Happy Summer Solstice!

At about 8 pm (EDT) today, the sun will have reached a high point in its yearly cycle. Today is the Summer Solstice, the time when the Sun reaches its maximum of 23.5° above the Celestial Equator (that is, the projection of Earth's equator onto the sky). It rises at 23.5° north of east, reaches the highest point in the sky it will achieve during the year, and sets north of west. That also means it will spend more time above the horizon than at any other time during a year, making it the longest day of the year. From now on, there will be fewer hours of sunlight each day, until we reach the low point - the Winter Solstice, around Dec. 21.

Ancient cultures tended to celebrate every solstice. Even today, we mark it as a significant event - it's the official first day of summer!