The sun resides some 26,000 light-years from the Milky Way’s center, in a tendril of our home galaxy known as the Orion Arm. Every 230 million years, the sun and the solar system it carries with it makes one orbit around the Milky Way’s center. Though we can’t feel it, the sun traces its orbit at an average velocity of 450,000 miles an hour.
As the Sun rises higher in the sky on the North Pole day by day, the midnight sun gradually expands south until it reaches just south of the polar circle around the beginning of June.
One of the reasons that the midnight Sun doesn’t end directly on the polar circle, but can also be seen a little further south, is refraction; The fact that light bends when it hits Earth’s atmosphere. Refraction makes the Sun visible above the horizon several minutes before it actually gets there.
24 hours of light is perfectly possible without midnight Sun, because it does not get dark as soon as the Sun sets. Before night falls, there are three stages of twilight civil, nautical and astronomical. During the summer, many areas south of where the midnight Sun can be seen, have what is known as white nights. Nights which are light, but the Sun’s disk isn’t visible for the enitre night.
In the Southern Hemisphere, it is opposite. There are polar nights when the Northern Hemisphere has polar days. The only landmass far enough south in the Southern Hemisphere to have midnight Sun, is Antarctica.
Solstice comes from the Latin words soll, meaning Sun and sistere , meaning. to come to a stop or stand still. On the day of the June solstice, the Sun reaches its northernmost position, as seen from the Earth. At that moment, its zenith does not move north or south as during most other days of the year, but it stands still at the Tropic of Cancer. It then reverses its direction and starts moving south again.
The opposite happens during the December solstice. Then, the Sun reaches its southernmost position in the sky – Tropic of Capricorn – stands still, and then reverses its direction towards the north.
Even though most people consider June 21 as the date of the June solstice, it can happen anytime between June 20 and June 22. June 22 solstices are rare – the last June 22 solstice in UTC time took place in 1975 and there won’t be another one until 2203.