What is a solstice?

Earth’s axis is tilted about 23.4 degrees relative to its orbit. Twice a year, this tilt causes one hemisphere to be maximally tilted toward the Sun (summer solstice) or away from it (winter solstice). The June solstice, around 20–21 June, brings the longest day in the Northern Hemisphere and the shortest in the Southern. The December solstice, around 21–22 December, reverses this. At the Arctic Circle, the Sun does not set on the summer solstice (midnight sun), and at the Antarctic Circle, it does not rise (polar night). Many cultures have celebrated solstices for millennia, including at Stonehenge, which aligns with the midsummer sunrise.