When two tones at slightly different frequencies are played separately and heard through stereo headphones or speakers, the brain perceives a third sound: a binaural beat. Though discovered by German scientist Heinrich Wilhelm Dove in 1839, the phenomenon was largely ignored until the 1970s. The beats are now a source of interest for some who think they have the potential to induce relaxation and increase memory and learning ability. How are binaural beats related to the "cocktail party effect"?
W. Somerset Maugham
Back in the day
With a summit elevation of 20,320 ft (6,194 m), Alaska's Mt. McKinley is the tallest mountain in North America. James Wickersham led the first recorded climbing attempt in 1903 but turned back at 8,000 ft (2,438 m). In 1910, a group known as the Sourdough expedition claimed to have summited its lower, northern peak. Three years later, explorer Hudson Stuck and three others made the first successful ascent of the South Summit—its true summit. How did Stuck's ascent verify the Sourdough climb?
Born on a day like today
Morley was an American archaeologist who studied pre-Columbian Maya civilization throughout Central America, including at Copán, Honduras, Petén, Guatemala, and Chichén Itzá, Mexico. Though his archaeological work was widely recognized during his lifetime, it was only after his death that his other career was revealed—Morley worked as a spy for the US during World War I by searching for German submarine bases in Central America. His adventurous life may have inspired what famous film character?