Iron catastrophehttps://en.wikipedia.org/wiki/Iron_catastropheThe iron catastrophe was a postulated major event early in the history of Earth. The original accretion of the Earth's material into a spherical mass is thought to have resulted in a relatively uniform composition. While residual heat from the collision of the material that formed the Earth was significant, heating from radioactive materials in this mass gradually increased the temperature until a critical condition was reached. As material became molten enough to allow movement, the denser iron and nickel, evenly distributed throughout the mass, began to migrate to the center of the planet to form the core. The gravitational potential energy released by the sinking of the dense NiFe globules, along with any cooler denser solid material is thought to have been a runaway process, increasing the temperature of the protoplanet above the melting point of most components, resulting in the rapid formation of a molten iron core covered by a deep global silicate magma. This event, an important process of planetary differentiation, occurred at about 500 million years into the formation of the planet.[1]
Earth's Inconstant Magnetic Field http://science.nasa.gov/science-news/science-at-nasa/2003/29dec_magneticfield/At the heart of our planet lies a solid iron ball, about as hot as the surface of the sun. Researchers call it "the inner core." It's really a world within a world. The inner core is 70% as wide as the moon. It spins at its own rate, as much as 0.2° of longitude per year faster than the Earth above it, and it has its own ocean: a very deep layer of liquid iron known as "the outer core."
see captionRight: a schematic diagram of Earth's interior. The outer core is the source of the geomagnetic field.
Earth's magnetic field comes from this ocean of iron, which is an electrically conducting fluid in constant motion. Sitting atop the hot inner core, the liquid outer core seethes and roils like water in a pan on a hot stove. The outer core also has "hurricanes"--whirlpools powered by the Coriolis forces of Earth's rotation. These complex motions generate our planet's magnetism through a process called the dynamo effect.
Using the equations of magnetohydrodynamics, a branch of physics dealing with conducting fluids and magnetic fields, Glatzmaier and colleague Paul Roberts have created a supercomputer model of Earth's interior. Their software heats the inner core, stirs the metallic ocean above it, then calculates the resulting magnetic field. They run their code for hundreds of thousands of simulated years and watch what happens.
What they see mimics the real Earth: The magnetic field waxes and wanes, poles drift and, occasionally, flip. Change is normal, they've learned. And no wonder. The source of the field, the outer core, is itself seething, swirling, turbulent. "It's chaotic down there," notes Glatzmaier. The changes we detect on our planet's surface are a sign of that inner chaos.
They've also learned what happens during a magnetic flip. Reversals take a few thousand years to complete, and during that time--contrary to popular belief--the magnetic field does not vanish. "It just gets more complicated," says Glatzmaier. Magnetic lines of force near Earth's surface become twisted and tangled, and magnetic poles pop up in unaccustomed places. A south magnetic pole might emerge over Africa, for instance, or a north pole over Tahiti. Weird. But it's still a planetary magnetic field, and it still protects us from space radiation and solar storms.
Finally, a Solid Look at Earth's Corehttp://www.livescience.com/6980-finally-solid-earth-core.htmlScientists have long thought Earth's core is solid. Now they have some solid evidence.
The core is thought to be a two-part construction. The inner core is solid iron, and that's surrounding by a molten core, theory holds. Around the core is the mantle, and near the planet's surface is a thin crust -- the part that breaks now and then and creates earthquakes.
The core was discovered in 1936 by monitoring the internal rumbles of earthquakes, which send seismic waves rippling through the planet. The waves, which are much like sound waves, are bent when they pass through layers of differing densities, just as light is bent as it enters water. By noting a wave's travel time, much can be inferred about the Earth's insides.
Yet for more than 60 years, the solidity of the core has remained in the realm of theory.
A study announced today involved complex monitoring of seismic waves passing through the planet. The technique is not new, but this is the first time it's been employed so effectively to probe the heart of our world.
First, some jargon:
P is what scientists call the wave
K stands for the outer core
J is the inner core
Path of a PKJKP wave.
? Science
So a wave that rolls through it all is called PKJKP.
An earthquake sends seismic waves in all directions. The surface waves are sometimes frighteningly obvious. Seismic waves passing through the mantle and traversing much of the planet's interior are routinely studied when they reach another continent. But no PKJKP wave has ever been reliably detected until now.
Aimin Cao of the University of California-Berkeley and colleagues studied archived data from about 20 large earthquakes, all monitored by an array of German seismic detectors back in the 1980s and '90s.
The trick to detecting a PKJKP wave is in noting the changes it goes through as it rattles from one side of the planet to the other. What starts out as a compression wave changes to what scientists call a shear wave (explanations and animations of these are here).
"A PKJKP traverses the inner core as a shear wave, so this is the direct evidence that the inner core is solid," Cao told LiveScience, "because only in the solid material the shear wave can exist. In the liquid material, say water, only the compressional wave can travel through."
The arrival time and slowness of the waves agree with theoretical predictions of PKJKP waves, which indicates a solid core. The results were published today online by the journal Science.
Clausius–Clapeyron relationhttps://en.wikipedia.org/wiki/Clausius%E2%80%93Clapeyron_relation"Clapeyron equation" and "Clapeyron's equation" redirect here. For a state equation, see ideal gas law.
The Clausius–Clapeyron relation, named after Rudolf Clausius[1] and Benoît Paul Émile Clapeyron,[2] is a way of characterizing a discontinuous phase transition between two phases of matter of a single constituent. On a pressure–temperature (P–T) diagram, the line separating the two phases is known as the coexistence curve. The Clausius–Clapeyron relation gives the slope of the tangents to this curve. Mathematically,
\frac{\mathrm{d}P}{\mathrm{d}T} = \frac{L}{T\,\Delta v}=\frac{\Delta s}{\Delta v},
where \mathrm{d}P/\mathrm{d}T is the slope of the tangent to the coexistence curve at any point, L is the specific latent heat, T is the temperature, \Delta v is the specific volume change of the phase transition, and \Delta s is the specific entropy change of the phase transition.
Newton's law of universal gravitationhttps://en.wikipedia.org/wiki/Newton's_law_of_universal_gravitationNewton's law of universal gravitation states that any two bodies in the Universe attract each other with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.[note 1] This is a general physical law derived from empirical observations by what Isaac Newton called induction.[1] It is a part of classical mechanics and was formulated in Newton's work Philosophiæ Naturalis Principia Mathematica ("the Principia"), first published on 5 July 1687. (When Newton's book was presented in 1686 to the Royal Society, Robert Hooke made a claim that Newton had obtained the inverse square law from him; see the History section below.)
In modern language, the law states: Every point mass attracts every single other point mass by a force pointing along the line intersecting both points. The force is proportional to the product of the two masses and inversely proportional to the square of the distance between them.[2] The first test of Newton's theory of gravitation between masses in the laboratory was the Cavendish experiment conducted by the British scientist Henry Cavendish in 1798.[3] It took place 111 years after the publication of Newton's Principia and 71 years after his death.
Newton's law of gravitation resembles Coulomb's law of electrical forces, which is used to calculate the magnitude of electrical force arising between two charged bodies. Both are inverse-square laws, where force is inversely proportional to the square of the distance between the bodies. Coulomb's law has the product of two charges in place of the product of the masses, and the electrostatic constant in place of the gravitational constant.
Newton's law has since been superseded by Einstein's theory of general relativity, but it continues to be used as an excellent approximation of the effects of gravity in most applications. Relativity is required only when there is a need for extreme precision, or when dealing with very strong gravitational fields, such as those found near extremely massive and dense objects, or at very close distances (such as Mercury's orbit around the sun).
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