Baghdad Battery
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The Baghdad Battery is the common name for a number of artifacts apparently discovered in the village of Khuyut Rabbou'a (near Baghdad, Iraq) in 1936. These artifacts came to wider attention in 1938, when Wilhelm König, the German director of the National Museum of Iraq, found the objects in the museum's collections, and (in 1940, having returned to Berlin due to illness) published a paper speculating that they may have been galvanic cells, perhaps used for electroplating gold onto silver objects.
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Description
The artifacts consist of ~130 mm (~5 inch) long clay jars containing a copper cylinder made of a rolled up copper sheet, capped at the bottom, in turn covering and protecting an iron rod. The iron rods are isolated from the copper by asphalt plugs or stoppers, and the cylinders fairly neatly fit the necks of the jars, which bulge toward the middle. The copper cylinders are not watertight, so that if the jars were filled with a liquid, this would surround the iron rod as well. The artifacts had been exposed to the weather and had suffered corrosion, although fairly mild given the presence of an electrochemical couple (which may lend evidence against an ancient date).
Dating
König thought the objects might be Parthian (between 250 BC and 224 AD) because the village where they were excavated was Parthian. However according to Dr. St John Simpson of the Near Eastern department of the British Museum their original excavation and context were not well recorded (see stratigraphy), so evidence for this date range is very weak. Furthermore, the style of the pottery (see typology) is Sassanian (224-640 AD), so they are probably much more recent than König thought.
Most of the components of the objects are not particularly amenable to advanced dating methods. The ceramic pots could be analysed by thermoluminescence dating, but this has apparently not yet been done; in any case, it would only date the firing of the pots, which is not necessarily the same as when the complete artifact was assembled. Another possibility would be ion diffusion analysis, which could indicate how long the objects were buried.
Speculations on function
Electrical
Copper and iron form an electrochemical couple, so that in the presence of any electrolyte, an electric potential (voltage) will be produced. König had observed a number of very fine silver objects from ancient Iraq which were plated with very thin layers of gold, and speculated that they were electroplated using batteries of these "cells". After the Second World War, Willard Gray demonstrated current production by a reconstruction of the inferred battery design when filled with grape juice. W. Jansen experimented wirh benzoquinone (some beetles produce quinones) and vinegar in a cell and got satisfactory performance.
However, even among those who believe the artifacts were in fact electrical devices, electroplating as a use is not well regarded today. The gilded objects which König thought might be electroplated are now believed to have been fire-gilded (with mercury). Reproduction experiments of electroplating by Dr. Arne Eggebrecht consumed "many" reproduction cells to achieve a plated layer just one micrometre thick. Other scientists noted that Dr. Eggebrecht used a more efficient, modern electrolyte; using only vinegar, the "battery" is very feeble.
An alternative but still electrical explanation was offered by Paul Keyser. It was suggested that a priest or healer, using an iron spatula to compound a vinegar based potion in a copper vessel, may have felt an electrical tingle, and used the phenomenon either for electro-acupuncture, or to amaze supplicants by electrifying a metal statue.
Nonelectrical
Skeptical archaeologists see the electrical experiments as embodying a key problem with experimental archaeology; such experiments can only show that something was physically possible, they say nothing about whether it actually occurred. Further, there are many difficulties with the interpretation of these artefacts as galvanic cells:
- the asphalt completely covers the copper cylinder, electrically insulating it, so no current can be drawn without modifying the design;
- there are not any wires or conductors, nor any accepted electrical equipment associated, with them;
- an asphalt seal, being thermoplastic, is excellent for forming a hermetic seal for long term storage. It would be extremely inconvenient however for a galvanic cell, which would require frequent topping up of the electrolyte (if they were intended for extended use).
Some observe that the artifacts strongly resemble another type of object with a known purpose – namely, storage vessels for sacred scrolls from nearby Seleucia. Those vessels do not have the outermost clay jar, but are otherwise almost identical. Since it is claimed these vessels were exposed to the elements, it would not be at all surprising if any papyrus or parchment inside had completely rotted away, perhaps leaving a trace of slightly acidic organic residue.
