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STEM, Uncategorized

Winter 2015 (or Groundhog Day for me)

Imagine my surprise when I woke up this morning to find out that today, not yesterday, is the first day of winter. I felt like Bill Murray in the movie, Groundhog Day, for about 15 minutes.

 

EarthOrbit_3531458b_Source-TheTelegraph

Earth’s Seasonal Orbit (Source: The Telegraph)

 

Thinking that maybe I incorrectly heard KPNX’s local meteorologist, James Quiñones, say that today is the first day of winter, I googled “winter solstice 2015” and quickly found out two things: There is the first day of winter, and then there is the winter solstice. They are related but not necessarily the same thing.

Here are some winter solstice facts collected from various sources including The Telegraph and NASA:

  • It is the shortest day of the year.
  • The solstice happened at the same time for planet earth on December 21 at 11:48 p.m. ET. That’s Monday night in New York and Atlanta, Tuesday morning in Paris and Nairobi, and Tuesday afternoon in Tokyo and Sydney.
  • It is caused by the earth having a tilt of about 23.5 degrees off of its vertical axis. (This causes the northern hemisphere to be tilted toward or away from the sun at different times of the year as the earth makes its orbit.)
  • In December, when the North Pole is tilted towards the sun, the northern hemisphere gets the fewest hours of sunlight for the year.
  • At the same time, the southern hemisphere is closest to the sun.
  • The winter solstice occurs in the southern hemisphere in June.

And here is what I really wanted to know:

  • The shortest day of the year usually occurs on December 21st, but can happen on any day between December 20th to December 23rd.
  • This is attributed to the fact that the solar year is 365.2422 days longer than the calendar year of 365 days per year. (And perhaps why we have a leap year every 4th calendar year.)
  • December 23rd solstices are very rare. The last one happened in 1903, and the next one is scheduled for 2303.

There are a number of well-known celebrations that occur around the world on the winter solstice each year. One of the more popular celebrations is at Stonehenge in Wiltshire, England. More interesting is that Stonehenge, the site of a prehistoric monument, is carefully aligned on a sight-line that points to the winter solstice sunset.

However, the first day of winter, technically is December 22, 2015. And that is what threw me because I had assumed both the solstice and the first day of winter would occur on the same day.

Here’s to making the best of each day regardless of the season of the year!

[Post Note: This post was modified on Tuesday, 12.22.2015 at 10:00 p.m.]

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About Vi Brown

Vi is principal and CEO of Prophecy Consulting Group, LLC, an Arizona firm that provides business and engineering services to private and public clients. Prior to establishing her consulting practice in 2001, Vi worked with Motorola, Maricopa County Government, Pacific Gas & Electric, CH2M Hill, and Procter & Gamble. As an adjunct faculty member, Vi teaches undergraduate calculus classes and graduate level environmental courses. She is also a professional speaker.

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