This article first appeared on Vox.com
Why do we have a summer solstice, anyway?
The summer solstice is upon us: June 20th and the 21st will be the longest days of 2017 for anyone living north of the equator. If pagan rituals are your thing, this is probably a big moment for you. If not, the solstice is still pretty neat.
Technically speaking, the summer solstice occurs when the sun is directly overhead the Tropic of Cancer, or 23.5° north latitude. In 2017, this will occur at exactly 12:24 am (Eastern) on the 21st. (But we can celebrate on either day.)
Below is a short scientific guide to the longest day of the year (though not, as we’ll see, the longest day in Earth’s history — that happened back in 1912).