The CMB and the Early Universe

What is Cosmic Microwave Background Radiation

Cosmic microwave background radiation, or CMB ( it is also known as relic radiation ) is a type of electromagnetic radiation of uniform density that fills the universe. It is believed that the CMB displays the heat caused  by the Big Bang (different post about that), the CMB is actually one of the biggest pieces of evidence that supports the Big Bang Theory. Also, because light moves at a fixed speed or as known by relativists the cosmic speed limit ( post on that soon ), we know that the CMB is the oldest light we have come in contact with, it is travelled for approximately  14 billion years.  Due to light's fixed speed we know from light's age how long ago what we are seeing occurred, an example of this is how the light from the Sun takes 8 minutes to reach Earth, if the Sun were to disappear, we wouldn't notice for 8 minutes because that's how long the light takes to travel there.

INTRESTING FACT :
Due to the accelerating expansion of the universe, the CMB's density and heat has been spread out which cooled it from being as hot the surface of a star to it being 2.8 K above absolute zero ( lowest point on the thermodynamic scale, where there is no heat energy in a substance).
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Picture of the CMB

Picture explaining universe development

What the CMB tells us about the Early Universe

The best quote to describe the CMB picture is that "it is the blueprint to the universe". Back to our topic, firstly the CMB confirmed the theory that the universe is constantly expanding, but that is not the main reason the CMB is so important. Its ability to correctly inform us about the size, temperature and elements of the universe are what make this discovery uniquely perfect. It suggests that the universe was denser (8 times more), smaller (that the  observable universe was half its current size) and hotter.  Also, it informs us that the universe was filled with hot hydrogen that  was 1000 atoms dense and that when the early universe. When the universe was 100 millionth its current size its temperature was 273 million K, and that early in the universe atoms could not be formed ( mostly just roaming electrons and nuclei) due to its intense heat. Finally, after 400,000 years after the Big Bang, the universe ( it was a seventh of its current size) cooled enough to form hydrogen atoms.

Final Facts and Thoughts

Recently, using advanced devices scientists were able to find fluctuations in the CMB's heat using WMAP and COBE, and by studying these they were able to learn how galaxies were formed and can verify the Big Bang theory. The CMB also provides evidence towards the existence of dark matter, but that is for a next post. Anyways I hope everyones staying safe, peace.