Today is the December Solstice, the first day of winter in the northern hemisphere. The new season officially begins at 23:03 UTC, which is 6:03pm EST here in New York City.
The astronomical seasons are produced by the tilt of the Earth’s axis – a 23.5° angle – and the movement of the planet around the sun. During the winter months, the northern half of the Earth is tilted away from the sun. This position brings the hemisphere the least amount of solar energy and its coolest temperatures of the year.
Since the summer solstice in June, the arc of the sun’s daily passage across the sky has been dropping toward the southern horizon and daylight hours have been decreasing. Today, it reached its southern most position at the Tropic of Capricorn (23.5° south latitude) marking the shortest day of the year. This observable stop is where today’s event takes its name. Solstice is derived from the Latin words “sol” for sun and “sisto” for stop.
Now, the sun will move northward again in our sky and daylight hours will slowly start to increase. Marking this transition from darkness to light, the winter solstice has long been a cause for celebration across many cultures throughout human history.