> If you picture us in an X-Y plane (which somehow represents all 3 spatial coords), and "up" is the time dimension, then a black hole would be the X-Y plane de

> If you picture us in an X-Y plane (which somehow represents all 3 spatial coords), and "up" is the time dimension, then a black hole would be the X-Y plane deformed into a 90-deg "pipe" facing straight down. This is not correct, there is no 90 degree bend. Space-time is locally Minkowskian ("flat") at the event horizon. It looks like a sharp 90 degrees turn in some coordinate system, just as when you walk in a "straight line" (a great circle if you prefer) over the north pole you go discontinuously from "walking north" to "walking south" even though your real motion is continuous.