Earth seen from a satellite
|Longest distance from the Sun||152,097,701 km|
|Shortest distance from the Sun||147,098,074 km|
|Longest distance from the center of its orbital path|
|How long it takes to complete an orbit||365.256366 days|
|Average speed||29.783 km/s|
|Angle above the reference plane|
to the invariable plane
|Size and other qualities|
|Average radius||6,371.0 km (3,958.8 mi)|
|Surface area||510,072,000 km²|
|Volume||1.08321 × 10¹² km³|
|Mass||5.9736 × 1024 kg|
|Average density||5.515 g/cm³|
|Surface gravity||0.99732 g|
|Escape velocity||11.186 km/s|
|Avg. surface temp.||14°C|
Earth is the planet we live on. It is the third planet from the sun. It is the only planet known to have life on it. Lots of scientists think the earth formed around 4.5 billion years ago. It is one of four rocky planets on the inside of the Solar System. The other three are Mercury, Venus and Mars.
The large mass of the sun makes Earth move around it, just as the mass of Earth makes the moon move around it. Earth also turns around in space, so that different parts face the sun at different times. Earth goes around the sun once (one "year") for every 365¼ times it turns all the way around (one "day").
Earth is the only planet in our solar system that has a large amount of liquidwater. About 71% of the surface of Earth is covered by oceans. Because of this, people sometimes call it "blue planet".
Because of its water, Earth is home to millions of species of plants and animals. The things that live on Earth have changed its surface greatly. For example, early cyanobacteria changed the air and gave it oxygen. The living part of Earth's surface is called the "biosphere".
Orbit and turning[change | change source]
Earth is part of the eight planets and many thousands of small bodies that move around the Sun as its solar system. The Solar System is moving through the Orion Arm of the Milky Waygalaxy now, and will be for about the next 10,000 years.
Earth is generally 150,000,000 kilometers or 93,000,000 miles away from the sun (this distance is named an "Astronomical Unit"). Earth moves along its way at an average speed of about 30 km or 19 mi a second. Earth turns all the way around about 365¼ times in the time it takes for Earth to go all the way around the sun. To make up this extra bit of a day every year, an additional day is used every four years. This is named a "leap year".
The Moon goes around Earth at an average distance of 400,000 kilometers (250,000 mi). It is locked to Earth, so that it always has the same half facing Earth; the other half is called the "dark side of the moon". It takes about 27⅓ days for the Moon to go all the way around Earth, but because Earth is moving around the Sun at the same time, it takes about 29½ days for the Moon to go from dark to bright to dark again. This is where the word "month" came from, even though most months now have 30 or 31 days.
History of Earth[change | change source]
- See also: Historical geology, Age of the Earth, Giant impact hypothesis, and Great Oxygenation Event
Earth and the other planets formed about 4.6 billion years ago. They were made of the leftover gas from the nebula that made the Sun. The Moon may have been formed after a collision between the early Earth and a smaller planet (sometimes called Theia). Scientists believe that parts of both planets broke off — becoming (by gravity) the Moon.
Earth's water came from different places. Condensingwater vapour, and comets and asteroids hitting Earth, made the oceans. Within a billion years (that is at about 3.6 billion years ago) the first lifeevolved, in the Archaeanera. Some bacteria developed photosynthesis, which lets plants make food from the Sun's light and water. This released a lot of oxygen, which was first taken up by iron in solution. Eventually, free oxygen got into the atmosphere or air, making Earth's surface suitable for aerobic life (see Great Oxygenation Event). This oxygen also formed the ozonelayer which protects Earth's surface from bad ultravioletradiation from the Sun. Complex life on the surface of the land did not exist before the ozone layer.
Earth was very different in the distant past. Long ago, almost all land was in one place. This is called a supercontinent. The earliest known supercontinent was called Vaalbara. Much later, there was a time (the Cryogenian) when Earth was almost entirely covered by thick ice sheets (glaciers). This is called the Snowball Earththeory.
What it is made of[change | change source]
Earth is rocky. It is the largest of the rocky planets moving around the sun by mass and by size. It is much smaller than the gas giants such as Jupiter.
Chemical make-up[change | change source]
Overall, Earth is made of iron (32.1%), oxygen (30.1%), silicon (15.1%), magnesium (13.9%), sulfur (2.9%), nickel (1.8%), calcium (1.5%), and aluminium (1.4%). The 1.2% left over is made of many different kinds of other chemicals. Chemicals that are very uncommon (such as gold and platinum) can be very valuable.
