Nothing in the history of modem astronomy has excited as much speculation as the object, or event, known as a black hole. Black holes have provided endless imaginative fodder for science fiction writers and endless theoretical fodder for astrophysicists. They are one of the more exotic manifestations of the theory of general relativity, and their fascination lies in the way their tremendous gravity affects nearby space and time.
A black hole is very simple in structure: it has a surface — the event horizon — and a center —the singularity. Everything else is gravity. The standard model for the formation of a black hole involves the collapse of a lager star. The imaginary spherical surface surrounding the collapsed star is the event horizon —an artificial boundary in pace that marks a point of no return. Outside the event horizon, gravity is strong but finite, and it is possible for objects to break free of its pull. However, once within the event horizon, an object would need to travel faster than light to escape.
For extremely massive stars, the exclusion principle — the resistance between the macular particle within the star as they are compressed 一 will not be strong enough to offset the gravity generated by the star’s own mass. The star’s increasing density will overwhelm the exclusion principle. What follows is runaway gravitational collapse. With no internal force to stop it, the star will simply continue to collapse in on itself. Once a collapsing star has contracted through its event horizon, nothing can stop it from collapsing further until its entire mass is crushed down to a single point — a point of infinite density and zero volume-toe singularity.
The star now disappears from the perceivable universe, like a cartoon character that jumps in to a hole and pulls the hole in after him. What this process leaves behind is a deterrent kind of hole — a profound disturbance in space-time, a region where gravity is, so intense that nothing can escape from it. Any object falling within the boundary of a black hole has no choice but to move inward toward the singularity and disappear from our universe forever. Moreover, a black hole can never be plugged up or filled in with matter: the more matter that is pound into a black hole the bigger it gets.
A What would happen to objects, such as astronauts, as they vanished into a black hole? B Physicists have been amusing themselves with this question for years, and most believe that the intense gravitational forces would rip apart the astronauts long before they were crushed at the singularity. C Theoretically, any astronauts who mortgaged to survive the passage would encounter some very strange things. D For instance, they would experience acute time distortion, which would enable them to know, in a few brief seconds, the entire future of the universe.
Inside a black hole, space arid time are so warped that the distance from the event horizon to the singularity is not a distance in space in the normal sense what we can measure in kilometers. Instead, it becomes a distance in time. The time it takes to reach the singularity from the event horizon — as measured by someone falling in — is proportional to the mass of the black hole.
The only way what astronauts would know whether they had crossed the event horizon would be if tried to halt their fall and climb out again by firing their engines enough to push themselves back from the center of the hole. However, because of the time warp, if the astronauts tried to do this, they would reach the singularity faster than if they had left their engines off. Moreover, since they could get no farther once they reached the singularity, this point would mark the end of time itself.
1.The word fodder in paragraph I is closest in meaning to （ ）.
2.The opposing force between the molecular particles inside a star is called （ ）.
3.Why does the author mention a cartoon character in paragraph 4?
4.Astronaut who fell into a black hole would probably experience all of the following EXCEPT （ ）.
5.The phrase “this point” in paragraph seven refers to（ ）.
