Of Particular Significance

The BICEP2 Dust-Up Continues

POSTED BY Matt Strassler

POSTED BY Matt Strassler

ON 05/30/2014

The controversy continues to develop over the interpretation of the results from BICEP2, the experiment that detected “B-mode” polarization in the sky, and was hailed as potential evidence of gravitational waves from the early universe, presumably generated during cosmic inflation. [Here’s some background info about the measurement].

Two papers this week (here and here) gave more detailed voice to the opinion that the BICEP2 team may have systematically underestimated the possible impact of polarized dust on their measurement.  These papers raise (but cannot settle) the question as to whether the B-mode polarization seen by BICEP2 might be entirely due to this dust — dust which is found throughout our galaxy, but is rather tenuous in the direction of the sky in which BICEP2 was looking.

I’m not going to drag my readers into the mud of the current discussion, both because it’s very technical and because it’s rather vague and highly speculative. Even the authors of the two papers admit they leave the situation completely unsettled.  But to summarize, the main purpose and effect of these papers seems to be this:

  1. to point out that the level to which dust tends to be polarized, as measured by the Planck satellite team in their very recent paper, is larger than most people expected: twice as large, or more, than assumed by BICEP2 in some of their arguments;
  2. to remind us that the effect of the dust on the BICEP2 polarization signal increases like the square of the dust polarization — i.e., a doubling of the dust polarization means a quadrupling of the contribution of the dust to BICEP2’s measurement;
  3. to try to convince us that the uncertainties about dust are currently too large for anyone to draw conclusions as to the meaning of BICEP2’s measurement — as to whether it is due to gravitational waves, to polarized dust, or to a combination of the two [along with small effects from synchrotron radiation and from gravitational lensing of E-mode polarization of the cosmic microwave background];
  4. to note that new measurements relevant for determining the dust effect are on their way on the 6 to 12 month timescale, so these issues may soon be resolved — although it may not be so easy, because precise determinations of the dust polarization, and proper combination of measurements by different experiments, will be needed for an unambiguous measurement of any gravitational wave contribution to BICEP2’s B-mode polarization.

Regarding the last point, the most important measurements in question will come

  • from the BICEP2 team itself, whose next-generation experiment KECK, already running, is basically five BICEP2’s in tandem, and will cover two different microwave frequencies, and
  • from the Planck satellite at a range of frequencies.


Both papers make some basic points that undermine confidence in BICEP2’s case against dust (e.g. by arguing that BICEP2, by overestimating the intensity of dust emission as measured by Planck, was led to strongly underestimate the average amount of dust polarization; that BICEP2 disregarded lensing effects in one of its arguments against dust; that BICEP2’s evidence that their data was uncorrelated with dust measurements carries no weight).  But when the papers try to make more quantitative statements about just how big the dust effect could be… well.  As far as I can tell, the methods used involve arbitrary judgment calls, and in the second paper these aren’t even clearly explained, and lead to key claims that can’t be verified by the reader.  That said, I’m not suggesting that anyone could do any better right now, given how little information we have about polarization in the BICEP2 region.  But I would suggest that experts read the words in these papers very carefully before attempting to evaluate the plausibility and reliability of the most important plots shown.

Since the whole discussion is currently so vague, I probably won’t say more about this until someone says something more convincing, or until BICEP2 publicly responds, if they choose to do so. The bottom line, for now, is clear enough: BICEP2 hasn’t made a case that overwhelmingly convinces the world’s experts.  The community will therefore remain collectively undecided until a precise determination is made of the amount of polarized dust in BICEP2’s region of the sky.  That lies six months to a year in the future. Until then, our knowledge will remain hazy.

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61 Responses

  1. In some theories the universe looks ringing like a bell or something. Such a theories really exist due to presence of spherical modes of CMBR. But the CMBR is noisy and you can see a dodecahedron in it too. One distribution violates the another one, so you can observe both but just in impure state only. IMO it’s because at the extreme distance scales the time and space dimensions are blurred mutually and the Universe behaves like mixture of transverse and longitudinal waves, i.e. the spherical surface ripples and gravitational waves, which undergo particle packing geometry like the foam. Just the dodecahedron mode of CMBR therefore corresponds the gravitational waves, which the BICEP2 and Planck cooperation looked for. In this sense we observed these gravitational waves already before some time in COBE/WMAP data. Once these modes don’t fit the E8 Lie group geometry, then it’s evident, they do contain some transverse component and as such they cannot represent a pure B-mode or gravitational waves. The Lie group essentially describes the tightest packing of hyperspheres, formed with exchanging of energy between itself.

