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In addition to its relevant astrophysical and cosmological significance, theExtragalactic Background Light (EBL) is a fundamental source of opacity forcosmic high energy photons, as well as a limitation for the propagation ofhigh-energy particles in the Universe. We review our previously publisheddeterminations of the EBL photon density in the Universe and its evolution withcosmic time, in the light of recent surveys of IR sources at long wavelengths.We exploit deep survey observations by the Herschel Space Observatory and theSpitzer telescope, matched to optical and near-IR photometric and spectroscopicdata, to re-estimate number counts and luminosity functions longwards of a fewmicrons, and the contribution of resolved sources to the EBL. These new dataindicate slightly lower photon densities in the mid- and far-infrared andsub-millimeter compared to previous determinations. This implies slightly lowercosmic opacity for photon-photon interactions. The new data do not modifypreviously published EBL modeling in the UV-optical and near-IR up to severalmicrons, while reducing the photon density at longer wavelengths. This improvedmodel of the EBL alleviates some tension that had emerged in the interpretationof the highest-energy TeV observations of local \textit{blazar}s, reducing thecase for new physics beyond the standard model (like violations of the LorenzInvariance, LIV, at the highest particle energies), or for exotic astrophysics,that had sometimes been called for to explain it. Applications of this improvedEBL model on current data are considered, as well as perspectives for futureinstrumentation, the Cherenkov Telescope Array (CTA) in particular.

The extragalactic background light revisited and the cosmic photon-photon opacity