Question

Your twin sister is hovering very near but outside the event horizon of a black hole. From a safe distance away, we see that her clock a) slowing down compared to our clock. b) speeding up compared to our clock. c) completely stopped. d) behaving normally, just like our clock. e) behaving normally, but bluer in color than our clock.

8. Your twin sister crosses the event horizon to be “inside” a black hole. Shining her flashlight back toward us, we see a) that her flashlight is very faint and redshifted b) nothing c) that her flashlight is very bright and blueshifted d) that her flashlight is completely motionless e) rapid pulses caused by the black hole’s rapid rotation

9. Black holes emit no light. Which of the following is evidence for their existence? a) We measure the radio emissions that come from inside black holes. b) Matter falling into black holes heats up and emits light at a range of wavelengths. c) The orbital period of Earth around the Sun is altered by the gravity of distant black holes. d) The mergers of two black holes produce loud booming sounds that can be heard light years away. e) The height of the ocean tides on Earth can only be explained by the gravitational effects of black holes.

Answer 1

1) due to strong gravity towards blackhole , for us the clock will slow down. As from lorentz transformation time dilated as mass increase.

Option (a)

2) due to strong gravitational field not even light can escape. Thus we see nothing.

Option (b)

3) it's true that when objects fall in blackhole they cannot escape. However when objects fall they accelerate and produces heat which emits light at different wavelength. And that's the evidence for a blackhole. Lights at different emit without a source.

Option (b)