taustasäteilynä

Taustasäteilynä, or cosmic microwave background (CMB) radiation, is a faint glow of electromagnetic radiation that fills the universe. It is considered the oldest light in the universe, originating from a time when the universe was about 380,000 years old. Before this time, the universe was a hot, dense plasma where photons were constantly scattered by free electrons. As the universe expanded and cooled, electrons combined with protons to form neutral atoms, allowing photons to travel freely. This event is known as recombination or decoupling.

The CMB radiation is remarkably uniform across the sky, with only tiny temperature fluctuations. These fluctuations are incredibly important as they represent the initial density variations in the early universe, which eventually grew under gravity to form the structures we observe today, such as galaxies and galaxy clusters. The spectrum of the CMB is a near-perfect blackbody spectrum at a temperature of about 2.725 Kelvin.

The discovery of the CMB in 1964 by Arno Penzias and Robert Wilson was a major confirmation of the Big Bang theory. Subsequent observations by missions like the Cosmic Background Explorer (COBE), the Wilkinson Microwave Anisotropy Probe (WMAP), and the Planck satellite have provided increasingly detailed maps of the CMB, allowing cosmologists to precisely measure fundamental parameters of the universe, such as its age, composition, and geometry. Studying the CMB continues to be a cornerstone of modern cosmology, offering crucial insights into the origin and evolution of the cosmos.