Why did the ancient astronomers not know about the existence of huge planets – Uranus and Neptune, although the smaller planets – Mercury and Mars – were well known to them?
They are located at a very large distance from the Earth and are practically invisible to the naked eye.
The astronomers of antiquity did not know about the existence of Uranus and Neptune, because although Uranus and Neptune and huge planets, they are located at a very great distance from the Earth, and they simply cannot be seen with the naked eye, and the telescope was invented only in 1611.
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.