Let us start with the bathtub. You know the story. King Hiero II of Syracuse gives a goldsmith a lump of pure gold and commissions a new crown. The crown comes back looking beautiful, weighing exactly what it should, but the king suspects the goldsmith has secretly mixed in cheaper…

On a spring day in 1833, a wire ran from the physics laboratory at the University of Gottingen to the astronomical observatory about one kilometer away. At each end sat a device built from copper coils, magnets, and a galvanometer, a needle that deflected when electric current passed through it.…

In 1687, Isaac Newton published three laws of motion in his Philosophiae Naturalis Principia Mathematica. The third law is the one most people can recite from memory, even if they have forgotten everything else about physics: for every action, there is an equal and opposite reaction. It sounds simple. Almost…

Open a first edition of On the Origin of Species and flip to the one illustration in the entire book. Just one. In a 490-page work that overturned humanity’s understanding of life on Earth, Darwin included a single figure: a branching diagram showing how species diverge from common ancestors over…

In 1905, atoms were still controversial. Not in the way that new scientific ideas are usually controversial, argued over at conferences and then gradually accepted. Atoms were controversial in a deeper way. Some of the most respected physicists and chemists in the world genuinely believed they did not exist. Ernst…

Somewhere in the ocean right now, trillions of single-celled organisms are building skeletons of glass. Not metaphorical glass. Actual glass, amorphous silica, the same basic material as a windowpane. These organisms are radiolaria, and their skeletons are among the most intricate structures produced by any living thing on Earth. Each…

In December 1995, the Hubble Space Telescope did something that many astronomers thought was a waste of time. It pointed at a tiny, seemingly empty patch of sky near the Big Dipper, a region with no known galaxies, no bright stars, nothing of obvious interest. It stared at it for…

In the autumn of 1936, a shy, awkward, twenty-four-year-old Englishman arrived at Princeton University with a typewriter and a radical idea. His name was Alan Turing. He had just published a paper that defined the theoretical limits of computation, what any machine could, or could not, ever calculate. At Princeton,…

In the basement of the Bibliotheque nationale de France in Paris, there is a collection of notebooks that cannot be casually browsed. They sit in lead-lined boxes, carefully preserved and carefully contained. If you want to read them, you must sign a liability waiver and wear protective clothing. These are…

Some of the most powerful ideas in physics sound almost too simple when you first hear them. Here is one: every point on a wavefront acts as if it were a tiny new source of waves, sending out spherical ripples in all directions. The new wavefront is just the surface…