Summer Solstice 2013 Ushers in Summer and Celebrations Around the World

Today marks summer solstice, the first day of summer and the day with the most sun. So what is summer solstice exactly, and what are people doing to celebrate it?

As self-made astro-personality Neil Degrasse Tyson said in a tweet:

June 21 -- 1:04 AM ET. Geeks: Sun reaches north-most spot on ecliptic above celestial equator. Everyone else: Summer begins.

— Neil deGrasse Tyson (@neiltyson) June 21, 2013

"Geeks: Sun reaches north-most spot on ecliptic above celestial equator. Everyone else: Summer begins," Tyson tweeted.

In layman's terms, the summer solstice is the longest day of the year because the Earth's axis (in this case, the northern point) is facing the sun. While it marks the beginning of summer it also means that the days will only grow shorter from here on out until winter solstice, the day with the least daylight out of the whole year. Winter solstice will arrive Dec. 21 this year.

Aside from the astronomical implications, summer solstice carries a lot of weight in countries and cultures worldwide. Many festivals are held on this day, often times in the name of fertility or religion. Yoga lovers flocked to Times Square for free yoga classes all day; and hordes of people converged on Stonehenge to celebrate the solstice. The numbers themselves are staggering - 15,000 registered for the yoga classes in Times Square and approximately 20,000 showed at Stonehenge - and they prove that summer solstice, while not as commercially successful as Thanksgiving or Christmas, is still an important part of many people's lives.

"Solstice is one of our most poignant rituals, for as we watch the bright-colored blossoms burn to ash, we remember that life is brief and so must be deeply cherished in every moment," wrote Pagan blogger Starhawk.

"Let this Solstice be a time to instead embrace change. As the sun sets at last on the longest day, take some time to consider how everything must eventually reach its peak, and transform," she continued.