Why Are Chickens So Bad at Flying? And More Questions From Our Readers

Why do chickens have wings if they can’t use them to fly? Caroline Mueller Loane | Hoboken, New Jersey

Chickens actually can fly! Just not very well. The modern chicken evolved from wild junglefowl. Junglefowl were already adapted to living on the ground, and when humans bred chickens for meat, they prized the heaviest birds. So modern domesticated chickens are large and heavy, with wings too small and inadequate for long-distance flight. The best flyers can stay aloft for less than 50 feet. Some of the larger breeds can do little more than jump. —Sara Hallager, curator of birds, National Zoo and Conservation Biology Institute

Why does the United States have 25-cent coins but not $25 bills? Michael P. Shore | Dayton, Nevada

Many currencies around the world have denominations of 20, so the question is why the U.S. has 25-cent coins at all. During the colonial period, coins from Britain, Germany and other nations were in circulation, but Spanish coins were especially important to the early American economy. Around the time of U.S. independence, one-eighth of a Spanish real equaled about 12.5 cents, so quarters may have developed to line up with that currency. (One quarter equaled “two bits.”) Banks and private businesses produced paper money in a wide variety of denominations until the outbreak of the American Civil War, when the federal government began issuing paper money in denominations of $5, $10 and $20. —Ellen Feingold, curator of the National Numismatic Collection, National Museum of American History

Which U.S. presidents had enslaved domestic servants at the White House? Edwin L. Crammer | Boynton Beach, Florida

At least 12 U.S. presidents enslaved African Americans, seven while living at the White House (Thomas Jefferson, James Madison, James Monroe, Andrew Jackson, John Tyler, James Polk and Zachary Taylor). Erica Armstrong Dunbar’s 2017 book Never Caught tells the story of Ona Judge, an enslaved maid brought from Mount Vernon to the President’s House in Philadelphia to serve George Washington. After she escaped, the first president pursued her, as documented in personal correspondence, newspaper accounts and runaway advertisements. In 1865, Paul Jennings published his own story of being enslaved by a president: A Colored Man’s Reminiscences of James Madison. It’s important to acknowledge the humanity of these individuals by remembering their names. —Mary N. Elliott, museum specialist, National Museum of African American History and Culture

Is there a reason wind turbines are shaped like giant airplane propellers? Jamie Trescott | Marianna, Florida

The two types of blades use some of the same physics and aerodynamics, so they look similar. But there are big differences. Aircraft propellers use a motor to move air: They must rotate quickly to generate thrust. Wind turbine rotors are moved by air: They turn at much slower speeds so they can spin electrical generators while extracting the most energy from the wind. So while similar in some ways, propellers and rotors require different engineering designs. —Harold Wallace, curator of electricity collections, National Museum of American History