During the Civil War battle of Seven Pines in Virginia in 1862, Confederate troops attacked a strong Union force. At his camp some two miles away, the Confederate general Joseph Johnston tried to coordinate the attack, but he didn't know the battle had begun because he couldn't hear the fighting, even though people several miles farther away heard the battle clearly. As a result, Johnston did not send in crucial reinforcements and the battle ended in a draw. To reconstruct what happened that day, Charles Ross, a physicist at Longwood College in Virginia and a Civil War buff, looked at weather records and soldiers' diaries. He learned that a terrible thunderstorm raged the night before the battle. Winds were so strong the next morning that Union surveillance balloons were grounded. Ross says that dense forest between Johnston and the fighting absorbed the sound waves near the ground, but swift winds caught the higher sound waves and carried them far from the battle scene. Both these factors put the general in an "acoustic shadow." Johnston went to the front, unaware that the area was now under Union control, and was wounded. He was replaced by Robert E. Lee. "I don't think the Confederates would have won the battle if there hadn't been any acoustic shadows," Ross says, "but I think history definitely would have been different."