Its surface area is covered with two-third of water that is why we call it a blue planet.
Earth is the third planet from the sun, the densest planet in the solar system, the largest of the solar system’s four terrestrial planets.
In size, it is the fifth-largest planet. It is the largest terrestrial planet. The other terrestrial planets are Venus, Mars, and Mercury.
It is slightly flattened at the poles, that is why its shape is described as a Geoid. Geoid means an earth-like shape.
Earth revolves around the Sun, but its average distance from it is 149 million kilometers / 93 million miles. In astronomy, this is 1 AU – or an astronomical unit.
Scientists have researched and estimated that our Earth is around 4.5 billion years old. Earth formed at around the same time as the rest of our Solar System.
Earth revolves around the Sun once every 365.25 days – this is known as one Earth year.
Only 3% of Earth’s water is fresh and 97% of it is salty.
The surface of Earth is covered by water, around 71%, only 29% of Earth’s surface is covered by land.
The atmosphere of Earth is divided into 6 layers – the troposphere, stratosphere, mesosphere, thermosphere, exosphere, and ionosphere.
Earth has only one satellite – the Moon, but it also has a couple of temporal artificial satellites.
Size and Shape of the Earth
Earth is not perfect circle it is an oblate spheroid, it is like a sphere, but the distance from pole to pole is less than the distance around the equator (middle).
The shape of the Earth is called “geoid” that is, ‘an Earth-like shape’.
Earth is bulged out at equator and flattered at poles because of centrifugal force.
The earth spins at constant rate but rate of movement is different the equator is moving fastest and poles are not moving (ignoring the fact that earth is orbiting the sun). Because of this movement centrifugal force is pulling matter closer to equator which structure outwards giving earth slightly non-spherical shape.
Geodesy is the science that studies the shape and size of the Earth.
Earth’s circumference and diameter differ because its shape is classified as an oblate spheroid or ellipsoid, instead of a true sphere. This means that instead of being of equal circumference in all areas, the poles are squished(slightly flattened at the North and South Poles), resulting in a bulge at the equator, and thus a larger circumference and diameter there.
The equatorial bulge at Earth’s equator is measured at 26.5 miles (42.72 km) and is caused by the planet’s rotation and gravity.
Motions of the Earth
Motion is the action or process of moving or of changing place or position.
The Earth is constantly in motion, revolving around the Sun and rotating on its axis. These motions account for many of the phenomena we see as normal occurrences: night and day, changing of the seasons, and different climates in different regions.
The earth has two movements, rotation and revolution.
Rotation- A rotation is a circular movement of an object around a center (or point) of rotation.
A three-dimensional object rotates always around an imaginary line called a rotation axis.
If the axis is within the body, and passes through its center of mass the body is said to rotate upon it, or spin.
Rotation causes days and nights. It takes 23 hours, 56 minutes, and 4.09 seconds for a sidereal day and an exact 24 hours for a mean solar day.
Earth rotates on its axis from west to east(counter-clockwise). The speed of Earth’s rotation is 1,674.4 km/h or 1,040.4 miles per hour at the equator.
The earth has a 23.45° tilt of axis.
While the Earth is spinning on its axis, it is revolving around the Sun in a counter-clockwise direction. It takes the Earth one full year to complete one full revolution around the Sun. This path is known as the Earth’s orbit. The mean distance of the Earth from the Sun is about 93 milling miles and the distance varies by 3 million miles, forming a slightly oval path.
The revolution of the Earth around the Sun traverses a distance of 595 million miles in 365 days, 6 hours, 9 minutes, and 9.5 seconds. This means a speed of 18 miles a second (or 66,000 miles per hour) while at the same time rotating once each twenty-four hours.
