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The BBC has “Stolen” my Interesting Shortest Day Facts December 21, 2014

Posted by mwidlake in off-topic.
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Today, the 21st December 2014, is the “shortest day” in the Western Hemisphere this year, the day in which the period of daylight is shortest (it’s the 22nd if the last Leap Year is more than 2 years ago).

I’ve blogged before about how the evenings start drawing out BEFORE the shortest day and, despite it not being an Oracle technical post and was also one of my first posts {when almost no one came by}, it gets a modest but interesting number of hits. If you look at the below graphs (sorry, it’s not as clear as it could be unless you click on the image), you will see there is a burst of hits at the end of the year and a smaller rise in interest at the middle of the year.

Evenings_post_stats

These hits are all via search engines, mostly on the phrase “Evenings drawing out”. Obviously there is a correlation with people both in the Northern (for the December hits) and Southern (for the June hits) hemispheres getting sick of the longer periods of dark and googling about when it will start to change. And finding this strangely relevant post on what is otherwise a nerdy IT site.

{Isn’t this an example of what all the IT blather about Big Data and the cloud is about? Finding patterns in search engine data etc? My blog is not exactly Big Data though 🙂 }

Well, The BBC is probably going to steal my thunder, this year at least, as they have done an article on the phenomena, though concentrating more on the mornings continuing to get darker after the “shortest day”. It’s not a very good article in one respect, though, as it has the phrase “perceived a curious development” as though this mismatch between the shortest day and mornings/evenings getting later is a recent change. I’m pretty sure that the tilt of our planet and it’s orbit around the sun has not changed enough in my lifetime to alter this situation! In fact, I checked – evenings started drawing out on around the 13th December 50 years ago, exactly the same as this year and exactly the same as is expected in 50 years too. It does describe well, however, how it is our shifting clock (due to the longer day length around now) that causes the shift.

Another little oddity about shortest day and our planet is in respect of when you think the earth is furthest from the sun. Most of us in the Northern hemisphere assume it is on the shortest day, because it is colder and darker. But it is not. we are actually nearest to the sun, at “perihelion”, on the 3rd Jan. So not even “shortest day” but just after :-).

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Comments»

1. David Harper - December 21, 2014

The axial tilt of the Earth does vary, but only by a degree or two either side of the average, and very, very slowly. Also, the date of perihelion also changes, and this will also affect the phenomenon you’ve described here, but again, the variation happens extremely slowly. In both cases, the changes take place over hundreds of thousands of years, so they are not noticeable over the span of a human life.

mwidlake - December 22, 2014

Thanks for the clarification David, I knew I could rely on you. I was 99.87% sure it changed over geological periods but I did a quick check for approx “zero change” in a 100 year span, just to be sure.
The article does give a nice description of how it is our clock day shifting in relation to the astronomical day that causes the effect – in effect “noon” is getting later compared to our watches (sorry, smartphones) as the true day is currently longer than 24 hours.

2. Miserable Dark Days of Winter Relieved by Data | Martin Widlake's Yet Another Oracle Blog - December 22, 2015

[…] start drawing out being around a week before the shortest day, and even about how I have become fascinated by how popular this off-topic post has become. Worry not, I shall not go over that date-discrepancy material again or how we in the Northern […]


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