2016-12-21 / News



The astronomical winter is officially upon us – the period when sunlight fades faster and darkness takes over.

Today, in fact (or, more precisely, Wednesday, Dec. 21 at 5:44 a.m.), is when winter solstice occurs: We’ll get just 9 hours and 34 minutes of daylight, the shortest amount of daylight we’ll see all year. Nighttime consumes the remaining 14 hours and 26 minutes.

Dwindling daylight is even more pronounced farther north. Portland, Maine, will catch just 8 hours and 56 minutes of sun, and Anchorage, Alaska, will eke out just 5 hours and 27 minutes. Conversely, southern locales will have longer periods of daylight. Miami, Florida, for instance, will bask in 10 hours and 32 minutes of daylight.

The reason for the winter solstice, and the four seasons, is due to the Earth’s tilt. “The Earth’s rotational axis is tilted to its plane of rotation around the sun. As a result, the sun appears higher or lower in the sky at a particular time of day in [the Earth’s] yearly revolution around the sun,” explains Terry Barker, amateur astronomer and member of the Richmond Astronomical Society.

Intuitively, many think that winter is ushered in when the Earth is farthest from the sun. But the Earth’s proximity to the sun does not influence the seasons. Instead, we experience the four seasons due to our planet’s tilt. During summer, we are tilted toward the sun, for example, and the sun’s rays hit us directly, delivering more solar radiation.

Astronomers and meteorologists define the seasons differently.

“The astronomical seasons are based on the position of the Earth in relation to the sun,” Barker explains. “The meteorological seasons are based on the annual temperature cycle. Meteorological winter, for example, includes December, January and February, whereas the astronomical start of winter for 2016 is Dec. 21.”

Though the winter solstice brings the shortest amount of daylight, it also offers hope. Each day after the winter solstice, the amount of daylight increases. By Jan. 31, we’ll receive about 10 hours and 19 minutes of daylight, and by Feb. 28, our daylight increases to 11 hours and 21 minutes. ¦

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