Why is the evening sky so blue?

When the weather is clear, there will be many tiny dust, water droplets, ice crystals and other substances in the air. When sunlight passes through the air, long-wavelength red light, orange light and yellow light can penetrate the atmosphere and directly hit the ground, while a small part of short-wavelength blue, purple, indigo and other colors will be blocked by particles suspended in the air, making the light scatter in all directions, and the sky appears blue. If you tell the truth, it means that there are more particles in the sky at night. Personally, I feel that there are more water particles in the air and the sky is bluer after the rain.