Tobacco companies incorporated doctors in their ads, such as this 1930 Lucky Strike campaign, to convince the public that smoking wasn't harmful. Stanford University hide caption

itoggle caption Stanford University

The Cathedral Spires in the Black Hills of South Dakota are just one of innumerable formations across the planet that speak to the Earth's ancient history. K. Scott Jackson/Ohio Water Science Center/USGS hide caption

itoggle caption K. Scott Jackson/Ohio Water Science Center/USGS

Part of the ALMA array on the Chajnantor plateau of Chile points skyward to the Milky Way, our own galaxy. The center of our galaxy is visible as a yellowish bulge crossed by dark lanes, which are themselves huge clouds of interstellar dust. José Francisco Salgado/ESO hide caption

itoggle caption José Francisco Salgado/ESO

President Abraham Lincoln's Gettysburg Address as inscribed on the stone at the Lincoln Memorial. Pat Benic/UPI/Landov hide caption

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An undated photo provided by The Patriot-News showing a bit of the 1863 editorial in which President Lincoln's Gettysburg Address was dismissed. The newspaper (then known as The Patriot & Union) referred to Lincoln's words as "silly remarks." AP hide caption

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A young girl stands in the doorway of a home in Uttar Pradesh, India. The markings on the door show that a polio immunization team vaccinated children in the home. Alyce Henson/Courtesy of Rotary International hide caption

itoggle caption Alyce Henson/Courtesy of Rotary International

Ava Gene's, a Roman-inspired restaurant in Portland, Ore., incorporates colatura, a modern descendant of ancient Roman fish sauce, into several of its dishes. Deena Prichep/NPR hide caption

itoggle caption Deena Prichep/NPR

This violin is said to have been played by bandmaster Wallace Hartley during the final moments before the sinking of the Titanic. It's thought he put the instrument in that leather case. Hartley's body and the case were found by a ship that responded to the disaster. Now the violin has been sold. Peter Muhly /AFP/Getty Images hide caption

itoggle caption Peter Muhly /AFP/Getty Images

Civil rights leader Martin Luther King waves to supporters from the steps of the Lincoln Memorial on Aug. 28, 1963, in Washington. AFP/Getty Images hide caption

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When dealing with aches and pains, sometimes the best way to get better is to feel better — and fast. Some popular medicines of old favored additives like cocaine. Courtesy of the National Library of Medicine hide caption

itoggle caption Courtesy of the National Library of Medicine