Cosmic Microwave Background
Episode #3 of the course “Strangest Things in Space”
The Cosmic Microwave Background (CMB) resulted from the Big Bang. It is the thermal radiation leftovers from such an incomprehensibly massive event. In other words, it is the side effect of the universe changing from a plasma into a gas. This radiation fills the universe and can be detected everywhere we look with the right tools. Scientists liken the CMB to seeing sunlight filtering through an overcast sky.
Arno Penzias and Robert Wilson discovered the CMB in 1963. While analyzing faint microwave signals from the Milky Way, they picked up noises which they originally thought were due to interference from pigeon droppings on their equipment. This noise, of course, actually turned out to be the radiation from the CMB.
The reason the CMB is so important is because it proved the Big Bang theory for the creation of the universe. Up until that point, there were two competing theories: the Big Bang and the Static State theory. The latter insinuated that the universe has existed forever and has maintained the same density throughout. The Big Bang, on the other hand, not only started the universe with a singular spectacular event, but also implies that as the universe continues to expand, it also becomes less dense.
No light in the universe is older than the CMB. When anyone—astronomer, physicist, or even regular Joe—looks into the sky, they are also looking into time, or the past, to be specific. It takes light a long time to travel across the vast universe—millions of years in some cases, so the stars and light we see in the night sky are objects that existed in the past. Such is the case when physicists study the CMB; they are looking into the past, to the very origins of our universe.
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