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Event Cache

Solstice @ Noon

A cache by madip Send Message to Owner Message this owner
Hidden : Thursday, June 21, 2018
Difficulty:
1 out of 5
Terrain:
1 out of 5

Size: Size: other (other)

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Geocache Description:


SK: Počas stretnutia 21. júna 2018 od 12:05 do 12:55 v Medickej záhrade v cente Bratislavy prežijeme spolu okamih slnovratu o 12:07 aj miestne poludnie, ktoré na súradniciach eventu nastane o 12:51 stredoeurópskeho letného času.

EN: During the event on 21st June 2018 from 12:05 p.m. to 12:55 p.m. in Medická záhrada in the centre of Bratislava, we shall be together in the moment of the solstice (at 12:07 p.m.) and at local noon, which on the event coordinates will occur at 12:51 p.m. Central European Summer Time.

 

SK:

Zem vo vesmíre vykonáva dva periodické pohyby, z ktorých ľudstvo odpradávna, tisícročia skôr ako ich pochopilo, odvodilo dve dôležité jednotky na meranie času: rok a deň.

Prvým pohybom, s periódou jeden rok, je otáčanie Zeme okolo Slnka po eliptickej dráhe, ktorá leží v rovine prechádzajúcej stredom Slnka. Je to tá istá rovina, v ktorej sa pri pozorovaní zo Zeme zdanlivo pohybuje slnko voči hviezdam. Zdanlivá dráha Slnka po oblohe sa volá ekliptika. Priemet zemského rovníka zo stredu Zeme na nebeskú klenbu sa volá svetový rovník.

Druhým pohybom, s periódou 24 hodín, je rotácia Zeme okolo osi prechádzajúcej jej stredom. Os rotácie je voči kolmici na rovinu obežnej dráhy Zeme okolo Slnka vychýlená, zviera s ňou uhol, ktorý kolíše medzi 22,1° a 24,5° v cykle asi 40 000 rokov a v súčasnosti je približne 23,5 stupňa. Rovnaký uhol zviera rovina svetového rovníka s rovinou ekliptiky.

Vďaka odchýlke osi rotácie Zeme od kolmice na rovinu jej obežnej dráhy môže byť slnko v nadhlavníku, a to dvakrát za rok, nielen na zemskom rovníku, ale aj na miestach so severnou alebo južnou zemepisnou šírkou menšou ako táto odchýlka. Tieto miesta tvoria pás ohraničený na severe obratníkom Raka a na juhu obratníkom Kozorožca, čo sú v súčasnosti rovnobežky so zemepisnou šírkou (severnou a južnou) približne tých spomenutých 23,5°. Len raz v roku však nastane okamih, keď je slnko v nadhlavníku na niektorom mieste na samom obratníku Raka. Býva to okolo 21. júna a je to júnový slnovrat, na severnej pologuli vtedy začína astronomické leto a na južnej zima. Podobne raz v roku, okolo 22. decembra, je Slnko v nadhlavníku na niektorom mieste na obratníku Kozorožca, je to okamih decembrového slnovratu, vtedy na severnej pologuli začína zima a na južnej leto.

Slovo slnovrat je odvodené od toho, že deklinácia slnka voči rovine svetového rovníka sa vtedy mení z rastúcej na klesajúcu alebo z klesajúcej na rastúcu, akoby sa slnko na chvíľu zastavilo a začalo sa vracať. V okamihu slnovratu nadobúda absolútna hodnota deklinácie slnka celoročné maximum. Na severnej pologuli je deklinácia kladná pri júnovom slnovrate a záporná  pri decembrovom, na južnej pologuli je to opačne. Zároveň deň júnového slnovratu medzi východom a západom slnka je na severnej pologuli najdlhší v roku (noc je najkratšia) a na južnej je deň najkratší a noc najdlhšia. Podobne deň decembrového slnovratu je na južnej pologuli najdlhší a na severnej najkratší.

V roku 2018 nastane júnový slnovrat 21.júna o 10:07 UTC, čo je 12:07 stredoeurópskeho letného času. Dve minúty predtým, čiže o 12:05 SELČ sa stretneme na daných súradniciach v Medickej záhrade v centre Bratislavy, kam možno prísť cez obednú prestávku z väčšiny pracovísk v hlavnom meste a v okolí sa dá najesť.

