Today is the winter solstice for the most of folks who reside on planet soil (that is, in the to the north hemisphere). The awful report: That means we have the least allowance of daylight today (roughly 9h20m for me in Boulder, for example, at 40° north latitude). The good report: From here on out for the next six months, the days get a bit longer while the nights get shorter.
Of course, for astronomers this is the other way round, more like good news/bad news, since we like long nights. Um, unless you’re a solar astronomer, I guess, then the first case concerns. except once afresh you’re a neutrino or wireless astronomer, in which case you don’t care. Day and night are all attractive much the identical to them.
Anyway, the solstice isn’t characterised by the extent of the day and evening, to be dependable. That’s an effect, not the origin.
Astronomers use a coordinate system on the sky that’s very similar to longitude and latitude on soil, except we call them Right Ascension and declination for historical causes. There’s also a celestial equator, and a celestial north and south beam!
Over the course of a year, as the Earth orbits the Sun, the Sun seems to move against the backdrop stars in the sky. It moves east/west in a full circle (360°) one time per year, but furthermore downhill rides away from the celestial equator by about 23.5° both north and south over that identical time time span, due to the tilt of the soil. In the summer (for northern folks afresh) it reaches its most to the north declination around June 21, and its southernmost issue round December 21 every year. When it’s in the north in June it’s high overhead the horizon at noon, and when it’s in the south in December it’s much lower in the atmosphere at noon.
Well, guess where we are now! Today at 17:11 UTC (12:11 EST) the Sun will be as far south as it can go, and we call that instant the winter solstice. From then on out it will creep north, getting higher in the atmosphere every day… until June, when it peaks (at the summer solstice, of course) and then begins heading south afresh.
Note that when the Sun is lower in the atmosphere at the winter solstice, the route it takes is shorter, so the day is shorter, and the night longer. The reverse is true at the summer solstice. glimpse? That’s what I meant by the extent of day and evening being an effect of the Sun’s position. Because the soil is tilted, the Sun’s place in the sky changes, as do the extents of day and evening.
I find this stuff endlessly fascinating. The cyclical environment of astronomical shift is magnificent, a cosmic clockwork that is predictable and understandable. It can be complex, and have unforeseen (and wondrous) outcomes, but if we try, we can grab it… just as assuredly as the Sun will come up tomorrow forenoon. And be a little bit more distant north when it does.
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