Fossil light from early Cosmos
It is said that the journey of our Universe began approximately 15 billion or so years ago with the commencement of the phenomena called the Big Bang (BB). The echoes of this cataclysmic event can still be seen today from every direction of the Universe in the form of faint traces of microwave radiation. This is known as the Cosmic Microwave Background Radiation (CMBR) which is basically the residual heat from the moment of creation, the afterglow of the Big Bang. The CBR is distributed throughout the universe uniformly and with equal intensity in all directions. This ancient relic harks back to the the time when the Universe was at its infancy. As time progressed and Universe got older and expanded, the heat and intensity of CMBR cooled down. It has been estimated that, at present the temperature is about 2.73 degrees, just above absolute zero, not even strong enough heat up microwave popcorn.
It was merely an accident that led to this groundbreaking discovery. Back in 1964, astronomers Arno Penzias and Robert Wilson of Bell Telephone Laboratories were trying to solve a static problem in a project in which a microwave antenna was picking up that undesired static distortion. Initially they thought that it was pigeon droppings that was causing such problem. However when they further investigated the source of this static they stumbled upon this CMBR and realized that they have discovered a radiation that was the leftover from early Universe. It is This finding eventually diminished the "Steady State Theory" which stated that the Universe had no beginning. Penzias and Williams received Nobel Prize in 1978 for their contribution in Physics.
Before the formation of all the planets, stars, galaxies and other cosmic matters, the young, hot and single Universe was filled with a uniform glow from its primordial white boiling fog of hydrogen plasma. But as the Universe got older and expansion started to happen and protons and neutrons came into being, these two eventually formed neutral atoms. And these atoms could no longer soak up the thermal radiation. Eventually the Universe became transparent instead of its previous dense, hot fog-like appearance. And it is believed that the photons that existed at that time became disseminated in the process and grew fainter and cooler. It is these photons that filled up the background of our Universe constitute the CMBR.
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