50.0 MB (839.1 KB compressed)
3576 x 4888 pixels
30.2 x 41.4 cm ⏐ 11.9 x 16.3 in (300dpi)
MARK GARLICK / SCIENCE PHOTO LIBRARY MARK GARLICK / SCIENCE PHOTO LIBRARY
Illustration showing the reionization of the Universe. Following the Big Bang, the Universe was little more than a soup of charged subatomic particles and energy (top, red). As the Universe expanded and cooled, there came a point – at an age of 300, 000 years – when most of the protons and electrons had combined to form a sea of neutral hydrogen gas. This heralded the so-called Dark Ages, when the Universe became opaque. A few hundred million years later, some of the hydrogen had started to gather into stars and, in turn, galaxies and quasars. These new structures unleashed a torrent of ionizing radiation that began to ionize the remaining neutral hydrogen, beginning the so-called Epoch of Reionization. At an age of 1 billion years, the Universe became transparent again (bottom).
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