Simplify the following text for a Grade 14 native English-speaking person.
Original: According to the prevailing theory , a slight imbalance of matter over antimatter was present in the universe 's creation , or developed very shortly thereafter , possibly due to the CP violation that has been observed by particle physicists .
Simplified: According to the prevailing theory , a slight imbalance of matter over antimatter was present in the universe 's creation , or developed very shortly thereafter .