The Universe is everything around us, matter, time, energy and space. There is no concrete proof of how it was formed, but, there are several theories. The most widely accepted one is the one we have all heard before: The Big Bang Theory.
According to this theory, the Universe began as a super hot and highly dense point. It was only a few millimetres in size and was comparable to a supercharged black hole. Almost 13.7 billion years ago, it exploded or expanded very fast, to create matter, energy, space and time. This was followed by two key eras known as the Radiation and Matter era.
The Radiation Era, the smaller of the two eras, was further divided into smaller periods known as the epochs. This era consisted of a total of eight epochs, Planck, Grand Unification, Inflationary, Electroweak, Quark, Hedron, Lepton and Nuclear. Each of these epochs marked a major event that took place and was essential in the formation of the Universe. It would surprise you to know that the first seven epochs during which forces such as gravity and nuclear were born lasted for only about a total of 1 second combined! The Lepton epoch, by which the Universe had cooled down considerably and, sub-atomic particles such as neutrons and protons were already created, had a temperature of about 10^12 kelvin. The Nuclear era was marked by the combination of these sub-atomic particles to form nuclei, which ended about 100 seconds after the big bang. The last epoch was also marked by the formation of the Helium, which was one of the first elements to be formed.
The Matter Era, as the name suggests was a period in which matter was present and predominant. It spaned for billions of years, from the end to the Radiation Era to the present day. This Era consisted of three major epochs, the Atomic, Galactic and Stellar epochs. During the atomic era, which lasted for about 50,000 years after the big bang, the temperature simmered down to 3,000 kelvin. This is when recombination took place and Hydrogen was formed. The two elements, hydrogen and helium, led to the formation of atomic clouds throughout the Universe in the Galactic epoch. 200 million years after the bang, in the galactic epoch, the seedlings of galaxies were formed. The Stellar epoch was marked by the creation of stars in the galaxies, causing a ripple effect which shaped the Universe as we know it today.
Coming to think of it, the Big Bang leaves me wondering:
Was the Big Bang only for us, or are there others out there?