Spectrometer measurements during the day

The photo demonstrates how the light spectrum changes as the end of the day slowly approaches in three spectral measurements: during the noon, 45 minutes before sunset and during sunset. It can be clearly seen that blue-rich wavelengths disappear almost completely yet the red ones are abundant. The reason behind this effect is the atmospheric filtering of these blue and bluegreen wavelengths caused by Earth’s rotation away from the Sun. Have you ever thought why the Sun appears orange during dawn and sunset?