What are early magnetic compasses made out of?
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Magnetite or AKA 'lodestone' - an iron containing mineral that is slightly magnetic. The orientation of the iron in the mineral is lined up much like we think of normal man-made magnets. This allows it to be attracted to earth's magnetic field.
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There is now a whole subspecialty of paleomagnetism and archaeology called archaeomagnetism that utilizes the phenomenon you are talking about in the study of archaeological sites. Kilns and hearths have been especially useful in this field, as they were regularly heated to fairly high temperatures, which did allow for realignment of microscopic magnetic particles such as hematite and magnetite with lines of flux in the magnetic field of the earth. By recording the orientations of the particles in old kilns etc, which have been accurately dated by other methods, dating scales of magnetic orientations have been  developed.(last 2 sentences paraphrased from last url on list bleow, which has a nice virtual tour of the application an archaeomagnetism study at an archaeological site.\nI'm directing you to a few informative sites:\nhttp://www.u.arizona.edu/~slengyel/amag2_new-sw_002.htm\nhttp://www.mnsu.edu/emuseum/archaeology/dating/dat_mag.html\nhttp://www.bradford.ac.uk/acad/archsci/depart/resgrp/archmag/menu.php?2\nhttp://www.meteo.be/CPG/aarch.net/onlytxt/no.frame.html\nhttp://farahsouth.cgu.edu/tour/archaeomagnetism/
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http://www.vrml.k12.la.us/mike/Intech2/learning_about_magnets.htm\n\nCHECK IT OUT
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No it hasn't. It's been this way since before Humans walked the earth or at the very least since some bright spark invented the compass. However, we know that the earths magnetic field has changed over time by looking at the direction of magnetism in a cross section of magnetic rock! The direction changes at different points in the cross section and the lower you go, the earlier in time it is.
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If you stood on the North Pole, your compass would point south towards the magnetic pole. \n\nThe magnetic pole is not and never has been connected with the north pole. The north pole is a demarcation of the earths point of rotation in space. The magnetic pole is the actual location of the northern pole of the Earth's magnetic field.
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In the first snow globes the snow was created by use of bone chips or pieces of porcelain, sand or even sawdust. \n\nAs they became more sophisticated, the snow was made out of particles of gold foil or non-soluble soap flakes although nowadays, for health and safety reasons, small pieces of white plastic are used.
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I think you are asking how a positive charge came to be called positive, and a negative charge came to be called negative. To answer this, one has to look at the history of electromagnetism. The history of electical charges is closely connected with the history of magnetism, since they appeared to be similar phenemona.\n\nStatic electricity has been known for a long time. The Greeks had found that rubbing an "elektron" or piece of amber with fur, the elektron would attract pieces of straw and feathers. The Greek mathematician Thales first recorded this observation about 600 BCE. \n\nThe attraction demonstrated by the elektron was often confused with the attraction and repulsion observed using lodestones, which had been known for a while. For example, Pliny in 900 BCE published an account of a Greek shepherd named Magnus who found that a field of black stones (lodestones) attracted metals. These fields were in a region that came to be called Magnesia (It is more likely  \nthat Magnesia is named after the Magnetes tribe that fought in the Trojan War, however). \n\nA Chinese general named  Huang-ti might have been the first to make a compass out of lodestone. Compasses were in common use in the military in China during the Han dynasty (206 B.C.E. to 220 C.E.). A few centuries later, compasses were used on Chinese ships for navigation. \n\nThe first known Western reference to the use of the lodestone as a compass is in the English scholar Alexander Neckham's book "De naturis serum", published about 1190. Apparently by then the lodestone was in common use on European vessels for navigation. \n\nIn 1269, Peter Peregrinus of Maricourt (one of Roger Bacon's teachers) published a treatise known by its shortened title as "Epistola de magnete" in which he clearly describes magnetic polarity. Peter also described the phenomena of like poles repelling, and opposite poles attracting.   \n\nIn 1550, Gerolamo Cardano, an Italian physician, mathematician and inventor outlined the differences between the amber effect (static electricity) and the lodestone effect (magnetism) in his book "De subtilitate rerum". Cardano also described many of the properties of magnets, attributing magnetism to the flow of "fatty humor" to which dry things adhered.  \n\n\nWilliam Gilbert, an English Physician, building on Peter of Maricourt's work, published "De Magnete" in 1600, in which he also clearly distinguished between the lodestone effect (magnetism) and the amber effect (static electricity). Gilbert was probably the first to realize that the earth itself had a magnetic field which was causing the forces on the lodestones. Gilbert dismissed some of Cardano's theories of magnetism. Gilbert explained static electricity as a fluid that is liberated by rubbing. Gilbert explained the dip of the magnetic field observed by English compass maker Robert Norman (1570-1600).\n\nNicolo Cabeo, a Jesuit mathematician, was the first to record the phenomenon of electrical repulsion in his book "Philosophia Magnetica". Cabeo noted that small objects attracted to the amber would sometimes later be repulsed. &#92;\n\n\nOtto van Guericke, a German politician, engineer and scientist experimented with vacuums and magnetism, and produced a variety of machines for producing electric charges, producing his first machine sometimes around the period 1650-1663. In 1672, he noted that he could make a ball of sulfur glow by charging it. He also is the first apparently to note that like charges repel.  \n\n\nIt was found that these charges could be stored in a glass jar lined with silver foil, first by  Ewald Jürgen Georg von Kleist, a German clerk, inventor and Church dean in 1745, and later independently by Pieter van Musschenbroek of the University of Leyden in the Netherlands, in 1746.  This device came to be known as a Leyden jar for this reason (it is interesting that von Kleist had been a studen
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Goring was almost right. Compasses do work there most of the time. The anomolies occur when gas is released from the buried gas hydrates, most often after an undersea landslide (very common off the Mississipi delta). The gas bubbles become electrically charged as they rise through the water and at the point where they emerge there are localised magnetic distubances which cause erratic behaviour in compasses.
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Earth's magnetic field, among other things.
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pole\nmagnetic pole, the two nearly opposite ends of the planet where the earth's magnetic intensity is the greatest, as the north and south magnetic poles. For the magnetic north, it is the direction from any point on the earth's surface linking the horizontal component of the magnetic lines of force with the observer and north magnetic pole; it is similar for magnetic south. The north magnetic pole, first located (1831) by English explorer Sir James C. Ross, is now about 78°N and 104°W in the Queen Elizabeth Islands of northern Canada. The south magnetic pole, reached (1909) by English geologists Sir T. W. E. David and Sir Douglas Mawson, is now about 66°S and 139°E on the Adélie Coast of Antarctica. The magnetic poles are not fixed but follow circular paths with diameters of about 100 miles (160 km). Studies of paleomagnetism also indicate that the earth's magnetic field has reversed its polarity many times in the geologic past. The best hypothesis to date for the origin of terrestrial magnetism is the self-exciting dynamo theory, where the earth's magnetic field is generated by the interaction of motion and electrical currents in the earth's liquid outer core.\n\n///\nMagnetic fields are produced by the motion of electrical charges. For example, the magnetic field of a bar magnet results from the motion of negatively charged electrons in the magnet. 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. \nRocks that are formed from the molten state contain indicators of the magnetic field at the time of their solidification. The study of such "magnetic fossils" indicates that the Earth's magnetic field reverses itself every million years or so (the north and south magnetic poles switch). This is but one detail of the magnetic field that is not well understood\n\n....\nIn order to explain the fact that ferromagnetic materials with spontaneous magnetisation could exist in the demagnetised state Weiss proposed the concept of magnetic domains. Weiss built on earlier work carried out by Ampère, Weber and Ewing suggesting their existence. The findings of this work revealed that within a domain large numbers of atomic moments are aligned  typically 1012-1018, over a much larger volume than was previously suspected. The magnetisation within the domain is saturated and will always lie in the easy direction of magnetisation when there is no externally applied field. The direction of the domain alignment across a large volume of material is more or less random and hence the magnetisation of a specimen can be zero.