U N I V E R S E

  Blog#10

  The Evolution of Earth

 

 

Abstract

      There are trillions of planets in the universe; nevertheless, most of them do not contain life on it. A very few planets have the rare combination of elements that could transformed into such ecosystem that could make a natural environment to sustain the biological and chemical reactions to create lives. We are fortunate to be on this particular planet called mother earth! But the formation of lives on this planet is not done in a short period of time but it was a series of a very complex process that have gradually happened in a very long period of time. We shall try to know a bit about formation and the different phases of the mother planet that could made us as we are today.  

 

 

Introduction

Universe is the void place where all the planets, stars, galaxies exist. The stars are created and destroyed every moment. Every star has its own family, which indeed is composed of planets, comets, asteroids and asteroid belts. Our Sun is also a star having its own family including all the aforesaid. Earth is one of the members of our solar family. It is an exception in this family as it is the only known planet to have extraordinary chemical and elementary composition that confers her the ability to exhibit life on it and own many unique features.

 

 

 

T h e   U n i v e r s e

 

 Astronomy: Science of Earth and the Universe

                                Astronomy is a branch of Science that deals with the creation, development, shape, size, nature, etc. of our universe and its entities. When the human developed to that extent when they became curious to know more about Earth and its structure; Astronomy came into existence, since it can only provide the detailed facts and information about the planet, its neighbors, their origin, the composition, etc. From the very ancient historical time, this subject has been explored. A lot of knowledge and experiments have been attained by the human beings from the subject, which has remarkably, increased the level of our knowledge. Today we are able to understand and have knowledge about the basic concepts of Astronomy, such as its creation and development so far; however, a lot more facts are still to be discovered.

Mainly Astronomy is divided in four parts:

o   Astrophysics,

o   Astrometry,

o   Astrogeology and

o   Astrobiology

 

Cosmology: Science of evolution of Universe

                                The study of Universe its formation, evolution, expansion and destruction, etc are studied under a particular branch of Astronomy called Cosmology. It deals with how the universe led to the star’s galaxies and other features we can observe today.

Basically, we have two ideas available about the creation of our universe.

 A.  Steady State

                                This is a general theory about the creation of universe believed from a long time ago. According to this theory; the universe, static entities and have not much changes in its basic structure. This is an old concept which neither clarifies about the initial creation process of the universe, nor does it clarify about its development or its destruction. This theory was scientifically established by Harman Bondy, Thomas Gold and Fred Hoyle in 1950’s. Then, it was considered to be a perfect cosmological principle. According to this theory, new matters are continuously being created to keep the mean density static at all times as the universe expands. In this theory creation always occurs therefore it is called Continuous Creation Theory.  

 

  B.  The Big Bang Theory

The Big Bang Theory was introduced by Georges Lemaitre in 1966 and Robert Wagoner in 1967. According to this theory, the universe started to create on its own about 15 million years ago. It started with a blast at a pointed energy. This was perhaps known as The Black Hole. It may also be any other source of light and energy. After the blast, the energy spread all around with an angular velocity due to which the energy started rotating anti-clock wise. The energy was spread all around and was forming gases at a very high temperature and on the other hand, it was rotating anti-clockwise on its own axis. The gases spread into a very large area and then started to condense and became relatively cooler. It started forming solid spheres and came closer to the centre point due to its heavy mass and density. The energy was not limited to form only one such sphere. Due to its angular velocity, many such spheres were formed and after getting solidified and cooled down, it slide towards the centre. This was the creation of stars in the rotating arms called Galaxy.

 

 

Our Sun and the Solar System

After the formation of the ‘Galaxy’ which started to form about 15 billion years ago, formation of different and many stars started.  It was due to compression of gases and matters contained by Milky Way as the temperature of this atmosphere came down up to 4,000 degree Celsius and compressed due to the angular rotation energy of the entire galaxy anti-clock wise. After compression of the particles, gases/solid bodies started to be formed and started sliding towards the center of the galaxy due to its increasing mass. This was the first phase of creation of a Star, and this was how our Sun came into existence; all these happened about four billion years ago.

 

Our Solar Family:

About four billion years ago, the sun created its own family of planets and other entities. About 130 million years ago, our earth and the other planets were formed with their satellites. The solar family consists of Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. However, Pluto has been removed from the list of planets and now it is considered as a dwarf planet. We shall come to know more about the planets and the removal of Pluto from the list of planets in the upcoming chapters.

