In anticipation of a solar eclipse that will cross 14 states and more than 1,100 cities this summer, the U.S. Postal Service has issued a commemorative stamp that changes from total eclipse to full moon from the heat of a finger. The stamp, which will be unveiled at the University of Wyoming with NASA scientists in attendance, will be available for sale nationwide starting Tuesday. “With the release of these amazing stamps using thermochromic ink, we’ve provided an opportunity for people to experience their own personal solar eclipse every time they touch the stamps,” Jim Cochrane, the postal service’s chief...