The CMB is the oldest light we can see — a snapshot of the universe 380,000 years after the Big Bang, its tiny temperature ripples the seeds of every galaxy that formed since.
delta_T/T ~ 10^-5
angular power spectrum shows acoustic peaks
- Angular resolution — how finely the all-sky temperature map is sampled.
- Fluctuation amplitude — the tiny temperature variation scale (~microkelvin) recorded across the sky.
- Acoustic oscillation scale — the characteristic size of hot/cold spots set by sound waves in the early plasma.
- Foreground noise — contamination from our own galaxy that has to be modelled out to see the true CMB signal.
The Planck satellite mapped exactly this sky at higher resolution, and its acoustic-peak pattern is how cosmologists pinned down the universe's age and composition.