Ernest Rutherford grew up in the 19th century. He created the 20th. No discovery struck deeper into the scientific understanding of reality, with more profound implications for civilization, than Rutherford’s revelation of the architecture of the atom. A century ago in May, Rutherford published a paper in the Philosophical Magazine interpreting experiments completed two years earlier by his assistants Hans Geiger and Ernest Marsden. They had witnessed the atomic equivalent, as Rutherford later described it, of an artillery shell bouncing backwards off of tissue paper. It was astounding, u... (p. 30)

Of all the mysteries of life and the universe, none resist the sleuthing of science’s best private eyes more obstinately than the ultimate nature of space and time. Every several centuries or so, profound insights do occur, immortalizing the names of the investigators who achieved them: Euclid (who cataloged the insights preceding him), Galileo, Newton, Einstein. Yet each advance left deeper questions unanswered. And now the 21st century’s best brains still cannot say for sure whether space and time are fundamental building blocks of natural existence, or are themselves built from mor... (p. 28)

Schrödinger’s cat was born 75 years ago. Its date of death remains uncertain. Science’s most famous feline remains perpetually both alive and dead, a mythological zombie symbolizing an enduring enigma at the heart of modern physics. It’s an imaginary cat, of course, invented by Austrian physicist Erwin Schrödinger in 1935 to emphasize the weirdness of quantum mechanics, the mathematical constitution governing the microworld. An experiment could be devised, Schrödinger showed, to put a cat in a box into a live-dead limbo (technically, a “superposition” of states) until somebod... (p. 15)

Explaining gravity to a small child is simple: All you have to say is, what goes up must come down. Until the kid asks why. What can you say? It’s just the way things work. All masses attract each other. Maybe to bright middle schoolers you could explain that spacetime is warped by mass. Or, to high schoolers, you could say that without gravity, the laws of physics would differ for people moving at changing velocities. Yet all those increasingly sophisticated answers merely invite another “Why.” As Sir Isaac Newton himself replied in response to similar questions, “hypotheses... (p. 26)