Cosmic microwave background

The cosmic microwave background (CMB) is the fossil light of the Big Bang, mapped by satellites like Planck and WMAP.

About this subject

The cosmic microwave background (CMB) is the electromagnetic radiation leftover from the Big Bang, filling the entire universe. Accidentally discovered in 1965 by Arno Penzias and Robert Wilson at Bell Labs, this radiation has a nearly uniform temperature of about 2.725 Kelvin, with tiny fluctuations that reveal the seeds of cosmic structures such as galaxies and clusters.

Satellites COBE (1989), WMAP (2001), and Planck (2009) produced increasingly precise maps of the CMB, allowing cosmologists to test cosmological models with high accuracy. For instance, the Planck map showed that the universe is 13.8 billion years old, composed of 68% dark energy, 27% dark matter, and only 5% baryonic matter (the matter we know).

The anisotropies in the CMB are regions with temperature variations on the order of 0.0002 Kelvin. These fluctuations are crucial for understanding galaxy formation: denser regions attracted matter and gave rise to the structures observed today. The polarization of the CMB also provides clues about cosmic inflation, an exponential expansion that occurred in the first moments of the universe.

Studying the CMB is essential for observational cosmology. It is considered the strongest evidence for the Big Bang model, ruling out alternative theories such as the steady state. Moreover, the CMB allows precise measurement of cosmological parameters and investigation of the physics of the early universe, including the possible existence of primordial gravitational waves.

Frequently Asked Questions

What is the cosmic microwave background?

It is the radiation leftover from the Big Bang, detected in all directions of the sky, with a temperature of 2.725 K. It was discovered in 1965 and is one of the key pieces of evidence for the Big Bang model.

Why is the CMB important for cosmology?

It provides a snapshot of the universe when it was only 380,000 years old, allowing scientists to measure its age, composition, and test theories about its origin and evolution.

What are the anisotropies of the CMB?

They are tiny temperature fluctuations in the cosmic background, which represent the primordial seeds of the galaxies and clusters we observe today.