Simplify the following text for a Grade 10 native English-speaking person.
Original: In the 1840s , using Newtonian mechanics , Urbain Le Verrier predicted the position of the then-undiscovered planet Neptune after analyzing perturbations in the orbit of Uranus .
Simplified: In the 1840s , using Newtonian mechanics , Urbain Le Verrier predicted the planet Neptune existed . He discovered this after studying the orbit of Uranus .