Disney always knew how to make a movie for all ages. Just remember legendary small WW car Herbie...This movie is about three youngsters in high-school which will become friends, and have a lot of troubles when they invent or better said "lend" time traveling equations from NASA. Apparently they build time traveling machine from microwave oven, projector and many other parts. As time passes they decide to use machine for helping people in school, which at first seems to go very good. But the most brightest student of all, finally understands they have created a black whole which will expand and destroy all town, and after that whole Earth. Physics in the movie is something awkward, but have in mind this is a movie just for entertainment.
All in all, this is a killer time movie worthing watching, if you have time to spare. It's funny, childish, but I do not see this as a problem, because we are all children, no matter how old we are.