One day, while straying dangerously close to a black hole, an astronaut notices that no matter how hard he tries to remain at rest, he is inevitably drawn into the black hole unless he keeps moving. What does this tell an observer about the black hole?
A) The black hole is evaporating.
B) The black hole is supermassive.
C) The black hole is electrically charged.
D) The black hole is rotating.

Question

Quizplus · Accepted Answer

The astronaut's experience suggests the presence of frame-dragging, a phenomenon associated with rotating black holes, as described by the Kerr metric in general relativity. This effect causes spacetime to be dragged around the black hole, making it impossible for objects to remain stationary relative to a distant observer without moving against this drag.

One Day, While Straying Dangerously Close to a Black Hole