IAU Symposium 204 1 Observations carried out with the Cosmic Background Explorer (COBE) in the early 1990s have been processed and analyzed with increasing care over the past few years.These measurements are now yielding the first reliable estimates of the strength and spectral distribution of a ubiquitous extragalactic infrared background.Buried in this background are clues to the entire history of the universe since stars and galaxies first began to shine.If we could just unscramble the successive layers of information, each piled on top of a fainter, progressively more redshifted stratum, we would be able to discern how galaxies first formed, what kinds of stars they contained, and whether gravitational collapse rather than nuclear energy conversion first provided the energy to light up the cosmos.Symposium 204, convened at the 24th IAU General Assembly in Manchester in mid-August 2000, was a first attempt to come to grips with such questions.The difficulties of reliably measuring the infrared background are formidable.Atmospheric absorption and emission make ground-based observations hopeless.Worse yet, early measurements carried out with liquid helium-cooled rocketborne telescopes in the early 1970s already showed that zodiacal dust grains powerfully scatter and thermally reemit absorbed sunlight; similarly, interstellar dust radiating in the far-infrared all but swamps the faint cosmic background.These sources of foreground emission must be modeled in excruciating detail and subtracted out, if a genuine cosmic infrared background is to be uncovered.How best to achieve this was the topic of a series of talks by Leonid Ozernoy of George Mason University in Virginia, Martin Cohen of the
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Martin Harwit (2001) studied this question.