Earth | the third planet from the Sun in the Solar System

Author: Leandro Alegsa Creation date: November 13, 2022

Earth is the third planet from the Sun in the Solar System. It is the only planet known to have life on it. The Earth formed about 4.5 billion years ago. It is one of four rocky planets on the inner side of the Solar System. The other three are Mercury, Venus, and Mars.

The large mass of the Sun keeps the Earth in orbit through the force of gravity. Earth also turns around in space, so that different parts face the Sun at different times. Earth goes around the Sun once (one year) for every 365¹⁄₄ times it turns around (one day).

Earth is the only planet in the Solar System that has a large amount of liquid water on its surface. About 74% of the surface of Earth is covered by liquid or frozen water. Because of this, people sometimes call it the blue planet.

Because of its water, Earth is home to millions of species of plants and animals which need water to survive. The things that live on Earth have changed its surface greatly. For example, early cyanobacteria changed the air and gave it oxygen. The living part of Earth's surface is called the "biosphere".

Etymology

The Common Germanic noun earth in Middle High German, in Old High German erda, is based on er- with related words of other Indo-European languages.

Orbit

→ Main article: Earth's orbit

According to Kepler's first law, the Earth moves in an elliptical orbit around the Sun. The sun is located in one of the foci of the ellipse. The major axis of the ellipse connects the point farthest from the Sun and the point closest to the Sun in the orbit. The two points are called aphelion and perihelion. The mean of the aphelion and perihelion distance is the length of the major semi-major axis of the ellipse and is about 149.6 million km. This length originally defined the astronomical unit (AU), which is the astronomical unit of length used mainly for distances within the solar system.

The aphelion is 1.017 AU (152.1 million km) and the perihelion is 0.983 AU (147.1 million km). Thus, the ellipse has an eccentricity of 0.0167. The aphelion transit occurs around July 5 and the perihelion transit occurs around January 3. The Earth orbits the Sun in 365 days, 6 hours, 9 minutes, and 9.54 seconds; this period is also called the sidereal year. The sidereal year is 20 minutes and 24 seconds longer than the tropical year on which the civil year of calendar reckoning is based. The Earth's orbital velocity is 29.78 km/s on average, 30.29 km/s at perihelion, and 29.29 km/s at aphelion; thus, the Earth covers a distance the length of its diameter in just over seven minutes.

Earth's orbit is distant from Venus' inner neighboring orbit by an average of 0.28 AU (41.44 million km) and from Mars' outer neighboring orbit by an average of 0.52 AU (78.32 million km). However, Mercury is closest to Earth on average (1.039 AU). There are several coorbital objects in Earth's orbit, for more details see: Earth's orbit.

The Earth orbits the Sun prograde, that is, in the direction of the Sun's rotation, which is counterclockwise as viewed from the north pole of the Earth's orbital plane.

The Earth's orbital plane is called the ecliptic. The ecliptic is inclined by a good 7° to the equatorial plane of the sun. The north pole of the sun faces the earth most strongly towards the beginning of September, the south pole of the sun towards the beginning of March. The earth is in the sun's equatorial plane only briefly around June 6 and December 8.

Questions and Answers

Q: What is the third planet from the Sun in the Solar System?

A: The third planet from the Sun in the Solar System is Earth.

Q: How long ago did Earth form?

A: Earth formed about 4.5 billion years ago.

Q: What are the four rocky planets on the inner side of the Solar System?

A: The four rocky planets on the inner side of the Solar System are Mercury, Venus, Earth and Mars.

Q: How does gravity keep Earth in orbit around the Sun?

A: The large mass of the Sun keeps Earth in orbit through its force of gravity.

Q: How often does Earth go around once around sun and turn around itself?

A: Earth goes around once (one year) for every 3651⁄4 times it turns around (one day).

Q: What percentage of earth's surface is covered by liquid or frozen water?

A: About 74% of earth's surface is covered by liquid or frozen water.

Q: What is living part of earth's surface called?

A:The living part of earth's surface is called "the biosphere".