Solstice Science: Why Winter Starts Dec. 21

The rise of the sun is seen at a 2,300-year-old structure in Peru, between Tower 1 and Cerro Mucho Malo at the June solstice, 2003, viewed from the western solar observatory. The sunrise position at the solstice has shifted to the right approximately 0.3° from the year 300 BC.
(Image credit: Ivan Ghezzi)

While snow marks the beginning of winter for many people, the first official day of winter is Sunday, Dec. 21, known as the December solstice.

It's a point in time that marks a transition in our planet's annual trip around the sun.

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Robert Roy Britt

Robert is an independent health and science journalist and writer based in Phoenix, Arizona. He is a former editor-in-chief of Live Science with over 20 years of experience as a reporter and editor. He has worked on websites such as Space.com and Tom's Guide, and is a contributor on Medium, covering how we age and how to optimize the mind and body through time. He has a journalism degree from Humboldt State University in California.