Concern about the origin of the universe has always been one of the most fundamental of all questions that are difficult to answer. Through the Big Bang model, astronomers believe that they are quite successful in explaining a number of observations of the universe.
Although this model has some limitations, its fundamental ideas are not in doubt. One of the strongest pieces of evidence supporting the Big Bang theory is the presence of the cosmic microwave background radiation observed throughout the universe.
What is the Cosmic Microwave Background?
The cosmic microwave background (CMB) refers to the microwave radiation which fills all space in the observable universe. It represents the leftover radiation from the Big Bang or when the universe began.
CMB cannot be seen with the naked eye but is everywhere in the universe. It is so cold, just 2.725 degrees above absolute zero, making it invisible to humans since it is most visible in the microwave part of the electromagnetic spectrum.
The existence of the cosmic microwave background was first predicted by American cosmologist Ralph Apher in 1948 when he was working with Robert Herman and George Gamow. Their team was researching the Big Bang nucleosynthesis or the production of elements in the universe aside from the lightest isotope of hydrogen.
However, CMB was first discovered by accident in 1965. While working at Bell Telephone Laboratories, researchers Arno Penzias and Robert Wilson created a radio receiver and were puzzled when it picked up a signal that could not be attributed to any source in the sky. They soon realized that the noise came from all over the sky with the same intensity. Penzias and Wilson concluded that it had to come from outside our galaxy, almost from the universe's origin.
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CMB as Evidence of the Big Bang
Scientists consider the cosmic microwave background discovery to be solid evidence for the Big Bang theory. CMB radiation was believed to be radiated only a few hundred thousand years after the Big Bang, long before stars or galaxies existed. By studying the physical properties of CMB radiation, scientists can learn about the conditions in the universe on very large scales at very early times.
According to the Big Bang theory, the universe started as a catastrophic explosion around 13.7 billion years ago when it was hot and dense. As the theory goes, the universe underwent rapid inflation, expansion, and cooling when it was born.
During the initial moments of the expansion of the universe, only energy and quarks were present. About 380,000 years after the initial expansion, the universe cooled enough for electrons and protons to come together to form the atoms of hydrogen and helium. For the first time, light traveled all through the universe.
The CMB is the farthest and oldest light that any telescope can detect. Scientists cannot see further beyond the time of its release because, at that point, the universe was completely opaque. By mapping CMB, astronomers are looking back in time as close as possible to the Big Bang, allowing them to understand the birth and evolution of the universe in which we live.
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