Earth

Earth is the planet we live on. It is the only planet in the solar system with liquid water. It's also the only one known to have life

How big is the Earth?

The Earth is 12,742 km in diameter. It's the largest terrestrial planet in the solar system. The Earth weighs 5,973,000,000,000,000,000,000,000 kg. (That's nearly 6 trillion trillion kilograms)

How old is the Earth?

Scientific evidence shows that the Earth is 4.6 billion years old.

What is its surface like?

Earth's surface is made of continents and oceans. There are also islands in the oceans. The top layer of Earth is called the crust. It divided into pieces called tectonic plates. They move very slowly, carrying continents with them. The places where they meet are called fault lines. On fault lines, magma can seep up through the cracks and create volcanoes (once on the surface it's called lava.) When fault lines move apart they create new land (these are called constructive margins) and where they move towards each other one of them goes underneath the other (these are called destructive margins.) When they slide past each other, great tension builds up due to friction - when this tension is released the plates move rapidly and sharply in one direction, creating earthquakes.

Earth

Earth is the planet we live on. It is the only planet in the solar system with liquid water. It's also the only one known to have life

How big is the Earth?

The Earth is 12,742 km in diameter. It's the largest terrestrial planet in the solar system. The Earth weighs 5,973,000,000,000,000,000,000,000 kg. (That's nearly 6 trillion trillion kilograms)

How old is the Earth?

Scientific evidence shows that the Earth is 4.6 billion years old.

What is its surface like?

Earth's surface is made of continents and oceans. There are also islands in the oceans. The top layer of Earth is called the crust. It divided into pieces called tectonic plates. They move very slowly, carrying continents with them. The places where they meet are called fault lines. On fault lines, magma can seep up through the cracks and create volcanoes (once on the surface it's called lava.) When fault lines move apart they create new land (these are called constructive margins) and where they move towards each other one of them goes underneath the other (these are called destructive margins.) When they slide past each other, great tension builds up due to friction - when this tension is released the plates move rapidly and sharply in one direction, creating earthquakes.

Earth has many kinds of environments. It is cold and icy in places like Antarctica. There are hot, dry deserts in some parts of the world like Africa and Arabia, and cold, dry deserts in some others like Siberia. Rain forests grow where it is warm and wet, in equatorial zones (these are areas a few hundred miles around a very hot 'line' called the equator. Outside equatorial zones there are areas of very dry, mostly hot desert, which is where all the water making the rainforests wet comes from, causing these areas to be very dry. Other kinds of forests grow between the Equator and the Poles, like the massive coniferous forests of pine and other trees which keep their leaves all the time, and deciduous forests of oak, beech and other leaf-losing plants. Some places are very wet and are called swamps or marshes. There are grasslands, many hot, some called savannahs, with lots of grass and few trees. There are also mountains, caused by collision of tectonic plates. Some of them are high with snow and ice on their tops all year. Others are lower and more rounded.

Is there life on the Earth?

When this question is asked on other planets in the solar system, it is important to know where you might find living things here on the Earth. Almost every important feature of the surface of the earth is in some way affected by living things, including mineral deposits and even the content of the air that we breathe.

One of the critical ingredients that all living things seem to need is water. Wherever you find liquid water, you will almost always find living things, even if it is not a place where you would want to live as a person. Bacteria has been found inside gysers, where the water temperature can be over 300° C. These living things not only live there, but even seem to need those very high temperatures. Other living things have been found on the bottom of the ocean, living around "thermal vents" where the only energy they obtain is from lava heating up water. It is so deep in the ocean that no sunlight ever appears there. Finally, you can find living things in Antarctica where it is always covered with ice, or even at the top of mountains in the form of lichens, growing where otherwise nothing else could live.

Is the Earth unique because only this planet could have living things growing on it? It would seem unlikely that this is the only planet in the Universe that has living things like we know them, and it is suspected that there are many other places in the Solar System where life might be. If liquid water is discovered anywhere else in the Solar System, you might just find some living things there too. There are other worlds in the Solar System where liquid water indeed has been found, so many scientists continue to look for signs on life on other planets.

An interesting experiment was conducted in December, 1990, where the Galileo spacecraft, on a journey to Jupiter, went past the Earth after having gone on a orbit around the sun earlier. In this situation, the scientists who were running the space probe decided to test the equipment to see if they could detect signs of life on the Earth. In addition to simply taking pictures of the Earth, it also detected signs of water, oxygen, and other elements and chemicals that are necessary for life. This information was then used to both see if these same instruments could detect life elsewhere, and to calibrate the instruments to make more accurate measurements when it arrived at Jupiter.

