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Tom Mazanec
2018-Apr-06, 02:26 AM
I read that spider threads are only a few microns wide.
I have relatively poor eyes, yet I can see the threads. How can I see something smaller than a protozoan?

grant hutchison
2018-Apr-06, 08:37 AM
Well, spider webs are covered in adhesive, which makes the threads easy to see. You'll often see an apparently empty centre to a spider web when it's first spun, because the central, non-sticky area is much finer than the rest of the web - but it tends to become visible as the day wears on and the web gets dirtier.

Parachute threads, as used by young spiders to drift through the air, are pretty much invisible unless the light catches them from behind. In that orientation, you have a reflective and refractive cylinder scattering light in the forward direction in a fairly narrow angular range. And it does two things to attract our attention - it sparkles, and it's linear.
Here's a photo of parachute threads caught on fence wire I took last year - the sun is just out of view at the top of frame. It's much more visible in the photo than it was in real life, since even the very short exposure time produces a little smear of light as the silk waves in the wind.
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Grant Hutchison

glappkaeft
2018-Apr-06, 05:16 PM
I read that spider threads are only a few microns wide.
I have relatively poor eyes, yet I can see the threads. How can I see something smaller than a protozoan?

It's the same reason you can see stars. There is a difference between resolving and seeing.