LMR-069 · Cosmology
CMB
The afterglow of the Big Bang, still arriving 13.8 billion years later.
§ A first look
§ Depths
Six ways into the same idea — from bedtime story to chalkboard. No order required.
L1 · Crayon
Told like a bedtime story.
For a curious 10-year-old. No jargon. Just a picture in your head.
When the universe was very young — only a few hundred thousand years old, which is basically a baby in cosmic terms — it was a hot, glowing fog of stuff, like the inside of a furnace. Then it cooled just enough that the fog cleared, and all the light bouncing around at that moment was suddenly free to fly outward. That very old light is still arriving at Earth right now, from every direction, much fainter and stretched out from the long trip. We call it the cosmic microwave background. It's basically the baby photo of the entire universe, and it's still in our inbox.
§ Strange but true
- 01It's the afterglow of the Big Bang, cooled over 13.8 billion years to a chilly 2.7 K — and it fills every direction you point.
- 02Tiny temperature ripples — one part in 100,000 — are the seeds every galaxy grew from.
- 03Some of the static on an old analog TV was the actual light of the early universe.
§ From the field journal
CMB
"The afterglow of the Big Bang, still arriving 13.8 billion years later."
— observed, sketched, not yet fully understood.
§ Nearby