 Logbook bude k dispozícii 50 minút, čiže do 12:55 SELČ, teda ešte 4 minúty po miestnom poludní, ktoré na mieste eventu nastane o 12:51 stredoeurópskeho letného času. Na 15° východnej dĺžky je totiž miestne poludnie presne o 13:00 SELČ a event sa koná ešte o 2° 7,195' východnejšie, pričom každá uhlová minúta na východ urýchli slnečný čas o 4 časové minúty

 Kto sa prihlási logom WA najneskôr týždeň (168 hodín) pred začiatkom eventu a zúčastní sa na ňom, môže si za 20 eurocentov kúpiť príležitostné drievko (SWG).

EN:

The Earth is performing two periodic movements in the cosmic space, from which mankind, millennia before understanding them properly, derived two important units for measuring time: a year and a day.

The first movement, having the period of 1 year, is that of the Earth around the Sun on an elliptical orbit, which lies in a plane passing through the centre of the Sun. It is the same plane which contains the apparent path of the Sun with respect to the stars when observed from the Earth, called the ecliptic. The projection of the Earth’s equator from its centre to the celestial sphere is called the celestial equator.

The second movement, having the period of 24 hours, is the rotation of the Earth around its axis passing through its centre. This axis is tilted from the perpendicular to the Earth’s orbit. The tilt varies between 22.1° and 24.5° in a cycle of some 40,000 years and at present equals approximately 23.5 degrees. The same angle is formed by the planes of the celestial equator and of the ecliptic.

Thanks to the tilt between the Earth’s axis of rotation and the perpendicular to the plane of its orbit, the Sun can be in the zenith, namely twice a year, not only for an observer on the equator, but also in places having northern or southern latitude less than the tilt. These places form a band delimited by the Tropic of Cancer in the North and the Tropic of Capricorn in the South, which at present are the parallels having northern / southern latitude of the mentioned 23.5°. There is only one moment in the year when the Sun is in the zenith at some place on the Tropic of Cancer itself. The moment occurs around 21st June and is called the June solstice. It marks the beginning of the astronomical summer on the northern hemisphere and the beginning of winter on the southern hemisphere. Similarly, there is exactly one moment in the year, which occurs around 22nd December, when the Sun is in the zenith at some place on the Tropic of Capricorn. It is the beginning of winter on the northern hemisphere and of summer on the southern.

The word “solstice” comes from Latin sol (sun) and sistere (to stand still), because at the solstices, the Sun’s declination relative to the celestial equator changes from ascending to descending or vice versa, as if it came to a stop before reversing direction. The absolute value of the Sun´s declination attains its yearly maximum in the moment of the solstice. On the northern hemisphere it is positive in the moment of the June solstice and negative in the moment of the December solstice, while the opposite is true on the southern hemisphere. Also, the day (time between sunrise and sunset) of the June solstice is the longest in the year on the northern hemisphere and shortest on the southern. Analogously, the day of the December solstice on the southern hemisphere is the longest and, on the northern hemisphere, the shortest of the year.

In 2018, the June solstice occurs on 21st  June at 10:07 a.m. UTC, that is 12:07 p.m. CEST (Central European Summer Time). Two minutes earlier, at 12:05 p.m. CEST, we shall meet at the given coordinates in „Medická záhrada“ park in the centre of Bratislava, which is not difficult to access during the lunch break from most places in the capital and there are opportunities for eating nearby.

The logbook will be available for 50 minutes, until 12:55 p.m. CEST, that is until 4 minutes after the local noon, which will occur at 12:51 p.m. CEST at the place of the event. This is because the local noon at 15° East occurs at 1:00 p.m. CEST and the event is 2° 7,195' more to the east, every minute of longitude pushing the local time 4 minutes of time earlier.

Those who log WA not later than one week (168 hours) before the start of the event and attend it will be offered, for 0.20 €, a special Slovak Wood Geocoin (SWG) made for the occasion.

Additional Hints (No hints available.)



 

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Last Updated: on 7/21/2018 1:00:08 AM Pacific Daylight Time (8:00 AM GMT)
Rendered From:Unknown
Coordinates are in the WGS84 datum

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