What Is the Cosmic Microwave Background—and What Is It Not?

Why does this microwave light reveal an ancient last-scattering era rather than a picture of the beginning itself?

Follow ancient light from repeated scattering to a mostly clear path, stretch its wavelength, and learn what a measured microwave spectrum and an all-sky map actually show.

Diffuse amber haze gradually gives way to broad charcoal and slate darkness, without stars or a sharp dividing line. — Vastward-generated concept art: haze becoming clearer is a metaphor for increasing transparency. The colours and spatial transition are artistic, not measurements, a temperature map, or a boundary of the universe. Complete original frame.

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