Like spiders fly even quietly

Amazing physics hides behind many everyday objects. I felt for many years Hans Joachim Schlichting He discusses these phenomena and explains them in his column for readers of the “Scientific Spectrum”. Schlichting is Professor of Educational Physics and worked at the University of Münster until his retirement.

Such problems can be eliminated if one takes into account the effects of the so-called potential gradient of the atmosphere. It has to do with the differences in charge between the atmosphere and the Earth: the ionosphere, more than 70 kilometers in height, is mostly positively charged, while the Earth’s surface is negative. The difference affects the entire area between them. The undisturbed atmosphere above the Earth is positively charged compared to this, such that there is an electric potential between a point on Earth and a point in the air above it. After all, it can be about 100 volts per meter. However, the strength of the impact varies and largely depends on weather conditions.

Good feeling of electric fields

The mutual repulsion of the threads released by the spider shows that the silk fibers are also electrically charged. So there is inevitably an interaction between it and the air field, which causes motion. But how can a spider know in advance whether the forces are strong enough to hold it and thread it? To do this, you must perceive electric fields and judge them according to their strength. At least some insects are capable of this It has been known for several years.

2018 Erica Morley and Daniel Robert from the University of Bristol have studied how spiders interact with fields. In laboratory experiments, they exposed parachute spiders (Linyphiidae) to electric fields that strongly corresponded to those in the atmosphere under different atmospheric conditions. In fact, the spiders responded with apparent preparations for flight. Flying animals gain height or lose altitude as the fields turn on and off. Thus, not only the aerodynamic lift is responsible for the ascent, but also the electrical interaction between animals and external fields should play a role. Certain movements of certain hairs on the surface of the animal’s body in response to electric fields indicate that the so-called Trichobothria enables spiders to perceive fields.