Today is the Summer solstice, the longest day of sunlight in the year. It’s my favorite day. It’s a great day for reflection and deep thoughts about life, but its an equally great day to get out and enjoy life. If you are a pagan this is an especially important holiday, but what is the solstice?
The summer solstice occurs during the hemisphere’s summer. This is the June solstice in the Northern Hemisphere and the December solstice in the Southern Hemisphere. Depending on the shift of the calendar, the summer solstice occurs some time between June 20 and June 22 in the Northern Hemisphere and between December 20 and December 23 each year in the Southern Hemisphere.The same dates in the opposite hemisphere are referred to as the winter solstice.
One of my favorite years was 1989. It was the year I got to experience TWO summer solstices and NO winter solstice. In June 1989, Bill and I were waiting to meet Max, out son, who we were adopting from Paraguay. we spent the whole day getting his room ready. Painting wallpapering and putting in some carpeting. Then in December 1989, we met Max in Acunsion, Paraguay. One of the happiest days of my life. Being in the southern hemisphere, we experienced a 2nd summer solstice. We walked in the sun and watched Max start to crawl and had a fabulous dinner at what the Paraguayans thought was a ridiculously early hour – 8:30 PM. Here’s Max’s baby picture.
Just another fun fact about the summer solstice –
Ever since the Earth has had liquid oceans and a moon, its rotation has been gradually slowing over time due to tidal friction. That means — over very, very long periods of time — the days have been getting steadily longer. About 4.5 billion years ago, it took the Earth just six hours to complete one rotation. About 350 million years ago, it took 23 hours. Today, of course, it takes about 24 hours. And the days will gradually get longer still.
Given that, you’d think 2018 would be the longest day in all of history. But while it’s certainly up there, it doesn’t quite take top honors.
That’s because tidal friction isn’t the only thing affecting Earth’s rotation; there are a few countervailing factors. The melting of glacial ice, which has been occurring since the end of the last ice age 12,000 years ago (and is now ramping up because of global warming), is actually speeding up Earth’s rotation very slightly, shortening the days by a few fractions of a millisecond. Likewise, geologic activity in the planet’s core, earthquakes, ocean currents, and seasonal wind changes can also speed up or slow down Earth’s rotation.
When you put all these factors together, scientists have estimated that the longest day in Earth’s history (so far) likely occurred back in 1912. That year’s summer solstice was the longest period of daylight the Northern Hemisphere has ever seen (and, conversely, the 1912 winter solstice was the longest night we’ve ever seen).
Eventually, the effects of tidal friction should overcome all those other factors, and Earth’s days will get longer and longer as its rotation keeps slowing (forcing timekeepers to add leap seconds to the calendar periodically). Which means that in the future, there will be plenty of summer solstices that set new records as the “longest day in Earth’s history.”
The World According to Laura 