Dark energy doesn't exist?

Paper:
http://iopscience.iop.org/0004-637X/...X_803_1_20.pdf

[[Mod. note -- See
http://arxiv.org/abs/1408.1706
for the open-access preprint. The journal paper is pay-walled .
-- jt]]

Explanation of that paper
http://www.eurekalert.org/pub_releas...-aun041015.php

quote
"The realization that there were two groups of type Ia supernovae
started with Swift data," Milne said. "Then we went through other
datasets to see if we see the same. And we found the trend to be present
in all the other datasets.

"As you're going back in time, we see a change in the supernovae
population," he added. "The explosion has something different about it,
something that doesn't jump out at you when you look at it in optical
light, but we see it in the ultraviolet.

"Since nobody realized that before, all these supernovae were thrown in
the same barrel. But if you were to look at 10 of them nearby, those 10
are going to be redder on average than a sample of 10 faraway supernovae."

The authors conclude that some of the reported acceleration of the
universe can be explained by color differences between the two groups of
supernovae, leaving less acceleration than initially reported. This
would, in turn, require less dark energy than currently assumed.
end quote

OK. This looks like the paper I cited a few days before.

Is it an alien intelligence or just a microwave oven?

Two populations of supernovas would explain dark energy. The authors are
careful to say that "*some*" of the dark energy can be explained away
but I am strongly confident that the whole thing will deflate soon.

It seems to me that if the scale of the universe were shrunk by
sqrt(2), that dark matter would no longer be needed, but I don't have
the math to test that. Were it true, it would be a minimalism type of
argument against current distance scales.


[[Mod. note -- We now have fairly good observational constraints on the
astronomical distance scale, with error bars much smaller than a factor
of sqrt(2). (This didn't use to be the case.)

For example, in this newsgroup on 2012-11-29, Craig Markwardt posted
article , cached at
http://www.spacebanter.com/showpost....2&postcount=23
describing various water-maser observations which give us absolute
distances to the galaxies NGC 4258, UGC 3789, and NGC 6264.

More recently, Reiss et al (Ap.J 785,161 = astro-ph/1401-0484) describe
a clever "spatial scanning" technique to use HST to directly measure
trigonometric parallaxes (-- absolute distances) of bright stars --
including some classical galactic Cepheid variables -- up to 5 kiloparsecs
away.

And GAIA (http://en.wikipedia.org/wiki/Gaia_%28spacecraft%29) is currently
in the process of a 5-year mission to measure (among other things) absolute
distances of ~1e9 galactic stars, which will (among other things) greatly
tighten the error bars on the astronomical distance scale.
-- jt]]

[[Mod. note -- We now have fairly good observational constraints on the
astronomical distance scale, with error bars much smaller than a factor
of sqrt(2). (This didn't use to be the case.) ...
... water-maser observations which give us absolute
distances to the galaxies NGC 4258, UGC 3789, and NGC 6264.

Of which, the first 2 are low redshift and might have large proper
motion components. NGC 6264 has z=0.033, so would provide good
corroboration of water maser measured distances, but the paper
describes its analysis as "Bayesian" and leaves lots of wiggle room.
I don't have evidence for any other distance scale (apart from that
the current distance scale requires "dark matter" which has gotta be
the biggest elephant in any room, evah!) , but there's an unfortunate
tendency to publish tentative findings which are then cited as
something more certain. In this vein are papers which supposedly
measure the CMB background temperature in earlier epochs, about which
I've previously posted in this forum. My point is only that error
estimates should be given and subsequently respected, especially as
older literature typically have (in hindsight) actual errors twice as
large as their estimated errors.

