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Earth
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Earth

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Surface

Our home planet is a rocky, terrestrial planet. It has a solid and active surface with features that include mountains, valleys, volcanoes, plains and oceans.

The planet’s crust and upper mantle are divided into plates that are constantly moving. Earth’s oceans contain 97% of the planet’s water.

71%

of the Earth’s surface is covered in water

Moon

Earth is the only planet that has a single moon. Even though our moon is the brightest object in the night sky, it is relatively far away. In fact, 30 Earth-sized planets could fit in between Earth and the moon.

Structure

Earth is composed of four main layers: inner core, outer core, mantle and crust.

Inner core

Diameter: 1,518 miles

Temperature: About 9,000°F to 12,000°F

State: Solid

Outer core

Thickness: 1,400 miles

Temperature: 6,700°F to 10,000°F

State: Liquid

Mantle

Thickness: 1,800 miles

Temperature: 2,500°F to 5,500°F

State: Molten rock

Crust

Average thickness: 19 miles for continental crust, 3 miles for oceanic crust

Temperature at the bottom of the crust: 1,800°F

State: Solid

Orbit and rotation

Earth completes one rotation on its axis every 23.9 hours. It takes Earth 365.25 days to orbit the sun. The extra quarter of a day leads to one leap day added to our yearly calendar every four years in order to keep it consistent with Earth’s orbit.

Similar to other planets, Earth’s orbit is not a perfect circle, but an ellipse. Our planet is a closer to the sun in early January and farther away in July. Earth itself is also not perfectly round because its spin causes it to be squashed at its poles and swollen at the equator.

Earth’s axis is tilted 23.4 degrees, causing our yearly cycle of seasons. When the northern hemisphere is tilted toward the sun, summer occurs. At this time, the southern hemisphere is experiencing winter, as it is tilted away from the sun. Six months later, the situation is reversed. In the spring and fall, the sun shines evenly on both hemispheres.

Atmosphere

Earth’s atmosphere is made up of mostly nitrogen and oxygen. It affects climate and weather and shields the planet from the sun’s radiation. Gases in the atmosphere trap heat from the sun and warm the Earth.

The atmosphere also protects us from incoming meteoroids, most of which break up before they can reach the surface.

The atmosphere is divided into layers. From the surface up they are the troposphere, stratosphere, mesosphere, thermosphere and exosphere.

Earth’s extremes

Highest elevation

29,035 feet

Mount Everest, located along the Nepal-China border, is the highest mountain above sea level.

Deepest point

36,200 feet

Challenger Deep in the Mariana Trench is located almost 7 miles below sea level in the western Pacific Ocean.

Highest Temperature

134°F According to the World Meteorological Organization, the highest temperature ever recorded was in Death Valley, Calif., in 1913.

Lowest Temperature

-128°F According to the World Meteorological Organization, the lowest temperature ever recorded was in Vostok, Antarctica, in 1983.

Satellites

As of March 31, 2020, there were a total of 2,666 active artificial satellites orbiting the Earth.

Biodiversity

Human population

7.8 billion

Named species

1.9 million

This number includes plants, animals, bacteria and fungi, though most of the identified species so far are insects. Estimates of the total number of species in the world range from 8.7 million to possibly 1 trillion (a number which would include microbes.)

New species identified each year

18,000

Break down

Approximate number of species that have been identified for different categories of living organisms:

Mammals

5,500

Birds

10,400

Reptiles

10,000

Amphibians

7,300

Fish

32,900

Insects

1,000,000

Spiders

102,200

Plants

307,600

Distance from the sun

93

million miles

Sunlight

As the third closest planet to the sun, it takes light from the sun about 8.3 minutes to reach Earth.

Year length

365.25 days

Day length

23.9 hours

Namesake

Apart from Earth, all of the planets were named after Greek and Roman gods and goddesses. Earth is a German word that means “the ground.”

Planet type

Terrestrial

Diameter

7,918 miles

Earth is the biggest of the terrestrial planets.

If the sun were as tall as a typical front door, the Earth would be about the size of a nickel.

Environment

Earth has a hospitable temperature, mix of chemicals, and liquid water that have made life possible here.

Average temperature: 57°F

Moons

1

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