Today is the winter solstice and the first day of winter in the Southern Hemisphere. It's all due to Earth's tilt, which ensures that the shortest day of every year falls around 21 June.
The solstice has been an auspicious day since ancient times, with countless cultural and religious traditions marking the winter solstice.
During the winter solstice the sun hugs closer to the horizon than at any other time during the year, yielding the least amount of daylight annually. On the bright side, the day after the winter solstice marks the beginning of lengthening days leading up to the summer solstice.
"Solstice" is derived from the Latin phrase for "sun stands still." That's because—after months of growing shorter and lower since the summer solstice—the sun's arc through the sky appears to stabilize, with the sun seeming to rise and set in the same two places for several days. Then the arc begins growing longer and higher in the sky, reaching its peak at the summer solstice.
The solstices occur twice a year (around 21 December and 21 June) because Earth is tilted by an average of 23.5 degrees as it orbits the sun—the same phenomenon that drives the seasons.
Being the shortest day of the year, the winter solstice is essentially the year's darkest day, but it's not the coldest. Because the oceans are slow to heat and cool, in June the seas still retain some warmth from summer, delaying the coldest of winter days for another month and a half.
Can I See The Solstice?
Ancient people didn't know about Earth's orbit but they still observed the solstice by noting what was happening in the skies overhead.
The sun's arc across the sky has been steadily dropping lower and becoming shorter since June. Now, at the north's winter solstice, it has reached its lowest possible arc—so low in fact that in the few days surrounding the solstice it appears to rise and set in the same place.
That phenomenon produced the Latin phrasing from which the word solstice was derived, meaning “sun stands still.”
The sun's low angle also means that your noontime shadow is the longest of the entire year during the winter solstice.