The structure of Earth changes from the inside to the outside. The center of earth (Earth's core) is mostly iron (88.8%), nickel (5.8%), sulfur (4.5%), and less than 1% other things. The Earth's crust is largely oxygen (47%). Oxygen is normally a gas but it can join with other chemicals to make compounds like water and rocks. 99.22% of rocks have oxygen in them. The most common oxygen-having rocks are silica (made with silicon), alumina (made with aluminium), rust (made with iron), lime (made with calcium), magnesia (made with magnesium), potash (made with potassium), and sodium oxide, and there are others as well.
Shape[change | change source]
Earth's shape is a spheroid: not quite a sphere because it is slightly squashed on the top and bottom. The shape is called an oblate spheroid. As Earth spins around itself, the centrifugal force forces the equator out a little and pulls the poles in a little. The equator, around the middle of Earth's surface, is about 40,075 kilometers or 24,900 miles long.
The highest mountain above sea level—the well-known Mount Everest (which is 8.8 km or 5.5 mi above sea level)—is not actually the one that is the farthest away from the center of the Earth. Instead, the sleeping volcanoMount Chimborazo in Ecuador is; it is only 6.3 km or 3.9 mi above sea level but it is almost at the equator. Because of this, Mount Chimborazo is 6,384.4 km or 3,967.1 mi from the center of the Earth, while Mount Everest is 2.1 kilometers or 1.3 miles closer to it. Similarly, the lowest point below sea level that we are conscious of is the Challenger Deep in the Mariana Trench in the Pacific Ocean. It is about 10.9 km or 6.8 mi below sea level, but, again, there are probably places at the bottom of the Arctic Ocean that are nearer to the center of the Earth.
[change | change source]
The deepest hole ever dug is only about 12.3 kilometers or 7.6 miles. We know something about the inside of the Earth, though, because we can learn things from earthquakes and the times when volcanoeserupt. We are able to see how quickly the shock waves move through Earth in different places.
The inside of Earth is very different from the outside. Almost all of Earth's liquid water is in the seas or close to the surface. The surface also has a lot of oxygen, which comes from plants. Small and simple kinds of life can live far under the surface, but animals and plants only live on the surface or in the seas. The rocks on the surface of Earth (Earth's crust) are well known. They are thicker where there is land, between 30 to 50 km or 19 to 31 mi thick. Under the seas they are sometimes only 6 km or 3.7 mi thick. There are three groups of rocks that make up most of the Earth's crust. Some rock is made when the hot liquid rock comes from inside the earth (igneous rocks); another type of rock is made when sediment is laid down, usually under the sea (sedimentary rocks); and a third kind of rock is made when the other two are changed by very high temperature or pressure (metamorphic rocks). A very few rocks also fall out of the sky (meteorites).
Below the crust is warm and almost-liquid rock that is always moving around (the Earth's mantle). Then, there is a thin liquid layer of heated rock (the outer core). This is very hot: 7,000 °C or 13,000 °F. The middle of the inside of the Earth would be liquid as well but all the weight of the rock above it pushes it back into being solid. This solid middle part (the inner core) is almost all iron. This is what makes the Earth magnetic.
Pieces of the crust form plates[change | change source]
Main article: Plate tectonics
The Earth's crust is solid but made of parts which move very slowly. The thin level of hard rock on the outside of the Earth rests on hot liquid material below it in the deeper mantle. This liquid material moves because it gets heat from the hot center of the earth. The slow movement of the plates is what causes earthquakes, volcanoes and large groups of mountains on the Earth.
There are three ways plates can come together. Two plates can move towards each other ("convergent" plate edges). This can form islands (such as Japan), volcanoes, and high mountain ranges (such as the Andes and Himalayas). Two plates can move away from each other ("divergent" plate edges). This gives the warm liquid rock inside the earth a place to come out. This makes special mountain ranges below the sea or large low lands like Africa's Great Rift Valley. Plates are able to move beside each other as well ("transform" plate edges, such as the San Andreas Fault). This makes their edges crush against each other and makes many shocks as they move.
Surface[change | change source]
The outside of the Earth is not even. There are high places called mountains, and high flat places called plateaus. There are low places called valleys and canyons. For the most part, moving air and water from the sky and seasdamages rocks in high places and breaks them into small pieces. The air and water then move these pieces to lower places. Because of this, the Earth would have been very flat a long time before now. The fundamental cause of the differences in the Earth's surface is plate tectonics.
