Earth

Our home planet is the fifth largest in our solar system and the third furthest from the Sun. Earth is unique because it's the only planet with liquid water on its surface. Out of the four closest planets to the Sun, Earth if is the biggest and slightly larger than Venus.

The name 'Earth' originates to about 1,000 years ago. Every planet, except for Earth, were named after Greek and/or Roman gods/goddesses. Earth is an exception to this, because the name originates from a Germanic word, which simply translates to 'the ground'.

## Size and Distance

Out of all the terrestrial planets in our solar system, Earth has the biggest radius with a length of 3,959 miles (6,371 kilometres). The Earth is also the fifth largest planet in our solar system.

Earth is exactly one astronomical unit away from the Sun. One astronomical unit (abbreviated as 'AU') is the equal distance from the Sun to Earth. This measuring system is a quick way to calculate how long it would take to travel to each planet.

Sunlight takes about 8 minutes to reach the Earth.

## Orbit and Rotation

To take one trip around the Sun, Earth takes 365.25 days to make a full orbit. For the Earth to make one rotation, it takes 23.9 hours. The fact that our planet needs an extra quarter of a day to complete an orbit around the Sun means that our calendar will be faced with challenges. We know that one year takes 365 days, but every fours years, we add an extra day on to our calendar to keep the Earth's orbit consistent.

Earth tilts at an axis of 23.4 degrees, this tilt causes our seasonal cycle. During part of the year, the northern hemisphere is tilted towards the Sun, which means that the southern hemisphere is tilted away from the Sun. This indicates that whichever hemisphere is tilted towards the Sun, that hemisphere will receive its Summer first. Six months later, this all switches because when a hemisphere is tilted away from the Sun causing Winter.

## Structure

Earth is made up of four main layers. The inner core at the centre, surrounded by the outer core, mantle and crust.

The inner core, made up of iron, has a radius of 759 miles (1,221 kilometres). The inner core's temperatures can reach as high as 5,400 degrees Celsius. Next we have the outer core, which is about 1,400 miles (2,300 kilometres) thick.

Now we reach the mantle, the thickest layer in the Earth. Made up of viscous mixtures of molten rock, the mantle reaches 19 miles (30 kilometres) deep on average terrain. The crust reaches 3 miles (5 kilometres) in length when you reach the bottom of the ocean.

## Formation

About 4.5 billion years ago, when the solar system formed, Earth formed by gas and dust pulling in together by gravity. Like other terrestrial planes, Earth has an inner core, a mantle and crust.

### Kid-Friendly Facts

Our home planet is a rocky planet. It has a very active ground with volcanoes, mountains and canyons. Earth is special because it is the only planet in our solar system filled with water. About 70% of our planet's surface is made up of water.

## Surface

Earth has volcanoes, mountains and valleys, just like Mars and Venus. Earth has a lithosphere (this includes both the crust and the mantle) which is divided huge plates which are constantly moving. If we take the North American plate, which moves to the west over the pacific ocean, means that earthquakes will occur more often towards the west because the plates from the west and the east will grind up against each other.

Nearly 70% of the Earth's surface is covered up by global oceans, which reaches a depth of 2.5 miles (4 kilometres) and contains 97% of the ocean. As a matter of fact, most of Earth's volcanoes are hidden underwater.

## Atmosphere

Our surface atmosphere consists of 78% of Nitrogen, 21% of oxygen, and 1% of other gases including argon, carbon dioxide and neon. As our atmosphere affects our climate, both long-term and short-term, local weather protects us from deadly gases. Our atmosphere is also lucky enough to protect us from asteroids, most of which burn up as soon as they enter. They then strike the surface with the object now being known as a meteorite.

## Magnetosphere

Our planet has a rapid rotation, and the molten nickel-iron core gives life to the Earth's magnetic field. A solar wind distorts this magnetic field resulting in a tear-dropped shape in space. (A solar wind is when a string of particles are continuously ejected from the Sun.) When these solar wind particles enter the Earth's atmosphere, they will collide with air molecules above the magnetic pole.

This is what causes compasses to always point towards the north direction regardless of which way you're facing. The magnetic pole can be changed, however, by flipping the Earth's magnetic field. Geographical records tell us that magnetic flips happen once every 400,000 years. However, this timing can be very irregular. Since magnetic flips have already occurred, we know that it doesn't effect any life at all (which is good news) and the next reversal is not likely until for at least 100,000 years. When this does happen, compasses could point in all different directions, after the switch is complete, all compasses will point south instead of north.

## Moons

Earth is the only planet in our solar system to have one moon. It is the brightest and yet familiar object in the sky. The moon is lucky to be part of our orbit because it protects us from wobbles, which has caused the climate to be less variable over thousands of years.

Earth can sometimes host orbiting asteroids, this is because that they become trapped in the magnetic field. Some asteroids will orbit longer than others.

Most moons are made up of rocks that were captured by the planet's gravity, but our moon was formed by several large rocks colliding together. When the Earth started to begin its life-cycle, a chunk of rock smashed into it causing a removing a portion in the Earth's core. With the moon having a radius of 1,080 miles (1,738 kilometres), it is the fifth largest moon in our solar system (after Ganymede, Titan, Callisto and Io).

Most people think that the moon is relatively close the Earth, but that is not the case. The moon is approximately 238,855 miles (384,400 kilometres) away from Earth. If we were to measure that distances in the size of our planet, it would take 30 Earths to reach the moon.

## Human Life

Earth has a very mixed temperature, meaning that in the summer we could reach scorching temperatures, and/or in the winter, we could reach freezing temperatures. Since our current temperatures allow for water to live for long periods of time, we can potentially have an infinite water source. Of course, this has allowed life to live on this planet for 3.8 billion years.

Some strange features on Earth make life living on this planet fairly easy. due to the on-going effects of our climate.