05-18Museum at Prairiefire, Overland Park, Kansas - Bernard P. Friel/Universal Images Group via Getty Images)
05-17Salt ponds of Maras in Peru's Sacred Valley of the Incas - Fotofeeling/Westend61 on Offset/Shutterstock)
05-16Burrowing owl chicks gaze out from among flowers near the Pawnee National Grassland in Colorado - Roberta Olenick/Alamy)
05-15Panoramic view of the Bernina Range with blood moon, Eastern Alps, Engadin, Switzerland - Bernd Zoller/Shutterstock)
05-12Nurses serving with the American Red Cross in Paris, France, in May 1919 - Universal History Archive/Universal Images Group via Getty Images)