Wasn't it Chris.B who wrote:
Wouldn't multiple dimensions require some rather strict
cross-dimensional physical placement? The leakage from even a small
black hole popping up on the dining table is apt to spoil ones
appetite. Surely any cross-dimensional gravitational effects should be
detectable?

It depends how close the next universe is. If the nearest brane that
contains matter happens to be the equivalent of a few tens of thousand
light years away, then the gravity that leaks into our universe would be
smeared out as if it were coming from diffuse invisible sources the size
of a galaxy.

--
Mike Williams
Gentleman of Leisure