The Winter Solstice – what it is and when exactly it happens – is one of those scientific topics that most people seem to have their own ideas about. Everyone who lives in the Northern Hemisphere recognizes winter as the coldest time of the year with the shortest days. But when does winter officially begin?
The first day of winter in 2017 is Thursday, December 21st. So if someone asks you “When is Winter?” you can respond with 4 days before Christmas on December 21st, 2017.
There is no simple answer to that question because there are two separate definitions of winter. One belongs to astronomy and the other one is meteorological.
But this is not the only problem we need to deal with if we want to answer the question of when winter begins. We also need to look at what solstices are and when they happen among other things.
When Is Winter Solstice in 2017?
This year the winter solstice in the Northern Hemisphere happened on December 21 exactly at 4:28 pm GMT or 11:28 am ET. Winter solstice happens at the same time all over the Northern Hemisphere. If you live in a time zone that is not GMT (Greenwich Mean Time) or ET (Eastern Time), you can just work out when the solstice happened where you live by converting the time zone.
In the Southern Hemisphere, the Summer solstice happened exactly at the same time.
Why Does The Winter Solstice Happen?
The first thing to note is that the reason why the winter solstice happens is the same reason that they are seasons.
And the reason is no other than the fact that our planet is tilted at 23.5 degrees on average from the sun. This tilt means that both hemispheres receive the same amount of annual sunlight.
This tilt increases and decreases throughout the year so solstices happen when the tilt as at its most severe.
So when the Northern Hemisphere is tilted the farthest from the Sun, the Winter Solstice happens there. And that logically coincides with the time that the Southern Hemisphere is tilted closest to the Sun and, therefore, it is when the Summer solstice happens there. As the Northern Hemisphere is titled the farthest from the Sun temperatures tend to cool down there. The Winter Solstice is when astronomers would say that winter begins. But, meteorologists use different criteria. From a meteorologist point of view, Winter 2017 began weeks before the Winter Solstice this year.
Meteorological winter encompasses the coldest months of the year: December, January, and February in the Northern Hemisphere, and June, July, and August in the Southern Hemisphere. So, for meteorologist winter always takes place at the same time every year. And anyone who looks at the calendar will be able to tell you when that is.
Why is there a difference between astronomical winter and meteorological winter? The difference between the two comes from the fact that meteorologists do not use astronomical criteria but, instead, use the temperature cycle. So, winter would be the coldest months and summer the warmest months.
Does It Get Dark Earlier on the Winter Solstice?
Because the winter solstice is the shortest day of the year, many people wrongly believe that the sun sets earlier on the winter solstice than at any other time of the year. But if you observed sunrise and sunset times you would notice that the sun sets earlier in early December than it does on the Winter solstice. But why is that?
There is a slight divergence between clock noon and actual noon. Noon happens when the sun is directly above us. Now, while noon happens exactly every 24 hours, the way our planet spins is not as precise as many people think. So, solar noons (as opposed to clock noons) does not happen exactly at the same time every day. That’s why sunrises and sunsets happen at different times throughout the year. And this is essentially why the sunset on Winter solstice happens a few minutes after it does earlier in the month.
Of course, the actual sunset time depends not only on your time zone but also on the latitude you are located. The further north you are the most extreme the season shifts in sunrises and sunsets. If you live close to the equator, then you will notice the difference between summer and winter in terms of sunset and sunrise much less. But also if you pay close attention to the sky and the sun’s arc, you will observe that the arc is the lowest on the winter solstice that at any other part. Of course, this is more noticeable the farther north you’d be.
Why Is the Winter Solstice Culturally Relevant?
The winter solstice has always been special to me as a barren darkness that gives birth to a verdant future beyond imagination, a time of pain and withdrawal that produces something joyfully inconceivable, like a monarch butterfly masterfully extracting itself from the confines of its cocoon, bursting forth into unexpected glory. – Gary Zukav
For millions of years, human beings in the different parts of the world have celebrated Winter solstice. A testament to this is the many ancient sites that still exist around the world. One of the best-known sits of the sort in Stonehenge in Wiltshire, England. This prehistoric monument goes back thousands of years. What many people do not realize is that Stonehenge, as we know it, was not built at once. In fact, it took more than a thousand years to be completed in many different phases.
Another important site in the Northern Hemisphere is ancient Mayan city of Tulum, which is located in Yucatan Peninsula, Mexico. Tulum is the Mayan word for wall, which is an unsurprising name for a wall-city. But the site was not always known as Tulum. There is an even older name for the site. Tulum used to be called Zama or city of the dawn because of its east-facing location.
Newgrange, Ireland is a prehistoric site that also goes back thousands of years. This monument is designed in such a way that the sun penetrates directly through it during the winter solstice. And that it is why historians and archeologists believe it was built as a Winter solstice site.