Geocentric Coordinate Time system. When the Earth is at perihelion in January, TCG ticks even more slowly than it does on average, due to gravitational time dilation from being deeper in the Sun's gravity well and also velocity time dilation from moving faster relative to the Sun. At aphelion in July the opposite holds, with TCG ticking faster than it does on average. Geocentric Coordinate Time Geocentric Coordinate Time (TCG - Temps-coordonnée géocentrique) is a coordinate time standard intended to be used as the independent variable of time for all calculations pertaining to precession, nutation, the Moon, and artificial satellites of the Earth.
Central place theory Central place theory Central place theory is a geographical theory that seeks to explain the number, size and location of human settlements in a residential system. The theory was created by the German geographer Walter Christaller, who asserted that settlements simply functioned as 'central places' providing services to surrounding areas. To develop the theory, Christaller made the following simplifying assumptions: All areas have: Therefore, the trade areas of these central places who provide a particular good or service must all be of equal size The theory then relied on two concepts: "threshold" and "range". The result of these consumer preferences