Earth
Overview
Earth is the third planet from the Sun, and it is the largest of the four inner planets that are made of rocks and metallic substances. The name earth comes from an English/German word which means ‘the ground’.
Earth seems to be the only planet that (we know of) supports life in the solar system. Liquid water covers 66% of its surface. Hospitable temperature, vast oceans, and the availability of required chemical ingredients enabled the beginning of life 3.8 billion years ago. Though science has made incredible accomplishments, the origin of life on Earth still remains a mystery.
But one thing is clear. The rarest of all the rare incidents that happened in the solar system (may be, in the Universe) is the beginning of life on our Earth. A chain of most improbable coincidences had led to the beginning and the subsequent evolution of life. Eventually, it resulted in intelligent life on Earth.
It is apparent that our planet’s environment is unique, and that life, which took billions of years to evolve, is extremely precious. So, it is everyone’s responsibility to protect Earth’s unique environment and to help nature sustain life on Earth.
Interesting Facts
Moon: As we know, Earth has one moon. Our Moon causes tidal waves in the oceans and also stabilizes the tilt of the Earth. Because of the fixed tilt, the climate and seasons on Earth stay stable over a lengthy period of time (in cosmic timescale). Without the Moon, life on Earth perhaps never started at all.
Moon’s Origin: While the two terrestrial planets Mercury and Venus do not have any moon orbiting them, Mars has two miniscule objects which are really captured asteroids. How did it happen that our Earth has such a massive Moon? What is the origin of our Moon? Astronomers believe that out Moon formed because a Mars-sized object collided with Earth when it was young.
Have you ever wondered why we always see the same side of the Moon? If you would like to read more on why we always see the near side of the Moon, please read this.
Atmosphere: Earth’s atmosphere consists of nitrogen (78%), oxygen (21%), and other gases (1%) including carbon dioxide. The atmosphere, along with Earth’s strong magnetic field, acts as a shield to protect life from all the elements of cosmos.
Size: It has a radius of 6371 kilometers, and it is the largest of the four inner planets closest to the Sun.
Orbit: The orbit of Earth around the Sun is almost circular with a mean distance of about 150 million kilometers from the Sun. The average distance between Earth and the Sun is known as an Astronomical Unit (AU). Astronomers sometimes use AU to specify the distance between celestial objects.
Earth takes 365.25 days to orbit the Sun, and its tilt is 23.4 degrees from the plane of its orbit. This tilt is responsible for the yearly cycle of seasons.
References:
- The Cambridge Guide to the Solar System by Kenneth R. Lang, Cambridge University Press.
- https://solarsystem.nasa.gov/planets/earth/in-depth/