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Which are the constants needed for the universe to exist?

  1. Aug 19, 2009 #1
    I heard a http://www.youtube.com/watch?v=YtdE662eY_M"by Brian Greene where he states that there are over 20 constants needed for the universe to exist, Which are those constants?
     
    Last edited by a moderator: Apr 24, 2017
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  3. Aug 19, 2009 #2

    marcus

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    Nobel laureate Frank Wilczek and his co-authors in this paper listed 31.
    http://arxiv.org/abs/astro-ph/0511774

    The number 31 is not specified by Nature but depends on the man-made models of particle physics and cosmology. Perhaps in the future we will have a better model of particle physics which requires fewer numbers input to it.
    A model which is just as accurately predictive as the now standard particle physics model, but which required fewer numbers input would be considered more elegant.

    As I recall of these 31 about 26 are inputs to the particle physics model and the remaining 5 are cosmology parameters, like the expansion rate and the dark energy density and various key things. They have to be adjusted in order for the presentday cosmo model to fit the observation data.

    The particle standard model parameters are things like the relative masses of various particles, mass ratios. And ratios of different forces.

    The basic reference quantities that the numbers relate to are G, hbar, c. These are taken as given and are not included in the list. They are actually not numbers, they are three basic raw quantities used to compare other things with.

    Brian Greene is an inspiring speaker with exciting delivery style, but he seems to leave many people with false impressions. He most likely did not say that the 31 numbers had to be exactly these that we measure. The universe could still exist if many of them were a few percent different, or even as I recall different by a factor of two! There is some room to play around.

    But changing some would for example change the number of stable chemical elements in the periodic table by making some elements that we have be radioactive, and decay. A drastic change in the numbers might make many chemical elements cease to exist, maybe only hydrogen and would exist. Then stars wouldn't be able to do fusion. A lot of things would stop working right. (at least by our standards)

    He may have introduced a qualifying phrase like "as we know it".
    If some of these numbers were changed by more than a few percent then the universe as we know it would not exist. It wouldn't necessarily go away, it could still be there but be different from the universe we know and love.
     
    Last edited by a moderator: Apr 24, 2017
  4. Aug 19, 2009 #3

    apeiron

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    So what are the various theories about how these three raw scaling factors relate?

    They would seem to fit neatly into a scale hierarchy perspective where such a triad is what is expected.

    So the cannonical hierarchy has two levels of scale in interaction. In this view, hbar would define the local grain - a metric for the smallest resolvable components. G would define the global form - a measure of general flatness (G being the scalar of observable deviations from this spatiotemporal flatness). And then c is the measure of the rate of equilbration, the interaction between the smallest and largest scales. What in scale hierarchy theory would be called the "cogent moment" (and in physics, a causal light cone).

    This is how I personally expect the key three to be connected to define a general cosmological framework. But what other kinds of stories are there?
     
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