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Monday, July 31, 2017

Shifting sun

This might be the last post about colors and spider silk (at least for a while).  The point where the sun rises along the eastern horizon has shifted to the south.  The sun's rays no longer strike the corner of our backyard (where I had been photographing the webs) in the same way .

Here's the last set of images taken on 22 July 2017.  The scene is a little different.  Instead of an orb web, this was a group of strands against a tree trunk, with some overlapping.

Happy August!


John W. Wall said...

I'm curious to know if this is like a spectrograph that tells us something about the physical/chemical make-up of the strands. Or is it more like a prism bending light at all those different wavelengths, and if so, what explains all those rings and their widths?

Jackie Sones said...

Hi, John! I wish I knew the answers to your questions. I've sent the photos around a bit, but I'm not sure if anyone has truly figured out what causes these color patterns. One person suggested that it might have to do with the proteins that make up the silk strands.

The patterning -- the width of the bands, and the way the bands alternate is consistent along the strand. For example, I can return to the same spot over and over and find the same pattern. But the colors of the stripes themselves can change -- I can see them change when I change my own position relative to the strand, e.g., rotating around to look at the strand from a different angle, and sometimes when I haven't changed position, but something's going on with the sun or with the strand itself (the breeze or the spider is moving it).

Sometimes the colors are more muted than what I've shown so far. I'm wondering if it has to do with the age of the silk, but I'm guessing there are additional explanations.

It's a fun phenomenon to explore -- I'm amazed by the colors themselves and the diversity of combinations -- but I sure do wish there was a good description of how these colors are produced.