How Long Can Turtles Stay Underwater and Other Questions From Our Readers

How long can a turtle stay underwater before it needs to surface to breathe?
John Crowther
Tampa, Florida

It depends on the species, locality and temperature. Painted and other turtles living in temperate zones hibernate all winter without breathing at the surface. (The familiar box turtle also hibernates, but on land.) An Australian species, the Fitzroy River turtle, hardly ever surfaces, but obtains oxygen from water pumped through its cloaca, or posterior opening. This is probably an adaptation to limit the turtle’s exposure to crocodiles. See Donald Jackson’s wonderful book Life in a Shell for more details.
Jim Murphy
Curator of Herpetology, National Zoo

How can thunder exist without lightning, and why does my state get all the tornadoes?
Matt LaRock
Lakewood, Colorado

Thunder is always linked to lightning, but the lightning isn’t always visible. Most lightning strikes occur between clouds in the atmosphere, never reaching the ground. Tornadoes arise from strong thunderstorms and are most common in the central United States, including Colorado. But Texas and Oklahoma receive the greatest number of tornadoes.
Andrew Johnston
Geographer, Air and Space Museum

How far south in the United States has the aurora borealis been seen?
Tom Gallaher
Fort Lauderdale, Florida

Auroras typically are seen in the far north, but during high variations in the earth’s magnetic field, they’re more frequent and can occur farther south. A sighting was recorded in Hawaii in 1859, but that was long before Hawaiian statehood. Florida had a sighting in 2003.
Kelly Korreck
Solar Scientist, Harvard-Smithsonian Center for Astrophysics

Is there any evidence that early Inuit cultures in Alaska burned local coal in their fire pits?
Timothy A. Schuerch
Anchorage, Alaska

Native Alaskans fashioned coal into labrets, or lip ornaments, and other artifacts, but I know of no evidence they burned coal for heating or cooking before explorers from Europe and Russia and American whalers arrived with coal-burning stoves.
Stephen Loring
Archaeologist, Arctic Studies Center, Museum of Natural History

Does anyone know how it was discovered that artichokes were edible?
Rose Mary Taquino
Arcadoa, California

Not exactly, but we do know artichokes became a dinner staple about 3,000 years ago in Greece and Italy, where they’re indigenous. Gardeners appreciated the ease with which Cynara scolymus grew in the cooler fall and winter temperatures, and cooks developed ways to roast, fry, broil and bake the prickly flower bud. It is said that Catherine de’ Medici introduced artichokes to France. French immigrants brought them to North America’s east coast, and Spanish immigrants brought them to the west coast (where they’re much easier to grow).
Cynthia Brown
Chief Horticulturist, Smithsonian Gardens

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