What is heat? What is temperature? What is energy? What is time? When we look beneath the surface of these everyday terms to learn how scientists understand them, we encounter a realm of fundamental processes that rule the universe.

What is heat? What is temperature? What is energy? What is time? When we look beneath the surface of these everyday terms to learn how scientists understand them, we encounter a realm of fundamental processes that rule the universe.
Matter is the raw material of the universe. Stars, planets, mountains, oceans, and atmospheres are all made of matter. So are plants and animals—including humans and every material thing we have ever produced. Amazingly, this immense variety is generated by a limited number of chemical elements that combine in simple, well-defined ways.
Everything we now know about the universe—from the behavior of quarks to the birth of entire galaxies—has stemmed from scientists who’ve been willing to ponder the unanswerable. And with the advent of modern science, great minds have turned to testing and experimentation rather than mere thought as a way of approaching and grappling with some of the universe’s most pressing and vexing dilemmas.
The search for, and ultimate discovery of, the Higgs boson is a triumph of modern physics—a global, half-century effort whose outcome would make or break the vaunted Standard Model of particle physics. The hunt for the Higgs was the subject of wide media attention due to the cost of the project, the complexity of the experiment, and the importance of its result. And, when it was announced with great fanfare in 2012 that physicists succeeded in creating and identifying this all-important new particle, the discovery was justly celebrated around the world.
Robots. The mere word conjures up a bevy of mind-bending images pulled straight from popular science fiction tales. But robots aren’t just the stuff of entertainment. They’re real. They’re everywhere around you. And they’re transforming your life in ways you can’t imagine.
Why does a curve ball curve? Why does ice float? What’s the perfect way to cook egg custard? How do CDs and DVDs work? Why don’t your legs break when you jump off a chair? What keeps a moving bicycle from falling over? These questions involve physical principles that relate not only to interesting aspects of our daily lives, but also explain such phenomena as the cause of hurricanes, the formation of neutron stars, the ability of water to dissolve different substances, and other fundamental features of reality.
For thousands of years, the star-filled sky has been a source of wonder, discovery, entertainment, and instruction. Ancient people from nearly every continent and culture wove exciting stories about the mythological figures they saw in the heavens. People also used the sun, moon, and stars for time-keeping and navigation. And careful observers throughout Europe, the Middle East, Asia, and elsewhere kept precise astronomical records, eventually paving the way for the Scientific Revolution and its remarkable discoveries about the nature of the universe.
The story of Earth is an epic filled with crises, catastrophes, and remarkable, repeated change. Earth traces its origin to simple atoms that were created in the big bang, transformed into heavy elements in stellar explosions, and then forged into a planet inside the nebula that gave birth to the solar system. Like many other planets, Earth went through phases of melting, volcanism, and bombardment by asteroids. But only on Earth did events lead to a flourishing biosphere—life. And once life was established, it drove the evolution of our planet in startling new directions.
Earth’s ocean is a source of wonder, delight, sustenance, economic benefit, and awe in the face of its overwhelming mystery and power. It dominates the natural world in ways that scientists are only now beginning to understand. And although we call our home planet Earth, it would be more accurate to name it Ocean, since 71% of the globe is covered with water, and beneath the waves churn forces that make our world unique in the solar system:
Nuclear radiation is everywhere. At this moment, byproducts of cosmic rays are raining down on you from the galaxy, neutrinos produced in the Sun are piercing your body by the trillions, and nuclear particles from everyday sources in rocks, air, food, and water are bombarding you from all directions. If you had a supersensitive “Geiger counter” that picked up all nuclear particles, it would chirp nonstop.
Enchanting and otherworldly in their beauty, the polar regions are some of the most isolated and least understood places on Earth. Until relatively recently, few non-indigenous people had experienced their immense majesty. And yet, while remote, these extreme environments are endlessly fascinating, and eminently worthy of witnessing firsthand, especially if you are prepared to understand what you are seeing.
An invisible world of astonishing complexity is all around you. A world so small you can’t see it with the naked eye. A world so crowded that its population staggers the mind. A world in which you participate every day—often without even knowing it.