It started with something I glimpsed out of the corner of my eye. At first, in as much as it registered with me, I thought it was a faint contrail. After all, as I was pulling into the car park beside Lough Neagh at Antrim, I was very close to Aldergrove airport. But, as I became slightly more aware of it, it suddenly struck me that it was unusually curved for a contrail. But it didn't register as anything more than that. Not, that is, until I got out of the car.

For the view that had been limited by the edges of the car windows suddenly and dramatically opened up before me as I stepped out. This 'contrail' was indeed unusually curved. Looped, in fact, in that classic and instantly recognisable shape. For this was no remnant of a passing aircraft. This was a rainbow. At night. In the dark. 

Now I'm no expert in physics by any means, but I know enough about this meteorological feature to be aware that it is formed as light is refracted through droplets of water in the sky. And so you need both rain and light. Okay, I thought, so there's a large cumulus congestus cloud hanging ominously over the sky to the west of the Lough. So that's the rain sorted. But light? At night? In the dark? 

Only it wasn't entirely dark, you see. For, behind me, high in the sky, was a full moon, casting its eerie grey light all over the landscape - and the sky. So this was the light source. And those two things were combining together to produce a feature I never knew could exist - a rainbow a night.

I like to think of it as the shy rainbow. When all other rainbows appear during the day, demonstrating slight narcissistic tendencies as they show off their glorious displays for all to see, this one is much more discrete, only sneaking out when it thinks no one is watching.

But I caught a glimpse that night, and now I share it with you. So, next time you catch something resembling a contrail at night out of the corner of your eye, look again. It might just be our shy rainbow, putting on a more humble - yet still glorious - display for those who care to notice.

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