Skip to Content

Summary: How the World Really Works: The Science of Our Past, Present and Future by Vaclav Smil

How the World Really Works (2022) tackles a paradox at the heart of the modern world: we’ve never had so much information at our fingertips and never known so little about how things actually work. Of course, we can’t be experts in everything. But, Vaclav Smil argues, it’s our duty as citizens to be informed about the basics – the big questions that shape our societies and their futures.

Introduction: Learn the fundamentals behind energy use and food production.

In the year 1500, it was just about possible to meet a real Renaissance man – a savant who knew everything. Think of Leonardo da Vinci, whose knowledge extended from hydraulics to aviation and anatomy.

By the eighteenth century, though, such a figure no longer existed. When France’s greatest minds set about compiling an encyclopedia containing everything worth knowing, they needed a team.

Today, our understanding of the world has advanced so far that even an encyclopedia running to thousands of volumes couldn’t do it justice. Knowledge is so specialized that it can take a lifetime to master a single discipline. A particle physicist – let alone a professional historian – would find it very difficult to understand the first page of a new research paper in viral immunology.

But that doesn’t excuse our lack of understanding of the fundamental workings of the world. We can’t expect everyone to understand cutting-edge research in neurobiology, but we can expect them to understand, say, how the food on their plates was made.

That’s the argument Vaclav Smil makes in How the World Really Works. For Smil, such knowledge is vital to the functioning of democracies. If we don’t have that knowledge, we won’t be able to make informed decisions about the most important issues of the day.

In How the World Really Works, Smil zooms in on seven topics he thinks all of us need to know about. For this summary, we’re going to narrow that down to two: energy and food.

Book Summary: How the World Really Works - The Science of Our Past, Present and Future

In this summary, you’ll learn

  • how our planet’s atmosphere came to support animal life;
  • why fossil fuels allow us to feed almost eight billion people; and
  • how electricity makes the world go round.

The history of life on our planet is a history of energy conversions.

Let’s start at the beginning – the very beginning. Some three and a half billion years ago, when much of our planet’s surface was little more than primordial soup, a new form of life emerged: simple, single-cell microbes.

These bacteria didn’t have consciousness or mobility: they merely drifted aimlessly through Earth’s seas. But they did have metabolism – the ability to convert one form of energy into another. That was how they accessed the nutrients they needed to survive and reproduce. The first form of energy was solar radiation from the sun. They used that energy to convert carbon dioxide and water into new organic compounds. While doing so, they created a by-product – oxygen.

This process, which is called photosynthesis, changed the planet’s atmosphere. Before these microbes began photosynthesizing, it was oxygenless; but after hundreds of millions of years, the atmosphere had enough oxygen to support life as we know it. Life, in other words, began with energy conversion. And it continued that way, too. The entire history of our planet is a history of energy conversions.

For example, several hundred thousand years ago, there was another epochal shift. This was the first extrasomatic use of energy – that is, the conversion of energy outside the body. Previously, all energy conversion had occurred inside the cells of living things. More metabolism, in short. Cells unlocking nutrients by converting one form of energy into another. That’s when a bunch of unusually clever apes – our ancestors – discovered the controlled combustion of plant matter.

Fire converts the chemical energy of plant matter, be it wood or peat or coal, into thermal energy and light. Homo sapiens began by using wood, of course – coal came much later. But that was enough to make indigestible foods edible, keep their shelters warm, and scare off dangerous animals. The use of fire was humanity’s first step on the long road to reshaping and controlling its environment.

The domestication of animals some 10,000 years ago is another milestone in the history of energy conversions. Before humans learned to put animals like oxen to work, they relied on their own muscles to convert chemical energy into the kinetic and mechanical energy which hauled loads, plowed fields, and drew water from wells. Domestication outsourced that role to beasts of burden. Later innovations, like sails and waterwheels, delegated that work to the wind and flowing rivers.

Then comes the next milestone – the use of fossil fuels – which brings us into the modern age. After around 1600, humans started burning coal, a fuel created over millions of years as heat and pressure fossilized plant matter. Coal gave us the steam engine – the iron workhorse which powered early industrialization. After around 1850, the history of energy conversion picks up tempo, giving us ever more new energy sources: crude oil, electricity-generating water and wind turbines, geothermal electricity, and then nuclear and solar power.

The abundance of useful energy has changed every facet of human existence. It allows us to work less, eat better, travel more, and communicate more efficiently. Put differently, if you want to understand the miracle of modern life, you have to start with how we convert energy.

