User:JacyLu/TWA/Earth/2



 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%的地球表面被覆蓋鹽水海洋. 地球是目前已知存在液態水的太陽系中唯一存在的地方. 另外29%由大陸和島嶼形狀的岩石土地組成.

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.

形狀和結構的地球表面被水覆蓋. 水下表面具有許多與火山，山脈和海溝或峽谷相同的特徵. 沒有被水覆蓋的30%主要是森林，沙漠平原，山脈和高原. 人類文明導致了城市化的加劇——城市的發展. 許多事情可以改變地球表面. 板塊構造是變化的主要原因，但還有其他原因，如風雨的侵蝕，海洋的侵蝕或隕石撞擊. 構成地球表面的岩石主要有三種類型： 火成岩是在地幔的岩漿或熔岩到達地表並冷卻時形成的. 當天氣變冷時，它會變成岩石或凝固. 沉積岩是由沉積物製成的，如沙子或其他岩石的小塊，這些沉積物被壓碎並緊密地堆積在一起. 變質岩，當其他兩種類型中的任何一種因高溫或低溫和壓力而改變時形成的.

Atmosphere

A planet's atmosphere is a layer of different gases surrounding it. It is kept there by gravity. The Earth's atmosphere is made of about 78% nitrogen, 21% oxygen and small amounts of other gases. This mixture is often called air. Further up there is a layer of ozone gas called the Ozone layer. Ozone absorbs ultraviolet radiation from the Sun. Ultraviolet radiation is dangerous to people, so without the Ozone layer life would not be possible. The atmosphere also protects the earth from crashes with meteors and small asteroids. This is because they burn up due to all the friction as they fly through it. It also helps to keep Earth warm. Some gases including carbon dioxide and methane act like a blanket around the Earth, they trap heat under them, keeping the Earth warm.

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. When it gets cold enough it turns back into water again. This causes the clouds and rain. It is called the water cycle.

Orbit and rotation

The Earth takes about 24 hours to complete one day and about 365 days to complete a year. 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. This is a leap year. 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. The Moon orbits the Earth at an average distance of 250,000 miles. It is tidally locked to Earth, which means it always has the same side facing the Earth. It takes roughly one month to complete one orbit. The Earth is part of the Solar System and orbits the sun along with thousands of small objects and eight planets. 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.

References