In case you weren’t paying attention, summer and the longest day of the year in the northern hemisphere arrived early this year.
The summer solstice usually falls on June 21 but moved up in 2012 because it’s a leap year. On this day, the Earth’s axis is tilted at 23.4 degrees to the plane of the solar system, and the North Pole is most tipped toward the sun, which means more daylight than any other day if you live north of the equator.
Over the years, the solstice triggered massive celebrations at places like Stonehenge and the Great Pyramids of Egypt, which were designed to have the sun set exactly between two pyramids on the solstice itself. Nowadays, the longest day of the year generally means running your air conditioner even longer than usual and applying more sun block.