The astronomical beginning of the summer could not have been better: in 2019, Friday, June 21, literally kicks off a long summer weekend. And, as most of us already know, the summer solstice marks the longest day of the year. Why Solstice? The days then become shorter again, so the sun slowly turns away from its highest position. So far, so good. For all of those who wants to shine with even more knowledge on Friday evening while sharing a barbecue with family and friends, we have put together five exciting facts.
1.The solstice takes place everywhere at the same time.
Despite the worldwide time shifts, the solstice takes place all over the world at the same time. The event is not measured by time zones and coordinates, but marks the time when the zenith of the sun reaches the north tropic. In mid-European summer time, the sun reaches its highest point at around 6 pm. There is one difference anyway: While people north of the equator celebrate the beginning of summer, winter is heralded in the south.
2. The longest day does not start with the earliest sunrise.
Although the summer solstice marks the longest day of the year, the sun rises even earlier a few days before the solstice. Even the latest sunset of the year does not take place on the longest day: In the following days the sun sets about one minute later. The tilt of the Earth’s axis and the elliptical shape of the Earth’s orbit around the sun causes the position of the sun to shift day by day. In June, the sun is slowing down, so the sun rises a little earlier before the solstice – and a little later afterwards.
3. The longest day is not the same everywhere.
The longest day of the year does not cover the same period of time everywhere. Why? The closer a place is to the Arctic Circle, the longer the days around the summer solstice are. That’s why the longest day in Hamburg is about an hour longer than in Geneva or Zurich.
4. The summer solstice is not in the warmest time of the year.
The astronomical beginning of summer is not the warmest time of the year. Statistically, the average temperature in July and August is significantly higher than in June. On the one hand, this is due to the energy surplus created by the sun’s radiation in the atmosphere. On the other hand, the process is supported by the fact that it takes a while for the Earth’s surface to warm up – especially when it comes to the oceans.
5. In 2020, the summer solstice will not take place on 21 June.
While the longest day of the year in the 20th century in our time zone could sometimes fall on the 22nd of June (most recently in Berlin in 1986), we have been able to celebrate the solstice relatively steadily since the beginning of the 2000s on 21st June. For the first time in 2020, the phenomenon will resume on June 20, almost exactly 17 minutes before midnight.
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