Cosmic Microwave Background Radiation
Although this is called the Dark Age, the Universe was not completely dark. After decoupling, photons were able to travel unhindered by the electrons which used to cause the fog. Now radiation could travel for huge distances before hitting anything. At the time this radiation had high energy, but in the billions of years since decoupling, the expansion of the Universe has stretched it out. The radiation dropped down the radiation spectrum towards the low energy end. rays became X rays, then ultra-violet and so on. Today it is seen as weak microwave radiation, the Cosmic Microwave Background Radiation (CMBR).
Cosmic Microwave Background Radiation image from NASA
We find these microwaves in all directions in space, and almost always with the same strength. There are, however, small differences in them, the echoes of the varied distribution of matter at the moment of recombination.
If you de-tune your TV set so that it is not tuned to a particular channel, some of the "snow" you see on your screen comes from the cosmic background radiation.
CMBR is one of the main reasons for believing that the Big Bang really happened.
Hidden Secrets of CMBR
By using new telescopes to examine the cosmic microwave background radiation, new things could be revealed about our Universe and Galaxy. For example it might show signs of collisions with other universes.
Let us use the PennySystem to try to get a feeling for the size of the Universe. Even though the Universe is only 14 billion years old, according to Charles Lineweaver and Tamara M. Davis its expansion means the observable Universe is about 46 billion light-years radius.
If the Solar System were the same size as a penny (our PennySystem model) then the distance to the edge of the observable Universe would be about three times as far away as the Moon from the Earth.
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