How the World Really Works: A Scientist’s Guide to Our Past, Present and Future

Imagine a world where every movement, every breath, every thought depended solely on your own physical strength. This was the reality for early humans and their ancestors for millions of years. But then came a revolution—not of politics or society, but of energy. Energy, in its many elusive forms, is the invisible power behind every aspect of modern civilization. It is the capacity to do work, the force that moves mountains, powers cities, and fuels our dreams.

From the gentle warmth of sunlight that nurtures plants to the roaring combustion of fossil fuels that drives our machines, energy manifests in many guises. Yet, despite its omnipresence, energy remains an abstract concept, defying simple visualization. We know it by its effects—light, heat, motion—but the essence of energy is a mystery that has challenged the greatest minds.

Consider the journey humanity has taken: for millennia, muscle power—human and animal—was the main source of mechanical energy. Wood and other biomass provided the heat and light. Then, around the 17th century, coal began to change everything. The steam engine, powered by burning coal, ushered in the industrial age. This was only the beginning. The 19th and 20th centuries saw a cascade of energy transitions—oil, natural gas, electricity—each leap propelling civilization forward at an unprecedented pace.

Today, an average person on Earth has access to nearly 700 times more useful energy than their great-great-grandparents did at the dawn of the 19th century. This abundance underlies our ability to travel across continents, communicate instantly, and enjoy comforts once unimaginable. The energy that lights your room, moves your car, and powers your devices is part of a vast, interconnected system that has evolved over centuries.

Electricity, that intangible flow of electrons, stands out as a marvel. It lights our nights, powers our industries, and drives modern transport. Yet, it accounts for less than a fifth of total final energy consumption worldwide. Why? Because many sectors—aviation, shipping, heavy industry—still rely on dense liquid fuels derived from crude oil. These fuels pack a punch that current batteries cannot match, making them irreplaceable for now.

Understanding energy’s forms, densities, and flows reveals why rapid transitions are so challenging. For example, kerosene's energy density is about 46 gigajoules per ton, vastly surpassing that of wood or natural gas per volume. This makes it ideal for air travel, where weight and space are at a premium.

As we look forward, the challenge is clear: how do we maintain and improve our quality of life while transitioning to cleaner energy sources? The path is complex, requiring innovations in storage, generation, and efficiency. But the journey begins with understanding the invisible force that powers it all—energy.

With this foundation, let us now explore the next vital pillar of civilization—food production—and how it too is intricately tied to energy.