Our earth is our home and also the home to several other living and nonliving things present on this planet. In the solar system, it is the third planet, if you count from the sun.
Also, earth is the only planet known which has an atmosphere with free oxygen and oceans and rivers filled with water which is the cause of life.
According to size, it is the fifth largest planet of the solar system, after Jupiter, Saturn, Uranus, and Neptune. It has a diameter of 8000 miles and is spherical. 71% of the surface of Earth is covered by water, most of which is in the oceans and 1/5th of its atmosphere contain oxygen which is produced by plants.
Orbital characteristics of the earth:
Earth rotates around its imaginary axis and revolves around the sun at the same time. It takes earth 23.439 approximately 24 hours to complete one rotation and 365.26 days to complete one revolution. Due to this rotation and revolution, several phenomena such as seasons, eclipse, waves and tides are experienced on earth. Earth has an oval-shaped ellipse like other planets, and that is why it stays closer to the sun in early January and in July it is a bit away. Earth is located in the Goldilocks zone around its star where it is apt to maintain a temperature where liquid water would exist.
Evolution and formation of the earth:
Earth formed around 4.6 billion years ago along with other planets of the solar system. It was formed out of a giant and rotating cloud of dust and gas which is termed as solar nebula. The collapse of the nebula made it spin fast because of gravity and then flattened in the form of a disk. Most of its material went to the center and sun was formed. Other particles collided and got stuck to form planets such as Earth. The solar wind swept away lighter elements and smaller planets. Earth was earlier a waterless rock, and then the radioactive elements within the rock increased pressure and generated heat which melted Earth’s interior. Some of these chemicals formed water and others made the atmosphere.
History of Earth:
History of earth can be divided into four eons, i.e., the Hadean, Proterozoic, Archean and Phanerozoic. The first three eons spanned 4 billion years and are known as Precambrian. Life was found in the Archaen era around 3.8 billion years ago. Life then became abundant in the Phanerozoic era. This era is divided into Paleozoic, Mesozoic and the last and most recent is Cenozoic.
Composition and structure of the earth:
The atmosphere of earth contains 78 percent nitrogen, and almost 21 percent is oxygen while the rest is water, carbon dioxide, argon, and other gases. The lowest layer of our atmosphere is the troposphere which causes the weather. Then there is stratosphere containing the ozone layer above it. Earth has a magnetic field too which is generated by the currents that flow in the outer core of the Earth. Earth’s crust contains oxygen, silicon, iron, aluminum, calcium, potassium, sodium, and magnesium.
Earth is the only planet with life on it, this is because it has oxygen and water. But we are constantly wasting water, and the pollution is depleting the natural oxygen. Also, global warming is continually increasing. If we do not protect our environment and natural resources, then our existence will be endangered.