Winter solstice 2020, the shortest day of year and the official start of winter, is on Monday, December 21 but how does it works

For six months, the days have grown shorter and the nights have grown longer in the Northern Hemisphere. But that’s about to reverse itself.

Winter solstice 2020, the shortest day of year and the official start of winter, is on Monday, December 21. How it all works has fascinated people for thousands of years.

First we’ll look at the science and precise timing behind the solstice. Then we’ll discover some ancient traditions and celebrations around the world (though many of 2020’s celebrations are being canceled or modified for the pandemic). And finally,
we’ll learn about a delightful show in the heavens special for winter solstice 2020.

The science and timing behind a winter solstice

The winter solstice marks the shortest day of the year in the Northern Hemisphere, when the sun appears at its most southerly position, directly overhead at the faraway Tropic of Capricorn.

The situation is the reverse in the Southern Hemisphere. There, the December solstice marks the longest day of the year — and the beginning of summer in places such as Argentina, Australia and South Africa.

When exactly does it occur?

The solstice usually — but not always — takes place on December 21. The time that the solstice occurs and the day itself shifts because the solar year (the time it takes for the sun to reappear in the same spot as seen from Earth) doesn’t exactly match up to our calendar year.If you want to be super-precise in your observations, the exact time of the 2020 winter solstice will be 10:02 Coordinated Universal Time (UTC) on Monday. Here are some examples of when that will be for local times around the world:

  • — Tokyo: 7:02 p.m. Monday
  • — Bangkok: 5:02 p.m. Monday
  • — Dubai: 2:02 p.m. Monday
  • — Rome: 11:02 a.m. Monday
  • — Casablanca, Morocco: 10:02 a.m. Monday (same as UTC)
  • — Boston: 5:02 a.m. Monday
  • — Vancouver: 2:02 a.m. Monday
  • — Honolulu: 12:02 a.m. Monday

What places see and feel the effects of the winter solstice the most?

Daylight decreases dramatically the closer you are to the North Pole on December 21.

People in balmy Singapore, just 137 kilometers or 85 miles north of the equator, barely notice the difference, with just nine less minutes of daylight than they have during the summer solstice.

Much higher in latitude, Madrid, Spain, still logs in a respectable nine hours and 17 minutes of daylight during the winter solstice.

The difference is more stark in frigid St. Petersburg, Russia, where the sun will rise at 10 a.m. and set at 3:53 p.m. resulting in less than six hours of anemic daylight.

Residents of Nome, Alaska, will be even more sunlight deprived with just three hours, 54 minutes and 33 seconds of very weak daylight. But that’s downright generous compared with Prudhoe Bay, Alaska. It sits inside the Arctic Circle and won’t see a single ray of daylight.

What causes the winter solstice to even happen?

Because the Earth is tilted on its rotational axis, we experience seasons here on Earth. As the Earth moves around the sun, each hemisphere experiences winter when it’s tilted away from the sun and summer when it’s tilted toward the sun.

Wait. Why is the Earth tilted?

Scientists are not entirely sure how this occurred, but they think that billions of years ago, as the solar system was taking shape, the Earth was subject to violent collisions that caused the axis to tilt.

What other seasonal transitions do we mark?

The equinoxes, both spring and fall, occur when the sun’s rays are directly over the equator. On those two days, everyone has an equal length of day and night. The summer solstice is when the sun’s rays are farthest north over the Tropic of Cancer, giving us our longest day and the official start of summer in the Northern Hemisphere.

Winter solstice traditions and celebrations

It’s no surprise many cultures and religions celebrate a holiday — whether it be Christmas, Hanukkah, Kwanzaa or pagan festivals — that coincides with the return of longer days.

Ancient peoples whose survival depended on a precise knowledge of seasonal cycles marked this first day of winter with elaborate ceremonies and celebrations. Spiritually, these celebrations symbolize the opportunity for renewal, a shedding of bad habits and negative feelings and an embracing of hope amid darkness as the days once again begin to grow longer.

Originally published at CNN