Every holiday season, tourists throng Rockefeller Center to see the famous tree, soaring above the paved plazas and fountains. But more than 200 years ago, they would have found avocado and fig trees there, along with kumquats, cotton, and wheat—all specimens belonging to the Elgin Botanic Garden, founded by physician and botanist David Hosack.

Hosack grew up in the shadow of the American Revolution and became fascinated with the healing powers of plants as a young doctor studying abroad. Upon returning to the young United States, he founded America's very first botanical garden, in the model of the great European gardens, as a place where he could study crops and medicinal plants.

He was close friends with both Alexander Hamilton and Aaron Burr (he was the attending physician at their fatal duel) and went on to help found many of New York City's civic institutions, such as Bellevue Hospital and the New York Historical Society, along with the first obstetrics hospital, mental hospital, school for the deaf, and natural history museum.

"Hosack started with his garden, and ended with making New York New York," says Victoria Johnson. She tells the story of Hosack's life in her book American Eden: David Hosack, Botany, and Medicine in the Garden of the Early Republic.

Yet Hosack has been largely forgotten by history, overshadowed by names like Rockefeller and Carnegie, even though he was legendary in the generations after his death. In this segment, Ira braves the crowds of Rockefeller Center on a hunt for Hosack's commemorative plaque, and interviews Johnson for the unheard story of this forgotten revolutionary hero.

What are your resolutions for 2019? If the answer is “explore a frozen, primitive planet-like body,” you have something in common with New Horizons, the spacecraft that dazzled the world with close-ups of Pluto in 2015. Its next stop? The first fly-by of an object in the distant Kuiper Belt.

New Horizons has been flying further away from us in the years since, and will soon encounter Ultima Thule, a small object about the size of New York City that may be able to tell us more about the origins of our solar system. Ultima Thule is thought to have been frozen and undisturbed for more than 4.6 billion years—a potentially perfect time capsule of the solar nebula that gave rise to Earth and its neighbors.

Ira talks to Alan Stern, principal investigator of the New Horizons mission, about the New Year’s Eve fly-by and the treasure trove of data his team is hoping to unwrap.