On Sun, 12 Apr 2015 22:20:35 EDT, jacobnavia
wrote:

Paper:
http://iopscience.iop.org/0004-637X/...X_803_1_20.pdf

[[Mod. note -- See
http://arxiv.org/abs/1408.1706
for the open-access preprint. The journal paper is pay-walled .
-- jt]]

Explanation of that paper
http://www.eurekalert.org/pub_releas...-aun041015.php

I was surprised and maybe you will be too if you look at National
Science Foundation's page, listing a maximum of 3000 awards concerning
dark energy. Just the titles are listed.
The website is a little tricky; I simply copied it including the
search term dark energy. One computer finds it, the other does not.

http://www.nsf.gov/awardsearch/simpl...queryText=dark
energy.
The awards range from $10,000-$10,000,000; "A maximum of 3000"!

It does seem to me that their papers should be available to the
taxpayer. I thought I saw a remark somewhere that they are planning to
maybe make some of it available.
It is hard to discern whether some of them might possibly deny dark
energy. I think here is an example of a government that's simply
lavishing money on science with no payoff-where are the papers?
Dark energy of course is just a narrow discipline; there are also lots
of other topics.
Take a look
John Polasek

In article , Eric Flesch
writes:

[[Mod. note -- We now have fairly good observational constraints on the
astronomical distance scale, with error bars much smaller than a factor
of sqrt(2). (This didn't use to be the case.) ...
... water-maser observations which give us absolute
distances to the galaxies NGC 4258, UGC 3789, and NGC 6264.

I think that the original poster's claim (that changing distances by
sqrt(2) would alleviate the need for dark matter) is more than a little
vague.

More to the point, the distance scales from the CMB and from more local
measurements agree to better than sqrt(2). While it might be possible
to wiggle enough to get sqrt(2) somewhere, this would upset other
concordances.

I think the situation in cosmology today is rather like that a bit more
than 100 years ago with regard to the reality of atoms and hence
determinations of Avogadro's number. There was no single experiment
which clenched it, and any single experiment could have been wrong, but
independent lines of reasoning converging on the same answer would have
required a highly improbably conspiracy if this were not the right
answer.

[[Mod. note -- Please limit your text to fit within 80 columns,
preferably around 70, so that readers don't have to scroll horizontally
to read each line. I have manually reformatted this article. -- jt]]

On Friday, April 17, 2015 at 11:22:10 PM UTC-4, Eric Flesch wrote:
... water-maser observations which give us absolute
distances to the galaxies NGC 4258, UGC 3789, and NGC 6264.

Of which, the first 2 are low redshift and might have large proper
motion components.

You mean peculiar velocity.

For NGC 4258, the cepheid-derived distance, the Hubble-derived
distance based on redshift, and the megamaser-derived distances all
agree to within the errors (few 10s of km/s in Doppler shift). Also
NGC 4258 is not need in the potential well of a cluster of galaxies.
So it's highly likely that NGC 4258 has a small peculiar velocity
compared to the Hubble flow. (You might argue that there is a
sqrt(2) distance effect that somehow is almost exactly balanced by
a ~200 km/s peculiar velocity so that they cancel, but then who
would be invoking a fine-tuning argument?)

For UGC 3789, you say it's at a "low redshift" but in truth the
redshift in terms of Doppler shift is about 3500 km/s; it's starting
to get up there. The megamaser-derived distance agrees with the
Hubble distance to within about 10%. A 40% distance error as you
suggest would demand a 40% peculiar velocity to maintain this
agreement, or about 1300 km/s. That is a pretty large peculiar
velocity. But based on nearby galaxies in the flow the peculiar
velocity is only estimated to be about 150 km/s. So such a large
distance error looks pretty implausible.

NGC 6264 has z=3D0.033, so would provide good
corroboration of water maser measured distances, but the paper
describes its analysis as "Bayesian" and leaves lots of wiggle room.

Bayesian means a particular statistical formulation for analysis.
By itself the use of Bayesian statistics is not a reason to discredit
a result.

Which specific parts of the paper leave "lots" of wiggle room?

Let's bear in mind that this completely independent line of analysis
and data for UGC and NGC, just *happens* to lead to the same value
of the Hubble constant to within the errors!

CM