Answer to Question 1
The escape velocity of a celestial object is the speed that an object on its surface needs to escape the gravitational field. A black hole is so dense that the escape velocity is greater than the speed of light, so light cannot escape the black hole; hence, the term black.
Answer to Question 2
It became known as the Copernican Revolution because it was not just the adoption of a new idea but a total change in the way astronomers, and, in fact, all of humanity, thought about Earth and its place in the Universe. In fact, our modern use of the words revolution and revolutionary to describe philosophical, political, and social upheavals comes from the title of Copernicus's book, De Revolutionibus, which means On Revolutions.
The black-capped chickadee is a permanent resident in biomes with harsh winter conditions.
Black-tailed Jackrabbit camouflage
Jets Created by a Black Hole in a Binary System
Exterior View of Tholos, The So-called Treasury of Atreus
Black-Scholes Formula
Black-tailed Prairie Dog (Cynomys ludovicianus).