In our school days, most of us would have read about the creation of the universe and finally, life on our planet. I have always been amazed by the vastness of the universe, how it came into being and am fascinated by theories that try to explain the unthinkable: What happened before (and after) the beginning of time. I’ll first try to recapitulate the history of the universe that I have read over the past years. Let’s see how it goes.
From what I can recall, according to the big bang theory, as proposed by Friedman, about 13.5 billion years ago, the universe started as a (relatively) small primeval atom with an incomprehensibly high temperature, pressure and energy. After the big bang, (only a microsecond later!) the universe had grown in size exponentially and the basic building blocks of matter: protons & neutrons had been formed. The universe continued to expand in size continually. Matter, which was mostly homogeneously distributed throughout the universe, at that time, started clustering together due to gravitational forces of attraction. These clusters then clumped together to form even larger gas clouds, which later gave rise to stars. Stars which constitute the beautiful galaxies we see today in the night sky. One of which is our very own Milky Way.
So let us come closer to home. Let us talk about our own solar system. A long time after the creation of the universe, about 4.5 billion years ago, a supernova i.e. the explosion of a star, in our galaxy, gave rise to a huge cloud of gas, which eventually resulted into the formation of our solar system including the sun, the planets and other heavenly bodies. The (hot and molten) Earth was also formed at about the same time (roughly 4 billion years ago).
The Earth, initially, did not have an atmosphere. As a result, other smaller objects (planetesimals), meteors, which got attracted towards the Earth due to its gravitational pull, received little air resistance and hence fell, right onto Earth’s surface very frequently. However, it was the same meteors that are believed to have brought substances to the Earth which were essential for creation of primitive life. At about this time, the Earth was hit by a large planetesimal, off center. This resulted in a lot of debris thrown out into space. Most of it got attracted back to Earth’s surface. What remained formed Earth’s only natural satellite, the moon. Slowly and gradually the earth began to cool down. The gases released from Earth’s interior formed the initial atmosphere.
And finally, we arrive at the creation of life. About 3.5 billion years ago, the atmosphere consisted mainly of hydrogen, water, methane and ammonia. Electrical discharges of lightening in the atmosphere, radioactivity, etc caused these elements to convert into the basic molecules necessary for life (nucleotides, simple proteins, etc). Eventually, these molecules collaborated together to form the first unicellular beings, the heterotrophs. These heterotrophs depended upon the existing basic molecules like nucleotides to survive. Slowly, the CO2 released by the heterotrophs allowed autotrophs to come into existence. Gradually, through the processes of evolution and natural selection, these primitive life forms, over billions of years, evolved into more complex species and eventually to the most advanced & sophisticated life forms.
It certainly is a long way from the unstable primeval atom and the big bang. To make things clearer I made this simple timeline:
From what I can recall, according to the big bang theory, as proposed by Friedman, about 13.5 billion years ago, the universe started as a (relatively) small primeval atom with an incomprehensibly high temperature, pressure and energy. After the big bang, (only a microsecond later!) the universe had grown in size exponentially and the basic building blocks of matter: protons & neutrons had been formed. The universe continued to expand in size continually. Matter, which was mostly homogeneously distributed throughout the universe, at that time, started clustering together due to gravitational forces of attraction. These clusters then clumped together to form even larger gas clouds, which later gave rise to stars. Stars which constitute the beautiful galaxies we see today in the night sky. One of which is our very own Milky Way.
So let us come closer to home. Let us talk about our own solar system. A long time after the creation of the universe, about 4.5 billion years ago, a supernova i.e. the explosion of a star, in our galaxy, gave rise to a huge cloud of gas, which eventually resulted into the formation of our solar system including the sun, the planets and other heavenly bodies. The (hot and molten) Earth was also formed at about the same time (roughly 4 billion years ago).
The Earth, initially, did not have an atmosphere. As a result, other smaller objects (planetesimals), meteors, which got attracted towards the Earth due to its gravitational pull, received little air resistance and hence fell, right onto Earth’s surface very frequently. However, it was the same meteors that are believed to have brought substances to the Earth which were essential for creation of primitive life. At about this time, the Earth was hit by a large planetesimal, off center. This resulted in a lot of debris thrown out into space. Most of it got attracted back to Earth’s surface. What remained formed Earth’s only natural satellite, the moon. Slowly and gradually the earth began to cool down. The gases released from Earth’s interior formed the initial atmosphere.
And finally, we arrive at the creation of life. About 3.5 billion years ago, the atmosphere consisted mainly of hydrogen, water, methane and ammonia. Electrical discharges of lightening in the atmosphere, radioactivity, etc caused these elements to convert into the basic molecules necessary for life (nucleotides, simple proteins, etc). Eventually, these molecules collaborated together to form the first unicellular beings, the heterotrophs. These heterotrophs depended upon the existing basic molecules like nucleotides to survive. Slowly, the CO2 released by the heterotrophs allowed autotrophs to come into existence. Gradually, through the processes of evolution and natural selection, these primitive life forms, over billions of years, evolved into more complex species and eventually to the most advanced & sophisticated life forms.
It certainly is a long way from the unstable primeval atom and the big bang. To make things clearer I made this simple timeline:
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