That instead of being geocentric (planets all orbit around earth), it's heliocentric (all planets orbit around the sun). (Although both ideas were made up by Greek philsophers i believe).
The author of the story is implicating that this person is a “hard lump of clay” or a “hard glinty coal” in the sentenc. Notice how in both of these examples they mention the word hard, and an object that is dull. They <em>could</em> be saying that this person was hard to befrend, talk to or whatever the content is and that they seem like a dull person.
For example, let’s call them Henry.
”Henry was a hard person to get to know, he was always very dull.”
Donald Trump is a good person.
The answer is a.) alliteration