The enormous effect of the Sun on Earth has been recognized since prehistoric times, and the Sun has been regarded by some cultures as a deity. The synodic rotation of Earth and its orbit around the Sun are the basis of the solar calendar, which is the predominant calendar in use today.
Latent heat is (thermal) energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process - usually a first-order phase transition.
Latent heat can be understood as heat energy in hidden form which is supplied or extracted to change the state of a substance without changing its temperature. Examples are latent heat of fusion and latent heat of vaporization involved in phase changes, i.e. a substance condensing or vaporizing at a specified temperature and pressure.
The term was introduced around 1762 by British chemist Joseph Black. It is derived from the Latin latere (to lie hidden). Black used the term in the context of calorimetry where a heat transfer caused a volume change while the thermodynamic system's temperature was constant.
In contrast to latent heat, sensible heat involves an energy transfer that results in a temperature change of the system.