Are the BICEP2 results invalid? Probably not

May 20, 2014 by Brian Koberlein
Galactic radio loops, with BICEP2 region indicated. Credit: Philipp Mertsch

Recently rumors have been flying that the BICEP2 results regarding the cosmic inflationary period may be invalid. It all started with a post by Dan Falkowski on his blog Resonaances, where he claimed that the BICEP2 had misinterpreted some data, which rendered their results invalid, or at least questionable. The story then has sparked some heated debate.

So what's really going on?

For those who might not remember, BICEP2 is a project working to detect polarized light within the cosmic microwave background (CMB). Specifically they were looking for a type of known as B-mode polarization. Detection of B-mode polarization is important because one mechanism for it is cosmic inflation in the early universe, which is exactly what BICEP2 claimed to have evidence of.

Part of the reason BICEP2 got so much press is because B-mode polarization is particularly difficult to detect. It is a small signal, and you have to filter through a great deal of observational to be sure that your result is valid. But you also have to worry about other sources that look like B-mode polarization, and if you don't account for them properly, then you could get a "false positive." That's where this latest drama arises.

In general this challenge is sometimes called the foreground problem. Basically, the is the most distant light we can observe. All the galaxies, dust, interstellar plasma and our own galaxy is between us and the CMB. So to make sure that the data you gather is really from the CMB, you have to account for all the stuff in the way (the foreground). We have ways of doing this, but it is difficult. The big challenge is to account for everything.

A map of foreground polarization from the Milky Way. Credit: ESA and the Planck Collaboration

Soon after the BICEP2 results, another team noted a foreground effect that could effect the BICEP2 results. It involves an effect known as radio loops, where dust particles trapped in can emit polarized light similar to B-mode polarization. How much of an effect this might have is unclear. Another project being done with the Planck satellite is also looking at this foreground effect, and has released some initial results (seen in the figure), but hasn't yet released the actual data yet.

Now it has come to light that BICEP2 did, in fact, take some of this foreground polarization into account, in part using results from Planck. But since the raw data hadn't been released, the team used data taken from a PDF slide of Planck results and basically reverse-engineered the Planck data. It is sometimes referred to as "data scraping", and it isn't ideal, but it works moderately well. Now there is some debate as to whether that slide presented the real foreground polarization or some averaged polarization. If it is the latter, then the BICEP2 results may have underestimated the foreground effect. Does this mean the BICEP2 results are completely invalid? Given what I've seen so far, I don't think it does. Keep in mind that the Planck foreground is one of several foreground effects that BICEP2 did account for. It could be a large error, but it could also be a rather minor one.

The important thing to keep in mind is that the BICEP2 paper is still undergoing peer review. Critical analysis of the paper is exactly what should happen, and is happening. This type review used to be confined to the ivory towers, but with social media it now happens in the open. This is how science is done. BICEP2 has made a bold claim, and now everyone gets to whack at them like a piñata.

The BICEP2 team stands by their work, and so we'll have to see whether it holds up to peer review. We'll also have to wait for the Planck team to release their results on B-mode polarization. Eventually the dust will settle and we'll have a much better handle on the results.

Explore further: Blogger claims BICEP2 team acknowledging possible error in discovery of evidence of gravitational waves

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cantdrive85
1.3 / 5 (14) May 20, 2014
The big challenge is to account for everything.


Given astrophysicists are constantly "surprised" by just about every observation, the idea they know "everything" there is to know is absolutely ludicrous.
Whydening Gyre
5 / 5 (10) May 20, 2014
Given astrophysicists are constantly "surprised" by just about every observation, the idea they know "everything" there is to know is absolutely ludicrous.

The key being, CD, is the realization that the more we learn, the less we know. One can only know the "everything" they've learned so far. So, surprises are inevitable.
Uncle Ira
4.3 / 5 (12) May 20, 2014
The big challenge is to account for everything.


Given astrophysicists are constantly "surprised" by just about every observation, the idea they know "everything" there is to know is absolutely ludicrous.


