Compass is a device, the invention of which allowed a person to learn to find the location of the planet's poles, thus focusing on the terrain. The blue end of its arrow shows where the north is located, and the red one fixes the south direction.
However, when determining the cardinal points by this method, in some cases you can make a mistake. After all, the geographic north and south of the planet do not quite coincide with the magnetic ones, and it is the location of the latter that is indicated by the compass needle. To be precise in this matter, scientists have introduced a number of concepts, which include magnetic declination and magnetic inclination. They help to detect measurement error, as well as to find out the distance from the poles. In addition, these determinants make it possible to capture changes in the field itself that occur over time.
What is the earth's magnetic field?
Our planet can be imagined as a giant magnet. The compass needle is also something like that, only in a miniature version. That's why the endsher all the time point to the magnetic poles of the Earth, assuming a position along its magnetic lines.
But what is the source and nature of such a grandiose phenomenon on a planetary scale? People began to be interested in this several centuries ago. At first, versions were put forward that the cause of magnetism is hidden in the earth's core. So they thought until they found clear evidence of the influence of solar activity on this natural phenomenon. And then scientists suggested that the source of terrestrial magnetism is not at all in the core.
One of the latest scientific hypotheses, trying to unravel the mystery of what the Earth's magnetic field is, broadcasts the following. Water from the oceans, which occupy a vast territory of the blue planet, evaporates in large quantities under the influence of the energy of the Sun and becomes electrified, receiving a positive charge. In this case, the earth's surface itself is negatively charged. All this provokes the movement of ion flows. This is where the magnetic properties of the planet itself come from.
Geographic and magnetic axes
What is the geographic axis of the Earth is not difficult to understand. A planetary ball rotates around it, where certain points remain motionless. In order to figure out where the axis is, you need to connect the poles with an imaginary line. But there are similar points in the Earth-magnet or, to put it scientifically, in the geomagnetic sphere. If you draw a straight line connecting the north magnetic pole and the south, it will be the magnetic axis of the planet.
Similarly, the Earth-magnet has an equator. This is a circle located in a plane that is perpendicular to a straight line called the axis. The magnetic meridians are defined in a similar way to the one just described. These are arcs that envelop the geomagnetic sphere vertically.
Magnetic declination
It is clear that the magnetic and geographic meridians, as well as the axes, cannot coincide completely, but only approximately. The angle between them at a certain point on the earth's surface is commonly referred to as the magnetic declination. It should be noted that for each specific locality, this indicator, when clarified, will not be the same. And its value helps to determine the error between the true direction and the compass readings.
Since the direction of the magnetic poles does not coincide with the geographic ones, this error, it turns out, must be taken into account in navigational calculations. Such a difference can be very important for sailors, pilots and the military. On many maps, for convenience, the magnitude of the magnetic declination is indicated in advance.
Magnetic inclination
It is interesting that from the point of view of physics, the true and magnetic poles not only do not coincide, but also turn upside down, that is, the south corresponds to the magnetic north, and vice versa.
The compass needle is designed to determine the location of the magnetic poles anywhere on Earth. And what will happen to the readings of this instrument directly at the North and South Poles? If athe compass is arranged in a classical way, then the arrow will no longer move freely on the central needle along the body, but will press against it or, on the contrary, deviate. At the north geographic pole, it will describe a pirouette 90 ° down, while at the south it will shoot up vertically with its northern end. The opposite tip of the arrow, that is, the southern one, will behave exactly the opposite.
The indicated metamorphoses do not occur abruptly at one moment when moving towards the poles. It should be noted that at a certain angle in the vertical direction, the compass needle deviates almost constantly under the influence of a magnetic field: in the northern hemisphere - down, and in the southern, respectively, up with its northern end. This angle is called magnetic inclination.
Such a phenomenon has been known for a long time and was discovered by the Chinese back in the 11th century. But in Europe it was described much later, in the 16th century. And the astronomer and engineer from Germany Georg Hartmann did it.
Measurement methods
The fact that the magnetic inclination changes in a certain way depending on the geographic location and the coordinates describing it was proved by Christopher Columbus. As you approach the equator, the angle decreases. It becomes zero at the equatorial line itself. However, at the time of this great traveler, they had not yet learned how to accurately determine the value of this quantity. The first devices, called inclinators and allowing you to set the angle of inclination of the Earth's magnetic field, were invented only more than half a century after his death. Columbus.
The first such design was proposed by the Englishman Robert Norman in 1576. But she was not entirely accurate in her testimony. Later, more advanced and sensitive inclinators were invented.
