, soy, peanuts, depending on the local climate) gives the soil a nice boost of nitrogen, which is then used in year 2 by wheat, a staple crop for human consumption. Then, in year 3, plant the field with root crops, such as turnips, rutabagas, or potatoes. The great thing about these crops is that you can feed them to your livestock throughout the year, so that you can have fresh meat and milk in the winter instead of slaughtering all but a few breeding pairs of your cattle every fall, as European peasants used to do in the Middle Ages. Finish the four-course rotation with barley in year 4.
Barley can be used to make beer, one of the foodstuffs described in chapter 4 (food and clothing). This, to me, was the most intuitive and familiar chapter in the book. As Dartnell points out, food preparation has two goals: prevent or delay spoilage by microbes and make nutrients in the food easier to absorb by the body. There are several ways to protect food from microbes. You can deprive the microbes of water by drying or salting the food; introduce a toxic compound, such as acid (in pickling) or creosote (in smoked foods); or kill the little suckers in situ with a combination of heat and pressure and prevent any more from getting in (pasteurized and canned food). As for making nutrients more bioavailable, the author provides basic instructions for baking bread and brewing the aforementioned beer.
One interesting thing I learned from chapter 4 is that there is an alternative refrigerator design more suitable to a post-apocalyptic society than the compression refrigerators we all use: the absorption refrigerator. Interestingly, absorption and compression refrigerators were developed around the same time, but compression refrigerators got a marketing boost from electricity companies, which is why they came to predominate. The absorption refrigerator will be easier to construct in the aftermath of the apocalypse, Dartnell writes, plus it has no moving parts and hence is less likely to break down.
A description on how to make fibers and weave cloth then follows. The main takeaway is that spinning fibers and weaving cloth without modern technology is horribly tedious, which is why new clothes were a luxury for the rich during most of human history. Dartnell provides basic instructions for building a spinning wheel for turning wool into fibers, and a loom for weaving cloth. He mentions something called the flying shuttle, which enables textile weaving to be automated and “powered by a waterwheel, steam engine, or electric motor” (p. 101) – this will be necessary for more advanced stages of the post-collapse civilization.
Chapters 5 and 6 (substances and materials) describe lots of interesting chemistry that a recovering society will have to master. Unfortunately, the survivors won’t have readily available supplies of petroleum for making plastics, and hence will have to rely on a more traditional source of organic compounds: wood. Dartnell recommends that survivors establish groves of fast-growing trees, such as ash and willow, and he describes useful materials we can obtain from them.
Wood can be turned into charcoal, a fuel that burns hotter and is more compact than plain wood and will be vital for applications such as smelting iron. Making charcoal involves incomplete combustion of the wood in the presence of limited oxygen to drive out water and volatile organic compounds. Said compounds can be isolated by burning wood in an enclosed metal container with a pipe to capture the gasses, and then condensing them by running the pipe through a container of cold water. The condensate separates into a watery fraction and a thick sludge; each fraction can be further separated by distillation, the principle of which is given in chapter 4. The watery fraction, originally called pyroligneous acid, is a mix of acetic acid, acetone, and methanol, all three of which are valuable industrial chemicals. The sludge is composed of turpentine, creosote, and pitch, useful for making pigments, preventing microbial growth, and making torches, respectively. Finally, wood ashes can be used to isolate potash, a valuable alkaline substance (appropriately, the word “alkali” comes from the Arabic for “burnt ashes”). If you throw the ashes in some water, skim the floating bits off the top, and then boil off the water or let it evaporate, you will find potash: white crystals composed of a mix of compounds, mostly potassium carbonate (K2CO3). You can use the same process with seaweed instead of wood to make soda ash, rich in sodium carbonate (Na2CO3); much more on soda ash in chapter 11.
Aside from isolating useful chemicals out of wood, Dartnell writes that one of the first things a recovering society must do is learn to work with calcium carbonate (CaCO3), which is found in limestone, chalk, coral, and seashells. By spreading crushed calcium carbonate on acidic soils, you neutralize their pH and improve crops’ ability to absorb nutrients. Baked in a kiln at >900oC, calcium carbonate breaks down into calcium oxide and carbon dioxide (CaCO3 → CaO + CO2). Calcium oxide, aka quicklime, is an extremely caustic compound that can be sprinkled over mass graves to control disease spread; Dartnell helpfully comments that this “may well be necessary after the apocalypse” (p. 110). If you mix quicklime with water (carefully, because it’s an extremely exothermic reaction), you will make calcium hydroxide (Ca(OH)2), aka slaked lime. Slaked lime is super useful for whitewashing walls, treating wastewater, and in construction, as described below.
