Cosmic Microwave Background Radiation - a leftover from The Big Bang

                                Have you ever seen black and grey dots on a TV screen after changing to an empty channel? Have you heard that strange noise when there was static? If yes, you've partly seen and heard Cosmic Microwave Background Radiation that occurs in the Universe. How's it possible?
                                CMB (Cosmic Microwave Background) is known to be a radio emission which is the result of the earliest stage of the Universe's evolution: The Big Bang. Even though we can't see it, the radiation reaches us from all directions. What's more: the existence of CMB was predicted by an American cosmologist Ralph Apher in 1948 but nobody really believed it would turn out to be true. There was a huge breakthrough in 1965 when two researchers Arno Penzias and Robert Wilson found out that actually there is a radiation coming from the sky. The interesting thing is that they did it by accident while they were working on a radio receiver. Wait, but where in the world did that emission come from?
                                As I wrote in my previous post - The Universe's temperature was really high in the past. When it cooled down enough, around 400,000 years after The Big Bang, there were better conditions for atoms to form, though they were still really hot. Hot matter emits particles called photons. Photons separated from the first atoms' electrons and filled the whole Universe. These photons cause the radiation I'm writing about. It's fascinating that they still exist, isn't it?
                                This is the picture of the CMB taken by one of the European Space Agency's satellites in 2013:


                                 You can get to know more by reading the article and watching the video:
https://www.space.com/33892-cosmic-microwave-background.html
https://www.youtube.com/watch?v=1kqWWLpyMpY