# Tag Info

125

Earth has a magnetic field. You can verify this yourself; it is why a compass works. Just take any magnet and hang it carefully from a string. As long as there's nothing else magnetic around and it's well-balanced and free to rotate, it will line up with Earth's magnetic field. We have measured the Earth's magnetic field all over the surface and up into ...

60

The crucial part is that earth's outer core is fluid, and that it's conductive. That the material happens to be iron which we know as ferromagnetic is actually rather unimportant, because the geomagnetic field is not created as a superposition of atomic spins like in a permanent magnet. Rather, it's generated via Ampère's law from macroscopic currents,...

26

The core of the Earth isn't a giant bar magnet in the sense that the underlying principles are different. A bar magnet gets its magnetic field from ferromagnetism while Earth's magnetic field is due to the presence of electric currents in the core. Since the temperature of the core is so hot, the metal atoms are unable to hold on to their electrons and ...

25

Setting aside the technical details, the biggest problem with this idea would be Earnshaw's theorem, stating that it is impossible to stably levitate a magnetic dipole in another magnetic dipole's (Earth's) field. In other words, you could theoretically generate enough magnetic force for lift-off with your dipole (the coil), but you would have trouble ...

21

A geodynamo requires a fluid that can carry a current. A widely held but incorrect explanation for Mars' lack of a magnetic field is that Mars' core is frozen solid. Gravitational observations of Mars show that its core is at least partially molten, just as is ours. While a frozen core would explain Mars' lack of a magnetic field, this explanation does not ...

20

Not really. A magnetic field alone doesn't create electricity. A changing magnetic field does. The Earth's magnetic field does change a tiny bit but not enough to really generate much. The other option is to move the inductor in the magnetic field. The Earth's magnetic field is quite homogeneous over short distances though so the coil would need to move ...

17

There are two parts to this question (even when you cut out the bonus bits). How much energy is stored in the earth's magnetic field (ramp up the magnet) How much power to keep that field going (drive current through big loop) The former is given by the $\frac12 L I^2$ - so we need to estimate the inductance of the coil needed and its current. A single ...

17

You are in luck, since Osamu Motojima and Nagato Yanagi have already calculated it for you in their report Feasibility of Artificial Geomagnetic Field Generation by a Superconducting Ring Network. They conclude that producing 10% of the current field is feasible using "12 latitudinal high-temperature superconducting rings, each carrying 6.4 MA ...

12

The magnets that you learned about in junior high are fundamentally different from the ionic liquid that generates the Earth's magnetic field. Conventional magnets get their magnetism from having a large number of magnetic "domains" aligned in the same direction within the (solid) material. These domains are essentially large regions where the crystal ...

10

The aurora are emissions of light caused by the excitation of nitrogen and oxygen mostly by energetic (i.e., ~1 keV to few 10s of keV) electrons coming from the Earth's geomagnetic tail (i.e., anti-sunward direction). There are proton-driven aurora too, but they are fainter and more rarely observed (partly because it takes much stronger geomagnetic storms ...

9

The field direction is stored in the magnetization direction of ferromagnetic minerals in the bedrock when it cools down. Those minerals are typically iron oxides like magnetite Fe$_3$O$_4$ etc or iron sulphides like pyrrhotite Fe$_7$S$_8$, with admixtures of other elements. Such minerals are often not really hard ferromagnets, but their coercive field is ...

9

It's tilted with the N pole toward the sun at Summer Solstice, and S pole toward the sun at Winter Solstice (assuming you are in the northern hemisphere, and winter is in December).

8

Yes, the Earth's magnetic field does rotate with the Earth. There is a simple way and a complicated way to explain this. Firstly the simple way: the magnetic north pole and the North Pole are not at the same point. That means if the magnetic field did not rotate with the Earth the magnetic north pole would rotate once around the North pole every 24 hours. ...

8

Well, it does. The Earth's magnetic field is about half a gauss, or $0.5\times10^{-4}\rm\,T$. So if you have a meter of wire carrying one ampere of current from east to west, it'll feel a magnetic force of $0.5\times10^{-4}\rm\,N$ in some mixture of upwards and the north-south direction that depends on the tilt of Earth's field at your location. (I'm in ...

