what is the strength of the earth magnetic feild?
108424
Earth's magnetic field (and the surface magnetic field) is approximately a magnetic dipole, with one pole near the geographic north pole and the other near the geographic south pole. An imaginary line joining the magnetic poles would be inclined by approximately 11.3° from the planet's axis of rotation. The cause of the field is probably explained by dynamo theory. The magnetic field extends several tens of thousands of kilometres into space as the magnetosphere\n\nThe locations of the magnetic poles are not static but wander as much as 15km every year (Dr. David P. Stern, emeritus Goddard Space Flight Center, NASA). The two poles wander independently of each other and are not at directly opposite positions on the globe. Currently the south magnetic pole is farther from the geographic south pole than the north magnetic pole is from the north geographic pole.\n\nThe field is similar to that of a bar magnet, but this similarity is superficial. The magnetic field of a bar magnet, or any other type of permanent magnet, is created by the coordinated motions of electrons (negatively charged particles) within iron atoms. The Earth's core, however, is hotter than 1043 K, the Curie point temperature at which the orientations of electron orbits within iron become randomized. Such randomization tends to cause the substance to lose its magnetic field. Therefore the Earth's magnetic field is caused not by magnetised iron deposits, but mostly by electric currents in the liquid outer core.\n\nAnother feature that distinguishes the Earth magnetically from a bar magnet is its magnetosphere. At large distances from the planet, this dominates the surface magnetic field.\n\nElectric currents induced in the ionosphere also generate magnetic fields. Such a field is always generated near where the atmosphere is closest to the Sun, causing daily alterations which can deflect surface magnetic fields by as much as one degree.\n\nMagnetic field variations\n \nGeomagnetic variations since last reversal.The strength of the field at the Earth's surface ranges from less than 30 microteslas (0.3 gauss) in an area including most of South America and South Africa to over 60 microteslas (0.6 gauss) around the magnetic poles in northern Canada and south of Australia, and in part of Siberia.\n\nMagnetometers detect minute deviations in the Earth's magnetic field caused by iron artefacts, kilns, some types of stone structures, and even ditches and middens in geophysical survey. Using the magnetic instruments adapted from airborne devices developed during World War II to detect submarines, the magnetic variations across the ocean floor have been mapped. The basalt -- the iron-rich, volcanic rock making up the ocean floor -- contains a strongly magnetic mineral (magnetite) and can locally distort compass readings. The distortion was recognized by Icelandic mariners as early as the late 18th century. More important, because the presence of magnetite gives the basalt measurable magnetic properties, these magnetic variations have provided another means to study the deep ocean floor. When newly formed rock cools, such magnetic materials record the Earth's magnetic field.\n\nIn October 2003, the Earth's magnetosphere was hit by a solar flare causing a brief but intense geomagnetic storm, provoking unusual displays of aurorae.\n\nMagnetic field reversals\n\n\n\nMain article: geomagnetic reversal \nBased upon the study of lava formations in Hawaii, it has been deduced that the Earth's magnetic field reverses at intervals, ranging from tens of thousands to many millions of years, with an average interval of approximately 250,000 years. The last such event, called the Brunhes-Matuyama reversal, occurred some 780,000 years ago.\n\nThe mechanism responsible for geomagnetic reversals is not well understood. Some scientists have produced models for the core of the Earth wherein the magnetic field is only quasi-stable and the poles can spontan
1033042
The earth IS protected from solar flares.  Unlike most other planets we have analyzed, the earth has an EMF field around it.  Its like a magnet.  Magnets have a North (positive) pole and a South (Negative) Pole.  Electro-Motive Force (EMF) is a flow of electrons from the negative pole to the positive pole.  This flow of electrons acts like a shield and deflects solar flares from reaching the earth.  Now, its not absolute!  There are actually some solar flares that do indeed reach us, but I think this is a bit much for this forum.  I hope this helps!
270208
Intensity of current and magnetic permeability of the core.
375243
1) Assuming there are no strong EM fields near the magnet, it should behave exactly as a similar object would due to gravity. The gravitational field of the earth is too weak to produce a measurable effect for this experiment.\n\n2) You need a very long liquid filled container with a speaker on one side and a microphone on the other. Then using a computer to produce and receive the sounds, measure the time taken for the sound to traverse the distance. For accurate results the water needs be still.
674108
The poles of any magnetized item will be at the extreme opposite points...in other words the positive will be as far as it can get from the negative.  In the case of a sphere this would be "top" and "bottom" not core and perimeter.  (Think of the Earth's magnetic poles!).
823892
In this reference, http://en.wikipedia.org/wiki/Magnets near the end of the article there is a formula for the force between bar magnets very close together.  You wll need to know the magnetic field strength of the magnet.  Also, for sliding, you will need to know the coefficient of friction.
