QUESTION : Since Pluto's and Neptune's orbits cross
 over eachother, could they ever  collide some day?
 
ANSWER from Heidi Hammel  on april 24, 1996 : 
 
 Neptune and Pluto could never collide.  A scientist in Texas, Renu
 Malhotra, has studied their orbits very carefully, and she has found that
 they are in a special configuration called a "resonance."  This means that
 although their pathes do indeed cross, the two planets themselves will
 never be together at the same place in their orbits at the same time
 (which is what it would take for them to collide).  So Pluto and Neptune
 are both safe from one another.
 DONE