A solstice marks the point in the Earth's orbit when the sun reaches its maximum or minimum declination relative to the celestial equator. These astronomical events, specifically the Summer and Winter Solstices, represent the moments when the difference in daylight hours reaches its greatest variation for any given hemisphere. Because of the planet's axial tilt relative to the plane of its orbit, the amount of solar insolation received differs dramatically between these dates. The occurrence of the solstices is a fundamental indicator used in the study of Earth's orbital mechanics and the resultant seasonal changes in global climate patterns.