Slaked lime is the foundation of architecture, serving as an ingredient in mortar, plaster, and, most importantly, cement. The use of cement dates to ancient Rome, but the modern method for making Portland cement was developed in 1794 and involves baking limestone and clay together at 1,450oC and adding gypsum. To make concrete, mix one part Portland cement with two parts sand or gravel plus “enough water to make a thick gloop” (p. 129). One problem with concrete is its very low tensile strength, but this can be solved by reinforcing concrete with steel rods to make rebar. Suspecting that his readers don’t have warm feelings toward concrete, the author writes in its defense:
“Now, I know that concrete is a horrifyingly dull and gray building material, and that there have been some architectural abominations constructed with it [reviewer: cough-Boston City Hall-cough]. But let’s step back and consider for a second what truly remarkable stuff it really is. Concrete is essentially man-made rock… an icon of the modern age” (p. 129).
Other construction materials described here include clay, glass, and metals. Clay, which is fortunately abundant in the environment, is conceptually simple: you shape it into pottery or bricks and fire it in a kiln. Glass, which was first made in Mesopotamia over 5,000 years ago, consists of silica (found in sand) combined with potash or soda ash to lower its melting point to within the reach of a kiln, plus quicklime to prevent the resulting glass from melting in water. Iron and steel will be easy to scavenge from ruined cities in the aftermath of the collapse, but Dartnell also provides instructions for building a blast furnace to smelt iron, i.e., to remove the other elements the iron is bound to in iron ore. A blast furnace, first invented in ancient China, yields pig iron – a high-carbon alloy of iron that is malleable and useful for making many objects such as cooking pots, but too brittle for use in load-bearing structures. To turn pig iron into hard steel, you need to remove the carbon using a Bessemer converter, a giant vat in which air bubbles through molten iron. The oxygen in the air reacts with carbon in the pig iron to form carbon dioxide, which then bubbles out of the metal. You run the reaction long enough to remove all carbon, and then mix in the desired amount of carbon at the end (0.2-1.2%, depending on what the steel is to be used for).
Aside from the strong alkali (potassium carbonate and sodium carbonate) described previously, a recovering society will need strong acids. For most of human history, we had only one acid, and a weak one at that: acetic acid, found in vinegar. During a reboot, survivors should fast-forward to start making a stronger acid: sulfuric acid, H2SO4. To make sulfuric acid, react sulfur dioxide (obtainable from pyrite rocks) with chlorine gas (made out of seawater by electrolysis; see chapter 11) to make sulfuryl chloride: SO2 + Cl2 → SO2Cl2. Sulfuryl chloride reacts with water to produce sulfuric acid and hydrogen chloride gas: SO2Cl2 + 2 H2O → H2SO4 + 2 HCl. Sulfuric acid has a ton of uses: add it to ground-up bones to make phosphorus more bioavailable in a fertilizer; bleach textiles with it; use it in processing iron and steel or as an ingredient in iron gall ink (chapter 10); mix it with ethanol to make diethyl ether, used as an anesthetic for surgery (chapter 7). Sulfuric acid can also be used to make other acids: it reacts with table salt (sodium chloride, NaCl) or saltpeter (potassium nitrate, KNO3) to make hydrochloric acid or nitric acid, respectively.
Aside from briefly mentioning ammonia (which can be fermented out of human urine, how lovely) and glue (made by boiling collagen-rich animal tissues such as skin, horns, and hooves), the author devotes a lot of text to humble soap, essential for limiting the spread of pathogens. Soap is made by saponification: reacting lipids with an alkaline substance to produce a fatty acid salt (that’s what soap is) and water. You can react potash or soda ash with slaked lime to make potassium hydroxide or sodium hydroxide, both of which are called lye (K2CO3 + Ca(OH)2 → CaCO3 + 2 KOH). Lye boiled with some plant oil or animal fat makes soap – but do not make it in an aluminum pot, as aluminum reacts with strong alkalis to make explosive hydrogen gas.
