I thought it was a simple question
Science teacher at college wants to demonstrate the theory of black holes in the fabric of time and space with the following:
1 dustbin
1 bedsheet
1 decent sized stone
4 luckless individuals

Teacher places dustbin upright. Gets unlucky 4 to hold sheet (fabric of space and time) over the bin. Places stone (very heavy planet) in the middle of the sheet and over the bin. Gets unlucky 4 to walk towards the bin and orders the class to observe the planet falling through fabric of time and space leaving a black hole in its place. Simple. Theory demonstrated.

I asked, “What’s pulling the planet in a downward direction?”
Science teacher looks at TitanLX and slowly shakes head as poor dim-witted TitanLX just doesn’t get the whole thing.

My conclusion is that the whole ‘fabric of time and space’ is utter twaddle and I won’t be swayed otherwise.
(TitanLX, Thu 13 Oct 2011, 16:00, 4 replies)

The earth's gravity is acting on the 2D sheet in an analogous way that the "planet"s *own* gravity would act on 3D space
...obviously
(moon monkey is busy making memories worth repressing, Thu 13 Oct 2011, 17:03, closed)

black holes come from the collapsing of massive stars
do they not?
( Vipros. clever got me this far, then tricky got me in, Thu 13 Oct 2011, 18:54, closed)

maybe

(spleenspleenspleen coffeeflavouredsugarcoatednicotine, Thu 13 Oct 2011, 19:16, closed)

xkcd got there first...
xkcd.com/895/
(flimflam_machine, Thu 13 Oct 2011, 21:40, closed)