‘I believe the lights were on,” wrote Bobby Thomson to Graig Kreindler, who was researching the Shot Heard Round the World, the storied walk-off home run that sent the New York Giants to the World Series five decades earlier. Kreindler knew that the sun was low in the sky behind first base and dimmed by dark clouds when Thomson came to bat a few minutes before 4 p.m. on October 3, 1951, at the Polo Grounds in Upper Manhattan.

Was it hard to see the ball? Or did the Giants turn the lights on, if only for the primitive TV cameras, …