magnetic pole reversal? why don't we feel it?
112224
because it changes slowly, and also you don't feel the magnets on your frigde why would you feel the earth? :P
380739
The presence of an electric field is tested by placing a unit charge at a point. \n\nIf the charge experiences a force, we say that there exists an electric field.\n\nThe field is measured by the force experienced by the unit charge.\n\nSimilarly, a magnetic field is tested by a wire circuit of very small area.\n\nBut the difference is that, here, we measure the rotational effect of this test circuit and not mere force.\n\nThe test circuit has its highest moment in a particular orientation of the area.\n\nThe side (upper side and lower side) of the test circuit also affects the direction of moment. \n\nIf the test circuit placed in a point and if it experience different moment for different orientation, we infer that there is a magnetic field.\n\nThe field is measured by the highest moment experienced by the test circuit.\n\nEarlier we used the concept of free unit north pole; since no single pole exists now the measurement is base on free test circuit, which is more and real fundamental concept.
685382
The pole shifts are not regular, and they don't always flop a full 180. The poles drift because they are generated by a ferro-magnectic liquid that is spinning in part of our core. It doesn't spin at the same speed as the crust above it.\n(Humans are about 7-10 million years old, but it of course depends on your definition of what a human is. Upright homonid? cro-magnon? neanderthal?. The dinosaurs died out 65 million years ago. 100-200 million years ago they were in their heyday.)
682124
As with many things in nature there is only one real answer to this question : No one really knows! What we do know now, is \n1. The magnetic poles change and last time this happened \nwas sometime around 780,000 years ago.\n2. The reversal will take thousands of years.
445743
IF YOU DON'T UNDERSTAND MY ANSWER.....FOLLOW THIS LINK ;\n\nhttp://en.wikipedia.org/wiki/Dipole\n\nA dipole (Greek: di(s) = double and polos = pivot) is a pair of electric charges or magnetic poles of equal magnitude but opposite polarity (opposite electronic charges), separated by some, usually small, distance. Dipoles can be characterized by their DIPOLE MOMENT : A VECTOR QUANTITY WITH A MAGNITUDE EQUAL TO THE PRODUCT OF THE CHARGE OR MAGNETIC STRENGTH OF ONE OF THE POLES AND THE DISTANCE SEPARATING THE TWO POLES. The direction of the dipole moment corresponds, for electric dipoles, to the direction from the negative to the positive charge. For magnetic dipoles, the dipole moment points from the magnetic south to the magnetic north pole — confusingly, the "north" and "south" convention for magnetic dipoles is the opposite of that used to describe the Earth's geographic and magnetic poles, so that the Earth's geomagnetic north pole is the south pole of its dipole moment. Because of the absence of magnetic monopoles, magnetic dipoles are actually created by current loops or by quantum-mechanical spin.\n\nSince the direction of an electric field is defined as the direction of the force on a positive charge, electric field lines point away from a positive charge and toward a negative charge.\n\nWhen placed in an electric or magnetic field, equal but opposite forces arise on each side of the dipole creating a torque τ:\n\nτ = p x E  (for an electric dipole moment p) (measured in coulomb-meters)\n\nor\n\nτ = m x B = u0m x H  (for a magnetic dipole moment m) (measured in ampere-square meters).\n\nThe resulting torque will tend to align the dipole with the applied field.
