Earth is the ONLY heavenly body known to host life. It is the third planet from the sun and fifth largest planet of the Solar system. Earth is most unique as it has an atmosphere with oxygen and oceans which sustains life. It is also the only planet which has not been named after some Roman or Greek God.
Interesting Earth Facts
- The Earth is the third planet from the Sun.
- The Earth is the only planet known that has conditions suitable for life.
- Earth’s surface is mostly covered by water i.e. approximately 70%.
- The Earth has one natural satellite i.e. the Moon.
- It has a diameter of the planet is 12,756 km.
- In the old times, it was believed that the Earth was the center of the universe and all the stars and planets revolved around it.
- It is the densest planet in the Solar system.
- The Earth is the only planet that has not been named after a god.
- The Earth takes 365.26 days to revolve around the sun and it’s period of rotation is approximately 24 hours.
- It is the fifth-largest planet in the solar system.
- It is the biggest of the terrestrial planets.
- Light takes about 8 minutes to reach the surface of the Earth from the Sun.
- Earth is the only planet to have just one moon.
- Earth has no rings.
History
Being the only planet inhabited by human beings, the Earth holds a long and detailed history of billions of years. Earth has formed about 4.54 billion years ago. It was formed along with the solar system. Life began on Earth around 3.8 billion years ago. Several theories had been put forward about the Formation and Life on Earth.
Many of the theories suggested that the Earth was flat or that the Earth was the center of the universe and all the planets, stars and the sun revolved around it. The name of our planet is around 1000 years old. It is a German word which means ‘the ground’.
About Earth
The Earth is 150 million kilometers away from the sun. The distance between the Earth and the sun is termed as one astronomical unit or 1 AU. The Earth’s axis is tilted at about 23.5 °. Hence, we experience seasonal variations continuously. The Earth takes approximately 24 hours to rotate and about 365 days to revolve around the sun.
Appearance
The Earth mostly appears blue from space. This is because 70% of the Earth’s surface is covered by water, 97% of which belongs to the oceans. In fact, the Earth is the only planet to have water on its surface. From space, everything else that is visible other than water is the Earth’s continents polar caps and clouds. The pattern of the clouds on the Earth’s surface keeps on changing continuously.
Size
The diameter of the Earth is approximately 6,370 km. The shape of the Earth is a geoid. The planet is a bit flattened at the poles and the part near the equator bulges out. The Earth’s mass is approximately 5.97×1024 kg, which is mainly iron, oxygen, silicon, magnesium, and sulphur.
Surface
Earth has a lot of variations in its surface. It contains mountains, oceans, volcanoes, plains, etc. The Earth’s crust is divided into several plates called the tectonic plates which are continuously moving. It is believed that at one point in time, instead of seven continents, the Earth only had one supercontinent called Pangea.
The tectonic plates of Pangea slowly drifted apart over the years and formed the map of the world as we know today. This phenomenon is called continental drift. These same plates collided to form mountains and trenches. When two plates rub against each other, earthquakes are caused.
The tallest mountain on Earth is Mauna Kea. However, Mt. Everest is considered the tallest as most of Mauna Kea is under the ocean.
Composition
Earth is mainly composed of iron, silicon, oxygen, sulphur, magnesium, and various other elements. The atmosphere of the earth mainly comprises of nitrogen (78%), oxygen (21%) and other gases. The internal structure of the earth is as explained below.
Earth is a terrestrial planet. It consists of mainly four main layers which are:
- Crust: The crust is the outer most layer. It is also the thinnest of all the layers. On average, it is about 5 km thick.
- Mantle: Above the outer core comes the mantle which is the thickest layer. It mainly contains molten rocks and is 3,000 km thick on average.
- Outer core: After inner core comes the outer core which is about 2,300 kilometers. It is also made up of iron and nickel.
- Inner core: The inner core mainly comprises of iron and nickel and can have a temperature of nearly 10,000°C. The inner core has a radius of 1,221 kilometers.
