Maybe change a little of the first sentence but the rest looks good
Answer:
The word "protracted" means lasting longer than expected, or unusually long, so what protracted most clearly means based on the context of the excerpt is how the time period of celestial motion studies must have lasted unusually long.
Answer:
Look below.
Explanation:
You didnt provide the second sentence but from my understanding the prefix "un" , which means not, could be added to friendly to mean unfriendly or not friendly.