

Big Bang finding challenged - d0mine
http://www.nature.com/news/big-bang-finding-challenged-1.15352

======
mahranch
From the abstract of the paper: "The expected amplitude of the dust
polarization power spectrum remains uncertain by about a factor of three. The
lower end of the prediction leaves room for a primordial contribution, but at
the higher end the dust in combination with the standard CMB lensing signal
could account for the BICEP2 observations, without requiring the existence of
primordial gravitational waves."

Two things to note. First, they aren't saying that is is wrong, only that it
_could_ be wrong. Second, the source of this doubt appears to come from a
single professor at Princeton.

~~~
T-A
Not just one. This has been mounting for a while:
[http://resonaances.blogspot.se/2014/05/is-bicep-
wrong.html](http://resonaances.blogspot.se/2014/05/is-bicep-wrong.html)
[http://resonaances.blogspot.se/2014/05/follow-up-on-
bicep.ht...](http://resonaances.blogspot.se/2014/05/follow-up-on-bicep.html)
[http://resonaances.blogspot.se/2014/05/weekend-plot-bicep-
li...](http://resonaances.blogspot.se/2014/05/weekend-plot-bicep-limits-on-
tensor.html)

Note also Steinhardt's opinon piece: [http://www.nature.com/news/big-bang-
blunder-bursts-the-multi...](http://www.nature.com/news/big-bang-blunder-
bursts-the-multiverse-bubble-1.15346)

~~~
mahranch
> " _Not just one._ "

But you linked to random blogspot articles, and Steinhardt is the guy who the
first source is referencing. His name is mentioned in the byline. He's the guy
from Princeton I mentioned. All of this is mainly coming from him, and those
blogs you linked are the result of his statements (aka opinion sprawl).

~~~
T-A
The "random blog posts" are by Adam Falkowski, a particle physicist who has
been following the controversy over BICEP2 from the start. They document how
opinion has been swinging over time.

Steinhardt is not "the guy who the first source is referencing". The two
references in the first source are

1) [http://arxiv.org/abs/1405.5857](http://arxiv.org/abs/1405.5857) , by
Mortonson and Seljak, both at LBNL and UC

2) [http://arxiv.org/abs/1405.7351](http://arxiv.org/abs/1405.7351) , by
Faluger, Hill and Spergel, from IAS, NYU and Princeton, respectively.

As you may have noticed, none of them is Steinhardt.

------
chakademus
Physicist here: the BICEP2 findings have a fair chance of being borne out, but
I do feel that the BICEP group was a bit premature claiming definitive
detection.

The doubts of independent groups, and the need for further experiments to
confirm the results is the scientific method and community working as
intended.

Ultimately, its mostly been the sensationalistic media coverage that makes the
situation seem more controversial than it really is.

~~~
darkmighty
With the original announcement came a "five sigma" or so claim. Was that
misleading or not? (was it plain wrong?) I mean, I'd expect from hearing
something like that that unless the underlying theory changes the hypothesis
is almost certainly true. Or is the uncertainty figure given in a more limited
sense?

~~~
betatim
If you are making a systematic mistake (not necessarily an error, could also
be an approximation that doesn't hold) in your analysis, the "5sigma" does not
really take that into account.

Struggling to come up with a simple example. Imagine you collect some data,
analyse it and see a "3sigma" effect. You decide to collect more data to see
if the effect keeps getting bigger or goes away. After collecting a lot more
data you get "5sigma". This could be because it is real, or because you have
an "unknown unknown"

If you had a systematic (as oppose to a random effect) shift in your analysis,
collecting more data will make you more sure that there is an effect. Even
though all you are seeing is the effect of the systematic shift.

For almost all analyses in particle physics (or astro or ...) we spend a huge
part of our time evaluating "systematics", it isn't uncommon that this part of
the analysis takes a lot longer than the nominal result. Unfortunately this
only protects you against known unknowns. You can't take into account things
you don't think of/check for.

~~~
choffstein
I suppose if your estimator is biased and not consistent -- due to some sort
of omitted variable -- you can end up with "significant" estimates that are
completely removed from reality. Great explanation at
[http://eranraviv.com/blog/bias-vs-
consistency/](http://eranraviv.com/blog/bias-vs-consistency/).

