expanding universe

The non amateur stuff. Hawking, black holes, that sort of thing

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joe
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Post by joe »

Hi Cliff,

Teach Yourself Cosmology is a very good book to introduce the reader to the main topics of cosmology. Short and concise. One that I would recommend if you are interested and feel the need to part with £30 is The Foundations of Modern Cosmology by John F. Hawley and Katherine A. Holcomb published by Oxford Uni Press. This goes into more detail but explains everything in a very clear manner, has a little of the simplest maths and also an excellent website to accompany the book and topics. It also happens to be the book used for one of the cosmology distance learning courses.

http://astsun.astro.virginia.edu/~jh8h/Foundations

Best wishes,
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Cliff
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Post by Cliff »

Dear Joe
Thanks for the gen about the cosmology book you recommend.
at the moment I am trying to keep a down the new books I acquire.
I do have quite a lot of books already and even I have to admit my wife is right in saying I have too many books already. Even so I still get the odd new book from time to time, too many times! However, I mostly lean towards getting new "practical" astronomy books, rather than about cosmological matters. with regards to cosmology I try to keep updated as best I can reading "New Scientist" and the likes. Indeed I just got The March "Scientific American" today. Apart from an interesting article about Global Warming, which I have some concerns about. There is a very interesting article "Misconceptions about the Big Bang" by C.H. Lineweaver & T. M. Davies. I need to read the article again more thoroughly but if my initial quick glance through is right the article suggests "If space were not expanding,the most distant object we could see would now be about 14 billion Light years away. ... the Universe is expanding .... the current most distant object we can see is about three times farther, or 46 billion LY..."
But the article then raises more complications because of the fairly recent discovery of the accelerating expansion.
........." The current distance to our cosmic event horizon is 16 Billion LY......."
I must say I found the article at a quick read very interesting. As to whether I will understand the article any better after reading it more thoroughly is very debatable.
Best wishes from as usual the grumpy old codger Cliff.
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Post by joe »

Know the feeling regards books, Cliff. I recently had to value my telescopes and eyepieces for insurance purposes and was taken aback by the amount. THEN I considered how much I had spent on astronomy books......!!! :shock:
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jax
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fascinating..

Post by jax »

totally fascinating this thread..!!

i am currently revising for my Open University course on "Space, time and Cosmology"

..guess what i'm doing right now.. expansion of the universe, scale factors, dark matter..and on and on.. it's wonderful..my head hurts.. so i came to browse here for a break!!

but i must admit, having started out with the OU with not even an O-level in math to my name, not a telescope nor pair of binoculars.. nor.. more than a casual interest in things astronomical..

..i am now totally hooked.. if i pass this year's exam (Oct 10th)..i will have my degree ..which i never set out to get anyway.. but far more than that.. i have gained a whole new love and appreciation of the 'stuff out there'...

.. right now my brain fairly aches with the revising..(i'm not as young as i used to be..) but it wont be long and after October i shall lurk here far more...

greetings to you all..

jax

ps have just bought my first ever scope..which i am not allowed to play with 'til you know when..
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Post by Geoff Burt »

Dear All.

You might have seen on the BBC on-line news today that two galaxies have been observed colliding, see

http://news.bbc.co.uk/1/hi/sci/tech/4189278.stm

furthermore, our own Milky Way is expected to eventually collide with the Andromeda galaxy. Thinking about the often quoted balloon analogy to explain the expansion of space following the Big Bang, this leads me to admit that I can't understand how galaxies can ever collide if they are all flying away from each other. Does this mean that space is expanding in different directions and perhaps even at different velocities ?

Best Wishes,

Geoff Burt :?
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Post by KendalAstronomer »

I think the balloon analogy refers to the frame of reference within which the galaxies independant movements happen. The moving apart, Hubble Flow, is the net movement rather than the movement experienced by each individual galaxy. Within this net movement, there is standard statistical turbulance leading to colliding galaxies etc.
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Post by joe »

Yes, if a galaxy or group of galaxies is close enough to others then it will be affected by gravitational forces and may be pulled towards another to eventually collide. The vast expanses of space between clusters of galaxies is more or less empty and the clusters are too far apart for gravity to play a role and therefore the general expansion of space is dominant. Most of the universe is this empty space between clusters. The Solar System is not expanding because gravity is dominant here.

I also think the Milky Way is at this very moment colliding with the Sagittarius Dwarf Galaxy and perhaps did some damage a while back to the Magellanic Clouds.
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Post by Cliff »

Dear Jax
I only just saw your recent mail.
Great stuff. Very best of luck with your forthcoming OU exams.
I was always scared stiff of doing exams. So I have to admit to being a bit envious of people who do well academically.
Very best of luck from the Grumpy Old Codger Cliff. I hope the !0th Oct goes well for you.
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Post by Cliff »

Dear Joe
I am interested to see your further comments.
I must admit that although I do generally go along with the Big Bang, I am feeling increasingly uneasy about some things related to it.
Groups of galaxies gravitationally pulling each other together ( eg our local group), outer most gallaxies accelerating apart. Walls of galaxies, String Theory, Branes, Dark Matter, Dark Energy. I doubt if I will ever get my head anywhere near these things never mind grasp them to an worthwhile acceptable level.
I read about the things in various books and magazines but in the end my acceptance of theories largely comes down to trust, and sometimes I feel unsure who to trust.
I tend towards being an aetheist (perhaps I am an agnostic) but sometimes think for someone like me belief in God might be just as good an answer (may be even better?) as trying to resolve the Universe in scientific terms.
I also sometimes think that I am just too lazy to go to church on sundays and that might be one reason I am a non believer.
Best wishes from the Grumpy old Codger Cliff
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Post by joe »

