Astronomical winter begins this week for the northern hemisphere, with the winter solstice falling on 21 December. This marks the shortest day and longest night of the year, a phenomenon that has been celebrated across cultures for centuries. Ancient Rome's Saturnalia, for instance, involved a week of feasting and gift-giving where masters served their slaves.
The winter solstice occurs when Earth's north pole is tilted as far away from the sun as possible. As a result, the sun appears at its most southerly position in the sky and reaches its lowest noon altitude in the northern hemisphere.
In the southern hemisphere, the situation is reversed: the south pole is tilted closest to the sun, leading to the summer solstice with the longest day and shortest night.
While the winter solstice marks the beginning of astronomical winter, meteorological winter is considered to start on 1 December. For those in the north, the good news is that from this point onward, the sun will gradually rise higher at noon, and days will begin to lengthen.
