On 21st June, which marks the summer solstice in the Northern Hemisphere, the tilt of the Earth's axis causes the Sun to remain above the horizon for 24 hours at the Arctic Circle and regions further north. This phenomenon, known as the "midnight sun," occurs because the pole is tilted towards the Sun, resulting in continuous daylight in those areas. This is a key example of how the Earth's axial tilt and revolution around the Sun influence seasonal variations and daylight hours, a concept fundamental to understanding Earth's climatic and environmental systems in UPSC GS Paper I.