Compass is a device, the invention of which allowed a person to learn to find the location of the poles of the planet, thus focusing on the terrain. The blue end of its arrow indicates where the north is located, and the red fixes the southern direction.
However, in determining the cardinal points by this method in some cases, one can be mistaken. After all, the geographical north and south of the planet do not quite coincide with the magnetic, and it is the location of the latter that indicates the compass needle. To be precise in this matter, scientists have introduced a number of concepts, which include magnetic declination and magnetic declination. They help to detect the measurement error, as well as to determine the distance from the poles. In addition, these determinants make it possible to record changes in the field itself that occur over time.
What is the magnetic field of the earth?
Our planet can be imagined of grandiose sizes with a magnet. The compass needle is also something like that, only in a miniature version. That is why its ends all the time point to the Earth’s magnetic poles, taking 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. Initially, it was suggested that the cause of magnetism is hidden in the earth's core. They thought so until they found vivid confirmation of the influence of solar activity on this natural phenomenon. And then scientists suggested that the source of terrestrial magnetism is not at all at the core.
One of the latest scientific hypotheses, trying to solve the mystery of the Earth’s magnetic field, 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 is electrified, receiving a positive charge. In this case, the earth’s surface itself is negatively charged. All this provokes the movement of ion flows. From here the magnetic properties of the planet itself appear.
Geographic and magnetic axis
What is the geographical axis of the Earth, it is not at all difficult to understand. Around it, a planetary ball rotates, where certain points remain motionless. In order to understand where the axis is, you need to connect the poles with an imaginary line. But similar points exist for the Earth-magnet or, to put it scientifically, 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 an axis. Like just stated, magnetic meridians are determined. These are arcs enveloping the geomagnetic sphere vertically.
Magnetic declination
It is clear that the magnetic and geographical meridians, like the axes, cannot coincide completely, but only approximately. The angle between them at a certain point on the earth's surface is called magnetic declination. It should be noted that for each particular area, this indicator will turn out to be uneven when clarified. And its value helps to determine the error between the true direction and the compass.
Since the direction of the magnetic poles does not coincide with the geographical, this error, it turns out, must be taken into account when navigating. 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 magnetic poles at any point on the Earth. And what will happen to the readings of this device directly at the North and South poles? If the 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, she will describe a pirouette 90 ° down, at the south - she will rise vertically upward with her northern end. The opposite tip of the arrow, that is, the south, will behave exactly the opposite.
These 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, upward with its northern end. This angle is called magnetic inclination.
A similar 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 he did this astronomer and engineer from Germany Georg Hartman.
Measurement methods
The fact that the magnetic inclination varies in a certain way depending on the geographical location and the coordinates describing it was proved by Christopher Columbus. When approaching the equator, the angle decreases. It becomes equal to zero on the equatorial line itself. However, at the time of this great traveler, they had not yet learned to accurately determine the value of this quantity. The first instruments, 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 the death of Columbus.
The first such design was proposed by the Englishman Robert Norman in 1576. But she was not entirely accurate in the testimony. More sophisticated and sensitive inclinators were invented later.