Featured Article Quiz #191
Black hole
#1 What is the event horizon of a black hole?
A boundary beyond which light and other matter cannot escape due to extremely strong gravity
The point where a black hole stops growing because it has no way to absorb matter
The location of the central singularity where spacetime curvature becomes infinite
#2 According to the text, who first widely accepted an early example of a black hole?
Cygnus X-1
Sagittarius A*
The Sun
#3 In the late 1700s, what did John Michell suggest about extremely massive stars?
Their gravity could make the escape speed greater than the speed of light, so light would not escape
They would always explode before reaching any critical radius
They would become visible only if they were exactly the same size as Earth