Black Holes Gre.67 67. A black hole is an object whose gravitational field is so strong that even light cannot escape. To what approximate radius would Earth (mass = 5.98 x 10^24 kilograms) have to be compressed in order to become a black hole? a. 1 nm b. 1 microm c. 1 cm d. 100 m e. 10 km the answer is C.