Tropic of Cancer (0.468″) of latitude, or 15 metres, per year (it was at exactly 23° 27′N in 1917 and will be at 23° 26'N in 2045). See axial tilt and circles of latitude for further information. North of the tropic are the subtropics and the North Temperate Zone. The equivalent line of latitude south of the Equator is called the Tropic of Capricorn, and the region between the two, centered on the Equator, is the tropics. There are approximately 13 hours, 35 minutes of daylight during the summer solstice. During the winter solstice, there are 10 hours, 41 minutes of daylight. Starting
Degrees of freedom (physics and chemistry) for 3 degrees of freedom. In addition, the molecule has two rotational degrees of motion and one vibrational mode. The rotations occur around the two axes perpendicular to the line between the two atoms. The rotation around the atom–atom bond is not a physical rotation. This yields, for a diatomic molecule, a decomposition of: For a general, non-linear molecule, all 3 rotational degrees of freedom are considered, resulting in the decomposition: which means that an -atom molecule has vibrational degrees of freedom for . In special cases, such as adsorbed large molecules, the rotational degrees of freedom can be limited