What are earths moons like?

Earth has one permanent moon named Luna, or more commonly called the Moon. Earth also has a number of temporary natural satellites, the largest of which is the three-mile-wide body named Cruithne [pronounced 'KROOee-nyuh']. Discovered in 1986, Cruithne follows an eccentric horseshoe-shaped orbit that takes 770 years to complete.

How long is a day on the Earth?

A day on Earth is 24 hours long (solar) and 23 hours 56 minutes (sidereal). It is how long it takes the Earth to spin once on its axis.

How long is a year on the Earth?

A year on Earth is 365 days long. It is how long it takes Earth to orbit the sun once.

What is earth made of?

The Earth has a crust and mantle made of silicates and an inner and outer core. The crust is the surface layer. It is up to 5 km deep under the oceans and up to 35 km deep under the continents. Despite being so thin, scientists have not ever drilled all the way through the crust. The mantle extends from the bottom of the crust down to 2900 km under the surface. Under the mantle there is the liquid iron outer core. It extends from 2900 to 5100 km under the surface. At the center of Earth there is the solid inner core. It is made of iron and nickel.

How much would I weigh on Earth?

It's easy to find your weight on Earth by using a scale. You have weight because the Earth pulls you towards its center. (Normally, the ground or the floor get in the way, making you feel 'stuck' to them.) This force is known as gravity.

... There are several kinds of scales:

1. Comparing of 2 masses (weights). You put the thing(s) you want to weigh on one pan (like some marbles), and then you put several "weights" on the other pan until the pointer shows that both pans have equal weights on them. Then you look at the pan with the known weights on it, and add them all up. The total is the mass of the thing(s) you want to weigh.
2. A spring balance usually has a hook on it, with a pan. You put the thing(s) you want to weigh on the pan, the spring is pulled, and the greater the weight, the further the spring is pulled. That distance, calibrated in pounds or kilogram (or whatever), is usually shown either on a dial or on a linear scale.
3. There are also electronic scales that give a properly calibrated reading— grocery stores, for example, use these.

NOTE

gravity varies slightly depending on the location where you want to get the weight; spring balances and some electronic scales can, in theory, read slightly different weights at different places because of that, but usually in practice that difference it too small to be noticed. But, because the balance type of scales work differently to the spring or electronic types, they will always read the true, correct mass. The would even give the same mass on the moon! (where gravity is much less than on Earth)

Did you know?

that Sir Isaac Newton was the first person to realise that the force pulling you down to the ground was the same force that keeps the planets going around the sun? The story goes that he thought of this when he saw an apple fall from a tree.
Gravity is a very important force. As well as keeping you firmly stuck to the Earth, it keeps the Moon going round the Earth, The Earth going around the Sun and the Sun going around the center of the Milky Way galaxy. Gravity also makes stars and planets a nice round ball shape. In fact without gravity there wouldn't even be a sun, moon or earth. (The material that they are made of would just float away into space)



Who is it named after?

The word earth is used for both planet Earth and soil. Other names had been used for Earth such as Gaia and Tellus. Gaia is the Greek god of Earth. Tellus is the Roman name of the same god.

Earth has many kinds of environments. It is cold and icy in places like Antarctica. There are hot, dry deserts in some parts of the world like Africa and Arabia, and cold, dry deserts in some others like Siberia. Rain forests grow where it is warm and wet, in equatorial zones (these are areas a few hundred miles around a very hot 'line' called the equator. Outside equatorial zones there are areas of very dry, mostly hot desert, which is where all the water making the rainforests wet comes from, causing these areas to be very dry. Other kinds of forests grow between the Equator and the Poles, like the massive coniferous forests of pine and other trees which keep their leaves all the time, and deciduous forests of oak, beech and other leaf-losing plants. Some places are very wet and are called swamps or marshes. There are grasslands, many hot, some called savannahs, with lots of grass and few trees. There are also mountains, caused by collision of tectonic plates. Some of them are high with snow and ice on their tops all year. Others are lower and more rounded.

Is there life on the Earth?

When this question is asked on other planets in the solar system, it is important to know where you might find living things here on the Earth. Almost every important feature of the surface of the earth is in some way affected by living things, including mineral deposits and even the content of the air that we breathe.

