>I think a reasonable conclusion would be that some other object or device occupied the sky for a long period of time, possibly leading to the interpretion in Joshua.
A theophany or a manifestation of God's presence. He often used fire: the burning bush; the volcanic mountain; the fire by night and the cloud during the day; the star leading the Magi to the Christ child; the Angel of the Lord (which was possibly the Word of God before He became man also).
Also, God lives outside of eternity and natural constraints. He can suspend any natural law at any time regardless of us being able to figure it out.