All places on Earth are made of, or are on top of, rocks. The outside of the Earth is usually not uncovered rock. Over 70% of the Earth is covered by seas full of salty water. This salty water makes up about 97½% of all Earth's water. The fresh water people can drink is mostly ice. Only a very small amount is in rivers and under the Earth for people to drink and use. The air above the Earth stops the water from going away into outer space. Also, much of the land on Earth is covered with plants, or with what is left from earlier living things. Places with very little rain are dry wastes called deserts. Deserts usually have few living things, but life is able to grow very quickly when these wastes have rainfall. Places with large amounts of rain may be large woods. Lately, people have changed the environment of the Earth a great deal.
Air[change | change source]
Main article: Atmosphere
All around the Earth is a large amount of air (the atmosphere). The mass of the Earth pulls the gasses in the air down and does not let them go into outer space. The air is mostly made of nitrogen (about 78%) and oxygen (about 21%) but there are a few other gasses as well. Most living things need the air (or parts of the air gripped in the water) to breathe and live. They use the gasses—especially oxygen and carbon dioxide—to make and use sugar and to give themselves power.
The air animals and plants use to live is only the first level of the air around the Earth (the troposphere). The day to day changes in this level of air are named weather; the changes between places far away from each other and from year to year are named the climate. Rain and storms are both in this level. Both come about because this part of the air gets colder as it goes up. Cold air becomes thicker and falls, and warm air becomes thinner and goes up. The turning Earth moves the air as well and air moves north and south because the middle of the Earth generally gets more power from the Sun and is warmer than the north and south points. At the same time, air over water (specially very warm water) gets water in it but, because cold air is not able to take in as much water, it starts to make clouds and rain as it gets colder. The way water moves around in a circle like this is called the water cycle.
Above this first level, there are four other levels. The air gets colder as it goes up in the first level; in the second level (the stratosphere), the air gets warmer as it goes up. This level has a special kind of oxygen called ozone. The ozone in this air keeps living things safe from damaging rays from the Sun. The power from these rays is what makes this level warmer and warmer. The middle level (the mesosphere) gets colder and colder with height; the fourth level (the thermosphere) gets warmer and warmer; and the last level (the exosphere) is almost outer space and has very little air at all. It reaches about half the way to the Moon. The three outer levels have a lot of electric power moving through them; this is called the ionosphere and is important for radio and other electric waves in the air. It is also where the Northern Lights are.
Even though air seems very light, the weight of all of the air above the outside of the Earth (air pressure) is important. Generally, from sea level to the top of the outer level of the air, a space of air one square centimeter across has a mass of about 1.03 kg and a space of air one square inch across has a weight of about 14.7 pounds. The mass of the air also keeps the Earth safe when rocks (meteorites) hit it from outer space. Without the air, the damage meteorites do would be much greater. Because of the air, meteorites generally burn up long before they get to the earth.
The air also keeps the Earth warm, specially the half turned away from the Sun. Some gasses – especially methane and carbon dioxide – work like a blanket to keep things warm.In the past, the Earth has been much warmer and much colder than it is now. Since people have grown used to the heat we have now, though, we do not want the Earth to be too much warmer or colder. Most of the ways people create electric power use burning kinds of carbon—especially coal, oil, and natural gas. Burning these creates new carbon dioxide and can cause more warming. A large discussion is going on now about what people should do about the Earth's latest warming, which has gone on for about 150 years. So far, this warming has been good for people: plants have grown better and the weather has been better than when it was colder before. Some people who learn about science, though, say that many bad things will possibly come about if the warming goes on.
People[change | change source]
Main article: Human
About seven billion people live on Earth. They live in about 200 different lands called countries. Some (like Russia) are large with many large cities. Others (like the Vatican) are small. The five countries with the most people are China, India, the United States, Indonesia, and Brazil. About 90% of people live in the north half of the world, which has most of the land. Scientists think that people originally came from Africa. Now, 70% of all people do not live in Africa but in Europe and Asia.
People change the Earth in many ways. They have been able to grow plants for food and clothes for about ten thousand years. When there was enough food, they were able to build towns and cities. Near these places, men and women were able to change rivers, bring water to farms, and stop floods (rising water) from coming over their land. People found useful animals and bred them so they were easier to keep.
