D · Biking in the buff on a summery day before Easter [1 April 2021]

First summery day with maximum temperatures above 25°C on Wednesday before Easter
Photo 1: First summery day with maximum temperatures above 25°C on Wednesday before Easter

In 2021, the first summery day with maximum temperatures above 25°C took place on Wednesday before Easter. Only a few commercial aircraft, again polluting the atmosphere, disturbed the blue sky.

In 2020, natury reported: "[…] There were only a few other cyclists on the paths in the southern Münsterland region, with whom I could exchange friendly greeting. Cars were even rarer. I did not meet any pedestrians at all. […]" This year, it was completely differen:t It almost seemed, as if people had the cooler weather outlook for Easter days in mind and unceremoniously brought forward their Easter excursion to this Wednesday!

Temperature went up to impressive 25.7°C at 3:30 p.m. – then, you're happy, when a breeze caresses your skin: natury enjoyed the day biking in the buff.

He visited spoil heaps of a strontianite mining tunnel. This rare mineral SrCO3 was used to produce sugar from sugar beet until 1883. Then, people learned to change the process of sugar production and use the more common and therefore cheaper coelestine (strontium sulphate = SrSO4). A 4,500-year-old stone cist grave was the next place of interest.

Afterwards, natury cycled through southernmost parts of Münsterland towards Drei-Schlösser-Route [en: Three Castles Route].

Tombe de l'âge de pierre
Photo 4: A stone box grave from the Neolithic period, about 4,500 years old, is one of the oldest testimonies of human settlement in Westphalia.

As an over-70, he chose for the rest a bench, on which he had the whole place to himself – that worked well despite the partly dense cycling excursion traffic.

The season has started: Next, we have to face a cool Easter Sunday.

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German archaeoastronomer Dr Steinrücken of Westfälische Volkssternwarte Recklinghausen has determined, that the stone cist grave in Dalmer has an astronomical alignment. The north-eastern horizon from the direction of the stone cist grave is dominated by the (for Münsterland conditions) prominent ridge of the Höxberg. In fact, the northern rising points of the moon – seen from the stone box grave – frame the mountain flanks of the Höxberg at the Great and Small Lunar Equinox. The longitudinal axis of the tomb is aligned extremely precisely with the rising point of the Great Lunar Equinox.

Astronomically, these extreme situations of moonrise occur because the orbital inclinations of the ecliptic (apparent solar orbit) of 23.5° and moon's orbit of 5° against the earth's equator add up to 28.5° or subtract to 18.5°. The fact, that these special astronomical constellations helped to determine the choice of location for a communal burial ground, which was used for centuries, shows the importance of celestial events for the people of that time.

Sun's point of rising (yellow) moves back and forth between a southernmost point in winter and a northernmost point in summer during the course of the year. Moon's point of rising also moves back and forth between a southernmost and a northernmost point within one lunar cycle (approx. 27 days). However, these extreme moonrise points are not constant: every 18.6 years, these two extreme moonrise points are significantly further apart, than the extreme sunrise points, or major lunar solstice (red), in between, the two extreme moonrise points are significantly less far apart than the extreme sunrise points, or minor lunar solstice (blue).

Hint: Lunar standstill

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D · Early feeling of spring in February [23 February 2021]

Short, dark winter days, together with restrictions to stem Corona infections, were already stressful enough for people. The onset of winter in February with unusually extensive snowfall and persistent frost causing road and rail traffic to collapse in many places in North Rhine-Westphalia, restricted life even further.

View over the Volmetal valley to the city centre: The mild air of just under 20°C was not enough for everyone to do without clothing. Photo: Rainer
Suddenly and just as unexpectedly, the air temperature rose by more than 30°C: Early spring arrived with 20°C warmth and 10 hours of sunshine – almost no one could stay indoors. Get out and enjoy nature, was their personal order of the day for many: The first birds were chirping their mating calls, and next to a few remnants of snow, colourful spring blossoms rose up between brown leaves and thin greenery.

Also, a few naturists took advantage and went on their first nude hike of this year in a city forest of their home town Hagen in Westfalia, less than 1000 metres from the main train station. The hike was delightful for more than two hours. In between, we took a break on a bench in the sunshine with coffee and cake, which Thomas had carried. We exchanged spring greetings and good wishes with many other people along the way.

 – Report and photos: Rainer

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