Happy Summer solstice! It's the official start of the Summer season, and the northern hemisphere is walkin' on sunshine for a bit longer starting today. The solar party starts at 1:04 a.m. EDT on June 21, but for North American cities west of the Central Time zone, the solstice actually began on Thursday night.
For many, this joyous occasion means warmer weather, vacations, and lots o' golden rays — but how much do you really know about the longest day of the year?
Find out the essential facts about the inner workings of this annual astronomical event:
- The days are longer. Because of extended exposure to solar radiation, the Northern Hemisphere experiences an increase in temperature. The Summer solstice occurs on the day with the longest period of light.
- It's Winter in the South. The Summer solstice, which typically occurs on June 20-21, marks the beginning of Summer in the north and Winter in the southern hemisphere.
- Seasons are caused by the Earth's axis. The axis of the Earth, an imaginary line through the north and south poles, is tilted at 23.5 degrees relative to the sun. During the Summer, the northern hemisphere is tilted toward the sun, which is why that area receives more direct rays.
- The equinox is the inverse. When the northern hemisphere is tilted away from the sun, the area experiences Winter. The Winter solstice marks the shortest day of the year.
- Stonehenge is aligned with the solstice. The avenue of Stonehenge, a historic monument in Wiltshire, England, is mysteriously aligned with the sunset of the Summer solstice.