Unraveling the Mystery of Extra-Galactic Background Light

The chapter explores the challenges of identifying the sources of extra-galactic background light, attributing them to potentially unknown sources or underestimated scattering effects in the universe. It discusses the use of high-energy photons from quasars to map the presence of this diffuse light, shedding light on the origins of photons as they travel through space. Additionally, it delves into the significance of cosmic infrared and microwave background light in unraveling the early universe's secrets.