I know the feeling Cliff. There is an awful lot that we have to accept on faith alone where science or theoretical physics is concerned as we have no way of checking the facts or doing the experiments ourselves. But there is one experiment that we can conduct to test a theory of the universe. Just by opening our eyes to the night sky we can see that the universe had to have a beginning at least, as the sky is not yet ablaze with starlight from every point. So cosmologists have got one thing right. :D
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Post by Cliff »

Dear Joe
I hope that cosmologists have got quite a few things right.
Being a bit nasty about it, one could say quite a lot of taxpayers money has been spent on cosmology over the years. Of course I am all for it, but not everyone might think cosmology gives value for money.
Dare I say it but I sometimes do wonder if cosmologists are trying to move too quickly ? Perhaps they should sit back a bit and ponder.
My wife says I do it all the time! So perhaps not?
I presume that your reference to blazing stars everywhere is effectively related to the good old Olbers Paradox. I have read that the famous paradox was thought about quite a while before Olbers cottoned on to it.
I cannot help thinking that there may be a while to go before all the connotations related to Olbers Paradox are really adequately explained.
With regards to the beginning of the Universe. I personally keep an open mind about it. As I said before, I tend to go along with the Big Bang theory. But I think there are several variants and I would hate to chose between them. I even go as far as thinking the Universe, or something akin to what we think of as the Universe could equally last forever and always did in the past. I think that some theorists suggest that the Universe was once only the size of a grapefruit ? I have never felt sure whether they think of the Univers was originally the size of a Universe or that it could have been even smaller before, presumably when "ordinary" physics and chemistry rules did not apply (or was different).
So one could argue that a "god" started all equally well as the Universe started out of nothing, or that the Universe always existed?
I might even be happy to accept there is a god. However, I think it does not matter whether there is a god or not because I do not think that god (if one does Exist) could care two monkeys uncles what happns to me (or anyone else).
Having said that, I sometimes wonder when the day of reckonning arrives, will I still stick to those gut feelings................
I am starting to feel cowardly already, Best wishes from the Grumpy Old Codger Cliff
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Post by davep »

Cliff wrote:So one could argue that a "god" started all equally well as the Universe started out of nothing, or that the Universe always existed?
Probably not equally. We have some evidence of a Universe existing. Working with the idea of a moment of "creation" I'd have thought that the question of why it happened was orthogonal to how (if at all) it happened.
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Post by joe »

davep wrote:orthogonal to
8) Good one. Had to get the dictionary out.
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Post by joe »

Cliff wrote:one could argue that a "god" started all equally well
...or a teapot.

I can see that you are kind of happy with the Big Bang Cliff so this is not necessarily directed at you. Do we accept that the universe is expanding or not? If it is expanding then it was smaller in the past. There are stars that are 12 billion years old (do we accept this also, these points are no longer controversial I believe) so it has been expanding for at least that amount of time. 12 Billion years ago the universe would have been much "smaller".

As for a God starting it all, I am prepared to be convinced but I see no evidence of it and to be honest, don't expect to. I think theological arguments are perhaps better conducted elsewhere but there are good sound physical and astrophysical arguments to be used when discussing a creator god. The big problem I always find is that believers never seem to state what their God is all about in any kind of detail. For obvious reasons one might say. I also see that cosmologists never really say there is no God. They just say that there was something mysterious and now we can explain it and by extension what remains mysterious will also be explained eventually. Some people like mystery.

Regards,
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Cliff
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Post by Cliff »

Dear Davep and Joe et al
Firstly I have not yet looked up "orthogonal" possibly when I have I might think differently.
However, I have a sneaky feeling that we (Joe, Davep and me) may not agree on this one. I get the feeling that you are both pretty confident about your ideas on these issues. I have to admit that I am not.
I cannot get my head round infinity or the idea of everything lasting forever. However, by a similar token, I cannot get my head round there being a beginning and an end to everything. I personally feel as if I have been here (ie alive forever) I know I haven't but I cannot imagine the World without me. Sorry I am a self centred old sod full of my own self importance. Furthermore, I cannot get my head round the idea of me pegging out (again I am far too important for that to ever happen).
Yet I have a sneaking feeling it might happen erventually?.
Yes I am a Big Bang believer, to a point. Amongst other things I like the simplicity of the basic idea. Furthermore, Edwin Powell Hubble is a god to me. But I have read that although he discovered the so-called expanding Universe, he never fully accepted the Big Bang theory.
I once had a brief chat with Dr Halton Arp, almost another one of my gods.
I asked him about Hubble (who I understand Dr Arp worked with for a short time. Dr Arp said that Hubble was never really allowed to expound any theoretical ideas ideas. The astronomical establishment only allowed him to be a brilliant observer. Of course i only had a very brief natter with Dr Arp, and many others might disagree with him.
I certainly would never say that Dr Arp as greatly changed my own views.
But I must admit( being a coward) I am sitting very much on the fence.
From what I have read, neither finger printing nor even possibly DNA testing are totally fool proof techniques. So I remain a worried man.
Dare I say it I might even spout a lot more when I find out what "ortogonal" means.
The more complicated the Big Bang theory or theories gets and the more I feel uneasy. I might become a steady state man.
Woh! Steady that might be going a bit too far?
Best of luck from the Grumpy Old Codger Cliff
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