BICEP, gravitational waves et al.

Reader Justin sent a link to this animated video by MinutePhysics that tries to explain what the BICEP project really revealed about the Big Bang (I say “tries” because I’m not a physicist). Do note, though, that Official Website Physicist™ Sean Carroll was an advisor on the science, so it must be right!.

One thing I took from this video (and again, readers in the know can explain it) was the statement that “this discovery marks the first confirmation that gravity is indeed a quantum mechanical phenomenon.” It was my impression that the unification of gravity and quantum mechanics was one of the great unsolve problems of physics, and I’m wondering if the BICEP results will help that project.

Note that two minutes in, the video tells you how to get a free audio book, and the selection includes one recommended by Randall Munroe, the creator of xkcd.

As for the significance beyond physics, it’s explained in yesterday’s The Far Left Side cartoon by Mike Stanfill, a strip I must check more regularly. (Stanfill always adds some explanation below his cartoons.)



  1. gbjames
    Posted March 20, 2014 at 8:18 am | Permalink


  2. Posted March 20, 2014 at 8:26 am | Permalink

    Far Left Side is almost uniformly unfunny and terrible – like a left-wing Mallard Fillmore. This, however, looks like a great improvement on their usual.

    • Kevin
      Posted March 20, 2014 at 9:07 am | Permalink

      I have never heard of it, but I thought it was hilarious.

    • Mark Joseph
      Posted March 20, 2014 at 6:10 pm | Permalink

      Remember, though, that reality has a liberal bias…

  3. Posted March 20, 2014 at 9:00 am | Permalink

    It was my impression that the unification of gravity and quantum mechanics was one of the great unsolve problems of physics, and I’m wondering if the BICEP results will help that project.

    Considering this is the first empirical measurement of quantum gravity, I’m sure everybody working on that problem plugged r=0.2 (still not sure what that means) into all their quantum gravity models and that, as a result, if nothing else, the field of candidates has already been significantly narrowed. It’s also (presumably) confirmation of the quantization of gravity, which means that everybody who had been working on solutions that didn’t quantize gravity are now going to be focussing their attention on quantized gravity, which means more attention on the problem and possibly fresh perspectives.

    It’s hard to know these things for sure, but I’m guessing that the solution to quantum gravity is now coming sooner rather than later, and that BICEP2 will be directly responsible for breaking the logjam.

    Note that a solution to quantum gravity will likely also come with a solution to dark energy and quite possibly dark matter and quite possibly cosmogenesis itself, so we may well soon have all the Big Answers to todays biggest Big Questions.

    …but, of course, there’re even more Big Questions farther over the horizon, such as supersymmetry…but the supercharged LHC when it comes back online after its supercharging will likely be powerful enough to probe that domain as well….


    • Diana MacPherson
      Posted March 20, 2014 at 9:07 am | Permalink

      Yes a grand unified theory in physics would be great if it happened in my lifetime!

      • Posted March 20, 2014 at 9:28 am | Permalink

        It very well could, especially now that we’ve got some hard data and good reason to expect more.


      • moarscienceplz
        Posted March 20, 2014 at 10:35 am | Permalink

        To heck with a GUT. I want Warp Drive, dammit!

        • Diana MacPherson
          Posted March 20, 2014 at 4:23 pm | Permalink

          I want transporters. I hate commuting.

    • Kevin
      Posted March 20, 2014 at 9:11 am | Permalink

      I could be wrong, but I thought the quantum fluctuations gave rise to the ‘jiggles’, but that does not necessarily imply ‘quantum gravity’. Although I would be hard pressed to believe that gravity is not quantized at some level. I think the data is good for constraining miscellaneous theories, in any case.

      • Posted March 20, 2014 at 9:19 am | Permalink

        Since the quantum fluctuations are of the gravitational field, that surely must imply “quantum gravity”.

        • Posted March 20, 2014 at 9:30 am | Permalink

          Exactly — this is an observation of gravity that’s been quantized. Whether or not it bears any semblance to what people expected quantum gravity to look like, assuming the BICEP2 results hold, it is, by very definition, quantum gravity. Now all that’s left is to figure out what quantum gravity actually is, since we’re looking at it, even if reality is much different from what we thought it was going to turn out to be.


