How was the Earth Created
How was the Earth created? How long ago was this third rock from the Sun created? Keep reading to get an answer to these 'down-to-earth' questions!
Earth is our home and perhaps the safest place in our universe. We have no idea, how lucky we are to be here! Earth is the only known planet in our universe, which we know for sure, harbors life. A series of serendipitous events have led to the origin of life on Earth, as we know it.
The odds against creation of our star, the Sun, then our planet Earth and finally evolution of life were so high, that its nothing short of a miracle, that it all happened! I am sure, everyone of us has wondered about how was the earth created, at some point of time, in our life. In this article we will investigate the origin of our world and know how it all happened!
Earth photographed by Apollo 12 (Credit: NASA)
Compared to outer space, this third rock from Sun, our planet Earth is more than a cozy place. It is almost tailor made for life! If you consider all the planet earth facts you will agree with me. To name a few things that make life on earth possible are the abundance of water, a magnetic field blanket (that protects us from high energy solar radiation), an ozone layer and the right mixture of elements in atmosphere, especially oxygen! If you look at all the factors, it is almost like the universe has conspired to create life on Earth! Let us understand how was the Earth created and the chain reaction of circumstances that made its existence possible!
Origin of Earth
How was the Earth formed? This question has bewildered each and every civilization that has existed on Earth. Each of them wanted to know, how was the earth made and they came up with an answer according to their own philosophy and understanding of how the world works. Most of them painted a naive picture, attributing the origin of our planet, to some supernatural being.
However, the most accurate picture of origin of earth, backed by observational evidence was constructed in the 20th century, when the tools of technology that could explore this subject deeply, became available. Let us recount the story put together through years of research in astronomy, geophysics and geology. What follows is a hypothesis that can best describe the observed state of the solar system and our dear Earth. The 'Solar Nebula' theory that I describe here has been indirectly verified through the observation of extrasolar planetary systems (planets revolving around other stars), still in a nascent stage of creation.
It All Started with The Big Bang!
If you really want to know where it all began, you must go way back to the beginning, the origin of the universe itself, the Big Bang theory. That story has been narrated in another article by me, titled, 'How was the universe created?'. We will fast forward from the Big Bang to a time when our galaxy had formed and a third generation star, our Sun was taking shape.
Gas Cloud Collapse
An interstellar Hydrogen cloud began collapsing under its own gravity. The details of how the gas collapsed to form a central hot and dense core which eventually became a star, can be found in the article, 'How was the Sun formed?'. We will focus on the protoplanetary disk which surrounded this central protostar, which eventually condensed to become our solar system.
This cloud of gas and dust contained remnants from previous dead stars and supernovas that enriched it with heavy elements. As the cloud shrank in size, collapsing under gravity, it started rotating. As the cloud rotated, it flattened out. This cloud is called the solar nebula.
As the central bulge of this protoplanetary disk formed the Sun, the surrounding debris of gas and dust started condensing. Consider the whole cloud to be a huge centrifuge. It is not an exact analogy, but close one. When a centrifuge rotates, heavier and more massive elements are thrown outwards. Similarly, heavier elements in the gas cloud were slowly thrown towards the border of the whole disk, just outside the photosphere of the T-Tauri Sun.
Protoplanetary Disk Condensation
About 4.5 billion years ago, Sun started its nuclear fusion engine and officially became a star. At this initial phase, Sun was surrounded by a flat disk of debris. This phase in Sun's life is called the T-Tauri phase (because of an observed star called T-Tauri, which is in this phase just now!).
A graphic illustrating formation of planets from protoplanetary disk (Credit: NASA)
Just as clouds grew through aggregation of water molecules around a dust droplet, matter molecules and atoms in the protoplanetary disk started aggregating to form larger solid objects. These aggregates grew at the rate of centimeters every year.
The region in vicinity of Sun, up till the point where orbit of Mars lies today, was at a very high temperature. So volatile atoms with low atomic weight could not condense in that region. Hence, only heavy metallic compounds (made up of elements with high melting points like (Iron, Nickel and Silicates) condensed in this region. These heavy metal compounds which condensed in inner circle of the protoplanetary disk eventually formed the terrestrial planets (Mercury, Venus, Earth, Mars). Now let us see how was the Earth born from this 'protoplanetary embryo'.
