Our Home, The Earth

In this vast emptiness of the cosmos, there is our Solar System somewhere in the Milky Way galaxy and there is only one known planet in the Solar System that is teeming with organic life, The Earth. Approximately 4.5 billion years ago the initial formation of the Earth started along with the formation of the Sun. Stars like the Sun are essentially formed from clouds of gas in space. We know these as nebulas. Over time gravity causes the atoms of gases and space dust to start coming together and gathering. Over time this gather of gases gains more mass and with it stronger gravity. This is a process that can take millions of years. In time the gravity causes the gases, mainly hydrogen to fuse in a nuclear reaction and a star is formed.
The formation of the Earth occurred after this initial phase happened for our Sun. After the Sun was formed we know from observations and other indirect evidence that there were leftover gases and heavier elements. The gravity of the Sun helped to flatten these leftovers into a disk and start to fuse them together which over time formed the present-day Earth. It's the third planet from the Sun.       

Earth during its initial formation process

Segregation of the Earth's Layers and Atmosphere     

The materials that accreted into the early Earth were probably added piecemeal, without any particular order (though some models call on sequential accretion of metallic and then silicate materials). The early Earth was very hot from 1) gravitational compression, 2) impacts, and 3) radioactive decay (much more than today).  The early Earth was probably partially or largely molten. The denser metallic liquids sank to the center of the Earth and less dense silicate liquids rose to the top like oil rises to the surface of the water. In this way, the Earth very quickly differentiated into a metallic, mostly iron core and a rocky silicate mantle.

 

Through igneous (volcanic and intrusive) activity the crust of the Earth eventually formed. The composition of the mantle is silicate. The crust, on the other hand, is more enriched in silica with lesser amounts of iron and magnesium. The high silica rocks of the crust (or rather the assemblage of minerals in crustal rocks) generally have lower density and lower melting temperatures than mantle rocks (minerals).  Crustal rocks formed by partial melting of mantle rocks (melting of the lowest melting temperature, highest silica, minerals in the mantle rocks.  This yields a more silica-rich magma (molten rock) than the mantle rocks.  The magma, being less dense than the rock from which it formed, can rise to the surface, cool, and crystallize.  This general process occurred slowly overtime after the Earth cooled enough that mantle rocks could not melt completely.  Much continental crust, the most silica-rich and least dense kind, had been produced by 2.5 billion years ago.    

The core of the Earth is made up of magma

                                                                                                                                                               

 Formation and Evolution of the Atmosphere

Volatile materials, carried by certain types of meteors and by comets, were added to the Earth by impacts, some of which penetrated the interior.  Gases in the mantle prefer to go into any melt that forms and happily escape into the atmosphere if the melt reaches the surface.  Volcanic activity, especially at the midocean ridges, volcanic arcs, and hotspots, releases large amounts of water vapor, carbon dioxide, and other gases into the atmosphere. Earth's atmosphere today is 78% Nitrogen and 21% Oxygen.

Rotation & Revolution of the Earth           

Earth is a rocky body constantly moving around the sun in a path called an orbit. The Earth and Moon follow a slightly oval-shaped orbit around the sun every year. 

 

Each journey around the sun, a trip of about 940 million kilometers (584 million miles), is called a revolution. A year on Earth is the time it takes to complete one revolution, about 365.25 days. Earth orbits the sun at a speedy rate of about 30 kilometers per second (18.5 miles per second).

 

At the same time that it revolves around the sun, the Earth rotates on its own axis. Rotation is when an object, such as a planet, turns around an invisible line running down its center. Earth’s axis is vertical, running from the North Pole to the South Pole. Earth makes one complete rotation about every 24 hours.

Earth’s rotation causes the periods of light and darkness we call day and night. The part of the Earth-facing the sun is in daylight; the part facing away from the sun is in darkness. If the Earth did not rotate, one-half of the Earth would always be too hot to support life, and the other half would be frozen. Earth rotates from west to east, so the sun appears to rise in the east and set in the west.

Earth has one natural satellite known as the Moon orbiting it.

Till Magellan the explorer set on the sea-expedition to prove that the earth was a sphere, it was widely believed that the Earth was flat.

 

Till almost the middle of last millennium, Earth was thought to be flat

      

The surface of the Earth

The surface of the earth is covered by 70.8% ocean and the remaining 29.2% not covered by water has terrain that varies greatly from place to place and consists of mountains, deserts, plains, plateaus, and other landforms. The abundance of water on Earth's surface is a unique feature that distinguishes the "Blue Planet" from other planets in the Solar System. Earth's hydrosphere consists chiefly of the oceans, but technically includes all water surfaces in the world, including inland seas, lakes, rivers, and underground waters down to a depth of 2,000m. The deepest underwater location is the Challenger Deep of the Mariana Trench in the Pacific Ocean with a depth of 10,911.4m.  

Our Home

Life on Earth

Earth is the only planet in the universe known to possess life. The planet boasts several million species of life, living in habitats ranging from the bottom of the deepest ocean to a few miles into the atmosphere. And the scientists think far more species remain to be discovered.

We need to take care of the planet and all the species living in it. That's the only way we can ensure life continues on Earth.

That's it for now. Stay Safe. Stay Healthy.