Our universe could be twice as old as current estimates, according to a new study that challenges the dominant cosmological model and sheds new light on the so-called "impossible early galaxy problem."

New research puts age of universe at 26.7 billion years, nearly twice as old as previously believed::Our universe could be twice as old as current estimates, according to a new study that challenges the dominant cosmological model and sheds new light on the so-called “impossible early galaxy problem.”

  • moridinbg@lemmy.worldEnglish
    6·
    1 year ago

    Are there any constants that we actually know to have varied along the lifetime of the universe?

    • h34d@feddit.deEnglish
      2·
      1 year ago

      According to my understanding, yes. For example, it is usually assumed that there was a period of time shortly after inflation when matter was in a quark-gluon plasma, which would imply a larger strong coupling than today, since a small strong coupling is associated to confinement. There was also the electroweak-epoch, during which the electromagnetic and weak interactions were unified, and the corresponding gauge bosons were massless. The masses of the W and Z bosons can thus also be regarded as time-varying, as well as the electron charge. However, it should be noted that these changes are not all that significant on the cosmological scales under investigation here (e.g. the quark epoch ended at about 10-6 seconds after the big bang, which is much much less than the age of the universe, and it’s assumed that it still took quite a while before the first stars formed). A time-varying cosmological constant could potentially be much more relevant (and some quantum gravity theories even predict it), and I’ve heard some people suggesting it as a potential solution for the H0 tension. However, I unfortunately can’t access the paper and assess what precisely the author did there, and whether it is in any way similar to what I just mentioned.

      • jorge@sopuli.xyzEnglish
        1·
        1 year ago

        What you’re talking about is the energy dependence of the coupling constants, which is a phenomenon that is very well understood theoretically, and also checked in experiments. The early universe was much hotter, and thus particles had much more kinetic energy and “felt” slightly different coupling constants. The neat thing is that, since this is a purely energy-dependent effect, we can recreate the conditions of the early universe: the collisions at LHC have an energy of the order of 1 TeV, which corresponds to a temperature of 1016K, the temperature 10-12 s after the Big Bang. Anything after the first 10-12 s we can directly recreate, and from 10-12 s to about 10-30 s-ish we can more or less reliably extrapolate. And of course this is all included in the standard Lambda-CMD cosmology.

        Although the article is behind a paywall (which is somewhat strange in cosmology, but I digress), you can check other articles by the same author that also use the “varying constants” framework, for example https://arxiv.org/abs/2201.11667. His framework is that the speed of light c, the Planck constant h, the Boltzmann constant k and the Gravitational constant G depend directly on time, or to be more precise, on the expansion factor of the universe. There are two big differences with respect to what you were saying:

        • c, h and k are not coupling constants, and therefore they don’t receive any energy-dependent corrections. In fact, you could think of these constants as “conversion factors” between units: c converts space-time coordinates in seconds to space-time coordinates in meters, k converts kinetic energy in Joules (or electronvolts) to kinetic energy in Kelvin, and h converts angular momentum or action measured in quanta to angular momentum or action measured in J·s (or eV·s). Honestly it doesn’t make much sense to me that these constants could change (what does it means, in physical terms), that they could change in a correlated way, or that they could change in a correlated way to one, and only one, coupling constant, G.
        • Since this is a time-dependent change, there is no real way to significantly test the hypothesis (unlike the energy-dependent changes). We can not go back in time, or to wait to a different time when these constants would be different. He actually proposes to study how the experimental determinations of these constants in the last 10-20 years, which sounds very wild, as those tiny differences are very susceptible, by definition, to experimental uncertainties, and they are not very suitable for controlled tests.
    • Contramuffin@lemmy.worldEnglish
      2·
      1 year ago

      Somewhat. Based on my understanding of current astronomy news (I’m not an astronomer, just interested in the field) it’s not proven, but it’s not entirely disproven either. For instance, my understanding is that the Hubble constant (rate of expansion of the universe) is different if measured with the Cosmic Microwave Background (newer universe) compared to measuring redshirt of stars (older universe). Of course, it could be that one of the measurements made an assumption that’s not true, but i don’t think it’s out of the question that the false assumption ends up being that the constant stays the same over time…

      Take what I say with a grain of salt, though. Hopefully an actual astronomer can pitch in

    • rhokwar@lemmy.worldEnglish
      42·
      1 year ago

      I don’t know if this counts as a constant, but I read that time moved something like 5 times slower in the early years of the universe.

      • vimdiesel@lemmy.worldEnglish
        5·
        1 year ago

        It didn’t as time is relative just like space. There is no absolute standard of time to say “time moves faster”. Faster relative to what?