Simplify the following text for a Grade 11 native English-speaking person.
Original: More accurately , it is the intersection of a spherical surface , the celestial sphere , with the ecliptic plane , which is the geometric plane containing the mean orbit of the Earth around the Sun .
Simplified: In more accurate terms , it is the intersection of the celestial sphere with the ecliptic plane , which is the geometric plane containing the mean orbit of the Earth around the Sun .