    One of problem with BICEP2 signals, it should be the more intensive, the more distant is and therefore “reddish”. But the BICEP2 signal exhibits a a blue tilt – i.e. its formed with something, which was created AFTER deionization, not BEFORE it. If we admit, that the “gravitational waves” searched are the dodecahedral mode of CMBR fluctuations, then everything looks OK, because just this mode represents the largest structures observable on the sky. But such large structures cannot be observed with tiny sampling window of BICEP2 polar observatory reliably.

    So in brief: what the BICEP2 is looking for is the dodecahedron mode of CMBR and the background is formed with dark matter filaments between galaxies and it should be subtracted from signal too.

  2. What the BICEP2 cooperation is still missing is the structure of dark matter fibers across the whole sky. The dark matter background AROUND galaxies was indeed filtered out from data, but the fibers BETWEEN galaxies were not. The dust background implies, that the background signal will disappear when we look at “proper” spot of the sky (from technical reasons the BICEP2 scanned only narrow region around south pole). But IMO this background is systematical, quite intensive and it essentially blurs the option, that we could ever observe the primordial gravitational waves before inflation.

    Dark matter fibers were already observed independently (1, 2). There is no apparent reason, why not to account them into background data of BICEP2. The watching of isolated narrow spots on they sky from the Earth is a cheap technology, but it isn’t the most systematical/effective way, how to do it. The astronomers therefore have to wait for Planck polarization data, once they will be released. The signal of true gravitational waves should shrink with increasing frequency, the background signal of dark matter filaments will expand with increasing frequency of radiation used for observation. In this way both signals could be separated computationally with FFT analysis of the spectra. The tiny localized spot of BICEP2 is a nice technological achievement, but the amount of data provided is not sufficient for reliable analysis of CMBR spectra.

  3. Some harsh critique of BICEP2 hype, and the inflationary paradigm in general, by Paul Steinhardt:

    Steinhardt’s final conclusion? :
    ” … it is clear that the inflationary paradigm is fundamentally untestable, and hence scientifically meaningless. … ”

    Mainly because inflationary paradigm leads to untestable and/or unobservable “multiverses” (my understanding of his article).

    1. TomH:- Like Strasser, Steinhardt is way behind the times. It was known as soon as the BICEP2 team report materialised that they had no CMB detections. In fact, it was known long before their report materialised that they would never make any CMB detections. Strasser and Steinhardt are either ignorant of the reports made long before them, or are otherwise failing to acknowledge them. Certainly they both now know about them, as does the BICEP2 team. But, as usual, silence is apparently golden.

      BICEP2 Fallacies

      Professor Pierre-Marie Robitaille: The Cosmic Microwave Background

      Professor Pierre-Marie Robitaille, ‘On the validity of Kirchhoff’s Law’

      As for the multiverse, that too was long ago proven fanciful, as this article reveals:


  4. This is old news. Matt Strassler is way behind the times. It was known immediately upon the report by the BICEP2 team that they have no CMB detections. In fact, it was known long before their report that they would get no CMB detections.

    BICEP2 Fallacies

    Professor Pierre-Marie Robitaille: The Cosmic Microwave Background

    Professor Pierre-Marie Robitaille, ‘On the validity of Kirchhoff’s Law’

  5. Suppose later work shows both sides are right: BICEP’2’s measurement is only a 2.3 sigma signal, but there is in fact a cosmological signal there also. How do you think credit (Nobels?) will be apportioned?

  6. Gravitational waves are propagating waves of gravitational energy produced by accelerating masses – disturbing, folding or shrinking the space itself.
    Light behaves as both a particle and a wave. Polarization refers to light that is reflected or transmitted through certain media so that all vibrations are restricted to a single plane.
    So one entangled Polarization may had been delayed longer, remained in a single plane (space time) ?

  7. Latest (Fri/Sat, 30/31 May) discussion at #WSF: #BICEP2 stand by their result – no proof dust forges polarization like that! Linde more convinced (and convincing) than ever! Guth not suspicious of BICEP! Princeton now pretty much a loner in unfounded attacks! Rumor 1: Planck final result coming up in 3 weeks tops, NOT in October! Rumor 2: Planck to confirm BICEP: http://www.worldsciencefestival.com/2014/05/ripples-from-the-big-bang-listening-to-the-beginning-of-time/

  8. Thanks for all this work!

    I looked at the first paper, since the 2nd (Flauger et al) gets a lot of criticism here. The first paper seems to cherrypick data and contort data analysis (dust models, l-dependence) to arrive at a possible r=0 null hypothesis.

