From the Wiki discussion on c2 about Wittgensteins Ladder:
Relativity proves that Newtonian physics was "wrong." But relativity also shows that Newtonian formulas are "remarkably close" in "most common situations."
In spite of relativity proving Newton wrong, and quantum physics proving relativity wrong, people who design roller coasters still use Newtonian formulas. Today's roller coasters don't get up very close to the speed of light, nor are they currently built close to black holes.
That would make a pretty awesome roller coaster, though!