When the big bang happened the whole what we see today was compressed to a space smaller than the nucleus of a atom. The Big Bang theory is the prevailing cosmological model explaining the existence of the observable universe from the earliest known periods through its subsequent large-scale evolution. Around 13.7 billion years ago, everything in the entire universe was condensed in an infinitesimally small singularity, a point of infinite denseness and heat. Suddenly, an explosive expansion began, ballooning our universe outwards faster than the speed of light. The universe began, scientists believe, with every speck of its energy jammed into a very tiny point. This extremely dense point exploded with unimaginable force, creating matter and propelling it outward to make the billions of galaxies of our vast universe. Astrophysicists dubbed this titanic explosion the Big Bang. The first long-lived matter particles of any kind were protons and neutrons, which together make up the atomic nucleus. These came into existence around one ten-thousandth of a second after the Big Bang. There was both matter and "antimatter" in roughly equal quantities. The Next 13 Billion Years. A lot happened in that first second of the big bang. But that's just the beginning of the story. After 100 seconds, the universe's temperature cooled to 1 billion degrees Kelvin (1 billion degrees Celsius, 1.8 billion degrees Fahrenheit). big-bang model, widely held theory of the evolution of the universe. Its essential feature is the emergence of the universe from a state of extremely high temperature and density the so-called big bang that occurred 13.8 billion years ago. As the universe cooled, the rest energy density of matter came to gravitationally dominate that of the photon radiation. After about 379,000 years, the electrons and nuclei combined into atoms (mostly hydrogen), which were able to emit radiation. As far as cosmologists can tell, the mysterious force behind the accelerated expansion of the universe, a force that we call dark energy, remains constant. But it may not have done so in the past. Very interesting how the new physics is explaining the cause of the Big Bang event now. The biggest explosion in the Universe since the Big Bang has been discovered by astronomers. The blast came from a supermassive black hole at the centre of a galaxy hundreds of millions of light-years away. “This is the most energetic outburst we have seen since the Big Bang,” she told the PA news agency. The Big Bang that began the universe is estimated to have released 1068 J of energy. How many stars could half this energy create, assuming the average star's mass is 4.00×1030 kg. In contrast, cosmologists believe the Big Bang flung energy in all directions at the speed of light (300,000,000 meters per second, a million times faster than the H-bomb) and estimate that the temperature of the entire universe was 1000 trillion degrees Celsius at just a tiny fraction of a second after the explosion. It was powerful enough to create all of observed space in our universe within the event horizon, drive the expansion for 13.8 billion years, and result in over 10^80 particles being created. Pune telescope detected an explosion five times bigger than the Big Bang 390 million light years from Earth. The blast, which released five times more energy than the previous record holder, came from a supermassive black hole at the centre of a galaxy hundreds of millions of light-years away. Astronomers once thought the universe could collapse in a Big Crunch. Now most agree it will end with a Big Freeze. Trillions of years in the future, long after Earth is destroyed, the universe will drift apart until galaxy and star formation ceases.

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