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About Earth Planet | Solar System


Earth is the third planet from the Solar System and only astronomical object known as harbor life. According to radiometric dating and the other sources of evidence, Earth formed over 4.5 billion years ago. Earth's gravity interacts with the other objects in space, especially the Sun and the Moon, which is Earth's only the natural satellite. Earth orbits around the Sun in 365.26 days, a period known as Earth year.
Earth Image (Source :NASA)

During this time, Earth rotates about its axis about 366.26 times. The composition of the Earth is similar to other terrestrial planets in that it has an iron-core which is surrounded by a molten mantle which, in turn, 
is surrounded by an outer crust. We live on top of the crust. Unlike the other terrestrial planets, Earth’s crust is divided into several separate solid plates
 which float around independently on top of the hot mantle below. The theory that describes this is known as plate tectonics.

Video Soure: National Geographic

Geography of Earth

The earth has seven large land masses called continents. The continents include  Africa, Asia, North America, South America, Europe, Oceania, and Antarctica.

Earth's atmosphere and oceans were formed by volcanic activity and outgassing. Water vapor from these sources condensed into the oceans, augmented by water and ice from asteroids, protoplanets, and comets.
Earth gets warmer toward its core. At the bottom of the continental crust, temperatures reach about 1,800 degrees Fahrenheit (1,000 degrees Celsius), increasing about 3 degrees F per mile 
(1 degree C per km) below the crust. Geologists think the temperature
 of Earth's outer core is about 6,700 to 7,800 degrees F (3,700 to 4,300 degrees C) and that the inner core may reach 12,600 degrees F (7,000 degrees C) — hotter than the surface of the sun.

Internal structure

The outermost 2,200 km of the core are liquid, while the inner core is solid; it's about four-fifths as big as Earth's moon, at some 2,610 km in diameter.
Important changes in crystal structure within the mantle occur at 400 and 659 km below the surface, spanning a transition zone that separates the upper and lower mantle. 
Geography of Earth
Internal Structure of Earth
Beneath the mantle, an extremely low viscosity liquid outer core lies above a solid inner core.
The Earth's inner core might rotate at a slightly higher angular velocity than the remainder of the planet, advancing by 0.1 – 0.5° per year.
The radius of the inner core is about one fifth of that of Earth.


The atmospheric pressure at Earth's sea level averages 101.326 kPa (14.695 psi), with a scale height of about 8.6 km .
A dry atmosphere is composed of 78.085% nitrogen, 20.946% oxygen, 0.935% argon, and trace amounts of carbon dioxide and other gaseous molecules.
The lowest layer of the atmosphere is known as the troposphere, which is constantly in motion and why we have weather. Sunlight heats the planet's surface, 

Atmosphere of earth

causing warm air to rise into the troposphere. This air expands and cools as air pressure decreases, and because this cool air is denser than its surroundings, 
it then sinks and gets warmed by the Earth again.

Earth Statistics

Earth Statistics
Mass (kg)5.976e+24
Mass (Earth = 1)1.0000e+00
Equatorial radius (km)6,378.14
Equatorial radius (Earth = 1)1.0000e+00
Mean density (gm/cm^3)5.515
Mean distance from the Sun (km)149,600,000
Mean distance from the Sun (Earth = 1)1.0000
Rotational period (days)0.99727
Rotational period (hours)23.9345
Orbital period (days)365.256
Mean orbital velocity (km/sec)29.79
Orbital eccentricity0.0167
Tilt of axis (degrees)23.45
Orbital inclination (degrees)0.000
Equatorial escape velocity (km/sec)11.18
Equatorial surface gravity (m/sec^2)9.78
Visual geometric albedo0.37
Mean surface temperature15°C
Atmospheric pressure (bars)1.013
Atmospheric composition


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