Hey Veeky Forums. I have a question about black holes and special relativity.
Now, in special relativity, velocity addition becomes really fucking weird when objects approach at high speeds. For example, two spacecraft that are travelling towards each other at 99.999% (from the perspective of a third stationary observer) will be measured by the third observer to be closing distance at a rate slightly under 2c. However, from the perspective of the crew aboard one of the spaceships, the other spaceship is NOT approaching at 2c but rather .999999c. I understand this is due to a bunch of weird relativistic effects, but this isn't my main question. I want to know what happens when try to apply this rule to the curved spacetimes of general relativity, or if this is even a valid question to ask.
For example, rotating black holes possess a region extending from the event horizon called the ergosphere, where spacetime is "dragged" in the direction of the black holes spin. The environment is so extreme that it is impossible for any particle, even light, to stand still in this region. Now, from the perspective of a stationary outside observer, the matter swirling around in the ergosphere is travelling faster than the speed of light from their vantage point. This seems to contradict special relativity's claim that you can never observe an object as travelling faster than the speed of light, although I understand that curved spacetimes fall under general relativity's realm. Now for my questions, I'll post more later but these are some of the ones that have been bugging me the most.