E-Archive


Vol. 22
November Issue
Year 2021
BACK

Off the Beaten Track


in Vol. 22 - November Issue - Year 2021
A Shocking Discovery



The E. voltai eel discharges 860 volts

The sick woman sat on a wooden stool next to a large basin of water. Something could be seen moving in the murky liquid. With a slow and grave gesture, the high priest took the woman’s left arm and raised it over the surface of the water before letting it drop. Two seconds later, the woman screamed and rolled to the ground.

*****

The discovery of electricity was a long process spanning several millennia. In ancient times it was known that some types of fish could generate shocks when touched. Egyptian scrolls from 2750 BC attributed magical powers to these fish, calling them “Thunderers of the Nile”. The ancient Egyptians used the Nile catfish to treat headaches and nerve pain, a practice that remained in medical use until the late 1600s. Ancient Arabic, Greek and Roman naturalists described electric fish found in the waters of the eastern Mediterranean. Scribonius Largus, court physician to the Roman emperor Claudius, and the Roman historian Pliny the Elder detailed the numbing effect of electric shocks delivered by catfish and rays.

The Greek philosopher Thales of Miletus discovered electrostatic electricity about 2,600 years ago. He observed that by rubbing amber, a fossilized tree resin, with animal fur, it was possible to attract dried grass. However, none of these observations and experiments led to a unifying theory of the physical phenomenon and electricity remained a simple intellectual curiosity for millennia.

The characteristics of magnets were comprehensively and carefully examined in a 1269 treatise entitled Epistola de Magnete by the French scholar Pierre de Maricourt. In his 1600 book entitled De Magnete, the English physicist William Gilbert studied the relationship between electricity and magnetism. He distinguished between the lodestone effect and static electricity produced by rubbing amber, coining the New Latin word electricus (meaning "of amber" or "like amber") from elektron, the Greek word for "amber". This neologism led to the words “electric” and “electricity”, first used in Thomas Browne's Pseudodoxia Epidemica in 1646.

In the mid-1700s, the American inventor Benjamin Franklin hypothesized that lighting was a ‘massive electric spark’ and proposed an experiment with an elevated rod to “draw down the electric fire” from the cloud. Upon reading Franklin’s theories, in May 1752 Frenchman Thomas Francois D’Alimbard successfully attracted the “electric fluid” (lightning) by using a 50-foot-long vertical rod. His experiment was replicated by Englishman John Canton two months later and by Russian chemist Mikhail Lomonosov shortly thereafter. Unaware of these developments in Europe, Franklin conducted his own version of the experiment in July 1752 with the famous kite and key episode.

A flurry of new research ensued when news of these experiments spread through the scientific community. The Italian doctor Luigi Galvani found that a frog’s legs would twitch when touching two different kinds of metals. He demonstrated that neurons passed signals to the muscles by electricity and published his findings in 1791, thus creating the field of bioelectromagnetics. Based on these findings, his contemporary Alessandro Volta concluded that a kind of electrical potential exists between the two metal plates, causing electrical charge to flow through the frog’s leg. His intuition led him to invent the first modern battery by stacking alternating layers of zinc and copper (the voltaic pile). In his honor, one of the properties of electricity, electrical potential (voltage), is named after Alessandro Volta.

With various experiments and studies in 1820-1821, Danish physicist and chemist Hans Christian Ørsted and French mathematicians and physicists A.M. Ampère and François Arago confirmed the relationship between electricity and magnetism. Ørsted's discovery that a magnetic field existed around all sides of a wire carrying an electric current led to Michael Faraday's invention of the electric motor in 1821. Ampère is considered the father of electrodynamics and the basic unit of electric current, the “ampere” or “amp”, is named after him. In 1826, the German mathematician and physicist Georg Ohm used Volta’s battery to define the relationship between power, voltage, current and resistance, leading to the creation of “Ohm’s Law”. The basic unit for resistance, the ohm, is named after him. In 1864, Scottish physicist James Maxwell wrote a set of equations that explained the relationship between various characteristics of electromagnetic waves, leading to Maxwell’s Laws.

And what about the electric fish? During a scientific expedition to the Amazon River in 2014, American researcher William Crampton was studying two species of electric eels recently discovered. While measuring the electrical output of a 1.21-meter specimen of E. voltai, his instruments read a whopping 860 volts!




Author: Giovanni Gregorat

By Giovanni Gregorat, Contributing Editor MFN