Cambridge IGCSE Physics · Syllabus 0625 · Space Physics
Cosmic Microwave Background Radiation
What is Cosmic Microwave Background Radiation?
Cosmic microwave background radiation, or CMBR, is microwave radiation of a specific frequency observed at all points in space around us. It was produced shortly after the Universe was formed and has been expanded into the microwave region of the electromagnetic spectrum as the Universe expanded.
This definition is part of the Space Physics chapter in Cambridge IGCSE Physics.
Cosmic Microwave Background Radiation in context
Core 6.2.3.1 The Milky Way is one of many billions of galaxies making up the Universe, and its diameter is approximately 100 000 light-years. Core 6.2.3.2 Light from receding stars and galaxies shows redshift — an increase in the observed wavelength of the electromagnetic radiation they emit. Core 6.2.3.3 Light from distant galaxies appears redshifted compared with light emitted here on the Earth. Core 6.2.3.4 That is evidence that the Universe is expanding, and it supports the Big Bang Theory.Extended candidates take this further: the same observations can be made quantitative, and a second, independent line of evidence — the cosmic microwave background radiation — is added to them.