A peak of eternal light (PEL) is a hypothetical point on the surface of an astronomical body that is always in sunlight. Such a peak must have high latitude, high elevation, and be on a body with very small axial tilt. The existence of such peaks was first postulated by Beer and Mädler in 1837. The pair said about the lunar polar mountains: "...many of these peaks have eternal sunshine". These polar peaks were later mentioned by Camille Flammarion in 1879, who speculated that there may exist pics de lumière éternelle at the poles of the Moon. PELs would be advantageous for space exploration and colonization due to the ability of an electrical device located there to receive solar power regardless of the time of day or day of the year, and the relatively stable temperature range.

The Moon is Earth's only natural satellite. It orbits at an average distance of 384,400 km (238,900 mi), about 30 times the diameter of Earth. Over time Earth's gravity has caused tidal locking, causing the same side of the Moon to always face Earth. Because of this, the lunar day and the lunar month are the same length, at 29.5 Earth days. The Moon's gravitational pull – and to a lesser extent, the Sun's – are the main drivers of Earth's tides.