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.
Animals of Hindustan monkeys called bandar that can be taught to do tricks
Gallery of Xylosandrus crassiusculus split open, with pupae and black fungus
Leaf from a Black Walnut tree
Trapping of Light by a Black Hole
A recruiting poster for the “True Sons of Freedom” encouraged African Americans to enlist. In fact,
Rubella rash in a young child. Rubella is also called 3-day measles or German measles.