792355
The nature of Earth's core is known from several types of evidence.  First, we know the mass of the Earth from applying the laws of gravity to orbital information about the Moon.  The enables scientists to calculate information about the density of the portions of the Earth that are deeper than the locations from which any samples have been obtained.  This lets the scientists make deductions about what substances are present in the core.  Secondly, the Earth's magnetic field tells us that a conductor is moving inside the Earth.  This is the solid iron core, surrounded by molten iron.  Additional information about this structure is gained through seismic analysis.
89051
On average, about once every 250,000 years or so Earth's two magnetic poles switch---the north magnetic pole becomes the south magnetic pole, and the south magnetic pole becomes the north magnetic pole. This means, among many other things, that compasses would all point south instead of north.\n\nScience knows that these pole reversals do happen. Some ancient rocks tell the story. In the far distant past these rocks were molten. At those times their interior materials would align themselves to Earth's magnetic field, much the way an electromagnet will. Careful analysis shows that the magnetic lines of force imbedded in these rocks often were directly opposite to Earth's present magnetic field.\n\nThe last pole reversal happened some 700,000 years ago, so we're sort of overdue for another one.
129623
The dynamo theory (that the earth is maganetic) is actually due to the fact that the outer crust is molten iron.  This iron is moving around inside the earth at very high temperatures.  Physics tells us that moving metals will create  a magnetic field.  This is why we have the magnetic field around the earth.
578157
3200 Degrees C.\n\n"The outer core, which is responsible for the Earth's magnetic field, contains about 29.3% of the Earth's mass and has an average density of 12200-9900kg/m3 and temperature of 3200 degrees C."\nhttp://www.cobweb.net/~bug2/rock7.htm
1145043
Gravity certainly is the weakest force, and your reasoning was pretty good - as a very rough comparison of the strength of the gravitational force compared to the electromagnetic force, your magnet situation is quite neat...\nThe gravity exerted by a body varies with it's mass, and your lump of metal, a paper clip say, stays on the desk because of the gravity exerted by the Earth. Quite a weak magnet could easily move or pick up the paper clip, effectively overcoming the gravitational field of the whole planet!\n\nIn fact the Electromagnetic force is about 10^36 times stronger than the the gravitational force.\n\nWeaker still is 'The Weak Nuclear Force', which is felt over only a very, very short range and is involved in the action of radioactive decay.\n\nThere's one more force in our universe, and it's even stronger than Electromagnetism - the very imaginatively named 'Strong Nuclear Force'. It's many times stronger than the other forces and again works over an extremely short scale. It's what holds everything together on a subatomic scale, so has to be pretty tough or we'd all fall apart!
944389
I researched this as a geology student 20 years ago and has interested me since then.  By researching cores of basalt, they have a pretty good idea what the magnetic field does when it starts to shift but it is somewhat random and slow.  I remember that typically, before the switch in polarization, the poles starts to migrate in a spiral as it is doing now.  It has been an extra long time since the last switch so it is due.  I suspect that it is about to switch (within the next thousand years or so) but no one can say for certain in my opinion.  Apparently there is a period of time (100 years or so) when the field is next to zero in strength.  I saw a show on it recently that demonstrated they have learned a lot since I studied it in school.
88162
This can get quite complicated, but I do not think you want a complicated answer. \n\nThere is a force that magnets produce on each other. Like poles (two norths or two souths) repel, and opposite poles repel (one north and one south). \n\nThe forces caused by these magnetic force causes a torque to be applied to the suspended magnetic, overcoming the resistance of the string to twisting. This causes the magnetic to turn, and eventually align itself in the minimum energy position, aligned with the external magnetic field at that location, which in most places on the surface of the earth, points towards the north magnetic pole. \n\nThis is not always true, of course, because there are all kinds of complicated fine structure details to the local magnetic fields caused by buried magnetic materials nearby, such as magnetite. \n\nThe north magnetic pole is close to the geographic North pole, but not exactly the north pole, which is why in many places the compass reading has to be corrected by adding or subtracting a figure called the declination. The magnetic pole also migrates every year by a few miles, so the magnetic declination at any given location changes as a function of time as well.
209289
start here:\nhttp://en.wikipedia.org/wiki/Magnet
1187223
Well, a clear question would help. \n\nAre you trying to calculate the power that a certain material can withstand?   Or are you trying to calculate strength?
637751
When sediment containing iron is deposited, the iron aligns itself with the earth's magnetic field like a compass does.  When the sediment hardens, geologists are able to collect the rock, examine the alignment of the iron it contains, and try to calculate the nature of the planet's magnetic field (e.g., its strength, the location of its poles) at the time that sediment was deposited.
4253
yes - assuming there are no nearby magnetic fields that are stronger than the earth's, or no strongly magnetic materials (such as metal) very close to the compass