    I’m much less impressed with that than by the simple, consistent analysis of the various dust models of the BICEP2 collaboration. It’s not impossible that dust predicts the signal, I just don’t see that these papers contribute to that. (They do seem to find some inessential errors, which is good and even should be expected.)

    “The bottom line, for now, is clear enough: BICEP2 hasn’t made a case that overwhelmingly convinces the world’s experts. The community will therefore remain collectively undecided until a precise determination is made of the amount of polarized dust in BICEP2′s region of the sky.”

    Okay, but that assessment must come from other sources. The initial reaction, and I assume there were experts, were exactly that the results were overwhelming and showed an explicit lack of indecision (among many). And it is very difficult for laymen to assess the consensus.

    At this point, the issue turns political. Here is what a layman then can do: As long as BICEP2 don’t respond, and as long as they don’t get criticism for not doing so, they imply that there isn’t anything worthwhile to respond to.

    1. Your last sentence isn’t correct. A lack of reaction by BICEP2 may simply reflect that they are carefully looking over what they can and cannot say given what they know. Even if the criticism were accurate, there would be no reason for BICEP2 to rush out a response. You misunderstand scientific politics; it’s not like government politics, where a lack of response is itself political. Scientific politics is very different: a statement which later turns out not to be scientifically accurate is damaging, while a correct statement that comes out after three months of careful consideration is well-received. We scientists are not in a rush.

  9. What I found quite interesting is the answer M. Zaldarriaga gave to E. Silverstein’s question at the Caltech workshop: http://www.ustream.tv/recorded/47637248 (after the 01:07:59 timestamp-but both the presentation and the eschanges afterwards are worth following), namely how much uncertainty there is about modeling the dust background. Measurements are useful, once there’s a model, or template, as it’s, apparently called. So how well are such templates known, at all, so that measurements of electromagnetic spectra can eliminate the contribution of interstellar dust, in order to reduce the uncertainty in inflationary signals? Is it reasonable to state that the uncertainty can be reduced beyond 3 sigma? Beyond 5 sigma?

  10. The proliferation of BICEP2 puns may be worse than finding out the result could be false.

  11. If my memory serves right, last year when Planck’s first results came out, they did imply support for inflationary models. So it looks like that the current controversy is only about whether primordial gravitational waves are source of B-mode polarization or not. In that case neither BICEP2 nor Planck would have any problem with the inflationary model. Is that right? How strong is the argument for inflation?

    1. “The inflationary paradigm not only provides an excellent way in solving flatness and horizon problems but also generates density perturbations as seeds for large scale structure in the universe. … In fact temperature anisotropies observed by the COBE satellite in 1992 exhibit nearly scale-invariant spectra as predicted by the inflationary paradigm. Recent observations of WMAP also show strong evidence for inflation.” — Shinji Tsujikawa, “Introductory review of cosmic inflation”, 2003
      “TASI Lectures on Inflation”, Daniel Baumann, 2009

    2. Inflation implies only that gravitational waves are produced, but not that they are observably large. If we see gravitational waves from the early universe, that supports (but doesn’t quite prove) inflation; if we don’t see them, that does not disprove or even disfavor inflation.

  12. The motion energy (mass) increases with the positive pressure (gravity) at the cost of potential energy (rest mass) – at one point, converted to vacuum energy, stopping all the momentum – sudden creation of new space. Then no rest mass, no black hole, no gravitational waves ?

  13. Reblogged this on thecuriousastronomer and commented:
    More on the controversy over the BICEP2 results which claimed back in March to have discovered the B-mode polarisation due to gravitational waves in the very very early Universe. It seems others claim that BICEP2 did not correctly subtract the polarisation signal from dust in our own Milky Way.

  14. Gravity waves do not exist but a Graviton foam or froth does. The CMB anisotropies reflect the presence of this Graviton froth.Binary pulsars do not generate GWs but stir up a Graviton foam/froth.The Graviton foam obeys Planck’s distribution function.

    1. Thanks for this statement. Of course it’s wrong; graviton “froth” occurs, if it does, at vastly higher energy and shorter distances than binary pulsars could possibly generate.

