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I once saw a spider hoist himself up 2 stories in a most elegant way. I was sitting outside on the porch and a gentle breeze was blowing. I noticed this shimmer

I once saw a spider hoist himself up 2 stories in a most elegant way. I was sitting outside on the porch and a gentle breeze was blowing. I noticed this shimmering line floating and it went up until it latched unto the roof and then this little creature just floated up from the porch and a few seconds later, was on the roof. It was almost like a dance. I remember being very impressed with that little spider and admiring it.

_Microft 5y ago
Some spiders even use threads as a sort of sail that can carry them around. https://en.wikipedia.org/wiki/Ballooning_(spider) https://en.wikipedia.org/wiki/Ballooning_(spider)
- hermitcrab 5y ago
  I did some amateur research on this years ago. I couldn't understand how a spider can 'fly' with a thread of gossmer, than has no aerodynamic lift. The most likely explantion is that the spider is falling in a rising column of convective air, but (in some cases) the thread allows it to fall slower than the air is rising.
  - ncmncm 5y ago
    Nope! It's electrostatic repulsion.
    - hermitcrab 5y ago
      How does that work when they are 10m+ in the air?
      - ncmncm 5y ago
        The electric field gradient of the earth is 100V/m all the way to the stratosphere. It is why lightning can find and release so much energy.
        hermitcrab 5y ago
        From: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6065530/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6065530/ "ballooning mechanisms are not fully explained by current aerodynamic models. The global atmospheric electric circuit and the resulting atmospheric potential gradient (APG) provide an additional force that has been proposed to explain ballooning" So perhaps a combination of drag and electrostatic force. And, unless the spider can build up a substantial charge on the thread, I am guessing that drag is the more important part.
        ncmncm 5y ago
        The surface of spider thread is such that air blowing across it takes away charge, leaving behind the opposite charge. So, atmospheric drag provides horizontal motion, and electrostatic repulsion provides vertical motion. Once the spider is aloft, air motion relative to it falls off, and the charge begins to leak away. Eventually it descends.
        hermitcrab 5y ago
        The rising convective air dragging along a vertical thread also provides some lift. I wonder if anyone has tried to lift a spider using electrostatic forces alone and what voltage that would need? You'd think it wouldn't that hard an experiment to do.

_Microft 5y ago

Some spiders even use threads as a sort of sail that can carry them around. https://en.wikipedia.org/wiki/Ballooning_(spider) https://en.wikipedia.org/wiki/Ballooning_(spider)

hermitcrab 5y ago
I did some amateur research on this years ago. I couldn't understand how a spider can 'fly' with a thread of gossmer, than has no aerodynamic lift. The most likely explantion is that the spider is falling in a rising column of convective air, but (in some cases) the thread allows it to fall slower than the air is rising.
- ncmncm 5y ago
  Nope! It's electrostatic repulsion.
  - hermitcrab 5y ago
    How does that work when they are 10m+ in the air?
    - ncmncm 5y ago
      The electric field gradient of the earth is 100V/m all the way to the stratosphere. It is why lightning can find and release so much energy.
      - hermitcrab 5y ago
        From: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6065530/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6065530/ "ballooning mechanisms are not fully explained by current aerodynamic models. The global atmospheric electric circuit and the resulting atmospheric potential gradient (APG) provide an additional force that has been proposed to explain ballooning" So perhaps a combination of drag and electrostatic force. And, unless the spider can build up a substantial charge on the thread, I am guessing that drag is the more important part.
        ncmncm 5y ago
        The surface of spider thread is such that air blowing across it takes away charge, leaving behind the opposite charge. So, atmospheric drag provides horizontal motion, and electrostatic repulsion provides vertical motion. Once the spider is aloft, air motion relative to it falls off, and the charge begins to leak away. Eventually it descends.
        hermitcrab 5y ago
        The rising convective air dragging along a vertical thread also provides some lift. I wonder if anyone has tried to lift a spider using electrostatic forces alone and what voltage that would need? You'd think it wouldn't that hard an experiment to do.