Why do streetlights mke the sky glow?

12 August 2007

Question

I’ve been watching meteors for the past week, and I live in the country with very little light pollution. However I can see the glow of a nearby town, despite the town being over the horizon and even when the night is crystal clear, so there are no clouds for the light to reflect off. What is the light reflecting off to get to me?

Answer

The light must be reflecting of something, and on a very dry night this could be dust. However in the UK the most likely candidate is water vapour - not dense enough see normally, more like a very light mist. This mist can form when moist air cools, and water condenses into a vapour, and is very likely the reason why you can see the town's lights on a clear night.

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