Universe opacity and EBL
  The observed extragalactic background light (EBL) is affected by light
attenuation due to absorption of light by galactic and intergalactic dust in
the Universe. Even galactic opacity of 10-20 percent and minute universe
intergalactic opacity of $0.01\,\mathrm{mag}\,h\,\mathrm{Gpc}^{-1}$ at the
local Universe have a significant impact on the EBL because obscuration of
galaxies and density of intergalactic dust increase with redshift as
$\left(1+z\right)^3$. Consequently, intergalactic opacity increases and the
Universe becomes considerably opaque at $z > 3$. Adopting realistic values for
galactic and intergalactic opacity, the estimates of the EBL for the expanding
dusty universe are close to observations. The luminosity density evolution fits
well measurements. The model reproduces a steep increase of the luminosity
density at $z<2$, its maximum at $z=2-3$, and its decrease at higher redshifts.
The increase of the luminosity density at low $z$ is not produced by the
evolution of the star formation rate but by the fact that the Universe occupied
a smaller volume in previous epochs. The decline of the luminosity density at
high $z$ originates in the opacity of the Universe. The calculated bolometric
EBL ranges from 100 to 200 $\mathrm{n W m}^{-2}\mathrm{sr}^{-1}$ and is within
the limits of 40 and 200 $\mathrm{n W m}^{-2}\mathrm{sr}^{-1}$ of current EBL
observations. The model predicts 98\% of the EBL coming from radiation of
galaxies at $z<3.5$. Accounting for light extinction by intergalactic dust
implies that the Universe was probably more opaque than dark for $z>3.5$.