Magnetic Field
The Earth is one of the four terrestrial planets along with Mercury, Venus, and Mars. Because of the rapid rotation of the Earth and its high iron and nickel content, there exists a strong magnetic field on the Earth. It is because of the magnetic field that a compass needle points towards the north.
The reason for the earth’s magnetism is the generation of conventional currents due to differences in composition, temperature, and pressure between the inner and outer core. A flow of liquid iron generates an electric current which in turn gives rise to a magnetic field. Thus, the earth has a strong magnetic field.
It is believed that these poles reverse every 400,000 years. This means than when a reversal takes place, the compass needles will point south instead of north. However, life on Earth will not be affected by the reversal of magnetic poles. As the Earth is not a perfect sphere, gravity on Earth also varies from place to place.
Orbit and Rotation
The Earth takes approximately 24 hours to rotate about its own axis and about 365 days to revolve around the sun. The time taken by the earth to revolve around the sun once is called an Earth year which is actually a period of 365.25 days or 365 days and 6 hours. However, we do not take into consideration the 6 hours for our convenience and instead add an extra day to the year, every four years i.e. 24 hours. This is called a leap year which consists of 366 days with one more day added to the month of February.
The revolution of the earth is also the cause of seasonal changes every few months.
The Earth is 150 million kilometers away from the sun. The distance between the Earth and the sun is termed as one astronomical unit or 1 AU.
Atmosphere
The Earth’s atmosphere comprises of several layers of gases. This layer of gases is commonly referred to as air and it surrounds the entire planet. The most abundant gas in the atmosphere is Nitrogen which comprises about 78% of it. Oxygen, the second most abundant gas covers approximately 21% of the atmosphere. Other gases present here include argon and carbon dioxide.
The atmosphere of Earth plays a major role in the survival of living things. This is because the atmosphere contains several gases like oxygen and carbon dioxide vital for the survival of plants and animals.
The atmosphere also helps in regulating the temperature on the planet by displaying the greenhouse effect and keeping the planet warm. It also absorbs the sun’s harmful ultraviolet rays and does not let them reach the surface. The 5 main layers of the atmosphere are as follows:
Exosphere
It stretches from 700 to 10,000 km above the Earth’s surface. It is the uppermost layer of the atmosphere. It is the least dense of all layers.
Thermosphere
It stretches from 80 to 700 km above the Earth’s surface. There are a lot of variations in this layer because of solar activities. In the lower part of this layer, there is a layer called the ionosphere which plays a part in atmospheric electricity.
Mesosphere
It goes from 50 to 80 km from the Earth’s surface. It is the coldest layer of all with an average temperature of -85°C. Mesosphere is the coldest place on Earth.
Stratosphere
It goes from 12 to 50 km above the Earth’s surface. This layer contains an important layer called the ozone layer. The ozone layer absorbs the incoming ultraviolet rays from the sun and does not let it reach the Earth’s surface.
The conditions on Earth would be extreme for without this layer. However, in recent times, this layer is slowly depleting due to human activities and emission of harmful gases like chlorofluorocarbons (CFCs), nitric oxide (NO), etc.
Troposphere
It is 0 to 12 km away from the surface. This is the lowest layer in the atmosphere and also closest to the Earth. It mainly contains water vapors.
Moons & Satellites
The Moon is the Earth’s only natural satellite. It is believed that the moon is 4.5 billion years old. It was formed soon after the Earth’s formation. The moon takes 27.3 days to revolve around the Earth. Its size is about 1/8 the size of the Earth. The distance between the Earth and the moon is around 3,60,000 km.
Earth also has a large number of artificial satellites. The Soviet Union’s Sputnik 1 was the first artificial satellite in the world. More than 8000 satellites by over 40 countries have been launched since then. Today, close to 4,900 satellites are currently orbiting the Earth out of which about 2000 are active.