Dartnell emphasizes the importance of soap in chapter 7 (medicine). The chapter starts with the author rightfully acknowledging two things: It is “impossible to meaningfully describe even a small sliver of current medical knowledge” (p. 146) in a 20-page chapter, and it will be impossible to prevent health care from plunging off a cliff after the apocalypse. His aim in writing this chapter is to provide tidbits of advice that will continue to be useful after the medical complex collapses, and to help survivors recreate modern medicine eventually. Survivors will have one important advantage over premodern people: the knowledge that pathogens cause disease, and that they can be controlled by frequent handwashing. Dartnell’s whirlwind tour of post-apocalyptic medicine includes a brief mention of oral rehydration therapy for cholera, birthing forceps for assisting in difficult childbirth, stethoscopes and X-rays for diagnostics, diethyl ether (made by reacting a strong acid with ethanol) for surgical anesthesia, and several medicinal plants, notably opium, extracted from poppies, for pain.
He wraps up chapter 7 by describing antibiotics, the first of which, penicillin, was discovered by Fleming in the 1920s. Importantly, although it is relatively easy to culture molds that produce antibiotics (as a molecular biologist, I can confirm this), preparing clinical-grade antibiotics is much harder: a patient injected with “mold juice” would go into anaphylactic shock. To purify penicillin (or another antibiotic), you need to filter the mold culture media and add a bit of acid and ether, shake well, and let the solution separate into the organic (top) layer and aqueous layer. Transfer the organic layer, which contains penicillin, into a sterile flask, and shake it with some alkaline water to cause the antibiotic to pass back into the aqueous solution. Unfortunately, this process is inefficient, requiring 2,000 liters of mold culture to make enough penicillin for one person for one day. Dartnell points out that during World War II, researchers made penicillin in “makeshift extraction equipment built using an old bathtub, trash cans, milk churns, scavenged copper piping, and doorbells” (p. 163), and that something similar may happen post-collapse.
In chapter 8 (energy), Dartnell starts out by reflecting on the gigantic amounts of energy that wealthy modern people use. When we account for all the energy we use both directly (e.g., the electricity we use in our homes) and indirectly (e.g., the energy used to grow the food we eat and the products we buy), each American uses approximately 90,000 kWh/year, which is equivalent to “every American having a team of fourteen horses, or more than a hundred humans, working flat-out, 24/7 for them” (p. 166). The average European uses 40,000 kWh/year. Sobering stuff. How to replace some of this energy once we lose access to plentiful fossil fuels post-apocalypse?
Dartnell begins with the most ancient forms of mechanical power: the waterwheel and the windmill. The rotation driven by a waterwheel or windmill has been used to grind grain with a millstone, but two other inventions – the crank and the cam, both pictured on p. 171 – can be used to transform rotation into back-and-forth motion or the repeated lifting and dropping of a hammer, respectively. With these three types of motion – rotation, back-and-forth, and hammering – waterwheels and windmills can be used to drive a huge variety of industrial applications, including pressing olives for oil, sawing wood, crushing limestone, breaking up metal ore, pounding wood to pieces to make paper, etc.
The author then provides detailed descriptions of a steam engine (internal combustion engines are described in the next chapter, on transportation). He points out two good reasons to build steam engines rather than leapfrogging over them to internal combustion engines: steam engines are much easier to build, and more forgiving of what is fed into them. An internal combustion engine requires refined gasoline, whereas a steam engine will run on pretty much anything that burns, such as agricultural waste.
A chapter on energy would not be complete without electricity. The author comments on how electricity is constantly, reliably, unobtrusively delivered to our homes:
“[An unfailing supply of electricity] is something we’ve come to take for granted. Just a century ago, all the energy for a household would have to be physically delivered: oil for lamps, charcoal or coal for cooking and heating…” (p. 184)
The basic principle is that electromagnetism can cause motion, and vice versa. These phenomena can be harnessed to create an electric current by rapidly spinning a magnet inside a wire coil, and to use electricity to spin a shaft, which in turn drives an electric motor. Dartnell describes how electricity may be generated using windmills (the American inventor Charles Francis Brush built an electricity-generating windmill in 1887, and something similar could generate electricity post-collapse), water turbines, or steam (no solar panels, sadly). Because energy will be extremely precious post-collapse, if we burn fuel to generate electricity, instead of wasting the heat thoughtlessly, we should use it for something useful, like keeping our homes warm. This is the principle behind combined heat and power (CHP) plants, common in Sweden and Denmark today.