      1. The largest bubble in the “froth” has an energy E=hH and a radius equal to the Hubble radius.There are 10^60 energy levels avaliable for these bubbles.Each separated by an energy E=hH.The size of the hubble is governed by the uncertainty principle.The more energetic the smaller the radius of the bubble.So a binary pulsar system can stir up the froth.The bubbles move like phonons in a solid or heat

        1. The Nexus model of quantum gravity is the only self consistent and falsifiable theory of quantum gravity surpassing the lambdaCDM model in predicting galaxy rotational curves and galactic cluster dynamics. If you want to verify this on your own use the following equation
          G’_{(k+ nk_0)\mu\nu}=\frac{8\pi G}{c^4}T_{(k)\mu\nu}+ \left(n^2-1\right)\Lambda g’_{(k_0)\mu\nu}
          where n is an integer between 1 and 10^60
          g’_{\mu\nu}= g_{\mu\nu}(\int_{-\k_n}^{\k_n} e^{ikx} dk_\mu)^2
          The n^2(\Lamda) term is the dark matter or a graviton bubble in the nth quantum state
          you also notice that at the planck state where n=10^60 the Dark matter term is 10^120 orders of magnitude greater than the Dark Energy Term.
          Also observe that when the baryonic matter energy density term is equal to the Dark energy term the Dark Matter term dominates the curvature.
          the quantized form of Hubble’s law is v=c/n. The speed v, is a constant rotational speed induced by the dark matter term in the nth quantum state.
          also notice that the space-time metric undulates at low values of n resulting in the motion of stars at galactic edges resembling horses on a merry-go-round or a roller coaster ride at a theme park.
          This undulation also accounts for the discrepancies in the lambdaCDM model for the CMB anisotropies at low values of l.

  15. “Until then, our knowledge will remain hazy.”

    Hazy, as if obscured by clouds of dust…

  16. BICEP is about proving Linde’s theory which pretty much has Multiverse as the underlying requirement. If Multiverse is proven scientifically, then BICEP is likely correct too.

    Multiverse actually has been proven experimentally, first in 2005 and 2012, from 10+ billion 1Hz gravity measurements taken by the (Canadian) superconducting gravimeter as the Earth’s most accurate instrument used for studying G, as well as mathematically (by expressing G via c on both quantum and mechanist scales, as Einstein hinted in 1930s) and multi-physically (w/o units of any universe): http:// lanl. arxiv.org/abs/physics/0608026, http:// hal. archives-ouvertes.fr/hal-00808674, http:// www. mynewsdesk.com/ba/pressreleases/as-big-bang-gets-downgraded-to-a-bang-the-first-scientific-proof-of-the-multiverse-claimed-975493

    1. This is not correct. You can have a multiverse and yet have no observably-large signal of gravitational waves. So whether the multiverse is true has no bearing on whether BICEP2 is right or wrong.

      As for the second paragraph, false.

  17. Is the gravitational wave signature in the CMB unique in that it can be clearly separated from other signals? If the foreground sources become understood will we be able to extract a reliable gravitational wave signal from data? Or is it possible that the foreground signal will overwhelm the gravitational wave signal?

    1. I don’t think that anyone knows for sure at the moment. Remember BICEP2 is only looking at a small portion of the sky. When we know how much dust polarization there is across the whole sky, then we’ll know how difficult measuring a gravitational wave signature might be.

      The other thing to keep in mind is that the gravitational wave signature from inflation might be far too small to measure, if the energy scale of inflation is relatively small. That’s always a possibility. Inflation offers the possibility of a gravitational wave signature; but that possibility is not a guarantee that it will be large enough ever to measure.

  18. The 2.3 sigma claim on BICEP frequency spectrum was based on an incorrect analysis- they did not use the correct errors, ignored the contribution of synchrotron (likely important at 100 GHz) and ignored the contribution of lensing. If it had been done correctly, the difference between the two fits (purely galactic vs. CMB) is less than a sigma.

    The BICEP’s team claim that they have a 5.9 sigma detection after fitting for the foregrounds is also based on incorrect analyses. The level of dust polarization needed to fit the data is typical of a high latitude region of the galaxy.

    The BICEP team has made an impressively deep and sensitive measurement. However, high frequency data from Planck will be needed to discover whether this is due to GW or galactic foregrounds.

    1. Could you elaborate on your 2nd paragraph? BICEP was in fact looking at a high latitude region of the galaxy, so where were they incorrect? (I’m curious if you’re pointing at something besides Flauger’s concerns.)

