The summer solstice is the day when the Earth's North Pole is closest to the sun. It is also the day when the sun reaches its zenith in the sky. The winter solstice, or the shortest day of the year, occurs when the Earth's North Pole is tilted away from the Sun the most. At this time, the Sun is located on its southernmost point in the sky and begins its descent toward the south pole. At mid-summer, the days are long but they get shorter as we move into fall and spring. However, at mid-winter the days are getting longer but they don't seem to get any longer as spring approaches. This is because the amount of daylight changes throughout the year. At mid-summer, there is almost no nightfall in central Europe because the sun rises so early in the morning. At mid-winter, it is beginning to get light earlier every day because the sun is going down later in the evening. These are just average values. In some regions, such as the Arctic, midsummer and midwinter have very short days. There may be only a few hours of sunlight each day, if anything at all. In general, the length of day increases as we move north. At the South Pole, where mid-summer is defined as the date when the Sun is highest in the sky, the days are forever dark.