It's the Summer Solstice. Now What Happens?

[ThelmaLou]

@Miss_Mapp

I was staying at a hotel in Brae on Shetland, just above the 60N Parallel, a couple of weeks ago before the Solstice. It was still light out when I went to bed shortly before 11 pm. It was dawn when I woke briefly a little past 2 am. If there was any night in the 3 hours between, I missed it completely.

Whoa-- Shetland! That IS way far north. Do you have access to the murder-mystery-cop show set on Shetland? I love it.

[Miss_Mapp]

@ThelmaLou

Whoa-- Shetland! That IS way far north. Do you have access to the murder-mystery-cop show set on Shetland? I love it.

I’ve seen it, yeah.

Up on Shetland, they laugh about that show. They say they haven’t had a murder there since the 1930s.

[ThelmaLou]

@Miss_Mapp

I’ve seen it, yeah.

Up on Shetland, they laugh about that show. They say they haven’t had a murder there since the 1930s.

Hehe. Like Cabot Cove, Maine, right? Population of 600, and every week, 3-4 murders. Don’t ever invite Jessica Fletcher, Father Brown, or Jane Marple to your party.

[FordPrefect]

In Manitoba, I make sure to put the ice scraper back into the car in preparation for winter

[thorny_locust]

@eschereal

Nitpick: this is not exactly correct. The equinoxes are when the equator aligns with the sun (it is directly overhead on the equator at noon). Outside the tropics, day and night are not exactly the same length at the equinox: the point at which this happens is called the “equilux”. Where I live, the spring equilux occurs several days before the equinox, the autumn equilux a few days after. This varies by latitude.

Ignorance fought! Thanks for info.

[Slow_Moving_Vehicle]

@thorny_locust

Yes, exactly.

It’s the day of longest sunlight (in the Northern Hemisphere), after which the days do indeed start getting shorter. And the winter solstice is the day of shortest sunlight, after which the days start getting longer. Reverse the seasons for the southern hemisphere.

The days at the midpoint are called equinoxes, because they’re the days on which day and night are of equal length. Solstices are ‘sun standing still’, because daylength changes hardly at all at that point, and very slowly for some time before and after; it’s changing much faster around the equinoxes.

This question occurred to me a few days ago, when I realized it was the solstice: Do the hours of daylight get shorter after the solstice, by the same amount as they get longer before it? In other words, if the daylight on June 21 is (say) seven minutes and thirteen seconds longer than the daylight on June 20, will the daylight on June 22 be seven minutes and thirteen seconds shorter? Is it that exact?

[eschereal]

@Slow_Moving_Vehicle

This question occurred to me a few days ago, when I realized it was the solstice: Do the hours of daylight get shorter after the solstice, by the same amount as they get longer before it? In other words, if the daylight on June 21 is (say) seven minutes and thirteen seconds longer than the daylight on June 20, will the daylight on June 22 be seven minutes and thirteen seconds shorter? Is it that exact?

Do you know what a sine wave looks like? At the top and bottom of a sine wave, the rate of change is zero. At the point where the sine wave crosses the midpoint, the rate of change is highest. At my latitude, the length of daylight on June 21st is 8 minutes longer than on June 5th and July 6th.

[ftg]

@Slow_Moving_Vehicle

This question occurred to me a few days ago, when I realized it was the solstice: Do the hours of daylight get shorter after the solstice, by the same amount as they get longer before it? In other words, if the daylight on June 21 is (say) seven minutes and thirteen seconds longer than the daylight on June 20, will the daylight on June 22 be seven minutes and thirteen seconds shorter? Is it that exact?

No. Earth’s elliptical orbit messes things up a bit. Esp. since perihelion is near the solstice.

Look up the data for your location on the UNO page I gave earlier.

[Chronos]

Although, perihelion being near the solstice decreases the asymmetry. There’d be the most asymmetry if perihelion were right on the equinox, and none at all if perihelion were right on the solstice.

In any event, though, it still wouldn’t quite be a sine curve.

[eschereal]

Perihelion occurs about two weeks after the December solstice, and aphelion occurs about two weeks after the June solstice. You can see it on the calendar: the time from March to September equinox is a couple days longer than the opposite half of the year. But, when you plot the length of a day over the year, visually it looks very very close to a sinusoidal curve. It ain’t perfect, but what is?

[ftg]

@Chronos

Although, perihelion being near the solstice decreases the asymmetry. There’d be the most asymmetry if perihelion were right on the equinox, and none at all if perihelion were right on the solstice.

What I meant by “Especially since …” was that this is one of those close-but-no-cigar situations. Close enough that most people wouldn’t readily notice the asymmetry but not close enough that you could call it symmetric for all practical purposes.