          • Posted March 20, 2014 at 10:09 am | Permalink

            Aren’t you mis-using the term “quantised” here? There’s a big difference between showing that gravity is a quantum theory, subject to quantum fluctuations, and showing that is is “quantised” (= having only certain discrete allowed values [e.g. electric charge]).

            • Buzz
              Posted March 20, 2014 at 10:30 am | Permalink

              That is correct. There is not really any quantum gravity here. What has been seen is strong evidence that the early universe was full of gravitational waves. This is more or less what one would guess for any cosmological model, although it’s possible to create “designer” models in which the waves are absent. Those models are now ruled out, and the approximate measurement of the amount of gravitational radiation that must have been present is a big deal.

              To spin this as support for quantum gravity (which, mathematically, has to exist in some form or another), one has to take this as confirmation of a specific kind of inflationary model, in which the gravitational wave production mechanism is quantum mechanical. Since what is actually being measured is the influence of the primordial gravitational radiation on the state of the universe at much later times (when it cooled enough for primordial plasma to become neutral), this is something of an overstatement. While the measurement is evidence in favor of those kinds of inflationary models, it is hardly a slam dunk.

              • Torbjörn Larsson, OM
                Posted March 20, 2014 at 3:53 pm | Permalink

                I think the secret sauce is that it is reputedly hard to make these fluctuations classically in inflation models.

        • Kevin
          Posted March 20, 2014 at 12:52 pm | Permalink

          But is it not possible that the gravitational field is responding to the effects of quantum fluctuations or incipient particles/fields which would not necessarily imply quantum gravity? I really do not know, but distinguishing classical/quantum is not straightforward.

          There are many aspects of classical-quantum connections which make me think quantum gravity is not necessarily implied from BICEP2 (maybe BICEP2+theory).

          Hanbury Brown and Twiss effect is purely classical, but depends on whether fermions or bosons are involved. Aharonov–Bohm effect is quantum mechanical, but can be explained with classically described field (of course, those fields, I think, can be quantized). Berry phase (geometric phase) is both classical/quantum. And Quantum Zeno effect is a disruption of a quantum system by means of a repeated classical (decoherence) process.

    • Marella
      Posted March 20, 2014 at 4:07 pm | Permalink

      “As an initial result, we are interested in [the strength of the inflationary B-modes], which is given by a parameter known simply as r. The latest rumors say that a value for r has been measured by the BICEP2 observatory in Antarctica … Versions of the rumor say that the answer is r = 0.2. This is somewhat bigger than expected and could be as good as a 3 or 4-sigma signal because the sensitivity of BICEP2 was estimated at r = 0.06.”

      r is the strength of the inflationary B-modes. All clear now? Good. 😉

    • Diane G.
      Posted March 20, 2014 at 10:42 pm | Permalink

      “…so we may well soon have all the Big Answers to todays biggest Big Questions.”

      There’ll still be abiogenesis.

  4. Posted March 20, 2014 at 9:24 am | Permalink

    The most interesting thing to me (and I think to other atheists) is that this boost for inflation’s credibility is also a boost for the credibility of multiverses. I’m surprised there has been so little discussion about this aspect. Linde and Guth (two of the main originators and developers of inflation) both consider multiverses to be a nearly-necessary consequence of the line of thinking that they took when they arrived at the inflation theory.

    This, of course, has enormous relevance to the fine-tuning issue (which I don’t think can be completely argued away as Stenger does).

    And the fact that we can now think about detecting signals so close to this universe’s creation (something nobody would have expected thirty years ago) raises the hope that we might eventually be able to pull the evidential cloak back even further, to detect some subtle trace of other universes.

    • Torbjörn Larsson, OM
      Posted March 20, 2014 at 4:25 pm | Permalink

      Linde, Guth, Weinberg, Susskind, Arkhani-Hamed, Tegmark. Some well respected names, maybe Bousso can be included here.

      But, I gather, they are not the majority among cosmologists. and here is a recent back-and-forth on the subject.

      “You might be thinking: “OK, that’s a toy-toy model about how a multiverse might come from an inflationary model. Cool. But are there any non-toy models?”

      As far as I’m aware, no. And this is where I definitely agree with Peter that, although it is certainly possible to generate a multiverse, it definitely isn’t inevitable. In fact, if anyone reading this does know of any full models where a multiverse is generated, with a set of vacua with different energies, please let me know (even if it’s just a complete toy model).”

