Today is the June Solstice, the first day of summer in the northern hemisphere. The new season officially begins at 23:09 UTC, which is 7:09 PM Eastern Daylight Time.

Astronomical seasons are the result of the tilt of the Earth’s axis, a 23.5° angle. Today, as summer begins, the northern half of our planet is slanted toward the sun.  This position allows the northern hemisphere to receive the sun’s energy at a more direct angle, warming the region.

Today is also the longest day of the year. Since the winter solstice in December, the arc of the sun’s daily passage across the sky has been moving northward.   Reaching its northern-most position at the Tropic of Cancer today, it stopped.  This phenomenon is where today’s event takes its name – solstice is a word derived from Latin meaning, “sun stand still”.

Beginning tomorrow, the sun will embark on its apparent journey southward and our daylight hours will slowly decrease.

Summer Solstice in Northern Hemisphere

Image Credit: scijink.nasa.gov