  The tidal interaction of a (rotating or nonrotating) black hole with nearby
bodies produces changes in its mass, angular momentum, and surface area.
Similarly, tidal forces acting on a Newtonian, viscous body do work on the
body, change its angular momentum, and part of the transferred gravitational
energy is dissipated into heat. The equations that describe the rate of change
of the black-hole mass, angular momentum, and surface area as a result of the
tidal interaction are compared with the equations that describe how the tidal
forces do work, torque, and produce heat in the Newtonian body. The equations
are strikingly similar, and unexpectedly, the correspondence between the
Newtonian-body and black-hole results is revealed to hold in near-quantitative
detail. The correspondence involves the combination k_2 \tau of ``Love
quantities'' that incorporate the details of the body's internal structure; k_2
is the tidal Love number, and \tau is the viscosity-produced delay between the
action of the tidal forces and the body's reaction. The combination k_2 \tau is
of order GM/c^3 for a black hole of mass M; it does not vanish, in spite of the
fact that k_2 is known to vanish individually for a nonrotating black hole.
