Certain things are invisible to us because our eyes just can't sense them. You don't see beams of infrared light shooting across the room from your remote control to the TV, for example, or radio waves streaming off everyone's cell phone.
Then there's the invisibility caused by a black hole. No matter how hard you look, you can't see the black hole itself. There's nothing at all coming from it – no light, no other forms of energy; and no matter. We can detect only what's around it – never anything inside.
—A Black Hole Is NOT a Hole,
Carolyn Cinami DeCristofano
a. What conclusion can be drawn about why black holes are invisible?
b. Special telescopes are needed to view black holes.
c. Blacks holes blend into the blackness of space, so we cannot see them.
d. The radio energy that black holes emit is not visible to our eyes.