ASTRON 100 Lecture Notes - Lecture 25: Cosmic Microwave Background, Gravitational Redshift, Black-Body Radiation
Document Summary
The expansion of the universe implies a big bang ~13. 7 billion years ago. From any galaxy in the universe, other galaxies appear to recede . Except for some nearby galaxies in the same galaxy group might be due to blue-shifted due to intra-group interactions. The universe is made up of dark energy, dark matter, and regular matter (baryons) Dark matter obeys gravity, but does not emit detectable radiations. Dark matter provides an unknown vacuum force that pushes the universe apart. The density of total matter/energy determines the fate of the universe. The critical density is when the mass/energy density is just enough to balance the expansion of the universe. Blackbody radiation in all directions when electrons and nuclei formed into atoms. The cmb (cosmic microwave background) gradually cooled as the universe started out hot and dense expanded. Photons interact with electrons; this is why this happens. Question: the cosmic microwave background is visible in every direction because. .
