Marking the shortening of nights and lengthening of days, it is actually the shortest day of the year for anyone living in the Northern hemisphere.
The solstice occurs when the sun is directly over the Tropic of Capricorn and the simple reason why the solstice occurs is that the Earth spins around its own tilted axis.
The tilt — possibly caused by a massive object hitting Earth billions of years ago — means that for half the year, the North Pole is pointed toward the sun (as in the picture below). For the other half of the year, the South Pole gets more light. It’s why we have seasons.
Places that are far away from the Equator and closer to the North Pole get less sunlight during the solstice. Even though the Solstice marks the shortest day of the year and longer nights, it does not make it the coldest month of the year, January and February are usually the colder months.
Ever since the Earth has had liquid oceans and a moon, its rotation has been gradually slowing over time due to tidal friction. That means that over very, very long periods of time, the days have been getting steadily longer. About 4. 5 billion years ago, it took the Earth just six hours to complete one rotation. About 350 million years ago, it took 23 hours. Today, of course, it takes about 24 hours. And the days will gradually get longer still.
Do other planets have Solstice too?
Yes! All the planets in our solar system rotate on a tilted axis and therefore have seasons, solstices, and equinoxes. Some of these tilts are minor like Mercury but others are more like the Earth or are even more extreme like Uranus.
Not only does the solstice mark the shortest day, it also brings along the spirit of festivity as Christmas follows only a few days after. So, enjoy the sunshine while you can, and light up your nights, because it is almost Christmas folks.
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