If the winter solstice is the longest night of the year, why does it mark the beginning of winter, rather than the very middle of it?
In: Earth Science
The temperature is changing downward the fastest on this day, since there is the least amount of sun. Until the amount of sun per day reaches the average amount of sun (basically at the spring equinox/the last day of winter), the daily temperature will tend to go down day after day.
I get this and agree. Because once we reach it, we are on our way out of winter. The dead middle of winter is when it should be imo
Edit: clarification
Societally it is because the seasons are things we invented, so we can decide it happens whenever we want*. Historically, it is because the solstices and equinoxes were easier to define astronomically than some arbitrary point halfway between them.
A more physically based answer is because the temperature/weather lags behind solar radiance. This is because of a concept called ‘thermal inertia’, which basically means that the environment still retains some warmth from summer and autumn. A simple model of weather would have the winter solstice be the day that the most heat was lost, but that means it gets colder the day after, and the day after that, etc. Actual weather is more complicated, but it still holds that the coldest day should occur a significant time after the solstice.
*cultures from more equatorial regions often defined the seasons differently. People in Sub Sahara Africa defined seasons by the direction of the crescent moon, which corresponded to the rainy and dry seasons. Ancient Egyptians defined their season/year by the star Sirius, which could first be seen predawn approximately 1 month before the Nile flooded.
The temperature of any given day has a bit to do with the sun, and a lot to do with the temperature of the land and sea.
The earth is constantly radiating heat, and the shortest day is when it will absorb the least heat from the sun – but it still has a lot of heat left over from autumn.
Over the next couple of months, although the energy being absorbed from the sun is more than the day before, it is still less than is given off each day. So every day, the land and sea (and thus the climate of that hemisphere) gets colder and more wintery.
The balance doesn’t shift until the hemisphere is absorbing more energy each day from sunlight than it is radiating, which is around the time that day and night are equal lengths (i.e. the vernal equinox).
So, the coldest months are between the winter solstice and the vernal equinox.
It’s based on astronomy — each solstice and equinox marks a position of Earth in orbit 90 degrees apart, which marks the beginning of what we call a season. Its what ancient people could easily observe and Mark. It’s also a solstice in Australia, but down there the days are longest and it’s getting warmer.
It doesn’t mark the beginning of winter, but it isn’t the coldest day due to something called seasonal lag, basically it takes a long time for the oceans around the continents to cool down keeping the land next to it warmer for longer. https://youtu.be/2i8MX73Uhyo
It’s not just the shortness of the day but the length of the night that makes winter. The longer night means there is more time for heat to escape and less time to reheat the land and sea.
This is similar to how ice ages happen. It’s not the coldness of winter but how mild the summers become (due to less axial of tilt). The milder summers can’t melt the ice sheets fast enough so every year ice accumulates until we have an ice age.
The rate at which you lose heat is dependent on the current temperature. The rate at which you gain heat is dependent on the current day length, and how high the sun gets in the sky. It takes some time for the temperature to catch up to what it would be if we got this amount of sunlight every day all the time. Basically, it’s still holding some heat from the warmer parts of the year.
Well, keep in mind that how we celebrate things is radically different when “pagans” celebrated.
Winter Solstice was about the *birth of the sun* with days growing longer & it *wasn’t* the celebration of the *start* of winter. It’s been hijacked to correspond with Jesus birth. This all has to do with the Church appropriating customs because prior to the Middle Ages, it was thought that Jesus was born in the Spring (May 20 according to some theologians and based on current Gregorian calendar which is not the same calendar used several centuries ago) NOT winter.
Every Western holiday we have in modern times is based on a “pagan” holiday that’s been converted to conform with Church teachings. Even Halloween, Day of the Dead, & All Soul’s Day are based on “pagan” celebrations & beliefs. Halloween though has become corrupted into a costume party & has essentially lost all meaning thanks to commercialism.
In Australia, first day of Spring is September 1, December 1 is first day of Summer….etc.
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