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The Big Bang's Last Great Prediction 80

StartsWithABang (3485481) writes "Even with the add-ons of dark matter, dark energy and inflation, the Big Bang still thrives as the most successful scientific model of the Universe ever constructed. It not only accounting for phenomena like the abundance of the light elements, the cosmic microwave background, and the Universe's large-scale structure, but it's led to observable predictions about their details that have since been verified. But there's one thing the Big Bang has generically predicted that we haven't been able to test: a cosmic background of low-energy, relic neutrinos."
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The Big Bang's Last Great Prediction

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  • by Anonymous Coward on Friday May 23, 2014 @03:18AM (#47072639)

    We must collect the low-energy neutrinos before the neo-Nazis find them!

  • by Anonymous Coward

    The humble banana disproves this all.

  • by nemasu ( 1766860 ) on Friday May 23, 2014 @03:54AM (#47072715)
    I just found this out a couple weeks ago, and it blew my mind, the big bang theory actually does not explain things we can actually observe right now.
    For instance, the Hercules–Corona Borealis Great Wall [wikipedia.org]
  • IANA astro-physicist - but something bothers me about the big bang theory (or at least what I know about it). Why just one? Why aren't we able to detect other big bangs elsewhere? And another thing - we theorise based on what we are able to measure and observe. While we seem to have a theory that fits the data available, surely it is quite possible that our data are just unique to our locality. Seems like we are looking into someone's CA backyard and trying to say something about volcanic action in Iceland.

    • Re:Bothered (Score:4, Funny)

      by u38cg ( 607297 ) <calum@callingthetune.co.uk> on Friday May 23, 2014 @04:49AM (#47072841) Homepage
      Well, when you create a theory of the universe's creation, you should probably take a hint from the name "universe" that there will be just one starting point...
    • by gl4ss ( 559668 )

      well if you could somehow transport yourself to outside of this universe you might be able to observe the other big bangs.

      hoooowever there's some significant problems with doing that. some people believe that if you jump from a bridge into concrete you get outside though(they base this on a lucid revelation given to someone else than them).

      really though you don't need to be an astrophysicist to understand the basis for why your question sounds very misinformed. volcanic action in iceland is observable from

    • Re:Bothered (Score:5, Interesting)

      by Sockatume ( 732728 ) on Friday May 23, 2014 @05:14AM (#47072875)

      That's a legitimate question, and in fact cosmologists are curious about the idea of whether the big bang is a unique event or something that can happen spontaneously. The hope is that advanced physics will provide some answers.

      As for the "locality" issue: cosmologists address issues related to the entire observable universe. Speculations on regions that are unobservable aren't really a topic for scientific investigation, except where a good model implies certain (untestable) things about unobservable areas.

    • Re:Bothered (Score:4, Interesting)

      by mbone ( 558574 ) on Friday May 23, 2014 @08:01AM (#47073265)

      In "eternal inflation," inflation is seen as something like the natural state of the universe, with little nodes from time to time budding off of the inflationary stream, and forming universes like our own, with inflation continuing elsewhere (from our standpoint, very very far away, much beyond any distance we could reach, even if we traveled at the speed of light). In such theories, the big bang is not the time of the birth of the universe, it is the time of the cession of inflation here, in our part of this bigger universe. This is one type of what Max Tegmark calls a Level I Multiverse (as there would be other "big bangs" elsewhere).

      It may be that the recent detection of cosmic acceleration (aka "dark energy") indicates that our universe may (if the acceleration itself starts to accelerate into something like a "big rip") return to this natural state of inflation in due course, and that might be the typical fate of "normal" universes like ours.

    • I was under the impression that the big bang needed conditions that would no longer exist in our post-bang universe (absence of time or something...), which would preclude further big bangs in our light cone. Although presumably they could still happen "outside" the universe?

  • Neutrino temperature (Score:5, Interesting)

    by Framboise ( 521772 ) on Friday May 23, 2014 @05:09AM (#47072873)

    The orginal article keeps quoting the temperature of 1.96K as the neutrino background temperature, as found in most textbooks on the topic. This is a relic of the time people were assuming massless neutrinos. The confusion is maintained by people using the temperature as a synonym of energy. Actually the non-zero rest mass energy must be subtracted, providing the real kinetic energy of these particles (moving now at 100-1000 km/s) that would be exchanged with a super large thermometer (in view of the tiny interaction cross section). The effective neutrino temperature would then be measured in the milliKelvin range.


  • Not quite (Score:5, Interesting)

    by mbone ( 558574 ) on Friday May 23, 2014 @07:49AM (#47073221)

    ...the only interaction they can conceivably have with normal matter is via a nuclear recoil.

    No, not quite. These neutrinos also interact gravitationally with ordinary matter, which, of course, the author knows, but just doesn't think of. That introduces two possible means of detecting them, either gravitationally [arxiv.org], or by using the Sun or other bodies to focus them [arxiv.org] on a detector, thereby greatly amplifying their signal.

    • The thing is gravitational interactions are so minute as to be useless (for now) for detecting individual neutrinos in a laboratory environment - the sort of situation which lets you conclusively state the things actually exist and aren't just a flawed theoretical construct used to help explain things we see halfway across the observable universe.

      The focussing thing sounds like it has promise though, though I wonder just how much good focussing something so far beneath our current detection thresholds can d

  • by Lumpy ( 12016 ) on Friday May 23, 2014 @07:54AM (#47073243) Homepage

    Will Sheldon finally find a way to communicate with Penny?

  • If quantum fluctuations created the big bang, than what created the quantum fluctuations ?
    • They are, have been, and ever shall be.

