Wednesday, 25 June 2014

Colourful linear anomalies

Water flying rodsMost flying rods have appendages, so those that don't are always worth a closer look. In the photo (right) there are some linear anomalies which certainly resemble flying rods but lack the typical appendages. They are also transparent, like tiny imperfect glass cylinders, which is also not typical of rods. The photo is a minute crop from a larger picture showing hundreds of similar objects. While these strange things are clearly in focus, the background, consisting largely of green vegetation, is not. The shutter speed, at 1/320s, is shorter than the 1/50s typical of flying rod photos. So what are they?

Their transparency is, perhaps, the biggest clue. The objects are water droplets. They appear elongated because of their rapid movement while the camera shutter is open. They are not raindrops, however, but spray from an irrigation sprinkler system. Many of the droplets in this section of the photo are near the apex of their trajectory, which is why some are moving almost horizontally. Raindrops would, obviously, tend to have a more vertical trajectory.

So, while these anomalies are not like typical flying rods, they might be mistaken for them. In a photo (below right) taken at the same place around 90s later, the same 'water rods' have taken on an even more unlikely appearance. They are now brightly coloured!

Water rods colourThis colourful effect is caused by sunlight being refracted and internally reflected within the water droplet (see here for a diagram and fuller explanation). The shutter speed this time was 1/250s which, coupled with the more vertical trajectory, probably explains the greater length (compared to the width) of these 'water rods'.

It's possible to see how this anomaly could be viewed as unexplained if the photographer didn't notice the sprinkler at the time of exposure. Indeed, the spray was not that obvious when these particular photos were taken. Of course, a photo covered in such anomalies may suggest rain or a sprinkler. However, if the water droplets only cover a small part of the frame, they might well appear more mysterious.

I've never seen an anomalous photo showing objects like these. But I have often photographed strange things (with known natural explanations) that I've never seen in anomalous photos before. And, in just about every case, I've subsequently seen anomalous photos that matched those I'd taken earlier! So I won't be surprised to come across anomalous photos like these in future.

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