 

 

Our Planet: The Mother Earth

Name of the mother planet:

The word ‘earth’ has its origin in English and German words, both means ‘ground’. This is the only planet that is not named after any Greek or Roman God or Goddess, but no one knows who named it!

Let’s discuss about her formation…

    1. The Mother Earth

Earth: The Special Planet

The Earth is the third planet from the Sun, which comes between Venus and Mars. It is a very special planet, not only because it is our home but also for other reasons as well. It is the only planet in the solar system known to support life. In fact, it does not only support life, but is also a home to millions of different forms of life called biodiversity. This is the only planet made with twenty one per cent of oxygen in its atmosphere and has liquid water on its surface which accounts to seventy one per cent of surface, covered with salty ocean water. In addition, it is the only inner planet known to have a big satellite, the Moon. The Earth is the densest planet in the Solar System.

 

Earth: The ‘Goldilocks’ Planet

If you have read the story of ‘Goldilocks and the Three Bears’, you will know that Goldilocks is characterized as a small girl in the story, who wanted everything to be just perfect. She didn’t like things which were too hot or too cold neither too hard nor too soft. The Earth is sometimes referred as a Goldilocks Planet, as it is just perfectly suited for life. It is neither too hot nor too cold, neither too wet nor too dry. Today, the term ‘Goldilocks Planet’ is used for any planet that is suitably far from any star to support life. But unfortunately, there has been no discovery about any such planet that could support life.

 

Earth: The Blue Marble

If the earth is looked from outside space, it looks like a ‘blue marble’. This term came into use after a photograph of the Earth was published by the crew of Apollo 17 mission in December 1972. In this photograph, the Earth appears like a blue marble with swirl of Yellow, Brown, Green and White. The Blue Color comes from the water covering the surface of the Earth. The Yellow, Brown and Green are the land masses whereas the white comes from the clouds in the atmosphere.

 

Earth: The Different Parts

Air, Water, Land and Life…. these make up the Earth, this beautiful planet which is our home. The air is a mixture of gases which mainly includes Nitrogen and Oxygen which are crucially needed for life. Land is made up of plains, valleys, deserts, mountains. It includes the regions below its surface that is made up of rocks and metal. Water available in both forms, salty as well as fresh water. Salty waters are mainly found in Oceans and Seas while the sources of fresh water are found in the rivers and streams, lakes and ponds etc. Rain, snow and ice are the types of precipitation which occur from the atmosphere.

 

Earth: The Clock

If we consider the entire history of Earth to be a clock of twenty four hours, then at what point of the time would had human beings evolved? The answer is precisely at 11:58:43 p.m. to understand why we came late to this extent of time, we must know the time at which life started its journey at this beautiful Earth with millions of animal species. The answer is, it’s at 4 a.m. the life began on. Outstandingly, at 10:56 p.m. the mighty dinosaurs appeared who ruled over the earth for several centuries.

 

 

2.    History of Earth

Earth: It’s Formation

Our Earth is a part of the solar system which was formed from the gaseous clouds and dust that remained after the Sun was formed around 4.6 billion years ago. The Earth itself started to take shape around 4.6 billion years ago. Some of the dust, pieces of rock and gas particles which were orbiting the Sun smashed against each other and began to heat up until the entire mass melted. As the mass grew, it began large enough to create its own magnetic force and gravity. The force kept the materials safe from flying off into the space again. It also attracted more materials, until the area around became free of debris and the Earth started to get its shape. Some materials in this mass that were heavier than others fell towards the center of the mass to become the Earth’s core. The rest formed the planet’s mantle, crust and atmosphere according to their masses and density. All the planets in this solar system were formed in this manner.

 

Earth: The Initial Stages

The period during which the earth was formed at around 4.6 billion years ago, is referred as the Precambrian Period. In the beginning, our planet was a giant, red, hot, boiling sea of molten rocks. Gradually, the Earth began to cool, and a thin crust appeared on its surface, Though, the core remained red hot. As the cooling progressed, water vapors formed and it escaped into the atmosphere; and then, these water vapors condensed and cooled to form clouds. The clouds led to rain and soon storms started raging over the planet, still cooling the surface of the Earth and causing floods. The floods caused to the formation of oceans and seas. 