The aggregation continued for about 100,000 years after Sun formed. Once this phase ceased, there were thousands of small planetoids (about 10 km long) that pervaded in the vicinity of the Sun. Over a period of millions of years, they coalesced through collision and condensation to form the terrestrial planets. One such planet which was the aggregation of such small planetoids, created 150 million kilometers away from the Sun, was Earth(rather the proto-Earth).
In the region beyond this high temperature region, which was relatively colder, volatile molecules made up of atoms like Hydrogen, Helium and Methane (which had low atomic weights) condensed. These aggregates of molecules kept growing, swallowing most of the left over Hydrogen and Helium after Sun evolved, becoming gas giants (Jupiter, Saturn, Venus) as we know them today.
As the fraction of heavy elements in the whole content of our solar nebula was quite less compared to Hydrogen and Helium, terrestrial planets like earth are small compared to the gas giants.
Over a period of 100 million years, most of the loose debris and planetoids were either wiped out by the solar wind or they coalesced into the large planetoids forming a solar system which was beginning to look like what it is today.
The Proto-Earth Phase
About 4.54 billion years ago, through accretion of small planetoids, numbering in thousands, an entity which we call proto-Earth formed. Our planet grew through accretion of planetoids and their collisions. This caused generation of a tremendous amount of heat. This combined with an increase in density, led to the melting of all the heavy elements like Iron and Nickel that were contained in proto-Earth's composition.
As our planet was in a molten condition during this time, these heavy elements sank and got concentrated at center of mass of the planet, forming the hot metallic Earth core. This separation of the primitive liquid metal elements, 10 million years after proto-Earth formed is called 'Iron catastrophe'. It created the layered structure of earth, with solid metallic core, liquid metal mantle around it with a solid crust forming later. The iron catastrophe was responsible for creating Earth's magnetic field, generated by the metallic liquid mantle flowing around a solid core.
Whatever we know of the insides of our planet Earth, has been garnered through years of painstaking research in Earth Science.
During this period, Earth was surrounded by an atmosphere, primarily made up of Hydrogen and Helium. This thin envelope was however, blown away by the solar wind.
If you ask me how long ago was the Earth created, then I would say, according to recent research, its age is estimated to be 4.54 billion years. This age has been determined through carbon dating of some of the oldest rocks in Earth's crust.
Giant Impact Created Moon
About 40 million years after the creation of Earth, a giant object about the size of today's Mars (named Thiea) impacted the hot and molten Earth, ejecting a large part of molten material in space, which accreted to create our Moon. This giant impact hypothesis for the creation of Moon is largely accepted due to the similarity in composition of the Moon and Earth's crust and the absence of a liquid metallic core in the Moon.
Earth Cooled to Form a Crust, Atmosphere and Oceans
About 150 million years later, Earth had cooled enough to create a primitive basaltic crust which is not same as the one we have today. Still the magma was a lot hotter than what it is today (at about 1600o C. The first atmosphere was created from gases and moisture that escaped from fractured crust and volcanoes. Water was also derived from millions of impacting planetoids which had ice present on them. They also enriched Earth with compounds like Carbon dioxide, Methane, Nitrogen and Ammonia.
With further cooling, clouds formed on Earth causing the first rains and creating oceans. The earlier basaltic crust was mostly lost due to the bombardment of asteroids. About 500 million years later, the first continental crust formed. These continents drifted on a sea of mantle causing plate tectonics. These continents drifted over millions of years. This was how our world was created.
Origin of Life
With the creations of oceans and enrichment of the atmosphere with gases like Oxygen, Methane and Nitrogen, the stage for arrival of first carbon based life form was set! How did the first unicellular life forms evolve in oceans, is still a matter of research. Evolution of unicellular life to human evolution would easily take tons of books in its description! There is also a debate whether life evolved on Earth or was seeded by impacting asteroids (called the Pan Spermia theory). So I will not dare get into that subject just now. May be I will talk about it in another article.
Hope this article has given you a good idea about how was the Earth created from the Solar Nebula. The future of our planet is closely tied to the fate of the Sun. Still many Earth mysteries remain to be solved like the reason for occurrence of Ice ages, the mechanism behind the creation of Earth's Magnetic field and many more. If some young readers of this article are motivated to explore these mysteries, I would say my job is well done!
