Planet Earth
Our Planet
our planet The striking image of our blue planet set against the darkness of space

A lone astronaut
a lone astronaut A shuttle astronaut on a space walk against the backdrop of planet Earth
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).
  • The planet is 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 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 100,000 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.
Surface, Atmosphere & Temperature
niagra falls Niagara Falls on the Canadian-American border

Surface
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.

Atmosphere
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.

Temperature
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).
Moons & Origin of Name
The Earth has one moon.
The name "Earth" is derived from the Anglo-Saxon word erda, meaning ground or soil.
Life on Earth
Life has existed on Earth for at least 3.5 of the 4.5 billion years of its history and is found 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 kilometers below it.

The Evolution of Earth
Early Earth Comet Bombardement
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 molten 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 (pictured left). 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.


Images & Video
Rainforest
rainforest
Planet Earth
A large city
a large city
Volcano
volcano
An African Tribe
african tribe
Ocean Life
ocean life


Planet Earth Statistics
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.