Life on Earth
Earth is the only known planet to have life. In other words, Earth is the only habitable planet known to mankind. The origin of organisms is not known in detail, but the most widely accepted theory is that all of the organisms on Earth today have evolved from one organism over the course of millions of years.
Earth is habitable because its conditions are perfect for life. Water on the surface of the earth, a blanket of air around i.e. the atmosphere and the planet’s distance from the sun which is neither too small nor too big and the suitable temperature has made life possible on Earth.
These satellites are mostly used for the purposes of communication, observation of Earth, technology, navigation, positioning, space science, and Earth science. They are used for commercial use, military use, government use, and civil use as well.
Pollution on Earth
Pollution is defined as the contamination of natural resources due to the release of harmful material into the environment. There are several types of pollution. Like – air pollution, water pollution, soil pollution, etc.
Pollution on Earth is a major problem. As the population of the planet is increasing, the demand for resources and the exploitation of resources is increasing rapidly. This means that the release of toxic chemicals and other harmful substances is also growing.
Some more factors that contribute to pollution are deforestation and the construction of concrete jungles.
The three main types of pollution are explained as follows:
Soil pollution/land pollution
Soil gets polluted because of the improper disposal of plastic or other non-biodegradable material, the use of harmful pesticides and insecticides in agriculture, the release of factory waste on land, etc.
Millions of tons of waste are dumped on the land every year. This results in degradation of the soil and lack of nutrients for trees and plants. This is, however, one of the many consequences of soil pollution.
To check soil pollution, several steps need to be taken. One of them includes making compost out of biodegradable material and recycling of non-biodegradable material.
Water pollution
Water pollution is caused by the dumping of waste in water bodies like lakes, rivers or oceans or releasing harmful chemicals by factories. Water pollution adversely affects aquatic life but at the same time, affects life on land too. Water pollution leads to the death of aquatic organisms and the pollutants do not allow decay. This leads to the water being polluted further.
Most human households get water from nearby water bodies. This means that if polluted water reaches human households, it will become a hazard to their health. On a small scale, it can be checked by controlling the disposal of oil, grease that is insoluble in water or reducing the use of pesticides and insecticides that may wash into rivers or lakes.
On a large scale, factories can play a major role in controlling water pollution by treating liquid waste before releasing it into water bodies.
Air pollution
Air pollution is caused by the release of harmful gases like carbon dioxide, nitric oxide, sulphur dioxide, etc. into the atmosphere. It is mostly caused by smoke released by vehicles, factories and sometimes natural causes like forest fires or volcanic eruptions. Human activities like deforestation also add further to air pollution.
Air pollution leads to the contamination of air which causes lifestyle and respiratory diseases in human beings. Polluted water and air also lead to acid rain which is harmful to the soil and the water. Air pollution also leads to Ozone depletion.
According to recent studies, a huge ozone hole has been formed over the continent of Antarctica, mainly because of pollutants like CFCs. The ozone layer protects organisms on Earth from the sun’s harmful ultraviolet rays.
The depletion of this layer will lead to an increase in the Earth’s temperature and also an increase in skin diseases. Global warming is also a major cause of concern. It is caused when chemical molecules like carbon compounds trap the sunlight and do not let it escape the Earth’s atmosphere.
This results in an overall rise in the temperature of Earth. Due to this, the ice caps in glaciers are melting. If this continues, the sea levels on Earth will rise rapidly and will lead to submergence of land.
Air pollution can be checked by more use of public transport and filtering of factory smoke and planting more trees. All in all, there is a need to conserve natural resources and put a stop to pollution, deforestation, and over-exploitation.
Timeline of the Earth’s Geological History
- 4.6 to 4 billion BC: Earth is formed
- 4.5 billion BC: The moon is formed
- 2.5 billion BC: The earth begins to cool down
- 1 billion BC: First signs of life on earth (single-celled and aquatic organisms)
- 1 billion to 500 million BC: formation of the atmosphere
- 250 to 65 million BC: Age of dinosaurs and reptiles
- 65 million BC to present: Age of mammals and humans
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