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.
Vertebral compression Fractures of the spine (vertebra) can cause severe ”band-like” pain that radia
Accretion Disk Around a Supermassive Black Hole
Black and White Out-Migration from Virginia and North and South Carolina, 1870–1940 (in thousands)
The Making of Black Harlem
Material safety data sheets (MSDS), now called safety data sheets (SDS), should be readily available ...
A thin cleft, called the synapse, separates one cell from another.