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Old August 25th 18, 12:58 AM posted to sci.astro.research
Bruce Scott[_2_]
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Default Missing matter found in the cosmic web

On 2018-07-12, Steve Willner wrote:

Dark energy, the remaining 68%, is something different still. There
is little evidence for what it is, but all the evidence I'm aware of
is consistent with its being a cosmological constant. I personally
have no problem with that. The cosmological constant has to have
_some_ value, and there's no reason that value must be zero.


Nice summary in general, just want to comment on this... you can take
the position it should be zero unless you have a reason for it. Fitting
the data is well enough (but I've seen that go wrong many times in
plasma physics where the underlying asumption of the thing and its cause
both being totally wrong and the community taking 20 years to wake up
to it). I take the position that zero is a reasonable a priori assumption,
but that if it has a value there should be a reason for it (ie, why is
it not very large). It may be like the photon mass, so small as not to
rock the boat with a theory in which it is zero and which is successful
for anything else which is known (at least below whatever it is... 5 MeV
or so for the nonlinearity in the electron scattering cross section).

Do we have solid evidence that it is _different from zero_ and if so
what does the curvature of the universe have to be? I guess if we say
68 percent of the curvature is due to the quoted dark energy fitting
then this should be something. I think if we know enough it may be a
property of space-time rather than a species of field/particle... but
I guess this is the same thing as "cosmological constant".

(does this follow from universe accelaration as per the supernovae
observations from 20 years ago? but that's negative curvature isn't it)

--
ciao, Bruce