Celebrating the Longest Day

P1060482 (Small)San Francisco Exploratorium teacher Tory Brady demonstrated how the solstice happens to an appreciative gathering at the Cesar Chavez Solar Calendar this evening, June 21, the longest day of the year.  Using a globe about the size of an exercise ball, Brady showed how the Northern hemisphere including the arctic at this time is in the sun for the longest number of hours per day.  In fact, in the Arctic, the sun does not appear to set at all in this period.  Meanwhile the Southern hemisphere is experiencing just the opposite, the shortest days of the year.  But around the equator, there’s virtually no change — the sun appears to set and rise about the same time every day all year round.  Brady also showed that the apparent path of the sun in the sky is always at a slant, never directly overhead in our latitudes.  Only in the equator does the sun appear to travel directly overhead from rising to setting.  Of course, Brady pointed out, the sun isn’t rising or setting at all.  It’s the rotation of the earth that makes it seem that way.

Brady also commented that the summer solstice is a sad occasion, because from now on the days will get shorter, so really we should be mourning instead of celebrating.  The sun hardly seems to move at all right around the solstice — that’s where the name solstice comes from, meaning “sun standing still” — but then picks up steam as it were, with the loss of daylight gradually accelerating as we move toward the winter solstice.  The winter solstice is the time for joy and celebration, because from then on the days get longer again.

As the sun set promptly at 8:30, part of the solstice gathering in the park posed for this solstice group portrait:

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