Oldest battery ~~~  The Baghdad Battery is believed to be about 2000 years old (from the Parthian period, roughly 250 BCE to CE 250). The jar was found in Khujut Rabu just outside Baghdad and is composed of a clay jar with a stopper made of asphalt. Sticking through the asphalt is an iron rod surrounded by a copper cylinder.,(reply>), Best guesses so far as to what the BB actually was are that someone accidentally put that combination of materials together and got a shock, maybe some sparks, and the deliberately built version was some kind of curiosity basically just like a joke buzzer or as something that went Zap in a sideshow. Without any knowledge of conductors, electromagnetism, etc, and nothing that could be usefully powered by the thing, it remained a curio and nothing more. Sort of like the spinning-ball steam engine invented in ancient Greece, or the iron trackways briefly used by the Romans.<br><br>There's a fun alternate-history tale to be told of how things might have progressed if the ancient arabs had figured some way of using the BB in a productive fashion, and/or the Greeks had figured out that power could be tapped off that turbine engine simply by wrapping a leather strap around it and a working axle, and/or the Romans had realised the much reduced friction of metal wheels on metal rails could be used for anything more than pushing boats over hills between rivers (...and that history is probably "The Mysterious CIties Of Gold", or maybe "Laputa: Castle in the Sky", come to think of it) ... but in reality, they were all dead end inventions that lacked the existence of other things that would have made them useful, or sufficient lateral thinking along the lines of "wait, we could probably use that to do &lt;XYZ&gt; if we put a bit of work into it".<br><br>It does make you think, though, much like the Basel Reaction Ferries: What have <i>we</i> missed, or what are we <i>currently</i> in the process of missing, in the same way? What possible futuristic inventions are we lacking, even though their core technology has already been invented but right now looks mostly like a useless toy, simply because of a lack of lateral thinking or of a suitable second piece of tech with which to join the dots?,(reply>), true, i was thinking of that too.  In fact i do believe the Ark is also an electrical device from the past...