This video explains the Properties of the Earth that formed a part of EASA ATPL General Navigation learning objectives. The items that will be discussed are Formation of Earth, Shape of the Earth, Poles, Equator, Earth Circumference & Diameter, and Vertex.

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FORMATION OF EARTH
The earth starts to form approximately 4.6 billion years ago, likely as a result of a supernova. The formation process affects the shape of the earth as we know it.

SHAPE OF THE EARTH
Earth is not a perfect sphere, the shape of the earth is known as Ellipsoid or Oblate Spheroid; however, for navigation purposes, it can be considered as a sphere. Semi Major Axis also known as Equatorial radius, is the distance from the earth centre to the equator. Semi Minor Axis also known as polar radius, is the distance from its centre to the North or South Poles. The value of earth compression or ellipticity is 1/298.

POLES
Poles are the points of intersection between the earth axis and the surface of the earth.

EQUATOR
The Equator is a line notionally drawn on the earth equidistant from the poles, dividing the earth into northern and southern hemispheres and constituting the parallel of latitude 0°. It devide the earth into

DIAMETER AND CIRCUMFERENCE OF THE EARTH
Distance from pole to equator is 10,000 km or 5,400NM; circumference of the earth is approximately 40,000 km or 21,600 NM. Diameter of the earth = 12,732.4 km or 6875.5 NM. The calculation method and formula are shown in the video.
VERTEX
The position where the Great Circle reaches its highest latitude is called the vertex. It exists in all Great Circle (GC) except Equator and Meridian or also known as longitude. Properties of Vertex:
• Every GC have two vertices
• Antipodal to each other
• Latitude is Opposite
• Longitude
• It will cut equator at longitude ±90° from Northern/Southern Vertex
• GC direction at Vertex 090° /270°

References:
History of Earth - Wikipedia [ Ссылка ]
Earth formation, Life on earth and in the universe by Khan Academy [ Ссылка ]
Semi-major and semi-minor axes - Wikipedia [ Ссылка ]
Navigation _Vertex of a great circle by Sailortube [ Ссылка ]

AviationExam.com database question number 40526.
Value for the ellipticity of the Earth is 1/297. Earth's semi-major axis, as measured at the equator, equals 6378.4 km.

What is the semi-minor axis (km) of the Earth at the axis of the Poles?

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