Related pages[change | change source]
References[change | change source]
- ↑By International Astronomical Union convention, the term "Terra" is used for naming extensive land masses, rather than for the planet Earth. Cf.Blue, Jennifer (July 5, 2007). "Descriptor Terms (Feature Types)". Gazetteer of Planetary Nomenclature. USGS. Retrieved 2007-07-05.
- ↑ 2.02.12.22.32.4Williams, Dr. David R. "Earth Fact Sheet". NASA. Retrieved 2011-02-03.
- ↑Allen, Clabon Walter; Cox, Arthur N. (2000). Allen's Astrophysical Quantities. Springer. p. 294. ISBN 0387987460.
- ↑Various (2000). David R. Lide, ed. Handbook of Chemistry and Physics (81st ed.). CRC. ISBN 0-8493-0481-4.
- ↑"The age of the Earth in the twentieth century- a problem (mostly) solved". Geological Society, London, Special Publications. Retrieved 2009-07-28.
- ↑"Rover reveals Mars was once wet enough for life". Microsoft. Retrieved 28 July 2009.
- ↑Blue Planet is a poetic title for the Earth used in movies, in cheap paper books, in poetry, and in government reports (such as the European Space Agency's "Exploring the water cycle of the 'Blue Planet'")
- ↑"How many species are there on Earth". Harvard University. Retrieved 2009-07-28.
- ↑Purves, William Kirkwood; et al. (2001). Life, the science of biology. Macmillan. p. 455. ISBN 0716738732.
- ↑"Origins of life on Earth". Space.com. Retrieved 2009-07-28.
- ↑"Earth's location in the Milky Way". NASA. Retrieved 2009-08-06.
- ↑"NASA- an Earth fact sheet". NASA. Retrieved 2009-08-06.
- ↑Staff (2007-08-07). "Useful Constants". International Earth Rotation and Reference Systems Service. Retrieved 2008-09-23.
- ↑Cite error: Invalid tag; no text was provided for refs named .
- ↑Dalrymple, G. Brent (2001). "The age of the Earth in the twentieth century: a problem (mostly) solved". Special Publications, Geological Society of London190 (1): 205–221. doi:10.1144/GSL.SP.2001.190.01.14.
- ↑"Origin of the Moon in a giant impact near the end of the Earth's formation". Nature.com. Retrieved 2009-07-28.
- ↑"Earth life appeared on land 1.5 billion years earlier than previously thought". SpaceRef.com. Retrieved 2009-07-03.
|Saving Planet Earth|
|Presented by||See episodes for detail|
|Country of origin||United Kingdom|
|No. of episodes||11|
|Executive producer(s)||Sara Ford|
|Running time||30 minutes|
|Production company(s)||BBC Natural History Unit|
|Original network||BBC One|
|Picture format||576i (16:9)|
|Original release||24 June (2007-06-24) – 6 July 2007 (2007-07-06)|
Saving Planet Earth is a season of nature documentaries with a conservation theme, screened on BBC Television in 2007 to mark the 50th anniversary of its specialist factual department, the BBC Natural History Unit.
The series featured films contributed by a number of celebrities on the plight of various endangered species, and coincided with the launch of the BBC Wildlife Fund, a charitable organisation which distributes money to conservation projects around the world. The television series culminated in a live fundraising telethon on BBC Two, hosted by Alan Titchmarsh, which raised over £1 million for the charity.
The BBC broadcast a second live telethon in 2010. Wild Night In was presented by Kate Humble, Chris Packham and Martin Hughes-Games and featured conservation projects which had benefited from the support of the BBC Wildlife Fund. This helped to raise a further £1 million.
The format of Saving Planet Earth was something of a departure for the Unit, using celebrities not normally associated with natural history programmes rather than selecting a familiar face from its pool of specialists.
The season began with a special hour-long programme on BBC One entitled "Sharing Planet Earth", a clarion call for action to conserve nature, presented by David Attenborough. It was followed by nine documentaries broadcast nightly over the course of a fortnight, in which celebrities investigated the plight of endangered species. Each programme was introduced by Alan Titchmarsh and featured a short narration by Attenborough to provide some background information on the featured species.
Along with the BBC One programmes, a five-part series entitled Saving Planet Earth - UK was broadcast in parallel on BBC Two. Presented by Michaela Strachan, it aimed to show audiences the threats facing British wildlife, and how they could help by becoming directly involved in conservation.
A second five-part series on the CBBC Channel followed seven young competition winners on their own personal journeys to destinations including Brazil and Borneo to report on threatened species.
