A scientific guide to winter solstice in the Hudson Valley

The winter solstice happens on Wednesday, December 21 at 10:27 p.m. Let’s take a look.

On that day and the next, the noontime sun stands at its lowest position of the year. Your shadow will extend to its longest length. But okay, that won’t make or break your day. The bigger news is that we will then have the fewest minutes of daylight. Starting Friday, December 23 days will be longer and the Sun will be higher up. Since solar strength depends on the sun’s height, we’ll start feeling greater warmth on our skin. Given that the ground and the air take awhile to catch up we won’t reach our coldest average temperature until the third week of January, a full month from now.

The most visible change is that you can look out your most southwest facing window and see the Sun set at its leftmost position of the year. If you’re an early bird and can watch the sunrise at around 7:15 a.m., that will happen at its rightmost spot, ever.

Thanks to the lag between the days’ variable lengths and the inflexible length of each clock’s minutes and hours, we already had our darkest afternoon on December 7 and will not suffer our darkest morning, meaning latest sunrise, until the first week of January. Those are the most tangible factors affecting things like perils of twilight driving, deer avoidance, and feasibility of late afternoon strolls.

Radio stations that announce changes in sunlight length will, starting Thursday, start to announce increases. This will be very little at first, a matter of seconds a day, but will steadily grow until daily daylight expands by three daily minutes in March. The amount depends critically on your location. During my annual Aurora odyssey in Alaska, (SpecialInterestTours.com) our groups have noticed the March daylight expansion as an amazing 7 minutes per day. There’s almost an hour of extra daily sunshine each and every week! It’s so rapid up there that human habits undergo a visible metamorphosis.

But here, where the extra daily sunshine is closer to 20 minutes after each week, nature steadily bestows something resembling a slowly opened gift package that nonetheless changes our lives dramatically enough that our daily April and May routines bear little resemblance to now. And slipping a bit of nighttime astronomy into this discussion, there will also be a radical planet change. Right now every planet is nicely visible while late spring will find them vanishing one by one.

Our planet reaches its perihelion, our closest point to the sun on January 4 when we zoom through space at our fastest speed of seven city blocks per second. Yet even with Earth and Sun both rapidly changing, our atmosphere coupled with our general science obliviousness combines to deliver only a few tangible consequences, known and appreciated by, hopefully, you.