Science of the Winter Solstice


As I mentioned in my article on Advent, the Romans, during the later Empire period, celebrated a holiday known as the Saturnalia, beginning on the Winter Solstice. The solstice can occur any time between December 20 to 23, though usually on the 21st or 22nd; but until modern instrumentation, interpolating the exact date with ancient astronomically aligned instruments was imprecise, and the ancient Romans set their Saturnalia on December 25.


ancient astronomically aligned instrument

Solstice comes from the Latin “solstitium,” meaning “Sun, standing still.” This year it occurs on December 21 at 21:48 GMT (or UTC) and marks the first day of the Winter season in the Northern Hemisphere from an astronomical perspective.



Earth enjoys different seasons because the planet is tilted 23 degrees and 27 minutes off the perpendicular to the plane of orbit. This means that the world revolves like a tilted spinning top. The Winter Solstice is the shortest day of sunlight as the Sun is at its lowest arc in the sky, at least in the Northern Hemisphere.

The farther north one is from the Equator, the more pronounced this is in Winter. However, as the Earth continues its orbit, the hemisphere angled closest to the sun changes, and the seasons are reversed.


Solstice: Standing Still

In the Northern Hemisphere, the Sun appears at its lowest point in the sky, and its noontime elevation seems to be the same for several days before and after the solstice. It looks like the Sun is “standing still” from the perspective of someone standing on the Earth until, following the Winter Solstice, the days grow longer and the nights shorter. In London, for example, on the Winter Solstice, the Sun sets at 3:53 pm, and the “day” is only 7 hours and 50 mins long.




Solstice and the Roman Saturnalia

I’ve written previously here and here about how the Romans celebrated Saturnalia around this time of year, honoring the head of their pantheon of Titans. Saturday gets its name from Saturn.



Temple of Saturn, Roman Forum

Yule Love It

Similarly, the Northern European tradition of Yule comes from the Norse name of the head of the Norse pantheon, Odin, known also as Jol or Jólner. Yuletide begins on December 25 and extends for 12 days. J.R.R. Tolkien‘s The Lord of the Rings novels, influenced by the author’s love of Norse mythology, includes “Yule” in the Shire Reckoning calendar at the turn of the year.


Know-it-all Facts to impress your Family and Friends

It is called the “shortest day of the year” or the “extreme of winter,” though it begins the Winter season. You cast your longest shadow at noon on this day. It has the fewest hours of sunlight and the most hours of darkness.

  • New York City: 9 hours, 15 minutes of sunlight
  • Helsinki, Finland: 5 hours, 49 minutes of sunlight
  • Barrow, Alaska: 0 minutes of sunlight — no sunrise at all until January 22



Bill Petro, your friendly neighborhood historian

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About billpetro

Bill Petro has been a technology sales enablement executive with extensive experience in Cloud Computing, Automation, Data Center, Information Storage, Big Data/Analytics, Mobile, and Social technologies.

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