The odds against creation of our star, the Sun, then our planet Earth and finally evolution of life were so high, that its nothing short of a miracle, that it all happened! I am sure, everyone of us has wondered about how was the earth created, at some point of time, in our life. In this article we will investigate the origin of our world and know how it all happened!
Earth photographed by Apollo 12 (Credit: NASA)
Compared to outer space, this third rock from Sun, our planet Earth is more than a cozy place. It is almost tailor made for life! If you consider all the planet earth facts you will agree with me. To name a few things that make life on earth possible are the abundance of water, a magnetic field blanket (that protects us from high energy solar radiation), an ozone layer and the right mixture of elements in atmosphere, especially oxygen! If you look at all the factors, it is almost like the universe has conspired to create life on Earth! Let us understand how was the Earth created and the chain reaction of circumstances that made its existence possible!
Origin of Earth
How was the Earth formed? This question has bewildered each and every civilization that has existed on Earth. Each of them wanted to know, how was the earth made and they came up with an answer according to their own philosophy and understanding of how the world works. Most of them painted a naive picture, attributing the origin of our planet, to some supernatural being.
However, the most accurate picture of origin of earth, backed by observational evidence was constructed in the 20th century, when the tools of technology that could explore this subject deeply, became available. Let us recount the story put together through years of research in astronomy, geophysics and geology. What follows is a hypothesis that can best describe the observed state of the solar system and our dear Earth. The 'Solar Nebula' theory that I describe here has been indirectly verified through the observation of extrasolar planetary systems (planets revolving around other stars), still in a nascent stage of creation.
It All Started with The Big Bang!
If you really want to know where it all began, you must go way back to the beginning, the origin of the universe itself, the Big Bang theory. That story has been narrated in another article by me, titled, 'How was the universe created?'. We will fast forward from the Big Bang to a time when our galaxy had formed and a third generation star, our Sun was taking shape.
Gas Cloud Collapse
An interstellar Hydrogen cloud began collapsing under its own gravity. The details of how the gas collapsed to form a central hot and dense core which eventually became a star, can be found in the article, 'How was the Sun formed?'. We will focus on the protoplanetary disk which surrounded this central protostar, which eventually condensed to become our solar system.
This cloud of gas and dust contained remnants from previous dead stars and supernovas that enriched it with heavy elements. As the cloud shrank in size, collapsing under gravity, it started rotating. As the cloud rotated, it flattened out. This cloud is called the solar nebula.
As the central bulge of this protoplanetary disk formed the Sun, the surrounding debris of gas and dust started condensing. Consider the whole cloud to be a huge centrifuge. It is not an exact analogy, but close one. When a centrifuge rotates, heavier and more massive elements are thrown outwards. Similarly, heavier elements in the gas cloud were slowly thrown towards the border of the whole disk, just outside the photosphere of the T-Tauri Sun.
Protoplanetary Disk Condensation
About 4.5 billion years ago, Sun started its nuclear fusion engine and officially became a star. At this initial phase, Sun was surrounded by a flat disk of debris. This phase in Sun's life is called the T-Tauri phase (because of an observed star called T-Tauri, which is in this phase just now!).
A graphic illustrating formation of planets from protoplanetary disk (Credit: NASA)
Just as clouds grew through aggregation of water molecules around a dust droplet, matter molecules and atoms in the protoplanetary disk started aggregating to form larger solid objects. These aggregates grew at the rate of centimeters every year.
The region in vicinity of Sun, up till the point where orbit of Mars lies today, was at a very high temperature. So volatile atoms with low atomic weight could not condense in that region. Hence, only heavy metallic compounds (made up of elements with high melting points like (Iron, Nickel and Silicates) condensed in this region. These heavy metal compounds which condensed in inner circle of the protoplanetary disk eventually formed the terrestrial planets (Mercury, Venus, Earth, Mars). Now let us see how was the Earth born from this 'protoplanetary embryo'.
