Summary
The CMB is remarkably uniform in temperature across the entire sky, differing by only tiny fluctuations, indicating a common origin for all observed regions of the universe.
Observation / Fact
Temperature measurements show uniformity to one part in 100,000, regardless of direction, after accounting for Earth’s motion.
Why This Is Non-Trivial
Regions of the universe separated by vast distances should not have been in causal contact under simple expansion models, yet they share nearly identical thermal properties.
What It Implies
The observed isotropy points to a shared early condition for the universe and supports models involving a hot origin followed by expansion, rather than independent or eternal regions.
Related
- Blackbody Spectrum Precision
- Anisotropy & Structure Seeds