The Official First Day of Summer

Image from ecotime.blogspot.com

The beginning of summer has officially been announced thanks to the summer solstice, the longest day of the year, which heralds in the summer months each year—if only for the northern hemisphere.

While the northern hemisphere experiences the longest day of the year, (when the sun stays out the longest), the southern hemisphere experiences the shortest.  In six months, on December 20^th, our roles will change.  The northern hemisphere will experience the winter solstice, which officially begins winter, while the southern hemisphere will experience their summer solstice.

This is because of Earth’s axis of tilt.  Our planet’s vertical axis is tilted 23.4 degrees relative to the elliptical plane of our orbit around the sun.  This tilt causes different amounts of sunlight to reach different regions.  On the northern hemisphere’s summer solstice the North Pole is dipped more toward the sun than on any other day.  A common misconception is that the Earth’s proximity towards the sun is what drives summer and makes the solstice the longest day of the year.  In reality, northern hemisphere experiences the summer solstice when we’re farthest from the sun.  The tilt of the earth is what drives the seasons, not it’s distance away from the sun—which is why the poles only experience two very long seasons, summer and winter.

Even though the earth receives the most sunlight on the summer solstice, we often don’t feel the heat of it for another couple of weeks.  This is because Earth atmosphere and ocean act like heat conductors; they absorb the sun’s heat and reradiate it over time.

In many places, summer unofficially started a while ago, announced by sweltering heat and bright, sunny days.  For others where there is still a bite to the air the summer solstice is a perfect marker for the beginning of summer, and a great reason to party.   In Scandinavia it marks the start of the midsummer festival, a party themed with the growth and rejuvenation that summer brings.  In Iceland, where it’s very northerly location makes it an extra-long sunny day, bars stay open through the sun-filled night.  There are many other celebrations throughout the world that mark this sun-filled day, as well as many bar specials throughout the U.S.