Energy is the ability to do work.

Energy conversion, in short, is the basis of all life. It powered human evolution and allowed our species to dominate the planet. No one knows this better than physicists.

In 1886, Ludwig Boltzmann – one of the founders of thermodynamics – came to the conclusion that energy is the heart of everything. All life, he said, is a struggle for free energy – the energy that’s available for conversions. Erwin Schrödinger, the winner of the 1933 Nobel Prize for Physics, agreed. Every organism feeds on free energy, he wrote, and the organisms that best capture that energy hold the evolutionary advantage. We’ll come back to that, but let’s pause first to pose a fundamental question:

What is energy, anyway?

The etymology of the word, which goes back to ancient Greece, is a good place to start. It comes from the noun enérgeia, meaning “work.” And that’s pretty much the standard scientific definition: energy is the ability to do work.

In physics, work refers to the physical act of producing a change of configuration in a system in opposition to a second force which resists change. That’s a technical way of saying that work is the force that causes things to move. Energy, in other words, is about motion. If you hold a tennis ball out of a second-floor window, for example, it has potential energy – the potential for creating motion. If you drop it, that potential energy is transformed into the kinetic energy of movement.

All energy can be converted. The food you eat is a store of chemical energy; when you go for a run or tidy up, it’s transformed into kinetic energy. The chemical energy in coal, meanwhile, can be converted into mechanical energy – the force moving the pistons attached to a steam engine.

And that, really, brings us back to what energy is all about: conversions. That’s because it can’t be created or destroyed; it can only change form. This is known as the conservation of energy, which is the first law of thermodynamics.

You can see how this works if you imagine a cardboard box sliding down a loading bay ramp.

When it was sitting at the top of that ramp, the box had potential energy. But then an accidental push sent it speeding down the ramp, converting potential energy into kinetic energy. But the box slows as it comes down the ramp: friction opposes its motion. The box’s kinetic energy isn’t lost, though – it’s converted into thermal energy, which heats both the box and the ramp. What has been lost, here, is the ability of this kinetic energy to perform useful work: it can no longer move the box.

That, in a nutshell, is the physics of energy. But let’s make things a little less abstract.

We just quoted Schrödinger’s view that organisms which best capture free energy – energy available for useful conversions – hold the evolutionary advantage. That’s a pretty good description of Homo sapiens. So let’s take a look at one of the most important ways in which our species has captured energy: agriculture.

Fossil fuels revolutionized agriculture.

Between 1950 and 2019, the globe’s population rose from 2.5 billion people to 7.7 billion. More mouths to feed didn’t mean more people going hungry, though. In fact, the worldwide share of undernourished people actually fell – from 65 percent in 1950 to just 8.9 percent in 2019.

So what explains this dramatic reduction of malnutrition? One answer is that our crops yield more food than before. That in turn is down to better crop varieties, improved fertilizers, better irrigation, and the mechanization of agriculture. But all those things are inputs. What made them possible? The answer is fossil fuels.

Modern food production is hybrid – it relies on two different kinds of energy conversions. The first type is as old as life on this planet. Everything we eat, from plants to animals, is the result of photosynthesis. Solar radiation powers food production as it has since the dawn of agricultural civilizations 10,000 years ago. Without the sun, there simply wouldn’t be anything to harvest.

But solar radiation alone can’t explain today’s high-yield crops. They also rely on fossil energies like gas and oil. Labor-saving machines, like combines, require diesel to harvest crops; so do the trains, trucks, and barges which bring crops to market. Irrigation pumps, crop processing, and drying machinery run on gasoline. And the factories which manufacture the steel, rubber, plastics, glass, and electronics that go into tractors, combines, trucks, silos, and greenhouses also run on fossil fuels.

That’s only half the story, however. High-yield crops are intensely managed crops: you need fungicides, insecticides, and herbicides to minimize losses and fertilizers to boost growth. That, too, is fuel-intensive. Take nitrogen fertilizer. On average, farms use between 100 and 200 kilograms of it per hectare, making it the most important indirect energy input in farming. Plant life is impossible without nitrogen. It’s in every living cell. It’s in the chlorophyll which powers photosynthesis and in plants’ DNA and RNA. It’s also in their amino acids – the building blocks of the proteins needed to grow and repair tissue.