One of the critical ingredients that all living things seem to need is water. Wherever you find liquid water, you will almost always find living things, even if it is not a place where you would want to live as a person. Bacteria has been found inside gysers, where the water temperature can be over 300° C. These living things not only live there, but even seem to need those very high temperatures. Other living things have been found on the bottom of the ocean, living around "thermal vents" where the only energy they obtain is from lava heating up water. It is so deep in the ocean that no sunlight ever appears there. Finally, you can find living things in Antarctica where it is always covered with ice, or even at the top of mountains in the form of lichens, growing where otherwise nothing else could live.

Is the Earth unique because only this planet could have living things growing on it? It would seem unlikely that this is the only planet in the Universe that has living things like we know them, and it is suspected that there are many other places in the Solar System where life might be. If liquid water is discovered anywhere else in the Solar System, you might just find some living things there too. There are other worlds in the Solar System where liquid water indeed has been found, so many scientists continue to look for signs on life on other planets.

An interesting experiment was conducted in December, 1990, where the Galileo spacecraft, on a journey to Jupiter, went past the Earth after having gone on a orbit around the sun earlier. In this situation, the scientists who were running the space probe decided to test the equipment to see if they could detect signs of life on the Earth. In addition to simply taking pictures of the Earth, it also detected signs of water, oxygen, and other elements and chemicals that are necessary for life. This information was then used to both see if these same instruments could detect life elsewhere, and to calibrate the instruments to make more accurate measurements when it arrived at Jupiter.

What are earths moons like?

Earth has one permanent moon named Luna, or more commonly called the Moon. Earth also has a number of temporary natural satellites, the largest of which is the three-mile-wide body named Cruithne [pronounced 'KROOee-nyuh']. Discovered in 1986, Cruithne follows an eccentric horseshoe-shaped orbit that takes 770 years to complete.

How long is a day on the Earth?

A day on Earth is 24 hours long (solar) and 23 hours 56 minutes (sidereal). It is how long it takes the Earth to spin once on its axis.

How long is a year on the Earth?

A year on Earth is 365 days long. It is how long it takes Earth to orbit the sun once.

What is earth made of?



The Earth has a crust and mantle made of silicates and an inner and outer core. The crust is the surface layer. It is up to 5 km deep under the oceans and up to 35 km deep under the continents. Despite being so thin, scientists have not ever drilled all the way through the crust. The mantle extends from the bottom of the crust down to 2900 km under the surface. Under the mantle there is the liquid iron outer core. It extends from 2900 to 5100 km under the surface. At the center of Earth there is the solid inner core. It is made of iron and nickel.

How much would I weigh on Earth?

It's easy to find your weight on Earth by using a scale. You have weight because the Earth pulls you towards its center. (Normally, the ground or the floor get in the way, making you feel 'stuck' to them.) This force is known as gravity.

... There are several kinds of scales:

1. Comparing of 2 masses (weights). You put the thing(s) you want to weigh on one pan (like some marbles), and then you put several "weights" on the other pan until the pointer shows that both pans have equal weights on them. Then you look at the pan with the known weights on it, and add them all up. The total is the mass of the thing(s) you want to weigh.
2. A spring balance usually has a hook on it, with a pan. You put the thing(s) you want to weigh on the pan, the spring is pulled, and the greater the weight, the further the spring is pulled. That distance, calibrated in pounds or kilogram (or whatever), is usually shown either on a dial or on a linear scale.
3. There are also electronic scales that give a properly calibrated reading— grocery stores, for example, use these.

NOTE

gravity varies slightly depending on the location where you want to get the weight; spring balances and some electronic scales can, in theory, read slightly different weights at different places because of that, but usually in practice that difference it too small to be noticed. But, because the balance type of scales work differently to the spring or electronic types, they will always read the true, correct mass. The would even give the same mass on the moon! (where gravity is much less than on Earth)

Did you know?

that Sir Isaac Newton was the first person to realise that the force pulling you down to the ground was the same force that keeps the planets going around the sun? The story goes that he thought of this when he saw an apple fall from a tree.
Gravity is a very important force. As well as keeping you firmly stuck to the Earth, it keeps the Moon going round the Earth, The Earth going around the Sun and the Sun going around the center of the Milky Way galaxy. Gravity also makes stars and planets a nice round ball shape. In fact without gravity there wouldn't even be a sun, moon or earth. (The material that they are made of would just float away into space)



Who is it named after?

The word earth is used for both planet Earth and soil. Other names had been used for Earth such as Gaia and Tellus. Gaia is the Greek god of Earth. Tellus is the Roman name of the same god.