In 1975, France launched an artificial Earth satellite made from uranium-238. Its mass is 47 kg, radius is 25 cm. The surface is covered with corner reflectors and ensures the accuracy of light location from ground objects up to 2 cm. The use of a high density material allows minimizing the resistance forces of the earth’s atmosphere.
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.