Wednesday, June 17, 2020

The Summer Solstice


A solstice occurs twice a year when the sun is at its furthest distance away from the equator (June and December).  An equinox also occurs twice a year, but it happens when the sun physically crosses the imaginary line in the sky above the Earth’s equator (March and September).  This year, our northern hemisphere summer solstice for the USA will occur on June 21.

Here are some interesting facts about the June solstice:

·         A solstice (or equinox) will occur at the exact same moment of time for every location on the earth.  For a June solstice in the northern hemisphere, it will be the moment the sun reaches its highest point in the northern sky, (Tropic of Cancer)

·         For June 2021, the summer solstice moment will occur at 10:32 pm CDT on Monday, June 21

·         The daily daylight length will continue to get shorter between the June solstice and the December solstice

·         The exact date and time of the solstice will vary from year to year, but will occur between June 20th and 22nd depending on the various time zones across the planet.  A June 22nd solstice is quite rare for North America as the last one occurred in 1975 and the next one is not forecasted until the year 2203

·         If you live on the Arctic Circle, you will experience the one day a year without a sunset, and conversely, if you live on the Antarctic Circle, you will experience the one day a year without a sunrise

·         The Earth does not move at a constant speed in its elliptical orbit around the sun, therefore the seasons are not of equal length.  Roughly speaking for the northern hemisphere, the spring season is 92.8 days in length, summer is 93.6 days, autumn is 89.8 days, and thankfully, the winter season is the shortest at 89.0 days

·         The inconsistent speed of the elliptical orbit also creates variability in the amount of daily daylight loss or gain throughout the year

·         The direction of tilt, or amount of tilt in the earth in relation to the sun does not alter over the course of the year.  The seasons change because of a hemisphere’s relation to the sun as the earth orbits.  In June, the northern hemisphere points towards the sun, in December, the southern hemisphere points towards the sun

·         The Summer Solstice date will provide 16 hours 2 minutes of daylength for Grand Forks, ND

·         Conversely, the shortest day of the year (Winter Solstice) for Grand Forks, ND will result in only 8 hours and 23 minutes of daylight

·         It’s interesting to note that the daylight hours on the longest day of the year (16 hrs 2 min), do not match the darkness hours on the shortest day of the year (15 hrs 37 min) for Grand Forks, ND.


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