How Does Earth’s Geomagnetic Field Work?

You asked, we answered

Kruella d’Enfer
Kruella d’Enfer

The earth’s solid iron core is hot enough to demagnetize iron and its alloys. So how does it generate the geomagnetic field?

John Campbell, Hood River, Oregon

Its core doesn’t. The geomagnetic field is generated by the liquid iron in the earth’s outer core, says Elizabeth Cottrell, geologist and curator at the National Museum of Natural History. Researchers don’t fully understand how, but believe that liquid iron is in constant motion, both from the earth’s rotation and from convection currents, and that the motion generates electrical currents, which induce the geomagnetic field.

How did we get 8½ by 11 inches as the standard size for letter paper? 

James Cloonan, Rochester, New York

Early paper sizes were limited to what a vatman—the worker who dipped a paper mold into a vat of pulp—could handle, says Helena E. Wright, curator in the division of culture and the arts at the National Museum of American History. Sizes varied within certain ranges. In the late 1600s,  papermakers invented molds that produced sheets that could be quartered into leaves of about 81⁄2 by 11, and businesses gradually adopted  variations on that size. By the 1920s—despite the efforts of a government-appointed Committee for the Simplification of Paper Sizes—most private firms were doing business on 81⁄2 by 11, and federal employees on 8 by 101⁄2. That disparity persisted until 1980, when the government adopted 81⁄2 by 11 as its standard.

How close to Sagittarius A*, the black hole at the center of the Milky Way, could a spacecraft get without getting sucked in to its doom? 

Richard B. Ellenberger, Normandy Park, Washington

Oh, about 435 light-years, assuming the spacecraft is moving at 58,000 kilometers per hour (the fastest launch velocity achieved so far from Earth). That’s according to the calculations of Laura Brenneman, astrophysicist at the Harvard-Smithsonian Center for Astrophysics. A spacecraft traveling faster could get closer.

How did women’s service in uniform during World War I help the suffrage movement afterward? 

Lee Schaffer, Bethesda, Maryland

President Woodrow Wilson was no great friend of women’s suffrage before the war, says Lisa Kathleen Graddy, deputy chair and curator in the division of political history at the National Museum of American History. But he began to change his mind after learning of the harsh treatment of imprisoned pro-vote demonstrators during the war, which included the force-feeding of suffragists on a hunger strike. The service of more than 10,000 women in the Navy and Marines—plus thousands more on the home front in factories and offices—gave Wilson a powerful argument as he lobbied for the 19th Amendment. “We have made partners of the women in this war,” he said. “Shall we admit them only to a partnership of suffering and sacrifice and toil and not to a partnership of privilege and right?”

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