It would pose some dangers, of course—but it could also be fun!
If civilizations form in, or migrate to, the vicinity of black holes, what could they do for fun and profit? The following top 10 activities come to mind:
Using the black hole as a source of clean energy by dumping trash through the accretion disk of matter that swirls around it. Up to 42 percent of the rest mass of this trash can be converted to radiation at the ISCO of a maximally spinning black hole.
Coupling some engineered device to the spin of the black hole, as a giant flywheel from which spin energy can be harnessed.
Surfing with light sails on relativistic jets at speeds approaching that of light.
Prolonging youth by visiting beauty salons to near the horizon of the black hole, where time is ticking more slowly as a result of gravitational redshift.
Viewing the spectacle of the entire universe reflected and distorted as gravitationally lensed images around the black hole.
Establishing an amusement park at the so-called “photon sphere,” where one could enjoy relativistic effects for fun, such as seeing oneself from behind by looking straight ahead as light circles around the black hole.
Taking advantage of new opportunities for space travel. For example, when the Milky Way and its sister galaxy Andromeda merge billions of years from now, the two black holes at their centers will pair into a tight binary, which should act as a gravitational slingshot and eject stars or planets at up to the speed of light, as described in two papers that the author wrote with James Guillochon. Travel agencies may offer tickets to exceptional rides on ejected planets that traverse the entire universe.
Sending criminals into the black hole as the ultimate prison with a death sentence at the singularity. The mass of the black hole will determine how much time is left for the prisoners to live. The lesser their crime, the more massive the black hole would be, extending their remaining life span after crossing the “prison walls” associated with the black hole horizon.
Using gravitational waves from small objects orbiting the black hole for communication. Such signals cannot be blocked by any known form of matter.
Testing fundamental aspects of quantum gravity through organized trips for string physics experimentalists.