Controversy
Some have claimed that these artifacts provide evidence of ancient knowledge of electricity, millennia before the conventional dates given for its discovery. However even if it is accepted that the "Baghdad batteries" were in fact electrical devices, this provides no evidence of any real knowledge of electrical phenomena. For example, it is well known that the Ancient Greeks were aware of electrostatic electrical phenomena produced by amber, but they regarded it as a mere curiosity or toy and developed no electrical theory or functional devices. For evidence of ancient Parthian knowledge of the ideas of electricity, we would have to see some evidence of its use, see it discussed in their writings (though they may not have stated it as 'electricity', relating instead a mystical connotation), or see that their "batteries" were designed with a knowledge of electrical theory.
Comparisons
As electrical generators, the "Baghdad batteries" would be inefficient when compared to modern devices. The formulation of a similar electrochemical couple experiment by Luigi Galvani in the 1780s and, 20 years later, Alessandro Volta developed enough theory to convert Galvani's simple experiment into the efficient voltaic pile, producing current around 30 volts (but Volta's devices were much larger then the known Baghdad relics). Within two or three more years Sir Humphry Davy was using voltaic piles that produced 1,000 volts and enough current to run an arc lamp.
Egyptian use
Still more controversial is the suggestion that the existence of these artifacts indicates that the Ancient Egyptians could have used electric lighting in the construction of the Egyptian pyramids. There are descriptions of electrical devices on Egyptian walls (e.g., Dendera light, [1] (http://www.catchpenny.org/dendera.html), in the Hathor temple) and in ancient writings (see electricity). Also, some purport that modern calculations reveal the Great Pyramid of Giza impossible to construct in a reasonable time frame (see Great Pyramid of Giza: Labor and Moscow Papyrus) without the aid of a sort of ancient crane.
This suggestion has been met by many objections, including:
- the main pyramid-building era of Egypt was millennia before the earliest date speculated for the "Baghdad batteries" to have existed;
- even if these artifacts were used as galvanic cells, they are far too feeble to be used for lighting unless placed into an appropriate network array (the maximum power output achieved in the vinegar alone test of a single unit was about 25 mW, compared to about 1100 mW for a typical small penlight);
- other practical and plausible methods were possible, such as using copper mirrors to reflect sunlight into the work site.
Nevertheless a carved stone relief [2] (http://www.bib-arch.org/bswb_AO/bswbao0804ancient.html) from the first or second century found in the tomb of the Haterii family in Rome shows a crane being used to build a monument. Other devices discovered in Egyptian digs are alleged to be batteries as well (see Battery (electricity): History). And archaeological evidence reveals that town life in Karakorum, Mongolia, centered on metallurgy powered by the currents of the Orhon River, circa 1240.
See also
- Ark of the Covenant
- Anachronism and time travel
- Dendera light
- Electricity
- Galvanization
- Pseudohistory
External links, references, resources
- Battery, Baghdad, 250 BC (http://www.smith.edu/hsc/museum/ancient_inventions/battery2.html) : Museum of Ancient Inventions
- Baghdad Battery (http://www.unmuseum.org/bbattery.htm) : Unmuseum.org
- Zymet, Matthew, Electric Artifact (http://tlc.discovery.com/convergence/ark/articles/battery.html). The Learning Channel.
- Baghdad Battery (http://www.world-mysteries.com/sar_11.htm) : Strange Artifacts - World Mysteries
- Electricity in ancient times (http://www.ufo.se/ufofiles/english/issue_2/pretech2.html). WUFOC and NÄRKONTAKT.
Further reading and other references
- Dubpernell, G., "Evidence of the use of primitive batteries in antiquity". Selected Topics in the History of Electrochemistry, The Electrochemical Society, I-22 Princetn, NJ. 1978.
- Eggert, G., "The Enigma of the 'Battery of Baghdad". Proceedings 7th European Skeptics Conference. 1995.
- Eggert, G., "The enignamtic 'battery of Baghdad". Skeptical Inquirer, May-June 1996 V20 N3 PG31(4).
- MacKechnie, J. C. "An Early Electric cell?" Journal of the Institute of Electrical Engineers, 6:356-57. 1960.
- Paszthory E., "Electricity generation or Magic? The analysis of an unusual group of finds from Mesopotamia". MASCA Research Papers in Science and Tecnology 6:31-8. 1989.sv:Bagdadbatteriet