When we think of energy today, we often think of fueling our vehicles, and transportation is the subject of chapter 9. Dartnell acknowledges that modern roads will fall apart surprisingly quickly post-apocalypse, and pointedly remarks that “for the first time SUVs will become necessary to get around urbanized areas.” Gasoline will not last long, either. Diesel engines can run on biodiesel made from plant oil, but survivors will need all the arable land they can get for feeding themselves, not their cars. Alternatively, cars can be powered by organic gas (actual compressed gas, not the abbreviation for “gasoline”), such as methane, propane, and butane. Dartnell describes how survivors can gasify wood to keep their cars running. Unfortunately, here we run into another problem: the need for rubber to make tires. Tires cannot be recycled, Hevea trees (the source of latex for making rubber) grow only near the equator, and synthetic rubber production is “fiendishly tricky,” so “reestablishing long-distance trade [of rubber] will be one of your top priorities” (p. 195).
If things really go south, and mechanized transport is lost, survivors may have to make do with ox- and horse-drawn vehicles. Dartnell describes the horse collar, invented in ancient China, which allows the horse to pull heavy loads without becoming strangled, unlike the strap-based harness used in ancient Egypt and Rome. After discussing sailboats and bicycles, the author goes into a detailed description of an internal combustion engine. I had never given much thought to internal combustion engines before reading this chapter, and I was amazed by how many different inventions, some of them ancient, had to be put together in a novel way in order to make this staple of the modern world. While he calls the internal combustion engine “a miraculous contraption” (p. 206), the author acknowledges that it may not be the most practical thing in a world devoid of easily accessible petroleum deposits, and he recommends that the post-apocalyptic society build electric cars instead.
Along with transport, the post-apocalyptic society will need to reestablish long-distance communication. Chapter 10 starts with the most ancient form of long-distance communication: handwriting, which requires paper and ink. Paper was invented in ancient China, and Dartnell describes how to make it post-collapse: chop tree trunks and branches into small pieces and boil them in an alkaline solution for several hours. The alkali will break down lignin in the plant matter, releasing cellulose fibers, which will float to the top of the solution and can be skimmed off with a sieve. Then put the cellulose fibers on top of a wire mesh or cloth screen to allow the water to drain out, and voila! Sheets of paper. To make the paper white, you will need bleach (aka sodium hypochlorite, NaOCl), which can be made from chlorine gas plus caustic soda. As for ink, Dartnell recommends a recipe from medieval Europe, called iron gall ink. As its name implies, it contains iron (specifically, iron sulfide, made by reacting iron with our old friend sulfuric acid) and organic acids extracted from galls (growths on oak trees caused by parasitic wasps laying their eggs there). The author waxes poetic about it:
“[T]he history of Western civilization itself was written in iron gall ink. Leonardo da Vinci wrote his notebooks with it. Bach composed his concertos and suites with it. Van Gogh and Rembrandt sketched with it. The Constitution of the United States of America was committed to posterity with it” (p. 213).
To achieve widespread literacy, handwriting will not suffice. Survivors will need to reestablish movable-type printing, invented by Gutenberg in the 15th century and described in loving detail by Dartnell. The author rounds out the chapter on communications with electric-based ones, namely radio (which is simple enough to use that we can leapfrog right over the telegraph, he says). He briefly gestures in the direction of using vacuum tubes to build post-apocalyptic computers, but email and social media are not part of the post-collapse society, as far as this book is concerned.
