Simplify the following text for a Grade 10 native English-speaking person.
Original: More importantly , the discovery of celestial bodies orbiting something other than the Earth dealt a blow to the then-accepted Ptolemaic world system , which held that the Earth was at the center of the universe and all other celestial bodies revolved around it .
Simplified: More importantly , the discovery of celestial bodies orbiting something other than the Earth dealt a blow to the then-accepted Ptolemaic world system . This held that the Earth was at the center of the universe and all other celestial bodies revolved around it .