The study looked at how twilight affects the distribution of particles in the atmosphere. During twilight, the sun's position causes a shift in the illuminated and shadowed parts of the atmosphere. The researchers found that the height of the twilight layer increases as the earth's shadow height increases. This means that during twilight, the light we see comes mainly from the lower, denser part of the atmosphere. As the lower layers become shadowed, the light comes from higher altitudes still lit by the sun. The researchers used a method to calculate the earth's geometrical shadow height, which helps understand how twilight impacts the vertical profiles of aerosols in the atmosphere.