Why do moths fly toward light?

One theory is that many night-flying moths find their way by using the moon as a guide. By flying at a constant angle to the moon-say with the moon always on their left-they keep going in the same direction. To a moth, a bright light such as a lamp resembles a super-moon. Keeping at the angle to the lamp makes the moth circle around it and eventually spiral into it. If the light is in a building, moths flutter at the window trying to reach the substitute moon.