This year, the winter solstice takes place on Thursday, December 22 at 12:30 a.m. EST. Many people know that the winter solstice marks the day when winter officially stars in the Northern Hemisphere, and when days will start to become incrementally longer. But what exactly is going on?
It all has to do with the tilt of the Earth's axis. In other words, the Earth does not rotate on its axis straight up and down in relation to its path around the Sun. Rather, it is always angled at 23.5 degrees. So as the Earth travels around the Sun during the course of the year, one pole is tilted more toward the Sun that the other with the exception of two days: the vernal (spring) and autumnal (fall) equinoxes.