Monday, June 22, 2015
The June Solstice marks the Northernmost point the sun reaches, with the North Pole tilted towards the sun at about 23.5 degrees. That tilt—axial tilt, it’s called—is why we have seasons at all.
So, this morning the sun was directly over (relative to the ecliptic plain) the Tropic of Cancer. The sun now “moves south”, and in six months it will be directly over the Tropic of Capricorn.
Northern Hemisphere days now start to get shorter, and Southern Hemisphere Days start to get longer (although barely noticeable for weeks). Then, six months from now, the process will reverse—and a good thing it does, too, because agriculture would be challenging without seasons on both sides of the equator.
It’s not hard to see why our ancestors millennia ago put supernatural or spiritual significance on solstices, given how important seasons were to their survival. It’s less clear to me why some people still do, apart from less developed parts of the world, maybe, or those who observe them for a sense of connection to our distant ancestors. In any case, like I’ve said in the past, I don’t know anyone in New Zealand who takes much notice.
So, solstices, like equinoxes, are part relevant, part irrelevant. The relevant part is that they mark points in the seasons, but in Australasia they’re also irrelevant in the sense that our seasons start on the first of the month the solstices and equinoxes happen.
The graphic up top is a screen grab from timeanddate.com, and shows how they display events like the arrival of a solstice in UTC and another timezone (although I did remove the "current times").