      “There are some (perhaps even many) scientists who hate the idea of a multiverse and demand that multiverses are stricken from science for being “unfalsifiable” or “unpredictive” (because we can’t ever access the other Big Bangs).

      I don’t understand this mentality.

      Forgetting about whether a multiverse is “scientific” or not, what if it is true? What if we do live in a universe that, it just so happens, is part of a multiverse? Would we not want whatever method we use to try to learn about our existence to be able to deal with it? If we want “science” to be something that examines reality, then (if we are in a multiverse) should it not be able to deal with a multiverse? We might not be able to directly measure other Big Bangs, but we can infer their probable existence by measuring other things.”

      Also the comments, where Hotchkiss goes into “catastrophic boundaries”.*

      “I would totally agree that at the moment the multiverse is just a highly speculative idea, rather than a fully-fledged model, however I don’t think that means the idea is “not scientific” or “not testable”. Whether it is scientific is just semantics, but it definitely is testable.”

      To sum up, this may be a boost for credibility. But multiverses starts out from the gutter. :-/ And even a sober evaluation gets it as “a highly speculative idea, rather than a fully-fledged model”.

      * [I think he is referring to the fact that SM vacuum is quasistable at nearly 3 sigma, even more so with the new LHC-Tevatron consolidated top quark mass value, I think. It is perhaps pushed there for the same reason that Weinbergs anthropic cosmological constant wants to be at Planck energies naturally, but just isn’t where we live.

      With the GUT scale inflation that BICEP2 may usher in, and possibly an axion family for GUT scale inflation, dark matter and matter/antimatter, there may be a particle desert between SM and GUT, and no support for new physics there. Purely speculative from me of course, but an illustration of the possible need for inflationary multiverses.]

    • Torbjörn Larsson, OM
      Posted March 20, 2014 at 4:31 pm | Permalink

      HTML fail. Another try:

      Here and here is a recent back-and-forth on the subject.

  5. Adrian Burd
    Posted March 20, 2014 at 9:27 am | Permalink

    “this discovery marks the first confirmation that gravity is indeed a quantum mechanical phenomenon.”

    OK, not to put a damper on things, but just hold onto your horses guys. IF it turns out that these measurements are indeed of the gravitational wave imprint on the microwave background radiation and that those gravitational waves are indeed a result of inflation (or some other process from the early universe), then the above statement is indeed correct.

    These are incredibly difficult measurements to make, and there remains uncertainty as to whether or not the interpretation of these observations is indeed correct. For a level-headed look, visit

    (Disclaimer: Peter and I did our D.Phil.s at the same time under the same supervisor)

    So we will have to wait to really be certain about this.

    • Jesper Both Pedersen
      Posted March 20, 2014 at 9:38 am | Permalink

      So no graviton orgies just yet?

      • George
        Posted March 20, 2014 at 9:47 am | Permalink

        That’s good. I was having a hard time figuring out what to wear to my first GO.

        • Jesper Both Pedersen
          Posted March 20, 2014 at 10:01 am | Permalink

          I still haven’t settled on the tilt of my toga, but the fabric feels groovy.

        • Timothy Hughbanks
          Posted March 20, 2014 at 12:35 pm | Permalink

          A guy named George, of all names, shouldn’t need to be reminded of what it means to become an orgy guy.

          • Diana MacPherson
            Posted March 20, 2014 at 4:40 pm | Permalink

            Ha ha! Seinfeld — is there ever something it doesn’t address? 🙂

    • Posted March 20, 2014 at 9:41 am | Permalink

      Caution is, indeed, called for, especially in the early days after the announcement of a discovery and before independent confirmation. At the same time, all the criticisms I’ve seen have been ones that I’m pretty sure the BICEP2 team would already have considered in the couple years since they finished data collection and started their analysis, and not only does the team have a first-class reputation but they know that that reputation is on the line.

      I think prudence at this point suggests enough of a tentative conclusion that they’re correct and operating on that assumption unless evidence surfaces to indicate an error — except, of course, for those in a position to actually look for said evidence; they should be going at the study mercilessly and at full tilt.


