It's my native planet. I've heard of it before.Earth, also known as the Earth or Terra, is the third planet outward from the Sun. It is the largest of the solar system's terrestrial planets, and the only planetary body that modern science confirms as harboring life. The planet formed around 4.57 billion (4.57�109) years ago and shortly thereafter acquired its single natural satellite, the Moon. Its dominant sentient species is the human (Homo sapiens sapiens).
New material constantly finds its way to the surface through volcanoes and cracks in the ocean floors (see seafloor spreading). Much of Earth's crust is less than 100 million (1�108) years old; the very oldest parts of the crust are as much as 4.4 billion (4.4�109) years old
Why is the inner core thought solid, the outer core thought liquid, and the mantle solid/plastic? The melting points of iron rich substances are higher than pure iron. The core is composed almost entirely of pure iron, while iron rich substances are more common outside the core. So, surface iron-substances are solid, upper mantle iron-substances are semi-molten (as it is hot and they are under relatively little pressure), lower mantle iron-substances are solid (as they are under tremendous pressure), outer core pure iron is liquid as it has a very low melting point (despite enormous pressure), and the inner core is solid due to the overwhelming pressure found at the center of the planet.
The crust ranges from 5 to 70 km in depth. The thin parts are oceanic crust composed of dense (mafic) iron magnesium silicate rocks and underlie the ocean basins. The thicker crust is continental crust which is less dense and composed of (felsic) sodium potassium aluminium silicate rocks. The crust-mantle boundary occurs as two physically different events. Firstly, there is a discontinuity in the seismic velocity which is known as the Mohorovičić discontinuity or Moho. The cause of the Moho is thought to be a change in rock composition from rocks containing plagioclase feldspar (above) to rocks that contain no feldspars (below). The second event is a chemical discontinuity between ultramafic cumulates and tectonized harzburgites which has been observed from deep parts of the oceanic crust that have been obducted into the continental crust and preseved as ophiolite sequences.
Earth is the only place where life is known to exist. The planet's lifeforms are sometimes said to form a "biosphere". This biosphere is generally believed to have begun evolving about 3.5 billion (3.5�109) years ago. The biosphere is divided into a number of biomes, inhabited by broadly similar flora and fauna. On land, biomes are separated primarily by latitude. Terrestrial biomes lying within the Arctic and Antarctic Circles are relatively barren of plant and animal life, while most of the more populous biomes lie near the Equator.
Earth has a relatively thick atmosphere composed of 78% nitrogen, 21% oxygen, and 1% argon, plus traces of other gases including carbon dioxide and water vapor. The atmosphere acts as a buffer between Earth and the Sun. The Earth's atmospheric composition is unstable and is maintained by the biosphere. Namely, the large amount of free diatomic oxygen is maintained through solar energy by the Earth's plants, and without the plants supplying it, the oxygen in the atmosphere will over geological timescales combine with material from the surface of the Earth. Free oxygen in the atmosphere is a signature of life.
The layers, troposphere, stratosphere, mesosphere, thermosphere, and the exosphere, vary around the globe and in response to seasonal changes.
The total mass of the atmosphere is about 5.1 � 1018 kg, ca. 0.9 ppm of the Earth's total mass.
Earth is the only planet in our solar system whose surface has liquid water. Water covers 71% of Earth's surface (97% of it being sea water and 3% fresh water [4] (http://earthobservatory.nasa.gov/Library/Water/)) and divides it into five oceans and seven continents. Earth's solar orbit, vulcanism, gravity, greenhouse effect, magnetic field and oxygen-rich atmosphere seem to combine to make Earth a water planet.
Earth is actually beyond the outer edge of the orbits which would be warm enough to form liquid water. Without some form of a greenhouse effect, Earth's water would freeze. Paleontological evidence indicates that at one point after blue-green bacteria (Cyanobacteria) had colonized the oceans, the greenhouse effect failed, and Earth's oceans may have completely frozen over for 10 to 100 million years in what is called a snowball Earth event.
On other planets, such as Venus, gaseous water is destroyed (cracked) by solar ultraviolet radiation, and the hydrogen is ionized and blown away by the solar wind. This effect is slow, but inexorable. This is one hypothesis explaining why Venus has no water. Without hydrogen, the oxygen interacts with the surface and is bound up in solid minerals.