      1. What David means is that Planck’s new data shows that in some high-latitude regions of the galaxy, the level of dust polarization is often 10-20%. (In most [all?] of their models BICEP2 was assuming something of order 5%.) If you take that high a polarization and assume it is present in BICEP2’s region of the sky [where Planck couldn’t make a measurement, because there’s so little dust there], then (David argues, along with his co-author Flauger) then it is potentially big enough to explain the signal that BICEP2 observes, without any gravitational waves.

        However, I am still not happy with the level of clarity in the Flauger et al. paper, so I am reserving judgment on this claim for the moment.

      1. A cynical, snarky reply to Stam Nicolis’ question of why the 2.3 sigma claim was eclipsed by the 5.9 sigma. BICEP presented these findings at a press conference as >5 sigma evidence for inflation (at least that’s how I read it). I’m waiting for their next pronouncement, but currently feel they over-reached badly.

    1. They hold them all the time. Did you know coffee reverses aging? Entanglement means homeopathy works! Stephen hawking says black holes are a lie!

      1. Press conference or no, I think it would have been wise of the BICEP2 team to emphasize the weaknesses as well as the strengths of their claims. But I think what must have happened is that they convinced themselves that dust couldn’t possibly be a problem — there just wasn’t enough of it, and it couldn’t be more than about 5-10% polarized. So this left them blind to their biggest weakness, and so they wouldn’t have emphasized it anyway. In retrospect it’s easy to say that they should have said more about the possibility that their result was due to dust — but they weren’t thinking that way at the time of the announcement. Hindsight is 20-20.

  19. BICEP2 had stated in their paper quite clearly that they could only discriminate their signal from dust to 2.3 sigma-so it’s not surprising that, with the avilable data, it’s not possible to reach a definite conclusion-that’s what this figure implies.
    The issue is, whether the dust foregrounds are understood sufficiently well at all, so that planned measurements and current models can eliminate dust sufficiently. So I’m not surprised that further analysis isn’t conclusive-I’m surprised that this fact wasn’t realized immediately.

    1. Stam — I don’t agree. BICEP2 did two separate things. They showed dust could only be separated from gravitational waves **using the spectrum** at 2.3 standard deviations. But they separately argued that dust polarization was too small **in size** to contribute to their signal. It was the latter argument that was more compelling.

      Once that compelling argument is gone, however, then yes, one has to rely on the spectrum, and then the argument is weak… especially since the both of the papers I mentioned suggest that 2.3 sigma was an overestimate.

      1. Matt-of course, I agree with you. But, if the argument couldn’t be quantified so as to affect the final uncertainty, this shows that the limits of the argument were recognized from the beginning.
        And doesn’t this, also, mean that a better, quantitative, understanding of the dust foregrounds is necessary? So the question is, is such an understanding available, so, if a polarization map is published, it is known to be free of dust contributions to a better level of uncertainty-or is this not, yet, the case?

        1. I don’t think I ever understood what BICEP2 had done with their DDM1 and DDM2 Planck-data driven models until recently. I was too naive about their methods, which I thought did have a statistical interpretation as an 95% upper bound. That was incorrect. You are correct that in fact their methods did not have a clear quantitative interpretation.

          The only way to understand the dust foreground is to have measurements at many different microwave frequencies, at high angular resolution. We don’t have that yet; someday we will.

          1. Is it possible to understand *why* the argument that the dust should contribute so “little” was considered so compelling, in the first place-and how it came to sort of push aside the statement that the uncertainty couldn’t be better than 2.3 sigma?

            1. I think you’re asking the wrong question, Stam, because you’re not understanding my point.

              First, most people in the field (myself included) are not dust experts. It’s a specialized area. Moreover, the BICEP2 paper was rather terse (surprisingly so) in the discussion of dust modeling. This made it difficult for most of us to understand, at the time of the paper, exactly what they’d done.

              To the extent I did understand it, I read it as the following claim. (a) Even the most pessimistic models put the dust far below the observed signal [and I incorrectly believed the lines on the relevant plot must be 95% upper bounds, which I assumed was why there were no error bars shown, which would then imply dust was many sigma too small to affect the result]. And therefore (b) the uncertainty over dust is not a substantial contribution to the error budget for the *size* of the signal, which was stated as over 5 standard deviations (“sigmas”) away from zero. I read this as a distinct argument not connected with the attempt to separate signal from dust purely spectroscopically, which was clearly stated as 2.3 sigma.