In chapter 11 (advanced chemistry), Dartnell makes a point I had not thought of before reading this book: we usually think of the Industrial Revolution as replacing human muscle strength with machines, but just as important was the ability to synthesize essential chemicals at scale. Better living through chemistry, 19th century-style! As the human population recovers post-collapse, humanity will need to recover this ability, lest progress stall due to shortage of essential ingredients. Dartnell mentions electrolysis, the use of electricity to split chemical compounds (e.g., running an electric current through seawater yields chlorine gas and hydrogen gas, both useful substances), the synthesis of explosives, and photography.
Explosives are important for quarrying, mining, making tunnels, and demolishing old buildings to recycle their components. An explosive works by rapidly converting a solid substrate into an expanding bubble of hot gas. The ancient Chinese developed a type of explosive, gunpowder, made of one part saltpeter (potassium nitrate, KNO3), one part sulfur, and six parts charcoal. A traditional source of nitrate is manure, which contains bacteria that convert atmospheric nitrogen to nitrate. So, to make saltpeter, you need a nice big pile of dung, plus some calcium hydroxide and potassium carbonate, aka slaked lime and potash, both introduced in Chapter 5. Pour a bucket of calcium hydroxide solution over a manure pile, and the fluid that drains out will contain calcium nitrate. Mix it with potash, and the ions will swap partners, resulting in calcium carbonate and potassium nitrate: Ca(NO3)2 + K2CO3 → CaCO3 + 2 KNO3. The calcium carbonate will precipitate out; take the solution, then boil away the water and you are left with saltpeter crystals. A stronger explosive than gunpowder is nitroglycerin, made of nitrate and glycerol, which is a byproduct of making soap (see chapter 5). Alfred Nobel made his fortune by developing a way to make the extremely unstable nitroglycerin less dangerous to use: he let the nitroglycerin soak into something solid, like a stick of clay, thus making dynamite.
A long description on how to take photographs then follows: “[Y]ou can take a primitive photo using substances derived from a silver spoon, a dung heap [nitrate again], and common salt” (p. 242). Dartnell rounds out chapter 11 with a detailed description of two key substances: soda ash (aka sodium carbonate) and nitrate.
As mentioned in chapter 5, soda ash can be made out of seaweed, and harvesting seaweed and processing it into soda ash was a traditional occupation along the western shores of Scotland and Ireland (hi, Deiseach!). However, for industrial-scale synthesis of soda ash, survivors will want to turn to the Solvay process, invented by the eponymous Belgian chemist in the 1860s. Put bubbles of ammonia and carbon dioxide through a column of seawater; the gasses will dissolve in the brine and form ammonium bicarbonate, which then reacts with the sodium chloride in the water to form sodium bicarbonate: (NH4)HCO3 + NaCl → NaHCO3 + NH4Cl. Sodium bicarbonate cannot dissolve in the alkaline solution, so it forms a sediment, which can be collected and then baked to yield the desired final product, Na2CO3, along with water and carbon dioxide. The great thing about the Solvay process is that it recycles ammonia: ammonia gas reacts with brine to form ammonium chloride, which is then combined with calcium oxide, yielding ammonia gas plus calcium chloride as a byproduct. The only feedstocks are seawater and limestone, both of which are plentiful and nontoxic. The limestone is the source of both carbon dioxide and calcium oxide for the reactions above. Excellent!
Along with soda ash, nitrate (NO3-) is another substance that will become limiting as civilization recovers:
“The use of nitrates in both fertilizers and explosives meant that they had become a crucial commodity by the end of the nineteenth century, and wars were fought over tiny barren islands for the bird shit they were encrusted in” (p. 238).
To avoid both starvation and the indignity of fighting over avian excrement, survivors should employ the Haber-Bosch process. Discovered in 1909, the Haber-Bosch process reacts atmospheric nitrogen with hydrogen gas to produce ammonia, which can then be made into nitrate. Hydrogen gas can be made out of water by electrolysis, as mentioned earlier in the chapter, and iron and potash are used as catalysts. Unfortunately, this process requires high temperature and extremely high pressure (450oC and 200 atmospheres) to run, so building a suitable reactor will be extremely difficult for a post-apocalyptic society. Dartnell’s best suggestion is to scavenge a pre-collapse Haber-Bosch reactor.
Once you have ammonia, you can burn it in the presence of a platinum-rhodium catalyst (scavenged from catalytic converters of defunct pre-collapse cars) to make nitrogen dioxide, which forms nitric acid when dissolved in water. Said nitric acid can then be used to make nitrate salts. Mix nitric acid with ammonia in equal parts to make ammonium nitrate (NH4NO3), an excellent synthetic fertilizer – not too alkaline, not too acidic, and a double dose of bioavailable nitrogen to keep crop plants happy.
In chapter 12, Dartnell turns to a much more rudimentary problem: how to tell what time of day and year it is, and where you are. He points out that these are not trivial concerns; they are vital for coordinating activities, knowing when to sow crops, navigating, and exploring. Again, he starts out with ancient options for telling time – the sundial and the hourglass – before describing how to make a mechanical clock. He then describes how to tell the time of year using the movement of the sun and stars. But what if we lose track of what year it is post-collapse? The solution lies in the way stars shift their location relative to one another, called proper motion. The star with the fastest proper motion is Barnard’s star, which is not visible to the naked eye, but can be seen with a rudimentary telescope. “Over a human lifespan, [Barnard’s star] races almost half the diameter of a full moon” (p. 263). Therefore, if our descendants can find Barnard’s star in the sky, they will be able to tell approximately what year it is by comparing the location of the star to the diagram on p. 263 of The Knowledge, assuming they don’t just rename the year of the apocalypse “Year Zero” and call it a day.
As for finding our way in space, our civilization has divided the earth’s surface into a grid, with lines of longitude running north-south and meeting at the poles, and lines of latitude running east-west. The equator is 0 degrees latitude, and the prime meridian (0 degrees longitude) arbitrarily runs through Greenwich, England for historical reasons. Post-apocalypse, survivors will need a way to tell their latitude and longitude.
Latitude is easier: we can tell it by measuring the angle between the horizon and stars in the sky. This can be measured with a sextant, which was developed in the 1750s and can be made using techniques described earlier in the book (metalworking, lenses, and a mirror). Longitude is more difficult to measure. Working from first principles, we know that the earth spins 360 degrees in 24 hours, and 360/24 = 15, so if noon at location A is one hour after noon at location B, then A and B are separated by 15 degrees of longitude. So, to tell your longitude, you need to measure the local time using a sextant to determine the elevation of the sun and then compare the local time to the time at the prime meridian. Theoretically, survivors could make a spring-based clock, which is unaffected by the movement of a ship (unlike a standard grandfather clock), set it to the prime meridian time, and carry it with them as a reference. However, such clocks are advanced precision instruments, likely beyond the capacity of a recovering civilization to make. Instead, Dartnell recommends communicating the reference time to faraway locations by radio, described in chapter 10. He conjures a steampunk-y image: old-fashioned tall ships sailing the seas with radio antennae attached to their masts.
One of the joys of reading this book was learning a lot of weird and wonderful facts about the world. Before we move on to the thirteenth and final chapter, here is a selection of interesting facts:
Chapter 13 is titled “The Greatest Invention.” Before telling us what it is, Dartnell allows himself a bit of philosophical musing, something he has avoided for most of the book. In a way reminiscent of Jared Diamond and Joseph Henrich, he asks: Why did the Industrial Revolution begin in 18th-century Britain? China had had a huge advantage in technology over Britain or anywhere in Europe for centuries. Ancient China had invented gunpowder, paper, block printing, the horse collar, blast furnaces for smelting iron, etc. Why did the Industrial Revolution not start in China? The answer: sociology matters, not just technology. 18th-century Britain had abundant energy from coal deposits plus relatively expensive labor; in China, labor was cheap and plentiful. Therefore, the British had a strong incentive to automate and hence save on labor costs, and their Chinese contemporaries did not. Once the Industrial Revolution began in Britain, it became a self-reinforcing cycle, with innovation begetting innovation.
This answer has disturbing implications. If both sociological and technological conditions must be right, at the same time, for an Industrial Revolution to happen, then it may be that our post-apocalyptic descendants never achieve Industrial Revolution 2.0, Dartnell writes. As a big fan of the well-being brought about by industrialization and innovation, I can only hope that memories of what life used to be like will survive the apocalypse and inspire our descendants to reboot an advanced civilization (hopefully without nuclear weapons).
