Earth Science


Sundogs over Huntington, Vermont.

My third-floor office is a commanding venue for a nap.  Reclined in a worn swivel chair with my unsheathed feet stacked on the heat grates, I slip into my best unproductive hours.  When my eyes deign to open, the scenery is ripe for a Chamber of Commerce brochure.  The golden chapel domes and brown brick mortar of the university sit regal and prim before the white speckled ribs of New York and the glass pool of Champlain.  It’s plain lovely.  Especially on biting cold mornings, near 10:00, when some change of guard ushers students out from every academic pore to wade the gray salty paths to their next nook.  It’s one vain pleasure up in my aerie, watching without sympathy the cold scholars scurry.

New Englanders are a bundled bunch this time of year, thick in flannel and knitting, under scarf and hood, huddled up and looking down.  They don’t glance up or over or about.  I’m of course the same when I’m between doors.  At those blistering and miserable moments I’m not concerned with scenery or smells; I’m concerned with thawing my fingertips and eyelashes.  But one small pearl of wisdom I’ve learned up in my sanctuary, watching the poor, huddled masses, yearning to be warm, is that those bitter winter mornings are the perfect hours to stop and look up.

Muggy summer sunsets are swell and soft spring dews lovely, but winter skies are epic.  They are also easily missed, so fixated are we on being anywhere but outside lounging with our eyes lilted poetically skyward.  Try it on some clear day, preferably close to sunrise or sunset.  Bundle up and find one wide view, sprinkle with mountain scenery to taste.  You need only a cursory dose of luck too, since your quarry is not rare.   You’ll be set to find nature’s own smoke-and-mirrors light show.

Sun Pillar

The winter sky is full of magic moments: blazing golden columns spearing the sun, iridescent rainbow parenthesizes, ghostly calm halos.  The secret behind these light shows is ice, or rather ice crystals.  On blue days, up through the troposphere (those bottom 30,000 feet of atmosphere home to us and nearly everything we consciously experience) layers of air stack neatly but invisibly upon one another, mostly undisturbed since the winter days can’t puff enough convective heat to stir them.  Each layer fosters slightly different temperatures, humidities and winds.  Each of these unique climates fosters different species of ice.

Ice is a tremendously variable substance.  Ice crystals form when water vapor, cooled below freezing, comes in contact with a nucleating surface – a speck of dust, a crystal of sea salt, a strand of smog – and instantly freezes.  Depending on the specifics of the day, temperature and humidity chief among them, the ensuing shape can be wildly varied.  Run-of-the-mill snowflakes are a minority in this club, which includes spears, columns, needles, cylinders and plates.  The magic happens when sunlight filters through these miniscule lenses and explodes into reflected and refracted patterns, illuminating the invisible.

Halos are easily the most striking dimension of winter light.  Halos spawn from suspended ice columns, with crystals less than 20 microns in diameter (twice the width of a red blood cell or half that of a human hair).  Light passing through the sides of these crystals refracts, scattering into a smear we can see.  Most halos are 22­o halos, since the distance between the circle and the sun is a calculated 22o.  Less often you might glimpse a wider halo, the 42Oer made from light refracting through the ends of slightly larger columns.

If the angles are not so neatly aligned, sunlight may just bounce off the crystal facets, reflecting back to our eyes in the form of pillars.  The more compact and jumbled the ice crystal layer, the more dynamic and vivid the column, right up to where the sun appears to be retching across the heavens in one terrific golden heave.


More rarely the crystals are uniform six-sided plates.  These crystals are much more broad than thick, and as they slowly fall through the atmosphere wind resistance keeps them parallel to each other and to the ground like tardy leaves on a calm fall day.  Without a jumble of different angles, sunlight cleanly refracts through the crystals and delivers to our eager eyes crisp, icy slivers of rainbows to either side of the sun.  These cupping rainbow parenthesis are called perihelion, or less snobbishly, sundogs.  Because the crystals are to our eye nearly edge-on in orientation, the refracted light comes through strongest at the corners instead of a full halo.

Even the rarest of these dazzlers is a common winter show.  An easy evening can be made watching that cold yellow yoke fall behind the Adirondacks, bursting with columns, ringed in halo, and dimpled with colorful sundogs.  Not to mention the glories, red suns, green flashes, tangent arcs, cirrus ripples…they’re there.  Waiting.  We just need to stop the feet, rub the fingers together, drop the hood and look up.