Fence Iridescence by Dan Gilder of Manchester, England. ©Dan Gilder, shown with permission.

Dan imaged these delicate iridescent tendrils curling up from a sunlit fence top last Sunday morning 7th December. There had been an overnight frost and the sun was warming the ice crystals on the fence. Some ice was probably subliming directly to water vapour, other crystals had melted and the water was evaporating.

Once mixed and cooled by the cold air, the water vapour condensed back into myriad tiny droplets each of which individually diffracted the sun's light to form the iridescent colours.

Optical effects are everywhere.