The aggregation continued for about 100,000 years after Sun formed. Once this phase ceased, there were thousands of small planetoids (about 10 km long) that pervaded in the vicinity of the Sun. Over a period of millions of years, they coalesced through collision and condensation to form the terrestrial planets. One such planet which was the aggregation of such small planetoids, created 150 million kilometers away from the Sun, was Earth(rather the proto-Earth).
In the region beyond this high temperature region, which was relatively colder, volatile molecules made up of atoms like Hydrogen, Helium and Methane (which had low atomic weights) condensed. These aggregates of molecules kept growing, swallowing most of the left over Hydrogen and Helium after Sun evolved, becoming gas giants (Jupiter, Saturn, Venus) as we know them today.
As the fraction of heavy elements in the whole content of our solar nebula was quite less compared to Hydrogen and Helium, terrestrial planets like earth are small compared to the gas giants.
Over a period of 100 million years, most of the loose debris and planetoids were either wiped out by the solar wind or they coalesced into the large planetoids forming a solar system which was beginning to look like what it is today.
The Proto-Earth Phase
About 4.54 billion years ago, through accretion of small planetoids, numbering in thousands, an entity which we call proto-Earth formed. Our planet grew through accretion of planetoids and their collisions. This caused generation of a tremendous amount of heat. This combined with an increase in density, led to the melting of all the heavy elements like Iron and Nickel that were contained in proto-Earth's composition.
As our planet was in a molten condition during this time, these heavy elements sank and got concentrated at center of mass of the planet, forming the hot metallic Earth core. This separation of the primitive liquid metal elements, 10 million years after proto-Earth formed is called 'Iron catastrophe'. It created the layered structure of earth, with solid metallic core, liquid metal mantle around it with a solid crust forming later. The iron catastrophe was responsible for creating Earth's magnetic field, generated by the metallic liquid mantle flowing around a solid core.
Whatever we know of the insides of our planet Earth, has been garnered through years of painstaking research in Earth Science.
During this period, Earth was surrounded by an atmosphere, primarily made up of Hydrogen and Helium. This thin envelope was however, blown away by the solar wind.
If you ask me how long ago was the Earth created, then I would say, according to recent research, its age is estimated to be 4.54 billion years. This age has been determined through carbon dating of some of the oldest rocks in Earth's crust.
Giant Impact Created Moon
About 40 million years after the creation of Earth, a giant object about the size of today's Mars (named Thiea) impacted the hot and molten Earth, ejecting a large part of molten material in space, which accreted to create our Moon. This giant impact hypothesis for the creation of Moon is largely accepted due to the similarity in composition of the Moon and Earth's crust and the absence of a liquid metallic core in the Moon.
Earth Cooled to Form a Crust, Atmosphere and Oceans
About 150 million years later, Earth had cooled enough to create a primitive basaltic crust which is not same as the one we have today. Still the magma was a lot hotter than what it is today (at about 1600o C. The first atmosphere was created from gases and moisture that escaped from fractured crust and volcanoes. Water was also derived from millions of impacting planetoids which had ice present on them. They also enriched Earth with compounds like Carbon dioxide, Methane, Nitrogen and Ammonia.
With further cooling, clouds formed on Earth causing the first rains and creating oceans. The earlier basaltic crust was mostly lost due to the bombardment of asteroids. About 500 million years later, the first continental crust formed. These continents drifted on a sea of mantle causing plate tectonics. These continents drifted over millions of years. This was how our world was created.
Origin of Life
With the creations of oceans and enrichment of the atmosphere with gases like Oxygen, Methane and Nitrogen, the stage for arrival of first carbon based life form was set! How did the first unicellular life forms evolve in oceans, is still a matter of research. Evolution of unicellular life to human evolution would easily take tons of books in its description! There is also a debate whether life evolved on Earth or was seeded by impacting asteroids (called the Pan Spermia theory). So I will not dare get into that subject just now. May be I will talk about it in another article.
Hope this article has given you a good idea about how was the Earth created from the Solar Nebula. The future of our planet is closely tied to the fate of the Sun. Still many Earth mysteries remain to be solved like the reason for occurrence of Ice ages, the mechanism behind the creation of Earth's Magnetic field and many more. If some young readers of this article are motivated to explore these mysteries, I would say my job is well done!
By Omkar Phatak
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