Do Other Animals Cry and More Questions From Our Readers

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Are human beings the only animals that produce tears when they cry?

Paul Verges, Bowling Green, Kentucky

If you define crying as expressing emotion, such as grief or joy, then the answer is yes. Animals do create tears, but only to lubricate their eyes, says Bryan Amaral, senior curator of the Smithsonian’s National Zoo. Animals do feel emotions, too, but in nature it’s often to their advantage to mask them. Usually, if a zookeeper notices tears in an animal’s eyes, a visit from the vet may be in order to check for an infection or scratched cornea.

I’ve read that half of the U.S. states have designated square dancing as their official dance or official folk dance. Is that right? How did square dancing become so sanctioned?

Susanne Epstein, Boston, Massachusetts

Actually, more than 30 states have so honored modern square dancing. And therein lies a quintessential American tale of...lobbying. Unlike traditional square dancing, modern square dancing generally is a regulated, organized activity, often anchored in clubs; it also has many more “calls,” or maneuvers, and uses recorded, rather than live, music. Starting in 1965, modern-square-dance associations advocated for it to be designated the national folk dance. Stephanie Smith, archives director at the Smithsonian Center for Folklife and Cultural Heritage, says scholars and activists opposed that move on the ground that a pluralistic country shouldn’t elevate one dance form over others. The dance lobbyists redirected their efforts to the states and found more success there.

What is “unobtainium,” which I see sometimes in reference to the possibility of faster-than-light space travel?

Michael Barrett, Ashburn, Virginia

Ha! It’s a joke among engineers, says Margaret Weitekamp, a curator at the National Air and Space Museum’s space history department. Yes, unobtainium refers to a material that could make faster-than-light space travel possible. It’s also any substance that would solve a huge and persistent engineering problem—but does not yet exist, and probably never will. The term has been in use since at least the 1950s. It might sound familiar now because it had a role in James Cameron’s Avatar, from 2009. In that film, unobtanium (with a variant spelling) is a valuable and scarce mineral; the race to mine it leads to colonization and the film’s central conflict.

When lightning strikes a body of water, how far can the electric current travel and how long will the water stay electrically charged?

M.K. Gunn, Durango, Colorado

Scientists do not entirely understand the phenomenon, says Doug Herman, senior geographer at the National Museum of the American Indian, but the charge will travel horizontally along the water’s surface, face resistance and dissipate, usually within tens of feet. The distance will vary with the strength of the strike and the water’s temperature and salinity. (Conductivity rises with temperature and salt content.) But water does not store electricity; contrary to what some people say, you don’t have to wait an hour before heading back into a pool that was hit by lightning.

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