Why do artificial satellites of the Earth, sweeping across the sky, when viewed from the Earth seem to flicker, change in brightness?

The satellites of the Earth are visible due to the fact that they reflect the incident sunlight. Rotating in flight, they turn different areas of their surface towards us, reflecting more light, sometimes less.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.