Simon Wrote:
-------------------------------------------------------
> bernard Wrote:
> --------------------------------------------------
> -----
> >
> > One problem I have with this post is that
> you
> > throw in a number of different frontier
> questions
> > all at once and it is too much to deal with
> all at
> > once. The question of Higgs has to do with
> > completion of the Standard Model. Some of
> this
> > other stuff (vacuum energy ec. is more
> relevant to
> > things like dark matter
> >
>
>
> But they are all related. In fact according to
> the physicists the Higgs is far more related to
> vacuum energy than dark matter is. Higgs derived
> his theory from the fact there is zero point
> energy.
>
> I realise I was doing a bit of a shotgun approach
> but I think its good to keep a broad perspecitive
> clearly in focus. Why should the nature of dark
> matter be considered in isolation of quantum
> gravity ??? Its like someone studying clouds and
> coming up with a theory of clouds and another
> person studying evoporation and a different person
> studing rain.
>
>
> >
> >
> >
> > I don't much beleive in the "many worlds" or
> in
> > superstring theory. Since they have not
> produced
> > testable consequences and/or experimental
> evidence
> > supporting them, they are too far out for me
> :-(.
> >
>
> Yes they are speculative and "many worlds" is so
> unevidenced and against common sense at the same
> time that I'm completely with you on that. With M
> theory the 'basic' maths has come from theories
> that are supported by experimental evidence. The
> fact no one knows what the results mean does not
> mean some of the things they suggest should be
> ignored IMO.
>
> >
> > Probably not enough. The only way to really
> see
> > what is going on in quantum mechanics,
> > superstrings, etc. is to be able to see what
> the
> > mathematics lead to. Although I had quantum
> > mechanics in graduate physical chemistry, it
> was
> > primarily applied to the needs of chemists
> and it
> > was many years ago. Physics has come a long
> way
> > since. What I do is what scientists usually
> do
> > when dealing with areas that differ from
> their own
> > expertise; as a first approximation you go
> along
> > with what the majority of scientists in area
> of
> > science see as valid. Questions and problems
> that
> > are in the frontiers (or exotic) in that area
> I
> > consider interesting, but I don't worry too
> much
> > about them. I want to see the dust settle
> among
> > the contenders with the credentials to fight
> the
> > fight before I take sides. I particularly
> take
> > reports in popular magazines or the press
> with a
> > load of salt. My other principles are that
> 1)
> > extraordinary claims require extraordinary
> > evidence and 2) untestable theories are just
> that-
> > theories.
> >
>
> Yes I agree with all that. So where is the
> extraordinary evidence for the fact that the vast
> majority of physicists accept that the entire
> visible and detectable universe represents only 4%
> of the total ?

They suggest WMAP says as much but
> they use completely unproven and extraordinary
> theories to come to that interpretation of WMAP.
> Its pure speculation.
Not really.

The thing that distinguishes the current accepted version and things like M or superstring theory is that it is tied to experimental observations. Dark matter was introduced by the need to explain certain astronomical observations, i.e. (1)for a long time astronomers have known that the observed distribution of luminous matter and Einstein’s theory of gravity could not explain the rotation rate of galaxies, the amount of luminous mass is much too small to explain these rotation rates. The favored explanation for this is the existence of dark matter. Another characteristic leading to acceptance of any theory is its ability to predict quantitative results and then getting experimental results that agree- the more precisely the better.
You should look at:
Alan H. Guth and David I. Kaiser. 2005. “Inflationary Cosmology: Exploring the Universe from the Smallest to the Largest Scales,” Science 307: 884-890.

p. 885 “According to inflationary cosmology(1-3), the universe expanded exponentially quickly for a fraction of a second very early in its history— growing from a patch as small as 10 ^(-26) m, one hundred billion times smaller than a proton to macroscopic scales on the order of a meter, all within about 10^(-35) s-- before slowing down to the more stately rate of expansion that has characterized the universe’s behavior ever since.. .
.. . in fact inflationary cosmology leads to several quantitative predictions about the present behavior of our universe—predictions that are being tested to unprecedented accuracy by a new generation of observational techniques. So far agreement has been excellent.. .
[BOM-predictions] First, our observable universe should be spatially flat [BOM the geometry of the universe according to Einstein’s theory will depend on the ratio of the critical mass density of the universe to the actual mass density (called omega). If omega >1 the universe will be a sphere, if omega < 1 the universe will be “saddle shaped” only of omega = 1 will the universe be flat].. . Although general relativity allows any value for this ratio, inflation predicts that &#937; = 1 within our observable universe to extremely high accuracy. Until recently uncertainties in the measurement of &#937; allowed any value in the wide range of 0.1&#8804; &#937; &#8805; 2, with many observation seeming to favor &#937; =0.3. A new generation of detectors, however has dramatically changed the situation. The latest observations, combining data from the Wilkinson Microwave Anisotropy Probe (WMAP), the Sloan Digital Sky Survey (SDSS), and observations of type Ia supernovae, have measured &#937; = 1.012 (+0.018, -022)(10)- an amazing match between prediction and observation.. .
.. .
The second main prediction of inflation is that the presently observed universe should be remarkably smooth and homogeneous on the largest astronomical scales. This, too, has been measured to extraordinary accuracy during the past decades. Starting in the 1960s, Earth-bound, balloon-borne, and now satellite detectors have measured the cosmic microwave background (CM radiation, a thermal bath of photons that fills the sky. .. . After adjusting for the Earth’s motion, CMB photons measured from any direction in the sky have the same temperature to one part in 10^5 (12).
.. .
A third major prediction of inflationary cosmology is that there should be tiny departures from this strict large-scale smoothness and that these ripples (or “perturbations”) should have a characteristic spectrum. Today these ripples can be seen directly as fluctuations in the CMB. Although the ripples are believed to be responsible for the grandest structures of the universe- galaxies, superclusters, and giant voids- in inflationary models they arise from quantum fluctuations usually important only in atomic scales or smaller.. . Cosmologists parameterize the spectrum of primordial perturbations by a spectral index, ns. A scale-invariant spectrum would have ns = 1.00; inflationary models generically predict ns = 1 to within 10%. The latest measurements of these perturbations by WMAP and SDSS reveal ns = 0.977 (+0.039, -.025) (10).
%%%%
BOM-- dark matter is needed in order to have enough mass to have omega = 1 and the universe be flat as well as explaining the observed rotation in galaxies. If you want to discard dark matter, it must be replaced by something that explains all the accumulated data better and more accurately. You can't replace something with nothing-- of airy-fairy speculations.
Bernard





>
> And as far as extraordinary claims a huge
> proportion of leading physicists claim there are
> billions of other universes. My claims are damn
> right down to earth compared to the completely
> unividenced stuff coming out from the academics.
> I do realise testability and clear deinitions and
> understanding are vital though - its just a hobby
> for me though and would require going back to
> university and studying physics to even be able to
> start doing anything seriously
>
> Simon