Stephen Hawking

This fellow may be the most interesting man on earth. His story is one we should all read. He wrote a book called "A Brief History of Time" which sold hundreds of thousands of copies and there aren't 20 people in the U.S. who read it and even fewer who could understand it. I didn't buy that book, but I did pick up a paperback of his a few years ago called 'Blackholes and Baby Universes" which I promptly skimmed and set aside. I set it aside so well, I just found it again today and started again to try to see what it was he contributed to science. Well, I rediscovered just how stupid I am and how impossible it is for me to comprehend such things as black holes. It is not Stephen Hawking's fault. He writes quite well. Here, is an example of his writing in which he is explaining how a black hole might be created.
"Imagine a star with a mass ten times that of the sun (I can't even do that). During most of its lifetime of about a billion years (say what?), the star will generate heat at its center by converting oxygen into helium. The energy released will create sufficient pressure to support the star against its own gravity, giving rise to an object with a radius about 5-times the radius of the sun (now he has really lost me). The escape velocity from the surface of such a star would be about a thousand kilometers per second (can't comprehend that). That is to say, an object fired vertically upward from the surface of the star with a velocity of less than a thousand kilometers per second would be dragged back by the gravitational field of the star and would return to the surface, whereas an object with a velocity greater than that would escape to infinity ( I have already confessed in a previous blog about my problem with infinity, but how does Hawking know that is where that object is going?)
When the star had exhausted its nuclear fuel, there would be nothing to maintain the outward pressure, and the star would begin to collapse because of its own gravity. As the star shrank, the gravitational field at the surface would become stronger and the escape velocity ould increase. By the time the radius got down to thirty kilometers (can you imagine the math necessary to get him to that measurement?) , the escape velocity would have increased to 300,000 kilometers/second, the velocity of light. After that time any light emitted would be dragged back by the gravitational field. According to the special theory of relativity, nothing can travel faster than light, so that if light cannot escape, nothing else can either. "

So there you have it. A black hole: a region of space-time from which it is not possible to escape to infinity. Next time you see Hawking's book on someone's coffee table, that is what it says.