The changes on Earth throughout the year result in the lengthening or shortening of days from north to south as the planet orbits the Sun. The Northern Hemisphere experiences the longest day of the year during the summer solstice, which occurs at 22:57 on June 21st according to Hanoi time.
The summer solstice is the moment when the Northern Hemisphere tilts the most towards the Sun, receiving the maximum amount of sunlight during the day. This means it is the longest day for half of the Earth in the northern hemisphere, where summer reaches its peak. However, while the Northern Hemisphere is bathed in sunlight, the Southern Hemisphere experiences the shortest day during winter. After the summer solstice, the days in the Southern Hemisphere start to lengthen while those in the Northern Hemisphere begin to shorten.
In reality, the Sun does not actually move horizontally across the sky. The apparent motion of the Sun in the sky is the result of the Earth’s rotation on its tilted axis. The arc of the Sun’s movement changes every day, becoming larger in the Northern Hemisphere from the winter solstice in December to the summer solstice in June, and vice versa.
The European weather satellite, Meteosat, observes Earth from a geostationary orbit at an altitude of 36,000 km. Currently, the Earth is gradually approaching the autumnal equinox in September, marking the moment when both hemispheres receive an equal amount of sunlight.