The need to accurately determine the location on the earth’s surface of one's own and surrounding objects has become especially urgent for a person with the beginning of an active study of the planet.
Geographic coordinates - latitude and longitude - are determined by the intersection point of two imaginary lines - parallel and meridian. The longest parallel, from which the latitude begins, is the equator.
origin of name
The imaginary line that the points located at the same distance from both poles form on the surface of the globe divides the planet into two hemispheres, two hemispheres. The word for the name of such a border has ancient roots. The Latin "aequator", an equalizer, is formed from the verb "aequō" - to equalize. In the international practice, the "equator" came from the German language, from Äquator.
This word has a more general meaning. In geometry, a three-dimensional body having simultaneously mutually perpendicular axis and a plane of symmetry has its own equator, its longest parallel is the intersection of the surface of a given body with a plane of symmetry. In astronomy, the celestial equator, the magnetic equator of a planet or star are known.
Earth is a geoid
The belief that the Earth is in the form of a flat disk was questioned only by ancient Greek scholars. By the end of the 19th century, it became clear that the shape of our planet is not just an ideal ball, but a special body of revolution - a geoid, the surface of which is influenced by many factors - from the force of gravity to the “cosmic wind”. Two points of the geoid are determined by the axis of its rotation - this is the North and South Pole. At the same distance from them is the longest parallel on Earth, the earth's "waist" is the equator.
But the geoid is not accurate, but only approximately describes the shape of the planet. Such it would be in the absence of mountains and depressions, if only a calm, undisturbed surface of the world's oceans were available. This level plays an important role in navigation and geodesy - from it a report of vertical marks for various technical and engineering objects is kept.
Equator length
It is also possible to understand which parallel is the longest by specific values of the geoid’s geometric dimensions. The radius of the equator, as a circle "drawn" on the surface of the Earth, is equal to the radius of the planet. Accurate measurements show that this parameter differs at different points on the planet - the polar radius is 21.3 km less than the equatorial. The average value is 6371 km
Using the formula for the circumference - 2πR - you can calculate the length of the equator. Different geophysical standards define numbers with a difference of about 3 m, an average of 40,075 km. The circumference along the meridian is 40,007 km, which proves the special geometric qualities of the geoid.
Zero latitude
The coordinate grid that the globe is covered with - a visual model of the globe - is formed by 360 meridians connecting the two poles, and 180 lines parallel to the equator, distributed 90 pieces to the poles, on either side of it. The meridian, taken through the Greenwich Observatory, located in the southeast of the English capital, is considered to be the longitude starting point from 1884. The longest parallel dividing the globe into the Northern and Southern Hemispheres is the origin of the latitude.
Coordinates are angular values, measured in degrees. Longitude is the angle between the plane passing through the zero - Greenwich - meridian and that indicated by the line connecting the earth's poles and drawn through this point. East of Greenwich to 180 °, longitude is called east and is considered positive, to the west - it has negative values and is called west.
Points equidistant from the poles form the equatorial plane. The radius drawn from the center of the globe through a given point on its surface forms an angle with this plane, the magnitude of which is latitude. The longest parallel has zero latitude. To the north of the equator, this angle is considered positive - from 0 ° to 90 °, to the south - negative.
Signs and rituals
The equator is just an illusory border between the two hemispheres, but it has always excited the human imagination. It is customary for sailors from different countries to observe special rituals when crossing the zero latitude, especially with respect to those who do this for the first time. Where the equator passes inhabited places, special signs and constructions are invariably erected, making the conditional line real. A rare tourist will miss the opportunity to stand with one foot in the South and the other in the Northern Hemisphere. It is impossible to forget after that, as the longest parallel of the globe is called.
But the equatorial zones of the Earth also have other unique characteristics that give them special value. The gravitational attraction here is slightly less than at other latitudes, and the momentum of rotation of the globe is greater. This allows you to significantly save rocket fuel to put spacecraft into orbit. It is no coincidence that it is in the equatorial French Guiana, on the South American coast, that the most effective launch space complex is located - the Kourou Cosmodrome.