Gravity is the force we meet first — it’s what holds you in your chair. Yet the number that sets its strength, the gravitational constant known as “big G,” is the most poorly measured of all the fundamental constants in physics.

Some of the oldest letters we have were never meant to be read by us. They were personal notes, sealed in clay and never reopened, and for most of history the only way to see inside one was to crack it open and risk destroying it.

Space missions almost never get more than they planned for. Fuel budgets are set years in advance, margins get eaten by delays and course corrections, and “design life” is usually the optimistic number.

Here is a number that is hard to hold in your head: 74 femtoseconds. That is 74 quadrillionths of a second — roughly the time it takes light itself to cross the width of a human hair.

In the 1960s, surveyors looking for productive fishing grounds off the coast of Benin, in West Africa, found what looked like a deep coral reef — and concluded it was probably dead. That verdict stuck for more than six decades.

King Charles III spent September 17 doing something no monarch has done before: telling the chief executives of Nvidia, OpenAI, Anthropic, and Google DeepMind, in person, that the industry needs “sufficient means of control before it is all too late,” according to Fortune’s account of the closed-doo