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Spiderweb (overview). Backlight [1]
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According to the laws of physics, rainbows caused by sunlight always
appear in the section of sky directly opposite the sun [2]. Here I show
that spiderwebs violate this rule by pictures of spiderwebs with backlight
resulting in rainbow-like colors as well.
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Kruisspin / Garden Cross Spider / Araneus diadematus
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Detail. length ~ 1 cm / 0,4 inches
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Straight white lines demarcate a sector of the spiderweb circle that
lights up selectively. The rest is faintly visible and colorless. The
lines meet at the center of the web, and seem to point towards
the sun.
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detail of previous picture. Click to enlarge.
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So the part of the spider web circle that lights up seems to be a segment
which points to the sun [3]. Furthermore, as shown in the previous blog,
the threads of the web consist of many small segments with different
colors. Contrary to the previous blog, these pictures are taken towards
the sun. The fact that colors are seen at all contradict the physical
rules for the formation of a rainbow by the sun. A possible explanation
could be that the spider web threads are not made up of water droplets but
of proteins...
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Garden Cross Spider This little spider had nothing to eat
for a week. Finally she caught a fly! Enjoy your meal!
Note the difference in size!
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An adult Garden Cross Spider built its web on the window of the barn
door. Fortunately we could still use the door! By the
way: this location is perfect to investigate the effect
of different directions of the sunlight because you can move
the door without damaging the web! Addtionally you can
photograph the web from both directions!
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Notes
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The main light source, the sun, is behind the spider, facing the
camera and photographer. Note: in Dutch this is called 'een tegenlicht
opname'.
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Thanks Rolie Barth and Matt Young for pointing this out. See for
example wikipedia article
Rainbow.
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However, I did not investigate this effect systematically!
Previous blogs
Links
Read more...
Yoy might like this one:
ReplyDeletehttps://www.youtube.com/watch?v=lLHgN1szKtI
"Spiderweb colorations"
Hi, thanks for the link. I think I have seen this video. His pictures are very good.
ReplyDeleteI can no longer remember if he paid attention to which direction the sun was coming from: backlight or something else...
ReplyDeletehttps://naturalhistory.si.edu/explore/collections/geogallery/10002820
ReplyDelete