Blood sky over million metropolis. Is it an omen? Is the end of the world imminent? Or is it a natural phenomenon? This suddenly red sky over the Chinese city of Fuzhou causes great confusion among passers-by. “The sky is turning red,” a woman is heard saying. And a man is troubled: “Why is the sky red? Scary. The end of the world. Run, run!” But ultimately there is no reason to panic. Meteorologists can quickly calm down: The red light is caused by light refraction near the port. Favored by the cloudy and foggy weather, the finest particles suspended in the air, so-called aerosols, are said to have refracted and scattered the light from fishing boats and thus created the red sky. And the weather conditions for the phenomenon appear to be favorable: days before, the same bloody skies appear over the city of Zhoushan, almost 700 km away. Scientists call this type of reflection “Rayleigh scattering”. This effect is also responsible, for example, for the blue of the sky during the day and the redness of the evening.