Earth

 

Earth, our home, is the third planet from the sun.  While scientists continue to hunt for clues of life beyond Earth, our home planet remains the only place in the universe where we've ever identified living organisms. 

Earth is the fifth-largest planet in the solar system. It's smaller than the four gas giants   Jupiter, Saturn, Uranus and Neptune  but larger than the three other rocky planets,Mercury, Mars  and Venus.

Earth has a diameter of roughly 8,000 miles (13,000 kilometers) and is mostly round because gravity generally pulls matter into a ball. But the spin of our home planet causes it to be squashed at its poles and swollen at the equator, making the true shape of the Earth an "oblate spheroidOur planet is unique for many reasons, but its available water and oxygen are two defining features. Water covers roughly 71% of Earth's surface, with most of that water located in our planet's oceans. About a fifth of Earth's atmosphere  consists of oxygen, produced by plants.   

Earth Internal Structure

Earth's core is about 4,400 miles (7,100 km) wide, slightly larger than half the Earth's diameter and about the same size as Mars. The outermost 1,400 miles (2,250 km) of the core are liquid, while the inner core is solid. That solid core is about four-fifths as big as Earth's moon, at some 1,600 miles (2,600 km) in diameter. The core is responsible for the planet's magnetic field, which helps to deflect harmful charged particles shot from the sun. 

Above the core is Earth's mantle, which is about 1,800 miles (2,900 km) thick. The mantle is not completely stiff but can flow slowly. Earth's crust floats on the mantle much as a piece of wood floats on water. The slow motion of rock in the mantle shuffles continents around and causes earthquakes, volcanoes and the formation of mountain ranges.

                                                                                                                  

PLANET EARTH'S ORBIT AROUND THE SUN

While Earth orbits the sun, the planet is simultaneously spinning around an imaginary line called an axis that runs through the core, from the North Pole to the South Pole. It takes Earth 23.934 hours to complete a rotation  on its axis and 365.26 days to complete an orbit around the sun  our days and years on Earth are defined by these gyrations.

Earth's axis of rotation is tilted in relation to the ecliptic plane, an imaginary surface through the planet's orbit around the sun. This means the Northern and Southern hemispheres will sometimes point toward or away from the sun depending on the time of year, and this changes the amount of light the hemispheres receive, resulting in the changing seasons.

Earth happens to orbit the sun within the so-called "Goldilocks zone," where temperatures are just right to maintain liquid water on our planet's surface. Earth's orbit is not a perfect circle, but rather a slightly oval-shaped ellipse, similar to the orbits of all the other planets in our solar system. Our planet is a bit closer to the sun in early January and farther away in July, although this proximity has a much smaller effect on the temperatures we experience on the planet's surface than does the tilt of Earth's axis. 

Statistics about Earth's orbit, according to NASA:

• Average distance from the sun : 92,956,050 miles (149,598,262 km)
• Perihelion (closest approach to the sun): 91,402,640 miles (147,098,291 km)
• Aphelion (farthest distance from the sun): 94,509,460 miles (152,098,233 km)
• Length of solar day (single rotation on its axis): 23.934 hours
• Length of year (single revolution around the sun): 365.26 days
• Equatorial inclination to orbit: 23.4393 degrees                                                                                                                                                                                                                                  
  
                     

Additional Resources:-

https://en.wikipedia.org/wiki/Earth

https://books.google.lk/books?id=WVb6Uu9aluYC&dq=earth+planet&hl=en&sa=X&redir_esc=y

https://www.planetary.org/worlds/earth

Earth's core is about 4,400 miles (7,100 km) wide, slightly larger than half the Earth's diameter and about the same size as Mars.

 The outermost 1,400 miles (2,250 km) of the core are liquid, while the inner core is solid. That solid core is about four-fifths as big as Earth's moon, at some 1,600 miles (2,600 km) in diameter. The core is responsible for the planet's magnetic field, which helps to deflect harmful

charged particles shot from the sun.

 

Above the core is Earth's mantle, which is about 1,800 miles (2,900 km) thick. The mantle is not completely stiff but can flow slowly. Earth's crust floats on the mantle much as a piece of wood floats on water. The slow motion of rock in the mantle shuffles continents around and causes earthquakes, volcanoes and the formation of mountain ranges.

Related: Earth's layers: Exploring our planet inside and out

Above the mantle, Earth has two kinds of crust. The dry land of the continents consists mostly of granite and other light silicate minerals, while the ocean floors are made up mostly of a dark, dense volcanic rock called basalt. Continental crust averages some 25 miles (40 km) thick, although it can be thinner or thicker in some areas. Oceanic crust is usually only about 5 miles (8 km) thick. Water fills in low areas of the basalt crust to form the world's oceans.

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.