On the first day of December 2020, dawn in Puerto Rico was spectacular. The skies blazed in shades of lilac and dusky rose, and the rising sun cast a warm glow on a giant radio telescope nestled among the karst mountains near the island’s northern shore.

Now, when the sun climbs over those mountains, it shines on the tangled ruins of a scientific and cultural treasure.

For nearly six decades, the Arecibo Observatory was Earth’s largest window to the cosmos. Its mammoth, 1,000-foot-wide dish made it exquisitely sensitive, able to capture radio waves that wash over Earth with just a millionth of the energy in a falling snowflake. High above the dish, an enormous 900-ton platform held the equipment needed