Summer Solstice is here - Solstices and Equinoxes

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Welcome to Summer Solstice for 2018. I'm choosing my words carefully. Often this is referred to as the longest day, which is partially correct, because it is based on daylight hours.  Of course the day still remains 24 hours long, but the number of daylight hours are the greatest they will be for this year.

In 2018, for Wellington, the sun rises at 5:42am and sets at 8:57pm, making the day light hours 15 hours and 15 minutes. The further south you go the daylight hours are longer. For instance, in Invercargill the sun rises at the slightly later time of 5:50am but doesn't set until 9:40pm. This makes the daylight hours there 15 hours and 50 mins!  Southern areas see even more daylight hours. In Antarctica the sun is now up all day and reaches its highest point in the sky at Summer Solstice.

So what exactly is the summer solstice and what causes it. Put simply, summer solstice is the point at which the South Pole is further most inclined to the sun and in 2018 this occurs at 11:23am on December 22.. It's often referred to as the "sun moving furthermost south" but again that's not strictly true. The sun doesn't move at all.

A solstice is created because earths rotation isn't flat as you would normally imagine it. If it were flat then for us here is New Zealand there would be no summer or winter at all. Instead the earth is tilted at an angle somewhere around 23.5 degrees.

As the earth continues on it's path of orbit, less and less sun is exposed to the southern hemisphere   The two days between where the sun sits directly above the equator , are called the equinox.

At the same time in the Northern hemisphere the earth is tilted away from the sun, which leads to longer nights and a winter solstice at the same time as our summer solstice.. In many places in northern Europe, sunlight is limited to only a few hours or even no sunlight at all.

The summer solstice was a day of cultural significance for many ancient civilisations, who marked it with magnificent festivals and celebrations. The Vikings were known to use the summer solstice, or "midsummer", as a time to convene and discuss legal matters and resolve disputes. They also visited wells believed to offer healing powers and built huge bonfires. The bonfire tradition has carried over to modern day, with Iceland being a popular destination for "Viking" style summer solstice celebrations.

In Britain, the Druids are thought to have practiced ritual celebrations during midsummer, with some believing these took place at Stonehenge. The historical accuracy of this has become unimportant to many Britons and tourists alike, who now gather at the ancient site to watch the sun rise. 

Of course this variation in sun (heat or energy) has an impact on the weather we experience, which we will go into further in another post

Further research:

  • Why isn't the summer solstice on the same day each year?

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