Earth

**Earth** (often referred to as "the earth" and in Latin known as Tellus) is the third furthest planet from the Sun in the Solar System. Even though researchers are still looking for signs of extraterrestrial life, Earth is still the only planet where life has ever been found. The solar system's fifth-largest planet is Earth. It is bigger than the three other terrestrial planets, Mercury, Mars, and Venus, but smaller than the four gas giants, Jupiter, Saturn, Uranus, and Neptune. The majority of Earth is round, with a diameter of 12,742 kilometers, as mass is typically drawn into a ball by gravity, However, because of the way our planet spins, it gets compressed at the poles and expanded at the equator, giving Earth its actual shape as a "oblate spheroid."

Earth formed 4.5 billion years ago. It is the most dense planet in the solar system and also the largest terrerestiral planet in the solar system. Earth has an atmosphere composed of nitrogen, oxygen, and argon. Water vapor is highly present in the atmosphere and forms clouds that cover most of the planet, contributing to the water cycle. The Moon is tidally locked to Earth, which causes lunar tides and helps to stabilize Earth's axial tilt.

## Motion

Earth has two motions: it rotates on its axis and it orbits the sun. The axis is an imaginary line that runs through the planet's center. The Earth takes 23.934 hours to rotate on its axis, which is why we have a day and night cycle. The Earth takes 365.26 days to orbit the sun, which is why we have a year.
The Earth's axis is tilted, which means that the Northern HemisphereNorthern and Southern Hemispheres receive different amounts of sunlight at different times of the year. This causes the seasons.

The Earth's orbit around the sun is not a perfect circle, but slightly oval. The Earth is closest to the sun in early January and farthest away in July, but this has a much smaller effect on temperature than the tilt of the axis.

Earth orbits the sun at a speed of 18.5 miles per second, which is about 700,000 miles per hour. The average distance between Earth and the sun is 93 million miles, which is the equivalent of 149.6 million kilometers. It takes light about eight minutes to travel from the sun to Earth. Astronomers use the distance between Earth and the sun, known as one astronomical unit (AU), as a standard unit of measurement for distances in space.

## Formation

Earth was once an enormous cloud of dust and gas. Something caused the cloud to collapse, forming a spinning disc of gas and dust called a solar nebula. The faster the cloud spun, the more the dust and gas became concentrated at the center, forming the sun.

The remaining material in the solar nebula began to coalesce into various masses, including Earth. Earth was originally a hot, molten ball of magma. Over time, it cooled and oceans of liquid water formed. Heavy elements sank to the center of the planet, forming the core.

Scientists believe that Earth went through three stages of development: accretion, a giant impact, and a period of asteroid bombardment. During the accretion stage, Earth formed from the collisions of smaller objects. During the giant impact, a protoplanet known as Theia collided with **Earth**, forming the moon. During the asteroid bombardment, Earth was bombarded by asteroids.
Earth's early atmosphere was likely composed of hydrogen and helium. Volcanic eruptions released water vapor, ammonia, and carbon dioxide into the atmosphere. Eventually, the oceans formed and primitive life evolved.

Asteroids are believed to have played an important role in the formation of Earth. They may have carried water to the planet, which is essential for life.
Photosynthesizing bacteria evolved around 2.2 billion to 2.7 billion years ago. They released oxygen into the atmosphere, which changed its composition to what it is today. Our modern atmosphere is composed of 78 percent nitrogen and 21 percent oxygen, which enables it to support life.

## Sources

1. ↑ https://www.space.com/54-earth-history-composition-and-atmosphere.html
2. ↑ https://education.nationalgeographic.org/resource/formation-earth/