Cosmic microwave background. Animation showing the origin and appearance of the cosmic microwave background (CMB). This is the relic radiation from the Big Bang. The animation starts with the Big Bang 13.798 billion years ago. The radiation produced during this event is shown as gamma rays (yellow waves; high energy, short wavelength, high frequency). The animation then shows the universe (bright light) expanding until the present day. By this time, the gamma rays have become microwaves (yellow; lower energy, longer wavelength, lower frequency). This radiation permeates the whole Universe in all directions as a background radiation. However, the temperature of the CMB radiation is not completely uniform. There are tiny variations, or fluctuations, which reveal the initial conditions of the Universe, the first seeds of the structures, such as galaxies, that we observe today. This is shown in the animation as a coloured circle (blue and orange), the results of all-sky space telescope observations of the CMB. |