The rarest rhythm

Everything in nature comes and goes—stars, planets, even our bodies—but what truly endures is repetition. The universe moves to a rhythm: the Sun brings the year’s shortest day on December 21 and its earliest sunset on December 7; the Moon cycles through fullness every 29½ days and repeats its elevation pattern every 18.6 years, reaching an extreme this year. Venus, fading from the morning sky, will return as a brilliant evening star later this winter—part of its elegant 8-year cycle. Saturn’s rings, now edgewise, won’t appear this way again until 2044. Even Earth’s poles follow a 26,000-year rhythm, and we’re now living in the rare moment when Polaris serves as the most perfectly placed North Star in that grand celestial cycle.