Extropia’s Curious Science: The Baghdad Battery

EXTROPIA’S CURIOUS SCIENCE: THE BAGHDAD BATTERY

When was the battery first invented?

Were I to hazard a guess, I would suppose that batteries were invented at some point in the 19th century, a time when Michael Faraday demonstrated the first prototype electric motor and James Clerk Maxwell wrote down the equations unifying electricity and magnetism. I certainly would not think that batteries had been around for a thousand years before the electrical age began.

But, a curious artefact at the National Museum of Baghdad might just prove me wrong. This object is said to have been discovered by a German archaeologist called Wilhelm Kong. According to some (accounts vary) in 1937 he was digging around a grave at Khujut Rabu near Baghdad when he uncovered an earthenware pot. The pot was not empty; it contained an iron rod encased in a copper cylinder, all sealed with asphalt. Kong believed he had discovered an ancient battery and he hypothesised that if several such objects were strung together, it would be possible to electroplate precious objects.

(An artist’s impression of the Baghdad battery. Image from Wikimedia commons)

This hypothesis was rejected by his peers and the discovery was largely forgotten as the world plunged into WWII. But after the war, further investigations revealed that some sort of acidic substance had corroded the object. This inspired an American engineer called Willard Gray to fill a replica jar with grape juice. He was able to generate up to two volts of electric potential. Furthermore, in the 1970s a German team successfully electroplated a thin layer of silver using a string of replicas.

Thanks to experiments like these, what was once a rejected idea is now a generally accepted theory. The consensus is that this really is a battery, which is pretty amazing if you think about it. This archeological discovery is thought to date from the Sassanian Period, approximately 225-640 BCE. So hundreds of years before Christ was born, our ancestors were making batteries.

The question is: Why? Nobody really knows. As I said, some guess they were used for electroplating. Others have suggested that they were hidden inside effigies so as to provide a mysterious tingle should anyone touch the sacred statue. Whatever their intended use, these batteries would have been very valuable, since many are needed to provide even a small amount of charge.

Sadly, following the Iraq war, several thousand artefacts went missing from the National Museum of Baghdad, and the Baghdad battery was among them. This just goes to show that while in some ways we have advanced (our batteries are a vast improvement over this ancient version) in other ways we are not so civilised.

REFERENCES

“Far Out” by Mark Pilkington