WINTER SOLSTICE 2022: THE FIRST DAY OF WINTER
We often think of the winter solstice as an event that spans an entire calendar day, but the solstice actually lasts only a moment. Specifically, it’s the exact moment when a hemisphere is tilted as far away from the Sun as it can be
The winter solstice marks the official beginning of astronomical winter (as opposed to meteorological winter, which starts about three weeks prior to the solstice). The winter solstice occurs once a year in each hemisphere: once in the Northern Hemisphere (in December) and once in the Southern Hemisphere (in June). It marks the start of each hemisphere’s winter season. When one hemisphere is experiencing their winter solstice, the other is simultaneously experiencing their summer solstice! This is all thanks to Earth’s tilted axis, which makes it so that one half of Earth is pointed away from the Sun and the other half is pointed towards it at the time of the solstice.
The winter solstice holds significance across a variety of cultures, as it signals the changing of the seasons. Some ancient peoples even marked the solstice using huge stone structures, like Newgrange in Ireland. In some cultures, the solstice traditionally marked the midway point of the season rather than the start of it, which explains why holidays such as Midsummer Day are celebrated around the first day of summer.
On the day of the winter solstice, we are tilted as far away from the Sun as possible, which means that the Sun’s path across the sky is as low in the sky as it can be. Think about the daily path of the Sun: It rises in the east and sets in the west, arcing across the sky overhead. During the summer, the Sun arcs high in the sky, but during the winter, it arcs lower, closer to the horizon. How can we observe the effects of solstice ourselves? On the day of the solstice, stand outside at noon and look at your shadow. It’s the longest shadow that you’ll cast all year! Do this again on the day of the summer solstice and you’ll see almost no shadow.
What is a Solstice?
A solstice is one of the two times of the year when the positioning and tilt of Earth relative to the sun results in the most amount of daylight time or the least amount of daylight time in a single day. There are two solstices during the year: one that occurs around June 20–22 (usually June 20 or 21) and one that occurs around December 20–23 (usually December 21 or 22).
The solstices are traditionally considered to mark the start of summer and winter. But which season begins with each solstice depends on which hemisphere you’re in. In the Northern Hemisphere, the summer solstice occurs in June and the winter solstice occurs in December. In the Southern Hemisphere, it’s the opposite. The summer solstice results in the longest day of the year, meaning it has the most time of daylight, and the winter solstice results in the shortest day of the year, meaning it has the longest period of darkness.
In contrast, an equinox is one of the two times of the year when the amount of daylight and nighttime hours are just about of equal length. The two equinoxes occur around March 20–21 and September 22–23. In the Northern Hemisphere, the vernal equinox (or spring equinox) occurs in March and the autumnal equinox occurs in September. In the Southern Hemisphere, it’s the opposite.
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