Earth
From Farscape Encyclopedia Project
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Mostly Harmless
Home of Chocolate
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Earth is the third planet from the sun and is the home planet of the human race.
Earth, the largest and densest rocky planet, was formed about 4.5 billion years ago. The Earth's interior is divided into four layers, which is typical of rocky planets. Each layer has different characteristics and is made of different elements and minerals.
There are many different types of features on Earth’s surface due to the complexity of our planet. The surface is unique from the other planets because it is the only one which has liquid water in such large quantities. Water forms some features of Earth's surface such as rivers, oceans, beaches and lakes. Other surface features, such as mountains, earthquakes and volcanoes, are formed when large pieces of the Earth’s outer layer move slowly by plate tectonics.
The atmosphere surrounds Earth and protects us by blocking out dangerous rays from the sun. The atmosphere is a mixture of gases that becomes thinner until it gradually reaches space. It is composed of Nitrogen (78%), Oxygen (21%), and other gases (1%).
Oxygen is essential to life because it allows us to breathe. Some of the oxygen has changed over time to ozone. The the ozone layer filters out the sun's harmful rays. Recently, there have been many studies on how humans have caused a hole in the ozone layer.
Humans are also affecting Earth's atmosphere through the greenhouse effect. Due to increases in gases, like carbon dioxide, that trap heat being radiated from the Earth, scientists believe that the atmosphere is having trouble staying in balance creating the greenhouse effect .
The atmosphere is divided into five layers depending on how temperature changes with height. Most of the weather and clouds are found in the first layer.
The Earth has a magnetic field with north and south poles. The Earth's magnetic field reaches 36,000 miles into space.
The magnetic field of the Earth is surrounded in a region called the magnetosphere. The magnetosphere prevents most of the particles from the sun, carried in solar wind, from hitting the Earth.
Some particles from the solar wind can enters the magnetosphere. The particles that enter from the magnetotail travel toward the Earth and create the auroral oval light shows.
The Sun and other planets have magnetospheres, but the Earth has the strongest one of all the rocky planets. The Earth's north and south magnetic poles reverse at irregular intervals of hundreds of thousands of years.
The Earth's one natural satellite, the Moon, is more than one quarter the size of Earth itself (3,474 km diameter). Because of its smaller size, the Moon's gravity is one-sixth of the Earth's gravity, as we saw demonstrated by the giant leaps of the Apollo astronauts.
While there are only two basic types of regions on the Moon's surface, there are many interesting surface features such as craters, mountain ranges, rilles, and lava plains. The structure of the Moon's interior is more difficult to study. The Moon's top layer is a rocky solid, perhaps 800 km thick. Beneath this layer is a partially molten zone. Although it is not known for certain, many lunar geologists believe the Moon may have a small iron core, even though the Moon has no magnetic field. By studying the Moon's surface and interior, geologists can learn about the Moon's geological history and its formation.
The footprints left by Apollo astronauts will last for centuries because there is no wind on the Moon. The Moon does not possess any atmosphere, so there is no weather as we are used to on Earth. Because there is no atmosphere to trap heat, the temperatures on the Moon are extreme, ranging from 100° C at noon to -173° C at night.
The Moon doesn't produce its own light, but looks bright because it reflects light from the Sun. Think of the Sun as a light bulb, and the Moon as a mirror, reflecting light from the light bulb. The lunar phase changes as the Moon orbits the Earth and different portions of its surface are illuminated by the Sun.
About 70% of the Earth is covered with water, and 97% of that is part of the salty oceans. Only a small portion of the Earth's water is freshwater. This includes such things as rivers, lakes, and groundwater. Freshwater is needed for drinking, farming, and washing. There is even water in the form of ice at the poles. Without water, life as we know it would not exist.
Few rivers flow into the Pacific Ocean since it is bordered by mountains. However, many large rivers flow into the Atlantic Ocean, carrying sediment from the land. This process is one step of the water cycle.
One way to explore water is by scuba diving. Another way is to use a deep-sea submersible like the Alvin.
