A solstice is a time in the annual motion of the Sun where the Sun's north‐to‐south motion appears to briefly stop and then start to reverse direction. There are two solstices in a given year, the summer solstice and the winter solstice. In the northern hemisphere, the summer solstice marks the northern extreme of the Sun's annual motion and the longest day of the year. Similarly, the winter solstice marks the shortest day of the year. During the autumnal and spring equinoxes (meaning equal night), the Sun crosses the celestial equator, and there are approximately an equal number of hours during the day and night. Explore the details of solstices and equinoxes using Wolfram|Alpha.