Question

problem 35 (2% of assignment value)
a friend of yours who is a science fiction fan hears you talk about the fact that astronomers now believe that the mechanism for the large energy output of quasars involves a supermassive black hole. he challenges you, saying something like, “oh come on, every science fiction fan knows that nothing, not even light, can escape from a black hole! how can a black hole be an energy source?” how would you respond to his objection?
please select the best choice from the available options.
○ youre right, my explanation doesnt make sense; i wonder why astronomers didnt think of that?
○ light cant escape from the event horizon of a regular black hole, but it can easily escape from the event horizon of a supermassive black hole
○ it isnt light that escapes from the black holes in quasars, but x-rays and gamma-rays, which work by completely different rules
○ the energy we see from quasars comes from regions where matter is falling in; these regions are still outside the event horizon
○ quasars act like gravitational lenses and bend spacetime until light and other radiation can emerge from a black hole in unexpected ways

Explanation:

To address the friend's objection, we analyze the options:

• The first option is incorrect as light can't escape a regular black hole's event horizon, and supermassive black holes in quasars also have event horizons where light can't escape.
• The second option is wrong because the physics of light and radiation (like x - rays, gamma - rays) doesn't change for quasars' black holes; light still can't escape the event horizon.
• The fourth option is incorrect as black holes, including those in quasars, follow the law that nothing (including light) escapes the event horizon.
• The third option is correct: Quasars' energy comes from matter falling into the black hole's accretion disk (outside the event horizon). As matter falls in, it heats up and emits energy (like x - rays, gamma - rays) before crossing the event horizon, so this energy isn't escaping from inside the black hole (where the event horizon is), but from the region outside where matter is falling in.

Answer:

the energy we see from quasars comes from regions where matter is falling in, these regions are still outside the event horizon