According to the introduction, why are black holes invisible?
Read this excerpt from Why Are They Caled Black Holes?
Black holes are invisible because they have so much gravity
that nothing escapes. Not even light can escape or bounce
off. So how do scientists know that black holes exist if they
are invisible?
Scientists can not figure out why they exist.
Gravity is caused by matter.
They have so much gravity that nothing escapes.
Stars are created first.
Gravity is caused by matter, and as matter increases, the
pull of gravity increases too. Stars are born when enough
matter collects that gravity makes it collapse into a hot,
dense protostar