Draining the Baghdad Battery

by Brian Dunning
September 11, 2018

There's long been a tendency among alternative historians to think that, for some reason, technology has actually been going backwards throughout history; that whatever we know now, the ancients knew better. One of the figureheads of this school of thought is the Baghdad Battery, a clay pot from Iraq that some believe was used as a battery, and thus the ancient people were actually centuries ahead of their European counterparts. Today we're going to discuss not only the details of what makes this claim demonstrably true or false, but also the larger phenomenon of broken thought processes that leads so many to embrace such beliefs as this one.

Let's have a look at the actual artifact. It's a fired terra cotta pot, quite small, only about 14cm high and 8cm across, narrow at the bottom and reaching its widest point about two thirds of the way up. The opening at the top is 3cm across, but it's also broken off at that point, so originally it was likely a bit taller. Around that broken rim are remnants of asphalt, collected from tar pits, which would indicate that the jar's top had originally been sealed. Inside the jar is a hollow tube made from a thin sheet of copper rolled into a cylinder, 9.5cm long and 2.5cm wide, with a circular copper plate closing its bottom sealed with asphalt. The seam along the side of the tube is soldered with lead/tin alloy. Inside the tube is an iron pin about 8cm long, completely rusted. At its top is a thick asphalt plug that fits the tube, such that when you placed the pin inside the tube it's sealed, with the pin running down the center of the tube, and protruding about 1cm beyond the top of the plug. For the entirety of its known lifetime, the Baghdad Battery was at the National Museum of Iraq in Baghdad, but it was unfortunately lost in 2003 when the museum was looted. Its status remains unknown.

The artifact became known to the archaeological community in 1938. Wilhelm König was an assistant at the museum, an artist by trade, working in the archaeology department. Later he took over and became the museum's director. He published a paper in the German language journal Research and Progress titled "A galvanic element from the Parthian period?" in which he speculated that the jar could have been a simple battery used for electroplating pieces of art. The Parthian period refers to the Parthian empire of 150 BCE - 223 CE in Khujut Rabu, just southeast of Baghdad.

Unfortunately König did not give precise information about the jar's origin, but we do have a pretty good idea. It's not clear whether he obtained it from the museum's archives or from its origins at a 1936 dig in Khujut Rabu, or even whether he was personally at the dig. It's also not clear how many such jars were recovered, but the Baghdad Battery is similar to other jars from the region and there's no special mystery about them. It has not been precisely dated, but from its context, modern archaeologists agree that it comes from sometime during the Parthian period or the following period of the Sasanian empire. Thus it's in the range of 1300 to 2200 years old, centuries before the first batteries were conceived around 1800.

Also in the Museum's collection are (or were) other similar copper cylinders. Many of them contain fragments of long-decomposed papyrus, indicating that they were used to contain and protect scrolls. A scroll would be wrapped around a wood or iron pin, then slipped inside a copper tube for storage. König did note this in his paper, citing a number of copper cylinders containing scroll fragments from other digs at other cities. Some used glass flasks instead of copper tubes, but what's clear was that König had plenty of information at his disposal hinting at the true use for these cylinders. Nevertheless, for reasons that aren't clear, König supposed that this one particular jar might have been used as a battery instead, and wrote his paper from that perspective. He built his own versions and successfully got small voltages from them by adding terminals, wiring — and most importantly — an electrolyte fluid. However, World War II was on the horizon, and little attention was given to his paper suggesting an alternate use for the scroll containers.

It remained in relative obscurity until another author who wrote in the German language — a certain Erich von Däniken — gave it the briefest of mentions in his 1968 book Chariots of the Gods?, showing a single photo of the iron pin and saying that it had "been identified as the remains of an electric battery." As we know from history, this book launched a whole genre of ancient astronaut mania, and alternative historians have been building and testing replica Baghdad Batteries ever since. The vast majority of articles written about the artifact have been from the ancient astronaut perspective, copying and pasting from one another, citing each other as authorities and never consulting archaeologists; and the natural result is that the existing body of literature about the Baghdad Battery is inaccurate, contradictory, and highly biased toward an alternative history perspective.

