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The universe’s rate of expansion is in dispute – and we may need new physics to solve

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  • The universe’s rate of expansion is in dispute – and we may need new physics to solve

    This discovery has been in a bunch of articles from different sources, but in a nutshell there are conflicts in recent discoveries of conflicts concerning the Hubble Constant that need to be resolved involving the expansion rate of the universe.

    Source: https://theconversation.com/the-universes-rate-of-expansion-is-in-dispute-and-we-may-need-new-physics-to-solve-it-100154



    The universe’s rate of expansion is in dispute – and we may need new physics to solve it

    Cosmic showstopper

    Now it seems that this difficulty may be continuing as a result of two highly precise measurements that don’t agree with each other. Just as cosmological measurements have became so precise that the value of the Hubble constant was expected to be known once and for all, it has been found instead that things don’t make sense. Instead of one we now have two showstopping results.

    On the one side we have the new very precise measurements of the Cosmic Microwave Background – the afterglow of the Big Bang – from the Planck mission, that has measured the Hubble Constant to be about 46,200 miles per hour per million light years (or using cosmologists’ units 67.4 km/s/Mpc).

    On the other side we have new measurements of pulsating stars in local galaxies, also extremely precise, that has measured the Hubble Constant to be 50,400 miles per hour per million light years (or using cosmologists units 73.4 km/s/Mpc). These are closer to us in time.

    Both these measurements claim their result is correct and very precise. The measurements’ uncertainties are only about 300 miles per hour per million light years, so it really seems like there is a significant difference in movement. Cosmologists refer to this disagreement as “tension” between the two measurements – they are both statistically pulling results in different directions, and something has to snap.

    © Copyright Original Source

    Glendower: I can call spirits from the vasty deep.
    Hotspur: Why, so can I, or so can any man;
    But will they come when you do call for them? Shakespeare’s Henry IV, Part 1, Act III:

    go with the flow the river knows . . .

    Frank

    I do not know, therefore everything is in pencil.

  • #2
    Originally posted by shunyadragon View Post
    This discovery has been in a bunch of articles from different sources, but in a nutshell there are conflicts in recent discoveries of conflicts concerning the Hubble Constant that need to be resolved involving the expansion rate of the universe.

    Source: https://theconversation.com/the-universes-rate-of-expansion-is-in-dispute-and-we-may-need-new-physics-to-solve-it-100154



    The universe’s rate of expansion is in dispute – and we may need new physics to solve it

    Cosmic showstopper

    Now it seems that this difficulty may be continuing as a result of two highly precise measurements that don’t agree with each other. Just as cosmological measurements have became so precise that the value of the Hubble constant was expected to be known once and for all, it has been found instead that things don’t make sense. Instead of one we now have two showstopping results.

    On the one side we have the new very precise measurements of the Cosmic Microwave Background – the afterglow of the Big Bang – from the Planck mission, that has measured the Hubble Constant to be about 46,200 miles per hour per million light years (or using cosmologists’ units 67.4 km/s/Mpc).

    On the other side we have new measurements of pulsating stars in local galaxies, also extremely precise, that has measured the Hubble Constant to be 50,400 miles per hour per million light years (or using cosmologists units 73.4 km/s/Mpc). These are closer to us in time.

    Both these measurements claim their result is correct and very precise. The measurements’ uncertainties are only about 300 miles per hour per million light years, so it really seems like there is a significant difference in movement. Cosmologists refer to this disagreement as “tension” between the two measurements – they are both statistically pulling results in different directions, and something has to snap.

    © Copyright Original Source

    Seems a bit overblown. Ever since I was a young man there have been articles on varying values of H0. At that time it seemed every study produced a different value and it often was given as a range (which typically would have included both the planck results and this study's results). I guess now the expectation is that with such high accuracy results as these and planck, coupled with the understanding the expansion rate is changing, we should see a convergence of values, but maybe it's just that we still don't quite understand why we get different values from different distance scales/objects? Seems the headline should be "Well, we thought we knew how to measure the hubble 'constant' ..."

