- #1
wangyi
- 56
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Hi, I have a question on can the black hole be formed?
As we know,
First, in the Swartzchild solution of GR, an observer outside the black hole will find it takes infinity time for any object to fall into the black hole.
Second, a black hole is formed by a star falling to its center.
Now the question arises: when a star is falling, and nearly to form a black hole, say, if one little piece of matter falls onto the star, it forms a black hole. At this time, the time for a observer to see the last matter falling onto the star is nearly infinate, that means no matter how long a period of time T given, we will find a piece of matter small enough which falls onto the star taking longer time than T according to the observer outside. Then how can a black hole form?
I have been confused about it for long. Thank you.
As we know,
First, in the Swartzchild solution of GR, an observer outside the black hole will find it takes infinity time for any object to fall into the black hole.
Second, a black hole is formed by a star falling to its center.
Now the question arises: when a star is falling, and nearly to form a black hole, say, if one little piece of matter falls onto the star, it forms a black hole. At this time, the time for a observer to see the last matter falling onto the star is nearly infinate, that means no matter how long a period of time T given, we will find a piece of matter small enough which falls onto the star taking longer time than T according to the observer outside. Then how can a black hole form?
I have been confused about it for long. Thank you.