Babbage's difference engine was made up of more than 25,000 individual levers, ratchets and cogs and weighed more than 13 tons.

Professor Robert Blick of the University of Wisconsin-Madison told the Beeb the nano version his team is trying to build uses the push and pull of micro parts to carry out calculations. They have apparently gone back to basics with the idea.

The US military is interested in a working device because unlike traditional chips, nano mechanical devices are not susceptible to electromagnetic pulses, which could be used by an enemy to knock out computing systems.

The first prototype parts are being built from gold and silicon and could be used in places such as car engines, where silicon can be too delicate, he said.

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