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Dirac,large numbers and cosmology

  1. Aug 3, 2004 #1
    A very interesting interview with Paul Dirac on his large numbers hypothesis
    which relates to cosmology
    http://www.fdavidpeat.com/interviews/dirac.htm
     
  2. jcsd
  3. Aug 3, 2004 #2
    very interesting.
     
  4. Aug 3, 2004 #3

    Chronos

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    Always interesting to peek into the mind of someone like Dirac. However, even a genius like Dirac is entitled to a few dead end ideas. I would think most modern scientists would not be swayed by numerology based objections to theory. And since we are now fairly certain the age of the universe is considerably less than 18 billion years, the apparent connection he saw between the age of the universe and gravitational force appears to be broken.
     
  5. Aug 3, 2004 #4
    arthur eddington too did lots of work in that area, did he not?
     
  6. Aug 4, 2004 #5

    Chronos

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    Yep, Eddington refuse to accept the possibility of black holes [or neutron stars, for that matter].
     
  7. Aug 4, 2004 #6

    mathman

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    Eddington also used some sort of numerology argument to assert that the fine structure constant was exactly 1/137. The last time I checked, it was 1/137.0373, with an estimated error of .0006 in the denominator.
     
  8. Aug 4, 2004 #7
    Dirac said the number of particles in the universe - 10^78 - is equal to the age of the universe (in atomic time units) squared.Since the radius of the universe is proportional to its age this is the same as saying that the number of particles is proportional to radius squared.This would not work out even for dark energy if it is made of particles because we would need a dependency on r^3 to keep dark energy density constant.
    He also mentioned the idea that force of electricity/force of gravity = 10^39 = age of universe in atomic time unit.Apparently though, the Sun would have burnt a lot more fuel by now if gravity had been stronger in the past.
    Unless there was less dark energy in the past because it had provided some fuel for the Sun (but don't ask me how dark energy could become hydrogen atoms!)
     
    Last edited: Aug 4, 2004
  9. Aug 4, 2004 #8

    Chronos

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    Depending on what you count, the estimated number of particles in the universe ranges from between 10^78 and 10^80 for mass possessing particles, 10^86 if you add neutrinos and around 10^97 if you include all massless particles.

    Not sure where Eddington got 10^39 age as an age, aside from his contention it must be the square root of the number of particles. None of these numbers correlate with the square or square root of the current estimated age of the universe: about 8 x 10^60 planck time units. You would think planck time would be the preferred unit. I'm sure you could pick a unit that would give the right answer just as Eddington did when he reworked his nuclear fine structure constant calculation to change the result from 1/136 to 1/137. He had his idiosyncracies.
     
  10. Aug 4, 2004 #9

    turbo

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    True, but bold ideas can provide the seeds for advances.

    Let's try a thought experiment: If space-time is quantized, and if the universe is expanding, do the units of space-time expand to adjust to the size of the larger space or do they multiply in numbers? Both the former and the latter might prove troublesome to the BB theorists.
     
  11. Aug 6, 2004 #10
    turbo-1
    Let's try a thought experiment: If space-time is quantized, and if the universe is expanding, do the units of space-time expand to adjust to the size of the larger space or do they multiply in numbers? Both the former and the latter might prove troublesome to the BB theorists.

    Kurious:

    I would like to know if space can increase just at the edges - on the visible horizon - or everywhere simulataneously.Do units get added like tiles or like a gas that spreads everywhere?
     
  12. Oct 24, 2004 #11
    Depending on
    I resurected and quoted parts of both posts because the following adresses the concerns of both.

    r^3 dependency appears to be about 120 orders of magnitude out of whack with reality when the negative energy solutions are applied to General Relativity using Einstein's own original abandoned version of the cosmological constant:
    http://www.astro.ucla.edu/~wright/cosmo_constant.html

    E=mc^2 and E^2=m^2*c^4 are only different if there is a physical meaning to negative mass and negative energy values, where the second equation allows for both positive and negative mass-energy solutions.

    If, as with Einstein's model, the negative pressure component reflects -rho and gravitational curvature, then negative mass-energy must necessarily be expressed via negative density, as well. In order to make a real massive particle from this energy, you must condense enough of it over a finite region of space to achieve positve mass, density and curvature.

    In Einstein's static model, if you condense vaccum energy, then you necessarily increase negative energy and pressure, as well, by way of rarefaction, so the vaccum necessarily expands during pair production.


    Somebody dropped the ball when they leaped to conclude that an expanding universe will necessarily run-away.


    www.anthropic-principle.ORG
     
    Last edited: Oct 24, 2004
  13. Oct 25, 2004 #12

    Garth

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    Dirac wanted to express all units in a dimensionless way by dividing cosmological quantities by atomic equivalents. However might it be more fundamental to divide cosmological quantities by Planck equivalents? In this case the large number to look out for is not 10^(+/-39) but 10^(+/-60) or thereabouts and powers thereof. Any takers?

    Garth
     
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