When you’re on a rural highway late at night or in the morning after midnight, often there are no streetlamps, so all you can see is what’s in the unevenly illuminated wedge of your bike headlight, which, if it’s a generator light (mine is), gets brighter when you’re descending and dims on the climbs. The beam mostly illuminates the road immediately in front of you, and shades down to grays and beiges after that, and beyond that is black, with the occasional bright distant dot of a reflective highway sign.
In the few inches right in front of your headlight, rain is a scattered jumble of bright slivers. If your headlight isn’t at its brightest, the slivers will have dark dashes on them as each drop passes through a beam blinking on and off too fast to be seen when there are no raindrops. That’s how modern bike headlights “dim”; they don’t actually get dimmer like old incandescents; they just don’t illuminate as often. If you have a battery-powered light, the lengths of the dark dashes on the bright slivers change as you click to different brightness settings.
In heavy fog or mist, there are many more bright slivers, smaller, and a short bright cone of haze, and then the beam brushes the top of your front tire, and then the road, with the shadow from that tire, and then there are shadows and refractions from the water on the headlight lens, the dark wiggly snakes of road patches, and the glitter, which is sometimes glass or wire or other puncturing crap and sometimes the chip part of chipseal paving.
If you can see your own shadow, and there are no streetlamps, that means the first car in a while has just crested a rise or turned onto the highway some ways behind you. Your shadow will gradually get larger, and gain density and sharpness, and move to your right as the car approaches in the lane to your left. The road surface will become better illuminated, and pebbles and other junk outside your little beam will stand out against the relief of their own shadows; if you’re experienced at this, you’ll take the opportunity to look farther ahead for potholes or puddles.
All the shadows—yours, the bike’s, the gravel’s, the beer bottle’s—move together, their size changing and rotation accelerating as the car approaches. By now, you can hear the hiss and swish of the car tires and its displacement of the air. Maybe its engine, too, but that won’t necessarily become primary at any point.
A few seconds before the shadows all rotate to three o’clock and vanish, on a forested highway that curves left, you will see your giant shadow on the trees in front of you: You, your helmet, the true shape of your body, your bike. You, pedaling, 10′ tall, then 20′, on gray-green trees. The perspective rotates slightly as the car closes the distance, as though the 40′ cyclist’s labor exists on a turntable, and the dark giant and his 50′ bike and pedaling legs slide sideways to the right, along the trees, and vanish.
Red taillights pass you, but what you’re watching is what the car’s headlights can tell you about the road ahead, until the road curves or crests, and then the headlights aren’t telling you anything, but the taillights are still red dots, which vanish soon enough too, and you’re listening to rain patter on leaves, the wet whir of your tires, some rhythmic mechanical noise you’ve been occupying yourself trying to identify, and if you’re lucky, the gorgeous echoes of a wood thrush.