Nitrogen is everywhere – over 80 percent of the planet’s atmosphere is made up of this colorless, odorless compund. Thing is, though, you mostly encounter it in its nonreactive form – a form plants can’t use. To make nitrogen available to plants, you need to split the bond between the two nitrogen atoms and unlock free nitrogen. In this state, it can combine chemically with other elements and form reactive, plant-accessible nitrogen compounds like ammonia, nitrates, and nitrites.

Some natural processes, like lightning, unlock free nitrogen, but you can’t really harness lightning as an agricultural input. What you can do, by contrast, is sow nitrogen-fixing crops, such as alfalfa. The roots of these plants are home to bacteria which convert nitrogen into ammonia, thus “fixing” the nitrogen in the soil. But that takes time: you have to stop growing, say, wheat and plant alfalfa.

In the early twentieth century, German scientists worked out how to produce synthetic nitrogen fertilizers. Simply put, you upgrade natural gas by combining it with nitrogen from the air. Suddenly, there was as much fertilizer as humanity needed. The result: crop yields went through the roof, bringing us to the point where we can almost feed eight billion people. But that came at a cost of ever greater reliance on fossil fuels. Today, fertilizer production accounts for almost 1.5 percent of the entire globe’s energy supply and a huge portion of the natural gas we burn each year.

The agricultural revolution drove urbanization.

Fossil fuels powered what’s known as the green revolution – the huge increase in crop yields across the world during the twentieth century. Agricultural development didn’t just change what, or how much, we eat, though. It also changed how and where we work. To get a better sense of these big picture changes, let’s zoom in on one of the many places that revolution played out: the United States.

It’s 1801 and we’re in western New York. More precisely, we’re on the banks of the Genesee, a river which runs through a fertile valley dotted with small farms growing bread wheat. The farmers here are Americans, but they grow their wheat in the same way their ancestors did back in Europe. In fact, they grow it pretty much exactly like the ancient Egyptians did over 2,000 years ago.

They start by attaching a wooden plow with an iron-plated cutting edge to two oxen and driving that across their fields. Then they sow the seed they’ve kept back from last year. Next, they harvest the wheat with sickles before cutting and bundling it. After drying, it’s hauled into the barn and threshed. The straw is stacked and the grain is winnowed – the process of separating the wheat seeds from their tough husks known as chaff. Finally, the wheat is measured and put in sacks.

Everything is done by hand. Nothing is mechanized and everything is powered by solar radiation. All in all, it takes 120 hours of human labor plus 70 hours of ox labor per hectare. That’s about ten minutes of labor per kilogram of wheat, which is what you’d need to bake two loaves of bread.

Fast forward a century. We’re now in the Red River valley in eastern Dakota. Agriculture has already moved on a great deal. Wheat farmers use teams of four powerful horses to pull multishare steel plows. They also have mechanical seed drills and harvesters. Fossil fuels have also arrived – threshing machines, for example, are now powered by coal-fired steam engines. At 1,000 kilograms per hectare, bread wheat yields are still relatively low, but much less human labor is required to secure a wheat crop. Now, it’s just 22 hours per hectare – about one-seventh of what it was in 1801. In other words, farmers are investing between one and five minutes of their labor per kilogram of wheat.

Let’s hit the fast-forward button one last time, bringing us up to 2021. This time, we’re in Kansas – the heart of American wheat country. The world of even a hundred years ago has completely disappeared. The US Department of Agriculture stopped counting the number of draft animals on American farms in 1961, which is pretty much when diesel-guzzling tractors became ubiquitous. Every part of the process is now mechanized, including the application of inorganic fertilizers. Combines take care of harvesting and threshing before directly loading grain onto trucks. A hectare now yields 3,500 kilograms and requires just two hours of human labor. That’s just two seconds per kilogram of wheat!

The upshot of these remarkable improvements was that farming required fewer hands and produced more food. In the United States, around 83 percent of Americans worked in agriculture in 1801; by 2021, that had all fallen to just 1 percent. This same story was replicated around the world, from Denmark to China and Argentina to India. Fossil fuels, then, changed everything. They drove the mechanization of agriculture and the increase in yields. But they also severed humanity’s age-old connection with the land, driving billions of people into cities to find new work in the innovative industries which shaped the modern world.

Electricity makes the modern world go round.

Lumps of coal and canisters of gasoline are pretty tangible stores of chemical energy. When they burn, they release thermal energy – the heat which powers locomotives or motor vehicles. It’s the same with falling water. We can easily picture the water wheel which converts the river’s gravitational energy into the mechanical energy which turns a millstone.

