Mean longitude is simply the mean longitude at a reference time "t", known as the epoch. Mean longitude can then be expressed, where "n" is the "mean angular motion" and "t" is any arbitrary time. In some sets of orbital elements, "ε" is one of the six elements. Mean longitude Mean longitude is the ecliptic longitude at which an orbiting body could be found if its orbit were circular and free of perturbations. While nominally a simple longitude, in practice the mean longitude does not correspond to any one physical angle. From these definitions, the "mean longitude", "l", is the angular distance
Thermal equator both "summer" and "winter." Chennai, India, at 13 degrees north is considered to lie on the thermal equator at its longitude (80 degrees east). Thermal equator The thermal equator (also known as "the heat equator") is a belt encircling the Earth, defined by the set of locations having the highest mean annual temperature at each longitude around the globe. Because local temperatures are sensitive to the geography of a region, mountain ranges and ocean currents ensure that smooth temperature gradients (such as might be found if the Earth were uniform in composition and devoid of surface irregularities) are impossible, the