June 21 2018 – the solstice

This 12 months, the June solstice will fall on 21 June.  Within the northern hemisphere, it’s the day when there’s essentially the most daylight and when the Solar is at its highest within the noon sky.

 

Dawn on the solstice at Stonehenge, England – picture from Wikimedia commons

The origin of the phrase solstice is from two Latin phrases:  sol, which implies Solar, and sistere, to face nonetheless. It is because, on the time of the solstice, the Solar stops getting increased, seems to face nonetheless on the identical top for just a few days, after which will get decrease within the noon sky.

 

The graph beneath exhibits the utmost top, or elevation, of the Solar, measured in levels above the horizon, through the month of June. The graph is for a location 50 levels latitude North, which is identical latitude as the southern tip of the British Isles.  

The truth that the Solar’s elevation modifications step by step means the quantity of daylight additionally modifications little or no across the solstice. That is proven within the desk beneath, which supplies the dawn and sundown instances and the quantity of daylight in hours, minutes and seconds for June in London.

Desk of dawn and sundown instances for London (Time and Date 2018).

 

Exact definition of the solstice

The diagram above exhibits the Earth’s orbit across the Solar. For readability the sizes of the Earth and Solar have been enormously exaggerated.

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• Throughout June, marked as Awithin the diagram, the Earth’s North Pole is tilted in the direction of the Solar and the times are longer within the northern hemisphere.
• Throughout December, marked as Cwithin the diagram, the Earth’s South Pole is tilted in the direction of the Solar and days are longer within the southern hemisphere.
• At factors Band D, often called the equinoxes, neither pole is tilted in the direction of the Solar and the quantities of daylight within the northern and southern hemisphere are equal.

The exact astronomical definition of the June solstice (additionally referred to as the summer season solstice within the northern hemisphere) is the precise cut-off date when the North Pole is tilted furthest in the direction of the Solar. The instances for this occasion for the years 2016-2020 are given within the desk beneath – in GMT, in Tokyo time (which is 9 hours forward of GMT) and in Hawaiian time (which is 10 hours behind GMT).

 

 

As you’ll be able to see, the time of the solstice varies from 12 months to 12 months. It might probably fall on 20, 21 or 22 June, relying in your longitude (and thus your time zone).

Significance of the solstice to early man

The solstice was of nice significance to early man, and lots of prehistoric websites seem to have been constructed to have fun it. Probably the most well-known of those is Stonehenge, which is positioned in Wiltshire, England. It is a set of concentric stone circles constructed between 4000 and 5000 years in the past. It was an incredible feat of building for stone age man. The stone circle is over 30 metres in diameter. The most important stones are greater than 9 metres tall, weigh over 25 tonnes and had been hauled over 30 km to the location. It’s reckoned that the smaller stones had been moved from western Wales, a distance of 225 km (Jarus 2014).

Picture from Wikimedia commons 

On the centre of Stonehenge is a horseshoe association of 5 units of arches referred to as triliths, every containing three stones.  The open aspect of the horseshoe factors North East in the direction of a massive stone 80 metres away from the primary circle. At the moment this huge stone is given the identify  ‘The Heel Stone’.

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Picture from Wikimedia commons

The monument is organized in such a approach that, for just a few days both aspect of the June solstice and solely at these dates, somebody standing within the centre of the horse shoe and going through North East will see the Solar rise over the Heel stone.

How dawn on the summer season solstice at Stonehenge would have sorted the monument’s building.

It’s superb that prehistoric man constructed such a big monument to line up with the June solstice. It clearly will need to have been a main occasion for a individuals dwelling open air with solely pure daylight, and actually the solstice continues to be celebrated at Stonehenge right this moment. Trendy teams with historic origins, equivalent to Druids and Pagans, who revere the pure world greater than many trendy people, be part of roughly 30,000 individuals who flock to Stonehenge to look at the Solar rise on the solstice every year.

Apparently, to stop injury to such an necessary historic monument it isn’t usually doable to get proper as much as the stones. Nonetheless, the charity which manages the location English Heritage open it up yearly for the solstice, giving individuals a uncommon likelihood to stand up shut.

For the BBC report on the 2017 Stonehenge solstice celebrations click on on the hyperlink beneath.

https://www.bbc.co.uk/news/uk-england-wiltshire-40352528

The southern hemisphere

To these of you who dwell within the southern hemisphere the June solstice is the winter solstice, when the noon Solar is at its lowest within the sky. After the solstice the days begin getting step by step longer and the nights step by step shorter, though the change doesn’t actually turn out to be noticeable till July.

Notice

Strictly talking it isn’t true that for the entire northern hemisphere the noon Solar is at its highest within the sky on the solstice. On the Tropic of Most cancers, which is 23.5 levels north, and is proven because the higher crimson line in diagram beneath, the Solar is immediately overhead at noon on the June solstice. At low latitudes between the equator and the Tropic of Most cancers the Solar is immediately overhead at noon on two dates both aspect of the solstice. For instance, in San Juan, Puerto Rico, which lies 18.5 levels North of the equator, the Solar is overhead at noon on Might 13 and July 30.

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References

Jarus, O (2014) Stonehenge: Information & Theories About Mysterious Monument, Obtainable at: http://www.livescience.com/22427-stonehenge-facts.html(Accessed: 10 June 2016).

 

Time and Date (2018) London, ENG, United Kingdom — dawn, sundown, and daylength, June 2018, Obtainable at: http://www.timeanddate.com/sun/uk/london(Accessed: four June 2018).