Simplify the following text for a Grade 9 native English-speaking person.
Original: Feynman diagrams were originally discovered by Feynman , by trial and error , as a way to represent the contribution to the S-matrix from different classes of particle trajectories .
Simplified: The points in Feynman diagrams where the lines meet represent two or more particles that happen to be at the same point in space at the same time . The lines in a Feynman diagram represent the probability amplitude for a particle to go from one place to another .