@ cantdrivegood-Skippy why you spend so much time here if you hate the scientist-Skippys so much uh? Can't you find a place where there are some Skippys you like better?
cantdrive85
1.4 / 5 (10) May 20, 2014
I appreciate science just fine, the pseudoscience of mainstream astronomy (and climate "science"), not so much...

Uncle Ira
3.4 / 5 (8) May 20, 2014
I appreciate science just fine, the pseudoscience of mainstream astronomy (and climate "science"), not so much...


That was not the question, no. The question was why you spend so much time here when all the science-Skippys here make you so much unhappy? Can't you find the site that the Skippys you like hang out? You want ol Ira to hunt around to see what I can find for you when I got the extra time? I'll do that for you if you tell me what kind of Skippys you like to be around without being in the bad mood all day. I hate to see you so unhappy every day all the day.
Z99
3 / 5 (3) May 20, 2014
I found this article informative,but also full of meaningless jabber. 1) who is Brian Koberlein? is his opinion is important? Unless he is an expert (which should have been mentioned) his opinion is not worth the bits used to represent it.2) His statement that BICEP2 results are undergoing peer review is not useful. When does peer review stop? (ideally) It never does.So that statement means little- he should have said the first 6-18 months are where much critical review happens, (like the FTL neutrino claim), and its still very early yet.3)The paper's B-mode effect was order(s) of magnitude more than expected, if inflation was the cause: extraodinary claims require extrordinary evidence... Finally, its TOTALLY predictable that "the team" will "stand behind" the work. That's human nature.My opinion (LOL) is that unless the "data scraping" was done with the Planck team's blessing, then it is a serious blunder not to have done the analysis with and without it & clearly mentioned it.
Z99
2 / 5 (1) May 20, 2014
P.S. I actually can spell "extraordinary". I ran out of space, and presumed meaning was clear. I have not read the BICEP2 paper, so its possible that they did acknowledge the crude way they included the Planck information...although if the "pdf slide" was an image, then its inclusion without further communication with the Planck team is risible. Since when is it good science to use data which has NOT (yet) been through peer review???
Pejico
May 20, 2014
This comment has been removed by a moderator.
TheGhostofOtto1923
4.3 / 5 (6) May 20, 2014
I appreciate science just fine, the pseudoscience of mainstream astronomy (and climate "science"), not so much...
Only godders think they know everything. And psychopaths. For similar reasons.
Urgelt
1 / 5 (1) May 20, 2014
I thought the article was sensible enough. But i, too, would like to know if the author is a subject matter expert in the field, or just a science journalist, when he weighs in with his personal opinion.
marjinsopmar
2.3 / 5 (3) May 20, 2014
Come on, Brian. You claim to be supporting the BICEP2 results, but you make no mention of Raphael Flauger's presentation last week at Princeton? The reason why scientists have lost confidence in the BICEP2 results is because of the devastating presentation made by Flauger, in which he showed that basically all of the BICEP2 observations can be explained by gravitational lensing and dust (a simple explanation) rather than gravitational waves or primordial cosmic inflation. See my blog post below for a summary of the presentation, along with a link to it:
http://www.future...ose.html
Uncle Ira
3.7 / 5 (6) May 20, 2014
I thought the article was sensible enough. But i, too, would like to know if the author is a subject matter expert in the field, or just a science journalist, when he weighs in with his personal opinion.


