The winter solstice in the Northern Hemisphere is known as the summer solstice in the Southern Hemisphere. In the Northern Hemisphere, this is the shortest day of the year, and after that, the days start to get longer and the nights shorter. In the Southern Hemisphere, Dec. 21 is the longest day of the year, and the days begin to shorten and the nights lengthen afterward.

Earth’s closest point to the sun actually comes in early January. It may seem surprising that it’s not summer in the Northern Hemisphere at that time but the difference between the sun at its farthest point (in July) and at its closest is just 3.3 percent, not enough to change seasons. It’s the tilt of Earth’s axis and not its orbit that gives the seasons.