Stars, Clocks and the Secret Clockwork of America

On a hill above Washington, D. C. , a team of scientists watches the sky. They belong to the U. S. Naval Observatory, or USNO for short. Their job is simple: keep track of the stars and the exact moment in time. Since 1873 a telescope at USNO has watched bright stars every night. The data they gather helps ships that travel far from shore. Without the stars, a sailor could not find their way in the dark. The observatory also runs a huge time‑keeping system. Its Master Clock contains more than 100 atomic clocks that tick in perfect harmony. Because atoms vibrate at a constant rate, the clocks stay almost perfect forever. USNO has been sending accurate time to people all over the world since 1880.The information is used by stock traders, pilots, and GPS devices. If the clocks were wrong, a car could be off by a mile or a stock trade could be mis‑dated. Modern GPS needs the precise timing that USNO supplies. The satellites rely on those atomic clocks to calculate positions on Earth. Without a trustworthy source of time, the whole system would fall apart. The observatory’s building also has history. An old house on the site once housed a Navy commander. In 1974, Congress turned that same building into the official residence of the Vice President. So next time you glance at your phone’s clock, remember the stars and the clocks that keep it right.