7

The Earth's magnetic field does not arise due to the same effect as the magnetic field of a permanent magnet. A permanent magnet's magnetic field is basically arose because at some point in that magnet's past it's internal magnetic dipoles (from its constituent atoms) were all aligned (it was magnetized) and then the alignment of its internal magnetic ...

6

The tilt is always 23.5 degrees, and it always points in the same direction (roughly to the Polaris star), but that means that it does not always point towards the sun or away from it. That depends on the time of year. Let's say that in your drawing Polaris is "above" the earth orbit, and "left" from the center. Then the earth axis is ...

5

Yes, Earth does have a magnetic field(check it out with a compass!). In geology, they explain this in this way: The Earth's core is divided between the inner and outer cores. The inner core is solid because of the very high pressure. The outer core, although it also has high pressure, it is not as high as the inner core and thus it is not solid, but fluid. ...

5

The Earth's magnetic field is caused by eddy currents in the liquid parts of the planet's interior. We believe the field is not due to a permanent magnet because: (1) Its direction and strength change over time, and (2) the planet's interior is hotter than the Curie temperature of its elements, and so a permanent magnet would not retain its magnetism. ...

5

Yes, the geomagnetic field does rotate with the earth. This is the reason why maps of the geomagnetic field overlaying geographic coordinates are reasonably accurate for a decade or two - and why a compass is still useful for navigation. (i.e. You do not need to know the time of day in order to correct for the magnetic declination cited on your map!) The ...

5

The physical explanation for the origin of the geomagnetic field is that it is caused primarily by electric currents (moving charge) in the Earth's liquid outer core. The composition of the outer core is thought to be largely iron. The temperature in the core is above the Curie temperature of iron, which means the magnetic field of the core is not caused by ...

5

The north-seeking pole always points toward magnetic north, assuming it is only feeling Earth's magnetic field. A magnet has no idea (so to speak) which direction is geographic north. Any source that tells you that a magnet points geographically north is only as correct as the statement that geographic north and magnetic north are the same direction.

5

Because the Earth is an electro-magnet, not a permanent magnet. There are two types of magnets: permanent magnets and electro-magnets. Permanent magnets do tend to lose their magnetic qualities when they melt. electromagnets do not. The Earth's magnetic field is (In Theory) formed by electric current flowing through various layers of its core. Part of ...

4

You can't generate power from a static magnetic field alone. In this context, the earth is just a permanent magnet, and a rather weak one at that. To generate electric power from that, you have to move electric conductors, like wires, thru the field in the right direction and with the right orientation of the conductor. If any electric power is taken from ...

4

If some fluctuation in the currents in Earth's core was to originate a second magnetic axis, the magnetic moments relative to the two fields (the "normal one" and the "anomalous one") would start to exert forces on each other until they merged in a single field, according to the equation for the torque acting on a magnetic dipole in an external field: \...

3

This particular orientation sensing protocol is not wonted to me, but the following, given the data you cite, will indeed give you your orientation in space: Magnetometer gives $\vec{N}_0$ north direction (in general, not parallel to the "ground" because it has magnetic dip included); Gravity accelerometer gives $\vec{D}$ "down" direction; Then \$\vec{D}\...

3

Magnetic surveys are used for prospecting for oil or minerals. On top of the earth's magnetic field there are small contributions form magnetic materials in the surface rocks, especially granites. You can use this to either find large bodies of volcanic rock that migth have minerals or diamonds - or alternatively you can find large volumes with no magnetic ...

3

No. The earth's North Pole is a "magnetic south pole". With a compass, the part of the needle that points north is a magnetic north pole. With magnets, opposite poles attract, so what we call North on the earth must be magnetic south to attract the needle's north.

3

Earth's magnetic field is just too weak. half a gauss is nothing compared to your standard refridgerator magnet.

3

Actually, the Earth's magnetic field does affect electronics, probably, in a positive way, as it protects it from the effects of cosmic rays.

Only top voted, non community-wiki answers of a minimum length are eligible