As the sun went down after the 1862 Battle of Shiloh during the Civil War, some soldiers noticed that their wounds were glowing a faint blue. Many men waited on the rainy, muddy Tennessee battlefield for two days that April, until medics could treat them. Once they were taken to field hospitals, the troops with glowing wounds were more likely to survive their injuries — and to get better faster. Thus the mysterious blue light was dubbed “Angel’s Glow.” In 2001, 17-year-old Civil War buff Bill Martin visited the Shiloh battlefield with his family and heard the legend of Angel’s...