EARTH Terra firma, globe, macrocosm, old sod, orb, planet, spaceship Earth, sphere, sublunary world, Home. americansector.blogspot.com

Big Bang In the beginning there is only a super-massive gaseous point in our empty universe. Instantaneously and randomly, enough energy is created to break the gravitational bond holding this massive body together, exploding the super- heated particles throughout space. In less than one millionth of a second, protons, neutrons, electrons, and their anti-particles begin to form.

Big Bang plus Time As time moves on, particles begin to cool by giving off energy, which allows them to combine to create the first and most simple ion, hydrogen, as well as a few more massive atoms.

Big Bang plus more Time More time passes; the atoms are becoming more abundant in the universe. They begin to pull together through atomic forces and the gravitational force.

The Earth was one of the planets formed from the collapse of the first star. However, it is unique in many ways. It is the only planet with visible surface water, which is explained by the precise temperature and atmospheric pressure the Earth maintains.

Got Life? Earth's atmosphere is also unique, in that it contains oxygen, which is essential for life.

Seasons The Earth's axis is tilted approximately 23 degrees.

Crunch!!! Or Hit and Run… At one time, a large asteroid may have collided with the planet, breaking off a large piece of it, which would eventually become our Moon. bang.htmhttp://mediatheek.thinkquest.nl/~ll125/en/big bang.htm homepage.smc.edu

Steps in the accretion process: Step 1: Step 1: accretion of cm sized particles Step 2: Step 2: Physical Collision on km scale Step 3: Step 3: Gravitational accretion on km scale anhttp://zebu.uoregon.edu/ph121/l7.html oxygen-silicon crust

Step 4: Molten protoplanet from the heat of accretion.Step 4: Step 5: Final step is differentiation of the earth: Light objects float; heavy objects sink.Step 5: Iron-Nickel Core (magnetic field), or is it? A new theory concerning the formation of the core states that the core may in fact be a nuclear reactor. anhttp://zebu.uoregon.edu/ph121/l7.html oxygen-silicon crust

Things to note about the formation of planets via accretion There is a lot of heat dissipated in the final accretion process resulting in initially molten objects. Any molten object of size greater than about 500 km has sufficient gravity to cause gravitational separation of light and heavy elements thus producing a differentiated body.

The accretion process is inefficient: there is lots of left over debris. In the inner part of the solar system, the leftover rocky debris cratered the surfaces of the newly formed planets. my/moon/Craters.shtml

Leftovers again? In the outer part of the solar system, much of the leftover rocky debris was ejected from the solar system due to the large masses of the planets which formed there.

How Thick are Earth’s Layer? The earth’s four layers: the crust, mantle, inner core, and outer core. The lithosphere is the crust and the upper part of the mantle. The lithosphere is about 5 to 30 miles deep. The mantle is about 1800 miles thick. The outer core is about 1300 miles thick. The inner core is about 800 miles to the center of the earth.

FOUR MAIN LAYERS The earth is divided into four main layers: the inner core, outer core, mantle, and crust. The core is composed mostly of iron (Fe) and is so hot that the outer core is molten, with about 10% sulphur (S).

The Earth has the Layered Look The crust is a thin rocky skin. The thinnest part of the crust is under the ocean. The ocean floor is heavy, dense rock and the land is lighter, less dense rock.

Mantle and Crust At over 1000 degrees C, the mantle is solid but can deform slowly in a plastic manner. The crust is much thinner than any of the other layers, and is composed of the least dense calcium (Ca) and sodium (Na) aluminum-silicate minerals. Being relatively cold, the crust is rocky and brittle, so it can fracture in earthquakes.

Deep Mantle The deep mantle is very hot because it rides on top of the extremely hot outer core and therefore it causes the mantle and crust to slowly move.

Inner Core The inner core is under such extreme pressure that it remains solid. Most of the Earth's mass is in the mantle, which is composed of iron (Fe), magnesium (Mg), aluminum (Al), silicon (Si), and oxygen (O) silicate compounds.

Electromagnetic Field

The origin of the Earth's magnetic field is not completely understood, but is thought to be associated with electrical currents produced by the coupling of convective effects and rotation in the spinning liquid metallic outer core of iron and nickel. This mechanism is termed the dynamo effect.

Solar Wind The solar wind is a stream of ionized gases that blows outward from the Sun at about 400 km/second and that varies in intensity with the amount of surface activity on the Sun. The Earth's magnetic field shields it from much of the solar wind. When the solar wind encounters Earth's magnetic field it is deflected like water around the bow of a ship, as illustrated in the following image.

Van Allen Belts The Earth has two regions of trapped fast particles. The inner radiation belt discovered by Van Allen is relatively compact, extending perhaps one Earth radius above the equator (1 RE = 6371 km or about 4000 miles). It consists of very energetic protons, a by-product of collisions by cosmic ray ions with atoms of the atmosphere.

Van Allen Belts

Van Allen Belts become Radioactive The number of such ions is relatively small, and the inner belt therefore accumulates slowly, but because trapping near Earth is very stable, rather high intensities are reached, even though their build-up may take years.

That’s all Folks The End