The Summer Solstice this year will be on June 21st at 14.57 UTC. UTC (Coordinated Universal Time)is the same as GMT but unlike GMT is never a time zone. It is a time standard, a basis for civil time and time zones worldwide. This means that no country or territory officially uses UTC as a local time. The UK uses GMT as a time zone until the change to BST which means for us the solstice will be at 15.57 BST.
Solstice comes from the Latin words sol, 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 Tropic of Cancer is not only a book by Henry Miller that you shouldn’t have read when you were 14 but also the most northerly circle of latitude on Earth at which the Sun can be directly overhead. This occurs on the June solstice, when the Northern Hemisphere is tilted toward the Sun to its maximum extent.
Solstices happen twice a year—in June and December. The December solstice takes place around December 21. On this day, the Sun is precisely over the Tropic of Capricorn (another book by Henry Miller that you shouldn’t have read…).
One might think that since it is summer in the Northern Hemisphere, the Earth is closest to the Sun during the June solstice. But it’s the opposite. The Earth is actually farthest from the Sun during this time of the year. In fact, the Earth will be on its Aphelion (the point where a planet is at its furthest from the sun) a few weeks after the June solstice.
The Earth’s distance from the Sun has very little effect over the Seasons on Earth. Instead, it the tilt of Earth’s rotational axis, which is angled at around 23.4 degrees, that creates seasons.
The direction of Earth’s tilt does not change as the Earth orbits the Sun; the two hemispheres point towards the same direction in space at all times. What changes as the Earth orbits around the Sun is the position of the hemispheres in relation to the Sun. The Northern Hemisphere faces towards the Sun during the June solstice, thus experiencing summer. The Southern Hemisphere tilts away from the Sun and therefore has their winter.
Even though the June solstice is the longest day in the Northern Hemisphere, most places do not see the earliest sunrise of the year on this day. The earliest sunrise happens a few days before, and the latest sunset takes place a few days after, the June solstice.
This happens because of the imbalance between time measured using clocks and time measured by a sundial. Don’t ask! Too complicated to go into here.
The hottest day of the year in the Northern Hemisphere usually comes a few weeks or sometimes months after the solstice. This is because it takes time for the oceans and landmasses to warm up, which again allows for higher air temperatures.
And one last fact that isn’t really related but I kept thinking about it while putting this blog together:
68% of the Earth’s land mass is located in the Northern Hemisphere, 32% in the Southern.
About 71 percent of the Earth’s surface is water-covered, and the oceans hold about 96.5 percent of all Earth’s water.
The surface of the Southern Hemisphere is 80.9% water, compared with 60.7% water in the Northern Hemisphere. The Southern Hemisphere is a very watery place.
So have a wonderful longest day whether in London, Stonehenge or the canyons of your very own mind.