Thomas Jefferson owned hundreds of slaves, yet he also wrote that "all men are created equal." How did he square the contradictions between his values and his everyday life?
This 1793 grave is an early version of the kilogram. It is possible this object, now owned by the National Institute of Standards and Technology museum, was once pirate treasure.
Senate Armed Services Committee Chairman Sen. John McCain (left) and Secretary of State John Kerry both continue to serve the country in official capacities after their failed presidential bids.