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The 180th meridian or antimeridian [1] is the meridian 180° both east and west of the prime meridian in a geographical coordinate system. The longitude at this line can be given as either east or west. On Earth, the prime and 180th meridians form a great circle that divides the planet into the Western and Eastern Hemispheres.
The bearing angle value will always be less than 90 degrees. [1] For example, if Point B is located exactly southeast of Point A, the bearing from Point A to Point B is "S 45° E". [3] For example, if the bearing between Point A and Point B is S 45° E, the azimuth between Point A and Point B is 135°. [1] [3] Azimuths and bearings.
Earth's rotation imaged by Deep Space Climate Observatory, showing tilt. Earth's rotation or Earth's spin is the rotation of planet Earth around its own axis, as well as changes in the orientation of the rotation axis in space. Earth rotates eastward, in prograde motion. As viewed from the northern polar star Polaris, Earth turns counterclockwise.
1571 Africa map by Abraham Ortelius, with Cape Verde as its prime meridian. 1682 map of East Asia by Giacomo Cantelli, with Cape Verde as its prime meridian; Japan is thus located around 180° E. In 1541, Mercator produced his famous 41 cm terrestrial globe and drew his prime meridian precisely through Fuerteventura (14°1'W) in the Canaries.
The position of a point along the meridian at a given longitude is given by its latitude, measured in angular degrees north or south of the Equator. On a Mercator projection or on a Gall-Peters projection, each meridian is perpendicular to all circles of latitude. Assuming a spherical Earth, a meridian is a great semicircle on Earth's
Astronomers have chosen this unit to measure right ascension because they measure a star's location by timing its passage through the highest point in the sky as the Earth rotates. The line which passes through the highest point in the sky, called the meridian , is the projection of a longitude line onto the celestial sphere.
Denoted with the symbol Ω, it is the angle from a specified reference direction, called the origin of longitude, to the direction of the ascending node (☊), as measured in a specified reference plane. [1] The ascending node is the point where the orbit of the object passes through the plane of reference, as seen in the adjacent image.
The poles of the dipole are located close to Earth's geographic poles. At the equator of the magnetic field, the magnetic-field strength at the surface is 3.05 × 10 −5 T, with a magnetic dipole moment of 7.79 × 10 22 Am 2 at epoch 2000, decreasing nearly 6% per century (although it still remains stronger than its long time average). [145]