 

Earth: The Beginning of Life

The first forms of life on Earth were primitive, single celled organisms, like bacteria which appeared about 3 billion years ago. Multi cellular life began a billion years later, and it’s only in the last 570 million years that the kind of life forms we are familiar with began to evolve. The first of these were the Arthropods or soft bodied worm like creatures that lived in the seas, followed by the fish which lived in the oceans. Some marine animals crawled to the shore and gradually became amphibians and terrestrial animals. Aquatic plants evolved into land plants which later turned into forests. Mammals evolved only 200 million years ago, and the early man only six to two million years ago. Hence, humans have been for a simply for 0.004 per cent of the entire Earth’s history!

 

Discovering Shape of the Earth

The shape of the Earth has fascinated scientists and philosophers throughout the history. The idea that the Earth is spherical originated in ancient Greece, and the oldest reliable sources credit Pythagoras from the 6^th century BC. Aristotle, the Greek philosopher, also argued that the Earth is spherical. He based his belief on the fact that different stars are visible in different locations. He also observed that the shadow of Earth on the Moon during a lunar eclipse is round, and argued that this proves that the shape of the Earth must be round too. The first person to prove a spherical Earth was a Portuguese Explorer- Ferdinand Magellan, whose expedition circumnavigated the globe in 1522. Wretchedly, Magellan died before reaching the end of his journey. The likely theory has been suggested and practiced in the Indian civilizations from very long ago which could be seen in our culture, customs and paleography. The theories are based on the science of astronomy and complex mathematics given by the Rishis, long ago in our history.

 

 

3.    The Supercontinents

Pangaea

Millions of years ago, the movements of these plates over the Earth’s rocky shell or mantle, brought land masses into collision with each other. The collision was so violent that mountains were formed as the existing continents smashed together to form one giant supercontinent. About 300 million years ago, during the time of the dinosaurs, Earth did not have seven continents, However, it had one massive supercontinent called Pangaea.  

 

Gondwana

Gondwana was an ancient supercontinent that was named after the Gondwana region of Central Northern India. The name is derived from Sanskrit for ‘forest of the Gonds’. Gondwana was formed when Pangaea broke up. About 280 million to 230 million years ago, Pangaea started to split up. Magma from below the Earth’s crust began pushing upward; creating a fissure between what could become Africa, South America and North America. As part of this process, Pangaea cracked into northernmost and southernmost continents. The southern continent came to be known as Gondwana. Gondwana stretched from South Pole to the equator. Nevertheless, the climate was warmer that time; Gondwana had temperate trees, with several species of dinosaurs, birds, reptiles and amphibians, which ran through its undergrowth. Gondwana itself eventually split into land masses, which we recognize today as Africa, South America, North America, Antarctica, Australia, Arabian Peninsula as well as the Indian Subcontinent.

 

Laurasia

Laurasia is the name made by combining two names of Laurentia and Eurasia, which is given to the large land of or the northern supercontinent that is too formed after the split of the Supercontinent of Pangaea. It includes most of the continents in the northern hemisphere such as Asia except India, Europe and North America. This supercontinent was dominated by conifers as well as other ferns and seeding type plants. At first, Laurasia was largely located in the equatorial latitudes. Later, it began to break up, with North China and Siberia drifting into latitudes further north.

 

Panthalassa

It was the name given to the vast ocean that surrounded Pangaea, when that supercontinent was there in existence. In fact, the word Panthalassa means ‘all the seas’. Currents in the Panthalassa would have been simple and slow and the earth’s climate would have been warmer than today it is. After the separation of Pangaea into Gondwana and Laurasia, the Tethys Sea formed between both of the supercontinents. It also became a dwelling and breeding place for many unique marine animals and shallow water dwellers.

 

 

        4.      Earth Through the Ages

Precambrian: A Milestone in Geological History

Our mother Earth reached its present size, more or less, between four and 5 billion years ago. The known history of the Earth is subdivided, where the largest defined unit of time is the super eon, composed of eons. Eons are divided into eras, which are in turn into periods epochs and ages. The Precambrian is the largest span of time in Earth’s history before the current Phanerozoic Eon, and is a super eon divided into several eons of the geologic time scale. It spans from the formation of Earth about 4.6 billion years to the beginning of the Cambrian Period, about 541 million years ago, when the hard shelled creatures first appeared. The Precambrian accounts for eighty-eight per cent of geologic time. However, only a little number of facts and information has been discovered about the Precambrian in comparison to the other Ages. The term Precambrian is recognized by the International Commission on Stratigraphy as a general term including the Archean and Proterozoic eons.

