Which observation challenged Ptolemy's geocentric model of the universe prior to the Scientific Revolution?

💡 Explanation

Mars' retrograde motion challenged Ptolemy's model because it required complex epicycles to explain the apparent backward movement against background stars. Therefore retrograde motion became problematic, rather than stellar parallax, starlight aberration, or supernovae brightness variations which were not observable without more advanced technology.

• Which mechanism limited cutting tool effectiveness despite widespread bronze axe blade use by Mesopotamians?
• Which diffusion-based mechanism enabled ancient bloomery furnaces to produce wrought iron from iron ore?
• Which metallurgical change improved iron weapons over bronze ones in the late Bronze Age?
• Which structural effect accompanied the transition from mortise-and-tenon joints to copper sheathing in 18th-century ship construction?
• What outcome occurs from repeated use of ballista siege engines in ancient Roman warfare?
• Which consequence occurred when 18th-century ships' hulls experienced prolonged immersion in warm, tropical waters?