Re: A black hole in orbit: what would it be like?
You (and Hyper-Man) are thinking of the Niven short story "There is a Tide". Louis Wu finds a planet with a 'moon' that is a five feet or so diameter sphere of neutronium. Meets up with an alien race (the Trinocs) who make the mistake of getting too close. From a distance, the 'moon' produces tides just like Luna does here, but the gravitational gradient is *incredibly* steep, so don't get too close.
"Neutron Star", OTOH, is Beowulf Shafer's orbit of an actual neutron star in a GP hull packed with, among other things, a bunch of explosives courtesy of Sigmund Ausfaller.
This ends my "Niven Nerd" fact of the day
- Bill