127673
Yes, if the magnetic field disappeared, there would be more radiation reaching the earth and this would cause adaptations to occur.  There's been some research into what has happened to plants and animals around the Chernobyl nuclear power plant in Russia that melted down and is still leaking radiation.\n\nNow, given that magnetic fields diminish and become spotty during magnetic pole reversal, some adaptation may occur but I'm not sure it will cause wholesale adaptation events.  These reversal events have occured about once every 5,000 to 50,000,000 years and larg land animals have survived for hundreds of millions of years so, yes, I think that they might be able to adapt quickly enough during some periods of low to no magnetic field.\n\nAlso, I think that ocean life will go relatively unaffected because water will help absorb some of this radiation.\n\nHowever, I'm sure some biologist or someone with greater knowledge than myself in this area will come along and prove me wrong. :^)\n\n-- \n\nAfter posting this, I read an article in March 2006 Scientific American on the problems of cosmic rays with respect to interplanetary space travel.  They noted in the article that it is a misconception that the magnetic field is the most significant form of protection from cosmic rays -- that it is the atmosphere itself that provides the greatest source of protection from cosmic rays.\n\nhttp://www.sciam.com/article.cfm?chanID=sa006&colID=1&articleID=000D6A37-E75F-13F5-A75F83414B7FFE9F
511616
First: Gravity is due to mass, while magnetism is due to the movement of an electric charge.  For earth, this is believed to be caused by the movement of ions within the earth, the magma near the core.\n\nSecond: The poles of a magnet were misnamed.  They named the poles of a magnet because of the direction they pointed.  However, once the properties of magnetism were truly understood, it was too late.  So, appropriately, it could be said that near the north pole is the south magnetic pole, but I'm sure most teachers would frown upon that assertion.\n\nOther notes about magnetism on earth: The earth is imperfect.  The magnetic field is not uniform, so there are variations.  Magnetic north is not geographic north in all situations.  The earth is tilted, and we don't really know the flow of the magma that causes the magnetic field all that well.  Not to mention, there is speculation that magnetic north and south may flip at some point in time, but the mechanism of this is lost on me.  It has happened a very long time ago, and is expected to happen again sometime in the future.
1161988
No.\n\nBut it can when it is heated.\n\nIf you heat a magnetic material above its Curie temperature, it depolarises and stops being magnetic.
85373
Magnetic force........
1020724
Based 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 spontaneously migrate from one orientation to the other over the course of a few hundred to a few thousand years. Other scientists propose that the geodynamo first turns itself off, either spontaneously or through some external action like a comet impact, and then restarts itself with the magnetic "North" pole pointing either North or South. External events are not likely to be routine causes of magnetic field reversals due to the lack of a correlation between the age of impact craters and the timing of reversals. Regardless of the cause, when magnetic "North" reappears in the opposite direction this is a reversal, whereas turning off and returning in the same direction is called a geomagnetic excursion.\n\nUsing a magnetic detector (a variant of a compass), scientists have measured the historical direction of the Earth's magnetic field, by studying the layered iron-rich lava rocks. This is possible as each layer has been found to maintain the original magnetic field at its time of cooling. They have found that the poles have shifted a number of times throughout the past.\n\nThe above is a quote from Wikpaedia and magnetic pole reversal is well documented in scientific literature. It still begs the question raised by one of the correspondents above as to why then there were not great extinctions as the magnetosphere would be disrupted and lethal cosmic radiation would harm all surface dwelling life.
270208
Intensity of current and magnetic permeability of the core.
757349
HI.  Great questions.  just realised i only got 2 points for answering.  anyway.  Weird magnets aren't they.  they always have a north and a south pole.  Almost like a mini Earth!  at the centre of the earth matter is so supper heated that it almost, but not quite, turns into energy. This raw force changes into a mix of matter and energy, producing and expelling a strong field of power.   When volcanoes were very active in earths early years, quite frequently this strange mix spewed into our atmoshere and solidified quickly.  magnetism was trapped during this process and magnets were born.  strange but very true.  I L U J L.
1048978
Doubtul.  The earth's magnetic field simply isn't that strong.  If it were, it would overwhelm any electronic devices on earth due to induced current.  While overall it's strong enough to protect us from harm from the solar wind and other nasty charged particles in space, it's not strong enough to harness locally for any useful work.
777145
There was a recent Nova program that said a magnetic reversal had been captured in a lava flow, so that it had reversed while the lava was cooling.\n\nOn the other hand, they also indicate that the reversals take place as localized anomalies, so that only the area of the volcano may have reversed.\n\nMore info at\n\nhttp://www.pbs.org/wgbh/nova/magnetic/reversals.html
662574
It might be due to the number of unpaired electrons which causes a large amount of net magnetic moment making the material more magnetic.  This is the property of a ferro magnetic material.
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.
480443
I have not read the article but this sound it weird enought I thought I mention it.\n\n\nBurkhard Heim claimed it is possible to convert electromagnetic energy into gravitational and back again, and speculated that a rotating magnetic field could reduce the influence of gravity on a spacecraft enough for it to take off.