Snow or not, the winter solstice is fast approaching, and many students are looking forward to longer days of sunlight.

“The winter solstice marks the shortest day [of sunlight] of the year,” said Xiaoqing Wu, associate professor of geological and atmospheric sciences.

Mathematics explains why there is an exact day and time when the winter solstice happens. This year, the winter solstice occurs at exactly 6:38 p.m. Dec. 21.

“The Earth rotates around an axis that tilts 23.5 degrees away from a right angle to the sun,” Wu said. “The rotation causes the amount of sunlight reaching a given spot on Earth to vary as Earth orbits the sun during the year. The winter solstice marks the day when the North Pole is pointed exactly 23.5 degrees away from the sun’s line of fire, explaining why it’s the shortest day of the year.”

Dec. 21 is the shortest day in the Northern Hemisphere, making it the longest day for the Southern Hemisphere. Some places in Alaska don’t see any daylight during the winter solstice. But during the summer solstice, the sun never sets.

“For 182 straight days in the far North, there is no sunlight,” Wu said.

To experience no sunlight in the winter and sun all day long in the summer, Barrow, Alaska, is the place to go. Known as “the land of the midnight sun,” Barrow has no daylight from about mid-November to January, according to National Geographic. The inverse can be said for the summer, when the sun doesn’t set from mid-May to mid-July.

When students return for spring semester, days will become longer and there will most likely, be snow on the ground.

“After the winter solstice, the amount of sunlight will gradually increase each day until the summer solstice,” Wu said.