Well you Skippys could just google scientist-Skippy's name like ol Ira did it. The Brian-Koberlein-Skippy is the astrophysics professor at the Rochester something Institute.
rah
1 / 5 (4) May 20, 2014
No. This claim by the Bicep2 team is not simply erroneous. It is a straight fraud in the final analysis. Do not be fooled when the claim is shown to be wrong and the guy making the claim is allowed to continue doing work as if he had just made an embarrassing boo-boo. A good part of the blame goes to the basic science illiteracy of journalists and editors who should not have accepted what would have been (which they should have spotted immediately) the discovery of their lifetimes. The foreground error is just one of a long list of variables which had to be adjusted just right to get the results he (Kovacs) decided to get. It's likely criminal and should be investigated.
vidyunmaya
1 / 5 (5) May 20, 2014
Sub: COSMOLOGICAL INDEX-MILKYWAY SENSEX-VISIBLE -INVISIBLE MATRIX
Plasma Regulated electromagnetic Phenomena in Magnetic field Environment holds the key at the milky Way Galactic Frame. Cospar 2013 , Super-imposition of Visible-Invisible Matrix--Research Paper by Vidyardhi Nanduri provides the inputs. The question of gravitational waves here do not contribute to any sensitive index at Milky way -see COSMOLOGICAL INDEX-MILKYWAY SENSEX-VISIBLE -INVISIBLE MATRIX 2010..TXU 1-731-970 - SPACE SCIENCE-Reports Cover [ESA]-2010- PROPOSALS-Environment-Sensex-Earth-Glow-Sun Life-Significance - Human Being in-depth-Milky-way Sensex-Aditya links Book by Vidyardhi Nanduri
adam_russell_9615
5 / 5 (1) May 21, 2014
The big challenge is to account for everything.


Given astrophysicists are constantly "surprised" by just about every observation, the idea they know "everything" there is to know is absolutely ludicrous.


"...as we know, there are known knowns; there are things that we know that we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns, the ones we don't know we don't know."
Donald Rumsfeld
cheers
theon
1 / 5 (2) May 21, 2014
All this ugly back stepping. It would have been more honest to admit that the searched media hype had better be avoided.
Torbjorn_Larsson_OM
5 / 5 (3) May 21, 2014
They did account for the foreground in many different ways that came to the same estimate of the dust contribution. [Se the BICEP2 data release.] It is Planck that may be putting out an exceptional result that needs exceptional checking. And unfortunately I don't think it covers the relatively clear polar window, their shown dust mask for example is concentrating on the worst parts (galactic contribution).

A personal upshot is that I thought Planck had confirmed BICEP2 by estimating dust contribution as 15 % at most. Alas, this cosmology layman had read the latest Planck data release sloppily.
Torbjorn_Larsson_OM
5 / 5 (4) May 21, 2014
Re astrophysicists, it is an observable fact that they are not "constantly" surprised. That's why the troll leaves no references to such a description that has passed peer review, by the way.

The absence of surprises lately is why we have the concordance cosmology now, where "everything" fits. (There are outliers, but it is not known if they add new physics.)

And that is why these data, that fits both the cosmology signal part and the dust emission models negligible enough part (so far), that made the scientists excited. They _want_ surprises, because it points to new physics or at least misunderstood ones. BICEP2 is a little bit of both (Planck preliminary data pointed to a lower signal; the signal is string enough that the physics must be trans-planckian vs changing field values.)
Torbjorn_Larsson_OM
5 / 5 (3) May 21, 2014
@theon: " It would have been more honest to admit that the searched media hype had better be avoided."

Did you read the article? Koberlein suggested just that, it was the point of the article. "This type review used to be confined to the ivory towers, but with social media it now happens in the open."

@Uncle Ira: IIRC, cantdrive is a creationist trolling about his magic. At least he is antiscience.

@Z99, Pejico: Brian Koberlein is an astrophysicist (google!). His voice is among those who counts.
Torbjorn_Larsson_OM
4 / 5 (4) May 21, 2014
@Z99: Peer review doesn't stop, but it can converge on a consensus either way, or conclude that the question is still reasonably open. That awaits Planck (or other) data, you forgot that part: "We'll also have to wait for the Planck team to release their results". This is science described as normal science, e.g. no pseudoscience but data driven.

"The paper's B-mode effect was order(s) of magnitude more than expected, if inflation was the cause".

No! No, no, no. It was exactly on the money of many inflation mechanisms, Linde's chaotic inflation premier among those. It was "order(s) of magnitude more than expected", if exotic string theory or ekpyrotic theory was the cause. It was twice as strong as expected from earlier Planck constraints (but still within 2 sigma, IIRC).

[tbctd]
Torbjorn_Larsson_OM
4.2 / 5 (5) May 21, 2014
[ctd]

"its TOTALLY predictable that "the team" will "stand behind" the work. That's human nature."