    Jim
    Last edited by oxmixmudd; 08-16-2018, 01:30 PM.
    My brethren, do not hold your faith in our glorious Lord Jesus Christ with an attitude of personal favoritism. James 2:1

    If anyone thinks himself to be religious, and yet does not  bridle his tongue but deceives his own heart, this man’s religion is worthless James 1:26

    This you know, my beloved brethren. But everyone must be quick to hear, slow to speak and slow to anger; James 1:19

    Comment


    • #3
      Originally posted by oxmixmudd View Post
      Seems a bit overblown. Ever since I was a young man there have been articles on varying values of H0. At that time it seemed every study produced a different value and it often was given as a range (which typically would have included both the planck results and this study's results). I guess now the expectation is that with such high accuracy results as these and planck, coupled with the understanding the expansion rate is changing, we should see a convergence of values, but maybe it's just that we still don't quite understand why we get different values from different distance scales/objects? Seems the headline should be "Well, we thought we knew how to measure the hubble 'constant' ..."

      Jim
      I do not consider it overblown, nor do I consider it shaking the foundation of physics and cosmology, but I do consider it a problem that needs resolution, and over time it probably will be resolved.
      Glendower: I can call spirits from the vasty deep.
      Hotspur: Why, so can I, or so can any man;
      But will they come when you do call for them? Shakespeare’s Henry IV, Part 1, Act III:

      go with the flow the river knows . . .

      Frank

      I do not know, therefore everything is in pencil.

      Comment


      • #4
        Originally posted by shunyadragon View Post
        I do not consider it overblown, nor do I consider it shaking the foundation of physics and cosmology, but I do consider it a problem that needs resolution, and over time it probably will be resolved.
        It's the 'we may even need new physics!' angle that makes it overblown (but not necessarily wrong). In the paper the author just refers to the tension between this high accuracy cepheid results and the result that derives from the Planck data. I agree with you that it is a problem worthy of research and that it needs resolution. I don't agree with the way the article sensationalizes the discrepancy between the two types of measurement.

        One thing not made clear at all is how the Plank result is used to define the expected nearby value for the Hubble constant. We know from SN Type Ia data the expansion rate was slower in the past. So if I could see cepheids far enough away, I could expect them to show a lower H0 value than the one measured in this article. And if the Planck CMB data was telling us what that value was in the past we really would not have a problem, because we already know it was slower in the past. So I have to assume that Plank value represents the expected current expansion rate, which should be close to what we would measure in nearby cepheids. But I also expect that would be derived from some theoretical extrapolation from the measured Planck data into some overarching hypothesis about how the universe would evolve from those conditions. So we have a theoretical extrapolation pitted against high accuracy measurements. And those that believe in the theory and Planck will think there is some systematic error in the parallax data, and the believers in the parallax data will think there is something amiss in the theoretical extrapolation that gives us an H0 value from the Plank data.

        The conundrum then is that to this point, no one can find a flaw in either. But even so, something must be wrong. Just like Quantum and the Theory of Relativity work really well on their respective scales, but inherently something is wrong with one and/or the other because they are - at least to this point - fundamentally incompatible theories, with neither predicting the results of the other at their respective scales.

        Jim
        My brethren, do not hold your faith in our glorious Lord Jesus Christ with an attitude of personal favoritism. James 2:1

        If anyone thinks himself to be religious, and yet does not  bridle his tongue but deceives his own heart, this man’s religion is worthless James 1:26

        This you know, my beloved brethren. But everyone must be quick to hear, slow to speak and slow to anger; James 1:19

        Comment


        • #5
          Originally posted by oxmixmudd View Post
          It's the 'we may even need new physics!' angle that makes it overblown (but not necessarily wrong). In the paper the author just refers to the tension between this high accuracy cepheid results and the result that derives from the Planck data. I agree with you that it is a problem worthy of research and that it needs resolution. I don't agree with the way the article sensationalizes the discrepancy between the two types of measurement.
          I tend to delete such editorial comments from layman articles. I can easily remember common layman articles on evolution that state; "New discovery over turns previous . . ." I, of course, consciously delete such editorial comments and go to the substance of the article.

          The conundrum then is that to this point, no one can find a flaw in either. But even so, something must be wrong. Just like Quantum and the Theory of Relativity work really well on their respective scales, but inherently something is wrong with one and/or the other because they are - at least to this point - fundamentally incompatible theories, with neither predicting the results of the other at their respective scales.

          Jim
          This is the point of the reason I cited the article.
          Glendower: I can call spirits from the vasty deep.
          Hotspur: Why, so can I, or so can any man;
          But will they come when you do call for them? Shakespeare’s Henry IV, Part 1, Act III:

          go with the flow the river knows . . .