\n\nMagnetic domains exist in order to reduce the energy of the system. A uniformly magnetised specimen as shown in figure 5(a) has a large magnetostatic energy associated with it. This is the result of the presence of magnetic free poles at the surface of the specimen generating a demagnetising field, Hd. From the convention adopted for the definition of the magnetic moment for a magnetic dipole the magnetisation within the specimen points from the south pole to the north pole, while the direction of the magnetic field points from north to south. Therefore, the demagnetising field is in opposition to the magnetisation of the specimen. The magnitude of Hd is dependent on the geometry and magnetisation of the specimen. In general if the sample has a high length to diameter ratio (and is magnetised in the long axis) then the demagnetising field and the magnetostatic energy will be low.\n\nThe break up of the magnetisation into two domains as illustrated in figure 5(b) reduces the magnetostatic energy by half. In fact if the magnet breaks down into N domains then the magnetostatic energy is reduced by a factor of 1/N, hence figure 5(c) has a quarter
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You need to run LOTS of current through a coiled wire. For a strong one I don't know, but you can make one big enough to deflect a compass like this:\n\nWind some stripped copper wire around a pencil to make a coil. Then connect a D cell battery to the wire. The important thing is that voltage doesn't matter, the stronger the current in the wire, the more powerful the wire.
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Great question.\n\nSo a guy named Oersted found that a single wire looped from one end of a battery to another made a compass move.\n\nSomehow the electrical current was creating a magnetic field!\n\nBy coiling the wire, just like you might coil a rope into a circle, it was like gathering together lots of small magnets to make one big magnet -- all the magnetic fields were adding up in the same direction.\n\nYou can try this yourself with a little compass, some copper bell wire and a regular flashlight battery.\n\nIf you use two flashlight batteries in a row, so as to give 3 volts, you will roughly double the electrical current flowing in the wire and the magnetic field will roughly double in strength.\n\nIf you use two flashlight batteries side by side (parallel) the voltage will remain the same, but the magnet will last longer as you are drawing less "juice" (energy) out of each battery.\n\nHave fun!
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The north and south poles will be at opposite ends of the object and will lie along the axis of the applied magnetic field that was used to produce the ring or marble magnet.\n\nThe poles in the case of the ring can be produced  on a line (axis) perpendicular to the ring (circle), or it can be produced along a line (axis) that passes through the ring material (the circle). Using the iron filings and multiple orientations will assist you in determining the general direction of the axis of the field, but will not tell you precisely where the poles are.
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Because they're made out of magnetic material...iron I believe.
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North and south geographic poles. A compass points towards the North magnetic pole, which is why you must correct for your magnetic declination to find true north using a compass. \n\nSince probably 1000 AD, navigation, however has relied on watching the skies more than watching a compass. Therefore, due north or south  is always the direction to that point in the sky that all the stars circle, projected down to the surface of the earth, and those positions in the sky are projections of the geographic pole (Polaris is actually about 0.8 degrees off the north celestial pole. If north was based on polaris, north would change by as much as 1.6 degrees depending on what time it is!)
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With a Magnetometer. See below for more detail.
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Apparently there is believed to be none now, but there may have been in the past.  Here is a quote from the link below:\n\nObservations of the magnetic fields on Mars by the Mars Global Surveyor spacecraft have revealed that parts of the planet's crust has been magnetized. This magnetization has been compared to alternating bands found on the ocean floors of Earth. One interesting theory, published in 1999 and reexamined in October 2005 in a publication by the same group, is that these bands could be evidence of the past operation of plate tectonics on Mars. However, this has yet to be proven or widely accepted and remains an area of active research.