A Brief History of Time: From the Big Bang to Black Holes by Stephen W. Hawking

Author:Stephen W. Hawking
Language: eng
Format: mobi, epub
Tags: Juvenile Nonfiction, Relativity, Astronomy - Universe, Planets, Science, Philosophy, Cosmology, General, Big bang theory, Science & Nature, Mathematical Physics, Black holes (Astronomy), Space and time, Astrophysics & Space Science, Time, Mathematics, Astronomy, Physics, Metaphysics
ISBN: 9780553346145
Publisher: Bantam Books
Published: 1990-12-14T09:00:00+00:00

CHAPTER 7

BLACK HOLES AIN’T SO BLACK

Before 1970, my research on general relativity had concentrated mainly on the question of whether or not there had been a big bang singularity. However, one evening in November that year, shortly after the birth of my daughter, Lucy, I started to think about black holes as I was getting into bed. My disability makes this rather a slow process, so I had plenty of time. At that date there was no precise definition of which points in space-time lay inside a black hole and which lay outside. I had already discussed with Roger Penrose the idea of defining a black hole as the set of events from which it was not possible to escape to a large distance, which is now the generally accepted definition. It means that the boundary of the black hole, the event horizon, is formed by the light rays that just fail to escape from the black hole, hovering forever just on the edge Figure 7:1. It is a bit like running away from the police and just managing to keep one step ahead but not being able to get clear away!

Figure 7:1

Suddenly I realized that the paths of these light rays could never approach one another. If they did they must eventually run into one another. It would be like meeting someone else running away from the police in the opposite direction – you would both be caught! (Or, in this case, fall into a black hole.) But if these light rays were swallowed up by the black hole, then they could not have been on the boundary of the black hole. So the paths of light rays in the file:///C|/WINDOWS/Desktop/blahh/Stephen Hawking - A brief history of time/f.html (1 of 8) [2/20/2001 3:15:18 AM]

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.