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Post by raygallagher on Oct 20, 2006 11:50:39 GMT
Chris Lyntott's excellent lecture on the 18th has left me with a few questions, which is how it should be.
We are in an expanding universe and the expansion is at a constant, non accelerating, rate; the flat geometry. This expansion means that the more distant an object the greater its velocity away from us and at great distances the velocity of a receeding object can be greater than the speed of light. The distance to the point were the object exceeds the speed of light is the size of our observable universe.
The observable universe is 13.7 billion light years in radius. Why can we deduce from this that the universe is 13.7 billion years old?
Can anyone recomend any good books or websites on cosmology that can answer questions like this?
We should be making a lot more use of this forum. I'm sure there is a lot of expertese in the IAA and that no-one minds helping the like minded.
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Post by Administrator on Oct 20, 2006 14:52:04 GMT
Hi Ray, Welcome to the board, thanks for posting, I agree with your comments about members making use of the board! I don't claim to be in any way knowledgeable in this area but as I understand it, the expansion of space itself is not limited by the speed of light, so that objects further than 13.7 billion light years away would be receding faster than the speed of light, which is why we can never 'see' them. This web page says that the universe is more likely to be 156 billion light years wide! Which is lucky since I was beginning to get claustrophobic. www.space.com/scienceastronomy/mystery_monday_040524.html
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Post by pk on Oct 27, 2006 11:30:43 GMT
Hi Ray I'm a complete newcomer to astronomy but I can recommend a book by Brian Greene; 'The Fabric of the Cosmos'. I'm reading it at the moment and I think it manages to explain complex (and in some cases downright weird) ideas in a reasonably straightforward way. However, I still find myself having to put it down, screw my eyes up and squeeze my brain to get a grasp of some parts! (Who was it that said " the universe is not only peculiar, but more peculiar than we can imagine."?) Another one I've seen is 'The Road to Reality' by Roger Penrose but it appears to be pretty technical, and involves quite a lot of mathematics. All the best, Patrick.
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Post by dobsonian on Oct 30, 2006 20:18:17 GMT
Hello, I too have read this book, and I have to say that I found it heavy going. I read the book from cover to cover, then left it for a week or two, then re read it. Still did not fully grasp all the ideas. I think that amateur astronomy and Cosmology are strange bedfellows, as one deals in practicalities whereas the other in merely abstract ideas. Regards, John.
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Post by raygallagher on Nov 15, 2006 15:16:25 GMT
I have the 'road to reality' but as you say its a bit heavy. I must go back to it, thanks.
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