Lucas had always been fascinated by astronomy. Every night, he would take his telescope outside and gaze at the stars. He learned about constellations, planets, and the mysteries of the universe. Last week, he attended a lecture on black holes, which deepened his understanding of space. During the lecture, the speaker described black holes as regions in space where the gravitational pull is so strong that nothing, not even light, can escape. Given this description, it can be concluded that black holes are extremely ______.