The air contains a large amount of dust, which comes from dry plants, volcanoes, desert dust, and soot ashes brought about by human life and production.
Dust is very annoying, it causes air pollution to humans, stains our clothes, food, and also affects the manufacture of highly accurate industrial products, such as semiconductor chips, laser disks, etc. For this reason, industry has to eliminate it with purification equipment.
For the living environment in which we live, it is of course very beautiful to have no dust. But without dust, the world would be a different story. Because of the dust in the upper air, the sun we see in the evening is fiery red; because the particles of dust in the air reflect the sun's rays, the sun is still visible an hour or two after sunset, which is the beauty of the sunset.
The biggest function of dust is that the water vapor in the air takes it as the core and gathers into water droplets, forming raindrops that land on the ground. If there was no dust, it wouldn't rain very often on Earth.