The tilt of the planet on its axis at autumn creates our gilded season.

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Now comes our gilded season, as the arrival of autumn brings low, slanting light and that fleeting feeling, knowing the blue skies and gold light will too quickly fade to our long season of gray.

From the back-to-school rhythm lingering long past our school years, to the first plangent honks of geese and tang of wood smoke and burn piles: Who can bear the poignancy of this season?

Then comes the light: thick, plush, gold. It’s not your imagination: The light really is different right now, and changing fast.

Dale Durran, chairman of the Department of Atmospheric Sciences at the University of Washington, explains it all:

The position of the sun in the sky is changing. That, in turn, alters how we perceive color and light. In the height of summer, the sun is as far overhead as it gets. But the sun drops and drops after the summer solstice in June — and the change speeds up at the midpoint toward winter. Right about now.

The seasons are the result of the tilt of our planet on its axis as we orbit the sun. Picture a tennis ball on a pen, with the pen held at a 23.5-degree angle. Now rotate the ball (Earth) on the same angle, fixed around a stationary object (the sun).

The farther from the equator, the more obliquely the sun’s light strikes Earth — that’s the longer, slanted light we are bathed in now, instead of the full-on beams we bask in at high summer.

And the journey will continue in the progression toward winter, taking us into shorter days, with the sun even lower on the horizon.

But not first without this gleaming farewell, through the golden hours of this season.

Add the steam fog rising off Lake Washington and Puget Sound, and these autumn mornings are too pretty to leave for our fluorescent-lit boxes — offices, schools and the like.

The steam fog is the result of autumn’s chill air, arriving in the morning over water still warmed from summer. The temperature difference causes water to evaporate from the surface and recondense as it mixes with the cooler air, in a rising, twining mist. Arctic sea smoke, or steam fog, as it’s called, is the result.

Fall color? That will depend on whether the wind and rain crash the party early, or if nature lets this sweet season linger.

Earlier this week, the spider webs glittered in the morning light, and sunlit, golden afternoons beckoned. Today, rain.

Take a tip from Durran, a master sky-watcher: “Go out,” he said, “and you can appreciate what’s there.”

Lynda V. Mapes: 206-464-2736