This animation demonstrates the production of the cosmic microwave background (CMB), and the expansion of the observable universe.
Gray plus signs represent points embedded in space. When the simulation starts, these points will expand away from one another.
At some time after the simulation begins, the universe is assumed to become transparent, and each plus sign will produce a blue photon of light directed at you (the left side of the screen).
The photons travel at the speed of light relative to local space, but space is receding from you. As a result, the photons appear, to you, to have varying speeds that depend on distance.
Furthermore, because space is expanding, the wavelength (color) of the photons expands too: the photons become redshifted. This explains why the CMB, despite having begun as highly energetic short wavelength radiation, is now down in the microwave part of the spectrum.
Finally, notice how each plus sign turns white when the photon it emitted reaches you. This means that the plus sign is now part of the observable universe. Notice how the observable universe grows over time.
Other information:
- Photon color is not meant to be accurate.
- Expansion occurs at a constant rate.