Coaxing a voltage from an object like the Baghdad Battery is quite easy, as a basic battery requires nothing more than ordinary items. All you need are two different types of metal, and if placed in an electrolyte liquid, an electrical current will flow from one piece of metal to the other. Common acidic liquids like the juice of a citrus fruit, wine, or vinegar, will do. A penny and a nickel in a bowl of vinegar will do. Even a potato with a nail and a penny jammed into it will work, as so many of us experimented in grammar school. Even TV's Mythbusters successfully replicated a Baghdad Battery; simple batteries are easy to make out of just about anything.

König's conjecture was that the battery may have been used for electroplating jewelry or bits of art, which is actually not a terrible hypothesis. Gilding was indeed well known in the world during the Parthian period. However, we do know how they did it, and it wasn't König's way. The technique in use was called mercury gilding (or fire gilding). The abbreviated description of this process is that gold or silver dissolved in mercury is applied to the object to be gilded, then heated to volatilize away the mercury, leaving the coating of precious metal on the object. Today it's trivial to verify that this was the method used on a given object, as the gilding still contains significant mercury and other chemical signatures. All gilded objects from the period used this method; none has been found to have been electroplated.

Other authors have come up with other things that the battery could have been used for. One suggestion was that a battery could have been connected to a religious statue, so that when a worshiper touched it, they would receive a sparkling little shock representative of the power of the gods. Another idea is that its mild shock was used for pain relief, perhaps in an early form of electroacupuncture.

However we find that it's relatively easy to dismiss all of the possible uses Parthians may have had for a battery, because we can go back to the jar's properties and quickly determine that it's about the worst thing you could try and use for a battery. Let's look at just three points:

1. If it were used as a battery, it would not last very long at all, and its electrolyte would need to be replaced quite often. However, it is sealed with asphalt, a thermoplastic, which would make it prohibitively inconvenient to refill.
   
   
2. It lacks terminals. Batteries need a positive and a negative terminal that are accessible for connecting wires. If rigged as a battery, this one would have had the terminals under the fluid level and inaccessible beneath a seal.
   
   
3. No conductive wires have ever been found that would indicate the ancients had knowledge of wiring. Without wires, there was no way to get current out of the battery and to the theoretical powered device.

Beyond these points, no followup developments or improvements to the battery have ever been found; which means that if it was indeed a battery, it was totally isolated from any context within the archaeological and historical records, which isn't the way history works. History has no examples of revolutionary inventions being suddenly discarded and struck from the records and from all usage.

However, all these nitpicks about its unsuitability for use as a battery aren't even the main argument against the Baghdad Battery. The best reason to regard it as archaeologists do (as a scroll jar) is that there is no reason to think of it as anything else. Just about everything can be repurposed. You can turn a flower pot upside down and wear it as a helmet. You can drink out of a shoe. You can fill a coconut with circuitry and turn it into a radio. The fact that something can be used as something else does not mean that it was ever intended that way. Writing in Skeptical Inquirer magazine in 1996, chemist and museum conservator Gerhard Eggert wrote:

As is always the case in experimental archaeology, successful experiments alone can show only a supposed ancient technique to be possible, but never its application. For instance, Thor Heyerdahl only showed with his Ra voyage that in principle it is possible to cross the Atlantic in an Egyptian boat. To accept the claim that the Egyptians really did so, one would need archaeological evidence from America.

...and no such evidence exists. Thus, Heyerdahl's voyage, while it made a great cover for National Geographic, did not persuade historians to upend the history of the Americas; just as the proof that people can make batteries out of ancient scroll containers did not persuade historians to overturn the history of science.

There simply is no reason to regard the Baghdad Battery as a battery. It's almost certainly just a scroll jar like any other — of course we can't state that identification definitively, but it's certainly the null hypothesis. The identification of battery is not only inconsistent with the details of its design, but is also radically at odds with historical context. Consider all the many archaeological artifacts from all cultures, all time periods, all parts of the world — everything from armor to art, from machines to medicine — millions of objects of unfathomable descriptions. In all of that, how many objects are container shaped and contain two types of metal? Thousands? Tens of thousands? Must we declare them all to be ancient batteries, or is it possible that the Baghdad Battery is nothing more than an example of wishful thinking from modern enthusiasts of alternative history?

By Brian Dunning
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