Pre-historic people valued and traded amber, a gem-like material that is petrified tree sap. Surely more than once a person would have rubbed amber on his or her fur clothing and noticed that fur was attracted to the stone. Perhaps she rubbed it hard enough to produce sparks. The Greek philosopher Thales of Miletus wrote about these effects around 600 B.C.E.

But it wasn’t until 1600 C.E., some 2,200 years later, that William Gilbert (1544-1603), an English physician, named this effect “electricity” after the Greek name for amber: “elektron.” Gilbert showed that sulfur, wax, glass, and other materials behaved the same way as amber. He invented the first instrument to detect what we now call the electrical charge on objects called a versorium, a pointer that was attracted to charged object. Gilbert also discovered that a heated body lost its charge and that moisture prevented the charging of all bodies.

In 1729, the English scientist Stephen Gray (1666-1736) determined that charge, or what he called the “electric virtue,” could be transmitted over long distances by metals, objects that couldn’t be charged.