The season culminated with a live fundraising evening to raise money for a newly established conservation charity, the BBC Wildlife Fund.
1. Saving Planet Earth "All the animals we’ll see over the course of the series are disappearing because of one species: humans. We know that we are using more than our fair share of the planet and its resources and we must now redress this imbalance. Any effort to do so – no matter how big or small – is valuable, if we wish to ensure a future that is healthy for all life on planet Earth so we have to save earth from various types of Pollution, Waste food, Drained Water etc. The earth is our mother planet in which we born and understand learn to speak, learn to walk and learned everything that we are now able to do. "It is only planet in our solar system on which life exists which incredible biodiversity. People all over the world celebrate this grand event all to protect flora and fauna and clean up the earth on which we live. Our life will be waste if we have no any goal. Without any goal we will feel unlucky, waste life etc. But if we don't Save Planet Earth then, our Earth will be destroyed and we can't live. So, Save Planet Earth.
2. Saving Gorillas
In the first of nine 30-minute films focussing on particular threatened species, pop star Will Young travels to Cameroon to report on the plight of the lowland gorilla. Although more numerous than its mountain-dwelling cousins, its numbers are declining fast due to habitat loss and poaching.
3. Saving Tigers
Tigers have been a protected species for many years, but despite this they are increasingly threatened by extinction due to poaching and increasing conflict with humans. But can the spiritual and deeply felt respect for tigers held by ordinary Indians offer a lifeline for the species? Newsreader Fiona Bruce reports from Bandhavgarh National Park, where acclaimed wildlife cameraman and tiger expert Alphonse Roy has been watching and filming them for 20 years.
4. Saving Crocodiles
DJ Edith Bowman travels 6,000 miles to Cambodia on the trail of the very rare Siamese crocodile, which was hunted to brink of extinction. Now, conservation charities such as The Wildlife Conservation Society and Fauna and Flora International are working in partnership with the Cambodian government and have established a crocodile farm to increase the population size.
5. Saving Albatross
Carol Thatcher flies to the Falkland Islands to find out why the black-browed albatross and its relatives are under threat. Albatross numbers have plummeted in recent years due to long-line fishing practices.
6. Saving Rhinos
Former England cricketer Phil Tufnell reports from Assam in India, one of the last remaining homes of the Indian rhinoceros. Fewer than 2,000 are left in the wild due to poaching for their horns.
7. Saving Wolves
In the southern part of the Ethiopian Highlands, a remote mountain region and the last home of the Ethiopian wolf, Graham Norton discovers that encroachments by the ever-expanding human population is threatening the wolf's survival.
8. Saving Elephants
Adrenaline junkie Jack Osbourne journeys to northern Namibia to investigate the plight of the desert elephant. Although saved from extinction by the banning of the ivory trade, the desert elephants now face a new threat. Local people once roamed the land as migrants, but their recent conversion to farming has brought them into conflict with elephants over precious resources.
9. Saving Turtles
Of the seven remaining species of sea turtle, six are seriously threatened with extinction. Saira Khan travels to Sri Lanka, one of the best places in the world to see turtles, but even here commercial fishing practices and pressure on the turtles' nesting beaches are driving numbers down.
10. Saving Orangutans
TV presenter Nick Knowles reports from Borneo, where orangutan numbers are being decimated due to the deforestation of the island and the growth of palm plantations. He visits a sanctuary where more than 600 orphaned young apes are cared for. Their mothers are usually killed by plantation workers, because the orangutans are attracted to the palms for food and can damage the crops. Their young are taken for the pet trade or are simply left to die, but those lucky enough to be rescued are brought to the sanctuary. Now, it simply can't cope with the number of apes being brought in and desperately needs extra funds. This programme was incorporated into the live fundraising broadcast (see below).
11. Saving Planet Earth - Live
The series culminated in a live fundraising event broadcast from Kew Gardens, hosted by Titchmarsh and featuring interviews with many of the BBC’s natural history presenters, including Attenborough, Strachan, Bill Oddie, Kate Humble, Simon King, Steve Leonard, Jonathan Scott, Chris Packham and Charlotte Uhlenbroek. A registered charity, the BBC Wildlife Fund, was established to direct funds raised by the programmes to conservation charities in the field to help save the featured animals, and other species, from extinction. Saving Planet Earth enabled the Fund to raise £1 million on the night, a total which had almost doubled by the end of 2010.