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The Hubble was pointed at what appeared to be a black void of space, and revealed lush fields of stars and galaxies. So at one degree of perception, we have an

The Hubble was pointed at what appeared to be a black void of space, and revealed lush fields of stars and galaxies. So at one degree of perception, we have an empty void, and at another, a bright flush of light and activity.

avian 6y ago
There is still plenty of space between the individual stars in the Hubble Deep Field image. From that point of view it just confirms the paradox - even with a powerful telescope stars don't fill up your entire field of view. I think a more fitting example of "an empty void yet a bright flush of light" would be the microwave background. With eyes sensitive to longer wavelengths the entire sky is indeed bright.
- deleted 6y ago
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- jessermeyer 6y ago
  > even with a powerful telescope stars don't fill up your entire field of view. Suppose the experiment is repeated on a black pixel from the Deep Field image, and another swell of stars are observed, hinting at a kind of fractal distribution. Were the universe eternal and static, why could this pattern not repeat indefinitely in infinite time, space and matter? The paradox seems to assume a kind of infinite level of sensitivity of the observer.
  - avian 6y ago
    No, the paradox as described in the Wikipedia article doesn't assume the infinite level of sensitivity. The figure explains it visually - the further away you go from the observer, the more stars you capture in your camera's field of view and the apparent brightness stays the same. The 1/r^2 term for light intensity is cancelled by the r^2 for the number of stars. It's interesting think what an experimental result you describe would imply. It either contradicts the nature of light or that we're in the center of a cloud of stars where the density of stars falls with distance from us.
    - jessermeyer 6y ago
      Thanks for spelling it out. Makes more sense now.
- raattgift 6y ago
  > With eyes sensitive to longer wavelengths the entire sky is indeed bright With eyes sensitive to the CMB, the CMB is dimming and reddening. Such eyes witnessing an essentially isotropic and homogeneous CMB would be Eulerian observers of the CMB. (In contrast to observers who see a dipole anisotropy because of acceleration along one spatial axis, for example, or observers immersed in the gravitational field of a massive system like a galaxy cluster or a planet). Such Eulerian observers see a clearly peaked spectrum, essentially identical to a that of a blackbody radiator that is cooling. If such observers are in deep inter-galaxy-cluster space and equipped with instruments to augment their CMB-sensitive eyes, they'd detect plenty of bright spots with frequencies much much lower than the peak in the CMB. As an example an https://en.wikipedia.org/wiki/Radio_galaxy https://en.wikipedia.org/wiki/Radio_galaxy will be much brighter in wavelengths longer than that of the CMB (spectral radiance peak of CMB is ~ 160 GHz and falls off quickly away from the peak). That -- correcting for proper motions and atmospheric effects -- our view of the sky is pretty uniform in the CMB (cf. https://en.wikipedia.org/wiki/BOOMERanG_experiment https://en.wikipedia.org/wiki/BOOMERanG_experiment and beyond) but far from uniform in VLF, radio, IR, UV, X-Rays, gamma rays, and so on (as known since roughly the 1930s thanks to https://en.wikipedia.org/wiki/Karl_Guthe_Jansky#Radio_astronomy https://en.wikipedia.org/wiki/Karl_Guthe_Jansky#Radio_astron... ) just like it is in visible light, and that the bright spots at different frequencies aren't coincident in our sky, are important pieces of evidence which must be dealt with by any prospective model of physical cosmology.

avian 6y ago

There is still plenty of space between the individual stars in the Hubble Deep Field image. From that point of view it just confirms the paradox - even with a powerful telescope stars don't fill up your entire field of view. I think a more fitting example of "an empty void yet a bright flush of light" would be the microwave background. With eyes sensitive to longer wavelengths the entire sky is indeed bright.

deleted 6y ago
[deleted]
jessermeyer 6y ago
> even with a powerful telescope stars don't fill up your entire field of view. Suppose the experiment is repeated on a black pixel from the Deep Field image, and another swell of stars are observed, hinting at a kind of fractal distribution. Were the universe eternal and static, why could this pattern not repeat indefinitely in infinite time, space and matter? The paradox seems to assume a kind of infinite level of sensitivity of the observer.
- avian 6y ago
  No, the paradox as described in the Wikipedia article doesn't assume the infinite level of sensitivity. The figure explains it visually - the further away you go from the observer, the more stars you capture in your camera's field of view and the apparent brightness stays the same. The 1/r^2 term for light intensity is cancelled by the r^2 for the number of stars. It's interesting think what an experimental result you describe would imply. It either contradicts the nature of light or that we're in the center of a cloud of stars where the density of stars falls with distance from us.
  - jessermeyer 6y ago
    Thanks for spelling it out. Makes more sense now.
raattgift 6y ago
> With eyes sensitive to longer wavelengths the entire sky is indeed bright With eyes sensitive to the CMB, the CMB is dimming and reddening. Such eyes witnessing an essentially isotropic and homogeneous CMB would be Eulerian observers of the CMB. (In contrast to observers who see a dipole anisotropy because of acceleration along one spatial axis, for example, or observers immersed in the gravitational field of a massive system like a galaxy cluster or a planet). Such Eulerian observers see a clearly peaked spectrum, essentially identical to a that of a blackbody radiator that is cooling. If such observers are in deep inter-galaxy-cluster space and equipped with instruments to augment their CMB-sensitive eyes, they'd detect plenty of bright spots with frequencies much much lower than the peak in the CMB. As an example an https://en.wikipedia.org/wiki/Radio_galaxy https://en.wikipedia.org/wiki/Radio_galaxy will be much brighter in wavelengths longer than that of the CMB (spectral radiance peak of CMB is ~ 160 GHz and falls off quickly away from the peak). That -- correcting for proper motions and atmospheric effects -- our view of the sky is pretty uniform in the CMB (cf. https://en.wikipedia.org/wiki/BOOMERanG_experiment https://en.wikipedia.org/wiki/BOOMERanG_experiment and beyond) but far from uniform in VLF, radio, IR, UV, X-Rays, gamma rays, and so on (as known since roughly the 1930s thanks to https://en.wikipedia.org/wiki/Karl_Guthe_Jansky#Radio_astronomy https://en.wikipedia.org/wiki/Karl_Guthe_Jansky#Radio_astron... ) just like it is in visible light, and that the bright spots at different frequencies aren't coincident in our sky, are important pieces of evidence which must be dealt with by any prospective model of physical cosmology.