What's a cosmic microwave background?

What's a cosmic microwave background?

The cosmic microwave background is the residual heat left from the early years of the Big Bang, which is the most important evidence in support of the Big Bang theory.

Our universe is supposed to start with the Big Bang; the universe was packed into a tiny space that exploded and formed the space that we now see around us; one of the most important proofs of this theory is the residual radiation that can still be found in the empty spaces of space — the space microwave background.

Space microwave background

In the night sky, we see space as it is, as it is, as black as it is. When we see stars and planets in the sky, it seems that between them there are vast distances, a distance filled with absolutely nothing, just a black void.

You can imagine that if you were to explore this void, you wouldn't have found anything, but the reality of the situation contradicts your intuition. When this space between objects is seen for radiation, it shows a faint microwave static signal invisible to our eyes. It seems that the static is present wherever you look. No matter how much interference you remove, it will show a microwave diagram, unlike everything we've seen before.

Since this pattern is everywhere we look, it must be a source of something that covers the entire universe, but of course we know that there is no supersized source of energy that emits this static microwave pattern in all directions of the universe.

This static microwave pattern is known as the Space microwave background, and is usually considered to be the heat residue of the Big Bang.

Big bang theory and relic radiation

The Big Bang Theory

After the singularity, our universe went through different phases. Initially, the density was very high, and the temperature was too high to form building blocks of matter. For example, at these early stages, the size of the universe was about one hundred million degrees above the size of the universe today, and the temperature was 273 million degrees above absolute zero.

Relict radiation is the residue of the vast heat of the infantity of the universe, which prevented atoms from forming at an earlier stage, so they were later broken into photons and electrons, so the cosmic microwave background photons simply scattered electrons, and photons wandering aimlessly like "optic light wanders through dense fog".

The universe cooled down enough to form atoms, but the wandering photons didn't interact with hydrogen atoms and instead started moving straight lines. The universe became more transparent, and at that time the last photons get into matter. It was 380,000 years after the Big Bang, and we know that, because when we study the relict background today, it can be dated in time when the translucentness of the universe became radiation.

This era is also known as "the last scattering," similar to how we can see through the air of clouds, but not through dense clouds, so cosmologists can see the distant beginning of the universe, but only after the last scattering and apparent lack of transparency of the universe.

Relic radiation was detected by accident

In 1948, American cosmosologist Ralph Alfer first predicted the relic radiation; he did so with his colleagues Robert Herman and George Gamov as part of their study of the nucleosynthesis of the Big Bang; at the time, their prediction was not particularly supported because the astronomical community was not very intrigued by cosmology.

Subsequently, in the 1960s, the theory was put forward that Relict radiation could be detected, but only in 1965 was it finally "detected." Arnaud Penzias and Robert Wilson were building a radio for Bell Telephone Laboratories in Murray Hill, New Jersey, for experiments in satellite communications, and they encountered radiation that was an annoying source of too much noise, no matter how much they tried to remove the interference, the radiation didn't go anywhere. Soon enough, they realized that something they had discovered was a space background radiation and wrote an article in which they published their discovery.

Arno Penzias and Robert Wilson shared the Nobel Prize in Physics in 1978 for the accidental discovery of relic radiation.

Relict irradiation utility

Relict radiation not only provides basic evidence of the Big Bang theory, but is also a useful tool for scientists to understand the earlier state of the universe; it is also linked to its apparent ubiquitousness, as it occurs in all regions with homogeneous temperatures, but shows little variation in observation using accurate telescopes. These fluctuations can be studied to measure the parameters of the theory and to understand the origins of galaxies and subsequent large-scale structures.

It also enabled NASA to take the first picture of the universe as a baby. In 1989, NASA launched its Cosmic Background Explorer mission, which charted the first full-scale space map of the universe.

This map was further refined in 2003 by Wilkinson's microwave anisotropic probe, launched in 2003, which not only provided a more detailed map, but also estimated the age of the universe at 13.7 years, which was further corrected to 13.8 billion years, giving a clearer understanding of the content of our universe, which consists of 4% atoms, 23% of unknown dark matter type and 73% of mysterious dark energy.

As we continue to analyse and study the relic radiation, it will certainly continue to shed light on many of our other favorite questions about the universe!