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Author Topic: The death of classical gravity  (Read 1492 times)

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Offline tomhow

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The death of classical gravity
« on: 19:31:12, 15 June, 2011 »
I've always hated the idea of dark matter and dark energy. Both sound like a re-hash of the 19th century theory of aether.

Here is a rather elegant paper in support of Modified Newtonian Dynamics - the theoretical alternative to dark matter.

http://arxiv.org/PS_cache/arxiv/pdf/1105/1105.1873v1.pdf

I like the way they produced a simple argument from existing observations. By examining the proper motion of a very large population of wide binary star systems, they show evidence for gravity losing its inverse square law at very low accelerations (there therefore are great distances).  I'm not sure it has been properly refereed yet, but it is a nice approach.

A few views of my own on the paper.

http://astro.neutral.org/astronomy_blog/blog/item/2011/06/the-death-of-classical-gravity-and-dark-matter

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Offline Nomis Elfactem

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Re: The death of classical gravity
« Reply #1 on: 20:33:52, 15 June, 2011 »
Intersting stuff Tom - I'll have a read and feed back my thoughts !

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Offline JJB2010

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Re: The death of classical gravity
« Reply #2 on: 10:50:51, 16 November, 2011 »
Its just adding another epicycle - and has no predictive power, come back Aristotle and Ptolemy all is forgiven.

jjb

Offline Ian Straton

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Re: The death of classical gravity
« Reply #3 on: 19:23:36, 20 November, 2011 »
the problem with modified newtonian dynamics is that it doesn't explain the movements of larger scale structures in the universe (the classic example being the bullet cluster), or rather some versions of MND do but only by invoking additional mass which we can't see, which kinda sounds like dark matter to me... so in essence MND looses its explanatory power unless you also invoke DM, whereas DM hypotheses account for all the same observations without having to modify gravity.   That makes the DM models more parsimonious and therefore more likely correct..

That said I don't much like Dark matter and I like Dark energy even less but what I do like is that the physicists investigating it are very forward in saying that the use of "dark" is intended to denote something we don''t yet understand.  The whole DM/DE debate is a first rate example of science in action: we have a theory that makes a prediction, our observations don't match the predictions, therefore the theory is incorrect and we need a new one.   The really fascinating thing is the theory's predictions would be accurate if there were a lot more stuff in the universe than we can observe using light (in all its guises)...  this gives two avenues for investigation: 1) are Einsteins theories of relativity wrong? 2) is there more matter in the universe than we can currently detect?  Normally when theory and observation don't match they really don't match so only one line of investigation is needed.. Relativity is such a powerful tool that has so far predicted the outcome of every single experiment designed to test it, it would be weird if it stopped working just because you got a bit further away, granted it would also appear weird that the universe is about 96% invisible and undetectable but then no one said the universe isn't weird.. the only question really is how weird?

 

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