The Earth is the third planet from the Sun. It is one of the four terrestrial planets in our Solar System. This means most of its mass is solid. The other three are Mercury, Venus, and Mars. The Earth is also called the Blue Planet, "Planet Earth", and "Terra".
The Earth is home to millions of species of plants and animals, including humans. Earth is the only planet in the galaxy known to support life. Earth has many places that are suitable for humans to live in, although some areas of the planet can are dangerous or uninhabitable.
Science shows that Earth formed around 4.5 billion years ago. The organisms that live on Earth have completely changed its air (atmosphere); this is called a biosphere.
71% of Earth's surface is covered in salt water oceans. Earth is the only place in the Solar System where liquid water is known to exist at present. The other 29% is made of rocky land in the shape of continents and islands.
Earth interacts with other objects in the Solar System, particularly the Sun and the Moon. The Earth orbits the Sun roughly once every 365.25 days. One spin is called a 'day' and one orbit around the Sun is called a 'year'. This is why there are 365 days in a year, but a leap day added to the calendar once every 4 years.[1]
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Shape and structure
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Tectonic plates
The Earth is the only terressdgsgaffsform.[4]
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Weather, climate, and water cycle
Hot air rises. As it rises it gets colder again and falls. This creates convection currents. When hot air meets cold air different weather effects happen. Convection currents are the cause of almost all weather on Earth. When it gets hot on the surface water evaporates and becomes steam or water vapour. This hot water vapour rises. As it rises it gets colder.[original research?] When it gets cold enough it turns back into water again. This causes the clouds and rain. It is called the water cycle.[7]
Orbit and rotation
The Earth takes about 24 hours to complete one day and about 365 days to complete a year.[citation needed] Actually, the Earth take 365.24 days to revolve around the sun. After every four years, an extra day is added, and the year has 366 days.[citation needed] This is a leap year.[citation needed] The Earth is, on average, 150 million kilometers away from the Sun, and moving at a speed of 30 kilometers a second or 108,000 miles an hour.[citation needed] The Moon orbits the Earth at an average distance of 250,000 miles.[citation needed] It is tidally locked to Earth, which means it always has the same side facing the Earth.[citation needed] It takes roughly one month to complete one orbit.[citation needed] The Earth is part of the Solar System and orbits the sun along with thousands of small objects and eight planets.[citation needed] The Sun, and therefore the Solar System, are currently traveling through the Orion Arm of the Milky Way Galaxy and will be for approximately the next 10,000 years.[8]
References
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- ^ Gnawledge, O'penn. "Planet Earth in the Balance of History". Science and Nature Journal. SandNjournal.com/Earthinthebalance. March 21, 20. Retrieved April 24th, 2013.
- ^ "Origin of the Moon and Earth". Reisch, Maggy. Nature.com: Volume 10:2, p.19-27. http.www.nature.com/102/Reisch/Earth. Retrieved 2009-07-28.
- ^ "Tectonic plates. Shifting Sands". Roberts, Paul. Harvard University Press. http.www.harvard.edu/roberts/shifting. Retrieved 2009-07-28.
- ^ Tossfsdagasfrieved 2009-08-02.
- ^ "The Crust". Alphonz, Edgar. Oregon private University. http.www.osu.edu/Alphonz/Crust. Retrieved 2009-07-03.
- ^ "NSA - Earth's atmosphere". NSA Student Guides. http.www.nsa.gov/student/atmosphere. Retrieved 2009-08-06.
- ^ "What causes weather?". NASA Student Guides. http.www.nasa.gov/student/weather. Retrieved 2009-08-06
- ^ "Earth's in the Milky Way". NASA Student Guides. http.www.nasa.gov/student/milkyway. Retrieved 2009-08-06.