Page 18 - IAV Digital Magazine #586

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Winter Seasons vs. Winter Solstices
For many people, the win- ter solstice marks the changing of fall to winter. But there’s a difference between the winter sol- stice—called the astro- nomical first day of win- ter—and the first day of the winter season, which is called the meteorologi- cal first day of winter. Each year, meteorolo- gists—people who study weather and climate— determine the first day of the winter season based on temperature records. In the United States, winter lasts about 90 days. Scientists often tie it to the calendar, so that winter falls during the latter part of December, January,
February, and the early part of March.
One myth is that the win- ter solstice is the coldest day of the year. But the coldest temperatures are often still at least a month away, depending on where you live. That’s because the Earth’s land and water takes time to cool down.
On the winter solstice, if you stand outside at noon and look at your shadow, it will be the longest shadow you cast the entire year. Here’s why:
Every day, the sun rises in the east and sets in the west, tracing an arc
across the sky. The height of that arc changes during Earth’s yearly orbit around the sun. As our planet orbits, one pole is tilted toward the sun, and one pole is tilted away from it. During winter in the Northern Hemisphere, the North Pole is tilted away from the sun, so the height of the arc is low—and your shadow looks long.
In fact, during the days around the winter solstice, the sun is so low on the horizon that it appears to rise and set in the same place. That’s why the word solstice can be translated to "sun stands still' in Latin.
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