James Cameron made one slight change in the 3D reissue of “Titanic,” adjusting the night sky in the scene where Rose is floating on a piece of driftwood, this to satisfy rock-star astrophysicist Neil deGrasse Tyson’s complaint that the star field shown in the original was not at all what would have been at that position in the Atlantic Ocean in 1912. Two observations: No. 1, man, I’ll bet that Neil deGrasse Tyson is loads of fun to go to the movies with. And, no. 2: As long as Cameron was tinkering with that scene, why didn’t he work a little CGI magic to make that piece of driftwood smaller so yet another generation of movie-goers won’t sit there and wonder, why doesn’t Rose just scoot her ass over and make room for Jack?