Matter Map

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

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Hampshire Astronomer
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Matter Map

Post by Hampshire Astronomer »

Cosmologists at the University of Durham have produced a map of the distribution of matter in the Universe. The simulation took a supercomputer 11 days to produce and could help shed light on the nature of dark energy - a repulsive force thought to counteract gravity.

The map has been displayed on the BBC Science/News website, and can be found via this link:
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Post by Eclipse »

Anti -gravity?? A fortune awaits the guy who can patent that.
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Re: Matter Map

Post by gyro »

Hampshire Astronomer wrote:The map has been displayed on the BBC Science/News website, and can be found via this link:
Dave,
Could you expand on the link please, I can't find the write-up/article and the Durham Uni' site doesn't give much info'.

Thanks.
Regards.
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Post by Cliff »

Dear al(L)
I gather the matter distribution map is actually just a computer simulation.
Ironically I once attended a lecture by a cosmologist from Durham and he misidentified M31. So I'll sit on the fence about this "matter" for a while.
Best of luck from Cliff
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Post by joe »

Cliff wrote:I gather the matter distribution map is actually just a computer simulation.
Yes, Hampshire Astronomer pointed this out in his second sentence. :wink:
The simulation took a supercomputer 11 days to produce and could help shed light on the nature of dark energy
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Post by Hampshire Astronomer »

I once attended a lecture by a cosmologist from Durham and he misidentified M31
Wonder if it was the same cosmologist that discovered that new supernova...what was it called now.....errrr....oh yeah thats right SATURN :-)

Funny because its true :-)

Dave
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Post by Cliff »

Dear Joe and Dave
Joe; You are quite right. Hoever, what I was trying to imply is that being a computer model I think there is a very strict limit to the amount of light that such methods can produce. It may be an exaggeration to suggest it but I am inclined to think that the limits of cosmology are computer extapolations of extrapolations. It is rather like (though I admit not necessarily exactly like, chaos theory whereby things can eventually go wonky and unpredictable.
I myself am a fan of Mond, but not because I think it is exactly right, but in a similar way to Bohr's model of the hydrogen atom, within reason it works.
I have always been a big fan of the Big Bang but I gather that because of some technical problems, beyond my understanding, to make the Big Bang work "inflation" has been introduced. Now I cannot say inflation is right or wrong. So I am prepared to half accept inflation but half think of it as rubbish ie there is another as yet unknown explanation, which either confirms the Big Bang idea or takes us in another completely different dirrection. Whichever, proves to be the case does not bother me personally one iota.
Dave: It is just conceivable that the cosmologist I referred to with regards the M31 mistake just suffered a brief mental block. However, the fact he mde the same mistake twice during his talk did not inspire me.
What did occur to me though was that the cosmologist was of course very much a theorist. Now I have no doubt the cosmologist could have run rings round not just me but everyone else in the audience with regards cosmological theories. Having said that I suspect most people in the audience of amateur astronomers probably realised the particularl galaxy referred to by the cosmologist was not M31.
Now it may be that everything else the Cosmologist said during his lecture was 100 percent correct, but I cannot say it inspired me with confidence. Indeed it made me think even more than ever that maybe csmological theory and cosmological reality might be two very different things.
Best of luck from Cliff
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Post by ajb »

You may be able to find more information from the The institute of Computational Cosmology at Durham.

You could try to find related papers using uk.arXiv.org e-print archive mirror.
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Post by Cliff »

Dear ajb
Thanks for pointing us at the internet sources you provided.
I have taken a quick look, but would need much longer to make any sort of appraisal. Even after that I would probably not feel much clearer in my understanding than I am at present. That is not necessarily meant as a critiscism of the information (but could be -though hardly fair if I had not even attempted top read it properly which is the current situation). If I were a little younger I might like to study the issues more deeply, just as I might want to understand Relativity much more than I do. I have to admit it is probably rather cowardly of me to be critical of any theories arguably on the basis that I do not understand them. Having said that if theorists are to satisfy others then I think they must be able to provide satisfactory basic information and evidence to support their case. If they don't (or cannot) then they can hardly blame people for not trusting them.
I can only ask is there any case for say asking cosmologists to step back and forget many apparently semi-accepted current theories and start afresh as if those theories do not exist. Of course that might well be a silly idea, and just pie in the sky to expect that.
Arguably I am just as guilty as the cosmologists I knock, since my own ideas are based on very simplistic thoughts with little or no concept of the technicalities involved.
Even so with the best will in the world, although I may have the best intentions, at this minute in time, give me a while longer I will almost certainly fall back to my old simplistic critical ideas again quite soon.
Best of luck from Cranky Old Cliff
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Post by JohnH »

