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.
Lampreys (sometimes also called lamprey eels) are a family of jawless fish
Once you go black, you never go back!
black-eyed susan (2)
The Land Ordinance of 1785 called for surveying and dividing the Western Territories into square mil
A resonance tube, called a Helmholtz resonator, is used on the intake duct between the air filter ...
Black Hole and Companion Star