A sunset occurs when sunlight travels through more of the earth's atmosphere. This process causes molecules to disperse blue and violet wavelengths from the light. The remaining light that reaches observers ranges from red to orange.
Sunsets can differ significantly depending on the location from where a person is watching. Cities with high pollution screen out more light than normal, therefore, they produce sunsets with more reds and yellows. Volcanic eruptions cause vibrant sunsets. Adversely, areas where the air is clean produce little or no sunsets. This effect is especially noticeable in the Arctic, where the sky remains blue and the sun is orange.