    • George
      Posted March 20, 2014 at 9:50 am | Permalink

      This was written and posted on Monday.
      “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. I’m disturbed that the media is declaring victory before the scientific community is ready to. That didn’t happen with the Higgs discovery, where the media was, wisely, far more patient.”

      Indeed, caution and waiting for confirmation is required. But being premature is fun sometimes.

    • Posted March 20, 2014 at 10:11 am | Permalink

      I certainly agree we should be cautious here, especially considering there is a possible conflict with other results. But it seems to me lots of the criticism of the discovery is a bit disingenuous. Some people say such a big r (=0.2) is unexpected and troubling. But if you look at earlier papers on inflation, written by opponents of the theory, these papers actually predict this exact value of r under inflation. See for example Khoury, Steinhardt, Kurok 2003:
      These guys are now proponents of a cyclic theory instead of inflation. That theory predicts r is essentially zero. So way back in 2003 this week’s result was already predicted under inflation, BY THE OPPONENTS OF THE THEORY!

      Furthermore, the authors of this week’s discovery say they have additional confirmatory data from a new experiment which is yet to be published. Of course we have to wait for it before we judge. I am cautiously optimistic.

    • Torbjörn Larsson, OM
      Posted March 20, 2014 at 5:28 pm | Permalink

      I’m not qualified to discuss the statistics problems. (Haven’t done a jackknife.)

      But I note that Strassler added on this on his post that you took the lensing modes highlight from:

      “However, this point was addressed by the BICEP2 folks in their presentation. Their view is that (1) the high data points are not very statistically significantly high, and (2) with new data that they haven’t released from their third-generation experiment, they don’t see the same effect. So this is presumably what gives them confidence that the excess is a temporary, statistical fluke that will go away when they have more data.”

      The BICEP2 folks do say somewhere, in the paper or at the presser, that they have correlated all _three_ instruments.

      So I’m not so concerned about the measurements as of yet. They did a lot to hunt down systematics and eliminate them, it seems to me. And some of the experts looks impressed enough, for now. (At the presentation; Tegmark in Scientific American.)

      But what about the analysis?

      Someone, I forgot who, found this Hail Mary on arxiv. Interestingly IMHO, even if they posted this after the rumors started and they have adjusted down their estimate accordingly [cf ], they do see a “hint” in Planck and WMAP data at roughly the correct tensor-to-scalar ratio years before this.

      That picked me up considerably. (Note that they use a non-canonical analysis of the CMB. But it doesn’t seem to change much else.)

  6. George
    Posted March 20, 2014 at 9:42 am | Permalink

    The biggest and most important news about the BTCEP2 experiment – from the Christian Post –
    “Big Bang ‘Gravity Wave’ Discovery Supports Biblical Creation, Say Old Earth Creationists”

    One of my favorite comments –
    “Rather than having a pointless, futile debate between Ken Ham and Bill Nye, someone needs to host a debate between “Young Earth” creationists and “Old Earth” creationists. Now THAT could be highly entertaining.”

    I agree that would be entertaining – in a very warped, surreal way.

    Great thing about religion – it can take credit for anything. Even things it once opposed.

    • Diana MacPherson
      Posted March 20, 2014 at 9:47 am | Permalink

      If there was a beginning there had to be a beginner. Good grief!

      • Posted March 20, 2014 at 9:49 am | Permalink

        God damn Aristotle to Hell for infesting so many people with this ludicrous bullshit about agency…can we please grow out of that primitive superstition? Please?


        • darrelle
          Posted March 20, 2014 at 10:10 am | Permalink

          For some reason I suddenly can’t stop thinking about Bush Jr. stating authoritatively, “I am the Decider.”

          • Diana MacPherson
            Posted March 20, 2014 at 4:21 pm | Permalink

            Ha! How did I not have that memory triggered? I must’ve hid it deep in my subconsciousness out of embarrassment for Bush. Damn empathy!

        • Diana MacPherson
          Posted March 20, 2014 at 4:19 pm | Permalink

          Aristotle should have stuck to his handbooks for comedy & tragedy. We’ve lost the book of comedy but his description of good tragedy influenced Shakespeare (even if English professors misunderstand what hamartia is).

    • George
      Posted March 20, 2014 at 10:15 am | Permalink

      Why did I type BTCEP2 instead of BICEP2? The I and the T have y and u between them on a QWERTY keyboard. Brain not working well today.