          Frank

          I do not know, therefore everything is in pencil.

          Comment


          • #6
            Originally posted by oxmixmudd View Post
            The conundrum then is that to this point, no one can find a flaw in either. But even so, something must be wrong. Just like Quantum and the Theory of Relativity work really well on their respective scales, but inherently something is wrong with one and/or the other because they are - at least to this point - fundamentally incompatible theories, with neither predicting the results of the other at their respective scales.
            I'm going to use a compatible situation that i understand better to explain the "new physics" angle. The example is the decay of neutrons, specifically what their half life is. We have two means of measuring this: put neutrons in a magnetic container, wait a bit, and see how many are left. The second is to watch a beam of neutrons and count the protons (a decay product) that come out of it.

            The two methods produce different values, and the statistics of them are such that they only way the uncertainties in these values can overlap is if we've gotten the statistics wrong.

            Now, bad statistics are one avenue that researchers are exploring, in part by devising new ways of doing one of the measurements so that we can control uncertainties better. So far, that's only made the problem worse. So others are starting to explore the alternative: what if both are right, and the difference is caused by the different physics of the two experiments?

            In the case of these two, the different physics explanation is pretty easy to understand: if some neutrons decay by a pathway that doesn't produce a proton, it's easy to explain why the two approaches would produce different values. The problem is that we know of no other way for a neutron to decay, and there are absolutely none predicted by the Standard Model. Hence it would have to be new physics.

            I don't understand the details of the Planck measurements well enough to understand how new physics could make them systematically different from more traditional measurements of cosmic difference, but i'd assume something similar is happening there.
            "Any sufficiently advanced stupidity is indistinguishable from trolling."

            Comment


            • #7
              Originally posted by shunyadragon View Post
              I tend to delete such editorial comments from layman articles. I can easily remember common layman articles on evolution that state; "New discovery over turns previous . . ." I, of course, consciously delete such editorial comments and go to the substance of the article.



              This is the point of the reason I cited the article.
              yes - and given the quietness of Nat Sci, I actually do thank you for doing that :)

              Jim
              My brethren, do not hold your faith in our glorious Lord Jesus Christ with an attitude of personal favoritism. James 2:1

              If anyone thinks himself to be religious, and yet does not  bridle his tongue but deceives his own heart, this man’s religion is worthless James 1:26

              This you know, my beloved brethren. But everyone must be quick to hear, slow to speak and slow to anger; James 1:19

              Comment


              • #8
                Originally posted by TheLurch View Post
                I'm going to use a compatible situation that i understand better to explain the "new physics" angle. The example is the decay of neutrons, specifically what their half life is. We have two means of measuring this: put neutrons in a magnetic container, wait a bit, and see how many are left. The second is to watch a beam of neutrons and count the protons (a decay product) that come out of it.

                The two methods produce different values, and the statistics of them are such that they only way the uncertainties in these values can overlap is if we've gotten the statistics wrong.

                Now, bad statistics are one avenue that researchers are exploring, in part by devising new ways of doing one of the measurements so that we can control uncertainties better. So far, that's only made the problem worse. So others are starting to explore the alternative: what if both are right, and the difference is caused by the different physics of the two experiments?

                In the case of these two, the different physics explanation is pretty easy to understand: if some neutrons decay by a pathway that doesn't produce a proton, it's easy to explain why the two approaches would produce different values. The problem is that we know of no other way for a neutron to decay, and there are absolutely none predicted by the Standard Model. Hence it would have to be new physics.

                I don't understand the details of the Planck measurements well enough to understand how new physics could make them systematically different from more traditional measurements of cosmic difference, but i'd assume something similar is happening there.
                Thanks - good and interesting example.

                Jim
                My brethren, do not hold your faith in our glorious Lord Jesus Christ with an attitude of personal favoritism. James 2:1

                If anyone thinks himself to be religious, and yet does not  bridle his tongue but deceives his own heart, this man’s religion is worthless James 1:26

                This you know, my beloved brethren. But everyone must be quick to hear, slow to speak and slow to anger; James 1:19

                Comment


                • #9
                  We'll have to wait and see, though I expect it to be a lot more likely that this does not require new physics to explain.

                  Comment

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