Sure, but it is also scientist nature to reverse themselves if early peer review pointed out a mistake. (Or they loose credibility.)

BICEP2 dedicated 1 year (!) to make sure that wouldn't happen. And it didn't. " the Planck foreground is one of several foreground effects that BICEP2 did account for". Exactly right.

"then its inclusion without further communication with the Planck team is risible."

It's an included reference in the paper. If you read Resonaances comments, you will see links to where they explain that they communicated with the Planck team, then did the best what they could with what they got.

Planck is a large effort with many participants, its data handling process is complicated, and to get clear or even correct responses while they themselves crank the process and has little overview is unlikely.
Torbjorn_Larsson_OM
5 / 5 (3) May 21, 2014
So, since there is so little interest in the science and so high crank-to-sane ratio in the remaining thread, this will be my last effort to promote science here:

@Marjinsopmar: Thanks, interesting.

But: "He has a BS degree with a major in philosophy", indeed. So you/Mahin [sp?] have no access to data that supports claiming "scientists have lost confidence in the BICEP2 results", even one of them. So far there are rumors of a problem as described here, you present a separate critical analysis that disregard BICEP2 dust models, and it is not clear if Flauger has lost confidence. (Maybe he has said so, making it one (1) scientist after all.)

On that analysis: If Flauger's 2 agreeing methods counts, BICEP2's handful agreeing ones count as well. BICEP2 is the one using the conservative data, Flauger is the one with the new models. And I would have to read the seminar to see where Flauger took his models, if he really put out his chin on this or just pointed out a putative discrepancy.
Torbjorn_Larsson_OM
5 / 5 (3) May 21, 2014
Nope, Flauger hadn't "lost confidence". He was actually working with some BICEP2 members (Choi) unless I'm mistaken, uncovers a small mistake in the analysis and is able to put up new uncertainty bands - with much extrapolation!.

Last 2 slides:

"Conclusions
• 100 GHz Keck Array data will be available soon
• Three frequency BICEP3/Keck Array data (coming 2015?),
should be able to characterize foregrounds
• Planck will soon release its polarization data which will be
extremely valuable for our understanding of foregrounds
because of its frequency coverage
• Luckily, Planck's noise is lower in the BICEP patch than average
• If the tensor to scalar ratio is 0.1 or larger, Planck may also be
able to confirm the measurement directly
• We will have additional data from many more polarization
experiments soon and get a definitive answer"
bluehigh
2 / 5 (4) May 21, 2014
Martin Fleischmann must be turning in his grave. I wonder what Stanley Pons might have to say about premature publication and experimental reproducibility of the BICEP2 conjecture (kind of ... 'you call that empirical evidence').
Torbjorn_Larsson_OM
5 / 5 (4) May 21, 2014
A final word on Flauger's analysis: it comes under heavy criticism itself, as I expected, in the comments here: http://resonaance...cep.html . It is only if you assume BICEP2 did it wrong, and he did it right, that you get a discrepancy. The jury is still out, and that is likely why he himself was cautious.

Worse, there is a discrepancy between Flaubert's column density models and the BICEP2. Meaning (unless I am mistaken) that some signal is there regardless, because the dust contribution is too constrained. (I don't get why, but it is apparent from his model slides.) There are comments to that effect too in that thread.

So: no need to distrust BICEP2 particularly yet, they likely have something. For final verdict we need more data. As usual. =D
yep
1.6 / 5 (5) May 22, 2014
"So, since there is so little interest in the science and so high crank-to-sane ratio in the remaining thread, this will be my last effort to promote science here"
Quite an ironic statement considering the premise of a big bang cosmology, with the assumption of an afterglow, in the speculation of separating the foreground signal from CMB, while postulating Einsteins gravitational waves.

Pejico
May 22, 2014
This comment has been removed by a moderator.
rah
1 / 5 (1) May 26, 2014
The Keck Foundation and the National Science Foundation, Gordon Moore Foundation and other investors in the Bicep2 experiment need to do a really thorough audit of that program. not for the money, but for their reputations.