Why does the landscape remain lit 30 to 45 minutes after the sun has set?
Harriett Drake, Fayetteville, Georgia
What you’re seeing then is twilight. From wherever you’re standing, shortly after sunset—and before sunrise, too—the sun illuminates not the Earth’s surface directly, but rather the atmosphere above the surface, says Jim Zimbelman, geologist at the National Air and Space Museum, and light scattered by the atmosphere provides considerable illumination. Celestial objects without this atmosphere, such as Mercury and Earth’s moon, have little twilight.
Which battle flag did Gen. William T. Sherman fly during his March to the Sea?
C. Melton, Morton, Illinois
Unlike his fellow generals George Custer and Philip Sheridan, Sherman didn’t have a personal battle flag, says Jennifer L. Jones, chair and curator of armed forces history at the National Museum of American History. He carried the 35-star national banner—the Stars and Stripes—plus the flags of the corps he commanded, which came from the Armies of Georgia and the Tennessee. Fifteen years after the war, in 1880, he commissioned a flag depicting an eagle holding an olive branch that was used at military ceremonies as a symbol of unity and peace.
At what location in a city is its official elevation measured?
Ricardo Berry, Socorro, New Mexico
There is no national standard for such measurements, so cities and towns use their own markers, says Rossman Irwin, geologist at the Center for Earth and Planetary Studies at the National Air and Space Museum. Denver, known as the “mile-high city,” takes its elevation from the steps of the Colorado capitol, which sits on a knoll. Most of downtown Denver is actually less than a mile high.
Are there any practical applications remaining for Morse code?
Bruce Squiers, Salem, New York
Samuel F.B. Morse’s system of dots and dashes was revolutionary in the 1840s (Morse, a portrait painter, became interested in speeding up communications after his wife died suddenly while he was away from home), but Western Union sent its last telegram in 2006. Now Morse code is used largely in airplane navigational systems for identification purposes, says Paul F. Johnston, curator of maritime history at the National Museum of American History. Amateur radio operators also use it for fun.
As I sit here eating chocolate mint walnut ice cream, I find myself wondering: Do other animals intentionally mix flavors in their food?
James Lehman Jr., Laytonsville, Maryland
Animals have been observed mixing their foods—an elephant named Ambika at the National Zoo often mixes grain and hay as she eats, says Tony Barthel, curator of the Zoo’s Cheetah Conservation Station and Elephant Trail—but their purpose in doing so hasn’t been extensively studied. Wild orangutans test different foods and, in some cases, reject them based on taste, says Meredith Bastian, the Zoo’s curator of primates. And some species wash or soak their food before eating, which may be an attempt to alter the food’s flavor.
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