In Arizona, nature is diverse and dramatic. The state's Tonto Natural Bridge State Park is home to the world's largest natural travertine bridge, where visitors can hike and explore its unparalleled ...

In the early 1990s, eight people agreed to vanish from the world and live for two years inside a sealed glass habitat in the ...

ORACLE, Ariz. — Plopped in the Sonoran Desert, just outside Tucson, Ariz., sits a massive, multilevel greenhouse that's probably best known as the inspiration for a Pauly Shore movie. A slick, stepped ...

From a distance, Biosphere 2 emerges from the cacti and creosote of the Sonoran desert like a gleaming oasis, a colony of glass and bright white structures. Despite being just outside Tucson, Arizona, ...

Earth's rotation is randomly speeding up, and nobody is quite sure why. These speedups, which have occurred several times over the last few years, haven't had any effect on daily life, but they also ...