What actually exists between galaxies? Even though photographs of the gaps between visible galaxies look almost black, that space holds most of the universe's ordinary matter, arranged in a changing network shaped by gravity, gas, radiation and galactic activity.

So what fills those seemingly empty gaps, and how do we know it's there? How does gravity organize matter into a cosmic web that stretches beyond any single galaxy's stars? What happens to gas as it falls into filaments, and why do oxygen atoms in hot gas offer clues to conditions between galaxies?

A quick note: the visuals in this video are illustrations built to accompany the science, not real photographs or footage of these events.

If a moment from this one stays with you, let me know which one in the comments, I read every one.

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Chapters:
0:00 Introduction
0:42 The Gap That Holds Matter
5:40 The Framework Beneath the Light
10:28 Where a Galaxy Ends
15:02 Hydrogen Written Into Passing Light
19:35 How the Web Heats
24:31 The Oxygen Trace
29:28 When a Filament Becomes Visible
33:52 A Radio Flash Crosses the Gap
38:27 Inside a Cluster
42:52 Stars and Dust Beyond Galaxies
47:26 Galaxies Reach Into the Dark
51:59 The Gap Before It Looked This Way
56:26 What the Space Between Can Change
1:01:16 Conclusion

#Cosmology #Space #Science