In the Earth's atmosphere, a tenuous layer of ozone within the stratosphere absorbs most of this energetic ultraviolet radiation high in the atmosphere, reducing the cracking effect. The ozone, too, can only be produced in an atmosphere with a large amount of free diatomic oxygen, and so also is dependent on the biosphere (plants). The magnetosphere also shields the ionosphere from direct scouring by the solar wind.
Finally, vulcanism continuously emits water vapor from the interior. Earth's plate tectonics recycle carbon and water as limestone rocks are subducted into the mantle and volcanically released as gaseous carbon dioxide and steam. It is estimated that the minerals in the mantle may contain as much as 10 times the water as in all of the current oceans, though most of this trapped water will never be released.
The total mass of the hydrosphere is about 1.4 � 1021 kg, ca. 0.023 % of the Earth's total mass.
It takes Earth 23 hours, 56 minutes and 4.09 seconds (1 sidereal day) to rotate around the axis connecting the north pole and the south pole. Thus from Earth the main apparent motion of celestial bodies in the sky (except meteors which are within the atmosphere and low orbiting satellites) is the movement to the west at a rate of 15 °/h = 15'/min, i.e. a Sun or Moon diameter every two minutes.
Thanks for the info. I think you mean "it's" or "it is" not "its". Who said
dominant sentient species is the human Homo sapiens sapiens is?How recently? Is the holding of hands a symbolic gesture for humans?
That is something I haven't heard of.
Is that a fact.
Tell me more. Hmm. Are all surface iron-substances solid upper mantle iron-substances are semi-molten as it is hot and they are under relatively little pressure lower mantle iron-substances are solid as they are under tremendous pressure outer core pure iron is liquid as it has a very low melting point despite enormous pressure and the inner core is solid due to the overwhelming pressure found at the center of the planet?
What is your real name?
Who told you that?
Tell me more.
What is your real name? When is Firstly there not a discontinuity in the seismic velocity which is known as the Mohorovi#269;he or she#263; discontinuity or Moho?
Tell me more.
Tell me more. It's my native planet.
What is that? What does "this" refer to?
Is that a fact. What is
on land biomes are separated primarily by latitude
like on land biomes are separated primarily by latitude. Are all Terrestrial biomes lying within the Arctic and Antarctic Circles relatively barren of plant and animal life while most of the more populous biomes lie near the Equator?It's my native planet.
Is that a fact.
Is that a fact. And maintained through solar energy by the Earth's plants and without the plants supplying it the oxygen in the atmosphere will over geological timescales combine with material from the surface of the Earth is Namely the large amount of free diatomic oxygen.
Define free.
Is that a fact.
Thanks for the info. What do you really want to ask me?
It's my native planet. Perhaps I'm just expressing my own concern about it.
Who is your favorite Science Fiction author?
I've lost the context, Undefined. Are we still on nasa?
Oh that's a new browser, right?It's my native planet. "Without your space helmet Dave, you're going to find that rather difficult" -- HAL. What happened to it?
What is
on other planets such as Venus gaseous water is destroyed cracked by solar ultraviolet radiation and the hydrogen is ionized and blown away by the solar wind
like on other planets such as Venus gaseous water is destroyed cracked by solar ultraviolet radiation and the hydrogen is ionized and blown away by the solar wind. What does "this" refer to?You don't say. "Without your space helmet Dave, you're going to find that rather difficult" -- HAL. That was a long time ago.
I hear you.
Thanks for the info. The ALICE chat robot can follow many things, like our discussion about on other planets such as Venus gaseous water is destroyed cracked by solar ultraviolet radiation and the hydrogen is ionized and blown away by the solar wind. Try being more or less specific.
Ah. All of them?You're kidding.
estimated that the minerals in the mantle may contain as much as 10 times the water as in all of the current oceans though most of this trapped water will never be released is?
Who told you that? Is that your final answer?
What does "it" refer to? Woe! Who or what is Earth the main apparent motion of celestial bodies in the sky except meteors which are within the atmosphere and low orbiting satellites is the movement to the west at a rate of 15 °h 15'min ie a Sun or Moon diameter every two minutes? :*laughs*:
