A quiet longform journey through the evidence for cosmic dawn: the galaxies we can measure, the hydrogen between them, and the questions that remain in their spectra.

The film follows infrared color selection, spectroscopic redshifts, neutral hydrogen, quasar sightlines and the photon budget behind reionization. Each method brings its own selection limits and model assumptions.

Early galaxies remain unresolved sources. Their measured light can constrain gas and stellar models, but does not directly identify the first stars. A radio upper limit is not a detected cosmic signal; a local sightline is not a map of the whole Universe. Artist concepts and explanatory diagrams remain separate from observed spectra and published data.

Chapters:
00:00:00 A Galaxy in the Early Light
00:03:43 The Background That Remembers
00:12:59 Listening to Neutral Hydrogen
00:25:03 The Stars We Have Not Seen
00:41:33 A Color Can Point the Way
00:55:04 Turning a Candidate Into a Spectrum
01:16:06 The Galaxies a Survey Can Count
01:29:09 A Quasar Looks Through the Fog
01:43:38 The Photon Budget
01:57:12 The Questions Still in the Spectrum
02:16:44 What Changed When the First Galaxies Lit Up?

Sources and further reading:
Naidu et al. (2026), MoM-z14 spectroscopy:
https://astro.theoj.org/article/156033-a-cosmic-miracle-a-remarkably-luminous-galaxy-at-_z_-sub-spec-sub-14-44-confirmed-with-jwst
Carniani et al. (2024), JADES spectra: https://www.nature.com/articles/s41586-024-07860-9
Planck Collaboration (2020): https://doi.org/10.1051/0004-6361/201833910
HERA Phase II (2026): https://doi.org/10.3847/1538-4357/ae2d54
Witstok et al. (2025): https://www.nature.com/articles/s41586-025-08779-5
Zhu et al. (2026), UV absorption in three galaxies: https://doi.org/10.1038/s41550-026-02988-2

Find us on:
YouTube: https://www.youtube.com/@GreenSpacealien15
Facebook: https://www.facebook.com/profile.php?id=61594406836899
Instagram: https://www.instagram.com/greenbigspacealien15/
X: https://x.com/GreenSpacealie
TikTok: https://www.tiktok.com/@greenbigspace15
Reddit: https://www.reddit.com/r/GreenSpacealien15/
Dailymotion: https://www.dailymotion.com/user/green.hbw590
Pinterest: https://www.pinterest.com/greenbigspacealien15/
Rumble: https://rumble.com/user/greenspacealien15
Threads: https://www.threads.com/@greenbigspacealien15
Bluesky: https://bsky.app/profile/greenspacealien15.bsky.social