      • Diana MacPherson
        Posted March 20, 2014 at 4:22 pm | Permalink

        Don’t worry – after a long day and a migraine, I called “BICEP2” “ELBOW”. 😀

  7. Posted March 20, 2014 at 9:50 am | Permalink

    On a discussion about how a sense of morality evolves, there is of course this (recent?) animated presentation with Steven Pinker in Pharyngula: I Like This Message .

    • Posted March 20, 2014 at 12:33 pm | Permalink

      Sorry, meant to comment in a different post about your upcoming talks. Must be a wormhole here….

  8. NewEnglandBob
    Posted March 20, 2014 at 10:30 am | Permalink

    Physicist Ethan Siegel has a couple of good posts at

    “All about Cosmic Inflation”

    “Evidence of the Universe From Before the Big Bang?”

  9. Andrew van der Merwe
    Posted March 20, 2014 at 11:48 am | Permalink

    I’d like to ask a question that has been burning a hole in my head for some time and which was revived when I read the Guardian article which speaks of astronomical “inflation.” I came to this question a long time ago when reading about the square cube law and the literally incredible sizes of some creatures such as the Brachiosaurus and the Meganeura. The question that immediately came to mind was simply how do we know the fossils are still the same size as the creatures from which they were formed? Is it not possible that the universe, expanding as it is on the astronomical level, is not also expanding on smaller levels, such as the molecular or atomic? Is it not possible that everything has gotten bigger while mass has remained constant? This would explain why the fossils leave impressions of creatures which seem too big to move their own mass.

    Please accept my apologies if this is a stupid question. I am a calligrapher, not a physicist. And either way, feel free to shred.

    • Torbjörn Larsson, OM
      Posted March 20, 2014 at 5:54 pm | Permalink

      First, biologists are certain these animals could move their mass.

      (Amusingly, according to some paleontologist blogs, they are less certain how they, eh, humped. Or do you say h**d?

      Even if they were quite limber, compare with today’s birds, it would have been awkward.)

      Second, let us look at the scales involved. Spacetime expansion is minute locally. Even today, as we have entered yet another exponential expansion phase (due to dark energy), a length increases ~ 10^-10/year.

      So _if_ a dinosaur would have expanded with the universe, it would have lengthened with 10^-2 parts over 100 million years (10^8 years). Or 0.3 meters for the 30 meter long ones.

      Third, nothing material expands as the universe expands. Ordinary matter is hold together (or not) by chemical bonds. In essence electromagnetic forces. Now, a hand held permanent magnet should convince you that it is far stronger than the gravitation of the much bigger Earth: it can pick up an iron nail against gravity.

      Since the Earth is bending spacetime so it isn’t as flat as between stars where space expands, we can realize that material bodies easily resist the expansion.*

      *Expansion can be seen over large enough distances.

      For example, it is believed and I think even measured that the local group of galaxies is slowly going apart despite their mutual gravitation. In the far future, our observable universe will only contain the Milky Way.

      And light gets cosmologically redshifted. In fact, the microwaves that BICEP2 looked at started out as thermal radiation at ~ 3000 K or half the temperature of the Sun surface.

      Approximately mostly red light in other words, now stretched with a factor ~ 1000 in 14 billion years.

      • Torbjörn Larsson, OM
        Posted March 20, 2014 at 6:00 pm | Permalink

        *Held* together.

        And I was clumsy on the Earth vs interstellar space issue. My apologies!

        I meant that the latter has a much weaker stretch than the pull that Earth manages.

        We can see from that it is taken as roughly flat in Einstein’s theory of gravity (general relativity) as in not bending light rays one way or the other.

        While passing Earth bends light rays more.

      • Torbjörn Larsson, OM
        Posted March 20, 2014 at 6:22 pm | Permalink

        In retrospect we don’t need the magnet. It is enough that our bodies doesn’t get squished by Earth gravity to realize solid state materials are stronger.

        Also, I get second thoughts on the Local Group (of galaxies). I forget if the majority of astronomers claims it will hold together. It is an arguable point.

        But eventually, for large enough scales, systems of galaxies will come apart over 100’s or 1000’s of billions of years. Large clusters will do this for certain.

