Planet Earth Facts

• Earth is the third planet from the sun, orbiting at a distance of 93 million miles (150 million km).
• It is the fifth biggest planet in the solar system with a diameter of 8,000 miles (13,000 km).
• Earth is around 4.5 billion years old.
• The Earth spins on its own axis every 23 hours 56 minutes and takes 365 days 6 hours to orbit the sun.
• The inner core of the Earth creates a magnetic field around the planet which protects it from solar winds, the liquid metal core is believed to be hotter than the surface of the sun.
• Life first appeared on the planet 3.5 billion years ago in the form of single celled organisms.
• Modern humans have only existed on the planet for around 200,000 years.
• The Earth is less well mapped than the Moon, Venus or Mars because the majority of its surface is covered by water.
• The first picture of Earth taken from space occurred in October 1946.
• There are more than 3,000 spacecraft currently orbiting the Earth.

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70% of Earth's surface is covered by water. The rest is made up of land covered by forests, deserts, mountain ranges, grassy plains and two polar ice caps. There are also a small amount of active volcanoes. Nitrogen makes up 78 percent of the atmosphere, while oxygen makes up 21 percent. The remaining 1 percent consists of argon and small amounts of other gases. The average temperature on Earth is 13C (55F) to 17C (63F). The coldest temperatures can be found at the poles, around -34C (-30F), the hottest at the equator, around 32C (90F).

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Life has existed on Earth for at least 3.5 of its 4.5 billion year history and is found almost everywhere on the planet. From the air to the oceans, from mountain tops to ocean basins, from polar glaciers to desert sands, from the surface to many miles below. The variety of life on Earth is extraordinary, there are millions of different types of animal and plant life, each perfectly adapted to their natural environment through the process of evolution. The key to life on Earth is water, it is thought that without it life is unable to exist, seven tenths of our planet's surface is covered in oceans, seas, lakes and rivers making Earth a veritable oasis in our little corner of the Milky Way galaxy. The Earth has one moon.
The name "Earth" is derived from the Anglo-Saxon word erda, meaning ground or soil.

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Some ancient civilizations believed that the interior of Earth was home to another world, a land where the gods resided or perhaps unearthly creatures held domain. The belief of a world inside a world was held by some parts of the scientific community up until two hundred years ago, laying the path for fictitious work such as Jules Verne’s “Journey to the Center of the Earth”. In some religions the center of the earth is home to a hellish world of brimstone and fire where people would be condemned to live for eternity. In truth Earth’s interior is far less 'out of this world' but its just as mysterious and fascinating. So what exactly lies under our feet and what is it made of? What we find is that our planet is actually rather like an onion with several layers making up its structure. Let’s go through them one by one. Crust
This is the rocky outer layer of the Earth, what we walk on every day and what makes up the ocean floor. The crust isn’t one solid object, it is broken up into plates which move and collide with each other, causing mountain ranges to form or earthquakes to occur. The land mass of the Earth is constantly shifting but at a very slow pace, creating new continents over millions of years. Mantle
Around 5 miles (8 kilometers) below the ocean floor we find the next layer, called the mantle. This is also made of solid rock, rock so hot that it would flow on Earth’s surface but deep underground pressure doesn’t allow it to melt, instead it moves extremely slowly in currents. Occasionally it will find its way to the surface and explode violently from volcanoes as magma. The mantle is the thickest layer of Earth’s structure, extending for around 1,850 miles (3,000 km). Outer Core
Below the mantle we find the outer core, the only layer of the Earth that can be described as liquid, here the composition changes form rock to metal, in the case of the outer layer in the form of extremely hot liquid iron. It is thought that Earth’s magnetic field is created by the outer core which protects us from radiation emanating from the sun. The outer core descends a further 1,400 miles (2,250 km). Inner Core
Here we find the last layer of our onion like planet and the very center of Earth, the inner core is mostly solid iron and nickel with temperatures similar to that found on the surface of the sun. The inner core has a diameter of around 800 miles (1,290 km).

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Around 4.6 billion years ago matter orbiting around the center of the solar system began clumping together to form the beginnings of our planet. Eventually a substantial mass took shape allowing its gravity to sweep up more and more elements adding to its size. The heavier elements sank to the center of the Earth creating its iron core while the lighter elements drifted to the top creating the Earth’s crust.

Between 4 and 3.5 billion years ago the Earth was subject to bombardments from comets which brought volatile molecules such as nitrogen, ammonia and methane. The gaseous output from these elements formed the early atmosphere of our planet. These comets also brought another important volatile element, water. Rain began to fall from the sky and as the planet began to cool down oceans formed.

Around 3.8 billion years ago the building blocks of life, amino acids, began appearing in the oceans, possibly due to chemical reactions produced by lightning or sunlight. Three and a half billion years ago the first single cell organisms began to form in the oceans, due to the lack of any oxygen they used methane or hydrogen in their metabolism.

Two and a half billion years ago algae began to form on the surface of the oceans and on land based rocks. These algae were crucial in the evolution of life on Earth as they produce huge amounts of oxygen as a bi-product. Over a period of 2 billion years they oxygenized the oceans and the atmosphere allowing for the evolution of animals to begin around 600 million years ago.

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Diameter: 7,926 miles (12,756 km)
Average Distance from Sun: 93 million miles (150 million km)
Orbital Period: 365.24 days
Rotation Period: 23.934 hours
Moons: 1

Maximum Surface Temperatures: 58C (136F)
Minimum Surface Temperatures: -88C (-126F)

Gravity: 9.766 m/s²
Density: 5.515 g/cm³
Mass: 5.9737 x 10²⁴ kg
Volume: 1.0832 x 10¹² km³
Atmosphere: 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.038% carbon dioxide.

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