 

Paleozoic Era

The Paleozoic Era is a part of Phanerozoic Eon. It lasted 325 million years, from 570 million years ago, to about 245 million years ago. There are several events that took place in this eon that it has been divided into seven geological time periods. During this era, the Earth’s interior cooled down to some temperature like that of the modern levels. As a result, volcanic activity was more or less as the same of today, with few exceptions of some gigantic ‘hot spot’ like eruptions that occurred every hundred million years or so. Plate tectonics continued to push the land masses across Earth’s surface. The composition of the air became similar to what we breathe today. The air was now capable of supporting large species of animals.

        5.    The Historical Theories on Earth

The Earth is flat

In the western world, it was believed that the Earth is flat till a few centuries ago. The flat earth theory states that the earth is flat instead of sphere. Some of the early philosophers believed that the Earth was flat and resting on any sort of foundation, while others claimed that the Earth was floating on air. However, as early as the fourth century BC, philosophers and scientists realized that the Earth was actually a sphere. This debate has raged on in many cultures through the centuries.

 

The Earth is center point of the Universe

In the early civilizations, ancient scientists observed the movements of the Sun and the stars in the sky, and reached a false conclusion. They wrongly believed that the Earth remaining still is the center of the Universe and the entire heavenly bodies orbit around it! This theory was known as the Geocentric Theory (geo means earth).

 

 

        6.      The Fate of the Earth

The Fate of Earth is Depended on the Sun

It is the Sun that will decide the future of the Earth. The Sun is slowly expanding and brightening, and over the next few billion years, it will eventually dry out the Earth. The Earth will be left dry and uninhabitable. About 7.6 billion years from now, the Sun will reach its maximum size as a red giant. In its final stage, the Sun will collapse as a white dwarf. But before this final stage, when the sun becomes a red giant, a simple calculation would put its equator beyond Mars. This means that the inner planets, including Earth may be swallowed by the Sun. But the scientists say that as the Sun will grow, it will lose its mass and it will cause the planets to spiral outwards. Now, a question arises over here, that will the expanding Sun overtake the planets spiraling outwards or will the Earth escape its grasp? Well, the scientists are still debating on this point.

 

What are the Chances for another Mass Extinction?

In the last half billion years, life from Earth has been wiped out five times, causing mass extinction. This happened for things such as- climate change, an intensive ice age, volcanic eruptions, and the space rock that hit and smashed into the Gulf of Mexico, around 6 million years ago, obliterating the dinosaurs and several other species. Now it seems that we are facing another mass extinction, and this time it will be caused by the human beings. Studies have shown that the current extinction rate of some of the species is almost 100 times the normal rate. Actually, that is only taking into accounts the kinds of animals we know the most about. The Earth’s oceans and forests host numerous number of species, many of which would probably disappear before we could get to know about them. Most probably, the reason for the extinction of animals is due to the global warming, caused by human beings. Nevertheless, it is not the one and only answer to be accurate. Other events can also occur. Comets or any asteroid may crash and smash with the Earth, as it has happened earlier and brought a huge mass extinction, or stars may explode. Anything may happen, but we do not have any possible control over any of these catastrophes that may bring huge mass extinction. Hopefully, for the next thousands of years, this mass extinction will not happen.

 

Conclusion:

Till today, scientists have not able to find any single planet which could support life on it, such as our mother Earth does, neither in our solar system nor beyond it in the whole universe. However, It is hard to say that there is no other Goldilocks Planet. The history of our Earth is very complex and rich, its detailed study shall provide us numerous data to save our lives and grow as well.

Our home planet and its environment is facing a lot of problems today and this problem is not occurred naturally but the human beings i.e. we are the cause for this crisis. Our greed and unnecessary ambitions have made the entire planet struggle along with all the other species living here.

 

 

           Total Words: 3650 Approx.

Sources of Data:

Wikipedia

Space.com

Amnh.com

Study.com

Science.nasa.gov

Google and other websites

Orient Blackswan School Atlas

Manorama TELL ME WHY EARTH 

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