This simple circuit can detect the invisible fields of voltage which surround all electrified objects. It acts as an electronic `electroscope.` Regular foil-leaf electroscopes deal with electrostatic potentials in the range of many hundreds or thousands of volts. The above device can detect one volt. Its sensitivity is ridiculously high. Since `static electricity` in our environment is actually a matter of high voltage, this device can sense those high-voltage electrically charged objects at a great distance. On a low-humidity day and with a 1/2 meter antenna wire, its little LED-light will respond strongly when someone combs their hair at a distance of five meters or more.
If a metal object is lifted up upon a non-conductive support and touched against the sensor wire, the sensor can detect whether that object has an electrostatic potential of as little as one volt!
Note: I use the term "electrification" rather than "charging", in order to avoid confusion between electric charge and net-charge. "Charge" is the stuff on the negative electrons and positive protons, while "net-charge" is the imbalance between positive and negative particles which appears on everyday objects. A avoid saying that everyday objects become electrically charged. After all, their atoms are always full of charges. Instead they become "electrified" whenever their pre-existing + and - charges are not equal.