Ben Lewis

At the bottom of lunar craters, where sunlight never reaches, an eternal cold reigns — about minus 240 degrees Celsius. In these icy pockets, known as permanently shadowed regions, plans are underway to install a mirror resonator made of monolithic silicon.

The world's most precise stopwatch still runs with one eye on an old pendulum. Hydrogen masers — the best radio-frequency flywheels (devices that keep the rhythm between comparisons with a reference)—accumulate error because noise between ticks leaks into the final signal.