I can only ask is there any case for say asking cosmologists to step back and forget many apparently semi-accepted current theories and start afresh as if those theories do not exist.
Well, that's what they asked Galileo to do when he insisted that he was right to believe the unlikely idea that the earth moves around the sun! And there wasn't really enough solid evidence at that time to be quite so sure, so his critics had some valid reasons for saying "hold on".

But theoreticians have to go out on a limb and support their views as strongly as they can - and leave others to find evidence to support them, or to prove they are wrong. That's the only way science can progress.[/quote]
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Post by Cliff »

Dear John
We could say with respect to Galileo that he was right (although I gather he did edge his bets a bit when shown the Inqisitions instruments of torture, which seems quite a sensible thing to do for me).
However, can you tell me that the cosmologists are right and if so which one.
Best of luck from Cliff
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Post by T Russell »

If memory serves correctly, I believe Galileo observed the phases of Venus through his telescope something which cannot be explained in a geocentric solar system. The problem with computer simulations is that they are just that - simulations which may or may not bear any relation to reality.

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Post by KendalAstronomer »

Cliff wrote:Dear John
We could say with respect to Galileo that he was right (although I gather he did edge his bets a bit when shown the Inqisitions instruments of torture, which seems quite a sensible thing to do for me).
However, can you tell me that the cosmologists are right and if so which one.
Best of luck from Cliff
Certainly, wait a few centuries and we'll apply the same hindsight to the cosmologists of today as we can apply to Galileo.

Computer simulations are not pulled out of thin air. They follow the same rules of development as any other theory, the difference being they can handle far more calculations than a human can. This means they do their calculating more explicitly, whereas humans would have to produce a simplification when encountering a complex calculation, long iteration and/or a calculation that would have to be repeated often. These simplifications then get propogated as theories develop in the same way as the extrapolations of extrapolations that Cliff complains about with the computers. The only difference between a theory with computer models and one without is that one has equations calculated with a computer and the other doesn't. They both still use extrapolations of extrapolations and throughout history it is these that get tested - the theoretical predictions.

...and the only person who could say which cosmologist was right or wrong would be the cosmologist whose model (computer or otherwise) fits the data best.

Current cosmology is not a homogenous field and includes many different takes on all the various ideas out there. They are all constrained and compared to the data gathered. The only reason to step back and think again is when the theory produces a result apparently incompatible with the data, unless that happens there's nothing you can do to challenge a theory, except bring out a better performing one.

As for explaining theories in simple terms, that's done when they are well developed enough. A scientific paper is just that, an on the job technical paper meant as an announcement of something new in the field for other scientists to accept or decry.
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Post by JohnH »

T Russel: If memory serves correctly, I believe Galileo observed the phases of Venus through his telescope something which cannot be explained in a geocentric solar system.
I don't intend to nit-pick but there were three "theoretical models" at that time. The highly respected Tycho Brahe had suggested that the earth is stationary and the sun revolves around it - but that the planets revolve around the sun. This would also have explained phases of Venus.

All I was saying is that, while Galileo's view seems obviously "true" in hindsight, it was scientifically respectable to be very cautious at a time when the facts were still very limited. (And on top of that, there was a lot of "religious baggage" to be overcome).

And science doesn't really deal in "truth". Scientists try to put forward theories to explain observed facts - and they (and especially others) have to continue to test how far a theory really does fit the facts, however counter-intuitive, or however well established, the theory may be. It's the duty of scientists to try to come up with possible new suggestions, whether the ideas come directly from a scientist's mind or from a computer model. It's also their duty to do their best to pick holes in old or new theories (or more likely, in other people's theories!)
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Post by Paul S »

JohnH wrote:Scientists try to put forward theories to explain observed facts
Yes they do. But they also do something else. For me, the best and most exciting science comes from theoretical predictions that are later backed up by observations.
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