Fourteen billion years ago the evolution of the present universe as we know it, began. It began with a Big Bang. At that infinitesimal point in time the universe was super tiny, super dense and super hot. Then suddenly, it exploded. Space began to expand and has been expanding ever since. Matter and energy that had remained compacted in a tiny, tiny dot, were suddenly and violently released and scattered across the entire universe in the form of a hot, charged plasma. With time the universe cooled. Particles of matter began to combine in different ways. The first atoms were formed. The simplest atom was hydrogen, the most abundant element in the universe followed by helium. Over time, these gases slowly condensed into gas clouds. In some regions a critical mass was reached. Inside the extremely dense, hot centers of these protostars, hydrogen nuclei began fusing to form helium releasing enormous amounts of energy in the process. The first stars were born. The firmament began to sparkle with starlight. In the high-energy inferno inside large stars, nucleosynthesis led to the formation of more complex elements including carbon, nitrogen, oxygen, phosphorus. The explosions of these large stars seeded the galaxies with the elements necessary for life. Heavier elements were formed during mergers of neutron stars or in exploding super-novae, spewing their contents across the entire cosmos. The gravity of large stars attracted matter that gradually coalesced and started revolving around them trapped in the stars’ gravitational fields. Planets were formed. One such star is our sun and one of the eight planets revolving around the sun is our beloved earth. It was formed 4.5 billion years ago.
Originally, the earth was an amorphous mass of hot, molten magma. Gradually it cooled. Water vapor that had been released from the hot rocks condensed and fell as rain. Oceans and land appeared. There were the elements; hydrogen, nitrogen, oxygen, phosphorus and, most importantly, carbon with its unique chemistry, all abundantly present in the universe, all crucial for the formation of life. These were concentrated in shallow pools at the edge of salty seas. As these pools dried in the hot sun, they became further concentrated. Their proximity and the warmth of the sun caused them to react with one another. Complex molecules arose; nucleotides, amino acids, sugars and fatty acids, the building blocks for nucleic acids, proteins, carbohydrates and lipids. The stage was set for a momentous happening. Dark, massed storm clouds thundered on the horizon. Lightning split the skies. Rain fell in torrents. Mightily the oceans heaved.
And then suddenly, about four billion years ago, from this soup of complex macromolecules, warmed by the sun and stirred by winds, life appeared on earth. At first it was a tiny, inconspicuous blob of protoplasm enclosed by a membrane protecting its precious contents. But it pulsated, grew and replicated itself by splitting into two equal halves, the two daughter cells. These cells, in turn, replicated, again and again. Life had appeared on earth and was off to the races. With time, cells began to utilize photosynthesis using the green pigment chlorophyll to harvest energy directly from the sun to synthesize simple sugars from water and carbon dioxide. These evolved into the green plants and trees we see today. Single cells clumped together to form multicellular organisms. In them, cells differentiated to become neurons, hepatocytes, adipocytes or myocytes giving rise to the organs; brain, liver, fat or muscle, each type very different from the other but each performing specific tasks for the good of the entire organism. Life evolved over a period of four billion years from the simple, single celled animalcule to the enormously complex, integrated life forms of today; the tiny mosquito, the gigantic blue whale, the spreading oak tree and the most intriguing of them all, modern man, Homo sapiens— Man the Wise, with a brain complex enough to contemplate the beginning of the universe and the origin of life. And he continues contemplating and probing, knowing that he is made from the dust of stars, one with the universe and evolving with it.
Featured image above depicts two colliding spiral galaxies. Photo: The Hubble Heritage Team, NASA,ESA