Summer Solstice will be observed on 21, June 2019 and it will be the day with the longest period of daylight. Many of us already know the scientific reason but those who don’t know, here is the complete explanation why June 21 is known as Summer Solstice, often known as the longest day of the year.
On June 21st, the Northern Hemisphere is tilted towards the sun. The rays of the sun fall directly on the Tropic of Cancer.
As a consequence, those areas receive extra heat. The areas near the poles get less heat (as the rays of the sun are slanting). The North Pole is inclined towards the sun & the places beyond the Arctic Circle experience continuous daylight for almost 6 months.
As a large area of the Northern Hemisphere is receiving light from the sun, it is summer in the regions north of the equator. The longest day & the shortest night at these places occur on 21st June.
At this time in the Southern Hemisphere, all these conditions are reversed. It is winter season there. The nights are longer than the days.
Also, on 22nd December, the Tropic of Capricorn receives direct rays of the sun as the South Pole tilts towards it. As the sunrays fall vertically at the Tropic of Capricorn (23° S), a larger portion of the Southern Hemisphere gets light. Therefore, it is summer in the Southern Hemisphere with longer days and shorter nights. The reverse happens in the Northern Hemisphere. This position of the earth is called the Winter Solstice.