The Imprint of The Extragalactic Background Light in the Gamma-Ray
  Spectra of Blazars
  The light emitted by stars and accreting compact objects through the history
of the Universe is encoded in the intensity of the extragalactic background
light (EBL). Knowledge of the EBL is important to understand the nature of star
formation and galaxy evolution, but direct measurements of the EBL are lim-
ited by Galactic and other foreground emissions. Here we report an absorption
feature seen in the combined spectra of a sample of gamma-ray blazars out to a
redshift of z$\sim$1.6. This feature is caused by attenuation of gamma rays by
the EBL at optical to UV frequencies, and allowed us to measure the EBL flux
density in this frequency band.