              In short, I set the 2.3 sigma aside because I believed BICEP2 was presenting it as a *cross-check* on the main result, and not central to the stronger main result. I don’t think I was alone in that understanding; in fact I still think that was what BICEP2 was claiming. I think your understanding is that the spectroscopic argument *was* central to the main result, but I don’t think that’s what BICEP2 said.

              Of course, I did talk to experts on dust. At least one of the world’s leading experts on dust was convinced that BICEP2 had showed the effect of dust was far too small to be of any importance — consistent with my reading of what BICEP2 was arguing. Other experts were more skeptical. I couldn’t judge, so I was patient and reserved judgment, like any responsible scientist, until the dust experts had had time to think through BICEP2’s arguments.

              If I may quote from my original post on BICEP2, http://profmattstrassler.com/2014/03/17/bicep2-new-evidence-of-cosmic-inflation/ : “Talking to and listening to experts, I’d describe the mood as cautiously optimistic; some people are worried about certain weird features of the data, while others seem less concerned about them… typical when a new discovery is claimed.”

              So when you ask “why the argument that dust should contribute so little was considered so compelling“, I don’t think your premise is correct. Non-experts in dust didn’t know what to think; we deferred to the experts. Hence the rather uninformed skepticism in my original post on the matter. Some of the experts (including Spergel) were immediately suspicious. Other experts were more convinced. But certainly the community of experts never had consensus that it was compelling.

              But I think I’ve answered the question of how the argument in question came to “push aside the statement”. I believed (and I think many others believed) that there were two separate claims, the 2.3 sigma spectroscopic argument being a cross-check on the other, less precise but much more powerful, non-spectroscopic argument constraining the size of the possible dust signal. I still believe that’s what BICEP2 was arguing. And the issues that are coming up now are not that BICEP2 did the statistical analysis wrong for the non-spectroscopic argument. It’s that they made a systematic mistake, and underestimated the potential for dust.

              The claim of the second paper I’ve mentioned is that BICEP2’s non-spectroscopic argument was just plain incorrect. *IF* that’s true, then the spectroscopic argument isn’t a cross-check: it’s central. And now the 2.3 sigma is the best you can hope for, with the additional caveats in the two papers that 2.3 is an overestimate (see Spergel’s comment below.)

              1. Actually, Stam — if you read Spergel’s comment carefully, you’ll see he too views this as *two separate claims*, one spectroscopic (2.3 sigma), one non-spectroscopic (over 5 sigma.)

                1. And now I return, with egg on my face. :/ If you reread my post on BICEP2’s original presentation, http://profmattstrassler.com/2014/03/17/bicep2-new-evidence-of-cosmic-inflation/ , I in fact wrote:

                  Note that this is not a 5.2 sigma detection of inflationary gravitational waves! For that, they need enough data to show their observed data agrees in detail with the predictions of inflation. The 5.2 sigmas refers to the level of the detection of B-mode polarization that is not merely due to lensing.

                  They can only disfavor the possibility that their measurement is caused by dust or by synchroton radiation at the 2.3 sigma level, however. This may be something to watch.”

                  So apparently I forgot what I thought at the time of the original presentation, when I shared the view you are expressing.

                  My best guess as to the reason for my memory lapse is that in the days following BICEP2’s presentation, after reading more about what they were saying about dust, and talking to some dust experts who believed their arguments, I forgot my original caveat! 🙂

          2. Thanks! My reading was that they had detected a non-zero signal, with a confidence level above 5 sigma, but they could distinguish *this* signal from synchrotron background at a level of 2.2 and from dust at a level of 2.3 sigma. (The uncertainties on synchrotron and dust imply that further measurements could be expected to push matters either way: wash out the signal, or confirm it-assuming the backgrounds are understood.)

  20. On a related matter, if the 5/28 Andromeda flash had been a GRB we’d be having a much wider discussion over gravity waves. LIGO is down for upgrades as well as the VIRGO interferometer, LISA and DECIGO haven’t launched yet leaving only Germany’s GEO 600 for detection. The problem with a single source is that it should be met with not just skepticism but disbelief. False positives are common. Today we’re not ready for a gamma ray burst, we lack the tools to accurately measure one. Here is an argument for preparation posthaste, one could be headed for us right now.

    1. Robert – If the burst had been real and from the coalescence of a compact binary, LIGO&Virgo should have seen a significant number of systems even with the initial detectors. The fact that we have to wait for advanced instruments to obtain a first detection means that the rate of these events in the local group is pretty tiny. And with the first sustained full-interferometer lock occurring at LIGO Livingston this week, the upgrades are continuing apace and more or less on schedule. So no need for panic.

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