Slashdot Mirror

← Back to Stories (view on slashdot.org)

Theory of Information Could Resolve One of the Great Paradoxes of Cosmology

Posted by Soulskill on from the bits-of-energy dept.

KentuckyFC writes: When physicists attempt to calculate the energy density of the universe from first principles, the number they come up using quantum mechanics is 10^94 g/cm^3 . And yet the observed energy density is about 10^-27 g/cm^3. In other words, our best theory of reality misses the mark by 120 orders of magnitude. Now one researcher says the paradox can be resolved by considering the information content of the universe. Specifying the location of the 10^25 stars in the visible universe to an accuracy of 10 cubic kilometers requires some 10^93 bits. And using Landauer's principle to calculate the energy associated with all these bits gives an energy density of about 10^-30 g/cm^3. That's not a bad first principles result. But if the location has to be specified to the Planck length, then the energy density is about 117 orders of magnitude larger. In other words, the nature of information should lie at the heart of our best theory of reality, not quantum mechanics.

2 of 183 comments (clear)

  1. Re:Numerology by Charliemopps · · Score: 4, Informative

    Why, for instance, 10 cubic-kilometer voxels? Why not 100, or 1, or 0.1? How about 10^{15} cubic kilometers, which is about the volume of the sun? Adjust this number correctly, and you can match any energy density you want.

    This is the problem with the science blogosphere: they'll take any press release whatsoever and echo it around regardless of whether or not it makes any fucking sense at all.

    No, they are basing it on Plank Length: http://en.wikipedia.org/wiki/P...
    A unit of measure derived specifically from universal constants, the speed of light, the Planck constant, and the gravitational constant.

    So it's not some arbitrary unit of measure as you suggest. It's the universes unit of measure. (assuming our current model of the universe holds) It's the smallest unit of measure that has any meaning in the real world.

  2. Re:Numerology by burtosis · · Score: 4, Informative
    Not sure if you are describing it correctly. They are not basing it on the plank length. They show that if you do the energy density of the universe is off by 117 orders of magnitude, close to the 120 orders off if you calculate the energy density of dark energy from first principles. The 10^4 km isn't totally at random, it's based on the free energy associated with encoding a center of mass classically in such a way as to make it unambiguous to independent observers.

    IANAP but it still smacks of numerology because the paper does not make any basis for why the mass of stars is important in any way. There is plenty of ordinary matter not in stars, black holes etc. what would have caught my attention is if it made a case based on mass and not just stars. Or at least gave a relevant basis for why it is negligible to discard non-star matter.

    tl:dr numerology. Though props to the author for saying it can be easily dismissed as numerology in his own paper - that's good scientific method.