Earth

Earth ﻿( home of the human being )



1 M⊕ = 5.9742 × 1024 kg. Earth mass is often used to describe masses of rocky terrestrial planets.http://www.google.com/search?hl=en&rls=com Earth: 3rd planet Distance:The average distance between the sun and the earth is 149 million kilometers (93 million miles). Number of moons: 1

"All the planets except Earth were named after Greek Gods and Godesses. It comes from the words "eor(th)e, ertha, and erde" which are English and German names meaning "the ground." The Earth was created 4.54 billion years ago when part of the Sun's accretion disc agglomerated into a spherical body. At that time, shortly after the birth of the Sun itself, the solar system's matter was much more scattered around, in the form of asteroids and dust rather than planets. This "matter cloud" has been called a Bok globule, and these globules have been observed in other parts of the [|Galaxy]. Scientists have determined the age of the Earth relatively precisely using [|isotope] dating of the world's oldest rocks." []

Ever wonder what the very center of the earth looked like or what its called? "The interior structure of the Earth, similar to the outer, is layered. These layers can be defined by either their [|chemical] or their [|rheological] properties. The [|Earth] has an outer [|silicate] solid [|crust], a highly [|viscous] [|mantle], a liquid [|outer core] that is much less viscous than the mantle, and a solid [|inner core]. Scientific understanding of Earth's internal structure is based on observations of [|topography] and [|bathymetry], observations of [|rock] in [|outcrop], samples brought to the surface from greater depths by volcanic activity, analysis of the [|seismic waves] that pass through the Earth, measurements of the [|gravity] field of the Earth, and experiments with crystalline solids at pressures and temperatures characteristic of the Earth's deep interior."http://en.wikipedia.org/wiki/Structure_of_the_Earth Unfamiliar Life-Forms "The first multicelled animals appeared in the fossil record almost 600 million years ago. Known as the Ediacarans, these bizarre creatures bore little resemblance to modern life-forms. They grew on the seabed and lacked any obvious heads, mouths, or digestive organs. Fossils of the largest known among them, Dickinsonia, resemble a ribbed doormat. What happened to the mysterious Ediacarans isn't clear. They could be the ancestors of later animals, or they may have been completely erased by extinction." "The earliest multicelled animals that survived the Precambrian fall into three main categories. The simplest of these soft-bodied creatures were sponges. Lacking organs or a nervous system, they lived by drawing water through their bodies and filtering out food particles. The cnidarians, which included sea anemones, corals, and jellyfish, had sac-like bodies and a simple digestive system with a mouth but no anus. They caught food using tentacles armed with microscopic stinging cells. The third group, the annelids, or segmented flatworms, had fluid-filled body cavities and breathed through their skins." "It's thought the final stages of Precambrian time were marked by a prolonged global ice age. This may have led to widespread extinctions, mirroring the bleak endings to the geologic periods that followed." "In the very beginning of earth's history, this planet was a giant, red hot, roiling, boiling sea of molten rock - a magma ocean. The heat had been generated by the repeated high speed collisions of much smaller bodies of space rocks that continually clumped together as they collided to form this planet. As the collisions tapered off the earth began to cool, forming a thin crust on its surface. As the cooling continued, water vapor began to escape and condense in the earth's early atmosphere. Clouds formed and storms raged, raining more and more water down on the primitive earth, cooling the surface further until it was flooded with water, forming the seas." ==== "It is theorized that the true age of the earth is about 4.6 billion years old, formed at about the same time as the rest of our [|solar system] . The oldest rocks geologists have been able to find are 3.9 billion years old. Using //radiometric dating// methods to determine the age of rocks means scientists have to rely on when the rock was initially formed (as in - when its internal minerals first cooled). In the infancy of our home planet the entire earth was molten (melted) rock - a magma ocean." ==== ==== "Since we can only measure as far back in time as we had solid rock on this planet, we are limited in how we can measure the real age of the earth. Due to the forces of [|//plate tectonics//], our planet is also a very dynamic one; new mountains forming, old ones" ==== ==== "wearing down, volcanoes melting and reshaping new crust. The continual changing and reshaping of the earth's surface that involves the melting down and reconstructing of old rock has pretty much eliminated most of the original rocks that came with earth when it was newly formed. So the age is a theoretical age." [] ==== ==== "The moon is [|Earth]'s closest celestial neighbor. It has a huge influence upon our lives, governs the tides (the [|sun] plays a small part, but not nearly as much as the Moon), and is responsible for eclipses. Some biologists say that the moon is even responsible - in part - for life on Earth, for without the tides causing currents and mixing of chemicals, life might never have formed. ==== The moon lies, on average, 384,400 km (238,900 miles) away and takes 27.3 days to orbit the Earth. Strange as it may seem, its rotation period is exactly the same as its orbital period, something that scientists call [|tidally locked]. Therefore, one half is always facing the Earth while the other half is always facing away. This means that there isn't really a "Dark Side" of the moon. Also, contrary to popular opinion, there have been people on the far side, and it has been extensively photographed and mapped." 

**The Earth’s Atmosphere **

★ ﻿The Troposhere "Troposphere means, ‘where the air turns over’. A very appropriate name, since the air closest to the earth is in a constant up and down flow. Also in this layer, the air is hotter closer to the earth’s surface and colder the higher up you travel. The troposphere is immediately important in our daily activities. Starting at sea level, the troposphere goes up seven miles. The bottom one third, that which is closest to us, contains 50% of all atmospheric gases. This is the only part of the whole makeup of the atmosphere that is breathable. This is the only area where all weather takes place. It also has the property of having a north –south oriented aspect. The air from the northern hemisphere and the air from the southern hemisphere meet and mingle at the equator, but never go farther. Next, is a thin layer called the tropopause, which is just a buffer between the troposphere and the stratosphere." ★The Stratosphere "The stratosphere is the next layer of the atmosphere. Here the air doesn’t flow up and down, but flows parallel to the earth in very fast moving air streams. This is the layer where most jet planes fly. The stratosphere starts at approximately 10 kilometers (8-14.5 miles) and goes to approximately fifty kilometers high (about 30 miles). The top edge of the stratosphere is abundant with ozone. Ozone is the byproduct of sun radiation and oxygen; by capturing the ultraviolet rays of the sun and deploying it, ozone takes out the harmful effects. This is very important to all living things on earth, since unfiltered radiation from the sun can destroy all animal tissue. After the stratosphere, there is again a buffer layer, this time called the stratopause."

★The Mesosphere "Above this from thirty miles up to fifty miles is the mesosphere. This area reaches the coldest temperatures of all the atmosphere, going to -130 degrees and lower. Here, meteors coming too close to earth burn up."

★The Thermosphere "The last layer of the atmosphere called the thermosphere, and measured at fifty to ninety miles above earth, contains less than 0.01% of all air within the atmospheric envelope. Temperatures here reach upward to 2000 degrees, but the gas molecules making up the air are so far apart the temperature is not felt." http://weather.about.com/od/weathertutorials/a/atmoslayers.htm