Dartnell then tells us what he thinks the greatest invention is: it’s the scientific method, which will be indispensable post-apocalypse to recover knowledge that has been lost and to discover what has not been known before.
A prerequisite for scientific experiments is being able to measure things accurately using a standardized measurement system, so that the results can be communicated to others. Dartnell extols the metric system as superior, and as a European-born scientist, I agree. It’s reassuringly logical, with units spanning orders of magnitude and standardized prefixes indicating which level of magnitude you are using (giga, kilo, micro, etc.). There are no nanomiles or gigapounds.
The metric system has seven basic units, including length (meter), mass (gram), time (second), and temperature (degree Celsius). From the meter, you can reconstruct the standard unit of volume, mass, and time. If you make a hollow cube with interior dimensions of 10 cm (0.1 m), the volume of the cube is one liter. If you fill this cube with ice-cold pure water, the water weighs one kg (1000 grams). And if you make a pendulum 99.4 cm long, its period is one second. Helpfully, Dartnell provides a 10-cm line at the bottom of p. 284 as a reference for reconstructing the meter. The author also describes how to construct a barometer and thermometer for measuring pressure and temperature, respectively.
Once we have some measuring tools in hand, we will be able to conduct scientific experiments. Dartnell’s scientific spirit shines through in his definition of an experiment as “asking a clearly worded question of the universe and eagerly watching how it responds” (p. 287). I found his description of science beautifully inspiring:
“[S]cience isn’t listing what you know: it’s about how you came to know. It’s not a product but a process… the most effective way of deciding which explanations are right and which are wrong” (p. 289, emphasis in the original)
Furthermore,
An “inquisitive, analytical, evidence-based mind-set” is “the flame that the survivors [of the apocalypse] must keep burning … It is science that built our modern world, and it is science that will be needed to rebuild it again” (p. 291).
Preach!
Overall, I loved this book. Not only is it packed full of interesting and useful knowledge, but apart from the nightmare vision of irreversible collapse (the worst-case scenario briefly mentioned in chapter 1), the spirit of the book is admirably rational, optimistic, and humane. As horrifying as the fall of our civilization would be, Dartnell says we would rally together and use our store of technical and scientific knowledge to rebuild, to bring forth order from chaos. He does not chide us for bringing the risk of the apocalypse on ourselves by being too warlike and greedy, despoiling the environment, engaging in nuclear arms races, and so forth. Nor does he wax rhapsodic about how a post-apocalyptic world would be somehow better, purer, more in harmony with Nature than our current atomistic-individualistic-materialistic-capitalistic existence. He values our advanced civilization and is vastly more knowledgeable about and grateful for it than the average modern person, as this book amply shows.
Reading The Knowledge, I was humbled by just how much energy, materials, and technological innovation goes into the everyday objects we take for granted: the bed I sleep in, the mug I drink my tea from, the phone I scroll on for news and emails. It is terrifying to think that it all might go away someday, and at the same time, there is a sense of profound gratitude for all the inventors and discoverers of the past to whom I owe my high-tech existence. If I live in greater comfort and abundance than the kings and queens of the past, it is by standing on the shoulders of those who developed all the material goods and processes described in this book.
For the most part, Dartnell focuses tightly on the technological-material side of the civilization reboot, not the political or sociological aspects. There is no speculation about, say, what forms of social organization or government may arise in the aftermath. As for art, he writes plainly,
“This book will focus on the critical science and technology as they are universal … Art, literature, and music are an important part of our cultural heritage, but the recovery of civilization won’t be held back half a millennium without them, and the post-apocalyptic survivors will develop their own expressions that hold relevance to them” (p. 16).
Aside from a few poetic and philosophical passages such as those I cited above, Dartnell’s prose is workmanlike, although he allows himself occasional tidbits of humor: the practice of fertilizing fields with human feces is called “crap into crop” (p. 73); immediately after the apocalypse, survivors should head out to the nearest golf course to scavenge rechargeable lead-acid batteries from golf carts, “not for a relaxing 18-hole round to help ease the stress of the end of the world” (p. 47). For the most part, the author keeps us moving briskly. Come along, there’s lots of ground to cover, he seems to be saying; I don’t have time for flowery prose here.