      • Andrew van der Merwe
        Posted March 21, 2014 at 1:47 am | Permalink

        Cool, thanks for giving my question the time of day!

        I got the impression from reading up about the problem of the mass of animals like the Brachiosaurus and the Meganeura that it wasn’t certain and that all the explanations begin with the assumption that the fossils provide an accurate record. After that it’s a matter of jumping through hoops to explain. (They had to have lived up to their necks in water, there had to have been higher oxygen levels, etc.)

        Re the strength of chemical bonds vs that of gravity, I always thought the bonds that hold atoms together were just as strong as the forces that kept them from collapsing, so a kind of balance exists and I wonder what’s involved in keeping that balance.

        I hadn’t thought of trying to work out the relative scales involved. Yes, 0.3m over 100 mil years doesn’t seem significant, though I do begin to wonder about 200 mil years which would take us back to the early Jurasic.

        I dunno, I’m not convinced that the question has no worth, though I also know that I’m not likely to understand the answer either way! I mean, I even have difficulty understanding what you’re saying about redshift. I know what it is but don’t get the implications for my question (sorry).

  10. Posted March 20, 2014 at 11:53 am | Permalink

    I wish I knew how to slow down the video. My brain couldn’t keep up with the narrator!

    • Diana MacPherson
      Posted March 20, 2014 at 4:36 pm | Permalink

      Me too. They shouldn’t have made it so fast.

  11. Torbjörn Larsson, OM
    Posted March 20, 2014 at 3:35 pm | Permalink

    Yes, it is the first confirmation (if it holds up) of the quantum nature of gravitation. The reason is, as I understand it, that these primordial gravitational waves are almost certainly caused by quantum fluctuations in gravity during the process of inflation. It is claimed to much harder (but I think still doable) to get these from classical fluctuations.

    This is why this unexpectedly easily seen signature of inflation is considered “the smoking gun”. It is the last major prediction, but it combines with an earlier one that is also somewhat difficult to get out of anything else than inflation.

    The latter is the spectral “tilt” of the primordial inflaton fluctuations, also of quantum nature, that later seeded matter clumping and ultimately galaxies. If there is anything I think the movie fubbed, it is the idea that these finds reach further back than the earlier finds. As far as I know they do not, both kind of fluctuations happens under the inflation phase. It is a confusion with the recognition that this “smoking gun” likely clinches the case for inflation immediately.

    Layman speculation:

    Will BICEP help with quantum gravity? Likely, and the rush that will get going to get better data will certainly do that.

    Because everything else alike, there is a tie between inflation and quantum gravity. Max Tegmark [also a Swede] is a cosmologist that has gone on record to note that the BICEP2 result, when adjusted for the still poorly understood galactic dust, gets the first data smack in the middle of Linde’s simplest model (a quadratic potential) for chaotic inflation.

    Chaotic inflation in turn demands that the inflaton field goes “trans-Planckian”.* Now, I understand this poorly. Energies can’t go above Planck energies (or you get a black hole). But other quantities can go so in Planck units, which I take it means they are “trans-Planckian”. This used to get theorists uncomfortable, but I think they now have found out that string/M theory can handle this. (E.g. “axion monodromy”.**) And if string/M theory gets a push, so will its handling of quantum gravity.

    Note that this handle on quantum gravity is different from the handle that the polarization gets us on primordial gravitational waves. I think.

    They latter are sub-Planckian (generated at ~ 1/1000 of Planck energy densities). And we know how to quantize gravity at such low energy densities that spacetime is approximately flat as it should be then. A “simple” quantization of the gravity Lagrangian will do. [Ref: theoretical physicist Distler’s blog has an article on that.]

    But if string/M theory gets involved, hopefully the goal of understanding the full quantization att all relevant energies (up to Planck scale) will get closer.

    * And when it does that, you get a multiverse. With a tie in to string theory, if that is what chaotic inflation is based on, you get an anthropic looking varying multiverse.

    ** Which should be good. As I mentioned yesterday, axions are also involved in theories of dark matter and matter/anti-matter symmetry breaking. Possibly open up several fields at once.

  12. stephen
    Posted March 20, 2014 at 7:32 pm | Permalink

    Since Jerry has asked for corrections-this is a bit nit-picky-I submit that the “et al.” (and other people) in the title ought to be an “et cet.”(and other things).

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