Strontium atoms floating in the center of this photo are the heart of the world's most precise clock. The clock is so exact that it can detect tiny shifts in the flow of time itself. Courtesy of the Ye group and Brad Baxley/JILA hide caption

itoggle caption Courtesy of the Ye group and Brad Baxley/JILA

The Concorde was fast and changed how we thought about travel here on Earth. In the future, we may well travel at speeds that change our relationship with time itself. David Parker/Getty Images hide caption

itoggle caption David Parker/Getty Images

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