There is indeed a ton of ground to cover, far more than any 340-page book (including bibliography and index) can do, and herein lies my main criticism of the book. The level of detail is like asking someone in NYC how to drive to LA and being told, “Drive toward the setting sun, and when you get to the huge water, turn left.” It’s certainly helpful if you’re starting from zero, but plenty of useful data are being left out.
The book assumes a fair amount of basic scientific knowledge on the part of the reader. I found the biology parts (agriculture, medicine) and the chemistry parts easy to understand, but a lot of the mechanical and electrical information went over my head. Partly it’s because physics and mechanical engineering are not my areas of expertise, and partly because detailed descriptions of complex machines are difficult to understand unless you can refer to a diagram or have seen such a machine before. If civilization ever comes to depend on my ability to construct a radio receiver, lathe, or steam turbine based solely on the information in The Knowledge, we are well and truly doomed.
I don’t have a great solution to this problem, but here are a few suggestions. First, I wish Dartnell had included a lot more diagrams in the book, although I understand that would have made the book both longer and more expensive. There are diagrams and illustrations in the book, but most of them show an overview of the device in question, rather than a detailed schematic of what the different parts are and what fits in where, such as you would need if you were attempting to build the thing. Secondly, Dartnell thanks a large group of subject-matter experts in the Acknowledgements, which is good, but I wish he had recruited more test readers for this book before publishing it – people like me, who are well educated in some areas and abysmally ignorant about others. Had he recruited me, I could have told him that the part about AC/DC and how transformers step voltage up and down made no sense to me and assumed knowledge about the nature of electricity that I don’t have. In parallel, another test reader presumably would have told him, “The part about transformers is great, but what is nitrogen fixation again and why should I care?” Had Dartnell incorporated such feedback from a diverse set of readers, it would have improved the book immensely, albeit at the cost of making it longer. In case it sounds like harsh criticism of Dartnell, I reiterate that I have tremendous respect for his having pulled together so much knowledge from such disparate domains in such a succinct format.
The Knowledge made me think of a piece titled “Reality Honks Back” by N.S. Lyons, posted on his Substack, The Upheaval, on 2/16/22. It’s about the Canadian truckers’ protest, which Lyons uses as a backdrop to discuss the society-wide conflict between two groups, which he calls Physicals and Virtuals. Physicals work with their hands and achieve tangible things in the real world; Virtuals work with their minds and get paid to come up with opinions and ideas. My philosophy is diametrically opposed to that of Lyons; he portrays the Physicals as decent, hardworking, salt-of-the-earth patriots oppressed by the evil Virtuals, who are simultaneously arrogant, cowardly, and weak. As a proud member of Team Virtual, I certainly disagree with the writer’s condemnation of my tribe as evil, but I think Lyons is correct to point out the division, and the acrimony, between Physical and Virtual people.
I bring this up because in the aftermath of the apocalypse we, meaning humanity in general, won’t have the option of dividing ourselves into Physicals and Virtuals anymore if we are to survive. We will need every bit of intellectual acumen, physical prowess, and manual dexterity to reboot civilization, as Dartnell’s book shows. And when you step back from our current political climate, you see no need for Physicals and Virtuals to be enemies. The motto of one of the most renowned institutions of higher learning in the world, MIT, is Mens et Manus, Latin for Mind and Hand. The virtual and the physical, working together in harmony to improve our world.
So here is my final suggestion: Maybe our society should start valuing the ability to tinker and work with one’s hands as much as we value academic knowledge. I don’t know what form such valuing would take. More shop classes in grade school? More voluntary associations where people learn how to make a lathe out of aluminum smelted in their backyard or things of that nature? I know that the idea of getting more kids to take shop classes is as old as the hills, but it’s usually treated as a consolation prize: “Oh, you aren’t gifted enough to become a computer programmer, let’s train you to be an electrician!” This isn’t my goal. I’m suggesting that we, as a society, should try to apocalypse-proof ourselves by sprinkling more bits of practical knowledge of the kind described in Dartnell’s book throughout the population. Perhaps “apocalypse-proofing” society in such a hands-on way, in addition to fighting climate change and AI risks, is a project that would appeal to some EA activists or ACX readers, to whom I heartily recommend Dartnell’s remarkable book.