      We know that today various so-called "virtual particles" spontaneously pop into existence for a brief moment before annihilating with the antiparticle that spawned along with them - the theory stands up and we can measure their effects in the lab. And there's no reason to assume the same thing hasn't been happening throughout eternity.

      And I mean actual eternity - not just the paltry 14 billion years since the big bang. For all eternity virtual particles could have be

    • by sjames ( 1099 )

      It was probably turtles.

  • Come on, DICE: If you're going to troll us with articles, at least try to make it a bit more subtle. This one basically reads as "Evolution is best science EVARRRR!!"

    It not only accounting for phenomena

    Glad to see the editors we know and love are still living up to the high standards we set for them, too.

  • That was really lovely, and thank you for posting it.

    You assert that one problem with detection is the difficulty of accelerating entire neutrino detectors to GeV energy scales. I'm not sure that I agree. Muons, as we know, decay into electrons and two kinds of neutrino/antineutrino. Electrons moving at GeV scales have more than enough energy to be transformed into muons in the inverse reaction -- if they happen to hit an electron antineutrino -- or more properly, they have a chance to be transformed into a W- boson which can then decay into several things -- lepton/neutrino pairs or quark pairs, one of which produces muons

    Muons are easy to detect. Electrons with "suddenly" shifted energy are also easy to detect (another possible outcome). Finally, quark-antiquark "jets" are easy to detect.

    At the densities of thermal neutrinos asserted, it seems reasonably probable (without, admittedly, doing the computation) that GeV scale electrons will encounter free neutrinos and undergo the inverse reaction and produce muons along a freely moving beam track and indeed that places like SLAC and the Duke FEL would be producing a small but detectable flux of muons all along the straight legs of their beams that would then either exit sideways (where they could be detected lots of ways) or continue along the collision frame of reference and be moderately separable at the next bending magnet. Yes, there would likely be some auxiliary production near the actual beam from electron collisions with beam pipe metal outside of the beam envelope, but one would expect to be able to put a vacuum pipe along the frame of reference of the collision a kilometer long or thereabouts PAST a a bending magnet (at the right angle) at the end of a long straight leg and run it into a detector, which would then detect all/mostly muons produced by neutrino scattering. Or so it seems.

    Is this wrong?


    • I think you are overestimating the scattering cross section of even GeV neutrinos. An electron neutrino with 10 GeV in the rest frame of an electron has a scattering cross section of about 2e-44 m^2. There are about 112 electron neutrinos per cm^3, so the (lab frame) scattering rate is about 2e-44 m^2 * c *112/cm^3 = 6.7e-28/s per electron. The number of protons per beam in LHC is about 1e14. Assuming the number of electrons per beam in SLAC etc. is roughly the same, we get about 1e-13/s scatterings total i

      • Thanks, you are probably right -- as I said, I wasn't doing the math, but was just thinking that an accelerated beam IS a rapidly moving detector. I was also assuming that it was the lack of collision frame energy in the huge neutrino detectors that was the limiting factor in detecting thermal neutrinos -- to create a W boson requires order of 100 GeV, and of course this just isn't available (outside of Heisenberg uncertainty and extremely suppressed virtual processes) which mutually thermal atoms and neut

        • Yes, the accelerated beam is a rapidly moving detector. My point is that it is a rapidly moving detector with a woefully tiny volume. I'm no expert on this - I used this page [cupp.oulu.fi] for neutrino cross sections. Both inelastic and elastic scattering seems to be proportional to collision energy.

          Neutrinos of several PeV/c^2 are regularly observed in neutrino observatories. At these energies, the Earth is able to act as a somewhat effective neutrino shield, resulting in a significant deficiency in high-enery (>60 T [arxiv.org]

          • Interesting article. Things really do get complicated at those energy scales...:-)

            They're using Cerenkov detectors, though, for very very high energy events. I wonder how sensitive they are to muons with much lower energies. The scales on the figures in the article, for example, don't actually go down to 100 GeV -- the left hand edge (log scale) appears to be 1 TeV. But the cross sections are indeed pretty small and it is difficult to get rates to rise above the background cosmic ray muon flux (which I

            • The scales on the figures in the article, for example, don't actually go down to 100 GeV -- the left hand edge (log scale) appears to be 1 TeV.

              Sorry, my third link was to the wrong article. It should have been this one [arxiv.org]. That's the one that covers the whole energy range, and which shows the magnitude and location of the W-boson resonance.

              SLAC is apparently capable of generating 1/2 an ampere of beam current. That's basically 10^19 electrons/second, which knocks five orders of magnitude off your estimate of 1 event per 300000 years to one per 3 years.

              Wow, I was off by a lot! I don't know how noisy environments accelerators are, but I think one would need many times more events per year to be able to detect this. It would be really nice.. But I'm skeptical.

              That seems as though it is low enough that IF there were any sort of actual resonance, it might knock another order of magnitude off and get one at least several events per year, maybe more.

              From the figure on page 3 in the article, it seems like the W resonance is at 6 PeV/c^2 for a stationary ne

              • Unless I've missed something crucial here. But perhaps we'll have a breaktrough in accelerator technology that will let us reach these levels at some point. If we hit the resonance, the scattering rate will be of the order 1e-31, 13 orders of magnitude higher than what I used in my back-of-the-envelope calculation. But we aren't likely to hit those energies soon, I think.

                Oops (blush). I haven't done relativistic kinematics for a very long while either, but I forgot about momentum conservation altogether.

          • Oops, I mistakenly used the same link twice. The last link was supposed to be this:
            http://arxiv.org/pdf/1305.7513v1 [arxiv.org]
            It is well worth a look through.

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