The rain had passed as quickly as it arrived.
For several minutes it had drummed against the leaves, run from the branches and turned the woodland path the colour of strong tea. Now sunlight was beginning to find its way back through the canopy.
Wayne stepped out from beneath the old oak and looked up.
Drops clung to the leaves above him. Every so often, one gathered enough weight to fall, striking another leaf on its way down before disappearing into the undergrowth.
Orion emerged from the trees behind him. Small beads of water covered his shoulders and the clear panels at the sides of his head.
“You’re dripping,” Wayne said.
“So are you.”
Wayne looked down at his wet jacket.
“Fair enough.”
They carried on down the path together.
The woodland gradually thinned. Somewhere beyond the trees, the river announced itself—not loudly, but with the steady sound of water continuing on its way.
They reached the bank near the old willow. Rain still slipped from its narrow leaves, making small circles on the surface below. The bench beneath it was wet, so Wayne remained standing.
Across the river, the last of the shower was moving towards the village. Grey rain softened the hedgerows and rooftops until they looked as though someone had rubbed a thumb across a pencil drawing.
Behind them, the sun broke through.
Colour appeared over the water.
At first it was only a faint red curve against the cloud. Then orange, yellow, green and blue gathered beneath it. Within moments, a rainbow stretched from somewhere behind the trees on one side of the river to the fields beyond the village on the other.
Wayne watched without speaking.
One end appeared to reach the ground beside the old footbridge. The other disappeared behind a distant chimney.
“When I was little, I thought you could reach the end of one,” he said.
“Did you try?”
“Once. It kept getting away.”
“What did you expect to find?”
“I wasn’t sure. That was why I wanted to go.”
The lower part of the bow was already thinning against the fields.
Wayne nodded towards the bridge.
“Let’s see if it still looks as though it ends there when we get closer.”
“It will not have a fixed ending on the ground.”
“You can tell me why on the way.”
They began following the river.
The path kept close to the water before wandering briefly into the trees. Wet grass brushed Wayne’s boots. The air smelled of damp soil, bark and leaves warmed by returning sunlight.
When the path returned to the bank, the rainbow was still ahead of them, although it was not as bright as it had been beneath the willow.
“If you didn’t know what caused that,” Wayne said, “you could believe almost anything.”
“There have been many ways of understanding it.”
“Such as?”
“In ancient Greek tradition, Iris was associated with the rainbow and carried messages for the gods. In the medieval Icelandic Prose Edda, Bifröst is described as a bridge between Earth and heaven—something people might call the rainbow.”
Wayne looked at the band of colour rising from beside the bridge.
“I can see why they made a road out of it.”
“Those stories had religious and cultural meanings of their own. They were not simply early guesses about refraction.”
“Fair point.”
They walked on.
The bridge was not far now. Wayne kept glancing towards the place where colour seemed to meet the bank, as though looking away might give it a chance to leave.
“So how does it form?” he asked.
“The Sun needs to be behind the observer, with water droplets ahead. Sunlight changes direction when it enters a droplet. Some of it reflects from the inside, then changes direction again as it leaves. The colours emerge at slightly different angles.”
“Millions of tiny prisms?”
“Not exactly prisms, but that is a useful first picture.”
Wayne turned his head enough to catch the brightness of the Sun through the trees behind them, then faced the rain again.
“Sun behind. Water in front.”
“Yes.”
The rainbow had paled another shade.
Wayne quickened his pace. Not enough to turn the walk into a race, but enough for Orion to notice and match him.
They reached the old footbridge. Its timber boards had darkened in the rain, and the iron railings shone where water rested upon them.
Wayne stopped halfway across.
The river moved beneath him, carrying small twigs and leaves between the stones. From the bridge, the rainbow no longer seemed to come down beside the near bank. Its lowest visible colour now lay beyond the wet willow and in front of the fields.
“It’s shifted,” he said.
“Your position has shifted.”
“Can we actually test that?”
The amber pattern behind Orion’s head panels moved steadily.
“Line part of the bow up with a fixed object. Then move sideways and compare the alignment.”
Wayne looked towards the distant chimney.
“That?”
“It may be too far away for a few steps to produce an obvious change. Use something nearer.”
Wayne chose a fork high in the wet willow on the near bank. From a join between two boards, the outside edge of the rainbow appeared to pass directly through it.
He placed the toe of his boot against the join, leaned back slightly and checked the line again.
“Red edge through the fork.”
Then he moved eight boards along the bridge.
The fork now stood well to the right of the colour. The bow seemed to come down beyond the willow instead. Wayne returned to the join. The old alignment was almost restored, though the rainbow had become fainter while he tested it.
“It moved across the tree.”
“The alignment changed because you moved. A rainbow is light reaching an observer at particular angles. From your new position, the light reaching you came from a slightly different collection of droplets.”
Wayne looked from the tree to the fields.
“So it didn’t slide along the riverbank.”
“No. There is no fixed object there sliding across the fields.”
“And the test?”
“The droplets are moving and the bow is fading, so this is not a precise measurement. But the change against a nearby tree is large enough to observe.”
Wayne stepped back beside Orion.
“Are you seeing the same rainbow as me?”
“Not precisely. I am in a different position, so light reaches my sensors from slightly different droplets. We are observing the same shower and the same optical process, but not exactly the same rays of light.”
Wayne rested his hands on the wet railing.
“So I can honestly say it looked as though the rainbow ended by the bridge.”
“Yes.”
“But not that there was an end sitting here waiting for me.”
“Correct.”
For a while they watched from their separate places.
A kingfisher flashed along the bank, startlingly blue against the wet greenery. It vanished around the bend before Wayne could properly point it out.
Orion had seen it too.
Neither of them tried to follow.
“Knowing all that hasn’t spoiled it,” Wayne said.
The rainbow stood a little longer over the river. Wayne could still see why one tradition had given it a messenger and another a bridge. The stories were not instructions for finding its position. They carried other things across it.
The rain cloud moved beyond the village. Sunlight spread across the fields, and the colours weakened until parts of the bow were difficult to separate from the brightening sky.
Then it was gone.
There was no sudden ending. The rainbow simply returned to the light, the water and the air from which it had appeared.
Wayne looked at the empty stretch of sky.
“It was still worth stopping for.”
Orion looked towards the clearing weather.
“Yes.”
They left the bridge and continued towards the village.
The path rose gently from the river and passed between hedgerows shining with rain. Ahead, chimney smoke climbed into the clearing sky. A church bell marked the hour, although neither Wayne nor Orion was in a hurry to count it.
Outside the bakery, a man in a white apron had stopped sweeping water from the doorway. He was looking towards the place where the rainbow had been.
For several seconds he stood completely still.
Then he returned to his broom.
Wayne glanced back once more. The river remained beneath the bridge, flowing through patches of sunlight and shadow as though nothing unusual had happened.
“So we know how it formed,” he said.
“Yes.”
Wayne put his hands in his pockets.
“I’m not sure that tells us everything it was.”