Electricity is different. It’s less intuitive. Even physicists can’t answer the question of what exactly electricity is – they can only describe how it interacts with the world. But that’s enough to harness its life-altering power. And the effects of that can be seen everywhere.

As an energy source, electricity has many advantages. It’s always clean, for example, and mostly very efficient. A simple flip of a switch or push of a button is enough to activate thermostats, motors, heaters, and lights. There’s no need for bulky fuel storage and nothing to carry. And unlike, say, coal or gas, there’s no danger of incomplete combustion – the source of deadly carbon monoxide.

Its uses have transformed our world. Take just one application: lighting. Before electric lighting, we relied on wax candles, oil lamps, and kerosene cylinders to erase the difference between day and night. All were expensive, inefficient, and often dangerous. They were also feeble. The gas lights of early industrial cities, for example, were ten times more efficient than candles. Today’s fluorescent lights, by contrast, are 500 times as efficient. Then there are the sodium lamps we use to illuminate cities at night, which are 1,000 times more efficient!

The energy conversion which really made the difference to modern life, though, is the conversion of electricity into kinetic energy by electric motors. Electrifying machinery to lift, press, cut, and weave various goods made factories cleaner, cheaper to run, and faster. Electric trams, meanwhile, made it possible to move through vast cities, bringing workers to the gates of those factories. Between 1900 and 1930, electrification doubled American manufacturing productivity. By 1960, it had quadrupled it.

It’s hard to overstate how much we’ve come to rely on electricity. Today, the economies of developed countries are dominated by the service sector. And that sector is entirely dependent on electricity. From elevators to escalators, trash compactors, conveyor belts in warehouses, and air-conditioning units – everything runs on electricity. Regular cars now contain between 20 and 40 electric motors. And households rely on it for heating, refrigeration, lighting, and countless other smaller tasks.

Electricity also moves major resources around. Without powerful electric pumps, cities couldn’t feed water into municipal pipelines. Those pumps also move fossil fuels – above all liquid gas – from the point of extraction to the places where they are used: factories and homes. If any densely populated region were to experience severely reduced electricity supply for just a few days, it would be plunged into chaos. If an entire nation experienced such shortages, we’d be looking at an unprecedented catastrophe. Yet despite its profound importance, electricity still supplies only a relatively small share of final global energy consumption – just 18 percent. But if history is any indicator, modes of energy conversion will still continue to change well into the future.


The most important thing to take away from all this is:

The history of life on Earth is a history of energy conversions. And the history of humanity is the history of a species that has become more and more efficient in exploiting free energy. So, next time you flip a switch or take a bite of food, take a second to think about all the processes and energy conversions that went into those seemingly small luxuries.


Science, History, Economics, Politics, Technology, Environment, Business, Climate Change, Sociology, Mathematics, Probability and Statistics, History and Philosophy of Science, Social Sciences

About the author

Vaclav Smil is Distinguished Professor Emeritus at the University of Manitoba. He is the author of over forty books on topics including energy, environmental and population change, food production and nutrition, technical innovation, risk assessment, and public policy. No other living scientist has had more books (on a wide variety of topics) reviewed in Nature. A Fellow of the Royal Society of Canada, in 2010 he was named by Foreign Policy as one of the Top 100 Global Thinkers.

Table of Contents


Stay tuned for book review…

Alex Lim is a certified book reviewer and editor with over 10 years of experience in the publishing industry. He has reviewed hundreds of books for reputable magazines and websites, such as The New York Times, The Guardian, and Goodreads. Alex has a master’s degree in comparative literature from Harvard University and a PhD in literary criticism from Oxford University. He is also the author of several acclaimed books on literary theory and analysis, such as The Art of Reading and How to Write a Book Review. Alex lives in London, England with his wife and two children. You can contact him at [email protected] or follow him on Website | Twitter | Facebook

    Ads Blocker Image Powered by Code Help Pro

    Your Support Matters...

    We run an independent site that is committed to delivering valuable content, but it comes with its challenges. Many of our readers use ad blockers, causing our advertising revenue to decline. Unlike some websites, we have not implemented paywalls to restrict access. Your support can make a significant difference. If you find this website useful and choose to support us, it would greatly secure our future. We appreciate your help. If you are currently using an ad blocker, please consider disabling it for our site. Thank you for your understanding and support.