The cosmic microwave background is the cooled remnant of the Big Bang, a sea of microwaves that fills the universe. Tiny ripples in its temperature and polarization encode the physics of the infant cosmos, from the density of matter to how fast space expanded.
Future experiments will push sensitivity to the curl‑like polarization patterns called B‑modes. Detecting a primordial signal would point to gravitational waves from an early burst of inflation, a leap in energy beyond anything achievable on Earth.
Mapping foregrounds is as important as chasing the signal. Dust and synchrotron emission from our galaxy can masquerade as primordial patterns. Multi‑frequency observations and careful component separation are the keys to honesty.
Even without a smoking gun for inflation, improved CMB measurements refine neutrino properties, dark energy parameters, and the sum of small anomalies that might nudge theory. Cross‑correlating with galaxy surveys and lensing maps turns each dataset into a multiplier for the others.
The CMB remains a gold standard: a simple signal from a complex universe that still has more to tell.