Stephen Hawking: Black Holes: The BBC Reith Lectures

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1,381,55,sci,eng,20170218,20170218,4,Stephen Hawking: Black Holes: The BBC Reith Lectures
20170218-20170218, 55 pages, 4* SalesInfo o eng

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201 Stephen Hawking: Black Holes: The BBC Reith Lectures
20101 Introduction by David Shukman
60102 1: Do black holes have no hair?
260103 2: Black holes ain’t as black as they are painted
500104 About the Authors
52010401 Also by Stephen Hawking
54010402 Copyright

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Albert Einstein even wrote a paper in 1939 claiming that stars could not collapse under gravity because matter could not be compressed beyond a certain point.
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if the curves in space-time become deeper and deeper, and eventually infinite, the usual rules of space and time cease to apply.
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A black hole has a boundary, called the event horizon. This is where gravity is just strong enough to drag light back and prevent it escaping.
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There is a black hole with a mass of about four million times that of the sun at the centre of our Milky Way galaxy.
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In space, no one can hear you scream; and in a black hole, no one can see you disappear.
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Entropy means the tendency for anything that has order to become more disordered as time passes
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The uncertainty principle of quantum mechanics implies that only particles with a wavelength smaller than that of the black hole itself could form a black hole. That means the range of potential wavelengths would be limited: it could not be infinite.
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To my great surprise I found that the black hole seemed to emit particles at a steady rate.
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These calculations were the first to show that a black hole need not be a one-way street to a dead end. Not surprisingly, the emissions suggested by the theory became known as Hawking Radiation.
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Pierre-Simon Laplace, who said that if we know the state of the universe at one time, the laws of science will determine it at all future and past times. Napoleon is said to have asked Laplace how God fitted into this picture, and Laplace to have replied: ‘Sire, I have not needed that hypothesis.’ I don’t think that Laplace was claiming that God didn’t exist – just that he doesn’t intervene to break the laws of science.
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If determinism, the predictability of the universe, breaks down with black holes, it could break down in other situations.
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It is like burning an encyclopaedia. Information is not lost if you keep all the smoke and ashes, but it is difficult to read.
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My message here, then, is that black holes aren’t as black as they are painted. They are not the eternal prisons once envisaged. Things can get out of a black hole, both in this universe and possibly to another. So, if you feel you are in a black hole, don’t give up: there is a way out!
14 (51)
Professor Hawking is the author of A Brief History of Time, which was an international bestseller. His other bestselling books for the general reader include A Briefer History of Time, the essay collection Black Holes and Baby Universes and Other Essays, The Universe in a Nutshell and The Grand Design. He lives in Cambridge.

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1 being ‘spat out’ by the black hole (32)

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Stephen Hawking: Black Holes: The BBC Reith Lectures
1,381,55,sci,eng,20170218,20170218,4,Stephen Hawking: Black Holes: The BBC Reith Lectures
20170218-20170218, 55 pages, 4* SalesInfo o eng

Did I understand?

What means understanding something? What means detecting a star? What is detecting a black hole? I understand, am aware, believe that a black hole cannot be seen with my own eyes as I can see a star in the sky. What is seeing a star in the sky? Just a spot of light. What use can I have of this observation? Is it necessary to have any use of it? Oh this science! It causes more questions tha it answers.

On the level of this text, it is impossible to see the practical usefulness of science, although our everyday life is completely dependent and lying on the basis of science!

Four stars for the glimpses of hints to our experiences and the chance of reconstructing an encyclopedy out of smoke and ashes after it having been burned.


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